Research On Vibration Propagation Law Of Frozen Soil Blasting In Deep And Large Vertical Shaft And Its Influence On Shaft Wall

With the continuous development of my country’s industrialization,the demand for coal is gradually increasing.Newly-built mines show the characteristics of large designed production capacity,deep shaft,large cross-section,and short construction period.These mines generally adopt the freezing method when crossing deep and thick topsoil.In the freezing method construction,the shaft wall bears a large external force under the action of underground confining pressure and freezing pressure,and because the large volume of high-strength concrete generates internal force during the setting and hardening process,the strength and rigidity are difficult to guarantee.The shaft wall is affected by the shock wave of frozen soil blasting,which is easy to cause damage to the shaft wall.Under the condition of multiple blasting cycles,the internal damage of the shaft wall continues to increase.This internal damage will be amplified again after the freezing wall melts,causing the concrete of the shaft wall to fall off,and water inrush accidents occur in serious cases.In this paper,combined with the West Air Shaft Project of Zhaogu No.2 Mine,comprehensive use of theoretical research,field test,numerical simulation and simulation experiment and other research methods,carried out research on the propagation law of frozen soil blasting vibration and its influence on the shaft wall,and obtained the following main result:(1)Aiming at the current problem of small blasting footage in frozen soil,a series of single-hole funnel tests and multi-hole blasting funnel tests in the same segment have been carried out.The single-hole blasting funnel test shows that when the charge is0.175kg,the best blast hole depth in frozen soil is 0.45m,the best blasting funnel volume is 0.075m~3,and the best blasting funnel radius is 0.438m;when five holes are blasted in the same cut,The volume of the blasting funnel obtained is 0.382m~3;when the distance between the peripheral eyes is 60cm at a certain dose,the blasting section of frozen soil meets the requirements of the design contour.(2)Based on the actual situation of the ventilation shaft in Zhaogu No.2 Mine,the propagation law of blasting vibration in a single frozen soil medium is studied.Through the underground-690m frozen soil blasting vibration test,the attenuation trend of the frozen clay vibration velocity in various directions is obtained,and the vibration velocity is fitted by the Sadolfsky formula to obtain the fitting formula of the vibration velocity.The wavelet packet analysis is carried out on the blasting vibration signal of frozen clay,and the change law of the blasting energy signal is obtained.(3)Using the method of field test,the impact of frozen soil blasting on shaft wall vibration was studied.When the section of frozen topsoil is detonated with 1-3-4-5electric detonators,the vibration to the shaft wall can be reduced.In order to ensure the safety of the shaft wall,the maximum vibration velocity of the blast on the shaft wall was 8.39 cm/s.Comparing the monitoring data,it is found that both the burst distance and the amount of charge play an important role in the vibration speed of the shaft wall.Compared with rock blasting,under the same blasting scheme,the slope of the vibration velocity of frozen soil blasting has a smaller change.(4)Numerical simulation is used to establish a model of porous short-distance blasting in a vertical shaft,and the influence of different blast hole types on shaft wall vibration is obtained.Considering the influence of frozen soil blasting on the internal force of the shaft wall,the change law of tensile stress and compressive stress on the shaft wall is analyzed,and the relationship between the charge amount and the internal force of the shaft wall is pointed out.It is further found that the radius of the hollow hole on the blasting face is larger.Larger,the lower the vibration speed of the shaft wall;the ground stress has a greater influence on the vibration speed of the shaft wall.The greater the confining pressure of the particle at the same position,the greater the particle vibration speed.(5)Considering the influence of frozen soil moisture content on the propagation of blasting stress wave,through vertical shaft frozen soil blasting simulation test,the effect of different moisture content on vibration velocity is obtained.In frozen soil blasting,the vibration speed of frozen soil with 10%moisture content is relatively high after blasting,which is about 3 times that of frozen soil blasting with 15%moisture content.Under the same moisture content,the multi-hole blasting scheme with hollow holes is better than the single-hole blasting scheme.And with the increase of the blast hole charge,the blasting vibration speed increased significantly.(6)Taking the west air shaft project of Zhaogu No.2 Mine as the project background,the application of the key technology of frozen clay construction in the actual project was explored.First,multi-circle freezing pipes are used for freezing,and the freezing temperature can be adjusted flexibly,which can provide a suitable freezing temperature for blasting and tunneling.Secondly,according to the underground confining pressure and the force of the engineering structure,the concrete strength grade is adjusted in a timely manner to ensure the pressure bearing and avoid displacement due to damage.Finally,the"three-eight system"work system is adopted to realize the shortest construction time of the project and achieve the best economic benefits.68 pictures,15 tables,108 references.