爆炸荷载下含预裂缝的裂纹扩展实验研究

预裂爆破技术目前广泛应用于爆破工程中，为了探究预裂爆破形成的预裂缝对爆生裂纹和原生裂纹动态断裂特性的影响，基于数字激光动态焦散线实验开展了一系列研究，获得了裂纹扩展的时实动力学参数。研究结果表明:预裂爆破形成的预裂缝可以阻挡爆生裂纹向保留岩体内扩展，加大被爆岩体的损伤;其两端产生的翼裂纹向保留岩体扩展，且扩展长度随着预裂缝长度的增加而增大;长度较短的预裂缝(L=20~80 mm)，对保留岩体内原生裂纹扩展有促进作用，只有当预裂缝长度增加到一定程度(L=100 mm)，才会对保留岩体内原生裂纹扩展有抑制作用，预裂缝A长度L=100 mm时，其B裂纹扩展长度为无预裂缝A模型时的21%，Bz和By扩展速度均值为无预裂缝A时的0和64.8%;当有预裂缝存在时，原生裂纹两端翼裂纹的起裂时间随着预裂缝长度增加而增加，当预裂缝长度增加到一定程度(L=100 mm)，迎爆侧翼裂纹没有起裂，By起裂时间推迟到和无预裂缝时一样的150 μs;原生裂纹迎爆侧翼裂纹断裂韧度小于背爆侧断裂韧度;当有预裂缝存在时，原生裂纹两端起裂韧度均小于无预裂缝时的起裂韧度，且随着预裂缝长度增加迎爆侧翼裂纹起裂韧度降低;原生裂纹两端应力强度因子峰值随着预裂缝长度增加而减小。

Experimental study on crack propagation with pre crack under explosion load

Presplit blasting technology is currently widely used in blasting engineering.In order to investigate the effect of pre crack formed by split blasting on the dynamic fracture behavior of blasting cracks and original cracks,a series of studies were carried out based on the digital laser dynamic caustic experiment.The real time dynamic parameters of crack propagation were obtained.The results show that the pre crack can stop blasting cracks from expanding to the retained rock mass and increase the damage of the explosive rock mass.The wing cracks generated at the both ends of the pre crack expand to the retained rock mass.As the pre crack length increases,the wing crack propagation length increases.The shorter pre crack (L=20-80 mm) can promote the propagation of the original crack in the retained rock mass.Only when the pre crack length increases to a certain degree (L=100 mm),it can inhibit the expansion of the original crack in the retained rock mass.When the length of the pre crack A is 100 mm,the crack propagation length of B is 21% comparing with no pre crack A model,and the average speed of Bz and By is 0 and 64.8% without pre crack A.When the pre crack exists,the crack time of the ends of the primary crack increases with the increase of pre crack length.When the pre crack length increases to a certain extent (L=100 mm),explosive flank crack does not crack,By crack initiation time is delayed to the same 150 μs as without pre crack.Fracture toughness of explosive flank crack is less than fracture toughness of backside flanking crack.When the pre crack exists,the fracture toughness of the ends of the primary crack is less than that of the non pre crack,and the fracture toughness of explosive flank crack decreases with the increase of the pre crack length.The peak of the ends of the primary crack stress intensity decreases with the increase of pre crack length.