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.     

Deformation mechanism and excavation process of large span intersection within deep soft rock roadway

The FLAC3D software was used to simulate and analyze numerically the displacement, stress and plastic zone distribution characteristics of a large span intersection in a deep soft rock roadway after the surrounding rock was excavated. Our simulation results show that there are two kinds of dominating factors affecting roadway stability at points of intersection, one is the angle between horizontal stress and axial direction of the roadway and the other are the angles at the points of intersection. These results are based on a study we carried out as follows: first, we analyzed the failure mechanism of a large span intersection and then we built a mechanical model of a rock pillar at one of the points of intersection. At the end of this analysis, we obtained the failure characteristics of the critical parts on the large span intersection. Given these failure characteristics, we proposed a new supporting method, i.e., a Double-Bolt Control Technology (DBCT). By way of numerical simulation, DBCT can effectively control the deformation of the surrounding rock at the points of intersection in roadways.     

深部巷道围岩变形试验与数值模拟研究

为了研究深部软岩巷道的变形破坏特性,以淮南矿区某煤矿13-1煤回采巷道为例,在现场调查回采巷道工程概况的基础上,开展了室内深部回采巷道围岩变形特性相似模拟试验,并基于块体离散元法,建立了深部回采巷道围岩的数值模型,模拟了开挖过程中围岩的变形特性。相似模拟试验和数值模拟试验结果表明,深部巷道围岩的典型特征为:巷道底臌量两帮移近量顶板下沉量,巷道不同围岩受开挖扰动的位移影响范围不同,底板为3.5 m,顶板为2.45 m,两帮为5.5 m。     

Bolt-grouting combined support technology in deep soft rock roadway

Analyzing the mineral composition, mechanical properties and ground stress testing in surrounding rock,the study investigated the failure mechanism of deep soft rock roadway with high stress. The boltgrouting combined support system was proposed to prevent such failures. By means of FLAC3D numerical simulation and similar material simulation, the feasibility of the support design and the effectiveness of support parameters were discussed. According to the monitoring the surface and deep displacement in surrounding rock as well as bolt axial load, this paper analyzed the deformation of surrounding rock and the stress condition of the support structure. The monitor results were used to optimize the proposed support scheme. The results of field monitors demonstrate that the bolt-grouting combined support technology could improve the surround rock strength and bearing capacity of support structure, which controlled the great deformation failure and rheological property effectively in deep soft rock roadway with high stress. As a result, the long term stability and safety are guaranteed.     

Deformation and failure characteristics of anchorage structure of surrounding rock in deep roadway

This paper investigated the stress evolution, displacement field, local deformation and its overall distribution, and failure characteristics of the anchorage structure of surrounding rock with different rockbolt spacing through the model experiments. The influences of the pre-tightening force and spacing of rockbolt on the support strength of the anchorage structure of surrounding rock were analyzed by the simulation using FLAC3D numerical software. The support scheme of the excavated roadway was then designed, and the effectiveness of this support scheme was further verified by the displacement measurement of the roadway. The results showed that the maximum displacement between the roof and floor of the west wing track roadway in Kouzidong coal mine, China is about 42 mm, and the maximum displacement between its both sides is about 72 mm, indicating that the support scheme proposed in this study can ensure the stability and safety of the excavated roadway.     

Permeability and pressure distribution characteristics of the roadway surrounding rock in the damaged zone of an excavation

Research on the permeability and pressure distribution characteristics of the roadway surrounding rock in the excavation damaged zone(EDZ) is beneficial for the development of gas control technology. In this study, analytical solutions of stress and strain of the roadway surrounding rock were obtained, in which the creep deformation and strain softening were considered. Using the MTS815 rock mechanics testing system and a gas permeability testing system, permeability tests were conducted in the complete stress-strain process, and the evolution characteristics of permeability and strain were studied over the whole loading process. Based on the analytical solutions of stress and strain and the governing equation of gas seepage flow, this paper proposes a hydro-mechanical(HM) model, which considers three different zones around the roadway. Then the gas flow process in the roadway surrounding rock in three different zones was simulated according to the engineering geological conditions, thus obtaining the permeability and pressure distribution characteristics of the roadway surrounding rock in three different zones. These results show that the surrounding rock around the roadway can be divided into four regions-the full flow zone(FFZ), flow-shielding zone(FSZ), transitive flow zone(TFZ), and in-situ rock flow zone(IRFZ). These results could provide theoretical guidance for the improvement of gas extraction and gas control technology.     

高应力回采巷道围岩破裂机理及危险性评价

用弹塑性力学中的复变函数方法求解了巷道围岩的应力函数,研究了高应力回采巷道围岩破裂机理,提出了用危险函数来评价巷道围岩破裂的危险性和确定滑移面分布特征的方法.结果表明:对一定特定内摩擦角(φ0)的巷道围岩,只有当q/C≥4.1156e0.0606φ0时,巷道围岩才会出现破裂区.当15°≤φ0≤23°时,围岩裂隙向巷道表面及深部两侧方向扩展而形成一定范围的破裂区;当23°<φ0≤60°时,围岩承载能力升高,围岩裂隙由巷道表面向巷道深部方向扩展.在工程实践中,此方法有效控制了围岩的变形.     

Deformation characteristics of surrounding rock of broken and soft rock roadway

A similar material model and a numerical simulation were constructed and are described herein. The deformation and failure of surrounding rock of broken and soft roadway are studied by using these models. The deformation of the roof and floor, the relative deformation of the two sides and the deformation of the deep surrounding rock are predicted using the model. Measurements in a working mine are compared to the results of the models. The results show that the surrounding rock shows clear rheological features under high stress conditions. Deformation is unequally distributed across the whole section. The surrounding rock exhibited three deformation stages: displacement caused by stress concentration, rheological displacement after the digging effects had stabilized and displacement caused by supporting pressure of the roadway. Floor heave was serious, accounting for 65% of the total deformation of the roof and floor. Floor heave is the main reason for failure of the surrounding rock. The reasons for deformation of the surrounding rock are discussed based on the similar material and numerical simulations.     

Effect of a single weak lithological structure on the height of a collapsing roof in a deep soft rock roadway

Besides the cross sections of roadways and the tendency and obliquity of roadway axes, the major controlling factors affecting the height of a collapsing roof include the weak lithological structure of surrounding rocks. This thesis analyzes the effect of two single and weak lithological structures of both sides and the roof on the height of a collapsing roof in a deep soft rock road-way. Using the two-dimensional UDEC3.1 software, a numerical simulation was carried out on the models of weak lithological structures of both sides of a roadway and of two weak lithological structures of roof of different depths. We reconstruct the overall processes from a break-away layer, bending, subsidence and the cracking of a collapsing roof. We also illustrate the distribution characteristics of displacement fields in the surrounding rock after the roof collapse in a deep soft rock roadway. The results of our numerical simulations indicate that the form of a roof collapse is side-expanding when the roadway is a weak structure at both sides. The height of the roof collapse is related to the lithological combination of the roof when the roadway is a weak structure of the roof.     

Roadway deformation during riding mining in soft rock

“Riding mining” is a form of mining where the working face is located above the roadway and advances parallel to it. Riding mining in deep soft rock creates a particular set of problems in the roadway that include high stresses, large deformations, and support difficulties. Herein we describe a study of the rock deformation mechanism of a roadway as observed during riding mining in deep soft rock. Theoretical analysis, numerical simulations, and on site monitoring were used to examine this problem. The stress in the rock and the visco-elastic behavior of the rock are considered. Real time data, recorded over a period of 240 days, were taken from a 750 transportation roadway. Stress distributions in the rock surrounding the roadway were studied by comparing simulations to observations from the mine. The rock stress shows dynamic behavior as the working face advances. The pressure increases and then drops after peaking as the face advances. Both elastic and plastic deformation of the surrounding rock occurs. Plastic deformation provides a mechanism by which stress in the rock relaxes due to material flow. A way to rehabilitate the roadway is suggested that will help ensure mine safety.     

Time-dependent safety of lining structures of circular tunnels in weak rock strataOA

Following tunnel excavation and lining completion, fractured surrounding rock deforms gradually over time; this results in a time-dependent evolution of the pressure applied to the lining structure by the surrounding rock. Thus, the safety of the tunnel lining in weak strata is strongly correlated with time. In this study, we developed an analytical method for determining the time-dependent pressure in the surrounding rock and lining structure of a circular tunnel under a hydrostatic stress fiel...     

基于强度折减法随机裂隙岩体结构稳定性分析

克服裂隙岩体确定性分析方法的局限性,采用有限元强度折减法对节理裂隙随机分布的重力坝安全稳定性进行评价。运用Monte-Carlo方法,生成二维和三维随机节理裂隙网络模型,模型较为真实的还原了节理裂隙的分布情况;针对重力坝只含软弱夹层和同时含软弱夹层和节理裂隙两种情况,采用强度折减法对比分析其塑性区和水平位移变化情况。研究结果表明,含节理裂隙的重力坝坝基内部塑性区较多,且局部破坏严重,坝体的水平位移相对较大。该结果可为裂隙岩体地下工程的安全和稳定性研究提供参考。     

深部软岩巷道合理喷层厚度确定

为分析深部软岩巷道锚喷支护合理喷层厚度,以淮南矿区具有典型特征某深部采区软岩巷道为例,采用FLAC3D软件,建立了合理应变软化数值计算模型,基于数值模拟方法分析不同喷层厚度围岩塑性范围及位移场分布,在此基础上进一步分析不同巷道埋深喷层厚度对围岩松动破碎影响。结果表明:深部巷道喷层对围岩塑性圈范围及松动破碎都有显著控制作用。针对淮南矿区典型深部巷道,合理喷层厚度应为200 mm。     

Zonal disintegration phenomenon in rock mass surrounding deep tunnels

Zonal disintegration is a typical static phenomenon of deep rock masses. It has been defined as alternating regions of fractured and relatively intact rock mass that appear around or in front of the working stope during excavation of a deep tunnel. Zonal disintegration phenomenon was successfully demonstrated in the laboratory with 3D tests on analogous gypsum models, two circular cracked zones were observed in the test. The linear Mohr-Coulomb yield criterion was used with a constitutive model that showed linear softening and ideal residual plastic to analyze the elasto-plastic field of the enclosing rock mass around a deep tunnel. The results show that tunneling causes a maximum stress zone to appear between an elastic and plastic zone in the surrounding rock. The zonal disintegration phenomenon is analyzed by considering the stress-strain state of the rock mass in the vicinity of the maximum stress zone. Creep instability failure of the rock due to the development of the plastic zone, and transfer of the maximum stress zone into the rock mass, are the cause of zonal disintegration. An analytical criterion for the critical depth at which zonal disintegration can occur is derived. This depth depends mainly on the character and stress concentration coefficient of the rock mass.     

膨胀特性对软岩巷道围岩变形规律的影响研究

针对软岩巷道的特点,利用泥灰岩三轴试验结果,分析了膨胀特性对深井软岩巷道围岩稳定性的影响;利用最新的弹塑性理论研究成果,推导出了膨胀角与围岩变形的直接关系式;采用数值力学的研究方法,分析了软岩巷道周围体积膨胀与扩容现象.数值模拟结果表明:软岩巷道表面变形和巷道周边体积应变随膨胀角的变化均成非线性递增,膨胀角愈大,软岩巷道的围岩条件愈差,巷道周边围压越大,所需要的支护力就越大,这些重要结论为深井条件下软岩巷道工程提供参考.     

膨胀特性对软岩巷道围岩变形规律的影响研究

针对软岩巷道的特点，利用泥灰岩三轴试验结果，分析了膨胀特性对深井软岩巷道围岩稳定性的影响；利用最新的弹塑性理论研究成果。推导出了膨胀角与围岩变形的直接关系式；采用数值力学的研究方法，分析了软岩巷道周围体积膨胀与扩容现象．数值模拟结果表明：软岩巷道表面变形和巷道周边体积应变随膨胀角的变化均成非线性递增，膨胀角愈大，软岩巷道的围岩条件愈差，巷道周边围压越大，所需要的支护力就越大。这些重要结论为深井条件下软岩巷道工程提供参考．     

Similar simulation study on the deformation and failure of surrounding rock of a large section chamber group under dynamic loading

Large and super-large section chamber groups in coal mines are frequently affected by dynamic loads resulting from production activities such as roadway driving and blasting. The stability of the surrounding rock is poor, and it is difficult to control. In this paper, a similar simulation test was used to study the deformation and evolution laws of the surrounding rock of a triangle-shaped chamber group under different dynamic loads. The results showed that under dynamic loading, the vertical stress of the surrounding rock of the chamber group increased in an oscillatory form. The maximum stress concentration coefficient reached 4.09. The damage degree of the roof was greater than that of the two sides. The deformation of the roof was approximately 1.2 times that of the two sides. For the chamber closer to the power source, the stress oscillation amplitude of the surrounding rock was larger, and the failure was more serious. The force of the anchorage structure showed a phased increasing characteristic; additionally, the force of the anchorage structure on the adjacent side of the chambers was greater than that on the other side. This study reveals the deformation and failure evolution laws of the surrounding rock of large section chamber groups under dynamic loading.     

Deformation control of asymmetric floor heave in a deep rock roadway: A case study

In order to control asymmetric floor heave in deep rock roadways and deformation around the surrounding rock mass after excavation, in this paper we discuss the failure mechanism and coupling control countermeasures using the finite difference method (FLAC^3D) combined with comparative analysis and typical engineering application at Xingcun coal mine. It is indicated by the analysis that the simple symmetric support systems used in the past led to destruction of the deep rock roadway from the key zone and resulted in the deformation of asymmetric floor heave in the roadway. Suitable reinforced support countermeasures are proposed to reduce the deformation of the floor heave and the potential risk during mining. The application shows that the present support technology can be used to better environmental conditions. The countermeasures of asymmetric coupling support can not only effectively reduce the discrepancy deformation at the key area of the surrounding rock mass, but also effectively control floor heave, which helps realize the integration of support and maintain the stability of the deep rock roadways at Xingcun coal mine.     

Failure mechanism and control technology of water-immersed roadway in high-stress and soft rock in a deep mine

Aiming at soft rock ground support issues under conditions of high stress and long-term water immersion, the ground failure mechanism is revealed by taking the deep-water sumps of Jiulong Mine as the engineering background and employing field investigation, tests of rock structure, mechanical properties and mineral composition. The main factors leading to the surrounding rock failure include the high and complex stress state of the water sumps, high-clay content and water-weakened rock, and the unreasonable support design. In this paper, the broken and fractured rock mass near roadway opening is considered as ground small-structure, and deep stable rock mass as ground large-structure. A support technology focusing on cutting off the water, strengthening the small structure of the rock and transferring the large structure of the rock is proposed. The proposed support technology of interconnecting the large and small structures, based on high-strength bolts, high-stiffness shotcrete layer plugging water,strengthening the small structure with deep-hole grouting and shallow-hole grouting, highpretensioned cables tensioned twice to make the large and small structures bearing the pressure evenly,channel-steel and high-pretensioned cables are used to control floor heave. The numerical simulation and field test show that this support system can control the rock deformation of the water sumps and provide technical support to similar roadway support designs.     

移动压力支承作用下底板巷道围岩变形与采深的关系

本文阐明了移动支承压力影响区与采深的关系，提出了用有效载荷系数来反映动压作用下底板巷道围岩变形量的大小，结合孙村煤矿实测资料，总结出在跨采期间，底板巷道围岩变形量与有效载荷系数之间的定量关系，为深井开采移动支承压力作用下，底板巷道围岩变形量预测预报提供了一种方法。