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A large ore loss and dilution can be expected when using a pre-blast ore boundary for shovel guidance because of the movement and re-distribution of ore in the muck pile under the action of explosive energy. Considering the difficulties in collecting measurements at the post-blast ore boundary, the distribution law and prediction of blast-induced rock movement were studied in this paper. With the application of a blast movement monitoring system, which can obtain the most accurate data to determine the ore boundary after the blast, four blast movement trials were carried out to collect data. Then, statistical analysis, an artificial neural network (ANN) model, a random forest (RF) model and a gray wolf optimizer algorithm–support vector regression (GWO-SVR) model were used to analyze the database. The results of the statistical analysis show that the horizontal, vertical and 3D movements first increase and then decrease, with the maximum displacement occurring near the top of the charging section. Furthermore, the horizontal movement exhibited a good linear relationship with the 3D movement, indicating that the horizontal movement can be considered instead of the 3D movement to facilitate shovel guidance for reducing ore loss and dilution. The results also indicate that the GWO-SVR model is more accurate than the ANN and RF models and that the blast-induced rock movement can be controlled by increasing the burden × spacing and reducing the power factor variables during the mining process.

A simple and accurate evaluation method of broken rock zone thickness (BRZT), which is usually used to describe the broken rock zone (BRZ), is meaningful, due to its ability to provide a reference for the roadway stability evaluation and support design. To create a relationship between various geological variables and the broken rock zone thickness (BRZT), the multiple linear regression (MLR), artificial neural network (ANN), Gaussian process (GP) and particle swarm optimization algorithm (PSO)-GP method were utilized, and the corresponding intelligence models were developed based on the database collected from various mines in China. Four variables including embedding depth (ED), drift span (DS), surrounding rock mass strength (RMS) and joint index (JI) were selected to train the intelligence model, while broken rock zone thickness (BRZT) is chosen as the output variable, and the k-fold cross-validation method was applied in the training process. After training, there validation metrics including variance account for (VAF), determination coefficient (R2) and root mean squared error (RMSE) were applied to describe the predictive performance of these developed models. After comparing performance based on a ranking method, the obtained results show that the PSO-GP model provides the best predictive performance in estimating broken rock zone thickness (BRZT). In addition, the sensitive effect of collected variables on broken rock zone thickness (BRZT) can be listed as JI, ED, DS and RMS, and JI was found to be the most sensitive factor.

Most mines choose the drilling and blasting method which has the characteristics of being a cheap and efficient method to fragment rock mass, but blast-induced ground vibration damages the surrounding rock mass and structure and is a drawback. To predict, analyze and control the blast-induced ground vibration, the random forest (RF) model, Harris hawks optimization (HHO) algorithm and Monte Carlo simulation approach were utilized. A database consisting of 137 datasets was collected at different locations around the Tonglvshan open-cast mine, China. Seven variables were selected and collected as the input variables, and peak particle velocity was chosen as the output variable. At first, an RF model and a hybrid model, namely a HHO-RF model, were developed, and the prediction results checked by 3 performance indices to show that the proposed HHO-RF model can provide higher prediction performance. Then blast-induced ground vibration was simulated by using the Monte Carlo simulation approach and the developed HHO-RF model. After analyzing, the mean peak particle velocity value was 0.98 cm/s, and the peak particle velocity value did not exceed 1.95 cm/s with a probability of 90%. The research results of this study provided a simple, accurate method and basis for predicting, evaluating blast-induced ground vibration and optimizing the blast design before blast operation.

Delay blasting with relatively long-delay intervals is widely used in mining engineering since the former detonated blast-holes can produce new free surfaces for the later detonated blast-holes. With the application of electronic detonators, which have a minimum delay and a delay accuracy of 1 ms, a new blasting pattern using short-delay intervals is proposed in the present study in order to improve rock breaking and control blast-induced vibrations in cutting blasting with single free surface in underground mines. Theoretical analyses are firstly conducted to investigate the mechanisms of blasting crater formation and vibration reduction of short-delay blasting. Then a series of blasting crater tests with different delay intervals are performed to compare the characteristics of blasting craters and blast-induced vibrations produced by short-delay and simultaneous blastings. The results of crater sizes show that it is possible to form a common blasting crater only when the delay intervals are shorter than the formation time of a new free surface. It is also found that the short-delay blasting can effectively reduce PPV compared with the simultaneous blasting, particularly in the near-field. Spectral analysis indicates that there is less energy in the low-frequency content in short-delay blasting than simultaneous blasting. The possibility and feasibility of reducing vibration via short-delay blasting in underground mines are also discussed in this study.

Deformation prediction and the analysis of underground goaf are important to the safe and efficient recovery of residual ore when shifting from open-pit mining to underground mining. To address the comprehensive problem of stability in the double mined-out area of the Tong-Lv-Shan (TLS) mine, which employed the dry stacked gangue technology, this paper applies the function fitting theory and a regression analysis method to screen the sensitive interval of four influencing factors based on single-factor experiments and the numerical simulation software FLAC3D. The influencing factors of the TLS mine consist of the column thickness (d), gob area span (D), boundary pillar thickness (h) and height of tailing gangue (H). The fitting degree between the four factors and the displacement of the gob roof (W) is reasonable because the correlation coefficient (R2) is greater than 0.9701. After establishing 29 groups that satisfy the principles of Box-Behnken design (BBD), the dry gangue tailings process was re-simulated for the selected sensitive interval. Using a combination of an analysis of variance (ANOVA), regression equations and a significance analysis, the prediction results of the response surface methodology (RSM) show that the significant degree for the stability of the mined-out area for the factors satisfies the relationship of h>D>d>H. The importance of the four factors cannot be disregarded in a comparison of the prediction results of the engineering test stope in the TLS mine. By comparing the data of monitoring points and function prediction, the proposed method has shown promising results, and the prediction accuracy of RSM model is acceptable. The relative errors of the two test stopes are 1.67% and 3.85%, respectively, which yield satisfactory reliability and reference values for the mines.

It is essential to control the damage to the surrounding rock and engineering structures in the process of cut blasting with a single free surface in underground mining. To reduce vibration induced by cut blasting, this paper proposes short-delay cut blasting, in which blast holes that are near each other are sequentially initiated with short-delay times. Experimental tests of cut blasting were conducted in a roadway in the Shaxi copper mine to compare the peak particle velocity (PPV) and frequency characteristics of simultaneous blasting and short-delay blasting. Numerical modelling was then developed to study the influence of short-delay times on blast vibration. The accuracy of the numerical simulation was verified by the comparison of the test and simulated data of single-hole blasting. The results show that the amplitude reduction ratio (ARR) value increases gradually with the increase in delay intervals, and the vibration reduction for delay intervals smaller than 6 ms is very limited, particularly in the near field. The principal frequencies (PFs) for short-delay blasting are similar to those for simultaneous blasting, which implies that the frequencies do not increase directly with the decrease of the delay intervals. The experimental tests also show that the mean frequencies (MFs) for the 8 ms delay are slightly higher than those for the 0 ms delay blast. In the case of ensuring the rock breaking of cut blasting, longer delay intervals of 8∼10 ms are beneficial to further reduce PPV in practical blasting.

Controlling rock damage induced by lateral blasting excavation is a source of concern. In underground mines, large-diameter-hole lateral blasting excavation often causes engineering disasters such as large blocks falling and overall collapse of the remaining rock mass. Because of their high cost and cumbersome operation, conventional contour blasting techniques, such as smooth and presplit blasting, are unsuitable for production boreholes. In this paper, based on the large-diameter-hole lateral blasting excavation of the Shaxi underground mine in China, a field lateral blast test with a single row was initially conducted, and the sonic wave speeds and goaf boundaries were measured to evaluate the damage degree to the remaining rock mass. A numerical model with three rows of boreholes was developed and calibrated against the lateral blast test with a single row. The calibrated numerical model was used to simulate the blasting process. The blast-induced damage characteristics with different charge structures in different rows were investigated, and the optimal charge structure for each row was obtained. The results indicate that the rock damage control effect can be achieved by a reasonable combination of charge structures and number of blasted rows, and it is more satisfactory with an increasing number of blasted rows and a reasonable decrease in the charge coefficient row by row. The rock breaking pattern at Cut X2 shows that most of the boulders are caused by the collapse of the remaining rock mass under the impact of blasting excavation. The ratio of broken rock in Part 4 indicates that the blast impact of the last row plays a dominant role in the damage to the remaining rock mass. Two optimized schemes were applied to the field of large-diameter-borehole lateral blasting, and satisfactory effects were achieved in the blast-induced damage control of the remaining rock mass.

Owing to the complex features of blasting vibration damage assessment systems, a gradient boosted machine (GBM) model is developed for the classification of residential structure damage (RSD) due to blasting vibrations of open pit mining. Twelve indicators are defined as the indices for the prediction of RSD in the proposed model. These are: peak particle velocity, dominant frequency, dominant frequency duration, distance, maximum safe charge per delay, compressive strength of mortar joints, ratio of brick area to house area, height of residential house, roof structures, beam-column frames, quality of construction, and site conditions. The GBM model is achieved by training 108 sets of measured data of blasting vibration. A 10-fold cross-validation procedure was applied to determine the optimal parameter values during modeling, and an external testing set was employed to validate the prediction performance of the model. Two performance measures – classification accuracy rate and Cohen’s kappa – have been employed. The analysis of accuracy together with kappa for the dataset demonstrate that the GBM model has high credibility as it achieves a comparable median classification accuracy rate and Cohen’s kappa values of 91.7% and 0.875 for the prediction of RSD, respectively.

The database of 254 rockburst events was examined for rockburst damage classification using stochastic gradient boosting (SGB) methods. Five potentially relevant indicators including the stress condition factor, the ground support system capacity, the excavation span, the geological structure and the peak particle velocity of rockburst sites were analyzed. The performance of the model was evaluated using a 10 folds cross-validation (CV) procedure with 80% of original data during modeling, and an external testing set (20%) was employed to validate the prediction performance of the SGB model. Two accuracy measures for multi-class problems were employed: classification accuracy rate and Cohen's Kappa. The accuracy analysis together with Kappa for the rockburst damage dataset reveals that the SGB model for the prediction of rockburst damage is acceptable.

The accurate identification of delay time in millisecond blasting plays an important role in the optimization of blasting design and reduction of vibration effect. Through a case study of a surge shaft blasting project, the capability of the EMD (empirical mode decomposition) method in identifying the delay time of short millisecond blasting with precise initiation was compared with the instantaneous energy method based on Hilbert-Huang transform (HHT). The recognition rate of the EMD method was more than 80%, while the instantaneous energy method was less than 25%. By analyzing the instantaneous energy of single-hole blasting signal, it was found that the instantaneous energy method was adaptable to millisecond blasting with delay time longer than half of the energy peak period. The EMD method was used to identify delay time of millisecond blasting in Zijinshan open-pit mine. According to the identification results, the blasting parameters were optimized for controlling the blast-induced vibration and reducing the large block ratio. The field data showed that the velocity peak of ground vibration was reduced by more than 30% under almost the same maximum charge per delay by the optimization of delay time and detonating detonators. Combining with slag-remaining blasting and burden optimization of the first row, the large block ratio was reduced to less than 3%. The research results proved that the identification method based on HHT was feasible to optimize the blasting design. The identification method is also of certain reference value for design optimization of other similar blasting projects.

Ground vibrations originating from bench blasting may cause damage to slopes, structures, and underground workings in close proximity to an operating open-pit mine. It is important to monitor and predict ground vibration levels induced by blasting and to take measures to reduce their hazardous effects. The aims of this paper are to determine the weaker protection objects by comparatively studying bench blasting induced vibrations obtained at surface and in an underground tunnel in an open-pit mine and thus to seek vibration control methods to protect engineering objects at the site. Vibrations arising from measurement devices at surface and in an underground tunnel at the Zijinshan Open-Pit Mine were obtained. Comparative analysis of the peak particle velocities shows that, in the greatest majority of cases, surface values are higher than underground values for the same vibration distance. The transmission laws of surface and underground vibrations were established depending on the type of rock mass, the explosive charge, and the distance. Compared with the Chinese Safety Regulations for Blasting (GB6722-2014), the bench blasting induced vibrations would not currently cause damage to the underground tunnel. According to the maximum allowable peak particle velocities for different objects, the permitted maximum charges per delay are obtained to reduce damage to these objects at different distances.

To eliminate undesired phenomena such as brow damage and excessive fines owing to the energy concentration on the collar of the ring, a fragment simulation using a charge scheme optimization algorithm is proposed based on modified Harries model in this article. First, the traversal algorithm for an arrangement of regular holes (holes charged to the collar) is proposed based on the analysis of the current interval charge design method in ring blasting. Second, a new developed mathematical model based on Harries model is introduced to predict the fragment size of the column charge using the superposition method. Then, the optimization criteria based on the calculated blasted fragment matrix are discussed. Finally, a case study is introduced to illustrate the usage and optimization procedure of the program. Ten trial blastings were conducted in the Tonglvshan copper mine to verify the feasibility and effectiveness of the optimization algorithm. The findings reveal that the probability of brow damage was reduced efficiently.

The charge structure is an important factor in the adjustment of the energy distribution of explosives and the control of the blasting effect, especially in an underground large-diameter longhole, for interval charge millisecond blasting design. To achieve a reasonable charge structure, a multi-planar detection optimization (MDO) algorithm for charge structures is proposed based on the Harries mathematical model and the superposition method. The vector size of a fragment is transformed into a scalar ruler, and the definition of the spatial non-uniformity evaluation factor is used in the MDO algorithm. A detailed methodology is implemented using a Visual LISP program and validated for a case study of the Fankou lead–zinc mine in China. The results reveal that the MDO algorithm can improve the rock fragmentation and increase the energy utilization rate of explosives in large-diameter longhole blasting operations. This algorithm could be extremely helpful in the process of underground mine blast optimization.

Large amounts of leaching residue are released into tailings dams from mines, and their acid content can cause environmental pollution. The aim of this study was to research the feasibility and value of a leaching residue backfill recycling method. The combination of property detection, laboratory tests (the neutralization method, strength test and diffusivity test) and numerical simulation methods (3D computational fluid dynamics (CFD) simulations of pipeline transportation properties) were used to assess the performance of the leaching residue backfill. The results show that backfill body with the cement:sand mass ratio of 1:3, the leaching residue:classified tailings ratio of 1:6, and slurry mass concentration of 71 wt % can meet the strength and pipeline self-flowing transportation requirements of mine backfill. The leaching residue is a good backfill aggregate, and its recovery ratio can reach 19.5 wt %. In addition, the recycling of leaching residue effectively alleviates the problem of mine waste emissions and protects the ecological environment surrounding the mining area. This study serves as a guide for the recycling of fine tailings and the environmental governance of the mining area.

A three-dimensional backfill pipeline transport model is developed using the computational fluid dynamics (CFD) technique, which is applied to study the pipeline transport properties of three-phase foam slurry backfill (TFSB). Based on rheological property tests and CFD simulations, the foam phase, pressure, and velocity in the pipeline system are investigated using the CFD mixture method for different bubble volume fractions and bubble diameters. The simulation results indicate that TFSB can maintain a steady state during pipeline transport, experience a markedly reduced pipeline transport resistance, and exhibit better liquidity than conventional cement slurry. Furthermore, as the bubble volume fraction increases, the resistance of the pipeline decreases and the fluidity improves. By contrast, the bubble diameter has little effect on the transport properties of TFSB. The combined results of CFD simulations, slump tests, and strength tests indicate that, when the bubble volume fraction is 15–20 vol %, TFSB can satisfy the necessary strength requirements and exhibit self-flowing transport. The CFD technique provides an intuitive and accurate basis for pipeline transport research and has the potential for wider application in studies of mine backfill.