Surrounding Rock Research Articles

Elastoplastic Analytical Solution for the Stress and Deformation of the Surrounding Rock in Cold Region Tunnels Considering the Influence of the Temperature Field

Elastoplastic Analytical Solution for the Stress and Deformation of the Surrounding Rock in Cold Region Tunnels Considering the Influence of the Temperature Field

Research on the Stability Mechanism of the Surrounding Rock of Gob-Side Entry Retaining by Roof Cutting in Dianping Coal Mine

According to the movement characteristics of the surrounding rock of the gob-side entry retaining by roof cutting (GERRC), the structural evolution mechanism and stability control countermeasures are studied in this paper. Taking the roof cutting and bulking as the core point, the movement process of the surrounding rock of GERRC is divided into five stages: roof cutting, dynamic pressure support, gangue bulking, double arch roadway support, and roadway formation. Combined with mechanical analysis, the roof pressure of the mechanical model of the short-arm beam formed by roof cutting is calculated, and the roof breaking criterion is obtained, which provides a basis for roof control design and reasonable support strength calculation. A structural model of double-arch roadway protection under the action of hydrostatic roof cutting and gangue bulking was established, and the mechanism of roadway formation stability was studied. The gob-side bulking gangue and short-arm beam are formed by roof cutting, and the solid coal seam forms the immediate balance arch, the bulking gangue in goaf, articulated transfer rock beam, and solid coal seam forms the main balance arch. The two together are called double balance arch. With the support of the double-balanced arch on the overlying rock strata, the roadway below is located in the low-stress zone, which ensures the stability of the roadway surrounding rock. Through mechanical analysis and field observation, the law of bulking and deformation and mechanical characteristics of gob-side gangue in the above structural model are analyzed, and the reasonableness of the structural model of the double-arch guard lane is verified through numerical simulation of the cut top into lanes. and the reasonableness of the structural model of double-arch protection in GERRC is verified by using numerical simulation. In this paper, a mechanical double-arch model has been developed that allows us to understand the mechanism of stress transfer of roof cutting roadway from the perspective of a dynamic balance of roadway surrounding rock and overlying rock strata, helping us to specify efficient support countermeasures.

Analysis of Surrounding Rock Pressure of Deep Buried Tunnel considering the Influence of Seepage

This paper takes the surrounding rock of deep tunnel as the research object and considers the action mechanism under the influence of seepage. Based on the Mohr-Coulomb criterion, the stress mechanism of surrounding rock of deep buried tunnel is analyzed by a convergence constraint method. Based on the elastic-plastic solution, the nonlinear elastic-plastic solution of the interaction between surrounding rock and lining structure considering the effect of seepage force is proposed, and the radius of surrounding rock plastic zone is obtained. The relationship between surrounding rock stress and displacement, radial deformation of lining, and support reaction force was observed. At the same time, considering the effects of seepage, strain softening, and intermediate principal stress, the surrounding rock is divided into a plastic residual zone, plastic softening zone, and elastic zone, and the stress distribution expressions of the plastic zone and each zone of surrounding rock of circular tunnel are derived. The results show that with the change of nonuniform permeability coefficient, the seepage shows anisotropy in different directions, and the closer to the horizontal or vertical direction, the more obvious the influence of nonuniform permeability coefficient on pore water pressure distribution. Seepage and material softening have different effects on the distribution of surrounding rock stress field and the size of plastic zone. Material softening is more unfavorable to the stability of surrounding rock than seepage. The intermediate principal stress coefficient has a significant impact on the tangential stress and plastic zone of surrounding rock. When the intermediate principal stress effect is not considered, the calculation results are relatively conservative and cannot give full play to the strength of surrounding rock effectively. The research conclusion can provide a theoretical reference for studying the stability of surrounding rock in tunnel excavation under water-bearing rock.

Theoretical Study of Surrounding Rock Loose Zone Scope Based on Stress Transfer and Work–Energy Relationship Theory

In view of the actual gap between the theoretical solution and the measured value of the range of the surrounding rock loose zone excavated by blasting, the formation process and influencing factors of the surrounding rock loose zone after blasting are analyzed by combining theoretical analysis, numerical simulation, and field tests. It is proposed that the formation of the surrounding rock loose zone can be divided into two parts: the stress loose zone formed by in situ stress release after chamber excavation and the blasting–expansion loose zone formed by blasting, corresponding to the stress loose zone crack propagation. In this paper, the stress method and work–energy relationship method based on the Fenner solution were used to study the range of the surrounding rock loose zone formed after chamber excavation. A theoretical formula for determining the range of the surrounding rock loose zone is presented. These methods can clearly explain the formation mechanism of the loose zone, and the parameter selection method is simple and fast, which can be used for the theoretical prediction of the loose zone of surrounding rock in tunnel engineering in rock areas. Finally, the two methods were used to calculate the range of surrounding rock loose zone under three different working conditions in the Qingdao Metro single-track section, and the results were compared with the field monitoring results to verify the applicability of the proposed methods.

Study on Failure Mechanism and Control Technology of Roadway Surrounding Rock under Complex Occurrence Coal Seam

Aiming at the characteristics of large deformation and long deformation time under the mining influence of the 2254 east floor roadway surrounding rock, which under the condition of complex coal occurrence in Jiahe Mine. Through the actual measurement, it is found that the mineral composition of the roadway surrounding rock is mainly siderite, and it also contains 9.52% of kaolinite minerals, and the surrounding rock is relatively weak. Through drilling and peeping, it is found that the roadway surrounding rock is mainly thin-layered, and a large number of fissures are developed in the surrounding rock near the surface of the roadway. Through the in situ stress test, it is concluded that the in situ stress field of Jiahe Mine is dominated by horizontal stress, the minimum principal stress is vertical principal stress, and the lateral pressure coefficient exceeds 2, causing serious damage to the two sides of the roadway. Using the gas drainage drilling data of the 2254 east floor roadway and using SketchUp and Rhino software, the complex geological occurrence model of the coal seam above the roadway was constructed, and on this basis, the FLAC3D numerical calculation model was constructed. The analysis results show that the plastic zone of the roadway surrounding rock is large, the bolt anchoring section is within the plastic zone, and the control effect on the deformation of the roadway surrounding rock is poor. Therefore, a comprehensive support method of “reserved deformation, anchor rod, metal mesh, shotcrete, grouting anchor cable, and full-section grouting” is proposed. The monitoring results of the surrounding rock deformation of the roadway 12 months after construction show that the support scheme can effectively control the deformation of the roadway surrounding rock. The research results provide a reference for the stability control of similar roadways.

Stability Analysis of Surrounding Rock of Shallow-buried Subway Tunnel with Small Spacing under Different Working Conditions

Stability Analysis of Surrounding Rock of Shallow-buried Subway Tunnel with Small Spacing under Different Working Conditions

Instability Mode and Control Technology of Surrounding Rock in Composite Roof Coal Roadway under Multiple Dynamic Pressure Disturbances

In view of the problems of composite roof coal roadway under multiple dynamic pressure disturbances such as strong stratification, large deformation of the roadway surrounding rock, and poor safety and reliability, this paper analyzed the deformation and instability characteristics of composite roof coal roadway under different influencing factors using numerical simulation and expounded the stress distribution pattern of composite roof coal roadway under multiple dynamic pressure disturbances. The geological conditions of gas control roadway in the 22301 working face of Tunlan coal mine are taken as examples, and this study is carried out based on the analysis of roof instability conditions of composite roof coal roadway. The progressive crack development characteristics in composite roof coal roadway and the instability failure mode of surrounding rock under multiple dynamic pressure disturbances were revealed, and the control mechanism and support scheme were put forward. According to the result, it is difficult to form a stable bearing rock beam due to the occurrence characteristics of the weak interlayer of the composite roof. The deflection of the roadway roof and the extent of the plastic zone are negatively correlated with the distance from the soft rock layer to the roadway but positively correlated with the thickness of the soft rock layer. As the lateral pressure coefficient λ increases, the plastic zone of the roadway surrounding rock first decreases and then increases. With the increasing influence of dynamic pressure, the coal roadway with composite roof suffers from greater damage under the superposition of high ground stress, lateral abutment pressure, and advance abutment pressure, which is characterized by significant zonal failure of the roof and asymmetric failure of surrounding rock. The control method of high-strength thick anchorage + differential support can construct the thick layer stable rock beam of the roof and equivalent support of the side, realizing continuous stress transfer and geometrically coordinated deformation. The support scheme was finally applied to the on-site industrial test, and the mine pressure monitoring results showed that the deformation of the roadway surrounding rock was effectively controlled under the new support scheme.

A Unified Solution for Surrounding Rock of Roadway Considering Seepage, Dilatancy, Strain-Softening and Intermediate Principal Stress

The analytic solution for surrounding rock of roadway is of significance for stability analysis and roadway support. However, analytical solution for surrounding rock of roadway which took influences of water seepage, strain softening, dilatancy and intermediate principal stress all into account did not receive much reporting. To promote research in this aspect, a mechanical model simultaneously considering water seepage, strain softening, rock dilatancy, and intermediate principal stress was established based on porous elastoplastic mechanics, and then unified analytical solution for surrounding rock of roadway was obtained. Based on an example, influences of water seepage, strain softening, rock dilatancy, residual cohesion and intermediate principal stress on surrounding rock of roadway were thoroughly investigated using single factor analysis. The obtained results are as follows: radii of plastic zones and surface displacement of roadway would increase exponentially with water pressure increasing and their magnitudes are greater than corresponding values without water seepage considered; with softening modulus increasing, peak circumferential stress location would slightly shift to deeper surrounding rock, while broken zone radius and surface displacement of roadway would increase in a decay velocity; rock dilatancy has little effect on peak circumferential stress and plastic softening zone radius, while broken zone radius and surface displacement of roadway increase linearly with dilatancy coefficient α1 increasing indicating their magnitudes are overestimated if associated flow rule is adopted; with weighted coefficient increasing, stress components in plastic zones at the same distance from roadway center would increase, while radii of two plastic zones and surface displacement of roadway are reduced, i.e., self-bearing capacity of rock is enhanced considering intermediate principal stress effect compared to Mohr–Coulomb criterion; with residual cohesion increasing, peak circumferential stress remains unchanged, while stress components in plastic zones at the same distance from roadway center would increase and radii of two plastic zones decrease significantly. The above results implicated that water seepage effect should be carefully considered for roadway stability under groundwater environment; strain-softening and flow rule of rock should be reasonably analyzed and chosen to accurately predict surface displacement and broken zone radius of roadway; rock bolt length should be increased with softening modulus increasing, while it can be decreased with intermediate principal stress effect considered; grouting measure is an effective measure to improve roadway stability. In short, the research provides a theoretical basis and some practical engineering implication for roadway support.

The Application of Intuitionistic Fuzzy Set-TOPSIS Model on the Level Assessment of the Surrounding Rocks

The level assessment of surrounding rocks in underground tunnels has essential significance for the stability of surrounding rocks. Its review is affected by many factors. The intuitionistic fuzzy set-TOPSIS model is first introduced to estimate the quality of surrounding rocks accurately. Secondly, the decisive matrix of the intuitionistic fuzzy sets is established. Then, the weighed decisive matrix is obtained. Finally, the degree of membership at different levels regarding the surrounding rock quality is determined. The quality level corresponding to the maximum degree of membership is the final assessment level. The conclusions are drawn that estimating the quality level of surrounding rocks using the method is feasible compared to the actual investigations and other methods. This method can reflect the quality level of surrounding rocks accurately, providing a new route for the quality assessment of surrounding rocks in the future.

Study on the Evolution Laws of Anchoring Property of Surrounding Rock of Argillaceous Weakly Cemented Roadway in Water Environment

This paper is aimed at studying the influence of composition and microstructure on the Jurassic weakly cemented rock mechanical properties. No. 1802 tailentry was used as the engineering background, located in the Danan Lake No. 5 mine in Xinjiang, China. The weakly cemented sandstone compositions were analyzed by using X-ray diffraction instrument. And the microstructure was observed by using a scanning electron microscope. The uniaxial compression experiment was carried out to investigate the mechanical characteristics by using MTS mechanics experimental system, and the uniaxial compressive strength, Poisson’s ratio, and elastic modulus were obtained. The relationships between the mechanical parameters that include the mineral composition, microstructural characteristics, uniaxial compressive strength (UCS), elastic modulus, cohesion, and friction angle of the weakly cemented sandstone and the water content were obtained. The attenuation of the anchorage force of the weakly cemented surrounding rock under different water-rich conditions was studied. The key reason of No. 1802 tailentry surrounding rock structure deterioration and roof fall was found. The model of a single anchor structure was established based on FLAC3D to study the mechanical response of a single anchor structure under different water contents and the distribution and evolution laws of bearing stress field, effective compressive stress, and anchor axial force. The influences of parameters such as water content, pretightening force, and anchor length on the preload diffusion effect of weakly cemented surrounding rock anchorage structures are obtained. The key to controlling the deterioration of the surrounding rock structure of the weakly cemented entry is to reduce the water content of the roof. The research results provide reference for the control of the entry surrounding rock under similar stratum conditions.

Investigation on Damage and Failure Mechanisms of Roadway Surrounding Rock Triggered by Dynamic–Static Combined Loads

Investigation on Damage and Failure Mechanisms of Roadway Surrounding Rock Triggered by Dynamic–Static Combined Loads

Study on Surrounding Rock Deformation Laws of an Argillaceous Soft Rock Roadway Based on the Creep Damage Model

The indexes of argillaceous soft rocks in Western China, such as rock strength and softening coefficient, are much smaller than those of soft rocks commonly seen in other areas. Such argillaceous soft rocks are susceptible to a more serious creep phenomenon if encountering water. Accordingly, the study theoretically constructed a constitutive creep model considering the weakening coefficient and damage of surrounding rocks. Next, the viability of this model was verified by combining numerical simulation and field monitoring. Accordingly, this study conducted a comparative analysis on the creep range and cross-sectional deformation of argillaceous surrounding rocks of a roadway in a titled stratum under dry and damp states. Results showed that the Cvisc model considering the weakening coefficient of surrounding rocks was applicable to the decay creep and uniform creep stage, and that considering the damage of surrounding rocks was applicable to the accelerated creep stage. During the creep process, the argillaceous surrounding rocks were prone to viscoelastic deformation. The damp state had an obvious time effect on the damage of surrounding rocks. Specifically, the creep range was expanded under a damp state at 18 days compared with that under a dry state, and the change in the left and upper displacements was especially significant. The roadway cross-section changed asymmetrically under both dry and damp states, where it was changed into an approximate deflected rhombic shape under the dry state and into an approximate deflected trapezoidal shape under the damp state. Additionally, the roadway cross-sectional change under the humid state was evidently greater than that under the dry state.

Study on Energy Distribution Law and Numerical Simulation of Mining Roadway Surrounding Rock

In underground engineering, the deformation and failure process of the surrounding rock of the roadway is always accompanied by the occurrence of energy. The study of the energy distribution law of the surrounding rock of the roadway plays an important role in its stability. This paper first theoretically analyzes the stress and energy distribution law of the surrounding rock of the roadway, then with the help of numerical simulation method, combined with the existing physical and mechanical parameters, based on the existing support parameters of Dongrong No. 2 Mine, gradually compares and analyzes the distribution of vertical stress and energy under the three support methods of no support, original support, and combined support, and the results found that the vertical stress distribution law under the three support methods is basically the same. High-stress areas appear on the two ribs of the roadway, and low-stress areas appear on the roof and floor. The range of high-stress areas from no support to combined support continues to decrease and becomes more evenly distributed. The energy distribution pattern is basically the same. The overall energy of the coal seam is high. There are high-energy areas at 2 m left and right of the roadway, and the roof and floor energy of the roadway is the smallest. The low energy area extends 5 m up and down, respectively. The range of high-energy areas from no support to combined support is shrinking, and the energy distribution is more uniform.

Study on the Surrounding Rock Pressure Characteristics of Loess Tunnel Based on Statistical Analysis in China

A method of load calculation in a tunnel was adopted in consideration of the state of covering depth. Due to the macropore characteristics of loess soil, the existing demarcation regulations of deep and shallow tunnels are inappropriate for large-section and shallow loess in highway tunnels. To determine the load of large-section loess tunnel and provide a proper reference for structural design, the theoretical basis for distinguishing depth of deep and shallow tunnels, as well as the characteristics of common calculation methods for surrounding rock load on depth, were analyzed. Through statistical analysis and significance analysis, the significance of the variation of surrounding rock pressure with cover depth was studied. Correlation analysis was carried out on significant results to fit the relationship between cover depth and surrounding rock pressure. The results showed that the surrounding rock pressure varied linearly with the cover depth, and the surrounding rock pressure was about 0.3 times the initial pressure in deep tunnels. The surrounding rock pressure of shallow tunnels did not change significantly with the cover depth, and the surrounding rock pressure was loose pressure. A method based on statistics was proposed to distinguish the cover depth threshold (CDT) of deep and shallow tunnels.

Study on Failure Characteristics and Control Technology of Roadway Surrounding Rock under Repeated Mining in Close-Distance Coal Seam

In this study, taking the Sheng’an coal mine as an engineering background, the failure characteristics of the surrounding rock of a roadway under repeated mining in a close-distance coal seam is comprehensively illustrated through field measurements (e.g., drilling imaging), theory analysis and numerical simulation (finite difference method (FDM)). The results show that although the return airway 10905 remains intact, the apparent failure of the roadway’s roof and the coal pillar can be observed. In addition, the expression of floor failure depth caused by upper coal seam mining is obtained through elastic-plastic theory. Meanwhile, the deformation of the surrounding rock of the roadway increases with the increase of repeated mining times, especially for the horizontal displacement of the roadway on the coal pillar side. Moreover, the cracks’ evolution of surrounding rock in the roadway can be observed as asymmetric characteristics. Finally, the stability control technology of “asymmetric anchor net cable + I-steel” is proposed to prevent potential mining disasters, and the feasibility of this support scheme is verified by numerical simulation and field practices. It can meet the requirement of safe mining and provide guidelines to effectively solve the failure of a roadway in close-distance coal seam mining.

Similar Material Proportioning and Preparation of Ductile Surrounding Rocks for Simulating In Situ Coalbed methane Production from Tectonically Deformed Coals

Similar Material Proportioning and Preparation of Ductile Surrounding Rocks for Simulating In Situ Coalbed methane Production from Tectonically Deformed Coals

Application of Three Steps and Middle Column Method in Shallow Buried Tunnel with Strong Expansive Surrounding Rock

Application of Three Steps and Middle Column Method in Shallow Buried Tunnel with Strong Expansive Surrounding Rock

Efficient Excavation and Support Cooperation Technology for Surrounding Rock of Deep Buried Long-Distance and Large Section Gob-Side Roadway: A Case Study

The gob-side roadway technology is widely used in coal mining in China, as it can improves the recovery rate of coal resources and alleviate the shortage of mining replacement. However, it is still difficult to control the stability of surrounding rock in gob-side roadway under deeper mining depth and more complex stress environment. With the auxiliary transportation roadway 30207 (ATR 30207) of the Muduchaideng Coal Mine as engineering background, this paper introduces the engineering case of gob-side roadway characterized by deep buried, long-distance, and large section. Through comprehensive methods, we studied and put forward the efficient excavation-support cooperation technology for surrounding rock of gob-side roadway. The research shows that the head-on cutting of gob-side roadway causes the stress to transfer and gradually adjust in the heading face to form a steady-state advanced abutment stress field. The coupling effect of the advanced abutment stress and the lateral abutment stress of goaf are the main reasons for repeated hole collapse of anchor cable drilling in solid coal rib, development and expansion of the roof separation fracture, and the low excavation speed. Supposed that upon the heading face support is completed, the next excavation-support cycle is quickly started during the early stage of stress adjustment, and the time effect can be fully utilized to alleviate the disturbance intensity of the advanced abutment stress in the heading face, as well as reduce the damage of rock mass. This paper puts forward the time-effect collaborative control countermeasures of the roof and rib in gob-side roadway of “hole collapse anchor cable of solid coal rib lag construction and waits for pressure relief and rapid excavation-support cycle in the heading face.” Engineering practice shows that the mine pressure behavior of roadway roof and solid coal rib is effectively controlled, and the roadway forming speed is greatly improved, which can provide reference for the efficient excavation-support design of gob-side roadway under the conditions of deep buried, long-distance, and large section in similar deep mines.

Stability Analysis on the Steeply-Inclined Small-Angle Layered Surrounding Rock Masses at the Upstream High Sidewall of a Large-Span Cavern

The underground powerhouse of China’s Wudongde hydropower station is one of the world’s underground powerhouses with the largest span and height. Because the underground powerhouse is all located in steeply-inclined layered rock masses, and the bedding plane strike of the rock mass has a small angle with the axis of the main caverns, there is a serious risk of high sidewall instability. According to the basic principles of the structurally-controlled concept, the mechanical properties of bedding planes and other discontinuities are largely attributed to this problem. A thorough investigation was conducted into the Wudongde underground powerhouse throughout the excavation process to clarify the possible mechanisms behind these failures and to realize the dynamic adjustment of construction. First, the geological conditions and mechanical properties of the rock masses in the study area were introduced in detail. The stability of the right bank underground powerhouse’s surrounding layered rock mass was then investigated using a discontinuum-based numerical method. Special attention was paid to the excavation-induced failure mechanisms of the steeply-inclined small-angle layered rock masses at the upstream high sidewall. The results show that the failure of steeply-inclined small-angle layered surrounding rock masses presents significant three-stage characteristics, i.e., 1) rock plate forms due to the unloading opening of the bedding plane; 2) rock plate cracks due to bending; and 3) rock plate buckles or slides due to crack penetration. Based on the understanding of the deformation and failure mechanisms of steeply-inclined small-angle layered rock masses, the excavation sequence needs to be optimized according to local geological conditions. In practice, it is vital to insist on the principles of excavation by thin layers and finish all the supports before the next-step excavation.

Experimental Study of the Plastic Zone and Stress Asymmetric Distribution in Roadway Layered Surrounding Rocks

A three-axis experimental simulation model was established for a roadway with layered surrounding rock by a 20 MPa true triaxial analog simulation equipment, and the corresponding layered surrounding rock numerical simulation model was established by discrete element software. The simulation results showed that the deformation of the roadway layered surrounding rock showed asynchronous deformation with time and asymmetric deformation in space. The measured results of the multipoint displacement meter inside the surrounding rock showed that the order of displacement of surrounding rock from the four corners of the roadway to the center of the roadway were upper right, lower left, upper left, and lower right. Under the influence of the surrounding rock bedding, the shape of the plastic zone of the roadway surrounding rock was irregular. In the area where the rock layer and the surface of the roadway were tangent and in the vertical area between the rock layer and the surface of the roadway, the plastic zone had a large development depth. In other regions, the development depth of the plastic zone was smaller. As a result, the stress values obtained at the monitoring points in the surrounding rock at the same distance from the roadway surface were different, and the stress increase value of the monitoring points in the plastic zone was not large (No. 929). With the expansion of the plastic zone, the monitoring point change from outside the plastic zone to inside the plastic zone, its stress first increased and then decreased (No. 2 and No. 872). The experimental results are of great significance for understanding and controlling the development law of the plastic zone of a layered inclined rock roadway and the deformation control of the roadway layered surrounding rock.