Guizhou Zhijin A Risk Evaluation Of Karst Collapse And Stability Analysis

Planning Constructing Project is located in the famous karst region-the northeast of Babu town, Zhijin Country, Guizhou Province. Taking into account the complexity of the karst site as well as the possible devastating consequences to the project, it is necessary to make the correct risk assessment and stability analysis of the project site. For this reason, a series of research work has been carried out in theory and practice.The main work and conclusions are as follows:(1) Based on the full grasp of the basic geological information and detailed exploration of the site, a complete explanation is given to the special conditions of geological environment in the karst site. A study is made of the effect factors on the karst collapse in the site and a analysis of the formation mechanism is described in the paper. The site has a subtropical humid monsoon climate zone, landforms plateau hilly topography, widespread carbonate rocks. The system of surface water is not well, but the surface karst is well developed and the groundwater is buried deeply which supply and excretion of cycles is not a strong role. There are two kinds of underground karst development types, vertical developments and horizontal developments. On the spatial distribution, the underground karst spread zonally and the surface karst is in linear arrangement. There are three kinds of geological generalized model types in the site, a single of water proofing cover, a single of water permeable cover and a sistance-permeable cover, but the single of water proofing cover is the main type of the three. The collapse is caused by the gravity, the upper load, the potential erosion and gravitational collapse, but the gravity and the upper load are the mainly reasons.(2) The effect factors of the karst collapse is noted. Twelve factors in five conditions, which are the terrain conditions, covering layers of karst conditions, structural conditions and groundwater conditions, are selected as predictors. Firstly the fuzzy multiple goals decision making is taken to established a multi-lever fuzzy evaluation of hierarchical model, in which the analytic hierarchy process is used to determine the weight of each layer factor in analytic hierarchy. Then the ModelBuilder module of ArcGIS is applied to build the space analysis model of karst collapse. Finally the risk evaluation result is achieved, which divides the site into the stable, the basic stable and unstable district.(3) The formation mechanism of the collapse is taken consideration. The mechanical model which the karst cave is under the action of the gravity and the upper load is established. On the basis of the geological generalized model and the collapse mechanism, FLAC3D is used to analysis the stability of karst collapse in the site by visualizing the force of damage mechanism and deformation characteristics.