预裂锚固体力学特性及锚固机理

Experimental study on mechanical properties of anchorage body and on anchorage mechanism

为研究锚杆对深部巷道围岩的控制作用,通过制作三轴加载物理相似模拟试验系统,分析了锚杆支护强度、锚杆预紧力对预裂试件的锚固效果并构建了劈裂板梁结构模型。试验结果发现:无锚杆支护时,试件表现出脆性破坏;随锚杆支护强度及预紧力增大,试件承载能力得到提高且其应力应变曲线具有较好的屈服平台,表现出明显的延性特征;试件垂向位移量相近时,随锚杆支护强度及预紧力增大,试件体应变变小;试件主要沿最大主应力方向(垂直方向)发生劈裂破坏,拉伸裂纹集中在临空面附近,剪切裂纹则分布在远离临空面的区域,在锚杆的作用下形成类似板梁结构,板梁挠度不仅与试件自身力学性能、外载荷有关,还与板梁长度、板梁结构形式有关。锚杆支护密度的增大改变了板梁结构形式,减小了板梁挠度,而较大预紧力能够降低板梁之间的离层量,相应的试件非连续变形得到控制。由此可知,锚杆支护不仅可提高破裂围岩的承载能力,而且可有效控制破裂围岩的非连续变形,从而提高深部巷道围岩的连续性和整体稳定性。

A triaxial loading physical similarity simulation test system was developed for studying the anchorage effect of bolt on the surrounding rock of deep roadway,the anchoring effect of bolting density and pretension on pre-splitting specimen was analyzed,and the plate-beam model was established.The test results show that the specimens appear brittle failure without bolting support,its post-peak bearing capacity increases and shows obvious ductility characteristics with the increase of bolting support density and pre-tightening force.When the displacement of specimens in the vertical direction is similar,its volumetric strain decreases with the increase of the bolting support density and pre-tightening force.The splitting failure occurs mainly along the direction of maximum principal stress(vertical direction).The tensile cracks are concentrated near the free surface and the shear cracks are concentrated far away from the free surface.Under the action of bolts,a similar plate-beam structure is formed,whose deflection is not only related to the mechanical properties and external loads,but also to the length and form of the plate-beam.The increase of bolting support density changes the form of plate-beam structure and reduces its deflection.The larger pre-tightening force can reduce the separation between plate-beams,and the discontinuous deformation of specimens is reduced.Therefore,the effect of bolt on surrounding rock of deep roadway is obvious,which can change the stress bearing condition of anchorage surrounding rock,can enhance the integrity and flexibility of surrounding rock,and can effectively control the discontinuous deformation of fractured surrounding rock.