Dry shrinkage cracking and permeability of biopolymer-modified clay under dry-wet cycles

Biopolymers efficiently improve the anti-seepage function of compacted clay layers, but research concerning the permeability stability of biopolymer-modified clay during cyclic wetting and drying is scarce. In this paper, the macro-microstructures and the permeability coefficients of biopolymer-modified clay and conventional bentonite-modified clay under dry-wet cycles are comparatively studied. The bentonite modifier is found to increase macro-microscopic cracks under dry-wet cycles, while the xanthan modifier decreases the macro-microscopic fracture rate of the clay. The physical properties of 2% by dry weight xanthan-modified clay are similar to those of 10% by dry weight bentonite-modified clay, but the permeability coefficient of the former is lower by approximately one order of magnitude. After the dry-wet cycles, xanthan-modified clay performed better in leakage prevention than bentonite-modified clay. For low-liquid-limit clay, the recommended mass percentage of xanthan gum was 1.5% considering the seepage resistance safety during dry-wet cycles.