Surrounding Rock Control Research Articles

Determination of Narrow Coal Pillar Width and Roadway Surrounding Rock Support Technology in Gob Driving Roadway

In order to determine the rational width of coal pillars and study the surrounding rock control technology of gob side entry driving with a narrow coal pillar, this paper first calculates the width of narrow coal pillar according to limit equilibrium theory; after that, the lateral support pressure and plastic zone development of the goaf is analyzed by numerical simulation to determine the rational width of reserved coal pillar; finally, through the ring breaking deformation regulation of surrounding rock of the gob side entry, the deformation and failure characteristics of the gob-side roadway during excavation and the influence of mining on the deformation and failure of the gob-side roadway are analyzed. The research results show that, combined with theoretical analysis and numerical simulation, the width of narrow coal pillar is decided to be 10 m; the deformation of the coal pillar side of the gob side roadway is much bigger than the roof subsidence, the deformation of the solid coal wall and the floor deformation; after the bolt support design of the gob side roadway, the deformation and damage of the gob side roadway during the driving period is small; during mining, the deformation of the narrow coal pillar wall is the key factor to determine the stability of the gob roadway; under the bolt support scheme, the overall deformation and failure of surrounding rock of the goaf roadway is small, and the control effect of the surrounding rock of the goaf roadway is good.

Study on Surrounding Rock Control of Gob-Side Entry Retaining in Inclined and Thick Longwall Face

Study on Surrounding Rock Control of Gob-Side Entry Retaining in Inclined and Thick Longwall Face

Research of roadway deformation induced by mining disturbances and the use of subsection control technology

AbstractTo address the problem of instability and failure of the 11,514 return air roadway caused by dynamic pressure in Jinhuagong Coal Mine, this study uses theoretical analysis, numerical simulation, and field test methods. The disturbance deformation mechanism and the surrounding rock control technology for the 11,514 return air roadway during face‐to‐face mining and excavation are analyzed. The results show that the causes of regional asymmetric deformation and failure of the surrounding rock of the 11,514 return air roadway are multiple superpositions of lateral bearing pressure of the 11,812 mined‐out area, mining stress in the 8814 working face, and advanced stress of the 11,514 return air roadway. When mining and excavation faces meet, the 11,514 return air roadway is affected by the superimposition of the mining stress. At the same time, the solid coal side of the roadway is in the mining pressure relief area in the 8814 working face in the upper coal seam, and the asymmetric distribution of the principal stress on both sides of the 11,514 return air roadway causes deformation and failure of the surrounding rock. Based on the differences in superimposed stress disturbance in different parts of the roadway, a subsection control technology is proposed. This technology is focused on supporting secondary reinforcement in the range of 40 m before and after the mining overlap position on the 11,514 roadway. Field measurement data confirm the effectiveness of this support technology.

Characteristics of Stress Field and Damage Law of Coal Rock in Residual Pillar of Top Slice and Its Application

This article presents a theoretical analysis and numerical simulation studies to determine the suitable position for the lower slice roadway in a residual pillar area after top slicing a thick coal seam. We considered the load concentration on the coal pillar, the goaf floor, and the stress distribution characteristics of the coal pillar area before and after the top slice. With a mechanical model built of the residual pillar load propagation in the floor and the failure model of the floor surrounding rock, the analytical formula we deduced for the coal pillar floor stress and the expression of the floor failure depth of the roadway provides a basis for the reasonable determination of the position of the lower slicing roadway. Studies proved that after mining the top slice working face, the floor stress field of the residual pillar area presented characteristics of the non-uniform distribution. The stress concentration occurred below the coal pillar. The stress variation area appeared at the edge of the coal pillar, with a stable stress area appearing far away from the coal pillar area. Therefore, the roadway layout should avoid the areas below the coal pillar and the coal pillar edge with high stress levels and a large stress variation gradient. High stress concentration formed on the coal pillar transferred to the lower layered coal and floor strata, and decreased the stress concentrations layer by layer. However, mining of the top-layered working face affected the coal, and rock mass damaged the coal pillar floor area and weakened the mechanical properties, which was not conducive to the control of the roadway surrounding rock. The research results applied to No. 30117 working face of the lower slice of the Shancheng Coal Industry, and the proper position of the return airway of the working face was determined to be 8 m outside the east side of the residual pillar in the top slice, achieving a good surrounding rock control effect.

Research on the Technology of Small Coal Pillars of Gob-Side Entry Retained in Deep Mines Based on the Roof Cutting for Pressure Unloading in the Lower Key Stratum

With the mining depth getting deeper and deeper, surrounding rock control technology has become a difficult issue in the development of modern mining, especially the mining roadways affected by mining. It is very difficult to control the surrounding rock due to the intense mining of the last working faces. In order to alleviate the impact of dynamic pressure on the gob-side entry retained, solve the ventilation difficulties caused by the commonly used method of the gob-side entry retained without leaving coal pillars, and solve the disadvantages of the inability to effectively isolate water and harmful gases, this paper proposes a small coal pillar gob-side entry retained technology based on the key stratum, that is, cutting the key stratum above the top plate, transferring lateral support pressure from the workings further up the seam to the depths of the coal seam, and then protecting gob-side entry retained method. In the final method of precracking and cutting joints by blasting with D-type polytunnel, we directionally cut the lower key stratum above the roadway in the designed direction and position. The theoretical analysis, numerical simulation and field test, and the method of the blasting broken roof pressure release effect are analyzed. Compared to the unloaded pressure method, the relatively complete direct roof is conducive to the maintenance of the surrounding rock on the gob-side entry retained. At the same time, the pressure relief caused by the fracture of the lower key stratum of the coal roof significantly improves the stress environment. The stress is no longer concentrated on the small coal pillars and the gob-side entry retained, and the required roadway support strength is greatly reduced and no longer needs to carry out the construction of roadside support system. This technology reduces labor intensity and production costs.

Mechanical Properties and Anchorage Angle Optimization of Rock Mass with a Weak Intercalated Layer

A weak intercalated layer has gradually become the key problem in roadway surrounding rock control in deep rock stress environment, and the selection of anchorage angle has a great influence on the stability of the intercalated rock. This study aimed to prepare weak intercalated layer-composited specimens with different dip angles and anchorage angles for the uniaxial compression test. The results showed that the strength curve of the composite specimens exhibited a single-peak variation trend of first decreasing and then increasing from 0° to 90° inclination variation, and the strength and strain reached the lowest value at 60° inclination angle. The failure modes of composite specimens with different dip angles could be divided into single splitting failure, coupled shear failure, and single shear failure. The initial strength of the unanchored specimen was basically the same as that of the anchored specimen, and with the increase in anchorage angle, the uniaxial strength first increased and then decreased. The appropriate anchorage angle range was 0° to 30°. Mainly slip deformation of the specimen occurred when the anchorage angle was smaller than 30°, and the deformation of the specimen mainly depended on the material of the bolt when the anchorage angle was larger than 30°. The strength variation model of the composite anchorage specimen was proposed, taking into account the stress of the bolt, the influence of the dip angle of the intercalated layer, and the anchorage angle of the structural plane.

Support design of main retracement passage in fully mechanised coal mining face based on numerical simulation

Abstract For the comprehensive mechanised coal mining technology, the support design of the main withdrawal passage in the working face is an important link to achieve high yield and efficiency. Due to the impact of mining, the roof movement of the withdrawal passage is obvious, the displacement of the coal body will increase significantly, and it is easy to cause roof caving and serious lamination problems, and even lead to collapse accidents, which will affect the normal production of the mine. In this paper, the mining pressure development law of the main withdrawal passage support under the influence of dynamic pressure is designed, the most favourable roof failure form of the withdrawal passage is determined, and the action mechanism and applicable conditions of different mining pressure control measures are studied. The pressure appearance and stress distribution in the final mining stage of fully mechanised coal face are studied by numerical simulation. The deformation and failure characteristics and control measures of roof overburden in the last mining stage of fully mechanised coal face are analysed theoretically. Due to the fact that periodic pressure should be avoided as far as possible after the full-mechanised mining face is connected with the retracement passage, some auxiliary measures such as mining height control and forced roof blasting are put forward on this basis. The relative parameters of the main supporting forms are calculated. The main retracement of a fully mechanised working face in a coal mine channel is put forward to spread the surrounding rock grouting reinforcement, reinforcing roof, and help support and improve the bolt anchoring force, the main design retracement retracement channels in the channel near the return air along the trough for supporting reinforcing surrounding rock control optimisation measures, such as through the numerical simulation analysis, the optimisation measures for coal mine fully mechanised working face of surrounding rock is feasible. Numerical simulation results also show that the surrounding rock control of fully mechanised working face of coal mine design improvements, its main retreat channel under the roof subsidence, cribbing shrank significantly lower, and closer, to better control the deformation of surrounding rock, achieved significant effect, to ensure the safety of coal mine main retracement channel of fully mechanised working face support.

Investigation on Hydraulic Fracturing and Cutting Roof Pressure Relief Technology for Underground Mines: A Case Study

Abstract Using hydraulic fracturing for cutting roof pressure is a critical technology to protect coal pillars. In this paper, based on the engineering background of 18506 working face in the Xiqu Coal Mine, using the methods of theoretical analysis, numerical simulation, and field measurement, a reasonable coal pillar width and practical parameters of hydraulic fracturing are given. The results show that roof cutting can significantly increase the stress in goaf and relieve the advanced pressure of the working face. Taking 18506 working face as the research object, the industrial test is carried out, and the surrounding rock control scheme of hydraulic fracturing and roof cutting is put forward, the mine pressure monitoring results show that the auxiliary roadway of 18506 working face reaches a stable state within 20 days, the deformation and damage degree of roadway surrounding rock are small, and the integrity of surrounding rock is improved.

Research on Surrounding Rock Control Technology of Gob-Side Entry Retaining by Directional Roof Cutting in a Deep Coal Mine

Research on Surrounding Rock Control Technology of Gob-Side Entry Retaining by Directional Roof Cutting in a Deep Coal Mine

Research on Mechanisms and Control Measures of Surrounding Rock Disaster in Large Section Roadway with Top Coal under the Influence of Tectonic Stress

Based on the research background of large section roadway with top coal (LSRTC) in thick coal seam mining in Wangzhuang Coal Mine, Shanxi Province, China, catastrophe characteristics of the surrounding rock of the LSRTC were investigated and summarized. Based on the principle of damage mechanics, the critical size discriminant of the LSRTC was deduced, and the induction mechanism of section size effect and tectonic stress effect on the roadway surrounding rock disaster was revealed. Accordingly, the roadway surrounding rock control principle with the basic idea of “stabilizing and controlling top coal, reconstructing the coal wall, and limiting floor heave” was put forward, and the roadway surrounding rock stability control countermeasures with the core technology of “strong pressure support for roof + grouting reinforcement for two sides + bolt barrier for floor angle” were developed, which solved the surrounding rock control problem of the LSRTC under the action of tectonic stress and provided a useful reference for the difficult problem of roadway surrounding rock control under similar conditions.

Failure characteristics and stability control technology of dynamic pressure roadway affected by the mining activity: A case study

Dynamic pressure roadway affected by the mining activity (DPRAMA), which is aimed at promoting the efficiency of panel replacement, is a new mode of roadway arrangement in neighboring panels. However, the failure characteristics and stability control of DPRAMA surrounding rock are rarely reported. In this study, the fragment grade of two-side coal mass of DPRAMA in Gaojiapu Coal Mine was evaluated using the basic measurement scale-fragment grade evaluation method. Then, the evolution of rock mass failure was analyzed through Flac3D software. The results show that (1) under static loading, DPRAMA is highly stable. (2) Under the second dynamic loading, the stress concentration coefficient and deformation value of surrounding rock both surges. (3) Under dynamic-static loadings, the roof falling value is far larger than the floor heave value, and the deformation of pillar-side coal mass is more serious than that of panel-side coal mass. Surrounding rock deformation is divided into three phases, and the specific support strategy is selected in accordance with the characteristics of each stage. (4) The plastic region shows a tendency of butterfly-shaped failure. Based on these findings, the surrounding rock control strategy of “slow yield and long-short control” was proposed to alleviate roof and pillar-side coal mass deformation. Furthermore, the coupling support scheme of “high-strength yield bolt (cable) & steel band” was designed for DPRAMA.

Study on the Working Resistance of a Support under Shallowly Buried Gobs According to the Roof Structure during Periodic Weighting

The phenomenon of dynamic pressure in the panel under shallowly buried gobs is obvious, resulting in limited and challenging support type selection. In this paper, theoretical analysis, numerical simulation and field measurement were combined to study the reasonable working resistance of the support in panels under shallowly buried gobs. First, the definition of the equivalent main key stratum (EMKS) was proposed. Then, a method of identifying the structure of the EMKS and broken key stratum blocks was given. The roof structure of the panel under a shallowly buried gob (PSBG) during strong periodic weighting could be divided into 12 types. Mechanical models of the roof structure were established, and the method to calculate the working resistance of the support was given. The Bulianta coal mine and Fengjiata coal mine in the Yushenfu Mining Area were taken as research objects. Based on the measured working resistance curve of the support, the structural morphology of key stratum blocks during strong periodic weighting was distinguished. On this basis, the working resistance of the support was calculated. Finally, FLAC2D numerical software was used to test the working resistance of the support. Based on the subsidence of the roof, horizontal displacement of the coal wall and the development range of the plastic zone in the surrounding rock, the working resistance of the support and adaptability of the surrounding rock control were verified and evaluated. The results show that it is reasonable to calculate the working resistance of the support based on the roof structure during strong periodic weighting. The research results can provide a reference for the scientific and rational selection of the support in a PSBG.

Study on the Stability Principle of Mechanical Structure of Roadway with Composite Roof

With the typical composite roof roadway and roof fall accidents in the Guizhou Province of China as the research background, the expression of damage parameters of composite roof was deduced according to Weibull statistical distribution, generalized Hooke’s law and Mises yield criterion, and the influence of shape and scale parameters of Weibull on damage characteristic was discussed. Based on the infinite slab theory, the expressions of deflection and layer separation of each layer of the composite roof were obtained, the critical load expression of each delamination was determined, and the influence of roadway width, overlying strata load, elastic modulus, shape parameters and scale parameters on the stability of composite roof was explored. The research shows that the bolt support can effectively reduce the layer separation between the composite roofs and enhance the stability of the composite roof. On this basis, it is proposed that for the surrounding rock control problem of roadways with composite roof, the active support technology with bolts as the core should be adopted.

Case Study on the Stability Control of Broken Surrounding Rock in Roadway Excavation on the Edge of a Collapsed Stope Area

Predicting and controlling the collapse of surrounding rock (especially broken rock masses) in underground chambers is an important topic in mining and geotechnical engineering. Based on an example, this paper introduces a case study of surrounding rock stability control technology in stope mining around abandoned areas. Based on on-site coring, mechanical properties of rock samples, and on-site grouting reinforcement technology, the TRT6000 advanced geological prediction system was used to predict the stability status of the surrounding rock of the underground chamber. AUTODYNA software was used to build a dynamic coupling model for numerical simulation prediction and optimization of blasting parameters and to reveal the dynamic variation in the surrounding rock. The dynamic failure process of the surrounding rock of the chamber before and after optimization of the blasting parameters is simulated, and the deformation characteristics and damage and acoustic emission characteristics of the surrounding rock are clearly shown. The surrounding rock failure first appeared around the surface of the underground chamber because of the high stress concentration around the surface of the chamber after blasting; with the interaction between the explosive gas and the rock mass, the damaged area further propagated into the external rock, eventually leading to a large damage area. At the same time, there is a large tensile failure in the rock, resulting in expansion and rupture around the underground chamber. Finally, the 3D laser scanning method is used to verify the superiority of the optimized blasting initiation sequence. The new edge hole detonation sequence can effectively improve the blasting vibration and successfully control the further damage of the surrounding rock of the underground chamber, thus proving the edge hole drug pack. Moreover, the initiation mode of the delay stage of the side hole charge is determined. This study provides a useful reference for the stability control of surrounding rock in mining in mining areas.

Investigation on the mechanism and control methods for roof collapse caused by cable bolt shear rupture

Roof collapse of mining roadways has always been key in the studies of the surrounding rock control. One of the critical factors lies in the roof separation and horizontal displacement which led to the cable bolt shear rupture, resulting in the roof fall. This study investigates the roof collapse accident that occurred at the No.15028 tailgate of XinJing coal mine in China. In-situ observations, numerical simulation and laboratory test are conducted to analyse the gradual deterioration of the roof strata. The field observation of the fractures, separations, pretension load and rock bolts loading are conducted during the process of separation. The analysis results indicate that owing to the torque value of rock bolts below 150 N·m (pretension load was 29 kN) and incompatibility of reinforcement fittings of rock bolts, the pretension load failed to solidify the surrounding rocks effectively. Obvious separations were identified at rock depths ranging from 0 to 2.6 m. Simulation results revealed that different flexural deflections caused horizontal displacement in rocks, which is positively correlated with the vertical separation. In weak interlayers of rocks, the severe horizontal displacements led to shear fracture of cable bolts, resulting in roof collapse. An increasing rock bolt pretension load can reduce the horizontal displacement of the rock stratum beyond the anchorage zone, which can lower the shear force of cable bolts by 30% and reduce the shear fracture risk of the cable bolts. Mechanical compatibility tests of the surrounding rock support system are conducted to develop a practical and reasonable reinforcement fittings to increase the pretension load of the rock bolts. Based on the research, a series of control methods are developed to enhance the roof stability. The field tests proved that the newly proposed methods can effectively improve the stability of the roof and eliminate roof collapses.

Deformation Mechanism and Surrounding Rock Control in High-Stress Soft Rock Roadway: A Case Study

Stability control for soft and broken surrounding rock of roadways is one important segment of mining support. Taking 1412 Roadway of a mine in Guizhou province as a research background, this paper studies the large deformation of surrounding rock and the failure of bolts and cables. The deformation and failure mechanism are analyzed by related theoretical analysis and field survey. Then, the feasibility of the composite controlling scheme, bolts and cables + grouting + steel tube concrete support, is verified by theoretical analysis, numerical simulation, and industrial test. Following results can be obtained: main reasons leading to the deformation of surrounding rock and the failure of cables and blots in the roadway are low strength and poor self-stability of surrounding rock, complex stress environment, low support resistance, and lack of reinforced support in crucial supporting sites; the control scheme can reduce the surrounding rock deformation by 40%, which meets the requirements of field application so that this practice can provide some guidance for other similar projects.

Surrounding Rock Stability Control Technology of Roadway in Large Inclination Seam with Weak Structural Plane in Roof

The surrounding rock control technology of mining roadways in large inclination seams with a weak structural plane in the roof is one of the most challenging fields in underground roadway support. In view of the serious deformation of the surrounding rock of the transportation roadway in the 1201 working face of a mine, the deformation and failure characteristics and instability mechanism of the surrounding rock of the roadway are analysed. The self-stability mechanical model of the roof block structure of the roadway with a large inclination under the support effect is established, and the support concept of “high pre-stressed asymmetric” and the combined support method of bolts, wire mesh, and cables are proposed. The rationality of the supporting scheme is verified by numerical simulation. The results show that: compared with bolt and wire mesh support, the maximum shear displacement of the roof’s weak layer under the combined support of bolt, wire meshes, and cable before and after mining is reduced by 86.78% and 83%, respectively, and the maximum total displacement of surrounding rock surface is reduced by 49.22% and 37.1%, respectively. The field monitoring results show that the combined support scheme can effectively control the deformation of the surrounding rock.

Failure Mechanism and Control of Surrounding Rock of Mining Roadway Under Overlying Goaf

Failure Mechanism and Control of Surrounding Rock of Mining Roadway Under Overlying Goaf

Research on Stress Distribution Characteristics for Uniquely Shaped Roadway with Hard Roof in Steeply Inclined Coal Seam and Support Technology of Reducing Vibration Impact

This paper presents a comprehensive study of the stress distribution and stability analysis of a uniquely shaped roadway having a steeply dipping hard roof. The coal seam and its roof have a certain impact tendency, which is the internal condition of rock burst. The syncline tectonic stress causes the original rock stress to reach a higher level. The large amount of coal produced in the coal mine and the large movement range of the upper strata cause the huge mining additional stress around the stope. The impact load caused by “cantilever beam” fracture of hard roof can induce and strengthen rock burst. Its engineering geological setting encompasses the mining process and surrounding rock conditions of No. 6 Coal Seam in the 2130 coal mine of Xinjiang. Numerical simulations with theoretical analysis and field measurements investigated a proposed new truss combined support scheme for implementation. A comparison was made of the differences in the state parameters of the road under the new and old support conditions. The application of the new combined support technology changed the form of the stress distribution around the road. Apart from the displacements of the two coal sidewalls, the new support system notably reduced the displacement of roof and floor by 67.8% and 83.6%, respectively. After the implementation of the new support scheme, the frequency of the original rock burst in the working face is greatly reduced, the surrounding rock control and field application effects also remained good, and personnel and equipment safety and production plan have a good guarantee.

Research on the Surrounding Rock Control Technology of Gob-Side Entry with a Narrow Coal Pillar Reserved in a Fully Mechanized Caving Face with Large Mining Height

Research on the Surrounding Rock Control Technology of Gob-Side Entry with a Narrow Coal Pillar Reserved in a Fully Mechanized Caving Face with Large Mining Height