Deformation Characteristics Of Surrounding Rock Research Articles

Study on Deformation Characteristics of Surrounding Rock of Roadway with Coal–Rock Interface

Surrounding rock of roadway with a coal–rock interface is a common form in coal mines. In order to determine deformation characteristics and obtain the control principle of roadways with a coal–rock interface, the interface between the roof and coal seam was added to simulate the weak cohesion between the stratum. In this model, the interface shear stiffness was considered to be one of the key factors affecting horizontal inward movement of the roadway sidewalls. The deformation of the roadway with or without coal–rock interface under different burial depths was analyzed. Then, the shear stiffness of the interface element was changed to study the influence of shear stiffness on roadway deformation. At the same time, the characteristics of discontinuous deformation caused by the coal–rock interface at different positions in the roadway were studied. The results show that the roadway sidewall appeared to bulge in the middle and there is no dislocation and a small deformation in the contact position of the roadway sidewall with the roof and the floor when there is no interface between the stratum of the roadway. When there is an interface, the sidewall of the roadway is extruded as a whole, the slip and dislocation between the coal sidewall and the roof were obvious, and the maximum deformation of the sidewall is 1.68 times that of the roadway without an interface. When the shear stiffness of the interface is low, the deformation and the range of the plastic zone of roadway are large, with a large deformation at the upper part of the roadway sidewall, and a small deformation at the lower part of the roadway sidewall. The deformation of sidewall at the interface position decreases gradually with the increase of the interface shear stiffness, approaching the shape without the interface. When the coal–rock interface is at the sidewall of the roadway, the deformation of the rock and coal body at the interface is discontinuous, with slip and dislocation. The greater the proportion of rock height in the roadway sidewall, the greater the rock deformation. On the contrary, the coal deformation increases. It is more reasonable to simulate the deformation of roadways by adding a coal–rock interface, and the results are closer to the actual situation.

Triaxial creep damage characteristics of sandstone under high crustal stress and its constitutive model for engineering application

AbstractThe creep characteristics of rock under high crustal stress are of important influence on the long‐term stability of deep rock engineering. To study the creep characteristics and engineering application of sandstone under high crustal stress, this study constructed nonlinear creep damage (NCD) constitutive mode based on the triaxial graded loading‒unloading creep test of sandstone in the Yuezhishan Tunnel. A numerical NCD constitutive model and a breakable lining (BL) model were developed based on FLAC3D and then applied to the stability analysis of the Yuezhishan Tunnel. Based on the creep test results of sandstone, a power function of creep rate and stress level was constructed, by which the long‐term strength was solved. The results show that the long‐term strength of the red sandstone based on the related function of the steady‐state creep rate and stress level is close to the measured stress value in engineering. The NCD model considering damage factors reflects the instantaneous and viscoelastic plasticity deformation characteristics of the red sandstone. The numerical NCD constitutive model and the BL model can reflect surrounding rock deformation characteristics and lining failure characteristics in practical engineering. The research results provide theoretical references for long‐term stability analysis of rock engineering and the deformation control of surrounding rock under high crustal stress.

Numerical Simulation Study on Deformation Characteristics of Surrounding Rock during Construction and Operation of Large Underground Gas Storage Structures

Underground gas storage is an important technical measure for future natural gas storage. The stability of the surrounding rock during excavation and under ultra-high gas storage pressure is the key to the stable operation of gas storage reservoirs. A numerical calculation model for different surrounding rock conditions, different depth-span ratios, and different buried depth conditions was conducted to study the stability of surrounding rock after large section underground gas storage excavation and under an ultra-high gas storage pressure of 20 MPa. The results show that after construction is completed, the deformation of the rock surrounding the cavern increases with a decrease in the surrounding rock grade, and the deformation of the rock surrounding the cavern increases as the burial depth increases. In addition, the maximum vertical deformation of the surrounding rock decreases with the increase in the depth-span ratio of the cavern, and the maximum horizontal displacement increases with the increase in the depth-to-span ratio. While operating at 20 MPa gas storage pressure, the displacement of the rock surrounding the chamber tends to increase with the decrease in the surrounding rock grade and the deformation of the surrounding rock of the chamber decreases as the burial depth increases. Furthermore, the vertical displacement of the rock surrounding the chamber decreases with the increase in the depth-span ratio, while the horizontal displacement of the surrounding rock increases with the increase in the depth-span ratio. Considering the stability of the surrounding rock during construction and operation, gas storage chambers should be built in areas with better conditions, such as Grade II and Grade III surrounding rocks within a burial depth range of 200 m. Moreover, the stability of the surrounding rocks is better when the chamber depth-span ratio is 2.5~3.0. These research results can provide a theoretical reference for the design of large underground gas storage structures.

A Case Study on Surrounding Rock Deformation Control Technology of Gob-Side Coal-Rock Roadway in Inclined Coal Seam of a Mine in Guizhou, China

Surrounding rock deformation control of gob-side coal-rock roadway in inclined coal seams (GCRICS) is a major problem in gob-side entry technology application practice. This paper describes a case study of the surrounding rock deformation characteristics and control technology of a typical GCRICS in Guizhou, China. As according to data obtained during a field investigation, the reasons for the deformation and failure of 151509 tailentry and the shortcomings of the original support scheme were analyzed. In combination with existing theory and field experience, the “anchor cable + U-shaped steel + shotcreting + grouting” (CUSG) support method was proposed. The plastic zone distribution, displacement, and stress evolution law of the roadway-surrounding rock under the four support modes were analyzed and compared by numerical simulation. The results show that the supporting effects of several support methods varied from good to poor; CUSG was the best, followed by anchor cable support, U-shaped steel support, and then no support. Based on the previous seepage grouting theory, a slurry diffusion model of hollow grouted anchor cable (HGC) was established and the calculation formulas of slurry diffusion radius and grouting time were deduced, which provided guidance for field construction. Finally, the CUSG surrounding rock control technology was applied to 151509 tailentry subsequent roadway support. Through drill holes, analysis of the surrounding rock of the non-grouting area and the grouting area was conducted. It was found that the surrounding rock of the grouting area was high in integrity and strong in bearing capacity. Throughout the excavation period to the end of roadway mining, the roadway did not have to be repaired. This case study has high practicability, high popularization value, and provides a useful reference for the engineering support design of the GCRICS.

Research on Pressure Relief Method of Close Floor Roadway in Coal Seam Based on Deformation and Failure Characteristics of Surrounding Rock in Deep Roadway

To solve the high-stress hazard faced in the process of deep mining process, the pressure relief characteristics of gas bearing coal and the deformation characteristics of surrounding rock in deep roadway are studied by means of laboratory test, similar simulation analysis, and field investigation. The investigation results and engineering application showed that the specimens could more easily reach the failure point due to the axial pressure relief under high confining pressure. In addition, the deformation and failure degree of the surrounding rock was higher due to the disturbance from the deep high-stress roadway. The scope of the height affected by the pressure relief of the overlying strata reached above 10 m. Moreover, the initial gas emission could reach 4.41–14.39 times that of the original coal seam by drilling a hole in the coal seam at 10 m from the roof. Thus, the short-distance floor roadway exerted an obvious pressure relief effect on the overlying coal seam.

Large Deformation Characteristics of Surrounding Rock and Support Technology of Shallow-Buried Soft Rock Roadway: A Case Study

The coal resources in the coal-rich area of western China are mostly located in the late diagenetic Cretaceous and Jurassic strata. In this paper, a study on the support of soft rock roadways was carried out in the background of the soft rock track roadway in the Jiebangou coal mine. The field investigation showed that the surrounding rocks of the roadway were weak, soft, and broken, and the surrounding rocks were cemented, with the roadway local deformation exceeding 1 m. The borehole television results showed that the surrounding rocks were mainly weak sandy mudstone and yellow mudstone. The average uniaxial compressive strength of the surrounding rock was 15.49 MPa. The roadway is a shallow buried soft rock roadway; site investigation revealed that the original U-shaped steel shed had an extremely low resistance to slip, the filling body behind the U-shaped steel shed fell off, the interaction between the U-shaped steel shed and the surrounding rock was poor, the U-shaped steel shed could not provide sufficient timely support resistance, and the bearing capacity of the U-shaped steel shed was far from consideration. The floor was not effectively supported. The floor had different degrees of the bottom drum, and frequent undercover caused new stress disturbances, which loosened the bottom corners of both rock types and made the shed legs move continuously inward, reducing the bearing capacity and actual support resistance of the bracket. Numerical calculations were performed to study the deformation characteristics of the surrounding rock of the tunnel and the yielding damage characteristics of the brace. The results showed that the current U-shack support strength was insufficient, the two sides were deformed by 950 mm, the bottom of the roadway bulged by 540 mm, and the surrounding rock was mainly shear damaged. The fall of the filler behind the shed caused damage to the U-shaped steel shed spire. Through site investigation results and numerical calculations, the deformation and damage characteristics of the soft rock roadway and its damage causes were analyzed, and the support technology system of ‘strengthening support for weak structural parts’ was proposed. This improved the mechanical properties of the weak structural support body, the stress state of the local surrounding rock, and the bearing capacity of the support structure, and effectively controlled the deformation, damage, and instability of the surrounding rock of the roadway, and deformation, damage, and destabilization of the roadway, thereby achieving overall stability for the surrounding rock of the roadway.

Optimum position of roadway in the middle residual coal seam between the upper and lower longwall gobs

ABSTRACT Residual coal seam mining is regarded as an effective way to alleviate the contradiction between limited coal resource reserves and unlimited consumption demanding. Previous studies have shown that the location of the roadway is one of the key factors affecting the safe mining of the residual coal seams. However, limited research on the roadway layout of the residual coal seam under the multiple mining-induced influence has been conducted, especially on the roadway layout of the middle residual coal seam (MRCS). To determine the optimum position of the roadway, a method to determine the optimum position of the MRCS is proposed based on the three factors of stress, stress variation rate and fracture characteristics. Then, the Jinhuagong Coal Mine is selected as the research mine. The stress distribution, stress variation rate, and fracture distribution of the surrounding rock of the MRCS were systematically analyzed by theoretical calculation, physical and numerical simulations. The research results show that the surrounding rock of the MRCS can be divided into five areas based on the new method, namely ISA, SCA, SRA, HSCRA, and FRA, respectively. Moreover, the roadway position of the MRCS should be avoided in SCA, HSCRA, and FRA areas. Finally, the optimum position of the roadway for the MRCS is determined through comparing the surrounding rock deformation characteristics of the roadway at different locations. The optimum position of the roadway in the MRCS is determined to be 20 m of the internal malposition of the boundary coal pillar. The research results can provide a useful reference for the same types of mines.

Study on support Design of 2220 roadway in Majiliang Coal Mine based on FLAC3D

In view of the serious deformation of roadway 2220 in Majiliang Coal Mine after excavation, the surrounding rock deformation characteristics and stress redistribution of the roadway are studied and analyzed by numerical simulation technology, and the support optimization is carried out. The research results show that the original support scheme can not effectively reduce the roadway deformation and the area of plastic zone and stress concentration area after roadway excavation. After the optimization of the support scheme, the shape variables of the roof and floor and the two sides are obviously reduced, and the plastic zone and stress concentration area are also greatly reduced, which significantly improves the overall stability of the roadway.

Numerical simulation research on the gob-side coal pillar width and surrounding rock deformation characteristics

Taking the Gaohe Coal Mine working face gob-side in Shanxi as the research object, the FLAC3D numerical simulation software was used to construct a numerical calculation model to analyze the coal pillar width and the surrounding rock deformation characteristics of the working face gob-side in the mining face during the mining process. The width of the coal pillars along the gob-side was determined, and the change law of the surrounding rock stress and deformation of the roadway with the advancing face was obtained. The research shows that the reasonable coal pillar width along the gob-side in the working face of Gaohe coal mine shall not be less than 36m. With the advancement of the working face, the stress and deformation of the surrounding rock of the roadway gradually increase, and the deformation amount and deformation range of the coal gang are both greater than the corresponding value of the flexible form gang, and the vertical stress of the coal gang is less than the stress of the flexible form concrete gang. The difference in deformation is the main reason for the difference in stress. The results of the study provide a reference for the safety of the gob-side along the coal mine.

Stability analysis of surrounding rock-supporting system of shallow buried soft rock tunnel based on time effect

In view of the lack of consideration of the time effect parameters of surrounding rock and supporting structure in the past research, this paper aims at the surrounding rock deformation characteristics of highway soft rock tunnel, and by introducing the long-term strength of rock and the creep coefficient of sprayed concrete, the surrounding rock and concrete mechanical parameters considering time effect is obtained. This paper uses ANSYS software to establish the finite element model, according to the application of anchors, steel arches and shotcrete support after the excavation without any support and excavation. The simulation results of surrounding rock-support stability after tunnel excavation are obtained. The effects of surrounding rock mechanical parameters and supporting parameters on tunnel deformation and surrounding rock stability under different time effects are studied. The research results can provide useful theoretical suggestions for the safe construction of subsequent soft rock tunnels.

Discussion on stability analysis and support technology of surrounding rock of gob-side entry retaining

In order to further analyze the stability and control mechanism of surrounding rock in the gob-side entry retaining, the slip instability coefficient k1 and compression failure coefficient k2 are proposed by the mechanical analysis of the established filling body mechanics model, and when both k1 and k2 are less than 1, the roadside filling body can keep stable. The mechanical model of main roof is analyzed by the static equilibrium method, and the formula for calculating the maximum roof subsidence is deduced. Based on the data of haulage gateway of No. 21201 coal face of Juncheng Coal Mine, using the formula to calculate the amount of roof subsidence at the junction point of filling body and the roof, and proposes two methods to reduce roadway floor heave by increasing the roadside filling width and transferring the surrounding rock stress to the gob. Finally, the corresponding surrounding rock control technology is proposed according to the surrounding rock deformation characteristics during roadway excavation, roadway retention and roadway reuse, and then carries out field monitoring and evaluation. The results show that after adopting the corresponding supporting technology, the surrounding rock of the gob-side entry retaining has been effectively controlled from the excavation to the reuse period with the coal face advancing, the roof-to-floor convergence of roadway solid coal side is less than 220 mm, the roof-to-floor convergence of filling body side is less than 280 mm, and the convergence on the both sides of the roadway is about 190 mm. At the same time, the calculated roof subsidence with the junction point of filling body and the roof is similar to the field monitoring results, which achieves the expected control effect, and the research contents provides a certain reference for the support technology of the gob-side entry retaining.

Analysis of Deformation Characteristics of Surrounding Rock in Shallow Excavation Tunnel

This paper takes the section of the excavation section SK25+490 of Nanzhi Road Station of Harbin Metro Line 2 as the background. Through collecting field monitoring data, the diachronic variation curves of surface subsidence and vault subsidence are drawn. By using FLAC3D software, a 3d model is built based on the engineering profile of the tunnel. Through comprehensive comparison of numerical analysis results and field monitoring data, it is found that the deformation of tunnel surrounding rock can be divided into three stages: rapid deformation, slow growth and basic stability with the advance of palm face. The similarity between the field monitoring data and the numerical analysis of the surrounding rock deformation law is high, which is of guiding significance for the reasonable selection of construction methods and types of supporting lining.

Surrounding rock control of gob-side entry driving with narrow coal pillar and roadway side sealing technology in Yangliu Coal Mine

Gob-side entry driving can increase coal recovery ratio, and it is implied in many coal mines. Based on geological condition of 10416 working face tailentry in Yangliu Coal Mine, the surrounding rock deformation characteristics of gob-side entry driving with narrow coal pillar is analysed, reasonable size of coal pillar and reasonable roadway excavation time after mining are achieved. Surrounding rock control technology and effective roadway side sealing technology are proposed and are taken into field practice. The results showed that a safer and more efficient mining of working face can be achieved. In addition, results of this paper also have important theoretical significance and valuable reference for surrounding rock control technology of gob-side entry driving with narrow coal pillar under special geological condition.

Roadway layout for recycling residual coal pillar in room-and-pillar mining of thick coal seam

In the context of a room-and-pillar mining gob in Shanxi province in China, this paper numerically investigates the stress distribution and deformation rules of roadway surrounding rocks at various locations of residual coal pillars in room-and-pillar mining gobs using software FLAC3D. It is found that the concentrated stress beneath coal pillars distributes in a shape of ellipse. A reasonable roadway layout is then proposed. In this design, it is indicated that roadways should be designed to avoid the supporting zones of pillars with increasing compression and take into account the roof falling and crushing in the upper gob. According to the surrounding rock deformation characteristics and mining roadway locations as well as the supporting principles of timely support, rock reinforcing, piecewise management and suiting local conditions, a new asymmetric shield supporting plan is proposed. The field surveying results show that this supporting plan can effectively control the roadway rock deformation, thus guarantee the safe and smooth construction of roadways.

The Numerical Simulation and Supporting Design of Gob-Side Entry Retaining in Gradient Medium Thick Coal Seam

In order to solve the technical problem of gob-side entry retaining in inclined coal seam, combined with the practical mining conditions in a certain mine, this paper adopts the discrete element method, applies numerical simulation to analyze inclined coal seam gob-side entry retaining with three different supporting ways, and studies surrounding rock deformation characteristics of gob-side entry retaining. The research results show that the filling body upper boundary for right side can control the roadway surrounding rock deformation better compared with the boundary is used as the hypotenuse; Meanwhile, the pressure of surrounding rock of coal seam gob-side entry retaining is mainly from the impact of the immediate roof natural fall of the upper goaf tilt and the weight of caving coal gangue and coal seam of immediate roof above; According to the surrounding rock deformation characteristics of coal seam remain gateway along goaf, it is determined to use combined supporting method of concrete filling in roadway sides and anchor wire rope supporting inside the roadways, providing the design basis of gob-side entry retaining in coal seam for the similar geological conditions.

Tunnel Surrounding Rock Deformation Characteristics and Control in Deep Coal Mining

In order to study the failure characteristics and control method of deep tunnel surrounding rock, based on the stress test, the structure and stress state of the main transportation tunnel surrounding rock in Mine Zhaogezhuang level 14 was analyzed, and it shows that the surrounding rock is exposed to an interphase hard and soft disadvantageous structure state and complex high stress repeated addition area; Through the theoretical analysis and the statistical data, the relation between the tunnel stress transformation and the surrounding rock deformation was proposed; Through the numerical simulation of the tunnel surrounding rock failure process with the help of RFPA procedure, the results show that the damage of the transportation tunnel level 14 mainly occurs in the bottom and the two coal ribs, and the failure process is spreading from the bottom to the two coal ribs, and the effect of the surrounding rock deformation control is obvious by using the way of 2.5 m anchor with 1.0 m grouting strengthening.

Study on Surrounding Rock Deformation Characteristics and Control Technology in Deep Soft Rock Roadway

To explore support technical problems in deep soft rock roadway, according to deep complicated geological conditions in 102 transport rise of Yuandian Mine, obtaining deformation characteristics of roadway in the initial support scheme under conditions, analysing the reasons of instability and failure of surrounding rock, proposing the surrounding rock control technology of step-by-step strengthen co-supporting, determining secondary anchor cable strengthen support time and grouting delay distance, optimizing the parameters of roadway support. Industrial practice show that the control effect of deformation was obvious,which provide the reference for deep soft rock tunnel support decision.