深埋隧洞开挖稳定性评价方法对比研究

引入2种等效超载法,并结合强度折减法和超变形法,对深埋隧洞初次开挖支护的稳定性进行渗流-应力耦合计算分析。结果表明,考虑增加初始孔隙水压力和应用弹塑性损伤本构模型均会增加破坏区的范围和最大值;等效超载法与强度折减法产生的破坏区范围差异性较大,且得到的安全系数要大于强度折减法;基于弹塑性损伤模型的强度折减法得到的安全系数为1.14,考虑初始孔隙水压力和弹塑性损伤模型的容重增加法得到的安全系数为2.2。等效超载法可作为评价隧洞稳定性的方法,容重增加法与应力系数法均能同时考虑初始应力场和孔隙水压力场的超载,且应力系数法适用性更好;超变形法破坏区变化有别于其他方法,局限性较大,实际工程中可基于实际地质情况有选择性地采用基于弹塑性损伤本构模型的强度折减法或等效超载法。

Comparative Study on Stability Evaluation Methods of Deep-buried Tunnel Excavation

Combined with the strength reduction method and over-deformation method,two equivalent overload methods are used to analyze and compare the stability of the initial excavation and support of a deep-buried tunnel based on seepage-stress coupling theory.The results show that,(a)the scope and maximum value of failure zone will be increased considering the increase of initial pore water pressure and the application of elastic-plastic damage constitutive model;(b)the range of failure zone generated by equivalent overload methods and the strength reduction method is quite different,and the obtained safety factor is greater than that of strength reduction method;and(c)the safety factor obtained by the strength reduction method based on the elastic-plastic damage model is 1.14,and the safety factor obtained by the gravity increasing method considering the initial pore water pressure and the elastic-plastic damage model is 2.2.The equivalent overload method can be used as a method to evaluate the stability of tunnel,both the gravity increasing method and the stress coefficient method can consider the overload of initial stress field and pore water pressure field,and the applicability of the stress coefficient method is better.The change of failure zone of over-deformation method is quite different with other methods,and its application is limited.The strength reduction method or equivalent overload method based on elastic-plastic damage constitutive model should be selected based on the actual geological conditions during tunnel excavation construction.