The propagation of stress waves in filled jointed rocks involves two important influencing factors: transmission-reflection phenomena and energy attenuation. In this paper, the split Hopkinson pressure bar (SHPB) test is used to shock the filled rock with joint angles of 0, 30, and 45° and the thickness of 4 mm and 10 mm, respectively, in three different velocities. The wave curves of the incident wave, reflected wave, and transmission are obtained. The effects of the filling angle and joint thickness on wave propagation are analyzed. Based on the propagation characteristics of stress waves in joints, the stress expression of oblique incident stress waves propagating in filling joints is derived, and the energy coefficient of transmission and reflection is calculated. The results show that the propagation of stress wave in filling joints is related to the impact rate. The larger the impact rate is, the larger the maximum voltage amplitude of the three waves is. And the increasing amplitude of the incident and reflected waves is larger than the transmitted wave; the greater the impact velocity is, the smaller the stress-strain curve gap of the three dip joints is, and the fracture strength of the specimen decreases with the increase of the joint dip angle. The larger the joint dip angle is, the smaller the deformation of the rock-like specimen is. The change of the transmission coefficient is related to the joint angle, and the larger joint angle weakens the influence of the joint width on the transmission of the transmitted wave; under each impact velocity, the theoretical and experimental stress peaks are approximately the same, and the transmission coefficient maintains a good consistency with the oblique incident angle.
Blasting in water-conveyance tunnels that cross rivers is vital for the safety and stability of embankments. In this work, a tunnel project that crosses the Yellow River in the north district of the first-phase Eastern Line of the South-to-North Water Diversion Project was selected as the research object. A complex modeling and numerical simulation on embankment stability with regard to the blasting power of the tunnel was conducted using the professional finite difference software FLAC3D to disclose the relationships between the blasting seismic waves with vibration velocity and embankment displacement under different excavation steps. Calculation results demonstrated that displacement generally attenuated from the tunnel wall to the internal structure of rocks under the effect of blasting seismic waves. The tunnel wall was in tension, and tensile stress gradually transformed into compressive stress with increased depth into the rocks. The curtain-grouting zone was mainly concentrated in the compressive zones. For different excavation steps, the vibration velocity at different feature points was high at the beginning of blasting and then gradually decreased. The resultant displacement was relatively small in the early excavation period and slowly increased as blasting progressed. The effects of different excavation steps on the safety of surrounding rocks and embankment under blasting seismic waves were simulated. We found that the blasting-induced vibration velocity was within the safe range of the code and that the calculated displacement was within the allowed range. Numerical simulation was feasible to assess the safety and stability of engineering projects.
The commonly used method for tunnel excavation is the drilling and blasting method, but the surrounding rock will accumulate damage under the action of blasting, leading to engineering accident, and the consequences of the accident in the Yellow River-crossing tunnel will be more serious. The work proposed a quantitative evaluation calculation of the damage on surrounding rocks caused by tunnel blasting excavation to study the effect of tunnel blasting on the damage of surrounding rock. analyzes the damage plasticity model theoretically, and determines the rock constitutive curve used in the numerical calculation of vibration damage, based on which plane physical model is established to adopt several different stress control standards to calculate the vibration damage of surrounding rock. The results proved that in the damage settlement of planar model 1, the damage variable around the tunnel was 0.14 at the maximum and 0.10 at the minimum. In the curtain grouting area, the maximum damage variable was 0.05, and the minimum was 0.01. In the damage settlement of planar model 2, the damage variable around the tunnel was 0.45 at the maximum and 0.05 at the minimum. In the curtain grouting area, the maximum damage variable was 0.20, and the minimum was 0.05.the impact of blasting vibration on the surrounding rock is mainly concentrated near the cavern, Thus, with the rock depth increasing, the damage decreased. the damage in the grouting curtain area is relatively small. The results accurately reflected the damage caused by blasting vibration on surrounding rocks and provided references for engineering construction.
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