Role of Rubber Crumbs on the Stress-Strain Response of a Coal Wash Matrix

Abstract

The recycling of waste materials (e.g., coal wash, steel slag, recycled rubber, and fly ash) is becoming increasingly popular in ground engineering projects. While the physical properties of these waste materials can be different from those of traditional aggregates, their strength properties are often comparable to traditional quarried materials. This paper examines the stress-strain properties of four mixtures of coal wash and rubber crumbs (CWRC) under monotonic, consolidated drained conditions considering four confining pressures (i.e., 10, 25, 50, and 75 kPa). A three-dimensional (3D) function is proposed to describe the effect of rubber inclusion on the peak friction angle and the shear strength of the mixture. Also, the role of rubber inclusion on the characteristic state, peak state, and critical state is addressed and quasi-critical state parameters are defined to incorporate the ongoing rubber deformation even after large axial strains (i.e., > 20%). Given that one component of the mixture is highly compressible (i.e., rubber), a new equation that accounts for the compression of rubber particles and the associated change in the volume of the solid phase is proposed to estimate the void ratio. Alternatively, a modified void ratio that is independent of the volume of rubber within the mixture is defined and a dilatancy model is proposed accordingly.