Soft Rock Roadway Support Research Articles

Study on Support Technology of Truss Anchor Cable Beam in Deep Soft Rock Roadway Excavation

Aiming at the difficult problem of soft rock roadway support in deep mine, the support mode of "truss anchor beam" is proposed, and the support mode technology of truss anchor beam in deep soft rock roadway driving is studied by FLAC simulation software. Combined with the measured displacement of coal and rock around underground roadway under this support mode, it is concluded that the truss anchor beam support mode can introduce the high stress of shallow coal and rock around roadway into deep area, thus effectively controlling the deformation of coal and rock around roadway and ensuring safe and efficient production of mine.

Study on Mechanism and Control Technology of Asymmetric Floor Heave in a Deep Soft Rock Main Roadway

Considering the serious asymmetric deformation and failure of the floor of 1# main roadway in Wanglou Coal Mine, the mechanism of roadway asymmetric floor heave was studied through on-site investigation, theoretical analysis, numerical simulation, and on-site test. The following conclusions were drawn: (1) the floor heave of 1# main roadway is mainly caused by high original rock stress, surrounding rock stress, water physical effect, support strength, etc. (2) A mechanical model of asymmetric floor heave is built and analyzed. Roadway floor stability is relevant to the stress concentration coefficient of the roadway sides, the burial depth of the roadway, and the cohesion and internal angle of friction of the floor rock. The relationship between the upward resultant force of the floor and the stress concentration coefficient of the roadway sides is established. Affected by mining, the upward force of roadway floor reaches 17.0 MPa, and serious floor heave is easy to occur when the floor is opened. (3) The floor heave curve of the position of 1# main roadway corresponding to working face is obviously asymmetric, the maximum value of floor heave being 948 mm. The floor heave curve of other positions of 1# main roadway is basically symmetric, the maximum floor heave value being merely 497 mm. A new “differentiated” combined support is proposed and field tested. It has been 13 months since the completion of main roadway repair in this section, no obvious deformation occurred, and the long-term stability of soft rock roadway support in deep mines is realized.

Deformation Characteristics and Control Technology of Roadway in Water-Rich Soft Rock

Jurassic soft rocks are the main coal-bearing strata in western mining areas, which are rich in water and high in expansive minerals. The roof and floor of the coal seam are easily muddied and disintegrated when affected by water, and heave floor of roadway in soft rock has become one of the problems that restricts the safety and efficient production of coal mines in western mining areas. It is not ideal for the effect of the traditional roadway control theory on geological soft rock roadway support, and the deformation is difficult to control. Take the tailgate of 11506 working face of a coal mine in the western mining area as the research background. This surrounding rock conditions and the deformation characteristics of the roadway in tailgate of 11506 working face were analyzed systematically, and the optimization design of the support scheme of the water-rich soft rock roadway was carried out by using theoretical analysis and numerical simulation. The application of the support in the tailgate of 11506 working face was carried out. The results show that slip of the two sidewalls, support failure, stress concentration, and floor heave were failure characteristics in water-rich soft rock roadway. The optimization of the roadway section, thin guniting of the roadway surface, optimization of support components, and gradient support could effectively achieve the control of soft rock roadway deformation. The maximum floor heave during the roadway deformation monitoring period was 230 mm, which decreased about 75% compared with original support. The influence range of the advance abutment stress is 0~60 m, of which 0~30 m is the serious influence area. The research results have good engineering practice significance for the control of bottom bulge of the soft rock roadway in this coal mine and western mining area.

Study on bearing capacity characteristics of steel structure support in soft rock roadway

AbstractWhen the soft rock roadway in underground mine is supported by steel frame, the bearing capacity of steel structure is the key to the success of roadway support. Taking the soft rock roadway support in Mengnuo lead‐zinc mine as an example, this paper studies the displacement and stress change law of U‐shaped steel, I‐shaped steel, rail steel, and surrounding rock, analyzes the bearing capacity characteristics of steel structure support, and conducts field application tests. The results show that: (a) the deformation resistance of U‐shaped steel is the best, the overall deformation of which is 85.0% of that of track steel, followed by that of I‐shaped steel, which is 92% of that of track steel, and the deformation resistance of track steel is the weakest in comparison; (b) the main stress positions of the three kinds of supporting steel structures are the joint of the support shoulder and the waist. When simulating the support of 10 m roadway, the deformation of the middle 4‐6 m roadway is larger than that of the surrounding rock of the head and tail roadway; (c) when the horizontal stress of the deep soft rock roadway is larger, the floor heave of the roadway is larger than that of the shallow roadway only when the side and top support are used; (d) by the analysis of three different forms and stress states of support steel structures, it is found that the shape of support has a great impact on the bearing mechanical characteristics. It is of great value to study the shape of support with more bearing advantages under the same amount of steel.

A Case Study of Optimization and Application of Soft-Rock Roadway Support in Xiaokang Coal Mine, China

The roadway of S2S2 fully mechanized caving face (FMCF) in Xiaokang Coal Mine is one of the most typical deep-buried soft-rock roadways in China and had been repaired several times. In order to figure out the failure reasons of the original roadway support, the geological conditions were investigated, the surrounding rock stress was monitored, the rib displacement, roof separation, and floor heave were in situ measured, and the performance of the U-shaped steel support was simulated. The above analysis results indicated that the support failure was mainly caused by (1) the unreasonable arch roadway section, (2) the high and complex surrounding rock stress, (3) the failure control of the floor heave, and (4) the inadequate self-supporting capacity of the surrounding rock. For optimizing, the roadway section was changed to circle and a new full-section combined support system of “belt-cable-mesh-shotcrete and U-shaped steel-filling behind the support” was adopted, which could specifically control the floor heave, allow the roadway deformation in control, and improve the self-supporting ability and stress field of the surrounding rock. To determine the support parameters, the selected U-shaped steel support was verified by simulation, and various bolt-cable support schemes were simulated and compared. Finally, such an optimized support scheme was applied in the roadway of the next replacement FMCF. The in situ monitoring showed that the rib-to-rib convergence and roof-to-floor convergence were both controlled within 600 mm, which indicated that the roadway was effectively controlled. This case study has important reference value and guiding function for the optimal design of the soft-rock roadway support with similar geological conditions.

Numerical Analysis and Control Study on Surrounding Rock Deformation of Deep Soft Rock Roadway

Aiming at the problem of large-scale deformation of the track and alleys in the East Second Mining Area, the numerical analysis method is used to analyze the stress and deformation law of the roadway. The results show that the critical depth of the roadway deformation is 800m, the shear stress of the deep roadway is about 8.7MPa in the left and right shoulders, and the vertical stress increases sharply in the range of 0~5.5m from the center of the roadway, and is 6~ from the center of the roadway. The peak value is reached within 8m, the plastic zone of the roadway roof is 2.6m, the left and right plastic zones are 5.2m and 5.4m, respectively, and the plastic zone of the floor is 6.1m. This result can provide a basis for the design parameters of deep soft rock roadway support. The engineering practice proves that the support design effectively controls the strong deformation of the roadway and achieves better support effect.

Instability Mechanism and Key Control Technology of Deep Soft Rock Roadway under Long‐Term Water Immersion

More and more attention has been paid to the supporting problem of deep soft rock roadway floor with long‐term water immersion in recent years. However, the existing soft rock roadway support technology rarely takes into account the influence of the immersion softening phenomenon of the roadway floor and the self‐supporting structure characteristics of the surrounding rock on the stability of the surrounding rock at the same time, and the influence of the creep characteristics of rock on the deformation zone of the surrounding rock requires further research on the nature and division of the self‐supporting structure of the surrounding rock. In response to the issues mentioned, based on the loading and unloading properties of the surrounding rock of the soft rock roadway, a new concept of the internal and external self‐bearing structure was proposed. The fact of water‐immersed mudstone softening in the soft rock roadway floor was revealed through the field practice, and the shape of the internal and external bearing structure was determined based on the in situ monitoring results. Then, the instability mechanism of the internal and external self‐bearing structure of the surrounding rock was analyzed, the position of the critical control point was calculated, and the key control technology based on the method of controlling floor heave by using double‐row anchor cables to control the deformation of the roadway sides was put forward. Finally, the field industrial test showed that this support technology can effectively control the deformation and failure of soft rock roadway in the case of water immersion on the floor. This work can provide a technical reference for similar roadway support designs.

Discussion on support technology of coal mine soft rock roadway

China is rich in coal resources. In most cases, coal resources are obtained through the way of mining. In the process of mining, it is necessary to control the application of mining technology, otherwise it will easily cause damage to the geological structure. With the increasing demand of social resources in recent years, shallow mining has been unable to meet the needs of the society, while deep mining is facing the problem of soft rock layer, which can not guarantee the stability and safety. Based on this, this paper will focus on the coal mine soft rock roadway support technology.

Coupling Instability Mechanism and Joint Control Technology of Soft-Rock Roadway with a Buried Depth of 1336 m

Based on the geological conditions of soft-rock roadway with a buried depth of 1336 m and the data that are achieved by various experimental methods, the multi-factor coupling analysis of the instability mechanism of soft-rock roadway is carried out through theoretical analysis and numerical simulation. Additionally, following the Nishihara model and Drucker–Prague’s modification of Mohr–Coulomb yield condition, the stability control theory of soft-rock coal roadway is analyzed. By fully considering the bearing capacity of each supporting component, the original supporting structure is innovatively examined with crush tube, spherical tray, high-strength bar and steel strip to form a flexible and high-performance bolt supporting structure, and the stability control of 1336 m soft-rock coal roadway is also comprehended. Therefore, the studies have shown that the convergence trend of omnidirectional, strong rheological and large deformation constitutes the essential characteristics of deep soft-rock roadway deformation. The instability process of roadway surrounding rock is accompanied by “domino-effect” similar to that of multi-factor coupling. The irrational design of the support scheme and the destruction of the support structure are the external factors of this effect, although the prominent contradiction between high in-situ stress and the weak bearing capacity of the deep degraded rock mass is the internal factors of this effect. Similarly, the engineering practice and observation data of the new scheme have shown that the deformation coordination of support components and the matching degree of bearing characteristics should be one of the main factors to be considered in the design of deep soft-rock roadway support, high elongation and multiple adjustable characteristics to adapt to the basic characteristics of deep soft-rock roadway deformation. Hence, the construction idea of the new scheme has contributed the satisfactory engineering significances and reference value for optimizing the stress environment of soft-rock roadway and further reducing the support cost.

Comparative study on bearing mechanism and design parameters of confined concrete arch joints in deep soft rock roadway

Square confined concrete arch is increasingly used in deep soft rock roadway support because of its advantages of high strength and construction convenience. However, the design of confined concrete arch in underground engineering still remains in experience-based method and lacks quantitative analysis. As a connecting component between arch sections, the connection joints have an important influence on the internal force distribution and failure mechanism of support arch. Therefore, a reasonable design of arch joints is the premise of rational support design. Taking Liangjia Coal Mine, a typical deep soft rock mine in China, as research background, this paper fully compared the most widely used joint types of confined concrete arch as analytical objects: flange joints and casing joints. The main failure modes of these two kinds of joints under bending moment are defined. Laboratory and numerical tests are carried out to study the mechanical characteristics of joints. Based on the M–θ curve, the influence law of different design parameters is analyzed, and the design principles of joints are proposed. The research results could provide a theoretical basis for the design and application of confined concrete arch in related projects.

Static tension test and the finite element analysis of constant resistance and large deformation anchor cable

Compared to the traditional anchor cable, the constant resistance and large deformation anchor cable (constant resistance and large deformation anchor cable) has good applications in many fields of geotechnical engineering. Through the indoor static tension test, this study reveals the variation law of constant resistance, axial strain, the outer diameter of the sleeve, and the thermal effect of constant resistance and large deformation anchor cables during static tension. The ANSYS software was used for the first time to establish the nonlinear thermomechanical coupling analysis model of the finite element structure of constant resistance and large deformation anchor cables for the numerical calculation and analysis of static tension mechanical properties of constant resistance anchor cables. The experimental results that the average elongation of this batch of constant resistance anchor cables is 905 mm with an average elongation rate of 45.2% and an average constant resistance of 650 kN prove that constant resistance anchor cables are characterized by good constant resistance and large deformation, which can meet the requirements of deep soft rock roadway support and advanced landslide monitoring. The numerical simulation results show that the elongation of this type of anchor cables is 902 mm with an elongation rate of 45.1% and a constant resistance of 660 kN, which are basically consistent with the experimental results, indicating that numerical simulation is relatively accurate for testing the mechanical property of constant resistance and large deformation anchor cables, and the combination of the indoor test and numerical simulation provides the reference for engineering practice and design optimization of constant resistance and large deformation anchor cables.

Study on Surrounding Rock Deformation Failure Law and Soft Rock Roadway Support with Thick Composite Roof

Study on Surrounding Rock Deformation Failure Law and Soft Rock Roadway Support with Thick Composite Roof

Influence of dynamic pressure on deep underground soft rock roadway support and its application

Due to high ground stress and mining disturbance, the deformation and failure of deep soft rock roadway is serious, and invalidation of the anchor net-anchor cable supporting structure occurs. The failure characteristics of roadways revealed with the help of the ground pressure monitoring. Theoretical analysis was adopted to analyze the influence of mining disturbance on stress distribution in surrounding rock, and the change of stress was also calculated. Considering the change of stress in surrounding rock of bottom extraction roadway, the displacement, plastic zone and distribution law of principal stress difference under different support schemes were studied by means of FLAC3D. The supporting scheme of U-shaped steel was proposed for bottom extraction roadway that underwent mining disturbance. We carried out a similarity model test to verify the effect of support in dynamic pressure. Monitoring results demonstrated the change rules of deformation and stress of surrounding rock in different supporting schemes. The supporting scheme of U-shaped steel had an effective control on deformation of surrounding rock. The scheme was successfully applied in underground engineering practice, and achieved good technical and economic benefits.

Research to Enhance the Supporting Stiffness of Different U-Type Sheds

With the increase of the mining depth, the surrounding rock of roadways shows the characteristics of soft rock that the stress increase, poor rock cementation, broken loose, a significant expansion, creep deformation, etc. Deep roadways mainly use the combination of active and passive supporting method, U-type shed is widely used in the roadway support and becomes gradually the main supporting form. This paper studies mechanical properties of different arched U- type sheds, then compares the stress distribution and the displacement change. According to the result of simulation and optimization, it is seen that the deformation trend is regular with the angle change, and when θ=30°, the U- type shed is better in the roadway support. The conclusion can provide some theoretical guidance for the deep or soft rock roadway support.

Numerical Simulation Research on Deep Soft Rock Roadway

The soft rock roadway support is one of difficult problems in the mineral engineering. For making the stress and strains of support system to be effective forecasted in the process of roadway support. The Adina finite element software is used to do numerical simulation about the strains of the supports system in the process of the Hama mountain roadway, and compare with the date which was got from the field monitoring. The date comparison shows that the results of simulation is basic anastomotic with the examination at present. So that it can be well predicted the effectiveness of the support measure when using the finite element simulation software –Adina.

Research and Exploration on Combined Support Technology in Deep Soft-Rock Roadway

Because of the existence of high stress in the surrounding rock of deep roadway, the physical and mechanical properties of the surrounding rock to change, and the surrounding rock stress distribution is very different from the shallow, so the way of shallow roadway support is not suitable for deep roadway. Deep soft-rock roadway support is a complex systems engineering, it should consider the different geological conditions, roadway scope of application, construction technology conditions, construction period and the cost and other factors to determine the optimal combined support program, if the special geological conditions encountered in the construction, it should be timely to improve the supporting program to meet the construction safety and ensure the quality. This paper is based on the characteristics of deep roadway support, sums up the combined support form in the project, researches and analyzes the combined support technology, and explores how to use suitable combined support form in deep roadway.