基于PFC3D仿真重演的加载及卸载岩爆破坏特征研究

以兰-海高速公路桐梓隧道灰岩为研究对象，进行室内力学试验，并基于三维颗粒流程序PFC（particle flow code）进行加载和卸载岩爆试验数值模拟，得出不同应力状态下岩样的细观破坏特征。研究结果表明： 1）加载试验中岩石应力变化、颗粒位移、黏结破坏特征及能量变化情况均表现出3个阶段，即弹性阶段、屈服阶段和破坏阶段。2）岩石加载强度随着初始应力的增大而增大，岩石储存的极限应变也随之增大。3）应力越大，卸载试验岩爆倾向及强度越大，这是由于岩石破坏时应力由卸载面转移到内部，导致岩石内部应力集中；在其他条件不变的情况下，初始应力越大卸载岩爆强度越大，径向应力增大对硐室围岩稳定性有着更不利的影响。4）岩石加载和卸载条件下岩石的破坏具有较大区别。

Numerical Simulation of Loading and Unloading Rockburst Failure Characteristics Based on PFC3D

The laboratory mechanical test is carried out on limestone of Tongzi Tunnel on Lanzhou Haikou Highway, and the numerical simulation of loading and unloading rockburst test is carried out by three dimensional particle flow program particle flow code（PFC）, which helps to obtain the meso failure characteristics of rock samples under different stress states. The results show that: (1) The rock stress variation, particle displacement, bond failure characteristics and energy variation of rock during loading test show 3 stages, i.e. elastic stage, yield stage and failure stage. (2) With the increase of initial stress, the loading strength of rock increases, and the ultimate strain of rock increases. (3) The greater the stress, the greater the rockburst strength during the unloading test, resulting from stress concentration inside the rock induced by the stress transfers from the unloading surface to the interior during rock failure; with other conditions unchanged, the higher the initial stress, the greater the unloading rockburst strength; and the increase in radial stress will have a more adverse effect on the stability of the chamber rock. (4) The failure modes of rock under loading and unloading conditions are quite different.