Application of FEFLOW to the description of karst conduit flow model

For a long time, it has been a challenge to describe the karst conduit flow in the research of groundwater numerical model at karst area. Giving these, this paper chose one item area in Liuzhi special district as an example to carry out the groundwater numerical simulation research, as well as to discuss the approach to depict karst conduit flow model by using FEFLOW software. The study area is situated in the typical karst mountains in Southwest China, and the groundwater mainly occurs in the form of karst conduit flow or karst fissure water in the area. Tectonically, this study area belongs to Rock Feet Syncline and rock stratum is relatively simple. According to field investigation there are some northeast beaded karst depressions in the south of the ash field selected by construction project; and the geophysical exploration has also confirmed the existence of hidden karst conduits. On the basis of a detailed analysis of geological and hydrogeological conditions and a careful examination of the scope, boundary, aquifer structure and etc. of the area, a hydrogeological conceptual model was established. Taking ArcGIS software as the assist and FEFLOW software based on the finite element method as the operation platform, by using borehole data and field measurement results, the elevation attributes of roof and floor in each layer have been acquired through formula editor and interpolation function of the software. After the data input to FEFLOW, a three-dimensional geological conceptual model of the synclines in the study area was established by carrying out the triangle subdivision to yield model area discretion. Through characteristic discrete function of FEFLOW, the karst depressions and rock feet spring in the south of ash field were defined as particular areas. By establishing a buffer zone with high specificity and coupling Hagen-Poiseuille flow equation, the karst conduit flow model was then depicted. The paper discussed the approaches to delineate special geological structure which was involved in the karst conduit flow model. The theory and method used in the study is a new attempt to solve relevant problems associated with establishing numerical model for the karstic aquifer, which may shed light on of the idea of conceptualization and modelling of geologically complex domains, especially the fractured-conduit flow in karst area.