拉伸条件下锚杆对含表面裂隙类岩石试样加固效应试验研究

Experimental study on reinforced effect of bolts on 3D surface fractured rock under uniaxial tension

选用改性橡胶粉-水泥砂浆来模拟真实岩石,用玻璃纤维增强塑料作为锚杆材料,研究锚杆对三维表面裂隙岩体的加固止裂效果。结果表明,锚杆提高了裂隙岩体的变形模量和单轴抗拉强度,变形模量随锚固角的增大而增大,而单轴拉伸随锚固角的增大先增大后减小,当锚固角β=45°时,锚杆对单轴抗拉强度的提高幅度最大;锚杆通过其抗滑移和抗剪切性能使裂隙岩体避免发生脆性破坏,并且在预置裂隙起裂之后存在不同程度的残余强度;单轴拉伸条件下加锚或无锚裂隙试件的破坏均以预置裂纹尖端为突破口产生翼裂纹,其扩展方向大致与轴向拉应力方向垂直。当锚固角小于某个临界值时,会有次生裂纹产生;拉伸条件下,含裂隙试件的破坏机制是张拉型裂纹的贯通作用。

Modified rubber powder-cement mortar is used to simulate the real rock.Glass fiber reinforced plastics（GFRP） is chosen as the bolt material.The reinforced and crack arresting effect of bolts on 3D surface fractured rock is studied.The experimental results show that the bolts obviously enhance the deformation modulus and uniaxial tensile strength.The deformation modulus increases with the increase of the anchor angles.The uniaxial tensile strength increases firstly,then decreases with the increase of the anchor angles,and it has the largest increment when the anchor angle β=45°.Due to the anti-slip and anti-shear properties of bolts,the fragile failure can be avoided for the fractured rockmass.Compared with the fractured specimens without bolts,there still exist different residual strengths after the pre-existing crack initiation for those specimens reinforced by the bolts with different anchor angles.Under uniaxial tensile conditions,the failure of reinforced specimens and non-reinforced specimens begins with the wing cracks at the tips of pre-existing cracks and the growth direction of wing cracks is approximately vertical to axial tensile stress.Secondary cracks appear when the anchor angle is smaller than a critical value.Under uniaxial tensile conditions,the failure mechanism of fractured specimens is the coalescence role of tensile crack.