Experimental Study on Small-Strain Elastic Parameters of Biochar–Methanotroph–Clay Mixture

Abstract

During the service of a landfill, uneven soil settlement and earthquakes can cause changes to the pore structure and cracks in the covering layer. The use of a biochar–methanotroph–clay mixture as a new landfill covering layer, can improve its engineering properties. The biochar–methanotroph–clay mixture’s shear-wave velocity and compression-wave velocity were measured by the bender–extender element test, and the elastic parameters under small-strain conditions, such as maximum shear modulus, Gmax, maximum constrained modulus, Mmax, and Poisson’s ratio, ν, were obtained. The parameters showed that the elastic characteristics and lateral deformation capacity were of great significance for settlement, seismic field, and stress–strain analysis. Based on the bender–extender element test, the effects of different compaction degrees, and biochar content on Gmax, Mmax, and ν of the biochar–clay mixture, and different methane cultivation days on the biochar–methanotroph–clay mixture, were investigated. The results showed that the Gmax, Mmax, and ν of the biochar–clay mixture increased with the increase in biochar content and dry density. When the biochar content was 15%, and the dry density was 1.64 g/cm3, the ν increased significantly. The Gmax and Mmax of the biochar–methanotroph–clay mixture tended to increase with the increase in methane cultivation days, and the higher the biochar content, the more obvious the increasing trend. The ν showed a decreasing trend with the increase in methane cultivation days, and the resistance to lateral deformation was stronger.