Roadway Excavation Research Articles

Discontinuous Deformation Characteristics of Deep Buried Roadway Roofs and Linkage Control of Thick Layer Cross-Boundary Anchorage: A Case Study

After deep mining, the discontinuous deformation characteristics of roadway roofs become more and more obvious, resulting in the emergence of separation fractures in the rock mass, which seriously affects the stability of the roof rock mass. By taking the air return roadway 21204 (ARR 21204) in Hulusu Coal Mine as the engineering background, this article reveals the discontinuous deformation characteristics of deep buried roadway roofs through field research, numerical simulation, theoretical analysis and engineering practice. After roadway excavation, the rock masses in different shallow roof horizons show different degrees of stress unloading, resulting in the occurrence of discontinuous deformation phenomena in rock masses. With the rise of the roof rock horizon, the degree of discontinuous deformation fades away until a continuous deformation zone with small deformation and stable rock strata appears. In addition, with the increase in the roadway buried depth, the extent of the discontinuous deformation of the roof and its extended range tend to increase. In view of the discontinuous deformation control of the roof, the technology of linkage control of thick layer cross-boundary anchorage is proposed. By establishing the thick anchorage ring of the roof, the bolts cross the discontinuous deformation zone to support the stable rock strata in the deep continuous deformation zone, thereby realizing the linkage control of the large and small displacement of the rock masses in these two zones and limiting the progressive damage of the roof rock mass from shallow to deep. The industrial test shows that the scope of the separation fracture zone on the roof is controlled at the shallow stratum of 0.85 m due to the great decrease in the surface displacement of roadway, which effectively restricts the progressive upward extension of the discontinuous deformation zone of the roof. The research results can provide references for the safe and efficient control of roadway roofs under deep mining conditions.

Vision and Inertial Navigation Combined-Based Pose Measurement Method of Cantilever Roadheader

Pose measurement of coal mine excavation equipment is an important part of roadway excavation. However, in the underground mining roadway of coal mine, there are some influencing factors such as low illumination, high dust and interference from multiple equipment, which lead to the difficulty in the position and pose measurement of roadheader with low measurement accuracy and poor stability. A combination positioning method based on machine vision and optical fiber inertial navigation is proposed to realize the position and pose measurement of roadheader and improve the accuracy and stability of the position and pose measurement. The visual measurement model of arm roadheader is established, and the optical fiber inertial navigation technology and the spatial coordinate transformation method are used. Finally, the Kalman filter fusion algorithm is used to fuse the two kinds of data to get the accurate roadheader pose data, and the inertia is compensated and corrected. Underground coal mine experiments are designed to verify the performance of the proposed method. The results show that the positioning error of the roadheader body using this method is within 40 mm, which meets the positioning accuracy requirements of roadway construction. This method compensates for the shortcomings of low accuracy and poor reliability of single vision measurement, single inertial navigation measurement and single odometer measurement.

Control Technology of Roof-Cutting and Pressure Relief for Roadway Excavation with Strong Mining Small Coal Pillar

In order to solve the problem of serious deformation and failure of surrounding rock and difficult maintenance of gob-side entries with strong mining-induced small coal pillars, taking the A110607 return airway of the Shanwenjiaba Coal Mine as the engineering background, the key parameters of roof-cutting and pressure relief control technology for roadway excavation with strong mining-induced small coal pillars were studied by using two-way concentrated blasting roof-cutting and pressure relief technology, combined with theoretical analysis, numerical simulation and a field industrial test. A collaborative control scheme of “roof-cutting pressure relief + anchor cable combined support” is proposed. The test results show that when the height of roof-cutting is 8 m, the angle of roof-cutting is 15°, and when the width of the coal pillar is 3 m, the effect of roof-cutting and pressure relief is the best. Through the field blasting test, it was determined that the blast hole spacing was 800 mm, 321 charge structure was used in the intact roof, and 221 or 211 charge structures were used in the broken roof and geological structure zones. During the driving and strong mining period, the roof and floor movement of the roof-cutting section of the roadway excavation was reduced by about 38% compared with the uncut section, and the deformation of the two sides of the roadway was reduced by about 44% compared with the uncut section. It shows that the collaborative control scheme of “roof-cutting pressure relief + anchor cable combined support” has a good effect on the roadway excavation driving of small coal pillars in strong mining.

Study on the Evolution Law of Deep Rock Cracks and the Mechanism of Graded Gradient Support

The surrounding rock of deep roadway is mostly composed of fractured rock. The deformation of roadway surrounding rock is complicated, which not only involves the stress change, but also involves the support means. This paper aims to study the deformation and fracture evolution law of surrounding rock in deep underground engineering. According to the stress rebalancing characteristics, after roadway excavation, the development and evolution characteristics of surrounding rock cracks are studied. At the same time, different seepage zones are divided according to the relationship between surrounding rock failure and its total stress–strain, that is, complete seepage zone, seepage shielding zone, and proto-rock seepage zone. The crack distribution characteristics of surrounding rock are studied, and the graded control of gradient support is proposed. In the broken area, the gradient bearing shell outside the roadway is achieved by means of bolting and high-strength grouting. As the cracks and pore sizes in the plastic zone gradually decrease along the radial stress direction of the roadway, and the open cracks gradually change into closed cracks, it is difficult for ordinary grouting materials to complete better consolidation and filling. Therefore, small particle size grouting reinforcement materials are studied. The plastic zone (fracture zone) is reinforced with nano-scale grouting material, and the internal three-dimensional gradient bearing shell is formed by combining with the anchor cable. This research plays an important guiding role in the stability of deep roadway surrounding rock.

Numerical Study on Deformation and Failure Characteristics of Rectangular Roadway

In the practical processes of coal mines and tunnel, rectangular roadways are widely used in the underground environment. However, the stress distribution law of the rock mass around the rectangular roadways is relatively complicated that is influenced by different parameters, such as the in situ stress, geological structure, and properties of the surrounding rock mass. It is extremely significant to conduct systematic and in-depth research regarding the stress distribution and deformation failure mechanism of the rock mass around the rectangular roadways. Based on theoretical analysis, the stress distribution law of the surrounding rock of rectangular roadway under different rock mass strength grades is studied directly through rectangular roadway in this paper. This further reveals the distribution law of secondary stress field after excavation of rectangular roadway. A coal mine intends to excavate a roadway in rock mass, and then, the rectangular roadway is simulated by FLAC3D software. Then, the strain distribution and failure types of roadway surrounding rock under different rock mass properties are obtained. The results show that the failure of rectangular roadway is mainly shear failure and tensile failure. The roof and floor of roadway are mainly tensile failure, and the side of roadway is mainly shear failure. Moreover, the stress shifting and distribution of the rock mass around rectangular roadways is a complicated dynamic variation process. The damage degree of the floor and roof of the rectangular roadway is greater than that of the two sides of the roadway. Its variation is mainly related to the strength of surrounding rock mass.

Study on Mechanical Properties of Ring Sandstone Specimen under Temperature and Water Coupling Dynamic Compression

The excavation of hard rock roadways in coal mines is often in the environment of underground water and high ground temperature, and it is easy to be affected by the dynamic load, which leads to roadway destruction and increases the difficulty of roadway support. The ring sandstone specimens with different inner diameters (0~25 mm) were treated with temperature and water coupled, and the dynamic compression test was produced by the Hopkinson pressure rod device (SHPB). The experimental results indicate that the coupling effect of temperature and water reduces the dynamic performance of sandstone specimens. XRD test results showed that the composition of sandstone specimens did not change before and after warm water coupling, and no new substances were found. Dynamic properties of ring sandstone specimens with different inner diameters weaken with the increase in inner diameters. With the increasing inner diameter of ring sandstone specimens, the energy dissipation per unit volume increases the dynamic compressive strength decreases, and the degree of breakage increases. Fracture morphology, average strain rate, and dynamic peak strain of ring sandstone specimens increase with inner diameter.

Mechanism and Application of Layered Grouting Reinforcement for Fractured Coal and Rock Roadway

This paper takes the ZF3806 working face of Shuiliandong Coal Mine in Binxian County, Shaanxi Province as the engineering background. Aiming at the problems of the development of surrounding rock cracks and roof breakage encountered in the process of roadway excavation and support and based on the composite beam theory, the method of layered grouting reinforcement of roadways is proposed according to the deformation and failure of the roadway roof and the internal drilling conditions. At the same time, combined with the splitting grouting mechanism, the roadway is strengthened and supported by layered grouting of “shallow bolt grouting + deep cable grouting”. The “shallow” and “deep” form a complete and stable composite beam support structure. After grouting, the bending moments of “shallow” and “deep” support beams decrease by 20.78 × 106 N·m and 26.50 × 106 N·m, respectively. The support scheme is applied to the field test, and the grouting effect is analyzed and monitored. The research results show the layered grouting support scheme of “shallow bolt grouting + deep cable grouting” can significantly improve the structural integrity of the roadway roof. The displacement of the two sides is within the controllable range, and the support role of the bolt and cable is entirely played through grouting. The roof displacement of the roadway is reduced by 65% on average, and the bolt failure and steel belt fracture are significantly reduced, which effectively controls the deformation and damage of the roadway and reduces the maintenance cost of the roadway while ensuring safe mining. The study’s findings could be useful in treating broken surrounding rock in other coal mine roadways.

Curve forming prediction of coal mine roadway based on RBF interpolation.

Underground roadway excavation is a complex process, especially roadway curved excavation. In addition, the rationality of the design of coal mine roadway excavation scheme directly affects the speed of roadway excavation. The more reasonable the scheme design, the more conducive to rapid excavation. In order to avoid the influence of invalid construction on the efficiency of roadway excavation, this paper studies the forming of roadway bend. Based on the analysis of the tunneling process of the roadway curve, the mathematical model of the roadway curve is established. Taking the turning radius of the roadway curve as the evaluation index, the influence of various factors on the roadway curve excavation is analyzed. The research shows that the radius of the roadway curve increases with the increase of the feed rate, the working space position of the roadheader and the required width of the roadway, and decreases with the increase of the working space angle. Then, combined with the advantages of KNN algorithm, an interpolation model for calculating the radius of the curve is established based on RBF algorithm, and the radius of the tunnel curve is reconstructed and predicted. It provides a basis for the rational design of the construction process of the roadway bend and a reliable numerical algorithm for the design of the radius of the roadway bend. It also provides a theoretical basis for improving the efficiency of high roadway excavation in coal mines.

Study on Sealing Depth Optimization of Gas Drainage Borehole in Coal Seam

To determine the reasonable sealing depth of the drainage borehole in the coal seam along lane W33011 of the Sihe coal mine and improve sealing quality based on the mine geological conditions, FLAC3D numerical simulation software was used to simulate the stress distribution and fracture development of coal body around the roadway after the roadway excavation. YFZ3 hole sealing quality detector was adopted to detect the hole sealing quality and leakage position. The reasonable drilling depth in the test area was determined to be 15m, effectively improving the gas drainage effect. This technology has important reference significance for improving the quality of hole sealing in other mines.

The Optimized Roadway Layouts and Surrounding Rock Control Technology of the Fully Mechanized Mining Surface with Large Mining Heights in High-Gas Mines

Many problems exist in the layout of working surfaces in high-gas mines, such as the low efficiency of roadway excavation, difficulties in maintenance after excavation, and serious resource wastes due to difficulties in recovering coal pillars between roadways. Taking the project profile in the west wing mining area of Sihe Coal Mine as the background, this work proposed an optimization plan for the staggered-layer arrangement of roadways. The minimum retained size of the coal pillar was calculated through theoretical analysis, and the plastic failure and deformations of surrounding rocks under different coal pillar sizes and roadway layouts were compared based on finite difference numerical simulations. The reasonable retained size of the coal pillar was determined to be 45 m, and the roadway layout was determined according to the distribution of coal and rock strata in the mining field. The technical measures of base angle pressure relief blasting and strengthening support were proposed to ensure the safety and stability of surrounding rocks of roadways during the service period after the layout plan was optimized. Similar simulation tests were used to study the damage deformations and stress changes of the blasting pressure relief floor. On-site tests showed that the optimized roadway layout greatly improved the recovery rate of coal resources. In addition, surrounding rocks had good stability, and they could be simply repaired or serve the next working surface directly without being repaired. These research results provide a scientific basis and useful reference for similar projects.

Study on gas extraction efficiency using in-seam borehole method considering influence of plastic zone induced by borehole drilling

Gas hazards pose a serious threat to the safety of coalmines. Gas extraction through in-seam boreholes is an important technical approach for preventing gas hazards and achieving rational exploitation of gas as a clean resource. Improper extraction design may result in inefficient gas extraction and create the risk of gas emission overrun, or even coal and gas burst during mining process. Gas extraction efficiency is associated with the permeability of the coal seam, which is affected by the integrity and porosity of the coal seam. The change in permeability in plastic zones induced by borehole drilling or roadway excavation is usually not sufficiently considered when designing a gas extraction scheme and predicting the gas extraction efficiency. In view of this, this research investigated gas extraction efficiency using in-seam borehole method considering influence of drilling/excavation induced plastic zone. Based on a gas extraction project in the Huainan mining area of China, site measurements were performed to test the pressure distribution characteristics along the gas extraction pipe. Subsequently, the radius of the plastic zone around the borehole was deduced based on elastic–plastic theory. Furthermore, a gas flow equation under extraction conditions was proposed, and the apparent permeability of the coal seam was analyzed by considering the plastic deformation induced by roadway excavation and borehole drilling. Finally, a three-dimensional model was built, and the gas flow performance was simulated by considering the influence of the plastic zone. The calculated radius of the plastic zone was compared with the analytical results. The evolution characteristics of the gas pressure and the effective extraction radius were obtained. In addition, optimized measures for the design of extraction boreholes are proposed.

New Technology of Pressure Relief Control in Soft Coal Roadways with Deep, Violent Mining and Large Deformation: A Key Study

Previous studies have shown that the influence of deep dynamic pressure on the surrounding rock control of a coal roadway is one of the difficulties in mine roadway support. Based on the investigation of the headgate 11231 in a coal mine, this study analyzes the damage characteristics of coal roadway surrounding rock affected by deep dynamic pressure, expounds on the difficulties of controlling the roadway surrounding rock, and creatively proposes a cooperative control technology of external anchor–internal unloading for regulating large deformation of roadways. The vertical stress distribution and transfer law of surrounding rock with different hole-making depths, spacing, and lengths after roadway excavation were simulated and studied, and an appropriate parameter range of hole-making space in the stage without dynamic pressure influence was obtained. Considering the influence of mining dynamic pressure, the surrounding rock pressure relief effect of each optimized hole-making parameter was analyzed. In addition, the optimal hole-making parameters (the hole-making depth, spacing, and length were 8 m, 3.2 m, and 3 m, respectively) that can effectively reduce the high stress of roadway shallow surrounding rock in two stages (without and with dynamic pressure) and ensure integrity of the shallow surrounding rock were obtained. The actual field application shows that the new technology can reduce the higher rib deformation by approximately 850 mm and achieve a good surrounding rock control effect. The research and practice show that the pressure relief control for soft coal roadways with deep, violent mining and large deformation has achieved success, providing technical support for the maintenance of the same type of roadway.

Study on Mechanical Characteristics of Rock Surrounding the Roadway under Different Section Shapes

In order to understand the instability characteristics of surrounding rock during deep roadway excavation, the influence of different section shapes on the stability of surrounding rock was systematically analyzed. Four sections of roadway with circular, rectangular, semicircular arch and three-center arch were studied. Simulation revealed that the maximum principal stress concentration and pressure relief degree of the three-center arch roadway is the highest, the minimum principal stress relief degree of the rectangular roadway is highest, the roof subsidence of the semicircular arch roadway is the lowest, the roof subsidence and left and right side displacement of the rectangular roadway are the highest, the surrounding rock failure areas of the circular roadway are evenly distributed, the surrounding rock failure areas of the other shape roadways are arch-distributed and the surrounding rock failure of the two sides of the rectangular roadway is the deepest. The mining stress environment coefficient is defined according to the stress state of the rock surrounding the roadway, and the range in which the coefficient is greater than 0.2 is defined as the destructive danger area. We found that the stability of the rock surrounding a circular roadway is greater than that of a semicircular arch roadway, a three-center arch roadway and a rectangular roadway.

Pose Detection and Automatic Deviation Correction Control Strategy of Crawler Walking Equipment in Coal Mines

Autonomous navigation technology is the basis of underground crawler walking equipment automation. Based on research of the sector laser pose parameter detection method, a pose detection system based on a cross laser is proposed. The mathematical model between pose parameters, laser receiver measurement data and tilt sensor measurement data is established by vector algorithm and the expression of key pose parameters is deduced. This paper studies the deviation correction control strategy of crawler walking equipment and puts forward the point deviation correction control strategy based on roadway excavation technology. Firstly, the end position of the path is determined according to the initial pose of the roadheader. Then, Bessel curve is used to plan the path between the starting point and the endpoint, and the pure tracking algorithm is used to track the planned path. The measurement errors of X and Y coordinates and yaw angle of roadheader within 10 80 m shall not exceed 10 mm, 32 mm and 0.65°. Using the point deviation correction strategy, the positioning error of the roadheader at the end of the path is less than 13 mm, and the yaw angle error is less than 0.16°. In the deviation correction process, the maximum angular velocity of the roadheader is 0.07 rad/s, which is less than 0.82 rad/s of the conventional deviation correction strategy. The results show that the point deviation correction strategy can not only ensure the accuracy of motion control, but also improve the stability of equipment motion.

Study on Occurrence Mechanism and Prevention Technology of Rock Burst in Narrow Coal Pillar Working Face under Large Mining Depth

This paper presents a collaborative control scheme involving “unloading-solidifying” to prevent rock bursts during narrow pillar recovery at large mining depths. In this study, the stress distribution rule of coal rock mass during the excavation and mining process is studied, and the energy accumulation characteristics of the overlying hard and thick roof structure are investigated. In this way, the rock burst inducing mechanism of the narrow coal pillar working face under complex conditions is investigated. The results show that the peak lateral bearing pressure of the goaf and the maximum horizontal principal stress provide the static load condition for the occurrence of rock burst during roadway excavation. Affected by the superposition of “near-field high static load + far-field dynamic load”, it is extremely easy to reach the critical destabilization value during the mining period at the narrow coal pillar working face. According to the monitoring results, the developed coordinated control scheme, which focuses on the strong pressure relief and strong support in near-field high-bearing pressure coal mass and the pressure relief in far-field high-level hard roof with an advanced pre-cracking roof, can effectively avoid the occurrence of rock burst accidents on narrow coal pillar working face.

Numerical modelling of coal and gas outburst initiation using energy balance principles

Coal and gas outburst is a common mining hazard as it cannot be readily predicted due to complex processes controlling its occurrence. Understanding these complex processes such as gas flow, mechanical properties and behaviour, stress regimes, and geological structures, is required to enable mitigating the outbursts. The most current thresholds proposed for outburst prediction are empirically based thus ignoring the physical processes involved. While numerical modelling is a powerful tool to simulate the involved physical mechanism in coal and gas outbursts, the use of thresholds for outburst initiation in numerical models has not attracted enough attention to date. In this study, the law of conservation of energy is used to determine the moment of the outburst occurrence; the energy of which is obtained through numerical simulation. Different sources of energy including elastic energy and, free and desorbed gas energies linked to the complex physical processes are modelled and discussed. Different mechanical properties of coal are assigned to discuss the distinction of energy values between normal coal and coal affected by geological structures (known as deformed coal). A 30 m long roadway excavation that penetrates through both normal and deformed coals is simulated to assess the effect of induced stress on outburst initiation during roadway development. In addition, the effects of initial gas pressure and damaged area on the propensity of outburst events are analysed. The numerical model can successfully simulate gas outbursts caused by deformed coal, which poses a higher outburst risk. In addition, the modelling results demonstrate that by increasing the gas pressure in the coal seam, outburst happens in the earlier stages of the roadway development, and more intense outburst can be expected.

Gas coal delamination recognition method based on the Fisher discriminant function of trace element characteristics

Abstract Numerous geological factors will affect determining the well bottom position by well depth during the construction of coalbed methane wells, resulting in inaccurate results. By using the trace element characteristics of coal samples to determine the source layer of coal samples, it is possible to avoid making incorrect assumptions. The groove method was used in this study to collect 40 gas coal samples from seven gas coal seams in Dingji Mine, which were then sealed and stored. The contents of 40 different trace elements were analyzed in the samples, and the types and content characteristics of trace elements in each coal seam were determined preliminarily through content distribution map analysis. Simultaneously, the SPSS analysis software was used to analyze the 1600 trace element test data from various coal seams, and cluster analysis was performed using the average link method between classes. The clustering tree diagram was created, and the discrimination was calculated using the distance between classes and samples. This study analyzed the typical explanatory variables and established the Fisher discriminant function for coal seam identification. Accordingly, identifying gas coal stratification requires only measuring the concentrations of nine trace elements (typical explanatory variables) in the coal seam being discriminated against. This method can be used in Dingji mine to determine the final hole horizon of surface coalbed methane wells and eliminates the risk of accidentally exposing coal seams during the excavation of an underground roadway.

Study on air curtain cooperative spray dust removal in heading face based on swirl theory

With the improvement of mechanization, fully mechanized excavators are widely used in roadway excavation, which produces a large number of fine dust particles in the process of tunneling. The smaller the dust particle size, the greater the impact of the environment, and the more difficult it is to be captured. Experiments and numerical simulations have been used to study the cooperative spray dust removal of the wall-mounted air duct based on the swirl theory, which is to prevent the escape of dust particles in the long-pressure and short extraction ventilation. Under the condition that the power of the push-in and extraction fans remain unchanged, it is determined that when the aspect ratio of air outlet is 6:1, the airflow can form an annular vortex area on the left side of the roadway, and the airflow velocity in 30 % of the area is greater than 1 m/s. When the opening angle is between 120° and 150°, the wall effect of airflow movement is weak, and the airflow velocity of 70 % of the cross-sectional area of the roadway is larger than 2 m/s, which enables the air curtain to block about 70 % of the dust. Under the action of the swirl air curtain, when the spray pressure is 6 MPa, 80 % of the droplets have a particle size of less than 2.5e-5 m, and the spray effect is better. The droplets move to the tunnel section under the swirling flow, and actively control the dust, establishing an air curtain-droplet flow field, thereby blocking and capturing the excavation dust.

Digital image processing-based automatic detection algorithm of cross joint trace and its application in mining roadway excavation practice

This paper proposes a digital image processing-based detection algorithm for cross joint traces of coal roadway heading face. Initially, the acquired images were preprocessed, i.e., adaptive correction was conducted for non-uniform illumination images based on the 2D gamma function. The edge detection algorithm was then applied to extract the edges of the structural plane, followed by the filtration of the non-structural plane noises. Moreover, the Hough transform algorithm was applied to extract the linear edges; finally, the edges were locally connected in accordance with the angle and distance criteria. The experimental results show that this algorithm can be used to reduce the noise caused by non-uniform illumination and avoid the mutual interference of multi-scale edges, so as to effectively extract the traces of the cross joint. Furthermore, Q-system and rock mass rating (RMR ) , were applied to conduct a quantitative evaluation on the stand-up time of unsupported roof in the four test images. The Q-system quality scores are 26.7, 43.3, 3.1, and 6.7, and the RMR quality scores are 56.84, 58.73, 48.42, and 51.42, respectively. The stand-up time of unsupported roofs with a span of 4.6 m are 30, 36, 7.7 and 14 d, respectively.

Study on dust pollution law and ventilation optimization of roadway excavation and shotcrete simultaneous operation

The simultaneous operation of heading machine and shotcrete machine often occurs in the process of roadway development. Many dust sources, such as cutting dust and shotcrete dust, increase the complexity of roadway dust pollution. In order to find out the law of dust migration in tunneling and shotcrete operation at the same time, and put forward effective dust control optimization measures, this paper takes a mine roadway as an example, based on Fluent numerical simulation software, the dust migration law is analyzed when the roadway driving operation and the shotcrete operation are carried out separately and when the two operations are carried out simultaneously. Moreover, the orthogonal experiment is used to optimize the ventilation parameters of the working face. Results show that the dust concentration in the roadway decreases gradually from high to low when the single shotcrete operation is on the air inlet side. On the return air side, the dust concentration in the roadway increases first and then decreases. In the single tunneling process, the dust concentration on the return air side is significantly higher than that on the inlet side, and at the 52 m section, the dust concentration basically decreases to less than 100 mg/m3. When tunneling and shotcrete work simultaneously, the dust migration distance increases, and the dust concentration decreases to less than 100 mg/m3 at the section of 55 m. Through an orthogonal experiment, the optimal combination of working ventilation parameters is obtained. This study gives a helpful guidance for dust suppression when two or more dust production processes operate simultaneously.