| Karst areas are widely in our country, and Guangxi is one. of the mostdeveloped areas. There are many projects of infrastructure construction in ourcountry in recent years, and complex karst condition will bring a series ofproblem in the projects of construction, repair, water conservation. The pilefoundation widely used in karst areas, so how to determine the best karst caveroof thickness has great significance in engineering practice.Based on a lot of litercltures at home and abroad and engineering practicalinformation, the paper described that the development of karst caves is affectedby the construction and fissure in karst area, and summed up the influence ofvarious factors situation on the karst cave roof. The rock mass classificationmethod has been discussed, and mechanical parameters of rock masses havebeen determined according to engineering practical information and relativelitervatures. According to elastic-plastic theory, computer simulation of thekarsts roof stability under pile foundation has been analyzed with 3-D FEM, andthe relations between each influence factors (mechanical of rock, size of karsts,pile's diameter,load on pile,weight of rock and soil etc.) and the distance from pile bottom to top of karsts cave(the critical thickness of karsts roof) have beenanalyzed. The optimum equation between the critical thickness of karsts roofand many influences factor has been obtained by multivariable linearstepwiseregression method.Finally, the engineering examples have been calculated through theregression equation, and the reliability of the regression equation has beenverified. The conclusion presented that the results was coincided with theengineering fact...
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