Novel Soft ComputingModel for Predicting Blast-Induced Ground Vibration in Open-Pit Mines Based on the Bagging and Sibling of Extra Trees Models

This study considered and predicted blast-induced ground vibration(PPV)in open-pit mines using bagging and sibling techniques under the rigorous combination of machine learning algorithms.Accordingly,four machine learning algorithms,including support vector regression(SVR),extra trees(ExTree),K-nearest neighbors(KNN),and decision tree regression(DTR),were used as the base models for the purposes of combination and PPV initial prediction.The bagging regressor(BA)was then applied to combine these base models with the efforts of variance reduction,overfitting elimination,and generating more robust predictive models,abbreviated as BA-ExTree,BAKNN,BA-SVR,and BA-DTR.It is emphasized that the ExTree model has not been considered for predicting blastinduced ground vibration before,and the bagging of ExTree is an innovation aiming to improve the accuracy of the inherently ExTree model,as well.In addition,two empirical models(i.e.,USBM and Ambraseys)were also treated and compared with the bagging models to gain a comprehensive assessment.With this aim,we collected 300 blasting events with different parameters at the Sin Quyen copper mine(Vietnam),and the produced PPV values were also measured.They were then compiled as the dataset to develop the PPV predictive models.The results revealed that the bagging models provided better performance than the empirical models,except for the BA-DTR model.Of those,the BA-ExTree is the best model with the highest accuracy(i.e.,88.8%).Whereas,the empirical models only provided the accuracy from 73.6%–76%.The details of comparisons and assessments were also presented in this study.

Numerical Study on Mechanism of Blast-Induced Damage Considering Guiding Effect of Water Jet Slot

Damage is one of the most important characteristics of rock failure.Studying the damage mechanism of rock blasting under the guiding effect of the water jet slot and revealing the mechanism of controlled blasting with water jet assistance are crucial.In this study,a rock-like material was chosen as the research object for the calibration experiment of the numerical model.The numerical simulation models were then established by ANSYS/LS-DYNA,and the blastinduced damage mechanism under the guiding effect of the water jet slot was analyzed according to the blasting theory.The results indicated that explosive energy accumulates toward the direction of the slot as the guiding effect of the water jet slot,which allows the rock mass in the direction of the slot bear more damage.Meanwhile,the rock mass in the middle of the connection line between two blast-holes bears more damage under the combination of the effect of the explosion stress wave and guiding effect of water the jet slot on the detonation gas during double-slotted borehole blasting,which results in the formation of a gourd-shaped blast-induced damage area.In addition,the influence of the water jet slot on blast-induced damage varies depending on the blasting-process stage.

Modified scaled distance regression analysis approach for prediction of blast-induced ground vibration in multi-hole blasting

The blast-induced ground vibration prediction using scaled distance regression analysis is one of the most popular methods employed by engineers for many decades. It uses the maximum charge per delay and distance of monitoring as the major factors for predicting the peak particle velocity(PPV). It is established that the PPV is caused by the maximum charge per delay which varies with the distance of monitoring and site geology. While conducting a production blasting, the waves induced by blasting of different holes interfere destructively with each other, which may result in higher PPV than the predicted value with scaled distance regression analysis. This phenomenon of interference/superimposition of waves is not considered while using scaled distance regression analysis. In this paper, an attempt has been made to compare the predicted values of blast-induced ground vibration using multi-hole trial blasting with single-hole blasting in an opencast coal mine under the same geological condition. Further,the modified prediction equation for the multi-hole trial blasting was obtained using single-hole regression analysis. The error between predicted and actual values of multi-hole blast-induced ground vibration was found to be reduced by 8.5%.

Early hyperbaric oxygen therapy inhibits aquaporin 4 and adrenocorticotropic hormone expression in the pituitary gland of rabbits with blast-induced craniocerebral injury

In the present study, rabbits were treated with hyperbaric oxygen for 1 hour after detonator-blastinduced craniocerebral injury. Immunohistochemistry showed significantly reduced aquaporin 4 expression and adrenocorticotropic hormone expression in the pituitary gland of rabbits with craniocerebral injury. Aquaporin 4 expression was positively correlated with adrenocorticotropic hormone expression. These findings indicate that early hyperbaric oxygen therapy may suppress adrenocorticotropic hormone secretion by inhibiting aquaporin 4 expression.

An ANN-based approach to predict blast-induced ground vibration of Gol-E-Gohar iron ore mine,Iran

Blast-induced ground vibration is one of the inevitable outcomes of blasting in mining projects and may cause substantial damage to rock mass as well as nearby structures and human beings.In this paper,an attempt has been made to present an application of artificial neural network(ANN)to predict the blast-induced ground vibration of the Gol-E-Gohar(GEG)iron mine,Iran.A four-layer feed-forward back propagation multi-layer perceptron(MLP)was used and trained with Levenberg–Marquardt algorithm.To construct ANN models,the maximum charge per delay,distance from blasting face to monitoring point,stemming and hole depth were taken as inputs,whereas peak particle velocity(PPV)was considered as an output parameter.A database consisting of69data sets recorded at strategic and vulnerable locations of GEG iron mine was used to train and test the generalization capability of ANN models.Coefficient of determination(R2)and mean square error(MSE)were chosen as the indicators of the performance of the networks.A network with architecture4-11-5-1and R2of0.957and MSE of0.000722was found to be optimum.To demonstrate the supremacy of ANN approach,the same69data sets were used for the prediction of PPV with four common empirical models as well as multiple linear regression(MLR)analysis.The results revealed that the proposed ANN approach performs better than empirical and MLR models.

Propagation and Coalescence of Blast-Induced Cracks in PMMA Material Containing an Empty Circular Hole Under Delayed Ignition Blasting Load by Using the Dynamic Caustic Method

In this paper,dynamic caustic method is applied to analyze the blast-induced crack propagation and distribution of the dynamic stress field around an empty circular hole in polymethyl methacrylate(PMMA)material under delayed ignition blasting loads.The following experimental results are obtained.(1)In directional-fracture-controlled blasting,the dynamic stress intensity factors(DSIFs)and the propagation paths of the blast-induced cracks are obviously influenced by the delayed ignition.(2) The circular hole situated between the two boreholes poses a strong guiding effect on the coelesence of the cracks,causing them to propagate towards each other when cracks are reaching the circular hole area.(3)Blast-induced cracks are not initiated preferentially because of the superimposed effect from the explosive stress waves on the cracking area.(4) By using the scanning electron microscopy(SEM)method,it is verified that the roughness of crack surfaces changes along the crack propagation paths.

Blast-Induced Traumatic Brain Injury Triggered by Moderate Intensity Shock Wave Using a Modified Experimental Model of Injury in Mice

Background： The increasing frequency of explosive injuries has increased interest in blast-induced traumatic brain injury （bTBI）. Various shock tube models have been used to study bTBI. Mild-to-moderate explosions are often overlooked because of the slow onset or mildness of the symptoms. However, heavy gas cylinders and large volume chambers in the model may increase the complexity and danger. This study sought to design a modified model to explore the effect of moderate explosion on brain injury in mice. Methods： Pathology scoring system （PSS） was used to distinguish the graded intensity by the modified model. A total of 160 mice were randomly divided into control, sham, and bTBI groups with different time points. The clinical features, imaging features, neurobehavior, and neuropathology were detected after moderate explosion. One-way analysis of variance followed by Fisher＇s least significant difference posttest or Dunnett＇s t 3-test was performed for data analyses. Results： PSS of mild, moderate, and severe explosion was 13.4 ± 2.2, 32.6 ± 2.7 （t = 13.92, P 〈 0.001; vs. mild group）, and 56.6 ± 2.8 （t = 31.37, P 〈 0.001; vs. mild group）, respectively. After moderate explosion, mice showed varied symptoms of malaise, anorexia, incontinence, apnea, or seizure. After bTBI, brain edema reached the highest peak at day 3 （82.5% ± 2.1% vs. 73.8% ± 0.6%. t - 7.76, P 〈 0.001）, while the most serious neurological outcomes occurred at day 1 （Y-maze： 8.25 ±2.36 vs. 20.00 ± 4.55, t = -4.59, P=0.048; 29.58% ± 2.84% vs. 49.09% ±11.63%, t = -3.08, P = 0.008; neurologic severity score： 2.50 ± 0.58 vs. 0.00±0.00, t = 8.65, P = 0.016）. We also found that apoptotic neurons （52.76% ± 1.99% vs. 1.30% ± 0.11%, t =57.20, P 〈 0.001 ） and gliosis （2.98 ± 0.24 vs. 1.00 ± 0.00, t = 14.42, P = 0.021） in the frontal were significantly higher at day 3 post-bTBI than sham bTB1. Conclusions： We provide a reliable, reproducible bTBI model in mice that can produce a graded explosive waveform similar to the free-field shock wave in a controlled laboratory environment. Moderate explosion can trigger mild-to-moderate blast damage of the brain.

Prediction of characteristic blast-induced vibration frequency during underground excavation by using wavelet transform

Blast-induced vibration produces a very complex signal,and it is very important to work out environmental problems induced by blasting.In this study,blasting vibration signals were measured during underground excavation in carbonaceous shale by using vibration pickup CB-30 and FFT analyzer AD-3523.Then,wavelet analysis on the measured results was carried out to identify frequency bands reflecting changes of blasting vibration parameters such as vibration velocity and energy in different frequency bands.Frequency characteristics are then discussed in view of blast source distance and charge weight per delay.From analysis of results,it can be found that peak velocity and energy of blasting vibration in frequency band of 62.5–125 Hz were larger than ones in other bands,indicating the similarity to characteristics in the distribution band(31–130 Hz)of main vibration frequency.Most frequency bands were affected by blasting source distance,and the frequency band of 0–62.5 Hz reflected the change of charge weight per delay.By presenting a simplified method to predict main vibration frequency,this research may provide significant reference for future blasting engineering.

Numerical study on dynamic mechanism of brain volume and shear deformation under blast loading

Blast-induced traumatic brain injury(b-TBI)is a kind of significant injury to soldiers in the current military conflicts.However,the mechanism of b-TBI has not been well understood,and even there are some contradictory conclusions.It is crucial to reveal the dynamic mechanism of brain volume and shear deformations under blast loading for better understanding of b-TBI.In this paper,the numerical simulation method is adopted to carry out comprehensive and in-depth researches on this issue for the first time.Based on the coupled Eulerian-Lagrangian method,the fluid-structure coupling model of the blast wave and human head is developed to simulate two situations,namely the head subjected to the frontal and lateral impacts.The simulation results are analyzed to obtain the underlying dynamic mechanisms of brain deformation.The brain volume deformation is dominated by the local bending vibration of the skull,and the corresponding frequency for the forehead skull under the frontal impact and the lateral skull faced to the lateral impact is as high as 8 kHz and 5 kHz,respectively.This leads to the high-frequency fluctuation of brain pressure and the large pressure gradient along the skull,totally different from the dynamic response of brain under head collisions.While the brain shear deformation mainly depends on the relative tangential displacement between the skull and brain and the anatomical structure of inner skull,being not related to the brain pressure and its gradient.By further comparing the medical statistics,it is inferred that diffuse axonal injury and brain contusion,the two most common types of b-TBI,are mainly attributed to brain shear deformations.And the von Mises stress can be adopted as the indicator for these two brain injuries.This study can provide theoretical guidance for the diagnosis of b-TBI and the development of protective equipment.

Analysis on the Influence Factors of Directional Controlled Blasting Assisted by Water Jet

Directional expansion of blast-induced crack is always the common purpose for directional controlled blasting. As it has been demonstrated that slot which located at the side of blasthole can function as a guidance for blast energy, let the stress concentration at the direction of water jet slot. Therefore, it is meaningful to investigate the influence factors of directional controlled blasting with water jet assistance. In this paper, the influence on the guiding characteristics of the water jet slot during the propagation of blast-induced crack by the change of length-width of slot was simulated by ANSYS/LS-DYNA. The results indicate that if the distance from blasthole exceeds the limit, the influence on the guiding characteristics by the change length-width of the slot will get smaller and smaller, and when the width of water jet slot remains the same, the stress shows a monotonic increasing trend with the increase of the length of water jet slot, and the stress reaches its maximum value when the length-width of water jet slot is 0.075m×0.0070m. Moreover, based on stress wave theory and rock fracture theory, the influential mechanism for both the law of transmission of stress wave and of crack propagation by natural fracture and water jet slot were analyzed. The criteria for blast-induced crack propagation were established.