| Karst areas in China are widely distributed. However, with the engineering construction scale expanding gradually, building all kinds of engineering facilities in karst region becomes inevitable, people also gradually realize the dangers of the karst geology upon structures. Especially when encountering buried karst stratum in the process of bridge pile foundation construction, generally it is taken into consideration to put the pile foundation above the roof. Therefore, the research on cave roof stability is mentioned to agenda. Based on Project under the name of Study on Engineering Characteristics of Buried karst of Yi Lou Highway and Its Treatment Technology, this study develops a research on the interaction mechanism and the stability of karst cave roof and the bridge pile foundation, which makes great application value in providing certain reference function for subsequent engineering design, safety construction and later operation.The main work done and research results obtained in paper are as follows:(1) The paper firstly introduces the characteristics of the buried karst, simplifies the classification of the pile and the roofs models through making the basic assumptions of the model and obtains 10 kinds of common mechanical structure models. Based on that, the detailed stress analysis on the roof and bridge pile foundation load system model is made with the theory of thin plate of elastic mechanics, which obtains the corresponding formula of roof thickness inspection.(2) according to the practical experiences of the construction of bedrock cave roof, the factors influencing cave roof stability are analyzed, the analysis shows that when karst cave is buried in a certain depth, the greater the roof span, the thicker minimum safety thickness allowed; while the deeper cave hole, the smaller minimum safety thickness; the roof span is a very unfavorable factors to the stability of karst cave, while the cave of the deep hole is favorable one.(3)the paper analyze the instability mechanism of karst from the reason for the cave's instability, and karst buckling model is established with the theory of rock strength to analyze the mechanism, from which obtains a conclusion that karst instability mechanism is the mechanics mechanism:actually loads lead to strength failure so that the instability of rock and soil mass.(4) simulating and analyzing beam model selected from the structural model, the paper checks punching shear, shear and bending of the stability of the roof under different pile diameter combining with the characteristics of the model. According to calculation, beam slab models composed of foundation pile and roof appear on the safe and stable state, which can guide the engineering design and construction.(5) This paper uses the numerical software FLAC-3D to simulate and analysis the stability of the pile and the karst cave roof under piers of Shi Ba Chong Bridge of tenth contract segment of Yi Lou highway located K81+843 and K81+878. By analyzing, the author recommended using the sleeve reinforcement technique for reinforcement of pile located K81+878, and the research conclusion can be used to guide design and construction of bridge foundation engineering of Yi Lou highway. In addition, the numerical simulation for analysis of such problem is practical and reliable, and being worthy of further research. |
PDF Full Text Request