Numerical Simulation of Consolidation Behavior of Large Hydrating Fill Mass

Liang Cui,Mamadou Fall

doi:10.1186/s40069-020-0398-0

Liang Cui, Mamadou Fall

Open Access

https://doi.org/10.1186/s40069-020-0398-0

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Abstract

Underground mined-out voids need to be backfilled for the stability of the surrounding rock and also to increase ore extraction from adjacent pillars. One of the relatively newer means is cemented paste backfilling, which has been extensively adopted in underground mining operations around the world. During and after the placement of cemented paste backfill (CPB) into stopes, complex multiphysics (thermal, hydraulic, mechanical and chemical) processes take place in the large mass of CPB and could affect its consolidation behavior. An analysis of the consolidation process in CPB mass is essential for the assessment of CPB behavior and cost-effective designs in practice. In this paper, multiphysics simulation of the consolidation behavior of CPB mass is performed under different conditions, including the mixture recipe, and backfilling, drainage, surrounding rock and curing conditions. It is found that the in situ consolidation behavior of CPB structures is a function of the multiphysics processes that occur in the cementing backfill mass. Moreover, the rock mass conditions, including the geometry and rock wall roughness, influence the consolidation process of CPB structures. Cement content, curing time and backfilling rate play a crucial role in the consolidation process of CPB. The obtained results can facilitate a better understanding of the consolidation behaviour of CPB for backfill designers and engineers, and thus contribute to enhance the engineering of CPB structures.

Highlights

Cemented paste backfill (CPB) is an engineered mixture of tailings, hydraulic binder and water (Fall et al 2007a, b)
After preparation in a backfill plant usually located on the mine surface, the fresh cemented paste backfill (CPB) is transported into underground stopes via reticulated pipelines and/or gravity system (Haiqiang et al 2016)
The mechanical performance of CPB structures is closely related to the consolidation process in the CPB

Summary

Introduction

Cemented paste backfill (CPB) is an engineered mixture of tailings (man-made soils), hydraulic binder and water (Fall et al 2007a, b). To address this problem Cui and Fall (2016a), developed a fully coupled multiphysics model that analyzes the consolidation process in CPB and incorporates the THMC processes that occur in CPB and affect its consolidation behavior This new approach fully considers the effect of self-weight, pore water flow and drainage, chemical shrinkage, thermal expansion, and temperature on the binder hydration. These two models are integrated to numerically model the consolidation behavior of CPB mass under various field conditions, including the filling rate, stope geometry and inclination angle, rock wall roughness, mix components (cement content) and drainage conditions The integration of these two models (multiphysics and elastoplastic interface models) is necessary in order to describe the consolidation behaviour of the CPB when arching effect takes place, i.e. in the case of narrow stopes. The arching effect significantly affects the distribution and magnitude of stress within the CPB, its consolidation behaviour

Fully coupled multiphysics model for consolidation process

Findings

Curing Stage