大量的工程建设都是在岩体中进行的，岩体的力学性能的优劣往往是由岩体内部的节理与微裂纹的影响程度所决定的，岩体在人为动力扰动下动态力学性能研究是目前国内外研究热点。钻爆法作为岩体开挖的主要手段，产生的动荷载有别于其他动荷载：爆炸荷载持续时间往往短到μs量级，而峰值却达到GPa量级，这类动态荷载的加载都是从岩石的局部开始再传播到整体，其尺寸相关性非常明显。因此，研究爆炸荷载下含缺陷岩石的动态响应有着明确的现实意义。本文以爆炸应力波波长为基本设计参量，设计了不同预制裂纹长度与不同边界反射波入射角度的I型断裂韧度测试试样，实现了不同加载率的动态断裂韧度测试。采用实验-数值法计算得到了爆炸应力波下，不同试样构型的动态应力强度因子曲线，从时间域上分析了裂纹面上首波与面波的叠加与分离；运用AUTODYN软件对不同预制裂纹长度的试样裂纹面产生的速度场与裂纹尖端附近张开位移进行了数值重演，得到了首波波阵面在空间域上的形态；通过改变试样的微小尺寸变化，讨论了动态断裂韧度测试值与试样几何尺寸的敏感性。本文的研究工作主要分为以下几个部分： (1)爆炸荷载上升沿与下降沿时间受传播介质的物理性质、炸药量以及距离爆炸点的位置影响，与冲击荷载相比，在动态断裂测试中爆炸荷载这种短波荷载体现了明显的尺寸相关性；爆炸荷载在裂纹面形成了纵波、横波、首波与面波，首波是由于爆炸纵波在裂纹面不能满足自由面零应力的条件而产生的，爆炸纵波与爆炸横波以一定入射角度在裂纹面叠加形成了面波；由于首波与面波的波速差，预制裂纹长短会影响首波与面波的叠加程度，从而影响加载率；通过AUTODYN软件对爆炸荷载在裂纹面产生的速度场与裂纹尖端位移变化进行了模拟，得到了首波波阵面在空间域的形态为夹角为63°的等腰三角形，裂纹起裂时靠近裂尖端监测点速度与位移时程曲线出现了明显的不连续性。 (2)利用爆炸荷载下岩体中不产生裂隙圈的最小半径公式，提出了符合研究爆炸应力波的试样加载方式；采用霍普金森压杆对PVDF压力计进行了动态标定，标定系数为14.5PC／N，给出了水介质透射到加载孔壁的爆炸应力计算公式；全面介绍了爆炸应力波实验测试系统组成部分以及相关原理，并通过预实验验证了测试系统的可靠性；针本文研究的问题，采用相互作用积分法来计算爆炸荷载下裂纹尖端的应力强度因子，并通过经典Chen问题对所采用的方法进行验证；对AUTODYN软件模拟爆炸动态过程进行了介绍，确定了砂岩试样材料采用线性状态方程、炸药材料采用JWL状态方程，选择最大主应力准则模拟裂纹扩展过程，根据加载率与动态抗拉强度的幂函数关系确定了试样的动态抗拉强度，对不同尺寸的网格进行了合理性验证，确定了单元的尺寸为0.5㎜。 (3)为了使首波与面波达到不同程度的叠加，以实测爆炸荷载曲线的波长为基本参量，对试样预制裂纹长度进行设计；利用设计的不同长度预制裂纹与不同反射波入射角度构型进行了爆炸实验，得到了试样预制裂纹的几何尺寸可以控制首波与面波的叠加，裂纹长度与反射波的入射角度能够控制加载率的结论，本次可控制加载率范围为1036 GPa×m〓×s⁻¹～4383GPa×m〓×s⁻¹。 (4)通用函数适用于扩展路径为直线的裂纹扩展韧度进行计算，当扩展路径为折线时采用分形模型修正法计算动态扩展韧度更加准确；在预制裂纹长度变化的测试试样中动态扩展韧度随着裂纹的扩展速度增加而增加体现了速度增韧，而随着加载率的增加扩展韧度呈下降趋势，在反射波不同入射角度的测试试样中随着入射角度的变化有最危险角度此时扩展韧度最小，而随着加载率的增加扩展韧度反而迅速增加；通过AUTODYN软件重演了在不同时刻，裂纹面爆炸应力波的空间分布情况。首波波阵面以预制裂纹为对称轴形成顶角为63°的等腰三角形速度带，随着预制裂纹长度增加三角速度带会越来越明显，随着时间的增加首波速度带会整体衰减，裂纹面上的面波会逐渐凸显出来，在裂纹的起裂时刻，裂纹尖端出现了明显的张开速度，预制裂纹越短其加载率越高，能量更大，其裂纹面张开位移就越大；加载中心位置、预制裂纹长度、加载孔径的变化都会对起裂韧度的测试结果产生影响，加载孔径变化1㎜时其测试结果偏差值达7.1％，裂纹长度变化1㎜时其测试结果偏差值达4.5％，加载中心偏差1㎜时测试结果偏差值达3.9％，因此，试样加工完成后应对这三个尺寸进行多次测量以实际测量值来代替设计值，保证测试精度。 关键词：砂岩；爆炸首波；断裂韧度；加载率；裂纹扩展速度；

 A large number of engineering constructions are carried out in rock mass. The dynamic mechanical properties of rock under anthropogenic dynamic disturbance are domestic and international hot issues.Both the rock mass and the rock interior contain a large number of joints, cracks or microcracks.The mechanical properties of rock mass and rock are often determined by the influence of these defects.Drilling and blasting method is the main means of rock excavation, and the dynamic load generated by drilling and blasting method is different from other dynamic loads. The duration of explosive loads tend to be shortened to the magnitude of μs.while the peak of explosive loads reach the magnitude of Gpa.The loading of explosive dynamic loads is often from the part to the whole of the rock.Its size effect is very obvious.Therefore, investigation of the dynamic response of defective rock under blast loading of practical significance. In this thesis, the dynamic fracture toughness test was conducted under different loading rate.The specimen with Type I fracture toughness that have different pre-crack lengths and different incident angles of boundary reflection waves were designed by taking the load wavelength of the explosive stress wave as the basic parameter. The dynamic stress intensity factor curve of different sample configurations under the explosive stress wave was calculated by the experimental-numerical method. The superposition and separation of the first wave and surface wave on crack surface were analyzed by the time domain on the stress intensity factor curve.The velocity field generated by the crack surface of different pre-crack length specimens under the explosive stress wave and the open displacement near the crack tip was numerically reproduce by AUTODYN software.The shape of the first wavefront in the spatial domain was obtained. The sensitivity of the dynamic fracture toughness testing value to the geometrical dimensions of the specimen was discussed by changing the small dimensional change of the specimen. The research work of this paper mainly includes the following parts:The shape of the first wavefront in the spatial domain was obtained.The sensitivity of the dynamic fracture toughness testing value to the geometrical dimensions of the specimen was discussed by changing the small dimensional change of the specimen. The research work of this paper mainly includes the following parts: (1)The rising time and the falling time of the blast load are affected by the physical properties of the propagation medium, the amount of explosive, and the location of the explosion point.Explosive loads,such short-wavelength loads,have a significant dimensional dependence compared with impact loads in dynamic fracture tests.Explosive load formed a longitudinal wave, shear wave, the first wave and surface wave on the crack surface.The first wave is generated because the compressional wave of explosion cannot satisfy the condition of zero stress of free surface on the crack surface. The surface wave is superimposed on the crack surface by the detonation longitudinal wave and the detonation transverse wave at a certain incident angle.Due to the difference in wave velocity between the first wave and the surface wave,the length of the pre-crack will affect the degree of superposition of the first wave and the surface wave, thus affecting the loading rate.The velocity field of the crack surface and the displacement change of the crack tip generated by the explosion load were simulated by AUTODYN software. The shape of the first wavefront in the space domain is an isosceles triangle with an angle of 63°.When the crack tip was cracked, the velocity and displacement time history curve of the monitoring point near the crack tip will show obvious discontinuity. (2)According to the formula of the minimum radius of the rock mass without the crack ring under the blasting load, the loading method of the sample conforming to the research of the explosive stress wave was proposed. The PVDF pressure gauge for testing the magnitude of the explosion stress wave was dynamically calibrated with a calibration factor of 14.5 PC/N by SHPB test. At the same time, the calculation formula of the explosion stress transmitted into the loading hole wall by water medium was given. In the thesis, the components and related principles of the experimental system of explosive stress wave were are introduced.The reliability of the test system was verified by preliminary experiments. The research question in this thesis was calculated the stress intensity factor of the crack tip under blast loading by the interaction integral method. The interaction integral method was verified by the classical Chen problem.The simulation of the dynamic process of explosion using the AUTODYN software with numerical replay was introduced.The linear equation of state was used for the sandstone specimen, and the JWL equation of state was used for the explosive material.The maximum principal stress criterion was selected to simulate the crack propagation process. Tthe dynamic tensile strength of the specimen was determined according to the linear elastic mechanics.The rationality verification was carried out on different size grids, and the size of the unit was determined to be 0.5㎜. (3)In order to achieve the superposition of the first wave and the surface wave to different degrees, the pre-crack length was designed using the measured wavelength of the blast load curve as the basic parameter.Explosion experiments were conducted on the configurations of different lengths of pre-cracks and different incident angles of reflected wave. The geometrical dimensions of the sample pre-crack can be obtained to control the superposition of the first wave and the surface wave. It was concluded that the crack length and the incident angle of the reflected wave can control the loading rate. The controlled load rate ranges from 1036 GPa×m〓×s⁻¹ to 4383GPa×m〓×s⁻¹ in the experiment. (4)The general function can be used to calculate the fracture toughness of the crack when the expansion path is straight. When the crack propagation path is a broken line, it is more accurate to calculate the dynamic expansion toughness by using the parting model correction method. In the specimen for testing the changes of the pre-crack length, the dynamic expansion toughness increases with the increasing rate of crack growth, showing that the greater the speed, the greater the toughness. Furthermore, as the loading rate increases, the expansion toughness shows a downward trend. In the specimens for testing different incident angles of reflected waves, the smallest expanded toughness appears at the most dangerous angle as the incident angle changes. In this case, the expanding rate increases with the increasing loading rate.The spatial distribution of the explosion stress wave on the crack surface of the sample at different time points is replayed by AUTODYN software. The vibration plane of first wave forms an isosceles triangle speed band with a fixed angle of 63° with pre-cracked symmetry axis. As the pre-crack length increases, the triangle speed band will become more and more obvious. As time increases, the first wave speed band will decay overall and the surface wave on the crack surface will gradually emerge. At the moment of crack initiation, the crack tip has a distinct opening speed. The shorter the pre-crack length, the higher the loading rate and energy. The opening displacement became larger on the crack surface. The results of testing initial expansion toughness could be affected by the position of loading center, the length of pre-crack, and the change of loading aperture. The diameter of the loading hole changes by 1㎜, the deviation of the test result is 7.1%. The crack length changes by 1㎜ and the deviation of the test result is 4.5%. The loading center deviate by 1㎜ and the deviation of the test result is 3.9%. Therefore, it is possible to perform multiple measurements on the three dimensions after the sample is processed, and replace the design value with the actual measured value to ensure the test accuracy. Keywords: sandstone; first wave of explosion; fracture toughness; loading rate;crack propagation speed