Research On Fracture Mechanism And Fracturing Effect Of Timing Controlled Blasting In Underground Powerhouse

In the national strategic development of marching deep into the earth,deep underground engineering such as deep resource development and underground space utilization is becoming or will soon become the norm.Therefore,the study of timeseries controlled fracture blasting technology in underground engineering,the analysis of the effect of directional seam formation between the blastholes,and the formation quality of the blasting excavation contour surface are crucial to the refined blasting construction and engineering safety of underground engineering.This article takes the blasting and excavation of the underground powerhouse of Henan Tianchi Pumped Storage Power Station as the research background.From the theoretical analysis and numerical simulation,this paper studies and analyzes the fracture formation mechanism of the sequential control blasting,and comparatively studies the different initiation timing types on the crack propagation between the holes The influence of the behavior is studied on the parameter optimization of the variable hole pitch sequential control blasting technology.In this paper,firstly,based on the theory of void effect and fracture mechanics,the effect of the stress concentration effect of the post-blast hole on the first hole in the sequence-controlled blasting is studied.From the perspective of wave dynamics and blast stress wave,the multiple scattering effect of the blast stress wave of the first blast hole between the two rear blast holes in the time-controlled blasting with variable hole distance is studied,and the expression of the dynamic stress concentration coefficient of the rear blast hole is derived.The change rule of the maximum dynamic stress concentration factor of the rear blast hole with the increase of vibration frequency and pitch-to-diameter ratio.Then,taking the blasting excavation of the underground powerhouse of Henan Tianchi Pumped-storage Power Station as the engineering background,the effects of the directional slotting of the traditional controlled blasting with equal hole spacing,the sequential controlled blasting with equal hole spacing and the sequential controlled blasting with variable hole distance were comparatively studied through numerical simulation.The effect of initiation delay time on crack propagation between blastholes was discussed.The mechanism of blast crack propagation was analyzed from the stress changes of explosion stress wave and rock medium unit,and the main crack propagation form between blastholes was summarized.Finally,the numerical simulation software was used to optimize the parameters of the time-controlled blasting technology with variable hole distance.The effects of the hole distance and the initiation delay time on the crack propagation between the holes were analyzed.The kinetic energy/internal energy ratio at different initiation delay time was studied.The change law of the method has obtained a reasonable blast hole interval and initiation delay time,and proposed the relationship between the first blast hole distance and the rear blast hole distance.In addition,the blasting and slotting technology was introduced in the variable-hole-pitch sequential control blasting,and the effects of the directional propagation of cracks between the blastholes under the three types of blasthole slotting,first blasthole slotting and blasthole slotting were compared and analyzed.Timing control-reasonable parameters and applicable scope of slotting blasting.