A working shaft for pipe-jacking is going to be excavated into a sand stratum with high hydraulic pressure in Guangzhou, China. A newly assembled pre-stressed retaining system has been proposed to support the shaft fo...A working shaft for pipe-jacking is going to be excavated into a sand stratum with high hydraulic pressure in Guangzhou, China. A newly assembled pre-stressed retaining system has been proposed to support the shaft for its efficiency, safety and sustainability. Full-scale field tests and numerical analysis were conducted to analyze the base failure of the circular shaft with confined water. The failure process of the shaft was observed on site. The construction process of step-by-step excavation of shaft and layer-by-layer assembly of pre-stressed structure was simulated in detail. Simulation results agree well with the phenomenon on site. The base failure modes present that tensile damage generates at the center of the base due to non-uniform uplift and shear failure occurs along the soil-structure interface. The effects of shaft size and confined water head were also discussed. As a result, a critical ratio of diameter to shaft depth is put forward to assess the size effect of circular shaft. A conclusion that the soil strength should be partially considered in anti-inrushing safety factor calculation is drawn by analysis and comparison of various calculation methods. This research provides a reference for the base stability evaluation of similar shaft subjected to hydraulic uplift.展开更多
Finite element method(FEM) was used to investigate the effect of the number of layers on the bond strength for the brittle coating/substrate materials at contact load condition,which has not been addressed previously....Finite element method(FEM) was used to investigate the effect of the number of layers on the bond strength for the brittle coating/substrate materials at contact load condition,which has not been addressed previously.The maximum shear stress was used to act as the criterion of the bonded strength.This paper discussed the relationship between the number of coating layers and the maximum shear stress of the layer/substrate interface.Firstly,the results of the FEM and the Hertz analytical method were compared to verify the accuracy of the FEM model.It was found that with the increase in the number of coating layers,the position of the suddenly changed stress along the z axis is transformed from the interface to the external surface of the coating.Finally,the increase in the number of layers contributes to the decrement of the stress along the x axis.展开更多
基金Project(2017YFC0805008)supported by the National Key Research and Development Program of ChinaProject(265201708)supported by the Fundamental Research Funds for the Central Universities,China
文摘A working shaft for pipe-jacking is going to be excavated into a sand stratum with high hydraulic pressure in Guangzhou, China. A newly assembled pre-stressed retaining system has been proposed to support the shaft for its efficiency, safety and sustainability. Full-scale field tests and numerical analysis were conducted to analyze the base failure of the circular shaft with confined water. The failure process of the shaft was observed on site. The construction process of step-by-step excavation of shaft and layer-by-layer assembly of pre-stressed structure was simulated in detail. Simulation results agree well with the phenomenon on site. The base failure modes present that tensile damage generates at the center of the base due to non-uniform uplift and shear failure occurs along the soil-structure interface. The effects of shaft size and confined water head were also discussed. As a result, a critical ratio of diameter to shaft depth is put forward to assess the size effect of circular shaft. A conclusion that the soil strength should be partially considered in anti-inrushing safety factor calculation is drawn by analysis and comparison of various calculation methods. This research provides a reference for the base stability evaluation of similar shaft subjected to hydraulic uplift.
基金supported by the National Natural Science Foundation of China (Grant No. 51005102)Postdoctoral Science Foundation of Jiangsu Province (Grant No. 1002028C)+1 种基金Postdoctoral Science Foundation of China (Grant No. 20110491366)the State Key Laboratory of Tribology of Tsinghua University (Grant No. SKLTKF10B04)
文摘Finite element method(FEM) was used to investigate the effect of the number of layers on the bond strength for the brittle coating/substrate materials at contact load condition,which has not been addressed previously.The maximum shear stress was used to act as the criterion of the bonded strength.This paper discussed the relationship between the number of coating layers and the maximum shear stress of the layer/substrate interface.Firstly,the results of the FEM and the Hertz analytical method were compared to verify the accuracy of the FEM model.It was found that with the increase in the number of coating layers,the position of the suddenly changed stress along the z axis is transformed from the interface to the external surface of the coating.Finally,the increase in the number of layers contributes to the decrement of the stress along the x axis.
