5. Factors Affecting Soil Compaction
5
1. Moisture content
2. Compaction effort
Compaction energy per unit volume (function of number
of blows per layer)
For the stand proctor test: 12,400 ft-lb/ft3
For the modified proctor test: 56,000 ft-lb/ft3
3. Type of soil
Grain size distribution
Specific gravity of solids
Type and amount of clay materials
6. What does water do for compaction?
• Lubricant
• Too much water lesser density
• Optimum moisture content
(=maximum dry unit weight) best
compaction
6
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
10 11 12 13 14 15 16 17 18 19 20 21 22 23
gdry max
Optimum
Water
Content
10. Checking Soil Density in the Field
10
1- Sand Replacement Method
2- Rubber Balloon Method
3- Nuclear Density Gauge
Method
4- Core Cutter Method
11. 11
A small hole (6" x 6" deep) is dug in the compacted
material to be tested. The soil is removed and
weighed, then dried and weighed again to
determine its moisture content. A soil's moisture
is figured as a percentage. The specific volume of
the hole is determined by filling it with calibrated
dry sand from a jar and cone device. The dry
weight of the soil removed is divided by the
volume of sand needed to fill the hole. This gives
us the density of the compacted soil in lbs per
cubic foot. This density is compared to the
maximum Proctor density obtained earlier, which
gives us the relative density of the soil that was
just compacted.
1- Sand Replacement Method
