Chapter 7, Problem 7.6P

### 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 results of a constant-head permeability test for a fine sand sample having a diameter of 70 mm and a length of 140 mm are as follows (refer to Figure 7.5):• Constant-head difference = 550 mm• Water collected in 7 min = 450 cm3• Void ratio of sand = 0.8Determine:a. Hydraulic conductivity, k (cm/sec)b. Seepage velocity

(a)

To determine

Find the hydraulic conductivity k.

Explanation

Given information:

The diameter of the specimen d is 70 mm.

The length of the specimen L is 140 mm.

The constant head difference h is 550 mm.

The volume of water collected Q is 450cm3.

The duration of water collection t is 7 min.

The void ratio of sand e is 0.8.

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×(1m1,000mm)2=0.0038m2

Determine the hydraulic conductivity k using the relation.

k=QLAht

Substitute 450cm3 for Q, 140 mm for L, 0

(b)

To determine

Find the seepage velocity.

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