soil investigation procedure

RDF POWER PROJECT HYDERABAD.

TECHNICAL SPECIFICATION FOR

SOIL INVESTIGATION DOC. NO: ENG-2645-600-001

CONSULTANT: MATRIX SOLUTIONS PVT LTD, BANGALORE - INDIA

REV

DATE

PREPARED

CHECKED

APPROVED

00 28-03-2009 V.M.P KJN

GN

PROJECT: 11 MW RDF BASED POWER PLANT, HYDERABAD.

10 MW RDF BASED POWER PLANT AT HYDERABAD, INDIA TECHNICAL SPECIFICATION FOR SOIL INVESTIGATION

MATRIX SOLUTIONS PVT LTD, BANGALORE

CONTENTS

1.0 INTENT

2.0 SCOPE OF WORK

3.0 SUBMISSION OF TEST REPORTS

4.0 GENERAL

5.0 PLATE LOAD TEST

6.0 ELECTRICAL RESISTIVITY TEST



1.0 INTENT The intent of this specification is for carrying out Soil investigation at site which is essential to

design economical and adequate foundations for the heavy and small equipment and structures of

the Power Plant. The following types of foundations are normally adopted for Design and

Execution.

1. Individual /Raft Foundation for Buildings and Power house structures.

2. Block Foundations for Equipments

3. Framed foundation with solid mat for TG.

4. Circular Solid raft for Chimney Foundation.

5. Footings for foundations for tall structures like Junction Towers, Conveyor system etc,

Soil Investigation shall be conducted by keeping in view of above, and shall be in accordance with

the following specifications.

2.0 SCOPE OF WORK 2.1 Field Investigations: 2.1.1 Drilling of bore-holes (BH) shall be done wherever specified as per IS 1892-1979.

2.1.2 The Standard Penetration Tests (SPT) shall be performed in accordance with Indian

Standards and the following details registered for carrying out SPT shall be furnished by

the agency.



2.1.2.1 Bore hole identification number.

2.1.2.2 Type and diameter of drilling.

2.1.2.3 Depth at which SPT shall be conducted as per IS 2131-1981.

2.1.2.4 Penetration record and N value.

2.1.2.5 Water table information.

2.1.2.6 Description, identification and depth of different strata encountered.

2.1.2.7 Core recovery data, level of bore hole termination etc.,

2.1.3 Soil Electrical resistivity test shall be performed in accordance with IS :3043.

2.1.4 Cyclic plate load test shall be carried out as per IS 1888, using reaction loading for loading

the test plates. Using the test results, the following shall be evaluated by suitable graphs.

• Elastic modulus and

• Co-efficient of uniform elastic compression (Co-efficient of sub grade reaction)

2.1.5 The depth of bore may be restricted on encountering hard soil/rock or at a depth where ‘N’

value is greater than 50 whichever occurs earlier. The boring shall be done beyond hard

soil/rock and core samples of about 1.5m long may be collected for further laboratory studies

to establish properties of rock.



2.1.6 Collection of disturbed and undisturbed soil samples, rock cores for conducting laboratory

tests.

2.1.7 Trial pits as shown shall be excavated at least up to 3.0 m depth as per relevant IS:code and

undisturbed soil samples shall be collected for laboratory testing. Soil stratification shall be

co-related with bore holes.

2.2 Laboratory testing:

Conducting all the following laboratory tests on the soil and rock samples collected from the

Site.

2.2.1 Tests to be conducted on representative disturbed samples as per following Indian Standards.

2.2.1.1 Moisture content :As per IS :2720(Part II)

2.2.1.2 Specific Gravity :As per IS :2720(Part III)

2.2.1.3 Grain Size Analysis :As per IS :2720(Part IV)

2.2.1.4 Atterberg’s Limits :As per IS :2720(Part V& VI)

2.2.1.5 PH value, Sulphate Content & :As per IS :2720(Part XXVI& XXVII)

Chloride Content

2.2.1.6 California Bearing Ratio Test :As per IS :2720(Part XVI)Ratio Test

2.2.1.7 Total soluble salt content :As per relevant IS codes.

2.2.1.8 Organic content :As per relevant IS codes.



2.2.2 Tests to be conducted on representative undisturbed samples as per following Indian Standards.

2.2.2.1 Consolidation test :As per IS :2720 (Part XV)

2.2.2.2 Undrained triaxial shear test :As per IS :2720(Part XII)

2.2.2.3 Unconfined compression test :As per IS :2720(Part X)

2.2.2.4 Co-efficient of permeability :As per relevant IS codes.

2.2.3 Tests to be conducted on rock samples as per following Indian Standards. 2.2.3.1 Compressive Strength :As per IS :9143

2.2.3.2 Moisture absorption :As per IS :1124

2.2.3.3 Density & Specific Gravity :As per IS :1122

2.2.3.4 Modulus of Elasticity :As per IS :9221

2.2.4 Tests to be conducted on underground water samples 2.2.4.1 pH value

2.2.4.2 Dissolved salts

2.2.4.3 Sulphate and Chloride content

All the above Tests 2.1 &2.2 shall be carried out in accordance with the relevant prevailing

Indian Standards of latest editions. All measurements shall be in the SI system.

3.0 SUBMISSION OF TEST REPORTS Reports covering the detailed test results for Field and Laboratory tests shall be submitted

covering the following.

1. Appraisal of the data and analysis of the estimated bearing capacities, settlement behavior,

swelling potential of foundations for the different strata existing at different locations.



2. Recommendations regarding the type of foundations to be provided for different structures

based on range of loading.

3. Recommendations of allowable bearing capacities/ Safe bearing capacities (SBC) at

different levels and at different locations.

4. Any special recommendations regarding equipment foundations.

5. Recommendations regarding filling, utilization of fill material, excavated at site.

6. Level of water table.

7. Relevant cross-sectional drawings of soil profile.

8. Bore hole logs, graphs, charts etc.

9. Recommendations for protection of foundations against aggressive action of soil and

underground water, if found from the laboratory tests on soil and water.

4.0 GENERAL

4.1 Site map for soil investigation shall be referred for location of various tests.

4.2 The investigator shall arrange for all necessary labour, tools and tackles, shoring materials,

equipment and instruments necessary for carrying out detailed soil investigation work.

5.0 PROCEDURE TO BE FOLLOWED FOR CONDUCTING THE PLATE LOAD TEST(PLT)

The cyclic plate load is conducted to estimate the SAFE BEARING CAPACITY of the SOIL (SBC).

The test shall be conducted as per IS :1888 and IS :3043

APPARATUS REQUIRED:-

Loading platform truss of sufficient size and properly designed members is to be made so as to

take the load reaction for conducting the test

Hydraulic jack of required capacity with properly calibrated load measuring device, pressure gauge

or proving ring can be used.



Square bearing plate made up of mild steel 300mm with thickness 25mm, sand bags.

Procedure.

Test Pit: -

• The pit is to be made up to the foundation level, having width equal to five times the test

plate,

• The test area shall be initially dressed up so that the test surface is plane without any

undulations for proper seating of the plate.

Dead Load:- The dead load of all equipment used, such as steel plate, loading column, hydraulic jack,

proving ring etc should be recorded prior to the application of load increment.

Test Arrangement Test plate shall be placed over a fine sand layer of max thickness 5mm. The hydraulic jack shall

be placed centrally over the plate with loading column in between the jack and reaction beams so

as to transfer the load to the plate. A ball and socket arrangement shall be inserted to keep the

direction of loading vertical throughout the test. The loading platform should be supported by

suitable means at least 2.5m from the test area with a height of 1m or more above the bottom of

the pit to provide sufficient working space. No support of loading platform should be located within

a distance of 3.5 times the size of test plate from its centre.

The platform shall be made up of jacking girders and secondary girders and they are made up of

beams of 300mm size (7 no’s). The over all weight shall be of minimum two times the expected

load taken

A minimum seating pressure of 70kg/cm2 should be applied and removed before starting the load

test



Load Increments Apply the load to soil in cumulative equal increments upto1kg/cm2 or one fifth the estimated

ultimate bearing capacity, which ever is less. The load is applied without impact, fluctuation or

eccentricity and in case of hydraulic jack load is measured over the pressure gauge, attached to

the pumping unit kept over the pit, away from the testing plate through extending pressure pipes.

Settlement Observation:- Settlement shall be observed for each increment of load after an interval of 1, 2, 2.5, 4, 6.25,9,16

and 25 min and thereafter at hourly to the nearest .02mm./min

If the soil is clayey, the ‘time settlement ‘curve shall be plotted at each load stage and load shall be

increased to the next stage either when the curve indicates that the settlement has exceeded 70 to

80 percent of the probable ultimate settlement at that stage or at the end of 24 hour period.

If the soil other than clayey, each load increment shall be kept for not less then one hour or up to a

time when the rate of settlement gets appreciably reduced to a value of .02mm./min. the next

increment of load shall then be applied and the observations repeated.

The test shall be continued till a settlement of 25mm under normal circumstances or 50mm in

special cases such as dense gravel.

If settlement does not reach 25mm, the test shall be continued to at least two times the estimated

design pressure. If needed, rebound observation may be taken while releasing the load.



6.0 PROCEDURE TO BE FOLLOWED FOR CONDUCTING THE ELECTRICAL RESISTIVITY TEST (ERT):- Objective

Electrical resistivity test was conducted to determine the Electrical

resistivity of the ground for the power plant area.

Electrical Resistivity: This electrical resistivity method is based on the measurement and

recording of charges in the mean resistivity or specific resistance of varies

locations in the site. The flow of current through a soil is mainly due to

electrolytic action and therefore depends on the concentration and

composition.

Results and discussion on the electrical resistivity test

WENNER’S four-electrode method is adopted to conduct the test at given

location in the project site. The test was conducted by driving four electrodes

(metal spikes) into the ground along straight line at equal distances. On

pressing the “Test” switch available in the meter, the resistance value is

displayed in the meter, which is recorded for calculation purpose. The same

procedure is carried out for different spacing of 2m, 4m, 6m, 8m and 10.0m

between the electrodes. During the process, a direct voltage of known

magnitude is imposed between the two outlet electrodes, thereby producing

an electric field within the soil.

Earth resistivity is calculated by using the formula, P = 2 x π x D x R

Where P is the resistivity in ohm-meter

D is the distance between electrodes in meters

R is the resistance value recorded during the tests in ohms



The results of the tests conducted in various locations are given Test No: ERT NO.1 Location: AUXILARY TRANSFORMER

Electrode

Spacing 2m 4m 6m 8m 10m Directions

Initial reading

Final reading

Resistivity P (ohm-m)

North

side

Initial reading

Final reading


South

Side

Initial reading

Final reading


East Side

Initial reading

Final reading


West

Side



Test No: ERT NO.2 Location: POWER HOUSE

Electrode

Spacing 2m 4m 6m 8m 10m Direction

Initial reading

Final reading


North side

Initial reading

Final reading


South

Side

Initial reading

Final reading


East Side

Initial reading

Final reading


West Side



Test No: ERT NO.3 Location: SWITCH YARD

Electrode

Spacing 2m 4m 6m 8m 10m Direction

Initial reading

Final reading


North side

Initial reading

Final reading


South

Side

Initial reading

Final reading


East Side

Initial reading

Final reading


West Side

soil investigation procedure

Documents

matrix solutions pvt

india technical specification

undisturbed soil samples

hydraulic jack

pressure gauge

electrical resistivity

test area

proving ring