AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT BARBARA COSANTI...
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AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT BARBARA COSANTI N. SQUEGLIA D.C.F. LO PRESTI University of Pisa – D.E.S.T.eC. WORKSHOP ON PENETRATION TESTING October 9 th , 2014 Auditorium Opera Primaziale, Pisa
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Transcript of AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT BARBARA COSANTI...
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS
USING CPT
BARBARA COSANTIN. SQUEGLIA
D.C.F. LO PRESTI
University of Pisa – D.E.S.T.eC.
WORKSHOP ON PENETRATION TESTINGOctober 9th, 2014
Auditorium Opera Primaziale, Pisa
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
Presentation outlineINTRODUCTION1
2 THE METHOD
3 HYPOTHESES
4 THE EQUIPMENT
5 LABORATORY TESTS
6 RESULTS
7 CONCLUSIONS
BARBARA COSANTI, PhD
INTRODUCTION12 THE METHOD
3 HYPOTHESES
4 THE EQUIPMENT
56 RESULTS
7 CONCLUSIONS
LABORATORY TESTS
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
Introduction1Compaction = Densification of soil by removing air
voids using mechanical equipment
Improving soil strength by increasing the unit weightIncreasing the bearing capacity of foundationsDecreasing the undesirable settlement of structuresControl undesirable volume changesReduction in hydraulic conductivityIncreasing the stability of slopes
Objectives
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
River embankments
CAUSES of
FAILURE
DESIGN ASSESSMENT of the
SAFETY DEGREESaturated for only a short
period of time
POOR ATTENTION
Different erosion mechanisms andslope instability
POOR DEGREE OF COMPACTION
=PREDISPOSING
FACTOR
Definition of design values for strength and permeability
characteristics
DEPENDENCY ON THE DEGREE OF
COMPACTION
NEED FOR AN EXPEDITIOUS AND ACCURATE METHOD TO EVALUATE DEGREE OF COMPACTION
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
INTRODUCTION12 THE METHOD
3 HYPOTHESES
4 THE EQUIPMENT
56 RESULTS
7 CONCLUSIONS
LABORATORY TESTS
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
EVALUATION OF THE DEGREE OF COMPACTIONOF RIVER EMBANKMENTS
CPT tests in situ
CPT TESTS IN LABORATORY
in a mini CC with a mini CPT
using samples at given densities
TIP RESISTANCE TARGET PROFILE
qc LAB
Vs
+
QUALITY CONTROL
After completion
In situ stress statewhen relevant
Existing embankments: evaluation of the degree of compaction Embankments under construction: it is possible (a‒priori) to establish which is the expected qc corresponding to a prescribed density
( )
The method2AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
INTRODUCTION12 THE METHOD
3 HYPOTHESES
4 THE EQUIPMENT
56 RESULTS
7 CONCLUSIONS
LABORATORY TESTS
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
I.qc from CPT (d= 35.7 mm)
qcLAB from mini-CPT (d= 8 mm)
The tip resistance is not affected by the tip diameter
Hypotheses3
0 2 4 6 8 10
q c [M P a]
160
120
80
40
0
de
pth
[cm
]
s tandard
m in i
BARBARA COSANTI, PhD
Normalized velocity(Finnie & Randolph, 1994)
Where: v: velocity of the penetrometerd: diameter of the penetrometercv: coefficient of consolidation of the soil
Vmini-CPT = 1/4 VCPT Even if:
UNSATURATED SILT MIXTURES
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
FOR DRY SAND →
III. IN SITU STRESS STATE →
(Jamiolkowski et al. 1988)
(Baldi et al. 1986, Jamiolkowski et al. 1988, Garizio 1997, Jamiolkowski et al. 2000, 2001)
Hypotheses3
BARBARA COSANTI, PhD
II.
Estimate of the vertical effective stress component v
At-rest earth pressure coefficient → DMT test
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
DMT-A DMT-AzDMT zCPT -- 30 d -- zCPT -- 15 d --
(m) (m) (kPa) (m) (bar)3.00 3.003.10 86 3.10 853.20 97 3.20 863.30 84 3.30 843.40 84 3.40 873.50 85 3.50 953.60 94 3.60 111
3.70 3.70 82 3.70 1223.80 3.80 1143.90 3.90 1114.00 4.00 974.10 4.10 964.20 4.20 894.30 4.30 864.40 4.40
DMT-A (kPa)
3.00
3.20
3.40
3.60
3.80
4.00
4.20
4.40
80 90 100 110 120 130
z (m)
15d - 53 cm
30d - 107 cm
DMT-A base
CC diameter
Mini-CPT diameter= 40
Diameter of the biggest particle
Mini-CPT diameter 4
Hypotheses3
BARBARA COSANTI, PhD
The effects of the mini–chamber sizes can be considered negligible if:IV.
V.
DMT blade location
CPT at 30d distance
CPT at 15d distance
When the horizontal distance between DMT and CPT is 20 times the cone diameter the DMT is no more sensitive to the passage of the cone
It is acceptable:
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
Hypotheses3
BARBARA COSANTI, PhD
The method has been successfully used in some case histories
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
qcLAB,80%
qcLAB,90%
CPT n°1 CPT n°2 CPT n°3
(Modified Proctor)
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
qcLAB,80%
qcLAB,90%
CPT n°1
CPT n°2
CPT n°3
CPT n°4
partially disturbed samples
BARBARA COSANTI, PhD
INTRODUCTION12 THE METHOD
3 HYPOTHESES
4 THE EQUIPMENT
56 RESULTS
7 CONCLUSIONS
LABORATORY TESTS
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
Developed by the Geotechnical Laboratory of the University of Pisa in partnership with Pagani Geotechnical Equipment
The equipment4
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
Diameter = 320 mm; Height = 210 mm
Top boundary → rigidLateral and bottom boundaries → flexible → provided with latex membranes
THE EQUIPMENT
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
THE EQUIPMENT
All the possible chamber boundary conditions can be applied:- BC1 = h = cost; v = cost- BC2 = h = 0; v = 0- BC3 = h = 0; v = cost- BC4 = h = cost; v = 0.
BARBARA COSANTI, PhD
The membranes allow the independent application of horizontal and vertical stresses through a compressed air system.
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
Manual air pressure regulators for the vertical and horizontal stresses.
THE EQUIPMENT
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
aluminum frame
locking system
step by step electric motor
Mini CPT:- 60° conical tip- cone diameter = 8 mm- external sleeve- standard rate of 20 mm/s- load cell external to the cone
THE EQUIPMENT
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
INTRODUCTION12 THE METHOD
3 HYPOTHESES
4 THE EQUIPMENT
56 RESULTS
7 CONCLUSIONS
LABORATORY TESTS
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
d50 = 0,5 mm Cu = 2 min = 1,419 kg/dm3 ; max = 1,663 kg/dm3
A6; dmax = 20.5 kN/m3; wopt=9.43% FR
A4; dmax = 18.2 kN/m3; wopt=13.2% DDA4; dmax = 19.5 kg/m3; wopt=10.8% PC
Laboratory tests5
CRUSHED SAND(Calibration material)
FINE GRAINED SOILS(Building materials)
Only the particle size fraction which pass the 2 mm sieve
dry partially
saturated
BARBARA COSANTI, PhD
Dry sand samples are reconstituted inside the CC to a given DR by pluvial deposit.
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
Fine grained soil samples are reconstituted in 5 layers at a known unit weight using static compaction (hydraulic ram) in a mold
The compaction effort, required to consolidate each layer and the sample, is registered:
FINE GRAINED SOILS
partially
saturated
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
INTRODUCTION12 THE METHOD
3 HYPOTHESES
4 THE EQUIPMENT
56 RESULTS
7 CONCLUSIONS
LABORATORY TESTS
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
dry sand
BARBARA COSANTI, PhD
σ’h = costant
TIP RESISTANCE STRESS DEPENDENCE
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
dry sand
BARBARA COSANTI, PhD
σ’v = costant
TIP RESISTANCE STRESS DEPENDENCE
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
AT A GIVEN DR VALUEh IS THE MOST INFLUENTIAL
PARAMETER ON qcLAB
TIP RESISTANCE STRESS DEPENDENCE
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
DD; PC; → d = 8092%dmax (Modified Proctor)w = wopt
Suction → evaluated according to Aubertin et al. (2003)
FR → d = 80%dmax (Modified Proctor) w= 4; 8; 12%
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
There is a clear relationship between tip resistance ‒ degree of compaction ‒ compaction energy, while, confinement pressures and suction have little effect on the tip resistance
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
FR → d = 80%dmax (Modified Proctor) w= 4; 8; 12%(wopt 10%)
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
CPT E2 FREDDANA
0
100
200
300
400
500
600
0 5 10 15 20 25
Qc ( MPa )
Z ( c
m )
CPT E2
Very high values of qc in the shallower layers of the embankments
EVAPO - TRANSPIRATION PHENOMENA (DESSICATION)
Variation of tip resistance with water content
?
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
Laboratory tests
Correlation between Ed and qc
CPTuLFWD
+
Simple prevision method for quality
control
Average qc measured within the influence depth for the LFWD (approximately 1.5 times the diameterof the loading plate = 45cm)
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
As the water content decreases, Ed value increases
BARBARA COSANTI, PhD
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
Conclusions
a correlation exists between qc and soil density that can be used to define a target tip resistance profile
DRY SANDS
PARTIALLY SATURATED FINE GRAINED SOILS
qc = f (σ’h)
qc = f COMPACTION ENERGYw
it is possible to predict the dry density from the measured qc irrespective of the boundary stresses
( )For a given soil and water content:
AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT
TIP RESISTANCE INCREASES WITH TIME BECAUSE OF DESSICATION
Thank [email protected]
