矩形顶管顶进过程中的背土效应OA

To address the problem of the soil-carrying effect,a new criterion for soil-carrying failure was proposed.Firstly,settlement monitoring data from practical engineering projects were analyzed to identify the soil zone affected by the soil-carrying effect.It was defined along the jacking direction as two upward-extending trapezoidal regions with an arc-shaped sliding surface at the front boundary.Secondly,based on four reasonable assumptions,the soil-carrying mass was simplified,and a 3D mechanical failure model for soil-carrying during rectangular pipe jacking was established,from which the failure criterion was derived.Thirdly,a practical engineering case was analyzed to perform a parametric sensitivity study,revealing the relationships between the soil-carrying effect and the jacking length,burial depth,and soil mechanical parameters.Finally,the critical friction coefficient at failure as well as the minimum cover depth required to prevent soil-carrying failure under different geological conditions were obtained.The results show that the critical pipe-soil friction coefficient increases with increasing burial depth,soil cohesion and internal friction angle,and decreases with increasing jacking length.A critical cohesion exists in the soil-carrying failure process.When the cohesion exceeds 12.5 kPa,the minimum burial depth decreases with increasing jacking distance,whereas the opposite trend is observed when the cohesion is lower than 12.5 kPa.In cohesionless soils,the stability of the soil-carrying mass is jointly controlled by the internal friction angle and the jacking length,and the minimum burial depth is highly sensitive to the jacking distance.When the jacking length exceeds 20 m,the minimum burial depth increases significantly,indicating that increasing the cover thickness or effectively reducing the pipe-soil friction is required to prevent overall soil-carrying failure.