List of top Geotechnical Engineering Questions on Deep foundations asked in GATE CE

Information related to foundation design is provided in table below.
Column 1Column 2
(I) Converse-Labarre formula(P) Pile capacity from dynamic formula
(II) Hiley formula(Q) Pile group efficiency
(III) Newmark's influence chart(R) Bearing capacity factor of saturated clay
(IV) Skempton's equation(S) Increase in vertical stress below footing
Option giving the CORRECT match between Column 1 and Column 2 is:
A circular pile of 600 mm diameter and 6 m length is embedded in a saturated clayey soil. The undrained cohesion of the soil is \(c_u = 80\) kPa and its unit weight is \(\gamma = 19.20\) kN/m3. The adhesion factor is \(\alpha = 0.54\). If the diameter of the pile is doubled to 1200 mm, keeping the length constant at 6 m, the ratio of the pile capacity of the 1200 mm diameter pile to that of the 600 mm diameter pile is ______ (rounded off to two decimal places).
A group of 25 circular piles is arranged in a \(5 \times 5\) uniform pattern in a soft clay soil, with equal spacing in both directions. These are friction piles with negligible end bearing. Diameter of each pile = 1 m. Length of each pile = 15 m. Cohesion of the soil = 20 kN/m2. Unit weight of the soil = 16 kN/m3. Adhesion factor = 0.75. Considering the efficiency of the pile group as unity, the optimum value of the ratio of the pile spacing to pile diameter is ______ (rounded off to one decimal place).

A group of 9 friction piles are arranged in a square grid maintaining equal spacing in all directions. Each pile is of diameter 300 mm and length 7 m. Assume that the soil is cohesionless with effective friction angle \(\phi' = 32^\circ\). What is the center-to-center spacing of the piles (in m) for the pile group efficiency of 60%?