Chapter 6, Problem 6.5P

### 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 standard Proctor test are given in the following table.a. Determine the maximum dry unit weight of compaction and the optimum moisture content. Given: Mold volume = 1/30 ft3.b. Determine the void ratio and the degree of saturation at the optimum moisture content. Given: Gs = 2.69.The laboratory test in Problem 6.4 is used to develop field compaction specification for a highway project. A field unit weight determination during the construction revealed that the in situ moist unit weight is 124 lb/ft3 and the moisture content is 13.7%. Determine the relative compaction in the field.

To determine

The relative compaction in the field.

Explanation

Given information:

The in situ moist unit weight γ is 124lb/ft3.

The moisture content (w) value is 13.7 %.

The volume of the mold (V) is 130ft3.

Calculation:

Calculate the unit weight of soil mass for trial 1 using the relation.

γ=WV

Here, W is the weight of moist soil in the mold for trial 1.

Substitute 3.7 lb for W and 130ft3 for V.

γ=3.7130=111lb/ft3

Similarly, calculate the unit weight of soil mass for remaining trials.

Calculate the dry unit weight of soil mass for trial 1 using the relation.

γd=γ1+w100

Here, w is the moisture content for trial 1.

Substitute 111lb/ft3 for γ and 8.6 % for w.

γd=1111+8.6100=102.2lb/ft3

Similarly, calculate the dry unit weight of soil mass for remaining trials.

Summarize the calculated values of unit weight and dry unit weights as in Table 1.

 Volume (ft3) Weight of soil mass, W γ (lb/ft3) w (%) γd (lb/ft3) 130 3.7 111 8.6 102.2 130 4.15 124.5 10.6 112.5 130 4.69 140.7 12.5 125.0 130 4.62 138.6 14.9 120.6 130 4.02 120.6 16.7 103.3 130 3.63 108

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