地球化学作用下饱和-非饱和介质水力-传质-传热耦合模型

A Coupled Model of Hydro-Transport-Thermal in Variable Saturated Porous Media Considering Geochemical Process

地球化学作用是影响岩土类多孔介质中流体流动、传质、传热的重要因素之一。基于Fredlund所提出的非饱和土四相理论,将地球化学作用所产生的溶解/沉淀视为一个独立相,在一定的假设基础上,利用溶质浓度对介质孔隙度、含水率进行修正,从而建立起传质过程与介质水力性质之间的关系,改进了传统模型中传质过程与流体密度、黏度之间单一的耦合关系;并以此为基础建立了考虑地球化学作用下饱和-非饱和介质中多组分、多相流体渗流场-浓度场-温度场耦合的数学模型。通过在实验室内对反应性煤矸石进行渗透实验的结果对笔者所建模型进行了验证,结果表明:综合考虑溶解作用时所测点处渗流速度与未考虑耦合作用的结果相比增大0.58倍;单独考虑溶解/沉淀相时,所测点处渗流速度与未考虑密度耦合作用时的结果相比增大0.44倍。水流的实际渗透速度与在使用考虑溶解/沉淀相计算模型时的结果吻合较好。

Geochemical process is one of the most important factors influenced fluid movement,solute transport and heat transfer in porous media such as rock and soil.Based on the unsaturated soil theory established by Fredlund,in which the unsaturated soil porous media has been considered as a media which has four phases,assumed the effect of precipitation/dissolution to be an individual phase.With some hypotheses,the porosity and water content of porous media are modified by solute concentration,a new coupled relation between solute transport and hydraulic parameters has been built.The new relation updates the traditional coupled model in which the impact from solute field acts on seepage flow field by only density and viscosity.Here,a coupled model of multi-phases and multi-components hydraulic-transport-thermal and geochemical processes in variable saturated porous media is established.Using a infiltrate experiment for reactive coal mine gangue in the laboratory,the coupled numerical model is tested.The results show that the water seepage velocity calculated from experiment matches well the outcome from numerical model which considered the precipitation/dissolution coupling variable.Thus the applicability of the numerical model is verified.