节理对爆生裂纹扩展影响的试验研究

Experimental study on the effects of joints on the blasting induced cracks propagation

采用模型试验方法,结合新型数字激光动态焦散线试验系统,比较了不同炮孔与节理间距下节理处起裂的动态行为,研究了节理对爆生裂纹扩展的影响。结果表明,由于节理结构的细观差异,试件的破坏形态表现出多样性。根据节理处起裂时段的差异,节理处起裂形式有2种,形式Ⅰ:在爆生裂纹扩展至节理之后,节理处起裂并扩展;该种起裂形式下,爆生裂纹对节理的直接作用是节理处起裂的主要原因,炮孔到节理的距离对节理处起裂裂纹的偏移距离影响不大。形式Ⅱ:在爆生裂纹扩展至节理之前,节理处已经起裂并扩展;该种起裂形式下,爆炸应力波对节理的作用是节理处起裂的主要原因。节理处裂纹的整体偏移范围由这两种起裂形式决定。试件的不同破坏形态在裂纹扩展的应力特征上表现出差异性和复杂性。

By model test with the new digital laser dynamic caustics(DLDC) experimental system,the dynamic behaviors of crack initiation at joints were compared in condition of different intervals between boreholes and joints.The effects of joints on the blasting induced cracks propagation were studied.It is shown that the failure forms of test specimens are various due to the mesoscopic differences among joint structures.There are two forms of crack initiation at joints according to the different crack initiation time.Form 1:crack at the joint doesn't be initiated until the blasting induced crack reaching to the joint.In this form,the direct action of blasting induced cracks on joints is the primary cause of crack initiation at joints.The offset distance of the crack initiated at the joint has little to do with the distance between borehole and joint in such form.Form 2:crack at the joint has already been initiated and propagated before the blasting induced crack reaching to the joint.In this form,the action of blasting stress waves on joints is the primary cause.The overall scope of the offset distance of crack at the joint is determined by these two forms.Different failures of specimens show various discrepancies and complexities in the aspect of crack stress characteristics.