The numerical simulation of rapid excavation technologies under the combined form of hydraulic fracturing and drill-and-blast method

With the aim of the drilling and blasting in underground space, there are problems of poor tunnel formation, large crushing and loosening area, difficult support, low driving efficiency, and special geological conditions that are not suitable for drilling and blasting. According to the fracturing and blasting theory and auxiliary hole effect, a combined hydraulic fracturing and drilling blasting tunneling technology was proposed in this research. Establish a rock breaking model, and according to the mechanism of swelling and breaking, the rock breaking efficiency and effect of swelling and breaking, the number of drill holes and the arrangement of drill holes affect the rock breaking performance; the traditional drilling and blasting method used the change of dynamic pressure and vibration velocity to judge the propagation and attenuation process of blasting vibration, as well as the range of damage area. The ANSYS LS-DYNA, a numerical simulation software, was used to determine the position and size of the top facing holes, the optimal spacing of fracturing holes, blasting holes and auxiliary holes. The static load applied to the arc part can effectively reduce the crushing area, the crack area and the elastic area. The lower rectangular part is arranged with the auxiliary holes reasonably to inhibit the propagation of the blasting shock wave, slow down the development of the fracture, guide the extension direction of the crack, and reduce the damage range of the three areas, avoid low efficiency of deep hole blasting, and judge the practicability and operability of this method based on the timeliness of each stage of excavation. The combined pressing and blasting method with the high-efficiency and short-distance, multi-frequency and high-efficiency excavation effectively controlled the shape of the upper area of the roadway, which contributes to reducing the damage area of the surrounding rock, developing a safe working environment, decreasing the maintenance cost of the roadway in the later stage, and providing a innovative way for the development of underground space in the future.