Chapter 7, Problem 7.8P

### Principles of Geotechnical Enginee...

9th Edition
Braja M. Das + 1 other
ISBN: 9781305970939

Chapter
Section

### Principles of Geotechnical Enginee...

9th Edition
Braja M. Das + 1 other
ISBN: 9781305970939
Textbook Problem

# The following data are for a falling-head permeability test:• Length of the soil sample = 140 mm• Diameter of soil sample = 70 mm• Area of the standpipe = 19.6 mm2• At time t = 0, head difference = 500 mm• At time t = 7 min, head difference = 350 mma. Determine the hydraulic conductivity of the soil (cm/sec)b. What was the head difference at t = 5 min?

(a)

To determine

Find the hydraulic conductivity of the soil.

Explanation

Given information:

The diameter of the soil sample d is 70 mm.

The length of the soil sample L is 140 mm.

The area of standpipe a is 19.6mm2.

The constant head difference (h1) at t=0 is 500 mm.

The constant head difference (h2) at t=7min is 350 mm.

Calculation:

Determine the area of the specimen A using the relation.

A=πd24

Substitute 70 mm for d.

A=π(70)24=3,848.5mm2

Determine the hydraulic conductivity k using the relation.

k=2.303(aLAt)log10(h1h2)

Substitute 19.6mm2 for a, 140 mm for L, 3,848

(b)

To determine

Find the head difference at 5 min time duration.

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