Publications

Cemented backfill is a mixture comprising dewatered tailings, a cementitious binder, and treated mine water. It is used to fill excavated cavities created during underground mining operations. Once placed in excavated cavities, the backfill material undergoes thermal (T), hydraulic (H), and mechanical (M; including self-weight and stress from surrounding rock mass) processes, along with THM coupling effects. Consequently, the mechanical properties of in situ cemented paste backfill (CPB) can vary significantly from laboratory results. Relying solely on laboratory data for backfill design may result in underestimated or overestimated strength, potentially increasing backfill costs and compromising safety and stability in mining stopes. This study introduces a Cemented Backfill Twin Curing Apparatus (TCA) integrated with the THM effect to assess how the in situ Thermal-Hydraulic-Mechanical environment affects the mechanical properties of backfill material. Subsequently, the TCA was employed to create paired CPB samples, which were subjected to in situ curing, followed by a series of macro experiments aimed at uncovering the interrelationships between cemented backfill strength and multifactor coupling effects. These findings have the potential to enhance the design of cost-effective, stable, durable, and environmentally friendly backfill structures.

The main purpose of this study is to investigate the rheological characteristics and resistance evolution behavior of tailings-waste rock paste backfill. An AMETEK Brookfield R/S+ rheometer was used to test and study the rheological parameters of the paste, and a formula for calculating the transport resistance considering volume concentration, bulk density, and water-cement ratio was established. Secondly, the developed formula was put into COMSOL Multiphysics® to build a numerical model, and the filling loop test data was used to compare and verify the error of the numerical model was less than 8%, proving the numerical model's robustness. Finally, the effects of different tailings-waste rock ratios, inlet velocities, and concentrations on conveying resistance were analyzed, and the optimal filling parameters were obtained: tailings-waste rock ratios 5:5 and initial velocity 2.2 m·s-1. The properties of aggregate used in this study are different from those currently used in the concrete field; the optimal ratio obtained by computational fluid dynamics (CFD) simulation is applicable to the field in general. The research results of this paper have positive significance for developing coarse aggregate paste transportation technology, reducing pipeline transportation resistance, and extending transportation distance.