爆炸荷载下青砂岩动态起裂韧度的测试方法

为了研究爆炸荷载下青砂岩I型裂纹动态断裂韧度的测试方法，利用内部中心单裂纹圆盘（internal center single crack disc，ICSCD）试样进行了爆炸试验研究。试样由外径为400 mm、内部加载孔径为40 mm、预制裂纹长为60 mm的青砂岩制成。利用同步触发器实现圆盘中心起爆，并同步触发超动态应变仪，通过径向应变片获取爆炸应变曲线、裂纹尖端的环向应变片获取裂纹起裂时刻。以实测爆炸应变曲线为参量，应用Laplace变换推导出试样加载孔壁应力时程曲线表达式，并用数值反演法得出其数值解。利用ANSYS有限元软件，建立数值计算模型，通过相互作用积分法得出了在爆炸荷载作用下砂岩的I型动态应力强度因子曲线。研究结果表明：（1）ICSCD试件能够很好地用来测试岩石的动态起裂韧度；（2）炮孔周边的应力可以通过拉普拉斯变换的数值反演方法得到；（3）通过试验-数值法能稳定计算出ICSCD砂岩构型的动态起裂韧度，其最大误差仅为7%。

Study of testing method for dynamic initiation toughness of blue sandstone under blasting loading

In this paper, an internal central single-cracked disk (ICSCD) specimen was proposed for the study of dynamic fracture initiation toughness of sandstone under blasting loading. We conducted blasting tests on an ICSCD specimen fabricated from a blue sandstone disc (400 mm in diameter) with a crack (60 mm in length), obtained a blasting strain-time curve from the radial strain gauges fixed around the blast hole, determined the fracture initiation time with the circumferential strain gauges placed around the crack tip, and then derived the stress history on the blast hole of the sandstone specimen from the measured strain curve through the Laplace transform. Furthermore, we obtained the numerical solutions using numerical inversion, establishing a numerical model using the finite element software ANSYS, and derived Type I dynamic stress intensity factor curves of the sandstone under blasting loading by the mutual interaction, with the results achieved: (1) the ICSCD specimen can be used to measure the dynamic initiation fracture toughness of rocks; (2) the stress on the blast hole wall can be obtained by the Laplace numerical inversion method; (3) the dynamic initiation fracture toughness of the ICSCD sandstone specimen can be calculated by the experimental-numerical method with an error below 7%.