列车荷载-地下水耦合作用下隧底围岩强度参数劣化规律研究

为探明列车激振荷载-地下水耦合作用下隧底围岩强度参数劣化特征及列车荷载、地下水压力、围岩级别对围岩颗粒流失影响规律,采用PFC 数值模拟方法分析不同影响因素对围岩颗粒流失量的影响规律,给出颗粒流失率计算公式; 探明不同颗粒流失率条件下围岩弹性模量、峰值强度劣化特征,得到劣化后强度参数计算公式。研究结果表明: 1)围岩自身完整程度、列车轴重、地下水压力三者均与围岩颗粒流失量呈正相关关系,且三者对颗粒流失影响程度依次降低; 2)颗粒流失率与列车轴重、地下水压力三者之间呈二次曲面关系,给出围岩颗粒流失率计算公式; 3)随颗粒流失率增加,围岩应力应变全曲线中弹性变形阶段逐渐减小, 塑性变形阶段逐渐扩大,全曲线特征由弹塑性逐渐向塑性转变; 4)围岩弹性模量、峰值强度均随颗粒流失率增加呈指数衰减,得到劣化强度参数计算公式。

Strength Degradation of Surrounding Rock at Inverted Arch of Tunnel under Coupling Action of Train Load and Groundwater

In order to investigate the strength degradation characteristics of surrounding rock at inverted arch of tunnel under the coupling action of train load and groundwater, the influences of different factors, i. e. train load, groundwater pressure, surrounding rock grade, etc. , on the practical loss of surrounding rock are analyzed by PFC simulation; and the calculation formula for particle loss rate is obtained. Meanwhile, the degradation characteristics of surrounding elastic modulus and peak strength are discussed, and the calculation formula for strength parameters after degradation is obtained. The study results show that: (1) The particle loss volume of surrounding rock is positively correlated to the surrounding rock integrity, train load and groundwater pressure; and the surrounding rock integrity affects the particle loss volume of surrounding rock greatly, followed by train load and groundwater. (2) The relationships among particle loss rate, atrain load and groundwater pressure is quadric; and the calculation formula for particle loss rate of surrounding rock is proposed. (3) The elastic deformation phase gradually disappeared and the range of plastic deformation gradually expanded with the increased ration of particle loss, which indicates the gradual transition from elastic-plastic to plastic. (4) With the particle loss rate increase, the elastic modulus and peak strength of surrounding rock decrease exponentially; and the calculation formula for degenerated strength parameters is obtained.