study of systems of couples in space , problems related to centroids in of composite area

 

analysis of equilibrium of concurrent coplanar and non concurrent coplanar coplanar force system

 

Problems involved with friction , analysis of simple truss by method of joints and sections

 

RADIUS OF GYRATION

 

MOMENT OF FORCE

 

Determination of Moisture Content of Soil

 

Tri-axial compression test in cohesion-less soil (Demonstration Only)

 AIM: 

To determine the undrained shear strength of the cohesive soil using vane shear.

THEORY: 

The strength test more commonly used in a research laboratory today is the triaxial

compression test, first introduced in the U.S.A. by A. Casagrande and Karl Terzaghi in

1936 – 37. The soil specimen, cylindrical in shape, is subjected to direct stresses acting

in three mututally perpendicular directions. In the common solid cylindrical specimen

test, the major principal stress σ1 is applied in the vertical direction, and the other two

principal stresses σ2 and σ3 σ2 σ3) are applied in the horizontal direction by the fluid

pressure round the specimen 

APPARATUS REQUIRED:

KNOWLEDGE OF EQUIPMENT

1) A constant rate of strain compression machine of which the following is a brief 

description of one is in common use.

a) A loading frame in which the load is applied by a yoke acting through an elastic 

dynamometer, more commonly called a proving ring which used to measure the load.

The frame is operated at a constant rate by a geared screw jack. It is preferable for the

machine to be motor driven, by a small electric motor. 

b) A hydraulic pressure apparatus including an air compressor and water reservoir in

which air under pressure acting on the water raises it to the required pressure, together

with the necessary control valves and pressure dials. 

2) A triaxial cell to take 3.8 cm dia and 7.6 cm long samples, in which the sample can

be subjected to an all round hydrostatic pressure, together with a vertical compression

load acting through a piston. The vertical load from the piston acts on a pressure cap.

The cell is usually designed with a nonferrous metal top and base connected by tension

rods and with walls formed of perspex. 

Apparatus for preparation of the sample:

1) 3.8 cm (1.5 inch) internal diameter 12.5 cm (5 inches) long sample tubes.

2) Rubber ring.

3) An open ended cylindrical section former, 3.8 cm inside dia, fitted with a small 

rubber tube in its side.

4) Stop clock. 

Direct shear test in cohesion-less soil

 AIM:

To determine the shearing strength of the soil using the direct shear apparatus. 

THEORY:

Shear strength of a soil is its maximum resistance to shearing stresses. It is equal to the 

shear stress at failure on the failure plane. Shear strength is composed of (i) internal

frictions, which is the resistance due to the friction between the individual particles at their

contact points and inter locking of particles. (ii) cohesion which is the resistance due to

inter particle forces which tend to hold the particles together in a soil mass. Coulomb has

represented the shear strength of the soil by the equation : 

APPARATUS REQUIRED:

1) Direct shear box apparatus

2) Loading frame (motor attached).

3) Dial gauge.

4) Proving ring. 

5) Tamper.

6) Straight edge.

7) Balance to weigh upto 200 mg.

8) Aluminum container.

9) Spatula. 

PROCEDURE:

• Check the inner dimension of the soil container. 

• Put the parts of the soil container together.

• Calculate the volume of the container. Weigh the container.

• Place the soil in smooth layers (approximately 10 mm thick). If a dense sample is 

desired tamp the soil.

• Weigh the soil container, the difference of these two is the weight of the soil. 

Calculate the density of the soil.

• Make the surface of the soil plane.

• Put the upper grating on stone and loading block on top of soil.

• Measure the thickness of soil specimen. 

• Apply the desired normal load. 

Determination of Liquid Limit and Plastic Limit

 AIM 

To determine the liquid limit and plastic limit of the given soil sample

THEORY AND APPLICATION 

Liquid limit is significant to know the stress history and general properties of the soil

met with construction. From the results of liquid limit the compression index may be

estimated. The compression index value will help us in settlement analysis. If the

natural moisture content of soil is closer to liquid limit, the soil can be considered as

soft if the moisture content is lesser than liquids limit, the soil can be considered as

soft if the moisture content is lesser than liquid limit. The soil is brittle and stiffer. The

liquid limit is the moisture content at which the groove, formed by a standard tool into

the sample of soil taken in the standard cup, closes for 10 mm on being given 25

blows in a standard manner. At this limit the soil possess low shear strength. 

The moisture content expressed in percentage at which the soil has the smallest

plasticity is called the plastic limit. Just after plastic limit the soil displays the

properties of a semi solid. For determination purposes the plastic limit it is defined as

the water content at which a soil just begins to crumble when rolled into a thread of

3mm in diameter. The values of liquid limit and plastic limit are directly used for

classifying the fine grained soils. Once the soil is classified it helps in understanding

the behaviour of soils and selecting the suitable method of design construction and

maintenance of the structures made-up or and resting on soils. 

APPARATUS REQUIRED: 

1) Measuring balance 

2) Liquid limit device (Casagrandes) 

3) Grooving tool 

4) 425 micron sieve 

5) Glass plate 

6) Spatula