A $4 \times 4$ group pile, with each pile 20 m long and 500 mm in diameter, is installed in a square pattern in a clayey soil, as shown in the figure. The average unconfined compressive strength of the soil is $100 \mathrm{kN} / \mathrm{m}^2$, and the adhesion factor is 0.8 . Neglect the bearing at the tip of the piles. For a group efficiency factor of 1.0 , the centre to centre spacing (s) of the piles (in m ) would be ________ (round off to two decimal places).

A single pile with 450 mm diameter has been driven into a homogeneous clay layer, which has an undrained cohesion ( $\mathrm{c}_{\mathrm{u}}$ ) of 20 kPa and unit weight of $18 \mathrm{kN} / \mathrm{m}^3$. The ground water table is found to be at the surface of the clay layer. The adhesion factor ( $\alpha$ ) of the soil is 0.95 and bearing capacity factor $\left(N_c\right)$ is 9 . The pile is supporting a column load of 144 kN with a factor of safety of 3.0 against ultimate axial pile capacity in compression.

The required embedment depth of the pile (in m ) is _________ (rounded off to the nearest integer).

A group of total 16 piles are arranged in a square grid format. The center-to-center spacing (s) between adjacent piles is 3 m. The diameter (d) and length of embedment of each pile are 1 m and 20 m, respectively. The design capacity of each pile is 1000 kN in the vertical downward direction. The pile group efficiency $${\eta _g}$$ is given by

$${\eta _g} = 1 - {\theta \over {90}}\left[ {{{(n - 1)m + (m - 1)n} \over {mn}}} \right]$$

where m and n are number of rows and columns in the plan grid of pile arrangement and $$\theta = {\tan ^{ - 1}}\left( {{d \over s}} \right)$$.

The design value of the pile group capacity (in kN) in the vertical downward direction is _________. (round off to the nearest integer)