Crushing and Flooding Effects on One-Dimensional Time-Dependent Behaviors of a Granular Soil

Particle crushing contributes significantly to the time-dependent compression behaviors of crushable granular soils. It also is widely accepted that flooding aggravates the breakage level of soil particles. This study investigated the combined behavior. A crushable granular soil was chosen for one-dimensional compression tests, i.e., constant rate of strain tests and multistage loading oedometer tests, under dry and saturated conditions. The crushing mechanism of particles was investigated by measuring the microhardness of soil particles. The shape characteristics (circularity, aspect ratio, roundness, and solidity) of particles before and after tests were analyzed by digital image processing (DIP) methods. The results showed isotach behavior for the tested soil in saturated condition. The compression curve, creep behavior, and level of particle breakage of initially dry specimens evolved in the same manner in which the initially saturated specimens behaved. The microhardness test clearly attributed the breakage of particles to the disaggregation of clay minerals which are the bonding materials between microquartz particles. This disaggregation became more severe after the moisturization of soil particles. The plastic work done to each specimen and the corresponding breakage ratio were correlated by two hyperbolic functions, which define two characteristic curves, for dry and for saturated/flooded conditions. The results from DIP analysis indicated that the average values of shape descriptors of all the particles in one specimen changed during compression, with a greater level under saturated or flooded condition than under dry condition.