Geotechnical Engineering

c. A vane apparatus 10cm long and 8cm in diameter was passed into the soft clay, at the bottom of borehole test. A torque of 45N-m was applied at which failure took place Subsequently vane instrument rotated rapidly, so as to get remolded soil sample. This remolded soil was sheared at a torque of 18 N-m. Then calculate sensitivity of clayey soil. 

Distinguish between Coulomb's earth pressure theory and Rankine's earth pressure theory.

a Critically discuss limitations of direct shear test. 

b. Explain Vane shear test with neat sketch along with relations.

Describe standard penetration test as per IS:2131 guidelines. How to apply corrections to observed SPT-values? 

Estimate the grand water table, given the following data. Depth upto which water is boiled out 18 meters. Water rise on I^st day = 0.95m, IIday = 0.86m and III day = 0.78m. Use Hvorselev's method.

Explain equivalent point load method of determining  - at any point with in loaded area.

Point loads 64kN, 15kN and 21kN, 1.5m apart in a straight line at the surface of soil mass.Calculate the resultant stress produced by these loads on a horizontal plane one meter below the surface at points vertically below the loads and also half way (mid point) between them. The vertical pressure  du to point load Q is given by Boussinesq's  equation The value of I_B are as follows: 

Sketch the curve showing distribution of these resultant stresses at that level.

Explain with a neat sketch a method of locating the phreatic line in a homogeneous earth dam with horizontal filter. 

List the applications of flow net. Discuss about the validate of Darcy's law in determining quantity of seepage. 

An earthen dam is built on a impervious foundation with a horizontal filter under the downstream slope. The horizontal and vertical permeability of the soil material in the dam are respectively 4 x 10^-5 m/sec and 1 x 10^-5 m/sec. Full reservoir level is 20 meters above downstream filter. Flow net consists of 4 flow channels and 15 equipotential drops. Estimate seepage loss per meter length of the dam. 

c. A layer of soft clay is om thick and dies under newly constructed building. The weight of sand overlying the clayey layer produces a pressure of 260 kN/m²  and this new construction increases the pressure by 100kN/m² If the compression index is 0.5, compute settlement of soil layer given water content 40% and G=2.65. 

Describe Rebhann's graphical method of finding active earth pressure on a retaining wall.

Obtain an expression for factor against sliding in C- soil by the method of slices. Explain determination of factor of safety by method of slices method. 

An embankment is inclined at an angle 38º and its height is 20 meters. The angle of shearing  resistance is 15º and the cohesion intercept is 50 kN/m². The unit weight of Boy is 16.5 kN/m'. Find the factor of safety with respect to cohesion. Consider Taylor stability number = 0.08.

List the assumptions of Terzaghi's bearing capacity equation.

Calculate the ultimate bearing capacity of a 2 meter wide square footmg resting on a ground surface of a sand deposit with the following properties: i) Unit weight is 18.6 kN/m³; ii) Anglo of internal friction = 38^o. Also calculate ultimate bearing capacity of same footing when the footing is placed at depth of im below the ground surface. Take N_q = 41.4, N_r = 42.2 for  =38º Adopt Terzaghi's equation. Also calculate percentage increase in bearing capacity with increase in depth from surface to 1 meter from natural ground level.

Discuss about the components of settlement.

The soft normally consolidated clay layer is 18 meter thick. The natural water content is 45%. The saturated unit weight is 18 kN/m³. The grain specific gravity is 2.70 and the liquid limit = 63%. The vertical stress increment at the centre of the layer due to the foundation load is 9kN/m". The ground water level is at the surface of the clay layer. Determine the consolidation settlement of the foundation.

List and explain the classification of pile foundation base on function and material.

b. Explain Quick - sand phenomena and list its importance during construction.

b. Derive the relation,  with usual notations.

c. In an earthen embankment under construction, the bulk unit weight is 16.5kN/m³ at water content 11%. If the water content has to be increased to 50%, compute the quantity of water to be added per cubic meter of soil. Assume no change in void ratio. Also determine 'e' at this water content taking G = 2.65. 

 a. Define relative density of sand and list its importance in geotechnical engineering.

b. Describe consistency of soil. List and define consistency limits. 

c. The following results are obtained by conducting liquid limit test on clayey soil in the laboratory :

 Plot flow curve. Determine Liquid limit, Toughness index. Assume plastic limit=20%.

a. Explain with the help of typical particle size distribution curve, well graded, poorly graded and gap graded soil.

b. With the neat sketch, explain structure of clay minerals.

c. Following results are obtained from the laboratory tests conducted on two soil samples:

Show the positions of these soils on plasticity chart and classify as per I.S. system.

a. Derive the relation between co-efficient of permeability and percolation with usual notations.

a. Critically define the terms void ratio, porosity and water content with phase diagram.

C. A falling head permeater accommodates a soil sample of 6cm length and 500cm² in area.The permeability of sample is expected to be 1 x 10^-6 cm/sec. Head of water in the standpipe falls from 30cm to 10cm in 40 minutes. Determine the size of the stand pipe which should be used. 

a. Explain sensitivity and thixotropy of clayey soil.

b. List the factors affecting shear strength of soil.

c. A direct shear test results are obtained as follows:

Determine shear parameters graphically. Also draw Mohr's circle corresponding to second test result and report major and minor principal stresses. 

a List the factors affecting compaction of soil and explain any 2 in detail.

b. List and explain various types of field compaction equipments.

c. The results of standard compaction test conducted in the laboratory are tabulated as follows:

Find MDD and OMC with usual notations by plotting compaction curve. Also draw ZAVD - line assuming G =2.65. 

a. State the assumptions of one-dimensional Terzaghi's theory of consolidation. Also write standard / general differential one-dimensional consolidation equation with usual notation. 

b. Explain with neat sketch, determination of co-efficient of consolidation by square root of time fitting method.