SOIL INVESTIGATION STUDIES

We takeup investigation to ascertain the nature and properties of soils available at different locations of site at various depths, safe bearing capacity and settlements of soil.

The work carried under soil investigation includes setting out, field investigation, laboratory testing and submission of soil investigation reports incorporating the observations made during the field investigation and the results of laboratory tests, analysis of all results foundation recommendation with calculations and other related information along with necessary charts, curves and drawings.

The field investigation consists of and/or drilling including penetration into hard rock if met during boring by at least one metre, standard penetration tests, electrical resistivity test and collection of disturbed and undisturbed soil and rock samples, excavation of trial pits, collection of water samples and conducting necessary laboratory tests at a recognized and approved soil laboratory.

Boring

Boring is done generally in accordance with IS:1892, employing mechanically operated equipment. Boreholes of nominal 150mm diameter minimum will be sunk employing shell and auger equipment or other duly approved method. The size of the drill holes will be normally NX(73mm), but may be reduced to BX (60mm) depending on strata conditions.

Drilling in rock and collection of rock core samples are in accordance with IS:6962,IS:4464 and IS:10208. Core drilling observations are in accordance with IS:5313.

Boreholes are taken down to a layer at which N value is greater than 50.However if continuous hard rock is encountered during boring ,drilling is continued for a depth of one metre into hard rock before termination of boring.

• Standard Penetration Test

Standard penetration tests are carried out at intervals of 1.5 meters or at every change of strata whichever is earlier in Accordance with IS: 2131.The intervals are increased to 3m if in between vane shear or cone penetration test is performed.

• Cyclic Plate Load test

Cyclic plate load test is carried out in accordance with IS: 5249.The plate will be located at depth of 3.0 m in a pit excavated as given in IS: 1888.

The loading is applied on the test plate gradually by reaction loading taking care to avoid impact, fluctuation, tilting of plate or eccentricity, so as to reach the soil as uniformly distributed static load. The load is maintained constant throughout for a period till no further settlement occurs or the rate of settlement becomes negligible.

The loading is increased in increments of 5 tons per square metre until the total settlement of the plate is 25mm or the soil under the plate fails whichever occurs earlier. Settlement of the plate is recorded by dial gauges of minimum accuracy of 0.02mm fixed at diametrically opposite ends as per IS:1888.

The entire load is removed quickly but gradually and the plate is Allowed to rebound when no further rebound occurs or the rate of rebound becomes negligible the reading of the dial gauges are again noted.

The cycles of loading, unloading is continued till the estimated ultimate load has been reached, the final values of dial gauges readings, being noted each time. The magnitude of the load increment will be such that the ultimate load is reached in 5 to 6 increments.

From the data obtained during cyclic plate load test, the elastic rebound of the plate corresponding to each intensity of loading is plotted. The dynamic properties of soil are furnished along detailed calculation and plots.

• Vane Shear Test

If clayey layer is found in borehole/ trial pits, vane shear test isl carried out as per IS:4434

• Trial Pits

Trial pits are done as per IS:4453 and IS:1892 by open excavation in order to collect samples and determine the nature and characteristic of soil.

The base of pit are minimum 1.5x1.5 m size and 4.0M depth in all soils

After completion of all works the trial pits are backfilled and compacted as directed by the employer or his representative.

• In situ California Bearing Ratio Tests

In situ tests to determine CBR values of existing materials at different clauses of IS:2720(part 31) at different locations along the proposed road alignment. The tentative locations of CDR tests are indicated in Drawing No Results of the tests along with suitable recommendations will be included in the investigation report.

The scope of work alsol include excavation of test pits upto the test levels in all types of fill/soil and soft rock, if any supplying and installation of all equipment, setting up and carrying out all the test evaluation of tests results, working out insitu CBR value of fill/soil and soft rock, if any at specified levels and reporting the results as specified.

All test data, charts, curves etc along with calculation for determination of insitu CBR value are given.

• Electrical resistivity of soil

Electrical resistivity of soil is measured by wenners four electrode method.. General description with regard to the type of soil, grain size distribution of the soil at test location are described in the test result.

• LABORATORY TESTS

Samples obtained during field investigation are of the particular type of subsoil and rock and forwarded to soil testing laboratory for performing the tests.