Compressibility of lightweight cemented clays

Compressibility characteristics of a lightweight cemented clay are important issues for deformation analysis. This paper attempts to analyze and assess the compressibility characteristics of lightweight cemented clays. Three types of clay, kaolin, Bangkok clay and bentonite, representative of non- to high swelling clays are used for this study. It is found that a lightweight cemented clay is stable in the meta-stable state. The void ratio of a lightweight cemented clay is the sum of the void ratio sustained by the intrinsic soil fabric (destructured void ratio) and the additional void ratio due to cementation. At post yield state, the additional void ratio is made of two parts, the part that is inversely proportional to effective vertical stress and the residual additional void ratio, esr, which cannot be eliminated by the increase in effective vertical stress. The esr is mainly dependent upon the mineralogy or soil type (swelling potential). The suggested esr values are approximately 0.49 for kaolin, 0.18 for Bangkok clay and 0.10 for bentonite. The rate of destructuring, b is mainly dependent upon the soil structure (degree of cementation and fabric reflected by the initial void ratio and swelling potential). The relationships between esr versus liquid limit void ratio eL and between b versus yield stress, initial void ratio and eL are proposed. Based on the two proposed relationships, a practical (simple and rational) method for assessing the compressibility of lightweight cemented clay with various soil structures is suggested. The prediction method is useful not only for the quick determination of a compression curve with acceptable error, but also for the examination of the test results.