Collapse and strength characteristics of loess in Thailand

Abstract

Collapse and strength characteristics of loess of Thailand are presented. The metastable loose structure of the soil which makes it susceptible to collapse is mainly attributed to clay-bridge bonds. Collapsibility of the loess is strongly governed by water content and the magitude of applied stress. Under an increasing load, the critical pressure at which collapse started to occur was greater for the loess with a lower water content. At natural water content the critical pressure was greater than the overburden pressure. Collapse caused by wetting at a given applied stress always resulted in approximately the same final porosity regardless of the initial water content. This reflected the existence of a unique post-wetted relationship between void ratio and applied stress. The predicted collapse settlement based on the double consolidation test results compared reasonably well with the settlements measured in the field, plate bearing tests. For shear strength, besides the initial water content and consolidation pressure, drainage condition is an important influencing factor. Loose structure could remain after initial saturation and consolidation at pressure as high as 400 MPa, leading to a much lower undrained strength than drained strength.