| The drilling and blasting method is the most commonly used excavation method in the drilling process of large diameter and ultra-deep shaft.The single-cycle explosive charge is large in shaft tunneling,and the vibration of blasting is difficult to control.Because the shaft lining is close to the blasting working face,the structure of shaft wall is inevitably influenced by the high vibration of the blasting.The stability of frozen wall in water-bearing strata is of great significance to the supporting effect optimization of the supporting structure,rib spalling produced by blasting disturbance for serious phenomenon such as poor quality of frozen wall forming,directly affect the stability of shaft constructed.The damage to the freezing pipe caused by the blasting can have an important effect on the formation of the temperature field of the frozen wall intersection and even lead to the engineering accident.At present,the research on blasting vibration reduction in blasting engineering depends on more and more empirical methods,such as reducing the footage and reducing the detonating dose,and so on.It is urgent to study the blasting vibration and damage control under medium-deep blasting.In this paper,based on the national natural science foundation "blasting dynamic load of frozen wall(pipe)and the mechanism of the supporting structure(51274203)",aiming at the problems of poor blasting forming,large unit consumption of explosives and serious damage to surrounding rock and the harmful effects of blasting vibration on the shaft wall and frozen pipe are significant.Takes Yankuang Heze Nenghua Wanfu mine shaft drilling and blasting construction as the engineering background,through the optimization of blasting parameters and the use of slotted cartridge charge controlled blasting technology to adjust the charge structure.In this way,effective control of vertical shaft blasting vibration and damage can be realized.Through field test,model test and numerical simulation method,thus reducing the wall structure vibration effect,frozen wall damage control and reduce the frozen pipe damage control and discussed the slotted cartridge blasting technology of vibration mitlgation and damage reduction effect,analyzed the influence of the blasting dynamic load on the high-strength shaft wall,frozen wall,and the supporting structure.The research contents mainly include the following aspects:(1)In view of the deficiency of the existing method of vibration testing of shaft lining,the embedded vibration monitoring method of shaft wall is proposed.In the pouring process of the shaft wall,the sensor is embedded in the reinforced concrete body of the shaft wall in advance,and the long-term and continuous monitoring of the shaft wall structure is realized.Through the method of pre-fixing the protection box on the shaft wall.On the basis of accurate acquisition of vibration signals of shaft wall,the law of vibration attenuation under the conventional blasting and slotted cartridge charge blasting is obtained,and the effect of vibration damping of the slotted cartridge charge is verified.(2)Through signal noise suppression and wavelet analysis methods,the actual detonation delay time in the section of shaft blasting network is precisely identified.The research shows that the detonation delay time of MS1?MS2 and MS2?MS3 in vertical shaft blasting initiation network plays an important role in vibration control of shaft lining.Due to the detonation delay time,MS1?MS2 and MS2?MS3 detonators interval delay is relatively close to the lower limit of detonator calibration delay time,the delay time is not enough thus lead to the MS3 and MS2 section blasting vibration peak is offset to MS3 segment detonator initiation peak on the time axis.Therefore,peak velocity superposition occurs during the initiation period of MS3.Therefore,it is necessary to improve the precision of the MS1 and MS2 segment,which can reduce the blasting vibration intensity.(3)The spectrum characteristics of blasting vibration signals collected under different schemes were extracted.The main frequency of vertical shaft blasting vibration was about 150 Hz,which was higher than that of conventional underground engineering blasting,which was beneficial to the shaft wall structure.Using FSWT(Frequency Slice Wavelet Transform)and wavelet analysis of a variety of analytical methods,obtained the signal in different frequency bands of energy distribution differences.The results show that the damping effect of the slotted cartridge blasting is mainly reflected in the near zone,at the same time,the local use of the slotted cartridge charge blasting is caused by the imbalance of the energy release of the explosive.It can lead to the "selective amplification" of the energy in the main vibration frequency band at different height of the shaft wall.This enlargement has some relationship with the uneven thickness of the shaft wall.Therefore,the symmetrical arrangement of slotted cartridge should be adopted in the engineering application to optimize the blasting vibration reduction effect.(4)The qualitative analysis and quantitative evaluation of the forming quality of frozen wall under different lithologies were carried out.Through the shooting of the frozen wall morphology after the slotted cartridge charge blasting under different lithologies,the application effect of slotted cartridge charge blasting under different lithologies is analyzed qualitatively by active contour recognition.Three-dimensional reconstruction of the shape of the frozen wall was performed by digital image correlation processing method.The multi-fractal algorithm was used to quantitatively evaluate the effect of the slotted cartridge charge under different lithology conditions.The application results show that the quality of the frozen wall can be optimized by slotted cartridge charge blasting,and the better the lithological conditions are,the better the application effect is.(5)After blasting with slit charge cartridge,the efficiency of borehole was increased from about 80% to more than 93%,which improved the blasting efficiency.The half-eye mark rate increased from 33% to 75% in the past,which effectively controlled the phenomenon of overbreak.It can save the consumption of explosives,detonators and other pyrotechnics.It reduces the total charge and hole number of single-cycle detonation and saves the drilling time.It can greatly reduce the support cost and engineering related auxiliary costs,and has significant economic benefits.(6)Because of the difficulty in realizing the measurement of explosive vibration response and damage shape of the frozen wall rock mass,a reasonable precondition is established,the disassembly mold is designed,the similar theory is applied and the physical model is established in the laboratory.On the basis of meeting the similarities of geometry,similarity of materials and the similar blasting power,the attenuation characteristics of blasting vibration wave in the surrounding rock mass are discussed.Three kinds of failure modes of tensile failure,single-slope shear failure and X-shaped conjugate slope shear are obtained under uniaxial compression of surrounding rock mass.In the horizontal direction of the surrounding rock mass,three vibration measuring points are arranged,and the effective acquisition of the vibration signal under different blasting schemes of the surrounding rock mass is achieved.Through the conversion of the equivalent distance between borehole and measuring point and the equivalent dose,the law of vibration attenuation of the surrounding rock mass under the conditions of conventional blasting and slotted cartridge charge blasting in peripheral eye are obtained by regression fitting.(7)Since the noise components contained in the signal greatly interfere with the extraction of its effective information,the EMD-DFA combination method is used to denoise the vibration signal of the surrounding rock.The four indicators of average error,signal-to-noise ratio,peak signal noise ratio and cross-correlation coefficient are compared,superiority of EMD-DFA method in denoising processing are determined.(8)Based on the analysis of the characteristics of different time-frequency analysis methods,the time-frequency features of signals under different blasting times were extracted by using HHT analysis.The signal energy of the first blasting of the slotted cartridge charge is not excessively concentrated in a certain frequency band,which reflects that the energy of the slotted cartridge charge blasting is dispersed evenly.The amplitude only has a large mutation in a few finite time and frequency,the low-frequency energy is discrete,and the vibration energy band is obvious.At 1 # and 2 # points,the peak energy of slotted cartridge charge blasting was 25% lower than conventional one,and the peak energy of slotted cartridge charge blasting at # 3 was 50% lower than that of conventional blasting.In the second blasting,the energy peak at 1# and 2# were reduced by 25% and 33%,respectively.The blasting energy peak at 3# was reduced by 66.7% compared with that of conventional blasting.The slotted cartridge charge blasting can make the main energy distribution to the high frequency,but it lasts longer on the time axis.The energy has a more uniform distribution in the above 500 Hz band,and gradually weakens with the increase of frequency.As the detonation distance increases,the energy contained in the high frequency part decreases gradually.The energy color bar is clearer,and the energy propagation in the near area tends to be stable.In the third blasting,the blasting energy peak of the blasting charge in 1# point was similar to that of conventional blasting,and the measuring points of 2 and 3 were reduced by 33% and 50%,respectively.With the increase of tunneling depth,the cavitation effect of excavation and the existence of micro-cracks make the explosion wave propagated to the inner wall of the slotted tube,the gas pressure in the slotted tube is redistributed,and the explosion wave pressure released is increased with the accumulation of the explosive gas at the cutting edge.According to the principle of energy conservation,the effect of detonation gas on the vertical cutting direction is weaker,and the energy is reduced and attenuated.(9)The acoustic wave test method was adopted to set 8 measuring points along the circle direction of the model,and 6 points were set in the height direction of the model to test the acoustic wave velocity before and after the explosion.By calculating the mean value of acoustic velocity of each measuring point,the cumulative damage of surrounding rock at each acoustic measuring point under different blasting times is obtained.The analysis shows that if the explosion parameters are basically the same,the rate of decrease of the cumulative sound velocity at the same measuring point basically increases.Explosion of the heart at the horizontal position of the spot injury degree of sudden change,reflecting the characteristics of the detonator centralized charge,which is different from the field of charge.(10)The nonlinear dynamic chaos characteristics of vibration signals under different test points are analyzed.The signal attractor after noise reduction has clear motion track and chaotic characteristics in a certain area.The long axis end value of the chaotic attractor corresponds to the extreme value of the vibration signal,and the upper end value corresponds to the maximum value of the signal,and the lower value corresponds to the minimum value of the signal.The larger the attractor is in the phase space,the higher the complexity of the signal,the slower the attenuation process is,and conversely,the attenuation is faster.As the depth of excavation increases,the attractor becomes smaller in the phase space and shows the continuous attenuation of energy.The vibration attenuation under the slotted cartridge charge blasting scheme of the measuring point 2# is reduced,the amplitude is reduced,and the frequency component is increased,the propagation is more stable,and the main peak is not obvious.The blasting energy tends to be stable,the loss is reduced,the attractor volume shrinks,and the equilibrium state transitions gradually.The region attractor trailing phenomenon is obvious,the initial micro cracks in concrete model that has formed,lead to changes in stress wave at the crack propagation path,in the embodiment of the signal waveform is in the main vibration time shock phenomenon.Due to the sensitivity of the blasting vibration in 3# point to the initial conditions of the boundary,the random chance characteristics of the attractor morphological changes are presented.The chaotic attractor change of blasting vibration signals under different schemes show that the blasting process belongs to the energy dissipation process,namely the non-linear energy dissipation process.(11)On the basis of introducing the basic theory of nonlinear dynamic finite element software ls-dyna,the research on the influence of freezing shaft blasting on the damage of frozen pipe is carried out.By applying the equivalent load to the zone of different detonators,the visualization of the vibration response process of frozen pipe under blasting load is realized.The vibration acceleration information of different parts of the frozen pipe is extracted and its response spectrum is obtained.It can be seen from the analysis that the peak of the vibration velocity is the most important factor affecting the area value of the reaction spectrum.The response spectrum area is positively correlated with the concentration of input energy.With the increase of the damping coefficient of the structure,the peak value of the acceleration response spectrum decreases,but the morphology tends to be consistent.The peak acceleration-response spectrum peak-response spectrum area gradient graph was established.The number of edges in the gradient graph is the number of detonator segments used.The different colors in the area cross each other,reflecting the degree of mutual interference and vibration reduction.The size of irregular pentagonal area reflects the damping effect of slotted cartridge charge to a certain extent.According to the Helen formula,the gradient graph is effectively divided and its area is calculated.The area of the gradient graph under the two blasting methods is 58.5052 and 40.6877,respectively,and the area of the conventional blasting gradient graph is 1.44 times of the slotted cartridge charge blasting,the initial input energy is greater.The distribution of damage probability under different blasting modes is obtained by weighting the data in different areas.The analysis indicates that RSI(Response Spectrum Integral)>6 is the focus of control,and the probability of damage of the frozen pipe in this value range is 0.916,and it is feasible to evaluate the blasting vibration effect by RSI value index. |
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