EFFECTS OF MOISTURE CONTENT ON THE RESILIENT MODULUS OF COMPACTED SUBGRADE SOILS IN AN ARID REGION

Abstract

The purpose of this study is to illustrate how the resilient modulus of three soils with varying grain size composition and mineralogy of their fines content is affected by moisture variations. The resilient modulus, a parameter measuring the subgrade material stiffness, was tested at five different states of moisture and compaction. For each of the three types of soils, the effects of moisture variation on the determined resilient modulus were shown. Since floods or severe soaking will alter the moisture condition for soils compacted at a dry of optimal state, this study recommends adjusting the resilient modulus determined by the laboratory.  Although the ranges given here are pertinent to local soils, the general pattern will be the same for soils with comparable mineralogy and structural characteristics. Wetness was found to have the greatest effect on fine-grained, plastic, and highly plastic soils. In the Greater Khartoum region, where a compaction water content tolerance of +/- 2% is implemented during pavement construction, a 10% drop in MR is advised for fine-grained clayey soils.