Study Of Multi-component Solutes Release And Transport In Coal Mine Waste Rock Pile

In the open air, the precipitation will produce leaching effect to the coal mine waste rock pile, the leaching solution which contain many solutes would influence the water quality in coal mine area. The characteristics of this influence may have hidden and long-term behaviour. Complexity of the coal mine gangue particle size and components,and structure characteristics formed in piling and dumping would make the coal mine waste rock pile to be heterogeneous material. Therefore, the water movement and water-rock interaction in the heterogeneous material appear special regularity.This article analyze the features of the coal mine gangue and pile firstly, and generalize the types and characteristics of the coal mine gangue and pile which belong to most coal mine in plain area in China. Compare the slide-rockfall theory with the dumping and find out the method of description of the coal mine gangue, then the numerical calculation and similar analogue method is used sepatately to annalyze the particle distribution on dumping slope and internal area. The MATLAB digital processing technic is used to establish the cross-section digital model which could reflect the heterogeneous characteristics. The precipitation/dissolving phase is introduced to construct the hydro-solute transport coupled model which consider the geochemical effect. Static leaching experiment is processed to study the dissolve-release characteristic, sulfide oxidization, silicate weathering and ion-exchange effects. According to the coupled model and model parameters, the COMSOL Multiphysics software is used to simulate the release and migration in 20 years of the ions which contain Cu ²⁺,Zn ²⁺,SO₂^4-,Al³⁺,Si⁴⁺,Ca ²⁺,Mg ²⁺,K⁺,Na⁺.The conclusions from the results metioned above are following:(1). Coal mine gangue have explicit endemic character, complex component, widely size distribution and could be easily weathered. The coal mine waste rock pile is homogeneous and spontaneous combustion, it also has specific geometry.(2). Grain size of gangue should be introduced to classification criteria.(3). Size distribution of coal mine gangue on dumping slope could be divided into three parts: the smaller size mainly distribute on upper domian, the medium size most distribute in centre portion of the slope, and the larger size mainly distribute in the bottom of the dumping slope.(4).The cross section of the coal mine waste rock pile which used with heap piling-end dumping manner has the zigzag cross-bedding.(5). According to introduce the precipitation/dissolving phase, we could deduce the hydro-solute trasnport coupled model which considering the geochemical effects.(6). Solute dissolve and release from the coal mine gangue could be divided into two parts, one is fast dissolve period and the other is slowly release period. Different period could be expressed by liner equation.(7). The relation between particle size and the dissolve-release quantity satisfy the power function.(8). Acid-base evolvement of the coal mine waste rock pile could be divided into four parts: calcite alkalinity period, silicate drag acidic period, sulfide acidic period and continuation reaction period.(9). Water movement in the homogeneous coal mine waste rock pile is quite different from the heterogeneous model. In the heterogeneous model, the dumping slope zone has the faster water velocity, slower release velocity , faster migrational velocity and weaker acidic than orbit slope zone.