Circular Roadway Research Articles

Case Study on Rock Support Technology for Roadways Based on Characteristics of Plastic Area

Rocks surrounding deep, high-stress roadways typically undergo a vicious cycle of destruction → repair → re-destruction → re-repair over a long time. This article uses the roadway restoration project of Pingmei Mine No. 6 (400 m underground) as research object. Starting from the plastic area, the characteristics of the distribution of rock surrounding the circular roadway are analyzed, and the influence of the side pressure coefficient, cohesive force, inside friction angle, support strength, and roadway radius on the plastic area is studied. Four types of distribution patterns were observed in rocks surrounding the plastic area of the roadway: round, oval, rounded rectangle, and butterfly. The side pressure coefficient, cohesive force, and inside friction angle affected the distribution and range of rocks surrounding the plastic area of the roadway. The support radius of the roadway and the support strength of its face did not change the distribution of the plastic area, but only affected its size. Therefore, to maintain the long-term stability of weak and broken roadways, the strength of the surrounding rocks must be increased, and roadway renovation should be avoided as it affects the distribution of the plastic area and reduces its scope. Engineering practice has shown that the “anchor net spray + hollow grouting anchor cable” technology for the combined, step-by-step repair and support of roadways, with a hollow grouting anchor cable as core, can suppress the distribution and scope of the plastic area to guarantee safe and long-term use of the roadway.

Research on the relationship between coal burst tendency and rockburst risk of coal seam

ABSTRACT The burst tendency and the risk of rock burst are of great significance in the research of coal mine, which is the basis for the prediction and prevention of rock burst. In order to avoid the confusion of two basic concepts, their essential properties and differences are discussed in detail. In this paper, a prediction model of rock burst in circular roadway based on disturbance response instability theory is proposed, and the critical stress formula of burst is derived to obtain the relationship between the burst tendency and the rockburst risk. The results show that the burst tendency is a necessary condition and an important index to evaluate the strength of the rockburst risk. The risk of rock burst is the possibility and harm degree of rock burst in coal seam with burst tendency. A new identification index of burst tendency and a new evaluation index of rock burst risk are put forward, which provides a new method for the risk evaluation and provides theoretical guidance for prevention and control.

Plastic failure zone characteristics and stability control technology of roadway in the fault area under non-uniformly high geostress: A case study from Yuandian Coal Mine in Northern Anhui Province, China

Abstract In order to explore the effective support method for deep broken roadway, based on the in situ stress test results, the analytical and numerical solutions of the stress and the range of plastic failure zone (PFZ) in a circular roadway subjected to non-uniform loads were obtained using analytical and finite difference numerical methods based on the elastoplastic theory, respectively. Their comparison results show that the analytical and numerical methods are correct and reasonable. Furthermore, the high geostress causes the stress and range of PFZ in roadway roof and floor to increase sharply while those in roadway ribs decrease. Moreover, the greater the difference of horizontal geostress in different horizontal directions is, the larger the range of PFZ in roadway roof and floor is. The shape of PFZ in roadway varies with the ratio of horizontal lateral pressure coefficient in x-direction and y-direction. Finally, according to the distribution characteristics of PFZ and range of PFZ under the non-uniformly high geostress, this paper has proposed a combined support scheme, and refined and optimized supporting parameters. The field monitoring results prove that the roadway deformation and fracture have been effectively controlled. The research results of this paper can provide theoretical foundation as well as technical reference for the stability control of deep broken roadway under non-uniformly high geostress.

Joint Support Technology and Its Engineering Application to Deep Soft Rock Tunnel with Strong Creep

Deformation control of soft rock in deep roadways has always been a challenge in coal mining. The strain softening and rheological properties of high-stress soft rock not only cause large deformation of the surrounding rocks, but also lead to a long duration of deformation. Based on previous research results obtained here in China as well as abroad, this study focused on the S2S2 mining roadway in the Xiaokang Coal Mine of Liaoning Province in China for research and studied the characteristics and damage of its surrounding rock deformation. Furthermore, the sectional form that should be used in roadway construction, as well as the support structure types and parameters were proposed to control the excessive deformation of the surrounding rock. It is suggested that a circular section should be adopted as the mining roadway section, and the high-strength rock should be bolted together, employing the combination of the anchor cable support method. Industrial tests have verified that the circular roadway under the new support mode can enable relative distance changes between the roadway walls, make the roof and floor relatively flat, and reduce the convergence speed to a value lesser than that of the original support mode. The most important advantage is that under this joint support mode, the deformation and damage of the circular roadway would be less affected by mining activity, so the deformation and damage of the mining roadway can be controlled effectively. Therefore, the research results of this study can provide a reference value for similar engineering projects.

Analysis of the rock stratum in a mining area in China with virtual reality technology

Virtual reality (VR) technology can promote the development of mining activities. A mining area in Henan, China, was taken as an example, and a VR system of the mining area was established through the VR-Platform software. Mechanical data of the rock stratum in the mining area were analysed with a rock-fracture-process analysis system. The fracture of the mine roadway was taken as an example to analyse the rock stratum fracture of a circular roadway, a rectangular roadway and the roadway support. It was found that roadways with different shapes had different fracture situations. The cracks occurred randomly, and a closed or non-closed near-annular fracture zone might appear. The roadway support could effectively reduce the fracture of the rock stratum and improve the stability of the roadway. This study proved the important value of VR technology in the mineral industry, which is conducive to providing a scientific guidance for the planning of the mining of the mining area and promoting the orderly development of mining work.

Analysis of Deformation of Circular Roadway Considering Effects of Intermediate Principal Stress and Dilatancy

Based on the unified strength theory and non-associated flow rule, with the consideration of the effects of intermediate principal stress and dilation characteristics, the analytical expressions of surrounding rock stress, displacement and plastic zone radius were obtained. Then the influences of the intermediate principal stresses and dilation angles on the surrounding rock stress, displacement and the plastic zone radius were analyzed by engineering example. The analysis shows that surrounding rock stress distribution and plastic zone radius have close relations with the intermediate principal stress. With the increase of the intermediate principal stress coefficient, the ultimate strength of surrounding rock increased, but the plastic zone radius shows a decreasing trend. The displacement of plastic zone is not only related to the intermediate principal stress coefficient, but also to the dilation angle. The displacement of plastic zone increased with the increase of dilation angle, and the displacement of plastic zone decreased with the increase of the intermediate principal stress coefficient.

Study on distribution law and influencing factors of surrounding rock plastic zone in mining roadway

By analyzing and studying the deduced theory of the surrounding plastic zone in the circular mining roadway, it is found that the radius of the surrounding plastic zone in the roadway considering the influence of mining coefficient can be divided into two stages: In the first stage, when the mining coefficient is small, the radius of the plastic zone is less sensitive to the mining coefficient, and the process increases linearly with the gradual increase of the mining coefficient. In the second stage, when the mining coefficient increases to a certain extent, the sensitivity of the radius of the plastic zone to the mining coefficient increases rapidly, and the non-linearity increases rapidly with the increase of the mining coefficient. With the gradual increase of the mining coefficient, the geometrical distribution morphology of the surrounding plastic zone of the roadway varies from circular to ellipse to round rectangle to butterfly, and the larger the mining coefficient, the more easily the surrounding rock is butterfly plastic zone, and the developmental dimension and range of the butterfly-leaf are larger. The growth of the buried depth of the roadway and the decrease of the cohesion and internal friction angle of the surrounding rock will lead to an increase in the radius of the plastic zone. With the rise of the mining coefficient, the sensitivity of the plastic zone radius to the buried depth of the roadway, cohesion and internal friction angle gradually enhanced. The butterfly plastic zone of the mining roadway has directional, and the butterfly-leaf will rotate to different degrees with the change of the principal stress direction of the surrounding rock of the roadway, When the maximum depth of butterfly-leaf plastic zone is located directly above the roof of roadway, the roof stability is the worst, and roof caving is easy to occur, thus, the support should be strengthened.

Analytic solutions of a reducible strain gradient elasticity model for solid cylinder with a cavity and its application in zonal failure

• Reducibility condition for the fourth-order equilibrium equation . • Analytic solutions of the fourth-order equilibrium equation in the strain gradient elasticity model for a solid cylinder with a cavity. • Classification of analytic solutions in the strain gradient elasticity model for a solid cylinder with cavity. • Quasi periodic solution explaining the occurrence of zonal failure. In this work, the reducibility condition of the fourth-order equilibrium equation in the strain gradient elasticity (SGE) model for solid cylinder with a cavity is obtained. When the reducibility condition is satisfied, the analytic displacement, generalized radial stress , and generalized angular stress can be solved out, and according to the higher-order coefficients, internal length scale, and Lamé constants , the displacement, generalized radial stress, and generalized angular stress are classified into four types: (1) conventional elasticity solution, (2) quasiperiodic SGE solution, (3) monotonous SGE solution, and (4) non-real-number solution. Quasiperiodic generalized radial stress and generalized angular stress are used to explain the occurrence of zonal failure of surrounding rock of a circular roadway. Numerical analysis with MATLAB is applied to study the influence of loading on zonal failure of surrounding rock of a circular raodway.

State of Access Roadways under Selvedges at Stratified Deposits

The results of experimental and analytical studies into the state of access roadways under selvedges of gently dipping sedimentary sheet-like bodies are presented. The stresses in rock mass under the selvedges of seams are determined. The state criterion was assumed the ratio of the maximal compressive stresses at boundary of a reference circular cross section roadway in an elastic medium and at the boundary of the roadway under the hydrostatic stress field. The results of the instrumental and visual observations in mines as well as the data of equivalent material modeling and analytical solutions agree.

Failure Mechanism for Surrounding Rock of Deep Circular Roadway in Coal Mine Based on Mining‐Induced Plastic Zone

In order to reveal the failure mechanism of the deep roadway under mining‐induced pressure in coal mine, the boundary equations for the plastic zone around the deep roadway were deduced, and then the evolution laws for morphology of the plastic zone and the relationship between the morphological indexes and the stability of surrounding rock were discussed. The results show that, for the deep roadway, the effect of mining on the plastic zone is more sensitive than that on the shallow one. Even if the changes of mining influence are small, they may also cause extremely serious plastic failure of surrounding rock masses, leading to the sudden instability of the roadway. When the plastic wings of the plastic zone are approximately perpendicular to the roof, floor, or sidewall, the large deformation and failure of the deep roadway are very likely to occur. Compared with the index of the uniformity coefficient, the irregular shape coefficient can be used to better characterize the differences in the plastic zone morphology. Finally, a case study was provided to apply the principles for the formation and extension of a butterfly‐shaped plastic zone.

Studies on rock failure of layered rock in underground mining-face and control techniques

The failure of layered rock in underground mining face may be influenced by the slipping among the layers. The shear failure around the excavation circular roadway is the main failure type in layered rock. To Study the rock failure in layered rock, the condition of bedding slipping in rock is analyzed, and the stresses distribution around circular roadway is calculated. Based on the analysis results, the Flac 3D software is used to analyze the failure of layered rock in roadway floor. Discontinuous interfaces are created to study the effect of bedding planes. The failure of floor is described at two phases: roadway stability phase and mining-face recovery influencing phase. The results indicate that a shear failure surface occurs at the side of coal pillar during the first phase; a shear arched plane occurs at the side of mining-face during the second phase. The results of numerical model are in good agreement with monitoring data. Finally, bolts reinforcement design is proposed to eliminate the development of failure zone in layered rock.

Experimental Investigation of Laws during Deformation of Circular Roadway in 10° Inclined Layered Rock

In order to analyze the deformation characteristics and mechanisms caused by high tectonic stress in gentle dip strata, a physical modeling with circular tunnel 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. The gravity was fixed while the lateral pressure increased step by step to mimic high tectonic stress. In order to observe the displacement in different area, the sketches of monitoring points and frame in the model surface were drawn down through video pictures in different periods and to be compared. For the sake of analyzing the deformation and failure mechanism of layers, rock structural mechanics models were set up for the left side and right side in the same stratum, respectively. For verifying the experimental phenomenon and its mechanism, infrared images were utilized based on the temperature variation mechanisms of material. Through systematic study, this paper enriches the research methods of model test and can provide a certain reference for practical engineering of similar conditions.

Dynamic caustics test of blast load impact on neighboring different cross-section roadways

Using digital laser dynamic caustics experimental system and conducting simulation experiment researched the influence rule of blasting excavation of a new roadway on neighboring existed different cross-section roadways. The experimental results show that the influence of blast load on adjacent roadway has a good relationship with the cross-section of roadway. The expansion distance of precrack existed in circular, arch-wall, rectangular roadway is respectively 1.76, 1.61 and 0cm under blast load. At the same time, the direct-blast side of rectangular roadway has more obvious damage compared with circular and arch-wall roadway. It explains that plane reflects more stress wave than arc, so that it exerts more tensile failure in the direct-blast side, which leads to less stress wave diffracting to the precrack in the back-blast side. When the precrack extends, higher value dynamic stress intensity factor in circular roadway works longer than that of arch-wall roadway. Indirectly, it explains that plane’s weakening function on stress wave is significantly stronger than arc. Stress wave brings about self-evident influence on the upper and bottom endpoints of the rectangular roadway, and it respectively extends 1.03, 2.06cm along the line link direction of the center of the blasthole and the upper and bottom endpoints on the right wall.

Analytical solution for a circular roadway considering the transient effect of excavation unloading

The rocks surrounding a roadway exhibit some special and complex phenomena with increasing depth of excavation in underground engineering. Quasi-static analysis cannot adequately explain these engineering problems. The computational model of a circular roadway considering the transient effect of excavation unloading is established for these problems. The time factor makes the solution of the problem difficult. Thus, the computational model is divided into a dynamic model and a static model. The Laplace integral transform and inverse transform are performed to solve the dynamic model and elasticity theory is used to analyze the static model. The results from an example show that circumferential stress increases and radial stress decreases with time. The stress difference becomes large gradually in this progress. The displacement increases with unloading time and decreases with the radial depth of surrounding rocks. It can be seen that the development trend of unloading and displacement is similar by comparing their rates. Finally, the results of ANSYS are used to verify the analytical solution. The contrast indicates that the laws of the two methods are basically in agreement. Thus, the analysis can provide a reference for further study.

Study on the Optimal Equivalent Radius in Calculating the Heat Dissipation of Surrounding Rock

The heat dissipation of surrounding rock of a non-circular roadway is computed using an equivalent circular roadway approach under three circumstances when the area, perimeter, or hydraulic diameter of the circular roadway is equal to the non-circular roadway to obtain the optimal equivalent radius. The differential equations of heat conduction for unstable surrounding rock are established in cylindrical and rectangular coordinate systems using dimensionless analysis method. The calculation formulas of heat dissipation capacity and heat transfer resistance are derived from differential equations. Based on the method of equivalent radius, the similarities and differences between non-circular and circular roadways in calculating the heat dissipation of surrounding rock are discussed. Using the finite volume method, the calculation models for non-circular and circular roadways in the heat dissipation of surrounding rock are also established, among the non-circular roadways including three circumstances, namely, trapezoid, rectangle, and arch. The relation errors of heat dissipation of the surrounding rock of the three equivalent circular roadway methods are investigated for the three non-circular roadways. Results show that the calculation approach with equal perimeters is the best for the heat dissipation of surrounding rock of non-circular roadways.

Numerical Simulation of Rock Burst of Circular Roadway Based on RFPA Software

Based on RFPA software, the numerical simulation of rock burst in circular roadway is carried out under different horizontal stresses. The paper studies the distribution of stress field, the crack propagation and acoustic emission characteristics in the process of rock burst. The results show that the stress moves and the concentration of compressive stress appears on left and right sides of roadway after excavation of the roadway, and tensile stress zone appears at the top and bottom of the roadway. The shear fracture on the roadway’s left and right sides is more serious. The larger the horizontal stress is, the earlier the energy releases and the higher the total energy is.

Stability of Gas Drainage Borehole Analysis on Rock Mechanics Parameters with Roadway of Complex Stress

The pattern of stress redistribution in the effect of circular roadway is analyzed and numerical simulation on stability of gas drainage borehole which is in the area of the stress redistribution was done with FLAC3D. The model of that circular roadway and gas drainage borehole are perpendicularly crossed is established and compute with the Coulomb Mohr criterion. It can be found that the stress of gas drainage borehole decreases with decreasing of internal friction angle and the cohesion value. The stress of gas drainage borehole steep rises where the distances of away from roadway is two times of the diameter and the stress of horizontal direction are larger than the stress of vertical direction.

Sensitivity analysis in traffic microscopic simulation model for roundabouts

In the literature, many analytical techniques allow the study of the performance (capacity, queues, delays, etc) of roundabouts which are divided into two groups: analytical models and microscopic simulation models. Each method, when formulated, has to consider some aspects of roundabout circulation in comparison to others (geometric elements, vehicular flow and user behaviour). In particular, microscopic simulation models offer several advantages, compared to analytical ones (such as realistic modelling of vehicle arrivals and departures or the ability to study the spatial extent of queues), but they must be carefully calibrated. In this paper the authors introduce the results of a large survey conducted on an ample range of roundabout scenarios through the application of VISSIM simulation software. Each scenario describes a fixed roundabout phenomenon using geometric elements (inscribed circle radius, circular roadway, central and splitter islands etc.) and characteristics of the traffic flow (density, distribution, crossing and approach speeds, etc.) as variables. The results allow authors to evaluate the effects of these parameters on roundabout stop-line delays through a significance analysis.

Search costs decrease prices in a model of spatial competition

AbstractThis paper examines the Nash equilibrium prices of stores in a spatial search model. By assumption, a large store is certain to have the particular product a consumer wants, whereas a small store has it with probability w. Large and small stores alternate with each other on a circular roadway. Consumers must search by visiting stores. In the Nash price equilibrium, large stores charge higher prices than small stores. Perhaps surprisingly, all Nash equilibrium prices are lower than in the corresponding perfect‐information‐no‐search model (for a given value w). This last result is also demonstrated in a model with only small stores.

ZAM을 이용한 원형교차로 원인별 사고모형 개발

이 연구는 국내 원형교차로에서 발생한 교차로 사고를 다루고 있다. 연구의 목적은 ZAM을 이용하여 원인별 사고모형을 개발하는데 있다. 주요결과는 다음과 같다. 첫째, 교차로 운행방법 위반에서는 ZINB 모형이 적합한 것으로 분석되었다. 둘째, 안전거리 미확보에서도 ZINB 모형이 적합한 것으로 분석되었다. 마지막으로 공통변수로는 교통량과 회전차로 폭이 선정되었다. 교통량이 많을수록 그리고 회전차로 폭이 좁을수록 사고가 많이 발생하는 것으로 분석되었다. 특정변수로는 접근로수와 감속 시설수가 채택되었고, 접근로수가 증가할수록 그리고 감속시설수가 적을수록 사고가 증가하는 것으로 분석되었다. 이 연구는 원형교차로 사고연구에 기여할 것으로 기대된다. This study deals with the traffic accidents of circular intersections in Korea. The goal of this study is to develop the traffic accident models using ZAM. The main results are as follows. First, in the case of 'violating the operational method of intersection', ZINB(zero-inflatednegative binomial) models were analyzed to be the best fit to the data. Second, in the case of' no maintaining the safe distance', ZINB models were also analyzed to be the best fit to the data. Finally, such the common variables as traffic volume and width of circular roadway were selected as the independent variables. The more traffic volume and the less width of circulatory roadway were evaluated to make the more accidents. Such the specific variables as the number of approach lanes and speed reduction facilities were selected as the explanatory variables. The more approach lanes and the less speed reduction facilities were evaluated to give the more accidents. This study might be expected to give some implications to the accident research on the circular intersections.