Study On Blasting Dynamic Characteristics Of Open Pit To Underground Mining Slope

With the exploiting of surface mining as ore resources, shallow resources declines and mining is turning from open pit to underground mining projects either at home or abroad. Blasting is an inevitable means of mining production and construction projects in mining, rock excavation, underground mining. Surface slope collapse, slip and other geological disasters are common occurrences because of the influence of blasting vibration dynamic action. Therefore, the problem of slope dynamic stability has become a key scientific and technological issue of safe exploiting in open pit to underground mining. Moreover, the dynamic response of open pit to underground mining slope is not only the basis for the work of the slope blasting dynamic stability problems, but also the hot topics in engineering geology, explosion and rock dynamics, which has significant importance in theoretical and engineering applications.In this paper, the field test, combined with numerical simulation, theoretical calculation and analysis were adopted. The analysis of the open pit to underground mining the slope blasting vibration field test, slope altitude effect of blasting vibration velocity, deep hole explosion in underground mining stress Bohol overload characteristics, the dynamic response of the open pit to underground mining blasting, the safety criterion of blasting vibration velocity in open pit to underground mining, etc. were carried out. The main results are listed as followings:(1) Study on rule of blasting vibration propagation on open pit to underground mining slope. Daye Iron Mine underground mining blasting vibrations were monitored applying the TC-4850blasting vibration recorder test system. Then, A series of open-pit slope rock blasting vibration test data were obtained which were analyzed on frequency distribution characteristics and velocity attenuation. The results show that:the main vibration frequencies on X, Y and Z direction are not consistent; the frequency on X direction is mainly concentrate in55Hz, but the frequencies on Y and Z direction are less than45Hz. Due to differences of rock mass characteristics and special geological conditions, there are significant differences of vibration propagations on the north and south slope rock mass by comparing the Sadaovsk formulas. The vibration velocity of the south slope which is made of marble attenuates faster. The influences of blasting vibration on the north and south slope should be analyzed separately.(2) Study on blasting vibration altitude effect of open pit to underground mining slope. A new forecasting model of blasting vibration velocity which considered the altitude effect was established based on the principle of dimensional analysis; then the blasting vibration velocity propagation characteristics were predictive analyzed separately by the forecasting model and Sadaovsk formula. On the basis of north slope mining engineering practice, the numerical model of the slope was established which was improved by field data. Applying the proved model and parameters, this dissertation establish the different degree slopes which contains15°slope,30°slope,45°slope and60°slope, and investigate the blasting vibration altitude effects of the slope. The results show that:the new forecasting model predicts the blasting vibration attenuation rules more accurate than Sadaovsk formula; the PPV’s amplification is obvious, and the vertical PPV plays the main role; The PPVs on the different slope surface attenuate with the slope degree increase, but there is a phenomenon that the amplification effect plays the main role.(3) Study on blasting load characteristics of sector medium-length hole in underground mining. The sector medium-length hole blasting model was established by dynamic finite element software LSDYNA, and the distribution characteristics of effective stress and resultant velocity were calculated and analyzed; Applying the same material parameters, this dissertation established the spherical structure blasting models whose radius were0cm,32cm,34cm,36cm,38cm,40cm,42cm,44cm,46cm,48cm; the equivalent spherical charge model was obtained by comparing effective stress and resultant velocity with sector medium-length hole charge model. The results show that:the blasting load characteristics of338kg (radius is42cm) spherical structure model were similar with493kg sector medium-length hole charge model; the equivalent spherical charge model can reflect the load characteristics of sector medium-length hole which can eliminate the meshing problems caused by size disunion.(4) Study on blasting dynamic response of open pit to underground mining slope. Based on the special engineering geological conditions of Daye Iron Mine, the three-dimensional numerical model including underground mining tunnel, slope rock mass and fault fracture zone was established; then the blasting vibration velocity-time curves and main frequencies of slope rock mass, fault fracture zone and the A-slope rock mass. The results show that:the vibration velocities of south slope rock mass on X, Y, Z direction are0.823cm/s,0.727cm/s and0.866cm/s separately, and the frequencies are between23.14Hz and31.88Hz; the vibration velocities of North slope rock mass on X, Y, Z direction are0.877cm/s0.737cm/s and0.903cm/s separately, and the frequencies are between13.89Hz and25.17Hz; the vibration velocities of A-slope slope rock mass on X, Y, Z direction are from0.464cm/s to0.176cm/s, and the frequencies are from38.22Hz to22.83Hz.(5) Study on blasting vibration velocity safety criterion of open pit to underground mining slope. On the basis of rock dynamic theory and rock dynamic strength characteristics subjected blasting vibration, the dynamic tensile strengths of Daye Iron Mine slope rocks were determined; according previous numerical simulation research on dynamic response of slope rock mass, the relationship models of PPVs and tensile strength of the slope rock mass and fault fractures were established:combined with ultimate tensile strength criterion, the blasting vibration velocity safety criterions based on numerical simulation was calculated by the introduction of the concept of the importance of the correction factor. Meanwhile, based on the theory of stress wave propagation, the reflection and refraction on the free surface and the interface were analyzed, and the blasting vibration velocity criterion theoretical calculation model was established; combined Daye Iron Mine open pit slope engineering practice, the blasting vibration velocity safety criterions based on theoretical analysis was solved. Finally, the numerical analysis results and theoretical analysis compared with the blasting safety standard. The results show that:based on the relationship models of PPVs and tensile strength, the blasting vibration safety criterion of south slope is9.31cm/s, and the blasting vibration safety criterion of north slope is7.90cm/s; based on the theory of stress wave propagation, the blasting vibration safety criterion of south slope is13.41cm/s, and the blasting vibration safety criterion of north slope is27.79cm/s; the blasting vibration safety criterion of numerical calculation and theoretical analysis are both basically consistent with the blasting safety standard, and the theoretical analysis results is slightly larger compared to the results of the analysis for numerical calculation.