Mechanical and Microstructural Properties of Alkali Wastes as Filling Materials for Abandoned Salt Caverns

Abstract

Alkali solid waste from soda industries has previously been stacked on surface and contaminated soil and groundwater. In China, an engineering method of filling alkali wastes into abandoned salt caverns is adopted. This method can solve the problem of waste disposal and the potential geological disasters associated with salt caverns. In such filling projects, the engineering properties of alkali wastes are important for the safety and stability of salt caverns. In this study, the microstructural and mechanical properties of alkali wastes were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to analyze the microstructure and mineralogy of such wastes. Direct shear tests were conducted to evaluate the mechanical performance and to obtain the strength parameters of alkali wastes. The basic physical characteristics, microstructure, mineral compositions, and mechanical properties of alkali wastes vary significantly at different burial depths. Moreover, the strength properties of alkali wastes are close to those of the two other common filling materials, sandstone–mudstone mixtures and tailings. The research results can be used as a reference for similar filling projects and can also be beneficial for the cyclic utilization of alkali wastes. An engineering method that utilizes alkali solid wastes to fill abandoned salt caverns is introduced, and the engineering properties of alkali wastes are studied.