This Article Covers Various Test On Soil Performed Before Road Construction Or Pavement Design.
Test On Soil
Sub grade soil
Soil is an accumulation or deposit of earth material, derived naturally from the disintegration of rocks or decay of vegetation, that can be excavated readily with power equipment in the field or disintegrated by gentle mechanical means in the laboratory.
The desirable properties of sub grade soil as a highway material are
- Permanency of strength
- Minimum changes in volume and stability
- Good drainage
- Ease of compaction
Sub grade soil is an integral part of the road pavement structure as it provides the support to the pavement from beneath. The main function of the sub grade is to give adequate support to the pavement and for this the sub grade should possess sufficient stability under adverse climatic and loading conditions.
Therefore, it is very essential to evaluate the sub grade by conducting tests.
The tests used to evaluate the strength properties of soils may broadly divided into three groups:
- Shear tests
- Bearing tests
- Penetration tests
Shear tests usually carried out on relatively small soil samples in the laboratory. In order to find out the strength properties of soil, a number of representative samples from different locations tested. Some of the commonly known shear tests:
- Direct shear test,
- Triaxial compression test,
- Unconfined compression test.
California Bearing Ratio (CBR)
This test was developed by the California Division of Highway as a method of classifying and evaluating soil-sub grade and base course materials for flexible pavements.
Plate Bearing Test
Plate bearing test used to evaluate the support capability of sub-grades, bases and in some cases, complete pavement. Data from the tests are applicable for the design of both flexible and rigid pavements.
In plate bearing test, a compressive stress applied to the soil or pavement layer through rigid plates relatively large size and the deflections measured for various stress values.
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