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

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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.