岩块锚固机理的模拟试验研究

Simulation on anchorage mechanism of rock mass

为研究锚杆对深部巷道围岩的作用机理,利用自制三轴加载物理相似模拟试验系统,进行了加锚与不加锚完整和预裂岩石试件(400 mm×400 mm×400 mm)的加载对比试验,比较了锚杆预紧力和支护密度对完整和预裂岩石试件的锚固效果,分析了锚杆对完整和预裂岩石试件的作用时机。研究结果表明:无论完整试件或预裂试件,锚杆支护均可提高其峰值强度,尤其预紧力对提高峰值强度的作用明显,对预裂试件峰值强度的提高幅度比完整试件更大。加锚预裂试件相对于无锚预裂试件其应力应变曲线从竖向加载一开始就相对滞后;而加锚完整试件相对于无锚完整试件,从竖向加载开始到试件峰前连续变形阶段,应力应变曲线差别不大,无锚完整试件在达到其峰值强度后,承载力开始下降,而此时加锚完整试件承载力继续增大,只是增速有所减缓。对于预裂试件,锚杆承载具有即时性,即与试件基本同时承载;而对于完整试件,锚杆承载则体现出延时性,即锚杆在岩体发生破坏、产生较大变形后才开始承载。因此,锚杆支护难以阻止巷道围岩的塑性变形和塑性区的形成,深部巷道的围岩控制理念应由变形控制向稳定控制转变。深部巷道锚杆的主要作用一是提高破碎岩体的残余强度,二是阻止破碎岩体裂隙的后续扩张,从而提高围岩的整体性和完整性,达到维护巷道稳定的目的。

In order to study the functioning mechanism of anchor bolts on the surrounding rocks of deep roadway,a comparison study of intact and pre-cracked rock specimens(400 mm×400 mm×400 mm)with anchors and without anchors was carried out by using a self-made triaxial loading physical similarity simulation system.The anchoring effect of bolt pre-tightening force and supporting density on intact and pre-cracked rock specimens was compared,and the function timing of anchor bolts on intact and pre-cracked rock specimens was analyzed.The results show that the anchor bolts can improve the peak strength of both intact and pre-cracked specimens.Especially,the pre-tightening force has an obvious effect on improving the peak strength of pre-cracked specimens,and the increase of peak strength of pre-cracked specimens is greater than that of intact specimens.The stress-strain curve of pre-cracked specimens with anchors lags behind that of pre-cracked specimens without anchors from the beginning of vertical loading.However,compared with the intact specimens without anchors,the stress-strain curves show little difference from the vertical loading to the pre-peak continuous deformation stage.The bearing capacity of the intact specimens without anchors begins to decline after reaching its peak strength,while the bearing capacity of the intact specimens with anchors continues to increase with a slowing down increase rate.For the pre-cracked specimens,the anchor bolt bearing capacity is instantaneous,which means it bears the load at the same time with the specimens.However,for the intact specimens,the bearing capacity of the bolt is delayed,which means the bolt begins to bear only after the rock mass is damaged and deformed significantly.Therefore,the bolt support is difficult to prevent the plastic deformation of surrounding rocks and the formation of plastic zone.The control concept of surrounding rocks in deep roadway should be transformed from deformation control to stability control.The main function of anchor bolts in deep dynamic pressure roadway is to improve the residual strength of broken rock mass and prevent the subsequent expansion of fractures in it,so as to improve the integrity of surrounding rocks and maintain roadway stability.