Abstract The influence of ground surface tension cracks on surrounding rock pressure of shallow-buried loess tunnels is not considered in the current tunnel design code. The paper first summarizes the deformation characteristics of surrounding rocks and the composition characteristics of failure slip plane in shallow-buried loess tunnels,then it constructs the calculation model of surrounding rock pressure based on the limit equilibrium theory, deduces the calculation formulas of tension cracking depth and tunnel surrounding rock pressure, and discusses the relationship between calculation results and influencing parameters, and finally, by comparing with the measured data and the existing theoretical calculation results, it proves the rationality of the calculation method. The research results show that due to the existence of ground surface tension cracks, both the normal stress and shear stress on the inclined shear plane in the soil mass would increase compared with that without considering surface tensile cracks, the fracture plane would share more loads generated by the overlying soil masses, and the surrounding rock pressure of the shallow-buried loess tunnel would be significantly reduced. The calculation curve of surrounding rock pressures in the proposed new model presents a form of parabola changing with the increase of buried depth, and the peak value of the curve can provide a reference for the demarcation of deep or shallow buried depth of a tunnel. Compared with the traditional methods, the calculation results of the new model are closer to the measured values.
Abstract：
The influence of ground surface tension cracks on surrounding rock pressure of shallow-buried loess tunnels is not considered in the current tunnel design code. The paper first summarizes the deformation characteristics of surrounding rocks and the composition characteristics of failure slip plane in shallow-buried loess tunnels,then it constructs the calculation model of surrounding rock pressure based on the limit equilibrium theory, deduces the calculation formulas of tension cracking depth and tunnel surrounding rock pressure, and discusses the relationship between calculation results and influencing parameters, and finally, by comparing with the measured data and the existing theoretical calculation results, it proves the rationality of the calculation method. The research results show that due to the existence of ground surface tension cracks, both the normal stress and shear stress on the inclined shear plane in the soil mass would increase compared with that without considering surface tensile cracks, the fracture plane would share more loads generated by the overlying soil masses, and the surrounding rock pressure of the shallow-buried loess tunnel would be significantly reduced. The calculation curve of surrounding rock pressures in the proposed new model presents a form of parabola changing with the increase of buried depth, and the peak value of the curve can provide a reference for the demarcation of deep or shallow buried depth of a tunnel. Compared with the traditional methods, the calculation results of the new model are closer to the measured values.
LAI Hongpeng1 WANG Bin1 LIU Yuyang2
.A Calculation Method of Surrounding Rock Pressure of Shallow-buried Loess Tunnels under Considering Ground Cracking[J] MODERN TUNNELLING TECHNOLOGY, 2021,V58(6): 95-101
2021, Vol. 58 