| Cave, soil cave and the collapse caused by them have been paid more and more attention in Karst region. At present, The studies of cave, soil cave and collapse are only focused on the formation mechanism and precaution of Karst collapse, moreover, the qualitative evaluation method has been taken more than the qualitative evaluation method in the evaluation of Karst. The theory for Karst ground treatment is not enough perfect. Based on intensive geologic investigation in this dissertation, the methods of elastic and plastic theory, limit equilibrium theory, rocks mechanics and soil mechanics theory, groundwater dynamics theory, and geotechnic test have been taken. The stability of cave and soil cave foundation, bearing capacity of foundation, the settlement and deformation of foundation, and Karst ground treatment have been studied. Conclusions are made as follows:1. The formation mechanism of cave and soil cave has been analyzed. Cave will be formed easily in the limestone of more simple component or thicker layer. The style and scale of geologic structure play an important role on cave formation. The seepage erosion and disintegration produced by the activity of ground water will result in formation of soil cave. The stress distribution of soil cave periphery will be changed because of the variation of groundwater level, then the soil of cave periphery maybe destroyed and the soil cave maybe enlarged or collapse.2. Geological structure, structural plane, rock property, cave shape and groundwater are important factors of qualitative evaluation for cave foundation stability. Based on elastic theory, the stress distribution on cave has been deduced first in the rock foundation. Though analysis, this paper point out, increase the dimension of base or decrease the distance between bottom of base and roof of cave will be helpful to foundation stability. The diameter of cave and the shape of cave have great influence on foundation stability. The smaller the diameter of cave is, the more stable the foundation is. The smaller the ratio between vertical axis and horizontal axis of elliptic cave is, the less foundation stability is. The'vacuum suction action' produced by groundwater has little influence on foundation stability. The effect on foundation stability is small when the cave is filled with some materials. Even according to the item 5.1.10 of 'Code for investigation of geotechnical engineering' GB50021-2001 or the item 6.5.4 of'Code for design of building foundation' GB50007-2002, the cave's disadvantageous effect on foundation may not be considered, the stability of foundation with cave should be calculated also.3. The activity of ground water and surface water are the most important factors of soil cave foundation stability. Based on elastic and plastic theory, limit equilibrium theory and Mohr-Coulomb yield criteria, the stability of soil cave foundation has been analyzed and evaluated first. The variation of groundwater level will caused marked change of stress distribution in soil cave periphery, and the soil cave foundation will be also probably damaged. Even according to the item 5.1.10 of 'Code for investigation of geotechnical engineering' GB50021-2001 or the item 6.5.2 of'Code for design of building foundation' GB50007-2002, the soil cave's disadvantageous effect on foundation may not be considered, the stability of soil cave foundation should be calculated also, especially when the groundwater in foundation, it should be paid more attention.4. The shear strength indexes c and values is the most key parameters in the calculation of soil cave foundation. There have different c and values when the consolidated drained condition is varied. The shear strength test result of different consolidated drained condition should be taken in different soil.5. In the process of artificial pumping water, the possibility of soil cave collapse will be increased when the quantity of pumping water become larger or the distance from pumping well become less. In sandy soil, the much ti...
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