Static Compaction Characteristics of Coarse and Fine Grained Soils

Abstract

The modified Proctor’s test, the reduced modified Proctor’s test, the standard Proctor’s test and the reduced standard Proctor’s test are dynamic methods which are often used in the laboratory to ascertain the compaction characteristics of soils at different energy levels. To perform these tests considerable time and effort are needed. A laboratory procedure is devised to determine the relationships between moisture content and dry unit weight by using static compaction method for different static pressures. The static compaction pressure test is performed in the Proctor mould to statically compact the soil at different moisture contents. This method is less laborious and the time involved is less. An attempt was made to predict the compaction characteristics by static compaction method and parabolic curves were obtained between moisture content versus dry unit weight at different static pressures. The static pressure equivalent to the standard energy input of a standard Proctor test to obtain the Proctor’s optimum moisture content (OMC) and maximum dry unit weight (MDUW) was determined for fine grained soil. The main objective of present study is to determine the static compaction characteristics of both coarse and fine grained soils and compare it with that of the dynamic compaction characteristics at different compactive efforts. For this, eleven different soil samples of classification CI, CH, SC, SP and SM were tested. The analysis shows that the relation between moisture content and dry unit weight in static compaction for different static pressure is parabolic in nature for CI & CH class of soil. For SP class of soil, both the static and dynamic compaction curves show an undulatory pattern with maximum dry unit weight near dry and towards saturated condition. The dynamic compaction curve for both SC and SM class of soil is parabolic in nature. For SM class of soil, static compaction curve show a wavy pattern with maximum dry unit weight at dry and near saturated condition whereas for SC class of soil only one sided compaction part of the curve for the rising portion of the dry of optimum side was generated. In case of coarse grained soils, an equivalent static pressure, at which maximum dry unit weight at optimum moisture content can be obtained corresponding to different dynamic efforts, could not be determined as that of fine grained soils. Further, the static pressure—dry unit weight relationship for a particular moisture content was identified as a rectangular hyperbola.