Deep Roadway Research Articles

Mechanism and prevention of coal bursts in gob-side roadway floor under thick and hard roof in the deep mining area of Ordos

The complex stress environment in deep roadways, often exacerbated by thick and hard strata, frequently precipitates coal bursts, posing significant safety hazards. This paper investigates the mechanisms and preventive methods for coal bursts in the gob-side roadway floor (GSRF) under thick and hard roof in the Ordos region, China. First, the stress-distributing characters of GSRF were analyzed then a stress calculation formula was derived. A mechanical model was developed to determine the critical stress for buckling failure of the roadway floor strata. Criteria for the bursting instability of GSRF were then established. The lateral static load from the adjacent gob, the advancing static load from the working face, and the disturbance load from overlying thick and hard roof fractures combine to transmit high loads and energy to the roadway floor via the “roof → rib → floor” pathway, causing increased stress concentration and energy accumulation. When the conditions satisfy the criteria for bursting instability, coal bursts can occur on the roadway floor. To mitigate dynamic load disturbances, the paper proposes roof regional fracturing and abrasive water jet axial roof cutting. Hydraulic reaming of gutters in the roadway ribs and deep hole blasting at the roadway bottom corners are offered to alleviate the static loads on the surrounding rock. The implementation of targeted prevention measures for dynamic and static loads effectively reduces coal bursts in GSRF. These findings offer an example of preventing and controlling coal bursts in other mines of the Ordos region with comparable geological conditions.

Experimental study on the macroscopic and mesoscopic mechanical characteristics of deep damaged and fractured rock

Most of the rock surrounding deep roadways is in a fractured state; fractured rock has significant rheological properties, and the time-dependent mechanical properties of fractured rock affect excavation construction, support design, and long-term stability of deep roadways. Triaxial compression and mercury intrusion tests are conducted on the bearing characteristics of severely damaged and fractured rock samples, indicating the strength degradation properties of these samples. The evolution of the internal pore structure in damaged and fractured rock samples is analyzed in relation to changes in unloading points (pre-peak stage, peak point, and post-peak stage), leading to the establishment of a quantitative evaluation index for rock damage based on the porosity evolution. Short-term rheological testing is performed on rock samples with varying degrees of damage and fracture, demonstrating the evolution of creep and stress relaxation characteristics. The findings contribute to a deeper theoretical understanding of the post-peak mechanical properties of coal and rock masses, which hold significant theoretical implications and can inform research on long-term stability in underground engineering applications, such as deeply buried roadways, tunnels, and chambers.

Load transfer model and failure prevention measures of a mechanical-type anchorage for anchor cable in deep roadway

In this paper, the load transfer mechanism of a mechanical-type anchorage is analyzed and studied. The stress distribution on the surface of the anchor cable is clarified, and the means of mechanical analysis and Abaqus finite element method are used. Results indicated there is no stress concentration, and the peak value indicated by the anchor cable appears near the loading end, and the peak value is about 60 MPa larger than the tensile strength. The results of the tensile test show that the failure mode of the anchor cable is the necking fracture of the steel wires, which indicates that the steel reaches the yield limit stress. The anchor efficiency of mechanical-type anchorage is high, which can effectively exert the tensile strength of anchor cable. In deep mine roadway, two failure modes of anchor cable are summarized when mechanical-type anchorage is used. Including shear failure and slippage failure under dynamic action. Aiming at the shear failure behavior, a new type of anchorage was invented, including the self-aligning and shear resistance functions of the anchor cable, and an experiment was carried out. Results indicated anti-shear anchorage can effectively solve the problem of anchor cable failure caused by shear. For the problem of anchor cable slippage failure under dynamic action. The parameters affecting the stability of mechanical-type anchorage are analyzed by means of theoretical analysis and numerical simulation. Results indicated reducing the bevel angle of wedge and barrel, the difference angle between them, and increasing the friction coefficient μ between wedge and barrel can increase the stability of mechanical-type anchorage. The research content of this paper can provide reference for the design of mechanical-type anchorage in similar underground engineering.

Numerical experimental study on combined support of bolt-arch in circular roadway

The deep soft rock roadway is in high stress environment, and the surrounding rock is prone to large deformation. Appropriate roadway cross-section form and high-strength support are effective control methods for surrounding rock deformation. Circular roadway is widely used in mine engineering because of its uniform stress and deformation, which gives full play to the characteristics of rock compression and non-tension. With the advantages of high strength, high cost performance and stability, the application of arch frame in deep soft rock roadway is increasing day by day. Based on this, based on the engineering background of deep roadway in extremely soft rock in sea area, numerical experiments were carried out using the FLAC3D bolt-arch fine numerical simulation platform. The progressive failure characteristics of bolt-arch combined support in soft rock roadway are revealed. The influence law of roadway section form, geostress grade and lateral pressure coefficient on support effect is clarified. The results show that: (1) Under the condition of deep soft rock, the surrounding rock deformation of circular roadway is uniform. Compared with the straight wall semi-circular roadway, the deformation is reduced by about 86% at most. (2) The failure of arch frame in circular roadway has a significant influence on the final control effect of surrounding rock. When the ground stress exceeds 15 MPa, the loss of bearing capacity of arch frame is instantaneous, and the deformation of surrounding rock increases suddenly. (3) When the support of circular roadway in deep soft rock fails, the axial force of bolt is very small, and it basically does not play a supporting role. According to the research results, the support optimization design is carried out, and the field verification is obtained.

Study on the fractional creep model of roadway filling paste under the coupling effect of pore water pressure and stress

Filling paste in deep roadways is significantly affected by groundwater, especially high pore water pressure, which increases the complexity and variability of the filling paste's mechanical properties. To explore the creep characteristics and long-term stability of filling paste under varying pore water pressure, the MTS815.03 test system is used to conduct creep tests under different pore water pressures and stress. Then the creep deformation of the filling paste under the complex pressure field of static pore water pressures is analyzed. Finally, through the one-to-one correspondence between the numerical simulation of the creep model and the characteristic points of the creep curve, a method for determining the creep parameters under the complex pressure field of static pore water pressures is proposed. Results show that the creep test curves of filling paste under different pore water pressures and stress are in good agreement with the model curves. This shows that the creep constitutive model in this research can better reflect the whole process of creep deformation of filling paste. The result also verifies the rationality of the proposed method to determine creep model parameters. The newly proposed creep model can effectively compensate for the traditional Nishihara model, which is inability to reflect the acceleration of creep and can more accurately describe the creep characteristics of the primary and steady-state creep stages.

Spalling Criterion of Hard Brittle Rock Mass Based on Dilatation Lateral Strain.

Spalling failure is a typical failure phenomenon after excavation and unloading of a deep, hard brittle rock mass, which seriously threatens the safe construction of deep roadways (tunnels) and other projects. From the engineering viewpoint, it is essential to accurately evaluate the range and depth of surrounding rock spalling failure. From the perspective of the laboratory and engineering site, the strength and formation mechanism of hard rock spalling failure were statistically summarized and analyzed. Under uniaxial and low confining pressure conditions, when the load reached the rock damage stress, cracks in the rock penetrated to form a failure plane approximately parallel to the axial loading direction, and the strength of rock mass spalling was much smaller than that of intact rock spalling. A triaxial compression test was conducted to analyze the dilatation axial strain and dilatation lateral strain characteristics of gneiss. The results showed that dilatation axial strain gradually increased with the increase of confining pressure, whereas dilatation lateral strain was almost unchanged. Therefore, a safety factor (FS) based on dilatation lateral strain was developed. Through comparison with other strain-based spalling criteria, the establishment and physical meaning of the method were described in detail. In addition, FS was applied to analyze the deep roadway of the Hongtoushan Copper Mine in China and the Rm415 test tunnel in Canada. The results showed that the spalling criterion could accurately indicate the range and depth of the surrounding rock spalling failure, which verified the rationality and applicability of the new spalling criterion. Thus, FS can be utilized as a new theory and analysis tool for the assessment and prevention of spalling failure in deep hard rock roadways.

Experimental Study on the Bearing Behavior of Bolted and Grouted Broken Surrounding Rock of Deep Roadways in a Coal Mine

Experimental Study on the Bearing Behavior of Bolted and Grouted Broken Surrounding Rock of Deep Roadways in a Coal Mine

Gradient failure mechanism and control technology of deep roadways under the action of deviatoric stress field

Deformation control of deep roadways is a major challenge for mine safety production. Taking a deep roadway with a burial depth of 965 m in a mine in North China as the engineering background, on-site investigation found that significant creep deformation occurred in the surrounding rock of the roadway. The original supporting U-shaped steel support failed due to insufficient supporting strength. The rock mass near the roadway experienced a transition from triaxial stress conditions to biaxial and even uniaxial stress states as a result of excavation and unloading, leading to a gradient stress distribution in the surrounding rock. From the perspective of the roadway's deviatoric stress field distribution, we investigated the gradient failure mechanism of the roadway and validated it through theoretical analysis and numerical simulations. The study found that the ratio of horizontal principal stress and vertical principal stress determines the distribution shape of the surrounding rock deviatoric stress field. The gradient distribution of the stress field in the roadway will cause time-related deformation of the roadway, which will lead to large deformation and failure of the roadway. Based on this, the control mechanism of roadway gradient failure was studied, and then a combined support technology of CFST supports with high bearing capacity was proposed.

Control Effect Analysis and Engineering Application of Anchor Cable Beam-Truss Structure on Large-Deformation Roadway in Deep Coal Mine

In response to the shortcomings of the small support scope of single anchor cable and failure to fully utilize the joint anchoring for surrounding rock, this study summarizes the classification of basic support forms for coal mine roadway surrounding rock and clarifies the main composition and mechanism of anchor cable beam-truss structure. A mechanical model of roadway roof beam under the conditions of no support, single anchor cable support, and anchor cable beam-truss structure support at both ends of the roadway is constructed, and the force and maximum bending moment of roadway roof beam under different support types are compared and analyzed. The study clarifies the bending moment reduction rate of anchor cable beam-truss structure relative to unsupported and single anchor cable support and combines numerical simulation to analyze the response laws of anchor cable beam-truss to prestress distribution and stress shell in roadway surrounding rock. Based on the on-site engineering application of a typical large-deformation mining roadway in a deep coal mine, the important role of anchor cable beam-truss structure in ensuring the safety and stability of surrounding rock in deep high-stress and intense-mining large-deformation roadway is revealed, providing technical references for surrounding rock control of similar conditions in deep roadways.

Study on Reinforcing Anchor Cable Support in Overreach Section of Deep Roadway

With the increasing depth of coal mining, the conditions of deep working face are becoming more and more complex, the stability of surrounding rock of roadway is getting worse and worse, and the problem of deep roadway support is becoming more and more prominent. In this paper, the 24100 working face of Pingdingshan No.11 Coal Mine is taken as the engineering background. In view of the problems of roof crushing and deformation and more net pockets in the return airway affected by the mining of the working face, the grouting anchor cable reinforcement and support technology in the advance section of the deep mining roadway is proposed, and the feasibility of the support effect is verified by numerical simulation. The results show that the influence range of the advance abutment pressure of the air roadway is about 60 m, and the reinforcement support strength required for the roof of the roadway is 50.6 kN/m2. The grouting anchor cable reinforcement support technology system of the return air roadway can control the deformation of the surrounding rock of the roadway and achieve safe and efficient mining.

Study on the failure mechanism of deep roadways considering gradient stress and the control technology of CFST supports

The surrounding rocks showed gradient failure after excavation. And according to the different stress states, the surrounding rock of the excavated roadway is divided into severe damage area, moderate damage area and light damage area. An indoor triaxial unloading test was designed to simulate the damage of surrounding rock under different stress states. It was found that it has the composite failure characteristics of splitting and shearing, and the peak stress is also between the conventional uniaxial and triaxial test results. The relative stress gradient was introduced, and a mechanical model of gradient failure in deep tunnels was proposed and established based on the stress field strength method. Based on the gradient damage mechanism, a combined support scheme of annular concrete-filled steel tube support is proposed, which has a better effect on controlling the deformation of the roadway in the field.

Numerical Study on Failure Mechanisms of Deep Roadway Sidewalls with Different Height-Width Ratios and Lateral Pressures

Numerical Study on Failure Mechanisms of Deep Roadway Sidewalls with Different Height-Width Ratios and Lateral Pressures

Method for Pressure Relief in Deep Coal Mine Roadways Using Borehole Groups and Its Application to Guqiao Coal Mine

Abstract With the increase in the mining depth of coal mines in China, the problem of large deformation of roadways owing to high-ground pressure has become prominent even under enhanced support systems. To reduce the high pressure on the surrounding rock, this study investigates a pressure-relief method for deep roadways using drilling borehole groups. Based on a deep roadway in the Huainan mining area of China, the influences of drilling parameters, such as borehole diameter, length, and arrangement were investigated. The results indicate that the fan-shaped arrangement of the borehole group can compensate for the dilatancy deformation of the surrounding rock. The peak stress of the surrounding rock is reduced and transferred to the inner part of the surrounding rock. Furthermore, a field experiment was conducted on an experimental roadway. The deformation of the roadway was monitored and compared with that of an adjacent roadway that did not apply the pressure-relief method. The monitoring results indicated that the deformation of the experimental roadway was significantly reduced.

Numerical Simulation Study on The Effect of Isolated Coal Pillar Width on The Subsidence Law of Deep Mining

A large number of research results show that the reasonable determination of the width of the coal pillar is an important factor affecting the stability of the surrounding rock along the roadway along the fully mechanized discharge. In this paper, the mechanism of the specific condition of isolation of coal pillars in the deep roadway of Menkeqing coal mine area on the law of surface subsidence is analyzed. The FLAC3D numerical simulation technology was used to simulate the multi-level experimental scheme to analyze the influence of different remaining coal pillar widths on the stress and strain of overburden rock and surface subsidence, and to reveal the relationship between the width of isolated coal pillars and the surface subsidence law of deep mining.

Elastic–plastic criterion solution of deep roadway surrounding rock based on intermediate principal stress and Drucker–Prager criterion

AbstractExcavation‐induced rock failure and deformation near an underground opening boundary is closely associated with the intermediate principal stress, strain softening and rock mass dilation. By combining theoretical analysis and numerical simulation to explore the mechanical evolution of the roadway surrounding rock during excavation. The elastic–plastic criterion solutions for surrounding rock stress, displacement, and the plastic zone of a circular roadway were deduced by including the intermediate principal stress, strain softening and rock mass dilation, based on the Drucker–Prager criterion and the nonassociated flow rule. Furthermore, ABAQUS finite element software was utilized for numerical simulations to scrutinize the influence of mechanical parameters on stress redistribution, surface displacement, and plastic range. The results of the numerical simulations verify the reliability of the theoretical analysis and affirm the high consistency of the results with the theoretical solution. The research findings indicate that the strength of surrounding rock is significantly influenced by the intermediate principal stress, and the deformation and failure of rock mass are primarily impacted by rock mass dilation, while strain softening mainly affects the thickness of the fractured zone. Moreover, the study reveals that enhancing the residual strength of the surrounding rock can improve its resistance to deformation and failure. Furthermore, the excavation of the roadway is observed to increase the original rock stress in the surrounding rock, but increasing the ground support strength effectively controls the deformation and failure of surrounding rock. Ultimately, the research outcomes offer valuable references for engineering calculations and ground support design of surrounding rock in deep roadways.

Numerical Simulation Study on The Effect of Isolated Coal Pillar Width on The Subsidence Law of Deep Mining

A large number of research results show that the reasonable determination of the width of the coal pillar is an important factor affecting the stability of the surrounding rock along the roadway along the fully mechanized discharge. In this paper, the mechanism of the specific condition of isolation of coal pillars in the deep roadway of Menkeqing coal mine area on the law of surface subsidence is analyzed. The FLAC3D numerical simulation technology was used to simulate the multi-level experimental scheme to analyze the influence of different remaining coal pillar widths on the stress and strain of overburden rock and surface subsidence, and to reveal the relationship between the width of isolated coal pillars and the surface subsidence law of deep mining.

Case study on the secondary support time and optimization of combined support for a roadway under high in-situ stress

Roadway support can effectively improve the stability of roadway excavation and ensure the safety of underground mining. This study investigates the secondary support time and parameter optimization of combined support for a deep roadway in the stage of resource replacement in the Huize lead–zinc mine in Yunnan Province, China. The aim of this study is to increase the stability and safety of the roadway and decrease the cost of support. Research on support methods and failure modes has shown that under the action of high in-situ stress in deep mining, the surrounding rock of the roadway exhibits obvious rheological phenomena. The change in the radial displacement of the roadway is combined with creep tests of the main exposed surrounding rock to determine the secondary support time. Numerical simulations and orthogonal tests are utilized to optimize the support parameters in terms of the roof subsidence, floor heave displacement, side displacement, and plastic zone by analyzing the effects of the sprayed concrete thickness, bolt length, bolt row spacing, and bolt diameter on the support results. The proposed secondary support time and combined parameters can provide a reference for roadway support in similar strata.

Asymmetric failure behavior of surrounding rock in the deep roadway: A semi-analytical solution

With increasing buried depth, the true three-dimensional asymmetric stress environment of deep strata changes the failure mode of roadways. Therefore, a mechanical model under the superposition of the geostress field and the mining stress field is established to highlight the failure characteristics of the surrounding rock. Based on four different strength criteria, the semi-analytical solution of the plastic zone (PZ) boundary under asymmetric stress is derived. The influence of the roadway buried depth, geostress deflection angle, lateral pressure coefficient, and mining stress concentration coefficient on the polymorphic evolution of the PZ are analyzed. The results show that the asymmetric concentration of stress, especially shear stress, is the internal cause of asymmetric failure behavior in roadways. The rock's nonlinear mechanical behavior and intermediate principal stress significantly affect the shape and size of the PZ. The PZ presents three different shapes: circular, oval, and petal-shaped, and the shape is closely related to the newly introduced equivalent lateral pressure coefficient. Furthermore, the proposed solution is used to analyze a field case, and the calculation results align well with the measured data. This paper contributes valuable insights into the PZ in deep surrounding rock and guides the design and construction of deep roadways.

Research and development of fully enclosed wire-shell support structure technology for deep soft rock roadway based on TRIZ theory

The TRIZ theory was used to accurately discover the problems to be solved in the design of roadway surrounding rock control technology. This paper tried to solve the complex issue of surrounding rock control in deep roadways from a new perspective. Based on the functional component analysis and causal axis analysis of the problem’s primary reason, simultaneously, the surrounding rock control technology was optimized through technical contradiction analysis, physical contradiction analysis, and substance and field model analysis. As a result, a fully enclosed wire-shell support technology was proposed. Finally, taking the typical soft rock roadway engineering of Pansan Coal Mine in Huainan Mining Area, Anhui Province, China, as the engineering background, the engineering application and effect evaluation were completed. This paper provides a reference for controlling the instability of deep soft rock roadways in coal mines. A new idea of optimizing roadway support engineering based on TRIZ theory was proposed.

A coupled hydro-thermo-mechanical model based on TLF-SPH for simulating crack propagation in fractured rock mass

In this paper, a hydro-thermo-mechanical coupling model based on the smoothed particle hydrodynamics with total Lagrangian formula (HTM-TLF-SPH) is proposed to simulate the crack propagation and instability process of fractured rock mass. TLF-SPH uses the Lagrangian kernel approximation, that is, the kernel function and its gradient need only be calculated once in the initial configuration, which is much more efficient than the smoothed particle hydrodynamics (SPH) based on the Euler kernel approximation. In TLF-SPH, particles interact with each other through virtual link, and the crack propagation path of rock mass is tracked dynamically by capturing the fracture of virtual link. Firstly, the accuracy and robustness of the HTM-TLF-SPH coupling model are verified by a reference example of drilling cold shock, and the simulation results agree well with the analytical solutions. Then, the crack propagation law of surrounding rock and the evolution characteristics of physical fields (displacement, seepage and temperature fields) after excavation and unloading of deep roadway under the coupling condition of hydro-thermo-mechanical are investigated. In addition, the seepage and heat transfer processes of the surrounding rock of Daqiang coal mine under different coupling conditions are successfully simulated. Meanwhile, the effect of the boundary water pressure difference on the temperature and seepage fields under the hydro-thermal coupling condition is quantitatively analyzed.