# Geotech Engineering Calculators Calculators for Test of Soil

## Determination of Water Content for Soil

In almost all soil tests natural moisture content of the soil is to be determined. The knowledge of the natural moisture content is essential in all studies of soil mechanics. To sight a few, natural moisture content is used in determining the index properties of the Soil. The natural moisture content will give an idea of the state of soil in the field.

## Free Swell Index of Soil

Sieve analysis deals with the method for the determination of grain size distribution in soils. An analysis of this kind express quantitatively the proportions by mass of the various sizes of particles present in the soil. In a soil, the gravel, sand, silt and clay fractions are recognize as containing particles of decreasing magnitude.

## Vane Shear Test

vane shear test for the measurement of shear strength of cohesive soils is useful for soils of low shear strength of less than about 0'5 kgf/cml. This test gives the undrained strength of the soil and the undisturbed and rernoulded strengths obtained are used for evaluating the sensitivity of the soil.

With a view to establish uniform procedures for determination of different characteristics of soils and also for facilitating comparative studies of the results, an Indian Standard on methods of test for soils (IS : 2720) is being published in various parts. This part describes the method for determination of coefficient of permeability of granular soils by a constant head method and under conditions of laminar flow of water. The knowledge of this property is essential in a solution of problems involving de-watering, yield of water bearing strata, seepage through earth dams, etc. A reliable determination of permeability can be made only when the conditions for the validity of Darcy Law are fulfilled, that is, when the flow is steady and laminar and the soil is saturated and the rate of flow is proportional to the hydraulic gradient. Part 17 of this standard covers the general method but this part covers the disturbed granular materials containing less than 10 percent soil passing through 75 micron IS Sieve which are used in embankments, earth dams base courses, etc, and thus has different test apparatus. This standard was first published in 1975. Based on the experience gained in conducting this test in the past 13 years, the procedures have been updated and figures have been modified. The opportunity has also been taken to make references of latest Indian Standards which have been published or revised in this period.

## Determination of Specific Gravity

Specific gravity G is defined as the ratio of the weight of a given volume of soil solids to the weight of a equal volume of distilled water.

It deals with the method of test for determination of specific gravity of soils which finds application in finding out the degree of saturation and unit weight of moist soils. The unit weights are needed in pressure, settlement and stability problems in soil engineering.

## Liquid Limit of Soil

A liquid limit of soil is the moisture content expressed as a percentage of the weight of over-dried soil, at which soil changes from a plastic to a liquid state.

Why to test Liquid limit of Soil?

• The liquid and plastic limits of soils are both dependent on the amount and type of clay in a soil and form the basis for the soil classification system for cohesive soils based on the plasticity tests.
• Besides their use for identification, the plasticity tests give information concerning the cohesion properties of soil and the amount of capillary water which it can hold.
• They are also used directly in specifications for controlling soil for use in fill.
• These index properties of soil have also been related to various other properties of the soil.

## Direct Shear Test

A liquid limit of soil is the moisture content expressed as a percentage of the weight of over-dried soil, at which soil changes from a plastic to a liquid state.

## IN-SITU Density By Core Cutter Method

This Indian Standard (Part XXIX) (First Revision) was adopted by the Indian Standards Institution on 22 September 1975, after the draft finalized by the SoiI Engineering Sectional Committee had been approved by the Civil Engineering Division Council.

## Sieve Analysis of Soil (Dry Method)

Sieve analysis deals with the method for the determination of grain size distribution in soils. An analysis of this kind express quantitatively the proportions by mass of the various sizes of particles present in the soil. In a soil, the gravel, sand, silt and clay fractions are recognize as containing particles of decreasing magnitude.

The results of grain size analysis are widely used in soil classification. The data obtained from grain size distribution curves is used in the design of filters for earth dams to determine the suitability of soils for road construction.

For a falling head test arrangement, the specimen shall be connected through the top inlet to selected stand-pipe. The bottom outlet shall be opened and thetime interval required for the water level to fall from a known initial head to a known final head as measured above the centre of the outlet shall be recorded. The stand-pipe shall be refilled with water and the test repeated till three successive observations give nearly same time interval; the time intervals being recorded for the drop in head from the same initial to final values, as in the first determination. Alternatively, after selecting the suitable initial and final heads hl and hi respectively, time intervals shall be noted for the head to fall from h1 to $\sqrt{{h}_{1}{h}_{2}}$ and similarly from $\sqrt{{h}_{1}{h}_{2}}$ to h2. The time intervals should be the same; otherwise the observation shall be repeated after refilling the stand-pipe.