1. School of Mechanics and Civil Engineering,China University of Mining and Technology (Beijing),Beijing　 100083,China; 2. The Government of Machik- ou Town,Changping District,Beijing　 102200,China

为了掌握巷道(隧道)围岩在开挖卸荷条件下的变形规律及破坏机制,实现对巷道开挖卸荷过程中真实加、卸载过程的模拟,采用具有自主知识产权的巷道围岩开挖卸荷模型试验系统,对高强石膏材料制作的小型围岩试件(厚壁圆筒:高290 mm、外径200 mm、内径100 mm)进行了巷道开挖瞬态、缓慢卸荷以及破坏的模拟试验。试验过程中采集到围岩试件轴向和切向2个方向的应变随时间的变化关系,获得了开挖卸荷全过程的应变-时间曲线。试验结果表明:(1)围岩试件的轴向基本都呈现受压状态,部分测点出现拉压变化,轴向应变在缓慢卸荷时可充分展现其弹塑性变形,而在瞬态卸荷时大部分的变形是在卸荷后慢慢释放的,卸荷结束后围岩试件有轻微蠕变现象;(2)围岩试件的内测切向应变大于外侧,即离洞壁距离越远,应变越小,试件在卸荷过程中向内膨胀;(3)同一测点,卸荷过程中切向应变大于轴向应变,切向应变对卸荷过程的反应更敏感,具有瞬时性,在围岩变形中起主导作用;(4)卸荷破坏时,切向应变先于轴向应变发生突变,即围岩试件破坏方向朝向洞内,试件破坏主要是环向剪切破坏伴随有竖向劈裂。

In order to grasp the deformation law and failure mechanism of surrounding rock of roadway under the con- dition of excavation and unloading,realize the simulation of actual loading and unloading process during un-loading of roadway excavation,a roadway surrounding rock excavation unloading model test system with inde-pendent intellectual property rights was used to simulate transient excavation,slow unloading and failure of tunnel excavation with the small wall rock specimen (thick cylinder:height 290 mm,outer diameter 200 mm,inner diameter 100 mm) made of high- strength gypsum materials. During the test,the strain of the surrounding rock specimen in both axial and tangential di- rections was collected and the strain-time curve of the whole process of excavation unloading was obtained. The test re- sults show that:① the axial direction of the surrounding rock specimen basically shows the state of compression,and some of the measuring points show the change of tension and compression. The axial strain can fully demonstrate the elastic-plastic deformation when it is unloaded slowly. Most of the deformation is slowly released after unloading,and at the end of unloading the specimen has a slight creep phenomenon;② in the surrounding rock specimens,the meas- ured tangential strain is greater than the outside,that is,the farther away from the wall. The smaller the strain is,the specimen expands inwards during the unloading process;③ at the same measuring point,the tangential strain during unloading is greater than the axial strain,and the tangential strain is more sensitive to the unloading process and has instantaneous response. Rock deformation plays a leading role;④ when unloading failure,the tangential strain changes prior to surrounding rock failure,that is,the failure direction of the surrounding rock specimen faces the hole,and the failure of the specimen is mainly the circumferential shear failure accompanied by the vertical cleavage crack.

HOU Gongyu,LI Xiaorui,LIANG Hongyao,et al. Study on deformation and failure of high-strength gypsum surrounding rock specimens (thick-walled cylinder) simulating roadway excavation[J]. Journal of China Coal Society,2018,43(3):616-625.