A method to improve the quality of rock preparation for extraction with emulsion explosives in open-pit mines with high benches

Increasing the production capacity of open-pit and strip mines while ensuring the efficiency of the mining enterprise can be achieved through enhancing the quality of rock preparation prior to excavation. The use of emulsion explosives and the transition to the high-bench technology can reduce the cost of mining operations by optimizing the drilling and blasting parameters. The article reviews methods to improve the efficiency of rock preparation for extraction based on the applicable scientific and methodological principles and it proposes a method to regulate the density of emulsion explosives. Schemes are presented for calculation of drilling and blasting parameters when implementing technical measures aimed at improving the blasting quality through rock preparation for extraction in conditions of overburden and mining operations with bench height of 15 m and higher. Parameters of drilling and blasting operations on high benches are justified with differentiation of the charge density along the length of the blast hole by controlling the delivery of the gas-generating additive. A simulation has been performed and the results of pilot tests of the emulsion explosive charge density control at the Ural deposits are presented.

Calculation of blast hole charge amount based on three-dimensional solid model of blasting rock mass

The development and use of intelligent drilling rigs make it available to obtain accurate lithology data of blast drilling. In order to make full use of drilling data to improve blasting efficiency, the following research was carried out. First, a database is established to manage and store the blast hole data recognized by the intelligent drill. Secondly, the blast hole lithology data is taken as a sample, and the inverse distance square method is used to interpolate the blasting range's solid elements to generate a three-dimensional solid model of the blasting rock mass. Afterward, the blasting range polygon and stope triangle grid are used successively in the solid model to obtain the cut 3D solid model of the blasting rock mass; finally, the blast hole charge is calculated based on the cut 3D solid model of the blasting rock. The C++ programming language is used to realize all the blast hole charge amount processes based on the three-dimensional solid model of the blasting rock mass. With the application example of No. 918 bench blasting of Shengli Open-pit Coal Mine in Xilinhot, Inner Mongolia, the blast hole charge amount in the blasting area is calculated and compared with the results of single hole rock property calculation, the results show that the blast hole charge calculated by three-dimensional rock mass model can be effectively reduced.

Design method of blasthole charge structure based on lithology distribution

The density of geological exploration boreholes is one of the main bases for blasthole charge structure design. Due to the low density of geological exploration boreholes, it is impossible to obtain the blast hole rock formations' distribution accurately. With the development and application of intelligent drilling rigs, the lithology distribution data of the blasthole can be accurately obtained, and a blasthole charge structure design method based on the lithology distribution is proposed. The blasthole lithology data collected by the intelligent drilling rig is divided into 7 categories according to the rock hardness, and the adjacent strata with similar lithology are combined and divided into two groups of soft rocks and hard rocks. According to the rock stratum grouping data of the blasthole and the unit explosive consumption of each type of lithology, the explosive amount and charge length required for the soft rock group and the hard rock group can be calculated, respectively. Finally, the blasthole charge structure is designed according to the thickness and charge position of the hard rocks. With the C++ programming language, this method is realized and applied in the Shengli Open-pit Coal Mine of Inner Mongolia Autonomous Region of China. The application results show that, compared with the traditional hole charging structure design method, this method can realize accurate segmented charging of the hole, improve the blasting effect and the degree of rock fragmentation, and reduce the blasting cost.

Experimental Study of Gangue Layer Weakening with Deep-Hole Presplitting Blasting

Advances in coal mining technology and an increase in coal output are resulting in increasingly challenging conditions being encountered at coal seams. This is particularly so at thin coal seams, where a large number of hard rock layers known as gangue are often present, which seriously affect the normal operation of the shearer and reduce coal output. Therefore, the effective weakening of hard gangue layers in a coal seam is crucial to ensure that the shearer operates effectively and that coal output is maximized. In this paper, the weakening effect of deep-hole presplitting blasting technology on the hard gangue layer in a coal seam is studied via a similar simulation. Four test schemes are designed: (1) A blasting hole spacing of 200 mm with the holes offset vertically. (2) A blast hole spacing of 300 mm with the holes offset vertically. (3) A blast hole spacing of 200 mm with the holes parallel to the gangue layer. (4) A blasting hole spacing of 200 mm with the holes offset vertically and initiation of interval blasting. The effect of the different blasting hole spacings and arrangements and different detonation methods on the weakening of coal seam clamping by gangue is studied, and the best configuration is identified. This improves the effect of weakening the coal gangue layer by deep-hole presplitting blasting.

Analyzing methods of determining pre-destruction of blast hole vicinity

The level of deformation of the rock massif of a blasted slab must be planned in advance, depending on the required results of blasting. Thus the energy costs of barren rock overfilling as part of preparing for overburden excavation are inefficient. On the contrary, an increase in the blast energy spent on degrading and breaking the ore mass is an efficient measure of preparing for the excavation of mineral wealth. There are currently two methods used to determine the pre-destruction of a blasted rock massif. The first one is based on determining the number of strain waves passing through locations of borehole charges. However, this method fails to determine the preliminary rock destruction level. The second method is based on determining coefficients of the pre-destruction of a rock massif by these strain waves. The merit of this method is that it allows evaluating the quality pattern of the pre-destruction of a rock massif. The procedure of considering the fraction of energy of the strain waves, reflected by the shielding rock mass to the destructive amount of blasting charges and refracted to this destroyed rock, is proposed.

Experimental investigation on potential use of drilling parameters to quantify rock strength

The uniaxial compressive strength (UCS) represents the strength of the rock. It frequently requires during the introductory phase of mining projects such as tunneling, rock excavation, blast hole designs, etc. Usually, the determination of UCS of rocks is carrying out in a concerned laboratory. The main drawback of determining the UCS in a laboratory requires at least five core samples of high-grade quality. Many problems and limitations are associated with removing the core, and also preparing the test specimen for UCS is tedious, time-consuming, and expensive. Therefore an attempt is made to develop an efficient indirect method to estimate the UCS of rocks without using the core samples. In this experimental investigation, the drilling response, such as thrust, is gathered by drill tool dynamometer considering the different drill operating parameters. The prediction model is developed with a regression technique using the measured thrust and calculated torque. The prediction capacity and validation of the model are carried out using the standard procedure. The experimental results show that the model could explain the variance in UCS up to 93.60%. RMSE and MAPE values in terms of percentage are 3.49% and 11.27%, respectively. Besides, the model's validation is checked for sandstone and limestone having the UCS 28 MPa and 35 MPa, respectively, and yielded the best prediction results with an error of 8.51% and 8.01% suggesting that the developed model could predict the UCS of sedimentary rock types within acceptable error limit, and reasonably. The correlation of UCS of rocks and drilling specific energy is also tested and found that linear relationship between them with an R2 value of 92.10%.

Study on Dynamic Evolution Law of Blasting Cracks in Elliptical Bipolar Linear Shaped Charge Blasting

Based on LS-DYNA numerical simulation analysis and comparison with laboratory tests, the blasting crack development dynamic evolution mechanism of elliptical bipolar linear shaped charge is analyzed. The development law of rock crack and optimal radial decoupling coefficient under different blast hole diameters were studied. The results revealed that the blasting with elliptical bipolar linear shaped charge had a remarkable effect on the directional crack formation, and the maximum effective stress of rock close to the position of shaped charge in the direction of concentrating energy is about 2.3 times of that in the direction of nonconcentrated energy. Moreover, the directional crack could be formed by blasting with elliptical bipolar linear shaped charge with different hole diameters, whilst the length of the main crack was related to the radial decoupling coefficient. Particularly, the main crack reached the longest when the radial decoupling coefficient was 3.36.

Support Vector Machines for the Estimation of Specific Charge in Tunnel Blasting

Mine tunnels, short transportation tunnels, and hydro-power plan underground spaces excavations are carried out based on Drilling and Blasting (D&B) method. Determination of specific charge in tunnel D&B, according to the involved parameters, is very significant to present an appropriate D&B design. Suitable explosive charge selection and distribution lead to reduced undesirable effects of D&B such as inappropriate pull rate, over-break, under-break, unauthorized ground vibration, air blast, and fly rock. So far, different models are presented to estimate specific charge in tunnel blasting. In this study, 332 data sets, including geomechanical characteristics, D&B, and specific charge are gathered from 33 tunnels. The data are related to three dams and hydropower plans in Iran (Gotvand, Masjed-Solayman, and Siah-Bishe). Specific charge is modeled in inclined hole cut drilling pattern. In this regard, Support Vector Machine (SVM) algorithm based on polynomial Kernel function is used as a tool for modeling. Rock Quality Designation (RQD) index, Uniaxial Compressive Strength (UCS), tunnel cross-section area, maximum depth of blast hole, and blast hole coupling ratio are considered as independent input variables and the specific charge is considered as a dependent output variable. The modeling results confirm the acceptable performance of SVM in specific charge estimation with minimum error.

Optimization Technology of Frequency Conversion Constant Pressure Control System of Mine Emulsion Pump Station in Electrical Engineering and Automation Specialty

No matter in metal mines or coal mines, an emulsion pump station has a wide range of application market and can play an important role. In this paper, the frequency conversion constant pressure control system of the mine emulsion pump station is taken as the research object. The two kinds of water-based drawing fluids used are dispersed drawing fluid and emulsion drawing fluid. After the intelligent level of the equipment reaches a very high level, an environmentally friendly, safe, and efficient Internet of Things technology system will be added. Combined with 3D laser scanning technology based on self-scanning of road contours, the blast method is input to the terminals of the emulsion pump station for automatic blast hole positioning and semiautomation of the emulsion pump station. Combined with 5 g communication and other intelligent key technologies, it realizes high-end functions such as fault self-diagnosis, remote operation, and remote monitoring of the emulsion pump station and rock drill, which can be called full intelligent stage. The results show that the initial friction coefficient of drawing fluid A lubrication is 0.21, and then, with the extension of time, the friction coefficient gradually decreases to 0.14. The initial friction coefficient of drawing fluid B is 0.22, then it decreases rapidly to 0.13, then it is stable at 0.17, and then it remains basically unchanged. When the temperature is 55°C, the initial friction coefficient is 0.16 and then decreases to 0.12. Therefore, the frequency conversion constant pressure control system of the mine emulsion pump station should be selected according to the environment and application scenarios.

Pressure Relief by Blasting Roof Cutting in Close Seam Group Mining under Thick Sandstone to Enhance Gas Extraction for Mining Safety

Close seam group mining under thin immediate roofs and thick sandstone walls is typically performed with a strong mine pressure and gas concentration, which pose considerable risks to miners. In this study, the mechanism of pressure relief and permeability enhancement to enhance gas extraction for mining safety through blasting roof cutting were investigated through theoretical analyses, numerical simulations, and laboratory tests. The results revealed that, near the blast-hole, which produced numerous cracks, blasting disturbed the integrity of the thick-layer roofs and redistributed the stress near the blast-hole, which prevented violent mine pressure caused by excessive fracture distances on the thick and hard roofs, reduced the additional load on the support, increased vertical gas migration, and ameliorated the effect of gas drainage caused by high-level boreholes. The field applications of forced roof cutting through deep-hole blasting in the II 7224N face of the Renlou coal mine (Huaibei, Anhui, PR China) demonstrated that the occurrence of excessive pressure on the fully mechanized mining hydraulic support was prevented. The gas extraction volume of high-level boreholes was maintained at 6–8 m3/min; the extraction concentration was stable at approximately 35%; and the gas concentration in the upper corner of the coal face was lessened from 7% to <1%, which ensured normal mining in the coal face. The current results can provide data reference and a theoretical basis for roof management and gas control of the same type of coal face.