锚杆抑制临空结构面扩展的试验研究

EXPERIMENTAL STUDY ON EFFECTS OF ROCK BOLTS RESISTING GROWTH OF SURFACE STRUCTURAL PLANES

通过试验研究受压作用下临空结构面的扩展特点以及锚杆的作用。试验中,模型材料为石膏,用钢板预制生成的裂纹来模拟结构面,采用铜丝、铝丝、保险丝来模拟不同刚度的锚杆。采用应变片来量测裂纹尖端的应力集中现象,利用电阻应变仪来读取应变与压力值。试验在压力机上完成。研究结果表明,随着压力的增大,临空结构面存在翼裂纹的张拉破坏与次生裂纹的剪裂纹破坏两种形式。结构面的倾角越大越容易产生翼裂纹的扩展;小倾角结构面更容易产生次生裂纹的剪切破坏方式;锚杆作用可增强结构体的力学性能,降低裂纹尖端的应力集中现象,提高裂纹尖端裂纹的起裂荷载;锚杆并不改变裂纹的起裂角度,但使翼裂纹扩展的方向向深部偏移,从而加大因翼裂纹而造成的剥离体的厚度,减缓翼裂纹的扩展速度。试验在一定程度上揭示了锚杆对监空结构面加固机制。

The growing modes of surface structural planes under compressive load and the function of the bolts are studied by experimental methods.In the experiment,the model material is gypsum.Structural planes are modeled by cracks,which are prefabricated by iron plates.Brass wires,aluminous wires and fuses are used to model the bolts with different stiffness.Strain gauges are applied to measure the stress intensity around the crack tips.Strain and pressure are measured by electrical resistance strain gauges.The experiment is accomplished by pressure machine.The results demonstrate that,with the increase of compressive load,there are two propagation modes at the tips of the surface structural planes:wing cracks and secondary cracks.With the increase of the inclination angle between the structural plane and the surface,the propagation of wing crack becomes more easily.The secondary cracks may be more popular for the case of the small inclination angles.The role of bolts is to improve the performance of the structural mass,weaken the stress intensity at the crack tips and increase the crack propagating loads.The bolts do not change the crack initial angle,but they can affect the internal extending path of the wing crack.This will increase the thickness of separated bodies and reduce its spreading speed.The experiment discovers the mechanism that the bolts reinforce the surface structural planes to some extent.