初始应力下巷道围岩瞬态P波扰动响应研究

Study on transient P-wave disturbance response of surrounding rock under initial stress

为了解决工程现场中动态扰动对巷道围岩稳定性造成影响的问题,揭示动力扰动对地下结构破坏的理论机理,基于波函数展开法,求解了无初始应力状态下圆形巷道周边的动态应力分布。并通过LS-DYNA有限元软件研究了弹性巷道围岩中初始应力对动态应力集中的影响。在垂直方向应力为30 MPa和孔洞轴向方向应力为10 MPa条件下,分别取不同侧压系数,得到在无初始应力状态下和有初始应力状态下的圆形巷道周边的动态应力集中因子(DSCF)以及动态应力放大系数(DSAF)的分布。研究表明初始应力对圆形巷道动态响应的影响并不是简单的线性叠加,而是一个动态的应力平衡过程;初始应力状态下,DSCF的分布与无初始应力分布大致相同,在侧压系数为1时,孔边的最大DSCF较无初始应力状态下的增大了0.3左右;在初始应力状态下,孔边的应力变化会出现不规律的波动,在动载应力下降段,孔边将出现主应力的偏转和应力释放,导致急剧的应力变化;孔洞周边围岩的DSAF随侧压系数的增大而减小。

In order to solve the problem of dynamic disturbance affecting the stability of tunnel surrounding rock in engineering sites and reveal the theoretical mechanism of dynamic disturbance on underground structure failure,based on the wave function expansion method,the dynamic stress distribution around circular tunnels in the state of no initial stress is solved.And the influence of initial stress on dynamic stress concentration in the surrounding rock of elastic tunnels is studied by using LS-DYNA finite element software.The distribution of dynamic stress concentration factor(DSCF)and dynamic stress amplification factor(DSAF)around the circular roadway without and with initial stress state are obtained under the condition of vertical stress of 30 MPa and axial stress of 10 MPa.The results show that the effect of initial stress on dynamic response of circular roadway is not a simple linear superposition,but a dynamic stress balance process.Under the initial stress state,the DSCF is almost the same as that without initial stress.When the pressure measurement coefficient is 1,the maximum DSCF at the hole edge increases by about 0.3.In the initial stress state,the stress change of the hole edge will appear irregular fluctuations.In the dynamic load stress drop section,the main stress deflection and stress release will appear at the hole edge,resulting in sharp stress changes.The DSAF of surrounding rock decreases with the increase of lateral pressure coefficient.