Study on mechanical properties and destabilization mechanism of unclassified tailings consolidation body under the action of dry-wet cycle

Abstract

Tailings consolidation displacement technology is one of the ways to efficiently dispose of tailings waste and reduce tailings storage in surface tailings ponds. Unclassified tailings consolidation body (UTCB) under natural conditions is inevitably subjected to high temperature drying and rainfall wetting cycle changes (i.e. dry-wet cycle effect), which is the crucial factor affecting the stability of UTCB. The essence of destabilization damage of UTCB is an energy-driven crack progressive development process. This paper introduces the energy conservation theory and explores the destabilization mechanism of UTCB under the action of dry-wet cycles by combining macro mechanical parameters and meso structural characteristics. The results showed that as the number of dry-wet cycles increased, the mechanical parameters of UTCB at 3 and 7 d curing ages increased and then decreased. The pore size of the internal pores of UTCB matrix was dominated by micro-pores <10 nm. Increasing the number of dry-wet cycles caused the pore size to transform to 10–100, 100–1000 nm pore sizes. Moreover, at the initial period of the cycle (0–5th cycle), increasing the number of cycles induced the elastic energy curve to shift to the left, corresponding to the increased energy storage capacity of UTCB. At the later period of the cycle (10–15th), the elastic energy curve and energy storage level of UTCB showed the opposite trend. The dissipative energy and the energy difference (ek) curves better depicted the crack sprouting, expansion, propagation and convergence as well as energy storage, release, and dissipation processes of UTCB under the load. Dry-wet cycles induced a transition from shear failure to mixed tensile-shear failure after UTCB damage. At the initial period of the cycle, the surface layer of UTCB did not change significantly. At the later period of the cycle, the surface layer of UTCB was peeling off. There was a competitive relationship between cement hydration reaction, water erosion and temperature-induced particle expansion and contraction phenomena, which were the main factors causing changes in mechanical properties and energy storage of UTCB.