Clayton Quarry, Clayton, California · EVALUATION OF EAST PITSLOPE STABILITY AND FILL SLOPES....
Transcript of Clayton Quarry, Clayton, California · EVALUATION OF EAST PITSLOPE STABILITY AND FILL SLOPES....
EVALUATION OF EAST PITSLOPE STABILITY AND FILL SLOPES
Clayton Quarry, Clayton, California
Submitted To: Mr. Pete Cotter & Mr. Ron Wilson Cemex 5180 Golden Foothill Parkway, Suite 200 El Dorado Hills, CA 95762 Submitted By: Golder Associates Inc. 425 Lakeside Drive Sunnyvale, CA 94085 Distribution: Mr. Ron Wilson, Cemex Mr. Pete Cotter, Cemex Ms. Karen Spinardi Golder Associates, Sunnyvale, CA May 2015 Project No. 1520962
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Table of Contents
1.0 INTRODUCTION .............................................................................................................................. 1 1.1 Purpose ........................................................................................................................................ 1 1.2 Scope of Work .............................................................................................................................. 1 1.3 Method of Work ............................................................................................................................ 1 1.4 Available Data .............................................................................................................................. 2
2.0 SITE DESCRIPTION ........................................................................................................................ 3 2.1 Site Topography and Layout ........................................................................................................ 3 2.2 Climatic Conditions ...................................................................................................................... 3 2.3 Geologic Setting ........................................................................................................................... 3
2.3.1 Structural Conditions ................................................................................................................ 4 2.3.2 Groundwater Conditions .......................................................................................................... 4
2.4 Seismicity ..................................................................................................................................... 4 2.5 Quarry Development .................................................................................................................... 5
3.0 SITE RECONNAISSANCE AND SUBSURFACE EXPLORATIONS ............................................... 6 3.1 Site Reconnaissance ................................................................................................................... 6 3.2 Subsurface Explorations .............................................................................................................. 6
4.0 LABORATORY TESTING ................................................................................................................ 8 4.1 2015 Field Program ...................................................................................................................... 8
4.1.1 Point Load Tests ...................................................................................................................... 8 4.1.2 Soil Index Tests........................................................................................................................ 8
4.2 Previous Testing (Golder, 2015) .................................................................................................. 9 4.2.1 Point Load Tests ...................................................................................................................... 9 4.2.2 Soil Index Tests........................................................................................................................ 9 4.2.3 Compaction Test .................................................................................................................... 10 4.2.4 Consolidated Undrained Triaxial Shear Tests ....................................................................... 10
5.0 GEOTECHNICAL CHARACTERIZATION ..................................................................................... 12 5.1 Bedrock Units ............................................................................................................................. 12
5.1.1 Uniaxial Compressive Strength .............................................................................................. 12 5.1.2 Rock Structure ....................................................................................................................... 12
5.1.2.1 Major Structures ................................................................................................................. 13 5.1.2.2 Rock Fabric (Minor Structure) ............................................................................................ 13
5.1.3 Rock Mass Quality (GSI) ....................................................................................................... 14 5.1.4 Jar Slaking Test ..................................................................................................................... 15
5.2 Groundwater Conditions ............................................................................................................ 15 5.3 Controls on Quarry Slope Stability ............................................................................................. 16
5.3.1 Overall Slope .......................................................................................................................... 16 5.3.2 Benches ................................................................................................................................. 16
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5.3.3 Groundwater .......................................................................................................................... 17 5.3.4 Seismic Slope Stability ........................................................................................................... 17
5.4 Overburden Fill ........................................................................................................................... 17 6.0 ENGINEERING ANALYSES .......................................................................................................... 19
6.1 Overall Bedrock Slope ............................................................................................................... 19 6.1.1 Kinematic Analyses ................................................................................................................ 19 6.1.2 Limit Equilibrium Analyses ..................................................................................................... 19
6.1.2.1 Rock Mass Properties ........................................................................................................ 20 6.1.2.2 Seismic Loading ................................................................................................................. 21 6.1.2.3 Results of Analyses ............................................................................................................ 22
6.2 Limit Equilibrium Analysis of Overburden Fill Slopes................................................................. 23 6.2.1 Overburden and Foundation Strength Parameters ................................................................ 23 6.2.2 Results of Analyses ............................................................................................................... 23
7.0 CONCLUSIONS AND RECOMMENDATIONS.............................................................................. 26 7.1 Conclusions ................................................................................................................................ 26
7.1.1 East Quarry Slopes: ............................................................................................................... 26 7.1.2 Overburden Fill Slopes .......................................................................................................... 26
7.2 Recommendations ..................................................................................................................... 27 7.2.1 East Quarry Slopes ................................................................................................................ 27 7.2.2 Overburden Fill....................................................................................................................... 27
8.0 USE OF THIS REPORT................................................................................................................. 28 9.0 CLOSING ....................................................................................................................................... 29 10.0 REFERENCES ............................................................................................................................... 30
List of Tables Table 1 Proposed Bench Configurations Table 2 Results of Point Load Tests on Core Samples (B-1) Table 3 Results of Soil Index Tests Table 4 Uniaxial Compressive Strength from Point Load Tests (Golder 2015) Table 5 Results of Soil Index Tests on Backfill (Golder 2015) Table 6 Results of Compaction Test (ASTM D-1557 Method B) (Golder 2015) Table 7 Characteristic UCS by Rock Type Table 8 Description of Rock Fabric by Rock Type Table 9 Geologic Strength Index (GSI) by Rock Type Table 10 Rock Mass Properties Table 11 Results of Limit-Equilibrium Slope Stability Analyses for Overall Slope Table 12 Overburden and Foundation Strength Parameters Table 13 Results of Infinite Slope Analyses for Overburden Fills
List of Figures Figure 1 Project Location Figure 2 Site Layout
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Figure 3 Site Geology Figure 4 East Wall (March 2014) Figure 5 Definition of Bench Face Angle, Catch Bench, and Inter-ramp Slope Angle Figure 6 Geologic Strength Index (GSI) Figure 7 Results of Stability Analysis – Case 1 Figure 8 Results of Stability Analysis – Case 2 Figure 9 Results of Stability Analysis – Case 3 Figure 10 Results of Stability Analysis – Case 4 Figure 11 Results of Stability Analysis – Case 5 Figure 12 Results of Stability Analysis – Case 6 Figure 13 Results of Stability Analysis – Case 7
List of Appendices Appendix A Boring Logs for B-1, B-2, and B-3 Appendix B Results of Laboratory Tests Appendix C Results of Previous Laboratory Tests (Golder 2015)
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1.0 INTRODUCTION Golder Associates Inc. (Golder) is pleased to provide this evaluation of pitslope stability and overburden
fill stability for the Clayton Quarry operated by Cemex S.A.B. de C.V (Cemex) and located near Clayton,
California (Figure 1). This report presents the results of field and engineering studies and provides our
conclusions and recommendations regarding the stability of the proposed east quarry slope and the
placement of overburden fills outside the pit limits.
1.1 Purpose The purpose of this study was to assess the long-term overall pit slope stability for the east side of the
Clayton Quarry, and the stability of overburden fills placed outside the pit limits. The location of the
overburden fill has not been finalized, so the recommendations included in this report are general
recommendations to assist in the design of a repository for overburden. It is recommended that Golder
review final fill placement plans once a final location and configuration for the fill has been selected. It is
our understanding that our recommendations will be used by Cemex to develop a mine plan for the quarry
that will, in our opinion, meet Surface Mining and Reclamation Act of 1975 (SMARA) standards for pit
slope and overburden fill stability.
1.2 Scope of Work The Scope of Work for this study was defined in Golder’s proposal, “Proposal for Geotechnical Slope
Investigation, Clayton Quarry, Clayton, California,” Proposal Number P15-20962, dated January 27, 2015.
The scope of work included:
Pre-field Preparation and Records Review to obtain existing information about the site and select drilling locations
Exploratory Borings consisting of:
Two 30-foot deep Hollow Stem Auger (HSA) borings in the existing native slope below the ridge line on the east side of the quarry where overburden will likely be placed
One 100-foot deep corehole along the crest of the ridge defining the east wall of the quarry
Laboratory tests of soil and rock samples obtained from the borings and corehole
A slope stability analyses of overall pit slope of the east side of the quarry
Preparation of this report documenting the results of our investigation
1.3 Method of Work The work was initiated on February 17, 2015 with the start of the field drilling. The subsurface
explorations consisted of two HSA borings and one corehole were drilled by Gregg Drilling of Martinez,
CA under subcontract to Golder. Leah Feigelson, Staff Geologist, logged the soil and core samples
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obtained from the borings, collected soil and rock samples, and transported the samples to Golder’s
Sunnyvale office.
Soil samples from the borings were delivered to Cooper Testing Laboratory, Inc. in Palo Alto, California
for soil index tests. Samples of rock core were shipped to Golder’s Reno, Nevada office for point load
tests. After obtaining the results of laboratory testing, we proceeded with our engineering analyses and
preparation of this report.
1.4 Available Data Cemex and their civil engineering and environmental consultant, Spinardi Associates of Piedmont,
California, provided the following data for use in our studies:
Aerial photograph of the quarry dated April 18, 2012 (Figure 2)
Site topography based on 2012 aerial photography (Figure 2)
A mining plan and sections showing preliminary quarry slope configurations
Golder performed a previous study at the Clayton quarry. That study included geologic mapping,
collection of samples for laboratory testing, and laboratory testing, slope stability analyses, and
preparation of the report “Evaluation of Pitslope Stability and Rockfall Hazard for the Clayton Quarry,
Golder Associates, January 2015” (hereafter Golder, 2015). Our previous report focused on the stability of
the west wall of the quarry comprised predominantly of diabase and included an analysis of potential rock
fall hazards. We used portions of the data and results obtained from that study in the engineering
analyses presented in this report.
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2.0 SITE DESCRIPTION
2.1 Site Topography and Layout The Clayton Quarry is located approximately 3.5 miles north-northwest of Mount Diablo in central Contra
Costa County, California on the east side of Mount Zion (Figure 1). Mount Zion is approximately 1585 feet
high, with natural slope inclinations of approximately 20 to 35 degrees to the southeast in the area of the
quarry. The area in the vicinity of the quarry is drained by Mitchell Creek, an intermittent stream trending
to the north-northeast, and draining the northwest-slopes of Mount Diablo and the east side of Mount
Zion. The elevation of Mitchell Creek, located about 1800 to 2000 feet east of the quarry, ranges from
approximately 550 to 675 feet.
2.2 Climatic Conditions The climate in the area of the quarry can be characterized by mild, moist winters and hot dry summers.
Data from the Western Regional Climate Center (2014) indicates that mean daily temperatures range
from approximately 40 to 50 degrees Fahrenheit (F) during the winter to 70 to 80 degrees F during the
summer months. Frost can occur during winter months and temperatures as high as 100 to 110 degrees
F can occur during the summer. The mean annual precipitation is approximately 20 inches, and almost all
precipitation falls in the winter. Pampeyan (1963) reports that light snow can occur during the winter on
the mountains to an elevation of about 1000 feet.
2.3 Geologic Setting A detailed description of the geologic setting, lithology, geologic structure, groundwater conditions, and
seismicity of the site are provided by Golder (2015). This report contains a brief summary of these topics
to the extent necessary for the understanding of our engineering analyses and recommendations. A
geologic map showing the location of the quarry is shown in Figure 3.
Cemex excavates rock from diabase dikes from a sheeted dike complex (part of the Mt. Diablo Ophiolite
Complex) which it then crushes and screens to produce construction aggregate. The sheeted dike
complex is bounded to the west and east by the Jurassic Knoxville Formation (part of the Great Valley
Sequence). The Knoxville Formation consists of micaceous shale with intermittent lenses of limestone
and sandstone beds (Pampeyan, 1963). The Great Valley deposits were thought to on-lap the rocks of
the Mt. Diablo Ophiolite complex in this area as a depositional contact, however, the contact may also
have experienced uplift and faulting over geologic time, but the contact is not considered a Holocene-
active fault.
The contact between the Knoxville Formation and the diabase dikes is characterized by altered rock-like
materials derived from both the Knoxville Formation and the diabase. Based on our 2014 site
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reconnaissance and mapping (Golder, 2015), it typically consists of a dense, highly fractured dark green
to black aphanitic rock containing slickensides on fracture surfaces.
Quaternary Alluvium occurs in the valley that contains Mitchell Creek east of the quarry (Dibblee, 2006).
In the immediate vicinity of Mitchell Creek this alluvium consists of alluvial gravel, sand and clay.
2.3.1 Structural Conditions The diabase sheeted dike complex mined at Clayton Quarry is within the Mt. Diablo antiform, in the upper
plate of the Coast Range Thrust. The orientations of the dikes have an average dip direction of 310° and
dip of 38°. These orientations are persistent over long distances because similar dike orientations are
reported for the Kaiser Quarry on the west side of Mt. Zion (Figure 3). Pampeyan (1963) writes that joints
in the diabase appear to be randomly oriented and this was confirmed by joint orientation measurements
in the quarry (Golder, 2015). Williams (1984) indicates the contact on the east side of the quarry between
the Knoxville Formation and the sheeted dike complex to be a fault that dips east at about 60 degrees.
Site specific drilling data evaluated by P. Cotter of Cemex (Pers. Comm. 2015) indicate that the contact
dips at approximately 61 degrees in the east wall of the Quarry. Geologic maps by Dibblee (1980) and
Williams (1984) indicate that the dip of the Knoxville Formation strata ranges from moderate (30 to 60
degrees) dips to the east to near vertical.
2.3.2 Groundwater Conditions The Clayton Quarry does not intersect a geologic unit that contains enough groundwater to be considered
a significant aquifer. Water that occurs in the Diabase exposed in the quarry appears likely consists of
surface infiltration that has percolated into discontinuities within the rock mass (i.e., seeps along fractures)
which then daylights in the quarry pitslopes. The current base of the quarry (~ el. 580 amsl) contains a
small pit lake formed from the seepage; however, the generally dry conditions and high rates of
evaporation minimize the accumulation of water in the pit lake.
2.4 Seismicity The Clayton Quarry is located in a seismically active area of California. The following seismic design
parameters were selected based on a probabilistic disaggregation of USGS seismicity data for the site
(Golder, 2015):
Peak Ground Acceleration (PGA) of 0.51g (475 year return period)
Modal design earthquake magnitude (M) of 6.57
Modal distance (r) to the causative fault is 10.2 kilometers
These values of PGA, M, and r were used to estimate the seismic coefficient for use in pseudo-static
slope stability analyses.
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2.5 Quarry Development The quarry is approximately 2850 feet long in a north-south direction and 1800 feet wide (Figure 2). As of
April 2012 the elevation of the bottom of the quarry was at an elevation of about 580 feet. The east wall of
the quarry is still being developed, and the crest of the east quarry wall ranges in elevation from
approximately 900 feet to 750 feet. Large portions of the west wall of the quarry are final slopes. As of
April 2012, the overall slope of the east quarry wall was about 20 to 25 degrees (approximately 2.7H:1V
to 2.2H:1V). An aerial photograph of the quarry with an overlay of the topography is shown in Figure 2. A
photograph of the existing east quarry wall is shown in Figure 4.
The diabase is blasted in order to loosen it so it may be excavated with loaders and placed into trucks so
it can be hauled to the plant for processing into construction aggregate. Mined soil and rock that cannot
be processed into construction aggregate (overburden) has been placed along the ridge between the
quarry and Mitchell Creek. We understand that portions of this overburden will likely be removed as part
of mining of the east wall of the quarry and ultimately reclamation.
The Proposed Mining and Reclamation Plans (Spinardi Associates 2015) indicate the bottom of the
quarry will be excavated to an elevation of approximately. 300 amsl. The east quarry slope will be
designed so as to not significantly lower the existing ridgeline below the original ground surface between
the quarry and Mitchell Creek. Cemex proposes to develop the east side of the quarry using the bench
configurations listed in Table 1.
Table 1: Proposed Bench Configurations
Rock Type Bench Face Slope
Bench Height
Catch Bench Width
Design Inter-Ramp Slope
Knoxville Formation (sandstone,
siltstone, claystone)
1H:1V (45 degrees) 60 feet 30 feet 1.5H;1V
(33.7 degrees)
Knoxville/Diabase Contact
(Transition)
Vertical (90 degrees) 60 feet 60 feet 1H:1V
(45 degrees)
Diabase Vertical (90 degrees) 60 feet 30 feet 0.5H:1V
(63.4 degrees) Note: See Figure 5 for definitions of Bench Face Angle, Catch Bench and Inter-ramp Slope
After mining has been completed, the pit will be allowed to fill with water to an approximate elevation of
735 feet to form a pit lake.
An overburden fill (the Permanent Overburden Fill Area) will be constructed outside the limits of the
quarry. The final location has not been selected but areas south and east of the existing quarry are being
evaluated (i.e., the native slope between the quarry and Mitchell Creek).
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3.0 SITE RECONNAISSANCE AND SUBSURFACE EXPLORATIONS Golder performed a site reconnaissance in March 2014 (Golder, 2015) and again in February 2015 during
the drilling program. We used site reconnaissance data to supplement that data collected from the three
borings performed as part of this study.
3.1 Site Reconnaissance During the site visit in March 2014 and the recent drilling campaign in February 2015, no tension cracks
or features indicating instability of overall slope on the east side of the pit were observed. Review of aerial
photographs (Figure 2) and visual observation of slopes (Figure 4) does not indicate the presence of
tension cracks or other features that would indicate that from a global perspective (i.e., crest to toe) the
existing east quarry slope is unstable.
3.2 Subsurface Explorations The subsurface explorations consisted of one corehole (B-1) and two hollow stem auger (HSA) borings
(B-2 and B-3) at the locations shown in Figure 2. Corehole B-1 was drilled to obtain information about the
rock conditions below the overburden located at the top ridgeline between Mitchell Creek and the quarry.
Boring B-2 and Boring B-3 were drilled approximately 700 feet southeast of the east ridge of the quarry in
native ground to obtain information about foundation conditions for the potential overburden fill.
Both the corehole and the HSA Borings were drilled using a truck mounted Mobile B-53 drill rig. Upon
completion of the drilling, each boring was grouted with a mixture consisting of water, cement, and
bentonite. Drilling operations were observed by Leah Feigelson of Golder, and she also logged the
borings and collected soil and rock samples from the corehole and each of the borings.
The corehole (B-1) was advanced by mud rotary methods equipped with a five-foot long, HQ core barrel.
The core barrels was advanced with a series of maximum 5-foot long runs and the core barrel was then
extracted from the corehole, unscrewed from the drill rods and emptied into cardboard core boxes.
Drillers marked the ends of the core run with the drill footage marked on wooden boxes
The corehole log for B-1 is presented in Appendix A along with a description of Golder’s rock core logging
procedure and Bieniawski’s Rock Mass Rating (RMR76) system. Information recorded for the core
included Total Core Recovery (TCR), Rock Quality Designation (RQD), fracture frequency (calculated as
the natural fracture count divided by the core run length), field estimate of the Uniaxial Compressive
Strength (UCS), and degree of weathering. Information collected on individual natural fractures in the core
consisted of the fracture type (bedding plane, joint, etc.) shape, roughness, infill type and thickness, angle
to core axis, joint roughness coefficient (JRC) and Joint Condition Rating (JCR). The JRC is a measure of
fracture roughness (Barton and Chouby, 1977), and the JCR is description of the mechanical properties
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of the fracture and is used in making estimate of Bieniawski’s (Bieniawski, 1976) Rock Mass Rating
(RMR).
Borings B-2 and B-3 were drilled use HSA drilling methods. Both boring were advanced to 31.5 feet below
the existing ground surface (bgs). Driven samples were retrieved from the borings at 5-foot intervals using
a Modified California (MC) steel tube-lined split spoon sampler (3 inch O.D. and 2½ inch I.D.) at depths of
5, 15 and 25 feet below ground surface (bgs) in both holes; and a Standard Penetration Test (SPT) split
spoon sampler (2 inch O.D. and 1⅜ inch I.D.) was used to obtain samples at depths of 10, 20 and 30 feet
(bgs). The samplers were driven 18 inches (unless otherwise noted) into the bottom of the boring using a
140-pound automatic hammer with a 30-inch drop. Hammer blows were recorded in 6-inch intervals for
each sample and are presented on the borings logs. The penetration resistance (N-value) of the soil is
calculated as the sum of the number of hammer blows required to drive the sampler the final 12 inches.
The N-value is an indication of the apparent density of cohesionless soils and the consistency of cohesive
soils. Generally, if a total of 50 blows were recorded for a single 6-inch interval, the test was terminated
and the blow count was recorded as 50 blows for the inches of penetration observed. All blow counts
presented on the boring logs are uncorrected values and do not take into consideration the efficiency of
the automatic hammer, overburden, or other influences.
HSA Boring logs for B-2 and B-3 are presented in Appendix A. The soils were classified according to the
Unified Soil Classification System (USCS) (ASTM D2488). Soil samples collected from the borings were
stored in plastic bags and sealed to minimize moisture loss, then transported to Golder’s Sunnyvale,
California office upon completion of the field investigation.
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4.0 LABORATORY TESTING Laboratory testing was performed on the samples of soil and rock obtained from the HSA borings and the
corehole. Results of these tests performed as part of this study area are included in Appendix B. The
testing performed as part of our previous studies (Golder, 2015) were also utilized in this study, and are
detailed in Section 4.2.
4.1 2015 Field Program
4.1.1 Point Load Tests The Point Load Strength Index was measured by performing point load tests (ASTM, 2006) on two
samples of siltstone (Knoxville Formation) from the corehole to verify UCS values assigned to rock units
in the field. The Point Load Strength Index is correlated to the uniaxial compressive strength (UCS) of
intact rock by multiplying the Point Load Strength Index by a factor, N. For this project, N was assumed to
equal 24. Test results are summarized in Table 2.
Table 2: Results of Point Load Tests on Core Samples (B-1)
Depth (feet) Rock Type Point Load Strength (psi)
Estimated Uniaxial Compressive Strength
(psi) 45.8 siltstone 61 1474
65.9 siltstone 326 7817
4.1.2 Soil Index Tests Soil index tests (particle size distribution and Atterberg Limits) were performed by Cooper Laboratories, of
Palo Alto, California on samples of soil obtained from the corehole (B-1) and the HSA borings (B-2 and B-
3). Results of these tests are summarized in Table 3.
Table 3: Results of Soil Index Tests
Boring Depth (feet)
Water Content (percent)
Dry Density3,4
(pcf)
Atterberg Limits2
USCS1 Material Description LL PL PI
B-1 91.4-92 10.6 NR 25 18 7 SC-SM Very Dark Gray Silty, Clayey SAND
B-2 5.5-6 13.0 119.9 36 18 18 SC Dark Yellowish Brown Lean Clayey SAND w/Gravel
B-2 10-11.5 15.9 NR 41 20 21 CL Dark Yellowish Brown Sandy Lean CLAY
B-3 5.5-6 31.4 106.0 51 22 29 CH Dark Yellowish Brown
Sandy Fat CLAY/Fat Clayey SAND w/Gravel
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B-3 10.5-11.5 18.5 123.9 39 24 15 CL Lean Clayey Gravel with Sand
Notes: 1. USCS = Unified Soil Classification System, USCS of fines based on Atterberg Limits and Material Description 2. LL= Liquid Limit, PL=Plastic Limit, PI = Plasticity Index
3. NR = Not Reported 4. Assumed Gs = 2.7 for determination of Dry Density
4.2 Previous Testing (Golder, 2015) In March 2013, samples of rock and backfill were collected by Golder personnel during a site visit to
Clayton Quarry. Backfill samples were analyzed by Cooper Testing Laboratory, Inc. in Palo Alto,
California for soil index, compaction, and triaxial shear strength tests. Rock samples were subjected to
Point Load Index Testing by Golder personnel. Material properties were estimated from the test results
and used in the engineering analyses presented in this report.
The samples were obtained from the existing fill placed on the ridge on the east side of the quarry and in
the general vicinity of corehole B-1. Results of this previous laboratory testing are in Appendix C.
4.2.1 Point Load Tests The Point Load Strength Index was measured by performing point load tests (ASTM, 2006) on samples of
diabase, siltstone (Knoxville Formation) and rock-like material from the contact between these two units.
The Point Load Strength Index is correlated to the uniaxial compressive strength (UCS) of intact rock. The
UCS was estimated for each rock type tested by multiplying the Point Load Strength Index by a factor, N.
For this project, N was assumed to equal 24, a value that is appropriate for many rock types. Test results
are summarized in Table 4.
Table 4: Uniaxial Compressive Strength from Point Load Tests (Golder 2015)
Rock Type Number of Tests
Estimated Unconfined Compressive Strength (psi)
Minimum Average1,2 Maximum Standard Deviation
Weathered Diabase 3 2300 5230 5580 N/A
Slightly Weathered to Fresh Diabase 25 1661 18270 39400 10330
Siltstone (Knoxville Fm.) 8 3310 5330 7340 1540
Diabase / Knoxville Contact 23 3165 7400 11870 2720
Notes: 1. The two highest and lowest test results are deleted from the data set for sample sizes greater than 10. 2. The highest and lowest test results are deleted from data set for sample sizes less than 10.
4.2.2 Soil Index Tests Soil index tests (particle size distribution and Atterberg Limits) were performed on two samples of backfill
material obtained during the site visit. One sample was obtained from the base of the overburden pile
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located near the southern rim of the quarry pit (Golder 2015) and may contain a larger portion of near
surface weathered rocks from the Knoxville Formation than typical backfill. The second sample consisted
of material obtained approximately 200 feet east near the crest ridgeline (Golder 2015). These samples
are considered more representative of typical overburden material and were combined for testing. The
results of these tests are summarized in Table 5.
Table 5: Results of Soil Index Tests on Backfill (Golder 2015)
Sample Type Depth Atterberg Limits USCS
Symbol Soil Description LL PL PI
x19 Bucket Surface 38 26 12 SC Lean Clayey Sand with Gravel
x20 and x21 Bucket Surface 26 17 9 GC Lean Clayey Gravel with Sand Notes: USCS = Unified Soil Classification System LL= Liquid Limit, PL=Plastic Limit, PI = Plasticity Index These test results indicate that the backfill consists of Lean Clayey Sand with Gravel (SC) and Lean
Clayey Gravel with Sand (GC). The fines fraction classify as clay of low plasticity.
4.2.3 Compaction Test The relationship between moisture content and the dry unit weight of compacted backfill was obtained by
performing a Modified Proctor Compaction Test (ASTM D-1557 Standard Method for Laboratory
Compaction of Soil Using Modified Effort) on the sample collected from locations x20 and x21. Since the
purpose of this test was to provide information for selecting unit weights for the triaxial shear test
specimens, only the material passing the ½-inch sieve was utilized in the compaction test. The results of
the compaction tests are shown in Table 6:
Table 6: Results of Compaction Test (ASTM D-1557 Method B) (Golder 2015)
Test Results Maximum Dry Density
(pcf) Optimum Water Content
(percent)
Uncorrected 140.7 8.5 Corrected for Oversize 142.2 8.1 Notes: pcf = pounds per cubic foot
4.2.4 Consolidated Undrained Triaxial Shear Tests Consolidated, undrained triaxial tests with pore pressure measurements (CU/pp) were performed on
samples of backfill to provide shear strength properties. Similar to the compaction test, only material
passing the ½-inch sieve was used to prepare test specimens. The three triaxial shear test specimens
each had an approximate dry density of 121 pounds per cubic foot (pcf) and moisture content of
approximately six percent. This density is approximately 85 percent of the maximum dry density of the soil
obtained in the compaction test, and approximates the density of the backfill when placed with little or no
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compaction. The results of the tests indicate that the effective friction angle of the backfill is approximately
39 degrees with zero cohesion.
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5.0 GEOTECHNICAL CHARACTERIZATION For this study, we defined soil and rock mass units, termed geotechnical units, based on their physical
and structural characteristics. Geotechnical units can be comprised of individual geologic units, or
combinations of geologic units that can be grouped together because they have similar engineering
properties. Alternatively, geotechnical units may be subdivisions of geologic units if mechanical and
structural characteristics within the units are different. The available published data, data we collected
during our site reconnaissance, and the laboratory testing results were used to define geotechnical units.
5.1 Bedrock Units The quarry rock mass on the east side of the quarry was divided into three geotechnical units, Knoxville
Formation (siltstone, sandstone, and claystone), Knoxville/Diabase contact material (Transition), and
Diabase.
5.1.1 Uniaxial Compressive Strength The UCS of the intact rock is required to estimate the rock mass shear strength properties. We estimate
the UCS for the Knoxville/Diabase contact material and Diabase from point load tests on hand specimens
performed as part of our previous study (Table 4).
The point load tests performed on core and hand specimens of Knoxville Formation may overestimate the
intact rock strength of this unit since suitable samples for point load testing can be difficult to obtain in
highly altered and weathered rock units; therefore, we assigned the UCS of the Knoxville Formation
based on weighted average of the field estimate of the UCS of intact rock made during core logging
(approximately 3000 psi) and shown in the log for the corehole (B-1) in Appendix B. We assigned
characteristic UCS values to the various rock types for use in our engineering analyses as shown in Table
7.
Table 7: Characteristic UCS by Rock Type
Rock Type Average Uniaxial Compressive Strength (psi)
Slightly Weathered to Fresh Diabase 18300
Knoxville/Diabase Contact 7400
Siltstone (Knoxville Fm.) 3000
5.1.2 Rock Structure Geologic structures pertinent to quarry wall slope stability studies are divided into major and minor
structures (rock fabric).
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Major structures consist of persistent individual geologic structures such as contacts between rock types,
faults, and other structures that extend over many benches or the entire quarry wall. Typically, these
structures can be mapped and shown as individual structures on large-scale geologic maps or quarry
geology maps. For slope stability studies, the effect of each major structure is assessed individually by
considering its location and orientation in the pit slope and evaluating if the major structures individually or
in combination intersect the pit slopes in a manner that may result in slope instability.
Rock fabric consists of those small-scale geologic structures such as joints, bedding planes, and small-
scale faults that form discontinuities that pervade the rock mass and are so numerous and with such
limited persistence that they cannot be shown on maps as individual structures. Their effect on slope
stability is assessed by considering their average orientation, persistence (trace length of the structure in
rock exposures), and spacing, and assuming that similarly oriented structures will be found throughout the
geotechnical unit.
5.1.2.1 Major Structures There are no other major structures of note in the quarry other than the east-dipping contact (shown as a
fault contact on Williams’ map [1984]) between the Knoxville Formation and the Diabase.
5.1.2.2 Rock Fabric (Minor Structure) During our site visit in 2014 (Golder, 2015) we observed and collected rock discontinuity data on the east
quarry slope from benches excavated in the Diabase and Knoxville/Diabase contact. A description of the
rock fabric of the Knoxville Formation was based on the discontinuity descriptions contained in the core
log provided in Appendix A. The descriptions of rock fabric are provided in Table 8.
Table 8: Description of Rock Fabric by Rock Type
Rock Type Discontinuity Set Description
Knoxville Formation
Primary
Type: Bedding Planes Orientation: Dip is vertical to 40 degrees east Persistence: High (> 30 feet) to Continuous Spacing: Very Close (< 6 inches) Surface Condition: Planar, Smooth
Secondary
Type: Joints Orientation: Orthogonal to Bedding Planes Persistence: Very Low (< 3 feet) Spacing: Close (< 6 inches) Surface Condition: Planar, Smooth
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Knoxville/Diabase Contact
Primary
Type: Joints and Shears Orientation: Random Persistence: Very Low to Low (< 3 feet to 10 feet) Spacing: Very Close (< 6 inches) Surface Condition: very irregular to undulating, smooth to slickensided surfaces with non-softening infillings. Note: Contact material consists of a sheared irregular mass of moderately strong angular rock blocks.
Secondary None
Diabase
Primary
Type: Dike Contacts Orientation: Dip is 40 to 60 degrees to northwest Persistence: High to Very High (10 to > 60 feet) Spacing: Wide to Very Wide (6 inches to < 6 feet) Surface Condition: Planar to Undulating, tight, rough, no to non-softening clay and silt infilling
Secondary
Type: Joints/Shears Orientation: Random Persistence: Low to Medium (< 3 to 10 feet) Spacing: Close to Wide (few inches to 3 feet) Surface Condition: smooth to rough, undulating to planar
5.1.3 Rock Mass Quality (GSI) Rock mass quality is an indication of the condition of the rock that accounts for the intact strength of the
rock, and the persistence, spacing, and condition of the natural fractures in the rock mass. It is used to
estimate rock mass shear strength properties used in slope stability analyses. For this project and the
previous study (Golder, 2015), we estimated the rock mass quality by estimating the Geologic Strength
Index (GSI) according to the guidelines provided by Hoek et al. (1992) and shown in Figure 6.
The Diabase consists of a Very Blocky to Blocky rock mass. The individual rock blocks are interlocked
and formed by three or more intersecting discontinuities that are pervasive throughout the rock mass.
The rock mass is typically fresh to slightly weathered with rough discontinuities, so the discontinuity
surface condition is classified as Very Good to Good.
The Knoxville/Diabase contact material consists of a highly fractured rock mass with angular individual
rock blocks formed by sheared contacts and numerous randomly oriented joints. Based on Figure 6, it
would be classified as a Blocky/Disturbed/Seamy rock mass with Poor to Very Poor conditions for
discontinuities.
Since there are no fresh outcrops of the Knoxville Formation in the Clayton Quarry, we estimated the rock
mass quality based on the Rock Mass Rating (RMR76) for the corehole (boring B-1). The weighted
average of the RMR76 assigned to each core run is 30 based on the log for B-1 provided in Appendix A.
Hoek, et al. (1993), indicates that GSI = RMR76 when RMR76 > 18. Since the value of RMR76 might be
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influenced by core intervals with high RMR, and we only had a short (50 foot interval of core) in the
Knoxville Formation, we conservatively estimated that the GSI = RMR76 = 20 for estimating rock mass
shear strength properties.
We assigned values of GSI to the rock mass as shown in Table 9.
Table 9: Geologic Strength Index (GSI) by Rock Type
Rock Type Structure Discontinuity
Surface Conditions
Geologic Strength Index (GSI)
Diabase Very Blocky Very Good to Good 55
Diabase/Knoxville Contact Blocky/Disturbed/Seamy Poor to Very Poor 20
Knoxville Formation Blocky/Disturbed/Seamy Poor to Very Poor 20
5.1.4 Jar Slaking Test Golder performed two jar slake index tests on samples of Knoxville siltstone. The test was performed in
general accordance with the Jar Slake Test method by Caltrans (2007). The two samples were placed in
a water filled jar and observed continuously for the first 10 minutes, at 30 minutes, and then a final
observation after 24 hours. There were no signs of slaking observed during the duration of the test. The
samples stayed intact and did not appear to develop any fractures or break. Both Knoxville samples were
given a jar slake index value (Ij) of 6; the highest value possible, describing, “no change to condition of the
rock fragment” (Caltrans, 2007).
5.2 Groundwater Conditions The Clayton Quarry does not appear to intersect a geologic unit that is likely to be a significant aquifer.
Water that occurs in the Diabase exposed in the quarry appears to consist of water that is contained in
discontinuities within the rock mass (i.e., seeps along fractures).
The quarry is unlikely to encounter significant groundwater or intersect a regional aquifer during mining. In
our opinion, it is unlikely that Mitchell Creek will contribute to groundwater flows into the quarry because:
The relative elevations and distance between the quarry and the creek are significant
The quarry is in a different geologic unit than that under Mitchell Creek
No known faults and structures appear to form a hydraulic connection between the creek and the quarry
Based on information provided by Cemex, and for the purposes of our slope stability analyses presented
in this report, it was assumed the gradient and position of the future water table in the pit walls (post
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reclamation) would be defined by the elevation of the pit lake (735 feet) which will be controlled by the
elevation of the outlet from the quarry at its north end.
5.3 Controls on Quarry Slope Stability
5.3.1 Overall Slope The stability of the overall slope (quarry slope crest to toe) in rock masses can be controlled by the
persistence and orientation of large-scale geologic structures (geologic contacts and faults), and also
persistent bedding planes in sedimentary rocks. Structurally-controlled failures are evaluated by
performing a kinematic analysis that takes into consideration the orientations of the slope and controlling
structures. Overall slope stability is also controlled by the shear strength of the rock mass. While shear
through the rock mass is unlikely in strong, brittle rocks such as the Diabase, slopes composed of highly
fractured rock like the Knoxville are more liable to become unstable due to shear through the rock mass.
The level of stability of a rock slope can be quantified by performing a limiting equilibrium slope stability
analyses.
5.3.2 Benches Benches are left in quarry slopes as a rockfall control measure. Catch benches (Figure 5) will be left in
the slope to retain rockfall and small bench-scale failures. Leaving benches in the slope does not improve
or decrease overall global slope stability.
The steepness of bench faces excavated in rock is controlled by both the mining method and the
persistence and orientation of geologic structures that might form plane shear and wedge type bench-
scale failures. In strong, brittle rock such as the Diabase, near vertical bench faces have been formed in
the quarry by pre-splitting, a controlled blasting method. Where dike contacts dip out of the bench face,
bench-scale plane shear failures may form and a few of these have formed in the existing east wall of the
quarry. The size of these plane shear failures is limited by the persistence of the dike contacts, typically
less than 30 feet in length. Where they have occurred, they have been removed during mining and bench
scaling operations.
There are few benches in the Diabase/Knoxville contact material in the existing quarry, but as indicated in
Table 8, discontinuity orientations vulnerable to bench-scale plane shear and/or wedge failures do not
appear to be present. Bedding planes in the Knoxville Formation dip either near vertical or to the east –
orientations favorable for bench slope stability in the east wall of the quarry.
The steepness of bench faces in the highly fractured Knoxville Formation and the Diabase/Knoxville
contact is likely to depend on mining method, and may vary locally depending on the degree of fracturing
of the rock mass. The bench faces in the Knoxville Formation may be formed by mechanical excavation
such as ripping and trimming with a dozer or digging with an excavator.
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5.3.3 Groundwater Groundwater would not appear to be a control on overall slope stability of the ridge on the east side of the
quarry as the ground surface is sloped to promote runoff and the recharge area is small, so infiltration of
surface water into fractures in the rock mass is not likely to be a source of significant groundwater in final
quarry slopes. Therefore, the rock mass can be assumed to be “dry” for the purposes of the slope stability
analyses. As previously discussed, we have conservatively assumed that the future position of the water
table would be defined by the elevation of a pit lake in the quarry at a final elevation of 735 feet.
5.3.4 Seismic Slope Stability Clayton quarry is located in a seismically active area of California. Keefer (1984) summarized the
geologic environments likely to produce earthquake-induced landslides and his findings were included in
California Geological Survey, Special Publication 117 (2008). Keefer’s study was based on analysis of 40
earthquakes and found that different types of landslides occur with different frequencies.
Keefer (1984) indicates large, deep-seated rock slumps, rock block slides, and rock avalanches are less
common. Large rock block slides require a conspicuous, persistent plane of weakness such as a bedding
plane, fault, or geologic contact dipping out of the slope. Such large-scale structures do not appear to be
present in the east slope of the Clayton Quarry. Rock slides triggered by earthquakes occur most
frequently in slopes composed of weakly cemented, intensely fractured, or weathered rock containing
conspicuous planes of weakness when the slopes are steeper than 35 degrees. Rock avalanches
typically occur in high (typically greater than 500 feet) slopes steeper than 25 degrees composed of
intensely fractured rock with either planes of weakness dipping out of the slope or weak cementation or
signs of previous sliding.
While portions of the east quarry slope will be composed of highly fractured rock, the quarry slope is not
particularly steep or high nor will it contain planes of weakness dipping out of the slope and so do not
correspond to the conditions Keefer indicates are likely to produce large-scale, earthquake-induced
landslides. As part of our engineering analyses we performed limiting equilibrium analyses using the
pseudo-static method to assess the level of stability under seismic loading conditions.
Keefer (1984) noted that small rock falls (falls of boulders or small disrupted masses of rock) and rock
slides (masses of rock fragments that slide on discontinuities dipping out of the rock) are relatively
common. At the Clayton Quarry, small rock falls from bench faces and slides of rock blocks, if they occur
during an earthquake would likely be retained on catch benches left in the slope.
5.4 Overburden Fill Based on laboratory testing performed as part of previous studies (Golder, 2015), the overburden material
consists of clayey gravel to clayey sand that the triaxial shear tests indicate will behave as a cohesionless
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material when it is not compacted (Appendix B). While this material contains about 15 percent fines,
based on our experience it will likely drain and not build up high pore pressures when placed in the
permanent overburden fill area with minimal compaction.
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6.0 ENGINEERING ANALYSES We performed a screening level kinematic analyses to evaluate the potential for overall slope instability to
develop due to a large geologic structure intersecting the east quarry slope. Limiting equilibrium analyses
were used to evaluate the stability of the proposed west facing quarry slope and the overburden fill
slopes.
6.1 Overall Bedrock Slope
6.1.1 Kinematic Analyses The stability of slopes in competent rock can be controlled by structures, or combinations of structures
that define kinematically admissible failure modes. A failure formed by discontinuities in the rock mass
results when the shear strength of the discontinuities is sufficiently low to allow sliding of an intact rock
block along one or more discontinuities, typically in planar, wedge, or a combination of these modes.
Each of these modes is described as follows:
Planar failure can occur where individual discontinuities dip towards the slope face and daylight such that the overlying rock block can displace.
Wedge failures can occur where two planar structures intersect to form a rock wedge and the line of intersection between the two structures dips toward and daylights in the slope.
Toppling failures can occur where there are persistent, closely spaced discontinuities that dip at a high angle into the slope so as to form slabs and blocks of rock that can overturn or topple from the slope. Toppling may occur from steep bench faces, but typically does not form a failure mechanism for an overall slope.
The only major structure on the east side of the quarry with sufficient persistence to impact overall quarry
slope stability is the contact between the diabase and the Knoxville Formation. This contact dips to the
east into the overall slope of the quarry at about 60 degrees, and thus does not form a kinematically
admissible failure. That is, the contact is not in an orientation that would allow sliding to occur. Similarly
the existing geologic data appears to indicate that the bedding planes in the Knoxville Formation are
either near vertical or dip into the quarry slope and are likewise not in an orientation upon which sliding
can occur.
6.1.2 Limit Equilibrium Analyses The weight of the soil and rock in pit slopes creates shear stresses within slopes. Pore pressures in the
slope from groundwater (if present) reduce the available effective shear strength of the rock mass. If the
shear stresses are greater than the available effective shear strength over large zones within the slope,
the pit slope will become unstable. Such failure mechanisms are evaluated by performing limiting
equilibrium analyses along surfaces that pass through the rock mass and mobilize the rock mass shear
strength.
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For this study, the level of stability of the high bedrock slopes was quantified by performing limiting
equilibrium slope stability analyses using Spencer’s Method of Slices (Spencer, 1967) as implemented in
the computer program Slide 6.0 (Rocscience, 2010). Spencer’s method is an “accurate” method that
satisfies both horizontal and vertical force and moment equilibrium. It provides calculated factors-of-
safety (FOS) that are comparable to values calculated by other “accurate” methods. Algorithms
programmed within Slide generate trial slope surfaces and identify the surface with the lowest FOS
(critical surface). This minimum FOS of all of the trial surfaces provides an indication of the level of
stability of the slope. For static loading, the minimum acceptable factor of safety is typically between 1.2
and 1.3 for slopes with a low consequence of failure (Duncan and Wright, 2004; Read and Stacey, 2009).
6.1.2.1 Rock Mass Properties The practical limitations for shear strength testing of the rock mass in the laboratory (samples are too
small to be representative) requires that empirical methods be used to estimate rock mass shear strength
such as occurs on the east side of the Clayton Quarry. For this study, as in the previous study (Golder,
2015), we estimated the rock mass shear strength based on an empirical method initially developed by
Hoek and Brown (1980) and subsequently modified (Hoek. et al., 2002). This is the most widely used
method of estimating rock mass shear strength for rock slope stability.
The Hoek-Brown failure criteria defines the strength of a rock mass as a function of the parameters: mb,
s, and a. These are in turn defined by the following properties:
Uniaxial Compressive Strength (UCS) of the intact rock (Table 7)
Geologic Strength Index (GSI) of the rock mass (Table 9)
A material constant, mi, of the intact rock
A disturbance factor, D, that accounts for loosening of the rock mass due to blast damage or stress relief
Values of mi were selected based on typical values (Hoek and Karzulovic, 2000). For the Knoxville
Formation, we assumed a, an average value for sedimentary rocks consisting of sandstone, siltstone and
claystone. We also used a mi of 7 for the Knoxville/Diabase contact as it appears to consist of fine-
grained material likely derived from the Knoxville Formation.
The disturbance factor, D, was selected based on guidelines developed by Hoek (2012). D can range
from 0 to 1.0 with lower values indicating lesser degrees of disturbance due to stress relief and blast
damage. A disturbance factor, D, of 0 was selected for use in our analysis for the portion of the rock mass
located deep in the slope as Hoek indicates blast damage typically does not occur more than a bench
height into the slope and may be less where controlled blasting methods and mechanical excavation are
used to form bench faces.
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A summary of the values of UCS, RMR76, mi, and D used in the Hoek-Brown Failure Criterion formulas to
obtain the Hoek-Brown rock mass shear strength parameters, mb, s, and a, used in our analyses is
provided in Table 10.
Table 10: Rock Mass Properties
Geotechnical Unit Unit
Weight (pcf)
Hoek-Brown Failure Criterion
UCS (psi) GSI mi D mb s a
Knoxville Formation 140 3000 20 7 0 0.40203 0.000138 0.5437
Knoxville/Diabase Contact 150 7400 20 7 0 0.40203 0.000138 0.5437
Diabase 175 18300 55 15 0 3.007 0.006738 0.5040
Analyses were performed assuming the slope is not saturated, and therefore there are negligible pore
pressure effects. We also evaluated the overall slope stability assuming a pit lake forms with a surface
water elevation of 735 feet as part of the revised reclamation plan currently under consideration.
We selected Section A-A’ (shown in Figure 2) to analyze the highest and steepest slope in the quarry
where the contact between the Knoxville and the Diabase will be exposed. The location of geotechnical
units corresponding with Table 10 are shown in Figures 7 through 13.
We searched for the most critical shear surfaces in the overall slope configuration from the uppermost
bench in the Knoxville and passing through both the contact zone and the Diabase. We limited our
search to failures that would pass below individual benches, as bench failures would most likely consist of
sliding of rock blocks as discussed in Section 5.3.2 and would be either be removed during mining as part
of normal operations or retained on catch benches left in the slope.
6.1.2.2 Seismic Loading For this study, we evaluated the effect of seismic loading on the rock slopes by performing a pseudo-
static analysis. A pseudo-static analysis is a type of limit-equilibrium analysis used to assess the level of
stability of a slope subjected to ground accelerations likely to be experienced at the site during an
earthquake. In a pseudo-static analysis, the effect of the earthquake on the stability of the slope is
represented by a constant horizontal acceleration that, when multiplied by the weight of the failure mass,
produces a lateral de-stabilizing force that acts through the centroid of the slide mass. The horizontal
acceleration (expressed as a percentage of gravity, 32.2 ft/s2) that produces this lateral force is
represented by a parameter called the seismic coefficient (k). For limit-equilibrium SLIDE analyses, this
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additional force is incorporated into the equilibrium equations of the slice method and the FOS is
calculated.
The value of the seismic coefficient (k) used in this analysis is selected to reflect the anticipated level of
earthquake shaking at the site, or more specifically the accelerations acting on the potential failure mass.
The seismic coefficient used in slope stability analyses is assumed to be less than the PGA predicted for
the site because, during earthquake shaking, a time-variant spatial distribution of accelerations exists
within the slope and not all points in the slope move simultaneously with the same intensity. The seismic
coefficient, k, is selected based on expected soil behavior and seismicity of the site as represented by the
values of PGA, M and r as determined during our previous study (Golder, 2015) and consistent with
recommendations for performing pseudo-static analyses by Blake et al. (2002). Because the diabase rock
mass is considered a strain-softening material (i.e., because the post-peak strength is low relative to the
peak strength), a value of k equal to 0.21 was used in our pseudo-static analyses. A pseudo-static FOS
greater than 1.0 assuming k = 0.21 indicates the performance of the slope will be acceptable under
seismic loading.
6.1.2.3 Results of Analyses We performed the analyses over a range of pit depths and also restricted the search for the critical shear
surface (shear surface with the lowest FOS) to selected geotechnical units. For the overall slope
including at the end of mining and after reclamation is completed, the results of the slope stability
analyses are shown in Table 11.
Table 11: Results of Limit-Equilibrium Slope Stability Analyses for Overall Slope
Critical Failure Surface Case No. Figure No. Water Condition
Factor-of-Safety (FOS)
Static k= 0
Pseudostatic k=0.21
Overall Slope (toe to crest) (pit bottom at 300 feet)
1 7 No Pit Lake 2.51 1.88 2 8 Pit Lake 2.70 1.74
Toe of surface in Diabase 3 9 No Pit Lake 2.34 1.69 4 10 Pit Lake 2.38 1.60
Toe of surface in Knoxville/ Diabase Contact
5 11 No Pit Lake 2.02 1.41 6 12 Pit Lake 2.00 1.31
Toe of surface in Knoxville Formation 7 13 No Pit Lake 2.36 1.65
The critical shear surfaces for each of the analyses listed in Table 11 are provided in Figures 7 through
13. The critical shear surface is not the shear surface over the full height of the slope due to the high
strength diabase unit in the toe of the slope. The lowest factor of safety of 1.31 was obtained from the
shear surface shown in Figure 11 that passes through the Knoxville/Diabase contact.
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The results of these analyses indicate acceptable factors-of-safety are achieved for both static and
seismic loading for the overall slope and therefore the proposed slopes meet the requirements of
SMARA.
6.2 Limit Equilibrium Analysis of Overburden Fill Slopes
6.2.1 Overburden and Foundation Strength Parameters Table 12 summarizes the estimated strength parameters for the geotechnical materials of the overburden
fill and the soil-like foundation materials below the fill.
Table 12: Overburden and Foundation Strength Parameters
Strength Parameters
Overburden Fill Area Mohr-Coulomb
Geotechnical Unit Unit
Weight (pcf)
Effective Friction
Angle (φ') (˚)
Cohesion (c) (psi)
Overburden 130 39 0
Overburden/Kk (weathered) Contact 125 25 0
Kk (highly weathered) 125 25 3.5
Kk (moderately weathered) 140 25 20.8
6.2.2 Results of Analyses As part of our slope stability evaluation, we performed an infinite slope analyses to assist us in selecting
an appropriate slope for design of the overburden fill. In an infinite slope analysis, the potential sliding
mass is assumed to be a long, thin slab of material sliding on top of a continuous shear surface that is
parallel to the sloping ground surface. This will be the critical shear surface (surface with the lowest factor
of safety) for long straight continuous slopes composed of a cohesionless Mohr-Coulomb material.
The pseudo-static FOS for an infinite slope in a dry, Mohr-Coulomb material is calculated as follows
(Duncan and Wright, 2004):
FOS = c’+(γz cos2 (β) – kγz cos(β) sin(β))tan (∅’) γz sin (β) cos (β)+kγz cos2(β) Where:
c’ = effective cohesion z = depth of failure surface
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γ =the saturated unit weight of the soil β = the slope of ground surface ∅’ = effective friction angle of the soil k = seismic coefficient (k=0 for static analyses)
We selected a seismic coefficient, k, for use in the analyses following guidelines by Blake et al. (2002).
The results of the laboratory testing (Golder, 2015) indicate that the coarse, granular material comprising
the waste fill is not strain-softening. The pseudo-static analyses procedure described by Blake indicates
that the slope will have acceptable performance under seismic loading when k = 0.18 and the computed
FOS equal or greater than 1.0.
The results of these analyses are shown in Table 13. Table 13: Results of Infinite Slope Analyses for Overburden Fills
Type of Analysis
Slope Angle (degrees) k FOS
Static
34 0 1.20 33.7 (1.5H:1V) 0 1.21
33 0 1.25 32 0 1.30
26.6 (2H:1V) 0 1.62
Pseudo-static
33.7 (1.5H:1V) 0.18 0.84 29 0.18 0.99 28 0.18 1.03
26.6 (2H:1V) 0.18 1.08
The results of these analyses indicate adequate factors of safety for a 1.5H:1V slope (approximately 34
degrees) under static loading; however, this slope would not have an adequate factor of safety under
seismic loading. The pseudo-static analyses indicate the slope would have to be flatter than 1.8H:1V
(approximately 29 degrees) to achieve a FOS of 1.0 under seismic loading; therefore we recommend that
future overburden fill slopes be designed at a maximum slope of 2H:1V (approximately 26.6 degrees).
The results of infinite slope analyses for use in design of overburden fills are typically conservative
because they assume a very thin layer of soil slides along an infinitely long slope. The actual overburden
fill will have some finite dimension and the thickness of the shear surface of interest is likely to be greater
than just a few feet deep. Slope stability analyses that include a search for a critical shear surface will
yield somewhat higher factors of safety than indicated in Table 13 depending on the length and depth of
the fill slope; however, the slope angles from the infinite slope analyses provide constraints on the
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May 2015 25 Project No. 1520962
maximum achievable slope angles for overburden fill that will satisfy SMARA requirements for seismic
stability.
Limit equilibrium analyses for a block failure along the base of the fill, and for circular failure modes
intersecting the foundation yielded static FOS of 1.7 and 1.92, respectively, indicating that the foundation
is of adequate strength for the proposed fill. Seismic FOS exceeded 1.0 for foundation-related failures
modes.
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May 2015 26 Project No. 1520962
7.0 CONCLUSIONS AND RECOMMENDATIONS Our conclusions and recommendations are based on:
Our knowledge of geology of the site as observed in the field and literature review
The data we collected during both the drilling program in February 2015 and our site visit in March 2014
Our experience with similar high, steep slopes excavated in similar rock masses
Our understanding of geologic environments which are vulnerable to large-scale slope instability under static conditions and seismic loading
The results of the subsurface explorations, laboratory testing, and our engineering analyses
7.1 Conclusions
7.1.1 East Quarry Slopes: The major structures (i.e., discontinuities) that could result in large structurally-controlled
instability of east quarry slope are not present at the site
The formation of large deep-seated slope instability due to shear through the rock mass in the east slope of the quarry is not indicated by either the geologic conditions or our slope stability analyses for either seismic or static loading. The computed minimum factors of safety under static conditions and pseudo-static conditions meet the requirements of the Surface Mining and Reclamation Act (SMARA).
Rockfalls from bench slopes and small bench-scale failures due either to static or seismic load will likely either be mined out or retained on catch benches left in the overall pit slope during mining.
Differences between the geotechnical characterization and geologic models described in this report and the actual geotechnical and geologic conditions should be anticipated. Geologic risks related to the slope stability of the east side of the pit include:
Extensive weathering of the Knoxville Formation over time resulting in reduced strengths more like a soil than a rock mass.
Unidentified faults, geologic contacts, or changes in the orientation of bedding planes in the Knoxville Formation or orientation of dike contacts in the Diabase
Distribution of more highly fractured zones that could affect the ability to develop steep bench and stable bench faces and the ability to implement effective controlled blasting methods (pre-split and trim blasting)
7.1.2 Overburden Fill Slopes Overburden fill slopes of 2H:1V meet the current requirements for static and seismic
stability of the Surface Mining and Reclamation Act (SMARA) (FOS > 1.0).
Foundation conditions in the proposed overburden fill area (native slopes east-southeast of the quarry) appear suitable for the proposed fills provided that design of the fills provide proper stripping of surface soils and organics.
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May 2015 27 Project No. 1520962
7.2 Recommendations
7.2.1 East Quarry Slopes The east quarry slope can be designed using the slope configurations shown in Table 1
and illustrated in Figures 7 through 13.
The height and character of the various rock units exposed in the pit slope may change the factor of safety from that indicated in Figures 7 through 13. We recommend that the geologic model be verified as the slopes are excavated to confirm the assumptions used in this report.
Occasional bench-scale failures due to either rock blocks sliding along discontinuities or raveling may occur locally. Catch benches with appropriate berms (if required) should be left in the slope to retain material from such small-scale failures
We recommend that quarry personnel conduct regular visual inspections to identify conditions (e.g., tension cracks, excessive raveling, rockfall, etc.) that might indicate the development of an unstable overall slope. If potential signs of slope instability are observed, we recommend that you contact us so we may evaluate the conditions and the recommendations in this report and revise them, if appropriate.
7.2.2 Overburden Fill The purpose of these recommendations is to assist Cemex in design of a overburden fill. A final location
and configuration of a overburden fill has yet to be selected. The following recommendations will assist in
developing a preliminary design:
The slope of the overburden fill should be no greater than 2H:1V for overburden placed in lifts with little compactive effort (i.e., assumes wheel and track rolling only).
For preliminary design assume that a keyway at the base of the fill will be constructed to enhance stability. For preliminary designs, assume that the key way will be 30 foot to 50 foot wide by 5 foot depth. The keyway should be inspected to verify that all unsuitable soft and organic soils have been removed.
Keyways should be evaluated for the presence of seepage. If seepage is present, a geotechnical engineer should provide recommendations for a subdrain.
If the existing subsurface explorations do not adequately represent ground conditions, additional subsurface explorations consisting of test pits and borings may be required once a final location of the fill has been selected. We recommend that a slope stability analysis of the final overburden fill design be completed once a final location and configuration for the fill has been selected.
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May 2015 28 Project No. 1520962
8.0 USE OF THIS REPORT This report has been prepared for the exclusive use of Cemex and their consultants for specific
application to the Clayton Quarry mine design.
The conclusions and recommendations contained in this report are based on data obtained by others as
well as the site reconnaissance and subsurface explorations conducted by Golder. The methods used
generally indicate geologic conditions at the time and locations explored and sampled. Our assessment of
geologic conditions based on conditions exposed in the existing quarry (ground surface) and samples
obtained from widely spaced borings may not disclose geologic features either hidden from view or not
sampled in the borings; and such undisclosed geologic features may result in slope instability under
certain conditions. In addition, groundwater conditions can vary with time.
The contacts between geologic units indicated on the subsurface exploration logs and cross represent the
approximate boundaries between soil and/or bedrock units, and actual transitions may be more gradual.
Subsurface descriptions are based on conditions encountered at the time of exploration and conditions
outside of the exploration locations may vary from those encountered during this investigation.
The findings, conclusions, and recommendations presented in this report were prepared in accordance
with generally accepted geotechnical engineering practice that exists within the area at the time of the
work. No other warranty, expressed or implied, is made.
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May 2015 30 Project No. 15-20962
c:\users\blara\appdata\local\microsoft\windows\temporary internet files\content.outlook\cvlw1gpq\clayton quarry report_ east pit slope_final_wlf-5-11-15.docx
9.0 CLOSING We appreciate the opportunity to work with Cemex on this project. Please call us if you have any
questions or require clarification of our findings and recommendations.
GOLDER ASSOCIATES INC. George Lightwood William Fowler, PG, CEG Senior Engineer Principal Engineering Geologist GL/WF/rk
May 2015 31 Project No. 15-20962
10.0 REFERENCES Barton, N. and V. Chouby, 1977, The shear strength of rock joints in theory and practice. Rock
Mechanics, vol. 10, pp 1 – 54.
Bieniawski, Z.T., 1976, Rock mass classification in rock engineering. Proceedings, Symposium on Exploration for Rock Engineering, Johannesburg, Vol. 1, 1976, p. 97-106.
Blake, T.F., R.A. Hollingsworth, J.P. Stewart, 2002, Recommended Procedures for Implementation of DMG Special Publication 117 Guidelines for Analyzing and Mitigating Landslide Hazards in California, published by the Southern California Earthquake Center, June 2002.
California Geological Society, Special Publication 117, Guidelines for Evaluation and Mitigating Seismic Hazards in California, Revised September 2008.
Caltrans. 2010. Rock Logging, Classification, and Presentation Manual. State of California, Department of Transportation, Division of Engineering Services, Geotechnical Services.
Dibblee, T.W., 2006, Geologic Map of the Clayton quadrangle, Contra Costa County, California, Dibblee Geology Center Map #DF-192, Santa Barbara Museum of Natural History, Santa Barbara, California.
Dibblee, T.W., 1980, Preliminary geologic map of the Clayton quadrangle, Contra Costa County, California: U.S. Geological Survey, Open File Report no. 80-547.
Duncan, J.M. and S. G. Wright, 2005, Soil Strength and Slope Stability, Wiley, New York.
Golder, 2015, Evaluation of Pitslope Stability and Rockfall Hazard, Clayton Quarry, Clayton, California, Project No. 113-01127, report prepared for Mr. Ron Wilson, Cemex, Eldorado Hills, CA, Project Number 113-01127.
Hoek, E., 2012, Blast Damage Factor D, Technical note in RocNews, winter, 2012, dated February 2, 2012.
Hoek, E., and Brown, E.T., 1980. Underground Excavations in Rock, Institute of Mining and Metallurgy, London.
Hoek, E., Carranza-Torres, C., and Corkum, B., 2002. Hoek-Brown Failure Criterion, 2002 Edition. Proceedings, 5th North American Rock Mechanics Symposium, Toronto, p. 267-273.
Hoek, E., P.K. Kaiser, and W.F. Bawden, 1993, Support of Underground Excavations in Hard Rock, Taylor and Francis, New York.
Hoek, E., and Karzulovic, A., 2000. Rock-Mass Properties for Surface Mines, in Slope Stability in Surface Mining. Society for Mining, Metallurgy, and Exploration, Inc., p. 59-69.
Keefer, D.K. 1984. Landslides caused by earthquakes, Geological Society of America Bulletin, vol. 98, pp. 406-421.
Pampeyan, E.H., 1963, Geology and mineral deposits of Mt. Diablo, Contra Costa County, California Division of Mines and Geology Special Report 80.
Read, J., and Stacey, P., 2009. Guidelines for Open Pit Slope Design. Published by CRC Press/Balkema.
g:\projects\clayton quarry cemex\1520962 (cemex geotechnical investigation)\final report\clayton quarry report_ east pit slope_final_wlf-5-11-15.docx
May 2015 32 Project No. 15-20962
Rocscience, 2012, Slide: 2D Limit Equilibrium Slope Stability Analysis, Rocscience, Inc., Toronto, Ontario,
Canada.
Spencer, E., 1967, A method of analysis of the stability of embankments assuming parallel interslice forces, Geotechnique, Vol. 17, p. 11-26.
Williams, K. M., 1984, Geologic map and cross sections of the Coast Range Ophiolite at Mount Diablo, Contra Costa, County, California, U.S. Geological Survey, Open File Report no. 84-557.
g:\projects\clayton quarry cemex\1520962 (cemex geotechnical investigation)\final report\clayton quarry report_ east pit slope_final_wlf-5-11-15.docx
FIGURES
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
2014-04-30
RLK
GTL
GTL
WLF
113-01127 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
1
PROJECT LOCATION TITLE
CONSULTANT
Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
2014-04-30
RLK
GTL
GTL
WLF
003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
Cemex Clayton Quarry
Source: U.S. Geological Survey. Clayton quadrangle, California [map]. Photorevised 1980. 1:24,000. 7.5 Minute Series. Reston, Va: United States Department of the Interior, USGS, 1953.
Source: OpenStreetMap http://www.openstreetmap.org/copyright
15-20962 PROJECT No.
!(
!(
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!(
!(!(!(
!(
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x1
x2
x3
x4
x6x7
x9
x11
x12x13
x14
x15
x18 x19
x20
x21
x8
x10
x5
x16
x17
1500
1400
1300 1200
11001000
900800
600
700
600
700
600
700600
6143200.00 6144000.00 6144800.00 6145600.00
2160
000.00
2160
800.00
2161
600.00
2162
400.00
2163
200.00
CLIENTCEMEX
LEGEND!( Station!( Station on Db/Kk contact
Surface Contour (100ft. Intervals)Approximate Diabase/Knoxville ContactCross Section
NOTES
REFERENCECOORDINATE SYSTEM: NAD 1983 STATEPLANECALIFORNIA III FIPS 0403 FEETSERVICE LAYER CREDITS: SOURCE: ESRI,DIGITALGLOBE, GEOEYE, I-CUBED, USDA, USGS, AEX,GETMAPPING, AEROGRID, IGN, IGP, SWISSTOPO, ANDTHE GIS USER COMMUNITY
PROJECT
TITLESITE LAYOUT
113-01127 #### #### 2
07-05-2014DZFDZFLF####
Path: G:\GIS\Sites\ClaytonQuarry\Maps\SiteMap.mxd
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
CONSULTANT
PROJECT No. CONTROL REVIEW FIGURE
YYYY-MM-DDPREPAREDDESIGNREVIEWAPPROVED1 inch = 300 feet
300 0 300150Feet
C C'
B
B'
A'
A
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
2014-04-30
RLK
GTL
GTL
WLF
113-01127 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
4
EAST WALL (March 2014) TITLE
CONSULTANT
Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
2014-04-30
RLK
GTL
GTL
WLF
113-01127 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
15-20962 PROJECT No.
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
2014-04-30
RLK
GTL
GTL
WLF
113-01127 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
5
DEFINITION OF BENCH FACE ANGLE, CATCH BENCH, AND INTER-RAMP SLOPE ANGLE
TITLE
CONSULTANT
Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
2014-04-30
RLK
GTL
GTL
WLF
15-20962 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
PROJECT No.
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
15-20962 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
6
GEOLOGIC STRENGTH INDEX (GSI)
2014-05-05
RLK
GTL
GTL
WLF
FIGURE
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
15-20962 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
Pseudostatic Analysis (k=0.21)
2015-04-09
7
SAM
GTL
GTL
WLF
FIGURE
RESULTS OF STABILITY ANALYSIS – CASE 1
Static Analysis
NOTE: See Table 9 for loading conditions.
FS = 2.505
FS = 1.88
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
15-20962 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
Pseudostatic Analysis (k=0.21)
2015-04-09
8
SAM
GTL
GTL
WLF
FIGURE
RESULTS OF STABILITY ANALYSIS – CASE 2
Static Analysis
NOTE: See Table 9 for loading conditions.
FS = 1.74
FS = 2.70
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
15-20962 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
Pseudostatic Analysis (k=0.21)
2015-04-09
9
SAM
GTL
GTL
WLF
FIGURE
RESULTS OF STABILITY ANALYSIS – CASE 3
Static Analysis
NOTE: See Table 9 for loading conditions.
FS = 1.69
FS = 2.34
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
15-20962 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
RESULTS OF STABILITY ANALYSIS – CASE 4
Pseudostatic Analysis (k=0.21)
Static Analysis
10
2015-04-09
SAM
GTL
GTL
WLF
FIGURE NOTE: See Table 9 for loading conditions.
FS = 1.60
FS = 2.38
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
15-20962 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
2015-04-09
11
SAM
GTL
GTL
WLF
FIGURE
RESULTS OF STABILITY ANALYSIS – CASE 5
Pseudostatic Analysis (k=0.21)
Static Analysis
NOTE: See Table 9 for loading conditions.
FS = 1.41
FS = 2.02
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
15-20962 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
12
2015-04-09
SAM
GTL
GTL
WLF
FIGURE
RESULTS OF STABILITY ANALYSIS – CASE 6
Pseudostatic Analysis (k=0.21)
Static Analysis
NOTE: See Table 9 for loading conditions.
FS = 1.31
FS = 2.00
TITLE
CONSULTANT
PROJECT No. Rev.
YYYY-MM-DD
PREPARED
DESIGN
REVIEW
APPROVED
15-20962 003 0 PHASE No. FIGURE
CLIENT
PROJECT
CEMEX
GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY
13
2015-04-09
SAM
GTL
GTL
WLF
FIGURE
RESULTS OF STABILITY ANALYSIS – CASE 7
Pseudostatic Analysis (k=0.21)
Static Analysis
NOTE: See Table 9 for loading conditions.
FS = 1.65
FS = 2.36
APPENDIX A
Clayton Quarry Geotechnical DrillingDate:
Project No. 1520962.002 Azimuth Elevation 879 Sheet 1 of 1Borehole # B1 Inclination Ref. Point Logged by Leah FeigelsonDrilling Method HQ N 37° 55 25 W 121° 56 49 Drill Rig mud rotary
Rubble Gouge
ROCK TYPE
RUN
From
(ft.)
To (f
t.)
Rec
over
y
Bed
ding
Dom
inan
t
RQ
D, f
t
Nat
ural
Fra
ctur
e C
ount
(N
/A fo
r "ic
e cu
be"
bx)
Ave
rage
Min
imum
Stre
ngth
Inde
x
Wea
ther
ing
Inde
x
Dep
th
TYPE
Cou
nt
Shap
e
Rou
ghne
ss
Infil
l
Thic
knes
s (m
m)
JRC
JCR
From
TO Type
From
TO
ADDITIONAL TESTING OR COMMENTS, SAMPLES COLLECTED
0.0 14.0 CASING set to 14 feet.
1 14.0 15.0 0.7 Drilling through waste dump; loosing2 15.0 20.0 0.8 circulation, therefore low recovery. Fines3 20.0 25.0 0.9 washed away, gravel/cobbles stay.4 25.0 26.0 0.35 26.0 31.0 0.76 31.0 36.0 0.6 checked depth with tape, confirmed at 36 feet.7 36.0 39.0 0.78 39.0 41.0 0.2 checked depth with tape, confirmed at 41 feet.9 41.0 42.5 0.2
10 42.5 44.0 0.511 44.0 45.0 0.411 45.0 46.0 0.7 N 0.0 7 10 8 R3 W3 46.0 B2 1 64 PL K ml C 8 8 45.4 45.7 Broken shale pieces are angular and have12 46.0 51.0 2.0 N 0.0 20 12 10 R3 W3 46.0 51.0 slicks, some pyrite on quartz vein13 51.0 54.0 1.5 N 0.0 15 12 10 R3 W3 52.9 J2 1 47 PL SR ml C 8 10
52.9 J2 1 32 PL SM ml C 2 8 rods stuck at 54 feet (took 1 day to un‐plug)53.5 J3 1 47 I SR ml C 10 14
14 54.0 56.0 2.0 N 0.4 16 12 10 R3 W2 54.2 B2 1 41 I K ml C 10 8 at 55.3'‐ a 0.3' section of sheared shale55.3 B2 1 41 PL K ml C 8 6 (fine bedding with some slicks)55.5 B2 1 67 PL SR ml C 12 10
15 56.0 57.8 0.5 N 0.0 5 10 8 R3 W3 at 57.8'‐ finely sheared at contactclayey SILTSTONE, heavily fractured 15 57.8 61.0 3.2 N 0.0 32 6 4 S4 W4 57.8 61.0 cl, ml *sample collected 59.5‐60.0 clayey siltstoneCLAYSTONE, dark gray, fractured 16 61.0 66.0 1.5 N 0.0 15 12 10 R3 W3 65.7 V1 1 62 PL R ml, cl <1 10 12 64.5 66.0 blocky fractures, angular
CLAYSTONE, light gray, abundant quartz veining 17 66.0 69.4 0.7 N 0.5 2 14 12 R3 W2 69.4 C2 1 62 I VR ml, cl C 16 14clayey SILTSTONE, dark gray 17 69.4 70.0 0.6 N 0.0 6 6 4 S3 W4 70.0 C1 1 36 I SR ml, cl <1 12 16 69.4 70.0 cl, ml at 70'‐ quartz veins and pyrite
CLAYSTONE, light gray, abundant quartz veining 17 70.0 70.6 0.6 N 0.0 4 12 10 R4 W2 70.4 V1 1 36 PL SR ml, cl C 8 12clayey SILTSTONE, dark gray 17 70.6 71.0 0.4 N 0.0 4 6 4 S1 W6 70.6 V2 1 85 I R ml, cl <1 18 20 70.6 71.0 cl, ml material from the shoe, therefore broken
clayey SILTSTONE, dark gray, heavily fractured 18 71.0 75.0 1.5 N 0.0 15 6 4 S4 W4 71.0 75.0 cl, ml heavily fractured, blocky
19 75.0 77.0 2.0 N 0.0 20 12 10 R3 W3 75.0 77.020 77.0 81.0 1.1 N 0.0 11 10 8 S5 W421 81.0 84.0 0.4 N 0.0 4 12 10 R3 W3 84.0 C2 1 44 I VR ml, cl C 18 1621 84.0 86.0 2.0 N 0.0 20 8 6 S4 W4 85.5 J2 1 44 C VR ml, cl <2 16 14 84.0 89.0 cl, ml some slicks at contact at 84.7'22 86.0 89.0 3.0 N 0.0 30 8 6 S4 W4 87.1 J2 1 64 I VR ml, cl <2 16 14
87.8 J2 1 48 PL R ml, cl <1 14 14 *sample collected 86.8‐87.6' clayey siltstone23 89.0 91.0 0.8 N 0.0 8 8 6 S4 W4 (direct shear/triax)24 91.0 91.5 0.2 N 0.0 2 4 2 S2 W6 91.0 94.0 cl, ml24 91.5 92.0 0.5 N 0.0 5 8 6 S4 W4 *sample collected 91.4‐92.0' silty claystone24 92.0 92.4 0.4 N 0.0 4 6 4 S3 W524 92.4 93.6 1.2 N 0.0 12 8 6 S5 W4 92.8 J1 1 50 PL SR ml, cl C 10 824 93.6 94.0 0.4 N 0.0 4 6 4 S3 W5
silty CLAYSTONE 25 94.0 96.0 1.1 N 0.0 11 12 10 R3 W3 95.4 J2 1 53 2 C ml, cl C 8 1026 96.0 96.8 0.8 N 0.4 4 12 10 R3 W326 96.8 98.0 1.2 N 0.0 12 8 6 S5 W4 *sample collected 96.9‐97.5' silty claystone26 98.0 99.0 1.0 N 0.0 10 6 4 S4 W4 98.0 99.0 cl, ml
silty CLAYSTONE 27 99.0 100.0 1.0 N 0.0 10 8 6 S5 W4 *sample collected 99.2‐99.7' silty claystone
TD=100'
Broken Core (smaller than core diameter)
Vertical
2/17/15‐2/19/15
Run Data
Recovery & Other Basic InformationJCR Strength Index
Detailed Discontinuity Data Gouge
clayey SILTSTONE
WASTE DUMP
CLAYSTONE, dark brownish‐gray
clayey SILTSTONE to silty CLAYSTONE, dark gray, fractured
CASING set to 14 feet.
01 in
152-0952
FIGURE
1
2015-03-16
JGE
GL
GL
CLAYTON QUARRY
2015 GEOTECHNICAL INVESTIGATION
CEMEX
CONTRA COSTA COUNTY
CLAYTON, CALIFORNIA
B1 DOWNHOLE PLOT
TITLE
PROJECT NO. REV.
PROJECTCLIENT
IF
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SU
RE
ME
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PREPARED
DESIGNED
REVIEWED
APPROVED
YYYY-MM-DD
Path: \\reno\data\Cemex - Clayton Quarry\Downhole Plot\ | File Name: Downhole Plot11x17.dwg
ISRM
STRENGTH
DESCRIPTION
UCS RANGE (PSI)
S1 VERY SOFT CLAY <4
S2 SOFT CLAY 4-7
S3 FIRM CLAY 7-15
S4 STIFF CLAY 15-35
S5 VERY STIFF CLAY 35-70
S6 HARD CLAY >70
R0 EXTREMELY WEAK ROCK 35-150
R1 VERY WEAK ROCK 150-725
R2 WEAK ROCK725-3,500
R3 MEDIUM STRONG ROCK3,500-7,500
R4 STRONG ROCK7,500-15,000
R5 VERY STRONG ROCK15,000-35,000
R6 EXTREMELY STRONG ROCK<35,000
LEGEND
WASTE DUMP
CLAYSTONE
SILTSTONE
CASING
RMR CLASSIFICATION
0 - 20
21 - 40
41 - 60
61 - 80
81 - 100
VERY POOR
POOR
FAIR
GOOD
VERY GOOD
CLAYEY SILT, low to medium plastic fines, some fine sand, trace medium to coarsesand, sub-angular to angluar; reddish-brown; moist; very soft.
gravelly CLAYEY SILT, low to medium plastic fines, some fine to coarse sand;reddish-brown, mottled; moist; soft.
gravelly CLAYEY SILT, low to medium plastic fines, some fine to coarse sand;reddish-brown, mottled; moist; very stiff.
SILTY CLAY, medium plastic fines, some medium to coarse sand, sub-angular;yellowish-brown; moist; firm.
SILTY CLAY to CLAY, medium to high plastic fines, trace fine to coarse sand,yellowish-brown; moist; very stiff.
gravelly SILTY CLAY, medium plastic fines, some sand, sub-angular to angular;yellowish-brown, mottled tan, green, red; moist; firm.
gravelly SILTY CLAY, medium plastic fines, some sand, sub-angular to angular;yellowish-brown, mottled tan, green, red; moist; very stiff.
Bottom of borehole at 31.5 feet.
ML
ML
ML
CL
CL-CH
CL
CL
18/18
18/18
18/18
18/18
18/18
12/18
MCB2-5
SPTB2-10
MCB2-15
SPTB2-20
MCB2-25
SPTB2-30
356
N=11
5811
N=19
6811
N=19
71112
N=23
4812
N=20
4811
N=19
2.0
10.0
15.0
20.0
25.0
30.0
31.5
LOGGED BY LF
GRAVEL PACK TYPE ----
CONTINUED
LOCATION Clayton, CA
SCREEN TYPE/SLOT ----
CASING TYPE/DIAMETER ----
GROUND ELEVATION
TOP OF CASING ----
REMARKS
GROUT TYPE/QUANTITY Neat cement grout.
DRILLING METHOD
LITHOLOGIC DESCRIPTION
BORING NUMBER B2PAGE 1 OF 1
GR
AP
HIC
LOG
PROJECT NAME Clayton Quarry
U.S
.C.S
.
5
10
15
20
25
30
DE
PT
H(f
t. B
GL)
PROJECT NUMBER 152-0962 DATE STARTED 2/20/15
DATE COMPLETED 2/20/15
L o g o
Golder AssociatesTelephone: 408-220-9223Fax: 408-220-9224
INC
HE
S
BLO
WC
OU
NT
SA
MP
LIN
GM
ET
HO
DA
ND
SA
MP
LE ID
CLA
YT
ON
QU
AR
RY
BO
RIN
G G
INT
ST
D U
S L
AB
_CLA
YT
ON
.GP
J L
OG
A E
WN
N01
.GD
T 3
/13/
15
CO
NT
AC
TD
EP
TH
L o g o
CLAY, medium to high plastic fines, trace coarse sand, trace roots; brown; moist; verysoft.
CLAYSTONE/SILTSTONE, weathered; yellowish-brown; moist; hard.
CLAYSTONE/SILTSTONE, weathered; yellowish-brown; moist; very stiff.
CLAYSTONE/SILTSTONE, weathered; yellowish-brown; moist; hard.
CLAYSTONE/SILTSTONE, weathered; yellowish-brown; moist; very stiff.
CLAYSTONE/SILTSTONE, weathered; yellowish-brown; moist; hard.
CLAYSTONE/SILTSTONE, weathered; yellowish-brown; moist; very stiff.
Bottom of borehole at 31.5 feet.
CH
12/18
12/18
9/11
15/18
12/18
12/18
MCB3-5
SPTB3-10
MCB3-15
SPTB3-20
MCB3-25
SPTB3-30
82126
N=47
91115
N=26
1350 for 5"
5917
N=26
92735
N=62
81013
N=23
5.0
10.0
15.0
20.0
25.0
30.0
31.5
LOGGED BY LF
GRAVEL PACK TYPE ----
CONTINUED
LOCATION Clayton, CA
SCREEN TYPE/SLOT ----
CASING TYPE/DIAMETER ----
GROUND ELEVATION
TOP OF CASING ----
REMARKS
GROUT TYPE/QUANTITY Neat cement grout.
DRILLING METHOD
LITHOLOGIC DESCRIPTION
BORING NUMBER B3PAGE 1 OF 1
GR
AP
HIC
LOG
PROJECT NAME Clayton Quarry
U.S
.C.S
.
5
10
15
20
25
30
DE
PT
H(f
t. B
GL)
PROJECT NUMBER 152-0962 DATE STARTED 2/20/15
DATE COMPLETED 2/20/15
L o g o
Golder AssociatesTelephone: 408-220-9223Fax: 408-220-9224
INC
HE
S
BLO
WC
OU
NT
SA
MP
LIN
GM
ET
HO
DA
ND
SA
MP
LE ID
CLA
YT
ON
QU
AR
RY
BO
RIN
G G
INT
ST
D U
S L
AB
_CLA
YT
ON
.GP
J L
OG
A E
WN
N01
.GD
T 3
/13/
15
CO
NT
AC
TD
EP
TH
L o g o
TABLE 1
ABBREVIATIONS FOR GEOTECHNICAL ROCK CORE LOGGING Type Code Description Planarity Code Description
J1 Natural joint PL Planar J2 Joint, origin uncertain C Curved J3 Joint caused by drilling or handling U Undulating B1 Natural fracture along bedding plane ST Stepped B2 Fracture along bedding plane, origin uncertain I Irregular
B3 Fracture along bedding plane caused by drilling or handling
BT Trace of intact bedding plane Roughness Code Description
FO1 Natural fracture along foliation plane P Polished FO2 Fracture along foliation plane, origin uncertain K Slickensided
FO3 Fracture along foliation plane caused by drilling or handling SM Smooth
FOT Trace of intact foliation R Rough V1 Natural fracture along vein VR Very Rough V2 Fracture along vein, origin uncertian
V3 Fracture along vein caused by drilling or handling Infill Type Code Description
VT Trace of intact vein Ca Calcite FB1 Natural fracture along flow banding Cl Clay FB2 Fracture along flow banding, origin uncertain Si Silica
FB3 Fracture along flow banding caused by drilling or handling Qtz Quartz
FBT Trace of intact flow banding Chl Chlorite C1 Natural fracture along contact G Gouge C2 Fracture along contact, origin uncertain Bx Breccia
C3 Fracture along contact caused by drilling or handling Hm Hematite
CT Trace of intact contact Lm Limonite F Fault FeOx Iron Oxide S Shear
����������� �
FIGURE
TP-1.2-2
5
PHYSICAL DESCRIPTIVE TERMS
����������� �
FIGURE
TP-1.2-2
6
DISCONTINUITY ROUGHNESS PROFILE
APPENDIX B
(X=NO)PERCENTFINERSIZE
PASS?SPEC.*PERCENTSIEVE
Project No:
Project:Client:
Elev./Depth:Location:Date:Source of Sample:Sample No.:
Remarks
Classification
Coefficients
Atterberg Limits
Soil Description
*
AASHTO=USCS=
Cc=Cu=D10=D15=D30=D50=D60=D85=
PI=LL=PL=
Particle Size Distribution Report
10
20
30
40
50
60
70
80
90
0
100
PE
RC
EN
T F
INE
R
100 10 1 0.1 0.01 0.001500GRAIN SIZE - mm
% COBBLES % GRAVEL % SAND % SILT % CLAY
6 in
.
3 in
.
2 in
.
1-1/
2 in
.
1 in
.
3/4
in.
1/2
in.
3/8
in.
#4 #10
#20
#30
#40
#60
#100
#140
#200
0.0 2.6 68.6 22.2 6.6
Figure287-201
Clayton Quarry - 1520962
Golder Associates
91.4-92'3/13/15B-1
SC-SM
2.9984.170.00520.01400.08290.2790.4401.19
72518
Very Dark Gray Silty, Clayey SAND
(no specification provided)
COOPER TESTING LABORATORY
100.099.597.494.167.759.251.538.728.825.019.916.814.612.811.09.37.16.75.5
3/4 in.3/8 in.
#4#10#30#40#50
#100#200#270
0.0345 mm.0.0220 mm.0.0128 mm.0.0091 mm.0.0065 mm.0.0046 mm.0.0033 mm.0.0023 mm.0.0013 mm.
(X=NO)PERCENTFINERSIZE
PASS?SPEC.*PERCENTSIEVE
Project No:
Project:Client:
Elev./Depth:Location:Date:Source of Sample:Sample No.:
Remarks
Classification
Coefficients
Atterberg Limits
Soil Description
*
AASHTO=USCS=
Cc=Cu=D10=D15=D30=D50=D60=D85=
PI=LL=PL=
Particle Size Distribution Report
10
20
30
40
50
60
70
80
90
0
100
PE
RC
EN
T F
INE
R
100 10 1 0.1 0.01 0.001500GRAIN SIZE - mm
% COBBLES % GRAVEL % SAND % SILT % CLAY
6 in
.
3 in
.
2 in
.
1-1/
2 in
.
1 in
.
3/4
in.
1/2
in.
3/8
in.
#4 #10
#20
#30
#40
#60
#100
#140
#200
0.0 26.0 35.7 22.7 15.6
Figure287-201
Clayton Quarry - 1520962
Golder Associates
5.5-6'3/13/15B-2
Due to the small sample size, relative to the largestparticle size, this data should be considered to beapproximate.
SC
0.00180.03100.2840.85812.0
183618
Dark Yellowish Brown Lean Clayey SAND w/ Gravel
(no specification provided)
COOPER TESTING LABORATORY
100.094.581.074.068.456.553.650.544.338.335.830.026.724.322.419.618.017.015.913.0
1 in.3/4 in.3/8 in.
#4#10#30#40#50
#100#200#270
0.0310 mm.0.0200 mm.0.0118 mm.0.0084 mm.0.0060 mm.0.0043 mm.0.0030 mm.0.0022 mm.0.0013 mm.
Project:
Remarks:Client:Project No.
%<#200%<#40PIPLLLMATERIAL DESCRIPTION
LIQUID AND PLASTIC LIMITS TEST REPORT
Source: B-1 Elev./Depth: 91.4-92'
Figure
LIQUID AND PLASTIC LIMITS TEST REPORT
COOPER TESTING LABORATORY
USCS
Golder Associates287-201
SC-SM28.859.271825Very Dark Gray Silty, Clayey SAND
Clayton Quarry - 1520962
Source: B-2 Elev./Depth: 5.5-6'
SC38.353.6181836Dark Yellowish Brown Lean Clayey SAND w/ Gravel
Source: B-2 Elev./Depth: 10-11.5'
212041Dark Yellowish Brown Sandy Lean CLAY
Source: B-3 Elev./Depth: 5.5-6'
292251Dark Yellowish Brown Sandy Fat CLAY/ Fat Clayey
SAND w/ Gravel
Source: B-3 Elev./Depth: 10.5-11.5'
152439Yellowish Brown Lean Clayey SAND
5 10 20 25 30 4020
28
36
44
52
60
NUMBER OF BLOWS
WA
TE
R C
ON
TE
NT
10 30 50 70 90 110LIQUID LIMIT
10
20
30
40
50
60P
LAS
TIC
ITY
IND
EX
47
CL-ML
CL or OL
CH or OH
ML or OL MH or OH
Dashed line indicates the approximateupper limit boundary for natural soils
APPENDIX C
Project No.:
Project:
Client:
Cu
Cc
COEFFICIENTS
D10
D30
D60
REMARKS:GRAIN SIZE
SOIL DESCRIPTIONPERCENT FINERSIEVEPERCENT FINERSIEVE
LLPLAASHTOUSCS% CLAY% SILT% SAND% GRAVEL
sizesizenumber
Particle Size Distribution Report
10
20
30
40
50
60
70
80
90
0
100
PE
RC
EN
T FI
NE
R
100 10 1 0.1 0.01 0.001200GRAIN SIZE - mm
6 in
.
3 in
.
2 in
.
1-1/
2 in
.
1 in
.
3/4
in.
1/2
in.
3/8
in.
#4 #10
#20
#30
#40
#60
#100
#140
#200
Figure
% COBBLES
287-147
Clayton Quarry Slope Evaluation - 113-01127Golder Associates, Inc.
Source: X19 Elev./Depth: Surface
1.47
37.718.3SC31.648.819.6
inches Dark Yellowish Brown Lean Clayey SAND w/Gravel
COOPER TESTING LABORATORY
Source: X20+21 Sample No.: Composite Elev./Depth: Surface
0.9496.22
25.517.0GC14.938.047.1
Yellowish Brown Lean Clayey GRAVEL w/Sand
80.465.148.245.142.137.031.6
#4#10#30#40#50
#100#200
100.0
98.597.095.792.690.0
3"2.5
21.5"
1"3/4"1/2
3/8"
52.938.326.224.021.918.414.9
100.099.498.493.388.778.671.7
Project:Remarks:Client:Project No.
%<#200%<#40PIPLLLMATERIAL DESCRIPTION
LIQUID AND PLASTIC LIMITS TEST REPORT
Source: X19 Elev./Depth: Surface
Figure
LIQUID AND PLASTIC LIMITS TEST REPORT
COOPER TESTING LABORATORY
USCS
Golder Associates, Inc.287-147
SC31.645.119.418.337.7Dark Yellowish Brown Lean Clayey SAND w/ Gravel
Clayton Quarry Slope Evaluation - 113-01127
Source: X20+21 Sample No.: Composite Elev./Depth: Surface
GC14.924.08.517.025.5Yellowish Brown Lean Clayey GRAVEL w/ Sand
5 10 20 25 30 4023
27
31
35
39
43
NUMBER OF BLOWS
WA
TER
CO
NTE
NT
10 30 50 70 90 110LIQUID LIMIT
10
20
30
40
50
60P
LAS
TIC
ITY
IND
EX
47 CL-ML
CL or OL
CH or OH
ML or OL MH or OH
Dashed line indicates the approximateupper limit boundary for natural soils
654321
Curve No.
Project:Remarks:Client:Project No.
Material Description
TESTING DATA
AASHTOUSCS%<#200PILLSp.G.NM
Soil Data
SievePassingTest Performed on Material
Mold Size:Blows per Layer:Number of Layers:Hammer Drop:Hammer Wt.:
Test Specification:
DRY DENSITY
MOISTURE
TARE #2
WD + T #2
WW + T #2
TARE #1
WD + T #1
WW + T #1
WM
WM + WS
COMPACTION TEST REPORTD
ry d
ensi
ty, p
cf
Water content, %
131.5
134.0
136.5
139.0
141.5
144.0
2 4 6 8 10 12 14
ZAV SpG2.9
Figure
COMPACTION TEST REPORT
COOPER TESTING LABORATORY
Source: X20+21 Sample No.: Composite Elev./Depth: Surface
ROCK CORRECTED TEST RESULTS UNCORRECTED
%>3/8 in.
Material scalped on the 1/2" sieve.Golder Associates, Inc.287-147
Yellowish Brown Lean Clayey GRAVEL w/Sand
6.9
2.7
3/8 in.
.03333 cu.ft.25five
18 in.10 lb.
Oversize correction applied to each pointASTM D 1557-00 Method B Modified
Clayton Quarry Slope Evaluation - 113-01127
137.6135.9141.8140.74.910.38.66.8
318.10326.60324.80293.80817.30914.30968.70798.60842.80978.701027.20834.704.424.424.424.429.189.389.529.39
8.5 % Optimum moisture = 8.1 %
140.7 pcf Maximum dry density = 142.2 pcf
Triaxial Consolidated Undrained with Pore PressureASTM D4767
Sample: 1 2 3 4
MC, % 6.3 6.0 6.4
DD, pcf 120.7 121.0 120.5
Sat. % 42.8 41.4 43.7
Void Ratio 0.396 0.393 0.399
Diameter in 2.86 2.86 2.86
Height, in 6.00 6.00 6.00
MC, % 13.1 11.1 12.0
DD, pcf 124.4 129.7 127.1
Sat. % 100.0 100.0 100.0
Void Ratio 0.354 0.299 0.325
Diameter, in 2.84 2.79 2.82
Height, in 5.92 5.87 5.85
Cell, psi 104.9 120.1 149.9
BP, psi 90.0 89.0 89.6
Job No.: 287-147 Date: ####### Strain, % 5.0 5.0 5.0
Client: BY:DC Deviator ksf 1.706 3.340 6.501
Project: Excess PP 1.695 3.339 6.856
Sample 1) X20+X21;Composite @ Surface Sigma 1 2.161 4.479 8.326
Sample 2) X20+X21;Composite @ Surface Sigma 3 0.455 1.139 1.825
Sample 3) X20+X21;Composite @ Surface P, ksf 1.308 2.809 5.075
Sample 4) Q, ksf 0.853 1.670 3.250
Stress Ratio 4.753 3.931 4.562
Rate in/min 0.0005 0.0005 0.0005
Total C 0.0 ksfTotal phi 15.9 degrees
Eff. C 0.0 ksfEff. Phi 38.8 degrees
Remolded to 85% of 142.2 @ 5.7 (OPT-2.5%).
Yellowish Brown Lean Clayey GRAVEL w/ Sand
Final
Effective Stresses At:
Clayton Quarry Slope Evaluation - 113-01127Golder Associates
Yellowish Brown Lean Clayey GRAVEL w/ Sand
Yellowish Brown Lean Clayey GRAVEL w/ Sand
0
4
8
0 4 8 12 16
Shea
r Str
ess,
ksf
Normal Stress, ksf
Total Stress
Effective Stress
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 5 10 15 20 25
Dev
iato
r Str
ess,
psf
Strain, %
Stress-Strain Response
Sample 1Sample 2Sample 3Sample 4
-70
-60
-50
-40
-30
-20
-10
00.01 0.10 1.00 10.00 100.00 1000.00 10000.00
Pore
Vol
, ml
Elapsed Time, min.
Consolidation Phase
Sample-1
Sample-2
Sample-3
Sample-4
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
Q, K
SF
.
P, ksf
P vs. Q
Sample 1Sample 2Sample 3Sample 4
(σ1 + σ3) / 2
(σ1 -
σ3)
/ 2
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 2 4 6 8 10 12 14 16 18 20
Dev
iato
r Str
ess,
psf
Strain, %
Stress-Strain Curves
Sample 1Sample 2Sample 3Sample 4
0
1000
2000
3000
4000
5000
6000
7000
8000
0 5 10 15 20 25
Exce
ss P
ore
Pres
sure
, psf
Strain, %
Pore Pressure Response
Sample 1Sample 2Sample 3Sample 4
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0 5 10 15 20 25
Stre
ss R
atio
Strain, %
Stress Ratio Sigma1/Sigma3
Sample 1Sample 2Sample 3Sample 4
Golder Associates Inc. 425 Lakeside Drive
Sunnyvale, CA 94085 Tel: (408) 220-9223 Fax: (408) 220-9224
Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation