Geological Structure And Karst Development Law On Both Sides Of The Beiyinshan Fault In The Eastern Part Of The Gejiu Tin Mine

The study area is located at the western edge of the first-order tectonic unit South China Folds.The crustal dynamics background is very complex.The main lithology is soluble rock(carbonate)-dolomitic limestone.The complicated geological structure conditions and soluble stratum lithology have led to a strong karst development in this area,and the geological structure has a very obvious controlling effect on the karst development.A large number of surface waters infiltrated through karst depressions,funnels,and sinkholes.The loss of surface water was serious.If we do not understand the characteristics of karst development in this area,it will bring a series of geological problems to the construction and site selection in the later period.Therefore,it is a very necessary and extremely important task to study the geological structure and karst development on both sides of the Beiyinshan fault in the eastern part of Gejiu tin mine,and to provide geology basis for future engineering survey,design and construction in the area.In this paper,a detailed hydrogeological engineering geological survey was carried out on the basis of the five-level concave pond tailings reservoir.Combined with previous research results and indoor data analysis,the geology structure background and karst characteristics of karst development in this area were studied systematically using ARCGIS software.Based on the geomorphological features and the spatial distribution of depressions and sinkholes,the mechanism and genetic model of karst development in this area were summarized.Finally,the finite element software ANSYS was used to simulate the underground caverns from the bottom to the top of the development of the concept of caverns,and the post-processing software TECPLOT output model under the conditions of the weight of the stress,displacement field distribution.Research shows:The study area is dominated by faulted structures and jointed structures.All identified faults are high-angle-translating faults with the typical characteristics of compression shear failure.More outcrops were found in geological surveys.Two sets of structural systems were proposed based on two different aspects.The difference between the two schemes was the extension direction of the Huangnidong fault,and the Huangmei fault was added to the alternatives.And the structure of the area controls the development and migration of landform,karst and karst water.The high-angle scissor-fractured tectonic system in the area provides channels and sites for precipitation infiltration and karst development,resulting in a karst development pattern that is “vertical oriented and supplemented horizontally”.From the distribution and size of the sinkholes and the geomorphological features of the atypical depressions,it can be inferred that the formation of sinkholes,funnels,and depressions in the study area was caused by the karst collapse model,and at the same time,it is also the main reason for the formation of "bottom-up" karst development mechanism in the area,which ultimately leads to unique karst geomorphological features in the study area.By investigating the five-level concave pond tailings reservoir currently in use in the area,it is inferred from the distribution and topography of sinkholes around the reservoir area that karst collapse is most likely to occur in the area.The sinkholes formed in the surrounding area are smaller in scale and have a small amount of leakage.They only need to be plugged and the project can be operated safely.