裂隙岩体渗流及污染物迁移模型的数值模拟研究

裂隙岩体的非均质性使得其渗流问题与传统多孔介质渗流存在本质差别.目前流行的裂隙渗流模型包括:离散裂隙网格模型;双重连续介质模型;等效连续介质模型.介绍上述方法优劣,并以中国东部某岛屿为基础,基于等效连续介质法,建立三维渗流模型以及污染物迁移模型.数值模拟结果显示,污染物被岩体的吸附程度对污染物运移影响巨大;降水入渗量增多会使得水流速度增快,却不会显著提升污染物运移至边界的时间,反而由于其增大了污染物向四周扩散的趋势,致使较少污染物迁移至边界;距断层较近的污染源不仅会导致污染物迅速迁移至边界甚至地表,并且质量分数显著提升.

Modeling fluid flow and tracer transport in fractured rock by the effective continuum method

Flow transport in fracture media is different from that in porous media due to anisotropy of fracture rocks.Available methods for treatment of fracture media include discrete fracture and matrix model, dual-continua method,and effective continuum method.Advantages and disadvantages of these methods are presented,and modeling studies for fluid flow and tracer transport in a field site with fractured rock are performed.The site of study is a small island in eastern China.A steady-state flow field with current climate condition is simulated using a simplified conceptual model of the flow system, which submits to mass conservation and Darcy’s Law.Result of the steady-state flow field is then used in further tracer transport simulations.It is found that adsorption is the most significant factor of transport.With higher infiltration,the tracer tends to reach the boundary with lower concentration.Because higher the infiltration,broader the tracer spreads.Accidentally inj ecting tracer near the fracture area may cause serious pollution.Tracer will quickly spread along the fault with boarder plume and higher concentration.In addition,a portion of the tracer will reach the surface.Therefore,it is necessary to pay close attention to water near faults.