Simulation on anchorage mechanism of rock mass

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.