考虑松动区高度影响的城市深埋隧道松动土压力研究

Urban Deep-buried Tunnel Loosening Earth Pressure Considering the Loos-ening Zone Height Influence

传统的太沙基松动土压力理论是基于浅埋地层这一基本假定建立的,其对于城市深埋地层不具备适用性。在深埋土质隧道土拱效应完全发挥情况下,考虑主应力轴旋转修正无黏性土侧压力系数计算方法;基于有限差分数值平台开展不同埋深、不同内摩擦角下的有限元模拟确定深埋黏性土层的破坏模式。给出考虑主应力轴旋转和内摩擦角对松动区高度影响的深埋无黏性土、黏性土地层的松动土压力计算公式,以实现对城市深埋土质隧道上覆土压力的准确计算。修正公式计算结果与文献、数值模拟结果对比分析结果表明:在深埋情况下,无黏性土层松动土压力修正公式计算结果与文献结果吻合良好;土体强度参数会对黏性土松动区高度造成影响,即随着内摩擦角的增大,松动区高度不断减小;黏性土层松动土压力修正公式计算结果与数值模拟结果吻合良好。

The conventional theory of Terzaghi loosening earth pressure is developed on the basic hypothesis of shallow-buried tunnel,which is not applicable to urban deep-buried tunnel.Under the condition that the soil arching of deep-buried soil tunnel is fully developed,the calculation method for lateral pressure coefficient of cohesionless soil is modified by considering the rotation of principal stress axis.Based on finite difference numerical platform,the failure modes of deep-buried cohesive soil of different buried depths and internal friction angles are determined by finite element simulation.The calculation formula for loosening earth pressure of deep-buried cohesionless soil and cohesive soil layer considering the influence of principal stress axis rotation and internal friction angle on loosening zone height is given,in order to achieve accurate calculation of the overburden earth pressure on urban deep-buried tunnel.The calculation results of the modified formula are compared with literature and numerical simulation results,and the results show that in the case of deep-buried tunnel,the calculation results of the modified formula for cohesionless soil are in accordance with literature;the soil strength coefficients will affect the loosening zone height of cohesive soil,meaning that,the loosening zone height decreases with the increase of internal friction angle;the calculation results of the modified formula for cohesive soil are in accordance with the numerical simulation results.