Improving fine-grained gypsiferous soil by increased compaction

Abstract

Presented in this paper is a study of the effect of compactive effort (CE) and long-term soaking on the strength characteristics of a clayey gypsiferous subgrade soil. The tested soil is A-6 (6) soil according to American Association of State Highway and Transportation Officials (AASHTO) soil classification system. To study the effect of CE and long term soaking on the properties of the tested soil, various California bearing ratio soil samples were prepared and compacted at optimum moisture content of the modified AASHTO compaction, but using four different chosen CEs of 12, 25, 56 and 70 blows/layer and then soaked for 0, 4, 7, 15, 30 and 120 days. The California bearing ratio (CBR) tests indicate that the CBR increases significantly in a nonlinear manner with increasing CE for all soaking periods, indicating improvement in soil strength with increased compaction. The rate of increase dies out with increasing CE. The CBR tests reveal also that there is a serious drop in the CBR due to soaking for all CEs.