DHARM432 GEOTECHNICAL ENGINEERING
12.5.5Abbot’s Compaction Test
A metal cylinder, 52 mm internal diameter and 400 mm effective height, with a base is used.
2 N of oven-dried soil is mixed with water and compacted in the cylindrical mould with a 50
mm diameter rammer of 25 N weight falling through a height of 350 mm. The number of blows
is decided by calibration with respect to Proctor’s compaction or field compaction.
The height of the compacted specimen may be determined from the reading of the gradu-
ated stem of the rammer. The volume of the compacted specimen is calculated from the known
cross-section and height. The wet unit weight may be obtained and also the dry unit weight
from the known dry weight of the sample.
The compaction curve is obtained in the usual manner.
12.5.6Dietert’s Test
The apparatus consists of a 50.8 mm diameter mould supported on a metal base. Compaction
is done by means of a piston on which a cylindrical weight of 81.65 N operated by a cam, falls
through a height of 50.8 mm.
Air dried soil weighing 1.5 N and passing through 2.36 mm IS Sieve, is mixed with
water and compacted in the mould by application of 10 blows. The mould is inverted and
another 10 blows are applied. The weight and length of the compacted soil cylinder are deter-
mined, from which the volume and bulk unit weight of the soil are obtained. The water content
is determined by oven-drying. The test is repeated with different water contents and the
compaction characteristics are established from a graph.
12.5.7Jodhpur Mini-compactor Test
The Jodhpur Mini-compactor (Singh, 1965) consists of a cylindrical mould of cross-sectional
area 50 cm^2 (79.8 mm diameter and 60 mm effective height) and a volume of 300 ml, and a
ramming tool with a 25 N drop weight (DRT which means “Dynamic Ramming Tool”), falling
through 250 mm. The drop weight falls over a cylindrical base, 40 mm in diameter and 75 mm
in height. The soil is compacted in two layers, each layer being given 15 blows with the ram-
ming tool.
The compactive energy transmitted is 625 N.m per 1000 cm^3 of soil. Calibration tests in
the laboratory (Singh and Punmia, 1965) have shown that the maximum dry unit weights and
optimum moisture contents obtained from the Jodhpur mini-compactor are comparable to those
obtained from the Standard Proctor Test.
12.6 In-situ or Field Compaction
As indicated in Sec. 12.1, in any type of construction job which requires soil to be used as a
foundation material or as a construction material, compaction in-situ or in the field is neces-
sary.
The construction of a structural fill usually consists of two distinct operations—placing
and spreading in layers and then compaction. The first part assumes greater significance in
major jobs such as embankments and earth dams where the soil to be used as a construction
material has to be excavated from a suitable borrow area and transported to the work site. In
this phase large earth moving equipment such as self-propelled scrapers, bulldozers, graders
and trucks are widely employed.