P. JOHN VICTORRESEARCH OFFICER

A.P. Engineering Research Laboratories,Himayatsagar, Hyderabad –500 030.

NEED OF SOIL TESTING

Earth work (SOILS) plays a major role in almost all Civil Engineering projects such as:

● BUILDING CONSTRUCTION

● FORMATION OF EARTHEN EMBANKMENTS

● ROAD FORMATIONS

● FILTER DESIGNS

● CUTOFF TRENCHES

● CNS LAYERS, ....

Therefore, the Soil Investigations are a must to select the type of soils to be used for different types of structures / purposes.

Present wrong practices.

EARTHEN EMBANKMENTS

MAIN ZONES (FOR SOIL TESTING):

HEARTING

CASING

FILTERS

COT

TESTS ON SOILS FOR IRRIGATION PROJECTS

• Pre Construction

• During Construction

• Post Construction

TESTS FOR SPILLWAY CONSTRUCTION

• INSITU PERMEABILITY TESTS – SINGLE PACKER METHOD– DOUBLE PACKER METHOD

(TO DECIDE ABOUT THE GROUTING)

• FIELD ROCK SHEAR TEST

(TO ASCERTAIN THE BOND BETWEEN THE NATURAL ROCK AND CONCRETE)

• GEOLOGIST’S REPORT

TESTS FOR CM & CD WORKS

• COLLECTION OF UNDISTURBED SOILS

(TO COMPUTE THE SAFE BEARING CAPACITY)

• DIFFERENTIAL FREE SWELL

• PLATE LOAD TEST

TESTS ON CNS SOILS

• MECHANICAL ANALYSIS– SIEVE ANALYSIS– HYDROMETER ANALYSIS

• ATTERBERG LIMITS– LIQUID LIMIT– PLASTIC LIMIT

• SWELL PRESSURE TEST

REQUIREMENTS TO USE AS CNS SOIL

• GRAVEL ( > 2 MM ) 0 – 10%• SAND ( 2 - 0.06 MM ) 30 – 40%• SILT ( 0.06 – 0.002 MM ) 30 – 40% • CLAY ( < 0.002 MM ) 15 – 20%• LIQUID LIMIT 30 – 50%• PLASTIC LIMIT 20 – 25%• SWELL PRESSURE < 0.10 Kg/Sq.Cm.

IS 9451-1994

TESTS FOR FILTERS

• MECHANICAL ANALYSIS – SIEVE ANALYSIS – HYDROMETER ANALYSIS– GRADATION CURVE

FILTERS(IS 9429 – 1980)

Transition filters are required between impervious zones of fine grained soils, and pervious zones or drains of coarse material to prevent migration of soil grains from the former to the latter. As the direction of seepage is towards the upstream face at the time of drawdown, such filters are needed both on the Upstream and downstream side of the core.

Need of Filters:

FILTERS

a) Its voids should not permit the migration of the particles from the protected zone.

b) It should be sufficiently more pervious than the protected zone to induce a sharp reduction in hydraulic gradient.

Contd...

Requirement of a Filter:

Requirement of a Filter:

D15 of filter

D85 of protected soil< 5

D15 of filter

D15 of protected soil> 4 & < 20

D50 of filter

D50 of protected soil< 20

FILTERS

a) Horizontal Filter – 15 to 30 Cm.

b) Vertical Filter – 1.00 to 1.50 m.

Thickness of Filter:

INSITUTESTING PROCEDURES & THEIR IMPORTANCE

TYPES OF INSITU PERMEABILITY TESTS

IN ROCKY STRATA :• SINGLE PACKER METHOD • DOUBLE PACKER METHOD

IN SOILS :• JAPANESE METHOD• PUMPING IN TEST• PUMPING OUT TEST

IMPORTANCE OF PERMEABILITY DATA

• CORE LOGGING OF A BORE HOLE PROVIDES INFORMATION ON THE PHYISCAL CONDITION OF THE ROCK MASS

• WATER PERCOLATION TESTS – PERMEABILITY RESULTS OF A STRATA SUPPLEMENTS INFORMATION ON THE DRILL HOLE DATA

• WHAT CAN BE THE LOSS DUE TO FEATURES SUCH AS THESE IF STORAGE STRUCTURES CONTEMPLATED?

PERMEABILITY

• THE STATE OF WATER MOVEMENT BELOW THE SURFACE THROUGH A MEDIUM IS CALLED PERCOLATION AND THE MEASUE OF MOVEMENT CALLED PERMEABILITY

DARCY’S LAW

• THE FLOW RATE IS PROPORTIONAL TO THE CROSS SECTIONAL AREA OF A MEDIUM THROUGH WHICH THE WATER FLOWS

• FOR UNIT CONDITIONS THE EQUATION CAN BE WRITTEN ASQ= KA h/l where

K= Co-efficient of permeabilityQ= quantity of water discharge per unit area of timeA= cross sectional area through which it flowsh= hydraulic head variationl= the distance in which the head is lost

• The Eqn can be re-written as K= Q/A . L/h• Temp and viscosity although affect they are not considered because

the effect on flow of water is insignificant

WHAT IS LUGEON VALUE?

• THE UNITS ARE NORMALLY EXPRESSED IN feet/year; cm/sec; m/sec; feet/day etc.

• Another unit commonly used is Lugeon named after a French Engineer M.Lugeon who conceived carrying out water pressure tests

• One lugeon is defined as the quantity of water lost in litres/min per metre cross sectional area of bore hole at a pressure of 10 bars

• Because of adoptability water tests in river valley projects use this unit which is equivalent to 10 feet/year or 10-5 cm/sec or 10-7 metre/sec

PACKER TESTS OR PUMP IN METHOD

• SINGLE PACKER METHOD AS THE BORE HOLE PROGRESSES OR

• BY DOUBLE PACKER METHOD AFTER COMPLETION OF BOREHOLES

• EQUIPMENT REQUIRED ARE DRILLING EQUIPMENT, PRESSURE GAUGE, PUMP, WATER FEEDER LINES, DRILL ROD, PERFORATED ROD AND OTHER FITTINGS, WATER METER ETC

METHODOLOGY

• A MEASURED QUANTITY OF WATER IS PUMPED INTO THE BOREHOLE UNDER KNOWN PRESSURE FOR A UNIT LENGTH OF SECTION

• WATER LOST OBSERVED FOR 3 CONTINUOUS READINGS FOR SPECIFIC TIME DURATION.

• LUGEONS CALCULATED

PRECAUTIONS

• SATURATION OF THE TEST SECTIONS FOR A SPECIFIED PERIOD

• CALIBRATION OF PRESSURE GAUGES, WATER METRES ETC

• USE OF CLEAN WATER TO PREVENT CLOGGING OF THE FEATURES - USE OF SETTLING TANKS

• OTHERWISE PERMEABILITY CALCULATIONS CAN BE GROSSLY MISLEADING

PROCEDURES

• TESTS TO BE PERFORMED UNDER UNCASED SECTIONS AND UNGROUTED SECTIONS AND WHERE DRILLING MUD USED TO BE AVOIDED

• PRELIMINARY DRILLING DATA SUCH AS CORE LOSS, COLLAPSED SECTIONS, CHANGE IN LITHOLOGY THEREFORE CHANGE IN PERMEABILITY CHRACTERISTICS, POSSIBILITY OF PACKER GETTING STRUCK OR WIDER SECTIONS WHERE PACKER WILL NOT BE SEATED PROPERLY TO BE GATHERED

• SINGLE PACKER TEST CAN BE PERFORMED IN HOLES CASING NOT REQUIRED EVEN FOR SOFT SANDSTONE ETC OR WHERE HIGHLY FRACTURED/SHEARED SECTION OF BORE HOLE

• IN DOUBLE PACKERS, (THOUGH EFFICIENT) LEAK THROUGH THE LOWER PACKER CAN GO UNNOTICED LEADING TO ERRONEOUS RESULTS

• TEST SECTIONS IN ANY CASE SHOULD NOT BE LESS THAN FIVE TIMES THE DIAMETER OF THE BOREHOLES

• CYCLIC TESTS ARE PERFORMED TO DETERMINE WASHABILITY AND GROUTABILITY OF JOINTS

• PRESSURES TO BE APPLIED IS EITHER GOVERNED BY THE COVER OF ROCK

• OR THE FOUNDATION THAT CAN WITHSTAND WITHOUT HEAVING SUBJECT TO MAXIMUM HEAD OF THE RESERVOIR TO BE IMPOUNDED

GROUTABILITY VS PERMEABILITY

• MEDIA INDICATING LESS THAN ONE LUGEON NORMALLY COULD NOT BE GROUTED

• BETWEEN ONE TO FIVE LUGEONS USE OF APPROPRIATE PRESSURES AND DETERMINATION OF POST GROUT PERMEABILITY TESTS REQUIRED FOR CROSS CHECKING

PLATE LOAD TEST

INSITU ROCK SHEAR TEST

LABORATORY

TESTING PROCEDURES

IDENTIFICATION MECHANICAL ANALYSIS

SIEVE ANALYSIS

HYDROMETER ANALYSIS ATTERBERG’S LIMITS

LIQUID LIMIT

PLASTIC LIMIT

SHRINKAGE LIMIT CLASSIFICATION

NOTATIONS: G – S – M – C – W – P – H – I – L – O – PtGC – GW – CH – ML .......

SC–SM; GC–SC

SOIL CHARACTERISATION

SIEVE ANALYSISWhy? – To know the grain size distribution of

coarse grained soils (gravel & sand)

40 mm

25 mm

12.5 mm

4.75 mm

For gravel For Sands

2.000 mm

0.600 mm

0.425 mm

0.250 mm

0.150 mm

0.075 mm

ADD DISPERSIVE AGENT

SIEVE SETS

SIEVE SHAKER

HYDROMETER ANALYSIS

Why? – To know the grain size distribution of fine grained soils (silt & clay)

Clay Silt Sand Gravel Cobbles Boulders

Grain Size Distribution

Particle size in mm

0.002 0.075 4.75 75 300

GRAVEL

4.75 7520FINE COARSE

SAND

0.075 4.750.425 2.00

COARSEFINE MEDIUM

ATTERBERG’S LIMITS

Moisture content (%)

Vol.

Cu.Cm.

Solid Semi-Solid

Plastic Liquid

LLPLSL

CASAGRANDE’S LIQUID LIMIT DEVICE

Specific Gravity

It is the ratio of the mass of a given volume of solids to the mass of an equal volume of water at 4 o C.

DIFFERENTIAL FREE SWELL TEST

Free Swell Index testIS: 2720 part 40

Graduated glass cylinders100mlsample passing 425 micron sieve

10mg in each cylinderkerosene in one and

distilled water in another

Free Swell Index: It indicates the Expansivequalities of soil. It gives the amount of volume

increase of soil on coming in contact with water

FSI in %expansiveness

< 20 low

20-35 moderate35-50 high> 50 very high

PROCTOR’S COMPACTION TEST

Why? – To find out the Maximum Dry Density (MDD) and Optimum Moisture Content (OMC) of a soil under a particular compactive effort.

MOISTURE CONTENT (%)

Dry Density (gm/cc)

Heavy compaction

Light compaction

(5, 25, 45, 4.9)

(3, 25, 31, 2.6)

PROCTOR’S COMPACTION APPARATUS

Permeability

Chemical Analysis

DIRECT SHEAR TEST

SET UP FOR

TRIAXIAL COMPRESSION TEST

1.5“ DIA.

3.0“ HEIGHT

(–) 4.75 mm SOIL

1.25 mm/min

Quality Control

> 75 mm size particles are to be rejected

Minimum 98% MDD must be achieved

Permeability Characteristics are to be checked

Embankment is to be checked whether same borrow soils are used or not.

OMC is to be checked.Dry of OMC leads to cracksWet of OMC leads to Pore Pressures

Distance of borrow from Dam

(more about) Proctor’s Compaction

Stones > 75 mm should be avoided.

Compaction is the most important property.

Because – It increases Density;It increases Shear Strength;It decreases Permeability;It decreases Compressibility.

Tested, Designated Soil must be used for various zones.

(more about) Proctor’s Compaction

Slopes: 60 Cm extra for later trimming.

Method of Compaction affects the results.

Why? – If different type of Soil is used, same MDD can be achieved with coarser borrow but classification varies. Result is – Seepage will be affected.

WHY FDD > 100% MDD?

• EXCESS COMPACTION

• DESIGNATED SOIL NOT USED

• DEFECTIVE UD SAMPLE COLLECTION

Frequency Of TestingTest Frequency IS code

Mechanical Analysis

One test per day for every 3000 Cu.M.

2720 – P IV

Atterberg’s Limits

One test per day 2720 – P V

FDD – FMC One test for every 1500 Cu.M. and atleast one test in each layer laid on embankment

2720 – P XXVIII

2720 – P XXIX

2720 – P XXXIII

Specific Gravity

One test per day 2720 – P III

Insitu Permeability

One test in every 3m of embankment or for 20000 Cu.M.

2720 – P XVII

Frequency Of Testing

Test Frequency IS codeTriaxial Shear

One test in 1 week or every 3 m of embankment or for 20000 Cu.M.

2720 – P XII

Consolidation One set of 3 samples in every 6 m height of embankment or for 30000 Cu.M. or once in ten days

2720 – P XV

Proctor’s Compaction

One test per day for individual borrow area

2720 – P VII

Frequency Of Testing (Filters)

Test Frequency IS codeMechanical Analysis

One test for every 200 Cu.M. of Filter (Sand).One test for every 200 Cu.M. of Filter (Aggregate)

2385 – P I

Clay lumps and Organic impurities

One test for every 200 Cu.M. of Filter (Sand).One test for every 200 Cu.M. of Filter (Aggregate)

2386 – P II

Note: The actual frequencies shall be determined by the Engineer – In – charge to suit the nature of work.