BLAST Scheme Research Articles

Numerical Simulation and Field Monitoring of Blasting Vibration for Tunnel In-Situ Expansion by a Non-Cut Blast Scheme.

There have been ever more in-situ tunnel extension projects due to the growing demand for transportation. The traditional blast scheme requires a large quantity of explosive and the vibration effect is hard to control. In order to reduce explosive consumption and the vibration effect, an optimized non-cut blast scheme was proposed and applied to the in-situ expansion of the Gushan Tunnel. Refined numerical simulation was adopted to compare the traditional and optimized blast schemes. The vibration attenuation within the interlaid rock mass and the vibration effect on the adjacent tunnel were studied and compared. The simulation results were validated by the field monitoring of the vibration effect on the adjacent tunnel. Both the simulation and the monitoring results showed that the vibration velocity on the adjacent tunnel's back side was much smaller than its counterpart on the blast side, i.e., the presence of cavity reduced the blasting vibration effect significantly. The optimized non-cut blast scheme, which effectively utilized the existing free surface, could reduce the explosive consumption and vibration effect significantly, and might be preferred for in-situ tunnel expansion projects.

Research on Optimization Design of Tunnel Blasting Scheme Adjacent to Buildings

The section of Jialingjiang Road Station to Xiangjiang Road Station along Qingdao Metro Line 13 is located in Qingdao, China. All of them show obvious characteristics, being soft on the top and hard on the bottom, and the interval tunnel is faced with the problem of existing adjacent buildings. In order to ensure the smooth progress of construction, as well as minimize the damage to the buildings, a new mechanical excavation combined with a blasting construction scheme for the adjacent buildings is proposed. In this scheme, the step method is used for excavation. The upper step is in the weak stratum, and the mechanical method is therefore used for excavation; the lower step is in the hard stratum, and the drilling-and-blasting method is thus used for excavation. Using FLAC3D 5.0 finite difference software and the method based on blasting an equivalent load, the vibration velocity at adjacent buildings caused by the combined mechanical excavation and blasting scheme, as well as the traditional full-section blasting scheme, is compared and analyzed. Further, the construction parameters of the combined mechanical excavation and blasting scheme are compared and selected based on building settlement, the plastic zone of surrounding rocks, building vibration velocity and other factors. The results show that under the mechanical excavation blasting scheme, the peak particle velocity of each monitoring point decreases significantly compared with that under the full-section blasting scheme, with a maximum reduction of 61.1%, which is within the allowable range of the project, demonstrating the rationality of the new scheme. Finally, the mechanical excavation advance in the upper step is determined as 0.5 m. The optimized parameter construction effect is monitored and evaluated, the problems encountered in the project are successfully solved using the combined mechanical excavation and blasting scheme, and the expected construction period is shortened by 3 months, which shows the rationality of the blasting construction scheme proposed and its parameters, as well as the validity of the calculation results. The research results can be used as a reference for the construction scheme design of similar projects.

Assessing the explosion effect on rock mass pre-destruction

Introduction. Theoretical and empirical research into rock blasting proved that detonation wave propagation results in the development of destruction and pre-destruction zones around the explosive cavity. In the destruction zone, rock crushes. In the pre-destruction zone, stresses set up by the detonation wave are concentrated on rock mass structure defects, giving rise to new micro defects and the development of the existing ones. Rock fracturing and cavitation increase, lowering its strength properties; this is called rock pre-destruction. There are works devoted to the qualitative analysis of rock in the pre-destruction zone, but the problem requires elaboration to offer possibilities for practical application. Research aims to quantify rock mass pre-destruction to use the parameters of rock blasting by borehole charges under opencast mining in engineering calculations. Methods of research. To assess the degree of rock mass pre-destruction at a distance from the charge axis, a pre-destruction intensity coefficient is used. The destruction zone radius is determined by a well-known method. In the destruction zone, the value of the pre-destruction intensity coefficient is higher than one, i. e. there is discontinuity of the rock mass. Beyond the destruction zone, there is a pre-destruction zone where the value of the pre-destruction intensity coefficient is less than one. The pre-destruction zone boundary is at distances of the order of 200–250 charge radii. The pre-destruction intensity coefficient of a particular zone attained after all charges have been fired is determined by summing the pre-destruction intensity coefficient from every charge. According to the energy approach, rock strength can be assessed by the value of the specific drilling energy intensity. In order to determine the reduction value of the specific drilling energy intensity in a particular zone, it is essential to know the drilling specific energy capacity of this zone in the natural state, the pre-destruction intensity coefficient attained after a large-scale blast of borehole charges, and specific drilling energy intensity of completely disintegrated rock. The effect made by another borehole charge explosion on the rock mass is weaker due to its pre-destruction by previous blasts. So we propose the impact multiplicity coefficient that reflects the accumulation of pre-destruction in a particular zone under the sequence blasting of borehole charges. Results. The expected value of the specific drilling energy intensity has been calculated for the individual arbitrarily spaced wells within the pre-destruction zone of a particular rock mass zone. The calculation results were compared with the practical values measured during blasting preparation in the preset rock mass zone. Conclusions. The findings of this study have made it possible to quantify the impact of explosions on rock mass pre-destruction. The developed technique makes it possible to predict the value of drilling energy intensity in the pre-destruction zone and, as a result, establish the required specific energy intensity of detonation and hence the consumption of explosives. Thus, it becomes possible to reduce the consumption of explosives under the existing blasting scheme at the enterprise and model other charge initiation types to select the least expensive one.

Impact analysis of pressure-relief blasting on roadway stability in a deep mining area under high stress

In the development of deep underground engineering operations, the surrounding rock is prone to large deformation, rockbursting, and other major engineering disasters. Pressure-relief blasting can improve the stress field in a deep rock mass and prevent the occurrence of roadway collapse. Based on the excavation of the Sandaoshan Mine, ANSYS/LS-DYNA dynamic finite element software is used to simulate the damage and fracture area in the surrounding rock of the roadway under three types of pressure-relief blasting schemes. The strength of the rock mass in the damaged area is reduced, and then the ground stress balance calculation is conducted. The stability of the surrounding rock rock a deep roadway is compared and analysed from aspects of stress and energy and it is verified by theoretical calculation of impact energy factor. The research results show that the non-penetrating fracture zone formed by pressure-relief blasting will increase the stress concentration of the surrounding rock of the roadway, which is more unfavourable to engineering safety. When a reasonable blasting scheme is designed to form a penetrating fracture zone in the surrounding rock of roadway, the concentrated high ground stress in the surrounding rock can be transferred to the deeper part of the rock mass, thereby reducing the elastic strain energy, reducing the risk of a rockburst. Pressure-relief blasting increases the rock mass quality in the failure zone formed by excavation, and reduces the impact energy factor k. When k decreases below the energy threshold, it can prevent rockbursting and ensure the stability of the surrounding rock of the roadway.

The ANP-Fuzzy-TOPSIS model for the optimization of the scheme of large-section blasting

In view of the difficulty of decision-making in the scheme selection of a bauxite mine in extensive section blasting, it is combined with analytic network process (ANP), fuzzy theory, and TOPSIS theory. The establishment of ANP-Fuzzy-TOPSIS comprehensive evaluation index system of comprehensive evaluation model can optimize the 3 selections of blasting scheme. From the 10 indicators of careful consideration of the impact of blasting scheme selection factors of 3 aspects of economy, technology, and safety, through the analytic hierarchy process, it objectively determines the weight vector of each evaluation index. Then, combined with the theory of fuzzy mathematics and the ideal construction of ANP-Fuzzy-TOPSIS comprehensive evaluation model solution method principle, the comprehensive evaluation index of each scheme calculate is calculated based on the superior degree. The selected cutting scheme is superior to 49.8%, 51.3%, and 48.4% to determine the second kinds of blasting scheme (double wedge cut) optimal. The results of this study are consistent with the results of BP neural network method, catastrophe progression method, and AHP-TOPSIS model, which prove the feasibility of the model.

Optimization Analysis of Controlled Blasting for Passing through Houses at Close Range in Super‐Large Section Tunnels

According to the on‐site vibration velocity monitoring and peak vibration velocity prediction, it is found that the maximum vibration velocity generated by the existing Dizong blasting scheme does not meet the requirements of the maximum allowable vibration velocity of houses. Therefore, the existing blasting scheme is optimized by reducing the maximum single‐segment charge and a variety of damping measures such as multistage duplex wedge groove, adding damping hole, and millisecond blasting. In addition, the blasting data before and after optimization are analyzed and compared by wavelet (packet) technology. The results show that the optimized blasting main frequency domain is increased to 50∼150 Hz and the maximum vibration intensity value is reduced by 79.8%. Based on the time‐energy analysis, the maximum energy value is reduced by 67.75% compared with the original scheme, and the dominant energy of the original scheme is reduced by 97.81%, 71.49%, 82.44%, 95.93%, and 93.03%, respectively, after optimization. The maximum vibration velocity generated by the optimized blasting scheme construction is 1.12 cm/s, which is less than the maximum allowable vibration velocity of the building of 1.2 cm/s, which meets the maximum allowable vibration velocity requirements of the building. The optimized blasting scheme realizes the safe and rapid construction of the two steps of the Dizong tunnel, which can provide a reference for similar engineering construction in the future.

Optimization for Blasting Scheme of Crown-Sill Pillar Based on CW-GT and GC-WTOPSIS

Blasting scheme for crown-sill pillar of a lead–zinc mine was optimized by a new combination optimization model on the basis of CW-GT and GC-WTOPSIS. Nine main evaluation indices influencing blasting were chosen from economy, technology and safety aspects to establish the synthetic evaluation index system of four blasting schemes. Then the synthetic superiority degrees of the four schemes were determined with the basic theory of CW-GT and GC-WTOPSIS. Scheme- III (burn cut, inclined hole and side collapse with an angle of 80°) had the highest superiority degree and hence was confirmed as the best. The result was consistent with AHP-TOPSIS, BP neural network and catastrophe progressing model. The practice showed that the selected blasting scheme achieved the desired blasting effect, and the new method was suitable for optimization of blasting scheme, which provided a new way for scientific and reliable optimization of similar programmes.

Quantifying the difficulty of tunnelling by drilling and blasting

This study deals with industrial trends in tunnelling by drill and blast (D&B). We perform a statistical analysis of accumulated experience from the 1950s to the modern day to provide advice for proper project management in tunnel driving. The basis of the study is a wide database of tunnel blast schemes. This database is made of excavation parameters, and considers two main families of blasts: with parallel hole cuts and with inclined hole cuts. Such parameters are analysed by means of statistical regression. Correlations are shown. We present a general curve of correlation between tunnel sections and specific drilling and specific explosive consumption. We show how pull efficiency cannot be correlated to a single parameter, and how tunnelling by D&B needs to be treated as a complex system. Finally, we propose a method for quantifying and classifying the difficulty of tunnelling. The deviation of specific drilling (SD) from industrial average trend is used as an indicator of difficulty: easier when SD is lower than average, and more difficult when SD is higher than average. We show how such deviation can be preliminarily associated with lithotypes. This provides to designers and cost estimators a tool of a first approximation for D&B cost prediction at the pre-feasability and feasibility stages of a tunnelling project.

Design of Blasting Scheme Based on Numerical Simulation

Operating safety of adjacent pre-constructed pipeline must be insured when the crude oil and refined oil pipeline is under construction. Applying finite element method, the peak velocities of observed points located at test segment and operating segment of West to East Gas Transmission Pipeline were calculated, and the ratio of the two peak velocities in different relative positions was also obtained. Taking advantage of quantitative relationship between the detonation charge and vibration velocity of particle on the pipeline, the ratio of detonation charge is derived from the peak velocity ratio, thereby the blasting scheme of West to East Gas Transmission Pipeline with different thickness is ascertained. This method is not only economical and convenient, but also has no damage to the pipeline, which also works for other blast schemes of different conditions.

On Some Near Optimal Low Complexity Detectors for MIMO Fading Channels

We introduce several low complexity sub-optimal MIMO detection schemes based on the List-BLAST algorithm, which exhausts the constellation points in the first layer of a BLAST scheme to generate multiple candidate solutions from which the maximum likelihood solution is determined. The candidates can also be used as initial points for the space alternating generalized expectation-maximization (SAGE) algorithm to further improve performance. The proposed schemes can achieve close to optimal performance for both hard and soft output detection with lower complexity than that of the sphere detection in our simulation settings

Iterative demodulation/decoding methods based on Gaussian approximations for lattice based space-time coded systems

In this letter, we study iterative demodulation and decoding methods for lattice based space-time coded systems concatenated with convolutional codes. We first apply the optimal MAP demodulation and the suboptimal linear MMSE methods to lattice based space-time demodulation and decoding. We then propose two other methods based on the idea of soft interference cancellation and in one method vector Gaussian approximation is used and in the other method scalar Gaussian approximation is used. We also present the EXIT chart analyses for the performance analyses for these iterative methods. Both theoretical and simulation results show that the performance of the vector Gaussian approximation method is the same as that of the linear MMSE method but in some cases the vector Gaussian approximation method has lower complexity. The complexity of the scalar Gaussian approximation method is the lowest among these different methods and grows linearly with the transmission rate while it still has an acceptable performance. Full diversity and full rate lattice based space-time coding is compared with the BLAST scheme and simulations show that the former has a better performance than the later even with the proposed suboptimal iterative demodulation and decoding methods.

Generalized Alamouti Codes for Trading Quality of Service against Data Rate in MIMO UMTS

New space-time block coding schemes for multiple transmit and receive antennas are proposed. First, the well-known Alamouti scheme is extended to transmit antennas achieving high transmit diversity. Many receiver details are worked out for four and eight transmit antennas. Further, solutions for arbitrary, even numbers of transmit antennas are presented achieving decoding advantages due to orthogonalization properties while preserving high diversity. In a final step, such extended Alamouti and BLAST schemes are combined, offering a continuous trade-off between quality of service (QoS) and data rate. Due to the simplicity of the coding schemes, they are very well suited to operate under UMTS with only very moderate modifications in the existing standard. The number of supported antennas at transmitter alone is a sufficient knowledge to select the most appropriate scheme. While the proposed schemes are motivated by utilization in UMTS, they are not restricted to this standard.

Performance Comparisons of MIMO Techniques with Application to WCDMA Systems

Multiple-input multiple-output (MIMO) communication techniques have received great attention and gained significant development in recent years. In this paper, we analyze and compare the performances of different MIMO techniques. In particular, we compare the performance of three MIMO methods, namely, BLAST, STBC, and linear precoding/decoding. We provide both an analytical performance analysis in terms of the average receiver and simulation results in terms of the BER. Moreover, the applications of MIMO techniques in WCDMA systems are also considered in this study. Specifically, a subspace tracking algorithm and a quantized feedback scheme are introduced into the system to simplify implementation of the beamforming scheme. It is seen that the BLAST scheme can achieve the best performance in the high data rate transmission scenario; the beamforming scheme has better performance than the STBC strategies in the diversity transmission scenario; and the beamforming scheme can be effectively realized in WCDMA systems employing the subspace tracking and the quantized feedback approach.