| The Huainan coalfield is located in the southern margin of the North China plate which is a typical karst area in North China.Its nappe structure and karst phenomenon are relatively developed.The surface karst restricts the development of the city and underground karst often induces mine geological disaster in the coal field,which brings great hidden danger to the life and properties of the people and the safety of mining production in the study area.By such means as of the field investigation of karst geological,the observation of karst characteristics,the statistics of structural and hydrogeological characteristics,the analysis of numerical simulation and other methods,the influence of the lithologic structure,structure distribution and groundwater flow on the karst development are studied in the outcrop and covered areas in formation and development of karst are revealed,the patterns of karst development are constructed and its formation mechanism is discussed.The main conclusions are as follows:1.The formation strata of karst development in Huainan coalfield are mainly concentrated in the gray dolomite of the Majiagou formation,the contact zone of Oolitic Limestone and the marl rock,the thick layer Oolitic Limestone of Zhangxia formation and Maozhuang formation.2.The development of karst is the result of the interaction of original lithologic structure,multi-stage geological structure and groundwater flow.Karst development is mainly composed of thick layer limestone and second place is taken by gray dolomite3.The structure controls the location,form and direction of karst development.The directions of NNE and NW are mostly karst development directions,and karst is often developed at the intersection of fractures.The form of karst development is controlled the occurrence,density and filling of joints in rock mass.4.Dynamic of groundwater is one of the factors affecmting the scale of karst development,and mine drainage is one of the main inducting factors of shallow covered karst collapse.5.According to karst burial types,the karst development models are three types: bare,covered and buried.From the genetic mechanism,the bare karst is subdivided into structural damage-suffosion development pattern and structure damage-lithologic association control suffosion development pattern.The covered karst is summarized as the gravity load-drainage and pumping of mine cause suffosion development pattern.And the buried karst is generalized into three patterns: growth paleo karst,declining paleo karst and death type paleo karst.6.The process of effect by groundwater flow and evolution process of karst development during different tectonic stages are reconstructed by numerical simulation method. |
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