Roadway Deformation Research Articles

Experimental Study on Deformation Law of Rectangular Roadway in Horizontal Layered Rock Mass

In order to analyze the characteristics and mechanism of roadway deformation caused by high stress in horizontal strata, a physical model with rectangular roadway was designed. The model was constructed by the so-called “Physically Finite Elemental Slab Assemblage (PFESA)” to bring about the structural effect of the deep strata. In the experiment, the vertical and horizontal pressures were increased step-by-step to simulate high stress. The deformation characteristics of surrounding rock in layered rock roadway were observed by video image and digital image correlation method (DIC). The strain and stress characteristics of surrounding rock of roadway in layered rock mass were obtained by using the strain gauge test method, and compared with the deformation characteristics. For the sake of analyzing the deformation and failure mechanism of layers, the mechanical model of layered rock structure was established, and the experimental phenomenon and mechanism were verified. Through systematic study, this paper enriches the research methods of model experiment and provides an experimental basis for practical engineering of similar conditions.

Research on Soft Rock Damage Softening Model and Roadway Deformation and Failure Characteristics.

To determine a reasonable control strategy for deep buried soft rock roadways, a study on deformation and failure characteristics was carried out. The Weibull distribution damage variable was introduced to construct a damage-softening model considering the lateral deformation of the rock mass, and the functional relationship between the model parameters F0 and m and the confining pressure were discussed. The nonlinear fitting method was used to correct the model parameters. Using the model, the failure characteristics of deep buried soft rock roadways were analyzed. A comprehensive and step-by-step joint support control strategy was proposed based on the numerical simulation results. The research results showed that the damage-softening model curve established could genuinely reflect the whole process of mudstone failure. The apparent stress concentration phenomenon occurred in the surrounding rock. The surrounding rock deformation showed that roadway floors had larger plastic failure areas than sides and vaults. The plastic failure depth could reach 2.45 m. After a comprehensive and step-by-step joint support control strategy was adopted, the deformation rate of the roadway at the section was less than 0.1 mm/d. The optimized support scheme can effectively improve the stability of the roadway.

Investigation on Pressure Relief and Roadway Protection Technology by Subsection Hydraulic Fracturing under Strong Mining Pressure in Fully Mechanized Mining

In this study, we analyzed the deformation and stress changes of an auxiliary transport gateway in Buertai coal mine 42106, which is a fully mechanized coal face. We used the directional long drilling hydraulic fracturing technology to weaken the mine hard roof clearance and investigated the overall pressure characteristics of the working face, mining, and two consecutive roadway surrounding rock deformations. The analysis showed that the segmented hydraulic fracturing technology of directional long drilling decreased the pressure in the area affected by the fracturing drilling on the working face after fracturing. The peak pressure decreased by approximately 10.4%, average resistance of the stent was reduced by 2.6%, average resistance of the support decreased by 6.8% under pressure, and dynamic load coefficient decreased by 4%. Furthermore, the roadway deformation decreased, and the coal face was restrained. The stress monitoring value of the surrounding rock was weakened, demonstrating the effectiveness of the fracturing weakening effect.

Highly prestressed NPR cable coupling support technology and its application in the deep roadway

The stability control of deep roadways has always been a difficult problem related to the safe production of mines. This study took the -950 level substation roadway of the Wanfu Coal Mine in China as the project background to study a new support technology with negative Poisson’s ratio (NPR) cables as the core. Firstly, based on the mechanical properties of the NPR cable with a large constant resistance, a high elongation, and uniform full-length energy absorption, the highly prestressed NPR cable coupling support technology was proposed. Its mechanism was revealed, i.e., by strengthening the surrounding rock with a high prestress and releasing its deformation energy with a large constant resistance and a large deformation, the “stress compensation” effect of the NPR cables can be brought into full play so that coupling of the “support-surrounding rock” can be achieved. Secondly, the numerical model of the second-generation NPR cable was established by FLAC3D, which can realise the constant resistance and large deformation of the NPR cable and achieve the sequential breaking of the NPR steel strands during the deformation of the NPR cable. Numerical tensile tests verified its effectiveness. Finally, the NPR cable support scheme was designed through theoretical calculations and numerical simulations. After field application, the roadway deformation was constrained within 80 mm, effectively preventing engineering failures. This study may serve as guidance for similar projects.

Deformation and Failure Mechanism of the Lower Roadway in a Close-Range Residual Coal Pillar Area

The Tashan coal mine is selected as a case study to determine the deformation and damage mechanisms of the lower roadway in a close-range residual coal pillar area. Roof drilling peephole technology is applied to detect the damage to the roadway roof surrounding rock. A boundary invisibility equation is derived for the plastic zone of a circular hole based on the theory of a butterfly plastic zone in a non-uniform stress field in which the principal stress occurs at an arbitrary angle to the vertical. Maple mathematical drawing software is combined with FLAC3D numerical simulations to investigate the influence of the principal stress ratio and direction on the roadway plastic zone. The results indicate that the plastic zone of the roadway surrounding rock assumes a butterfly shape when the bidirectional stress ratio is large, and the direction of the butterfly-shaped failure of the roadway is related to the principal stress direction. Field test images are combined to show that the asymmetric damage pattern of the lower roadway in a close-range residual coal pillar area is influenced by the presence of the roadway in a non-uniform stress field in which the main stress direction is deflected.

Model test on creep deformation and failure characteristics of soft rock roadways

This paper studies the creep deformation and failure characteristics of a soft rock roadway under the condition of combined support through a model test that lasted for 30 days. Under the action of high stress, the soft rock roadways present a tendency of continuous failure and nonconvergence, and the cross-sectional area shrinks to 52.3 % of the original roadway. The failure of the anchorage zone causes the bolt to lose its supporting function, and the continuous extrusion leads to the cracking of the lining and the shrinkage of the arch. Floor heave is the superposition of geometric deformation and loose deformation. The floor is continuously replenished by the movement of the surrounding rock below and to the two sides and moves upward under the combined action of high-level stress and vertical stress. Finally, the model test conclusion is verified by field tests, and deformation control schemes are proposed.

Research on Theory and Technology of Floor Heave Control in Semicoal Rock Roadway: Taking Longhu Coal Mine in Qitaihe Mining Area as an Example

Abstract As one of the most common disasters in deep mine roadway, floor heave has caused serious obstacles to mine transportation and normal production activities. The third section winch roadway in the third mining area of Qitaihe Longhu coal mine has a serious floor heave due to the large buried depths of the roadway and the semicoal rock roadway, and the maximum floor heave is 750 mm. For the problem of floor stability, this paper establishes a mechanical model to analyze the stability of roadway floor heave by analogy with the basement heave of deep foundation pit. It provides a model reference for analyzing the problem of roadway floor heave. Aiming at the problem of roadway floor heave in Longhu coal mine, the roadway model is established by using FLAC3D, and the roadway model after support is established according to the on-site support measures. Through the analysis of the distribution of roadway plastic area, stress nephogram, and displacement field simulation results, the results show that the maximum displacement of roadway roof and floor after support is reduced by 15% and 23%, but the maximum floor heave is still 770 mm, which is close to the measured floor heave of roadway. In order to solve the problem of roadway floor heave and integrate economic factors, this paper puts forward three support optimization schemes, simulates the support effect of each scheme, and finally determines that scheme 3 is the best support optimization scheme. Compared with that under the original support, the amount of floor heave is reduced by 81%, and the final amount of floor heave is 150 mm, which can meet the requirements of roadway floor deformation. The results provide a scheme and guidance for roadway support optimization.

True 3D geomechanical model test for research on rheological deformation and failure characteristics of deep soft rock roadways

Deep soft rock roadways generally present large deformation characteristics, and a vast number of workers attempt to repair them to no avail. A true 3D model test was performed based on the engineering background of the transportation roadway of the Huafeng coal mine in China. The selected analogous materials have a significant time similarity relationship with the surrounding rock, and a similar bolt-mesh-shotcrete support structure, according to the engineering background, was applied to the roadway. The test results showed that the evolution process of the rheological deformation of the roadway is two sidewalls → floor → vault → full-section convergence of the roadway. The large deformation zones of the surrounding rock are constantly transferred from the surface to the depth, and the bearing capacity of the bolts decreases rapidly after the deformation of the anchorage zones. The mechanical characteristics of the floor determine that the lower surrounding rock always repeats the failure process of the upper rock stratum, and the floor heave does not stop. The test results revealed the full-section convergence rheological deformation laws and migration laws of the internal key deformation locations of the surrounding rock and clarified the reasons for the floor heave. The model test results are verified through field monitoring, and opportunities and suggestions for secondary support are determined. These results could provide a reference for the failure process and control technology of the same type of deep soft rock roadway.

Failure characteristics and control techniques for mining roadway affected by stress accumulation of residual pillars in contiguous coal seams

During contiguous coal seams mining, the upper goaf residual pillars often cause strong ground stress in underlying longwall mining face and stress accumulation can result in severe mining roadway failure and deformation. To address this issue, the strata stress behavior of working face and the failure and deformation process of an affected roadway at Tashan coal mine were studied in this work. The failure and deformation process of the mining roadway surrounding rock were monitored using the borehole endoscope and the laser range finder. The distribution characteristics and evolution process of vertical stress and failure zone around the affected mining roadway were simulated by FLAC3D. The mechanism of the large deformation and failure of the roadway were revealed based on the numerical simulation. The results indicate that: (1) the supports working resistance below the residual pillar are generally high with an average value of 9726.6 kN, while that below the goaf are generally low with an average value of 7655.5 kN; (2) the deformation and failure degree are relatively moderate for the affected mining roadway beyond 30 m away from the mining face, and it is relatively severe within 30 m away from P30515 working face; (3) the fundamental causes of large deformation and failure of the affected mining roadway are the combined concentrated stress of the residual pillar and the advanced abutment pressure of the working face; (4) hydraulic fracturing was adopted to degrade the residual pillar’s mechanical properties based on its concentrated stress distribution characteristics, which cuts off the stress transfer path of the overburden strata and improves the stress environment of the mining roadway.

Impact of Depressurizing Boreholes on Energy Dissipation in Deep Roadway

Depressurizing borehole drilling is an effective approach to control the large deformation of deep roadway. It can transfer the high stress in the proximity of the roadway into the deep stable rock masses. However, it should be noted that the borehole drilling will inevitably cause the secondary damage to roadway. To determine the parameters of depressurizing boreholes, the degree of the secondary damage must be evaluated properly. Given that the rock mass failure is an unstable phenomenon driven by energy, it is of great use to reveal the disturbing impact of depressurizing boreholes on the roadway stability from the angle of energy dissipation. This is much more consistent with the failure nature of rock mass. Hence, an integrated method of laboratory test, numerical simulation, and theoretical analysis was used to study the disturbing effect of depressurizing boreholes on roadway energy dissipation. The equations of elastic energy and dissipated energy of rock cell grid were derived based on the energy principle and finite-difference algorithm, which was implemented into FLAC3D software by the FISH language. The numerical stress-strain and dissipated energy-strain curves of rock samples were verified by experimentally obtained data, and the whole deformation path from roadway excavation to instability was back-analyzed by the dissipated energy evolution. Based upon the energy model, the ratio of borehole diameter D to row spacing R ( D / R ) was selected as the variable to analyze the influence of borehole parameters on the depressurizing effect. The varying D / R leads to three depressurizing states: insufficient depressurization, sufficient depressurization, and overdepressurization. Increasing D / R will make the roadway transfer from insufficient depressurization to sufficient depressurization and finally to overdepressurization. The sufficient depressurizing state could be realized by adjusting the borehole D / R value, which is of great use to the roadway control. The D / R values of 1 : 6 to 1 : 2 were proposed for the test roadway, and D / R = 1 : 6 was applied in the field test, which achieved a well roadway control effect.

Research on Application of the Bolt-Truss Coupling Support Technology in Roadway With Water-Rich and Soft Rock

In the process of underground energy mining, the stability of roadway support is an important guarantee. In order to study the application of the anchor cable-truss support technology in water-rich soft rock roadways, the mechanical analysis of the anchor cable-truss structure is carried out, and the surrounding rock deformation of different supporting methods is numerically simulated under the consideration of the fluid–solid coupled interaction. We observed that the anchor cable (rod)-double arch truss coupling support can control the deformation of the surrounding rock and the expansion of the plastic zone well. The maximum vault subsidence of the roadway is 0.017 m, the horizontal convergence is 0.054 m, and the deformation of floor heave is 0.02 m, which are 3.8, 16.3, and 4% of the deformation under unsupported conditions, respectively; the roadway deformation is effectively controlled. The research results have certain guiding significance for the support design of the water-rich broken soft rock roadway.

Deformation and Failure Law of Roadway along Goaf and Reserve Width of Section Coal Pillar

It was a non-negligible problem in the reserve of section coal pillar in coal mining. Reasonable section coal pillar width and support parameters can not only ensure the stability of surrounding rock of roadway but also produce more coal resources and save support cost. In this paper, the mining of 9106 workface of Linfen Tianyu Hengsheng Coal Industry of Wanbei Coal Power Group was taken as the research engineering background. FLAC3D numerical simulation software was used to simulate and analyze the laws of deformation failure of 6 m, 7 m, 8 m, 9 m, and 10 m coal pillars and surrounding rock of roadway along goaf without support conditions during the mining of 9106 workface. On this basis, the deformation failure law of 7 m and 8 m coal pillars and surrounding rock of roadway along goaf under different supporting conditions (bolt and cable with different row spacing) were further simulated and analyzed. The results showed that when 7 m coal pillars were reserved in 9106 roadway along goaf, the optimal bolt row spacing was 800 mm. When 8 m coal pillars were reserved, the bolt row spacing was preferred to be 900 mm. At this time, the width of coal pillar and support parameters can ensure the stability of roadway surrounding rock during the mining process of 9106 workface and can produce more coal resources and save support cost.

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.

Deformation, Failure, and Acoustic Emission Characteristics under Different Lithological Confining Pressures.

When a temporary support is used to control new surrounding rock in a deep mining roadway, the new surrounding rock is supported by the working resistance of the temporary support. In this study, the influence of deep well boring roadway deformation and rock failure characteristics under different surrounding pressure was investigated. In this paper, for each confining pressure, we experimentally identified the stress-strain, strength, and acoustic emission characteristics of the rocks. The results show that: the surrounding pressure has a significant effect on the damage deformation characteristics of the rock, and the change of the surrounding pressure directly affects the strength, damage form and elastic modulus of the rock; the strength limit of the rock increases with the surrounding pressure, and the damage form of the rock gradually changes to ductile damage with increase of the surrounding pressure; the elastic modulus of the rock increases non-linearly with the increase of the surrounding pressure. The acoustic emission signal of a rock can be divided into three stages: calm, sudden increase, and destruction. The acoustic emission ringing count rate increases suddenly and reaches a peak before the main fracture. Therefore, a sudden increase in the acoustic emission value can be considered a precursor to rock destruction.

Numerical study on the deformation and failure of soft rock roadway induced by humidity diffusion

In underground space engineering, the humidity in the environment has a great influence on the structural performance of soft rock roadway. It not only changes the stress state of rock mass, but also weakens the physical and mechanical properties of surrounding rock, resulting in many accidents such as swelling deformation and even collapse of the roadway. In this paper, the deformation and failure process of soft rock roadway in high humidity environment are simulated by using the humidity diffusion-deformation-fracture coupling model based on the finite-discrete element method (FDEM). Firstly, the coupling model is verified through two simple examples with analytical solutions. Then, the humidity diffusion and floor heave of soft rock roadway after excavation are studied by using the coupling model. The results show that only the humidity of the surrounding rock surface changes greatly at the beginning of excavation and the roadway floor heave caused by humidity is small but with a large change rate. However, with further diffusion of humidity, the displacement of the floor increases slowly at a constant rate. Besides, several main factors affecting floor heave are studied, including humidity swelling coefficient, initial elastic modulus, and initial humidity of floor. Finally, the coupling model is used to simulate the roadway failure process induced by humidity diffusion. The numerical results provide a better understanding of the deformation and failure behavior of soft rock roadway in high humidity environment.

Back Analysis of Surrounding Rock Parameters in Pingdingshan Mine Based on BP Neural Network Integrated Mind Evolutionary Algorithm

The mechanical parameters of surrounding rock are an essential basis for roadway excavation and support design. Aiming at the difficulty in obtaining the mechanical parameters of surrounding rock and large experimental errors, the optimized BP neural network model is proposed in this paper. The mind evolutionary algorithm can adequately search the optimal initial weights and thresholds, while the neural network has the advantage of strong nonlinear prediction ability. So, the optimized BP neural network model (MEA-BP model) takes advantage of the two models. It can not only avoid the local extreme value problem but also improve the accuracy and reliability of the prediction results. Based on the orthogonal test method and finite element analysis method, training samples and test samples are established. The nonlinear relationship between rock mechanical parameters and roadway deformation is established by the BP model and MEA-BP model, respectively. The importance analysis of the three input variables shows that the ∆D is the most important input variable, while ∆BC has the smallest impact. The comparison of prediction performance between the MEA-BP model and BP model demonstrates that the optimized initial weights and thresholds can improve the accuracy of prediction value. Finally, the MEA-BP model has been well applied to predicting the mechanical parameter for the surrounding rock in the Pingdingshan mine area, which proves the accuracy and reliability of the optimized model.

Investigation of Overburden Movement and Ground Stress Behaviour in Multiseam Mining

Abstract In multiple-seam mining, severe deformation of roadways and coal bursts caused by overlying coal pillars can occur in the lower seams. Overburden movement and ground pressure behaviour when mining thick seam below the strong roof and upper four extracted coal seams were investigated in the Tongxin coal mine, China. The numerical model indicated that the abutment stress in the lower seam is affected by overlying coal pillars as suggested by the bubble and the cantilever beam models. The microseismic monitoring indicated that high-energy seismic events caused by large overburden movement under the overlying pillars were the source of the dynamic loads. The influence of upper pillar on lower longwall mining conditions can be broken down into three cases: (a) under no pillar area, no excessive deformation or dynamic failure was observed in the tailgate with medium static loads and low dynamic loads; (b) under single pillars or two overlapping pillars, severe deformation occurred in the tailgate with low to medium static loads and medium dynamic loads; and (c) under the three to four overlapping pillars, extreme deformation was observed with the high static loads and high dynamic loads. These findings can provide guidance for the roadway layout in the multiple-seam operations.

Key Parameters of Surrounding Rock Roof Cutting and Pressure Relief Control in Soft Rock Roof Roadway of Deep Mine Stope and Its Engineering Application

Abstract In this study, the movement and failure law of working face overburden and the distribution characteristics of mining stress are analyzed using laboratory test and numerical calculation methods to address the problems of large deformation, failure instability, and difficult maintenance of the soft rock roof roadways of deep stope influenced by strong disturbance, the roof gas comprehensive treatment roadway of 17191 (1) working face of Pansan mine of China Huainan Mining Group was considered as the engineering background. The deformation and failure mechanisms of the surrounding rock in soft rock roof roadway are revealed, the surrounding rock control technology of presplitting and roof cutting pressure relief is proposed, and the key parameters of presplitting and roof cutting are systematically studied. According to the results, after mining, the overburden presents the distribution of “upper three zones,” in which the heights of the caving and fracture zones are 7 m and 38 m, respectively, the influence range of lateral mining abutment pressure is 80 m, and the influence height exceeds 42 m. The roadway is located in the same layer as the fracture zone and within the influence range of mining. Under the influence of overburden migration of the working face, the stress field around the roadway, and the mining stress field, the surrounding rock of the roof roadway is significantly damaged, and the floor heave is violent. Based on the stress distribution characteristics of the stope and the deformation mechanism of the roadway, the pressure relief control technology of surrounding rock presplitting roof cutting is proposed. The optimal values of key parameters are determined as the roof cutting height of 49.9 m, the roof cutting angle of 10°, and the blast hole spacing of 10 m. The results of this study have been successfully applied in 17191 (1) working face.

Stress Distribution Law of Full-Length Anchorage Bolt in Rectangular Roadway

To study the evolution law of axial force and shear stress of a full-length anchorage bolt in a rectangular roadway during roadway driving and working face mining, based on the stress analysis of the bolt, considering the elastic parameters and geometric size of the bolt, the effect of a bearing plate on surrounding rock, roadway cross-section shape, roadway deformation degree, and roadway elastic parameters, elastic mechanics and mathematical analysis methods were used to establish the mechanical model describing the interaction between the bolt and surrounding rock, and the mechanical formulas for calculating the axial force and shear stress of the bolt were derived. Taking the mining roadway of 1,131(1) working face in the Zhujidong coal mine of the Huainan mining area as the engineering background, the axial force and shear stress of the bolt in the middle of the roof and side of the rectangular roadway with the advance of driving face and working face were analyzed. The mechanical model and theoretical analysis results are verified by installing force measuring bolts with the same mechanical properties as the field and observing the real axial force distribution of the bolts.

Deformation Characteristics and Control Countermeasures for Surrounding Rock of Deep Roadway under Mining Disturbance: A Case Study

Highly efficient maintenance and control of the deep strong mining roadway’s stability is a reliable guarantee for the safe production and sustainable development of a coal mine. With return air roadway 4106 in Wenjiapo coal mine as the research background, an in situ investigation, numerical simulation, and engineering practice were carried out to reveal the stress distribution and surrounding rock deformation and failure characteristics of a strong mining roadway. The numerical simulation results show that both first mining and secondary mining are positively correlated with the deformation and failure of roadway surrounding rock. The peak abutment pressure of the coal pillar near the goaf caused by first mining and secondary mining are 28.7 and 35.6 MPa, respectively, with a 24% increase. During the first mining period, the total deformation of the roof and floor of the roadway and the two sides was 1160 and 1436 mm, respectively. During the second mining period, the total deformation of the roof and floor of the roadway in a working face advance gradually increased from 1737 mm 80 m away from the working face to 2281 mm at the working face, and the total deformation of the two sidewalls gradually increased from 2094 mm 80 m away from the working face to 2211 mm at the working face. The damage to the roadway caused by secondary mining was much greater than that caused by the first mining. The collaborative control technology of long anchorage-top-cutting blasting stress relief is proposed to control the stability of the roadway. The engineering practice shows that the deformation of the roadway is effectively controlled under strong mining disturbance, and the maximum deformations of the roof, floor and sidewall are 17, 23, and 11 mm, respectively.