4_engineering geology and soil mechanics_chapter 5_permeability and seepage

7/25/2019 4_Engineering Geology and Soil Mechanics_Chapter 5_Permeability and Seepage

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6.18.

6.18

Page 27 of 32

For the case presented

at page 29 of 32

CHAPTER 5


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Chapter 5 Ground Water, Permeability and Seepage Engineering Geology & Soil Mechanics

Soil Mechanics_Chapter 5_Class Practice_2014

Chapter 5Ground Water, Permeability and Seepage

Class Practice

Q.1 A laboratory set-up as shown in the diagrammatic sketch in Figure Q.1 was used for

determination of the coefficient of permeability of an undisturbed soil sample

obtained from the field. The test results are given in the diagram.

(i) Determine the hydraulic conductivity of the soil in mm/min.

(ii) Find the seepage velocity of water in a soil column if the soil porosity equals

to 0.35 and the hydraulic gradient across is unity.

Q = 3.2 litre

in 650 sec

Cylinder

D = 0.1m

SOIL

0.5 m

L = 0.25 m

Not to Scale

Figure No. Q.1


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Q.2 A pumping test was carried out in a confined aquifer of the construction site, the

depth of a pump well is 10m and the thickness of an impermeable stratum above

the confined aquifer is 7m. The top level of the impermeable stratum is the

existing ground surface. The following data and results are collected.

Volume of ground water collected from the pump well = 0.04 m3

Time for collection of ground water = 65 minutes

Thickness of aquifer = 3 m

Distance between pump well and observation well 1 = 4 m

Distance between pump well and observation well 2 = 8 m

Measured depth of ground water level in

observation well 1 from existing ground surface = 5 mMeasured depth of ground water level in

observation well 2 from existing ground surface = 2 m

Based on the above information, determine the coefficient of permeability of the soil.

Chapter 5 Ground Water, Permeability and Seepage

Class Practice


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Q.3 The site condition as in Figure Q3, a 10.0 m thick layer of sandy soil overlies an

impermeable rock. Ground water level is at a depth of 1.85 m below the top of the soil.

Water was pumped out of the soil from a central well at the rate of 6.5 m3/minute and

the drawdown of the water table was noted in two observation wells. These two wells

were on a radial line from the centre of the main well at distances of 4.40 m and 35.00

m. When a steady state was achieved, the drawdowns of water level in the well

nearest to the pump was 3.50 m and in the furthest well was 1.00 m below initial

water table. You are asked to determine with detail calculations on the following:

(i) the coefficient of permeability (in m/s) for the sandy soil deposit.

(ii)

the drawdown in a new observation well if it was located 20 m from the

pumping well.

(iii) the radius of influence due to the field pumping test.

Figure Q3

Chapter 5 Ground Water, Permeability and Seepage - Class Practice


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4_engineering geology and soil mechanics_chapter 5_permeability and seepage

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