It has been anticipated that the soil under the proposed dam is contaminated, and needs to be removed and backfilled to a depth of 2.5 feet. A Standard Proctor compaction test was conducted on soil from a borrow pit, with the results shown below right. Based on the results: a) Plot the Proctor curve for the borrow soil. b) Find the optimum water content and max. dry unit weight for the borrow soil. c) Determine whether the unit weight of the top layer can be met by compacting to 95% of maximum, and what the range of moisture content for that unit weight is.

Principles of Geotechnical Engineering (MindTap Course List)
9th Edition
ISBN:9781305970939
Author:Braja M. Das, Khaled Sobhan
Publisher:Braja M. Das, Khaled Sobhan
Chapter9: In Situ Stresses
Section: Chapter Questions
Problem 9.13P
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It has been anticipated that the soil under the proposed dam is contaminated, and needs to be removed and backfilled to a depth of 2.5 feet. A Standard Proctor compaction test was conducted on soil from a borrow pit, with the results shown below right. Based on the results:

a) Plot the Proctor curve for the borrow soil. 

b) Find the optimum water content and max. dry unit weight for the borrow soil.

c) Determine whether the unit weight of the top layer can be met by compacting to 95% of maximum, and what the range of moisture content for that unit weight is. 

d) If we borrow soil from a pit with a void ratio of 0.71, determine how much soil we need to borrow to backfill below the dam to match the in-situ void ratio of the top layer of soil. 

The concrete dam in the figure below is to be built on top of a soil whose profile consists of two
horizontal layers of soil, each 5 ft thick. The depth to the groundwater table is approx. 6 feet. The
dam is anticipated to weigh approx. 8200 psf, and will be 120 feet long (the dimension into and
out of the page).
The layers of the soil have the following properties:
k (ft/s)
unit weight (y)
(pcf)
void ratio
(in-situ)
Y (pcf)
top
8.2 × 10-3
122
0.47
W
102.32
3.8%
109.44 13.1%
121.45 6.1%
123.64 9.3%
132.75 7.9%
bottom
1.9 × 10-7
130
0.33
8 ft Water
10 ft
1
20 ft
Concrete dam
2 ft water
Transcribed Image Text:The concrete dam in the figure below is to be built on top of a soil whose profile consists of two horizontal layers of soil, each 5 ft thick. The depth to the groundwater table is approx. 6 feet. The dam is anticipated to weigh approx. 8200 psf, and will be 120 feet long (the dimension into and out of the page). The layers of the soil have the following properties: k (ft/s) unit weight (y) (pcf) void ratio (in-situ) Y (pcf) top 8.2 × 10-3 122 0.47 W 102.32 3.8% 109.44 13.1% 121.45 6.1% 123.64 9.3% 132.75 7.9% bottom 1.9 × 10-7 130 0.33 8 ft Water 10 ft 1 20 ft Concrete dam 2 ft water
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Can you show how to do part d I had the first 3 parts done before. I was confused with part D

 

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