Head of Water

Q. Two observation wells penetrating into a confined aquifer are located 1500 m apart in the direction of flow. Heads of 50 m and 25 m are indicated at these two observation wells. If the coefficient of permeability for the aquifer is 30 m/day and its porosity is 0.25, the time of travel of an inert tracer from one well to another is

1. 75 days
2. 750 days
3. 1200 days
4. 3000 days

Q. Consider the following statements:
1. The hydraulic head at a point in the soil
includes piezometric head as well as datum head.
2. Piping in soil occurs when effective pressure becomes equal to zero.
3. Piping in soil occurs when soil is highly porous.
Which of these statements is/are correct?

1. 1. 2 and 3
2. 1 and 2 only
3. 2 and 3 only
4. 2 only

Q. A strata of 3.5 m thick fine sand has a void ratio of 0.7 and G of 2.7. For a quick sand condition to develop in this strata, the water flowing in upward direction would require a head of

1. 7 m
2. 5.56m
3. 5 rn
4. 3.5 m

Q. In a variable head permeability test, the head was noted to fall from 100 cm to 75 cm in 2.5 minutes. If the time required to drop head further remains same, the final head of water is_____ cm.

1. 56.26
2. 29.36
3. 48.39
4. 76.17

Q. Water is flowing at a steady rate through a homogeneous and saturated horizontal soil strip of 10 m length. The strip is being subjected to a constant water head of 5 m at the beginning and 1 m at the end. If the governing equation of flow in the soil is $d^{2}H/d{x}^2=0$ (x = distance along the soil strip) value of H (in m) at the middle of the strip is

1. 3

Q. Laplace equation for water flow in soils is given below.

$\frac{{\partial }^{2}H}{\partial x^2}+\frac{{\partial }^{2}H}{\partial y^2}+\frac{{\partial }^{2}H}{\partial z^2}=0$

Head H does not vary in y and z direction. Boundary conditions are: at x = 0, H = 5, and $\frac{dH}{dx}=-1$. What is the value of H at x = 1.2 ?

1. 3.8

Q. In the fig. shown aside, the head (h) required to cause quick condition is

1. ${\gamma }^{\prime }L/{\gamma }_w$
2. $({\gamma }^{\prime }L+q){\gamma }_w$
3. $({\gamma }^{\prime }L-q){\gamma }_w$
4. $({\gamma }^{\prime }L+H_w+q)/{\gamma }_w$