# GATE Questions & Answers of One Dimensional Consolidation

## What is the Weightage of One Dimensional Consolidation in GATE Exam?

Total 16 Questions have been asked from One Dimensional Consolidation topic of Soil Mechanics subject in previous GATE papers. Average marks 1.75.

The void ratio of a soil is 0.55 at an effective normal stress of 140 kPa. The compression index of the soil is 0.25. In order to reduce the void ratio to 0.4, an increase in the magnitude of effective normal stress (in kPa, up to one decimal place) should be ______

A 3 m thick clay layer is subjected to an intital uniform pore pressure of 145 kPa as shown in the figure.

For the given ground conditions, the time (in days , rounded to the nearest integer) required for 90% consolidation would be ___________

The results of a consolidation test on an undisturbed soil, sampled at a depth of 10 m below the ground level are as follows:

 Saturated unit weight : 16 kN/m3 Pre-consolidation pressure : 90 kPa

The water table was encountered at the ground level. Assuming the unit weight of water as 10 kN/m3, the over-consolidation ratio of the soil is

A water tank is to be constructed on the soil deposit shown in the figure below. A circular footing of diameter 3 m and depth of embedment 1 m has been designed to support the tank. The total vertical load to be taken by the footing is 1500 kN. Assume the unit weight of water as 10 kN/m3 and the load dispersion pattern as 2V:1H. The expected settlement of the tank due to primary consolidation of the clay layer is ______mm.

A 20 m thick clay layer is sandwiched between a silty sand layer and a gravelly sand layer. The layer experiences 30 mm settlement in 2 years.

Given:

Where Tv is the time factor and U is the degree of consolidation in %.
If the coefficient of consolidation of the layer is 0.003 cm2/s, the deposit will experience a total of 50 mm settlement in the next ________ years.

A 4 m thick layer of normally consolidated clay has an average void ratio of 1.30. Its compression index is 0.6 and coefficient of consolidation is 1 m2/yr. If the increase in vertical pressure due to foundation load on the clay layer is equal to the existing effective overburden pressure, the change in the thickness of the clay layer is_______mm.

The following data are given for the laboratory sample.

If thickness of the clay specimen is 25 mm, the value of coefficient of volume compressibility is ___________ ×10-4 m2/kN

The contact pressure for a rigid footing resting on clay at the centre and the edges are respectively

A layer of normally consolidated, saturated silty clay of 1 m thickness is subjected to one dimensional consolidation under a pressure increment of 20 kPa. The properties of the soil are: specific gravity = 2.7, natural moisture content = 45%, compression index = 0.45, and recompression index = 0.05. The initial average effective stress within the layer is 100 kPa. Assuming Terzaghi’s theory to be applicable, the primary consolidation settlement (rounded off to the nearest mm) is

Identical surcharge are placed at ground surface at sites X and Y, with soil conditions shown alongside and water table at ground surface. The silty clay layers at X and Y are identical. The thin sand layer at Y is continuous and free-draining with a very larger discharge capacity. If primary consolidation at X is estimated to complete in 36 months, what would be the corresponding time for completion of primary consolidation at Y?

The e-log p curve shown in the figure is representative of

A saturated undisturbed sample from a clay strata has moisture content of 22.22% and specific weight of 2.7. Assuming $\gamma$w = 10 kN/m3, the void ratio and the saturated unit weight of the clay, respectively are

Using the properties of the clay layer derived from the above question, the consolidation settlement of the same clay layer under a square footing (neglecting its self weight) with additional data shown in the figure below (assume the stress distribution as 1H:2V from the edge of the footing and $\gamma$w = 10 kN/m3) is

A saturated clay stratum draining both at the top and bottom undergoes 50 percent consolidation in 16 years under an applied load. If an additional drainage layer were present at the middle of the clay stratum, 50 percent consolidation would occur in

The ground conditions at a site are as shown in the figure. The water table at the site which was initially at a depth of 5m below the ground level got permanently lowered to a depth of 15m below the ground level due to pumping of water over a few years. Assume the following data

 i. unit weight of water = 10kN/m3 ii. unit weight of sand above water table = 18kN/m3 iii. unit weight of sand and clay below the water table = 20kN/m3 iv. coefficient of volume compressibility = 0.25m2/MN

What is the change in the effective stress in kN/m2 at mid-depth of the clay layer due to the lowering of the water table?