层次分析法确定影响地下洞室围岩稳定性各因素的权值

在研究大型地下洞室围岩稳定性时,综合考虑了围岩强度和刚度、洞室高度和埋深、水平向地应力及其相互间距等影响因素,采用FLAC3D软件进行了16个工况的数值模拟计算,建立了影响地下洞室稳定性的层次分析法模型,对影响稳定性的各个指标因素进行判断矩阵的构造、特征向量的求解以及一致性的检验。这种分析方法可以从总体上对各因素进行排序,为将来预测地下洞室围岩稳定性提供必要的依据。

轨道交通深通风竖井围岩变形应力特征研究

依托重庆轨道交通某通风竖井施工过程,建立竖井开挖支护的过程的三维有限元分析模型,分析竖井开挖支护过程中围岩变形及应力特征。研究结果表明,竖井长边跨中水平位移、地表沉降明显大于短边跨中,围压最大、最小主应力皆在容许范围之内,且为压应力,最大剪应力出现在竖井底部边缘位置,大于围压的抗剪强度,施工过程中应加强支护。受竖井围岩侧压力变化特征的影响,在竖井深度60~70m范围围岩位移发生“S”形反弯。

里蔡隧道破碎围岩施工安全控制措施研究

针对隧道施工中最常见的坍塌事故,以里蔡隧道为例,深入探讨了如何更有效地保证隧道破碎围岩的施工质量和安全。通过里蔡和茶园里隧道进行了节理发育特征的精细化描述,利用室内模型试验、数值模拟试验和现场监测结果的相互验证,揭示了节理组数、产状、间距等特征对隧道变形的影响程度,提出了适用于隧道破碎围岩施工安全的预警系统和安全控制措施,开发了隧道破碎围岩安全施工动态预警软件并取得很好的效果。

深部岩体非线性蠕变规律研究

对深部工程中不同深度的巷道围岩在高地应力作用下的蠕变破坏过程进行了数值模拟,得到了时间-蠕变、水平地应力-蠕变曲线组和时间-水平地应力-蠕变三维曲面。应用 Mohr-Coulomb 和 Griffith 破坏准则,获得了高地应力岩体的蠕变破坏规律,并计算验证了郑榕明和孙钧提出的非线性流变理论。

温州绕城高速太平山1#隧道上方500kV高压线铁塔稳定性研究

本文利用FLAC3D软件,对太平山1#隧道开挖过程中,其上方500 k V高压线铁塔的稳定性进行了计算机模拟计算分析。重点分析公路隧道施工过程中的铁塔附近的围岩变形,得到了施工过程中围岩位移规律,分析电塔在施工过程中的稳定性。

Numerical analysis of deformation and failure characteristics of deep roadway surrounding rock under static-dynamic coupling stress

In actual production,deep coal mine roadways are often under typical static-dynamic coupling stress(SDCS)conditions with high ground stress and strong dynamic disturbances.With the increasing number of disasters and accidents induced by SDCS conditions,the safe and efficient production of coal mines is seriously threatened.Therefore,it is of great practical significance to study the deformation and failure characteristics of the roadway surrounding rock under SDCS.In this paper,the effects of different in-situ stress fields and dynamic load conditions on the surrounding rock are studied by numerical simulations,and the deformation and failure characteristics are obtained.According to the simulation results,the horizontal stress,vertical stress and dynamic disturbance have a positive correlation with the plastic failure of the surrounding rock.Among these factors,the influence of the dynamic disturbance is the most substantial.Under the same stress conditions,the extents of deformation and plastic failure of the roof and ribs are always greater than those of the floor.The effect of horizontal stresses on the roadway deformation is more notable than that of vertical stresses.The results indicate that for the roadway under high-stress conditions,the in-situ stress test must be strengthened first.After determining the magnitude of the in-situ stress,the location of the roadway should be reasonably arranged in the design to optimize the mining sequence.For roadways that are strongly disturbed by dynamic loads,rock supports(rebar/cable bolts,steel set etc.)that are capable of maintaining their effectiveness without failure after certain dynamic loads are required.The results of this study contribute to understanding the characteristics of the roadway deformation and failure under SDCS,and can be used to provide a basis for the support design and optimization under similar geological and geotechnical circumstances.

Numerical simulation on deformation character of surrounding rock masses of Changjiashan tunnel through the gob of coalmine

Based on the construction project of the Changjiashan tunnel of the freeway,the variety rule of surrounding rock masses of the tunnel through the gob of coalmine wasstudied by using of finite element methed(FEM).The status of the stress and strain,thevariety of the plastic area were simulated in the whole rock mass before and after thetunnel was excavated.The characters of stress and deformation of surrounding rockmasses were analyzed when the tunnel was built.It concluded from the numerical simula-tion that the influence on the tunneling is great when the tunnel passing through the gob ofcoalmine is excavated,and the relative measures should be taken.

Numerical simulation study of the failure evolution process and failure mode of surrounding rock in deep soft rock roadways

Based on the safety coefficient method,which assigns rock failure criteria to calculate the rock mass unit,the safety coefficient contour of surrounding rock is plotted to judge the distribution form of the fractured zone in the roadway.This will provide the basis numerical simulation to calculate the surrounding rock fractured zone in a roadway.Using the single factor and multi-factor orthogonal test method,the evolution law of roadway surrounding rock displacements,plastic zone and stress distribution under different conditions is studied.It reveals the roadway surrounding rock burst evolution process,and obtains five kinds of failure modes in deep soft rock roadway.Using the fuzzy mathematics clustering analysis method,the deep soft surrounding rock failure model in Zhujixi mine can be classified and patterns recognized.Compared to the identification results and the results detected by geological radar of surrounding rock loose circle,the reliability of the results of the pattern recognition is verified and lays the foundations for the support design of deep soft rock roadways.

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 theological 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, theological 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.

Numerical Simulation for Roadways in Swelling Rock Under Coupling Function of Water and Ground Pressure

According to the analogical relation in the governing differential equations of the humidity stress field theory and the temperature stress field theory, the problem of solving the humidity stress field was transformed into that of solving the temperature stress field by the change of parameters. As a result, the problem of roadways in swelling rock under the coupling function of water and ground pressure can be solved by the analytical module of temperature stress field in software ANSYS. In the numerical simulation mentioned above, three kinds of supporting, i.e. steel support, bolting support and non support, were taken into account, the pressure distribution and deformation state of roadways with a swelling rock floor under the coupling function of water and ground pressure were analyzed and compared with those in the action of only ground pressure. The research results provides a scientific basis for the deformation control of roadways in swelling rock.

Interaction between anti-shear galleries and surrounding rock in the right-bank slope of Dagangshan hydropower station

The fight-bank slope of the Dagangshan hydropower station located in Southwest China is a highly unloaded rock slope. Moreover, large-scale natural faults were detected in the slope body; some excavation-induced unloading fractures were discovered at elevations between lo75m and 1146m. Because of poor tectonic stability, the excavation work was suspended in September 2009, and six large- scale anti-shear galleries were employed to replace the weak zone in the slope body to reinforce the fight- bank slope. In this study, based on microseismic- monitoring technology and a numerical-simulation method, the stabilities of the slope with and without the reinforcement are analysed. An in-situ microseismic-monitofing system is used to obtain quantitative information about the damage location, extent, energy, and magnitude of the rocks. Thus, any potential sliding block in the fight-bank slope can be identified. By incorporating the numerical results along with the microseismic-monitoring data, the stress concentration is found to largely occur aroundthe anti-shear galleries, and the seismic deformation near the anti-shear galleries is apparent, particularly at elevations of 121o, 118o, 115o, and 112om. To understand the interaction mechanism between the anti-shear gallery and the surrounding rock, a 2D simulation of the potential damage process occurring in an anti-shear gallery is performed. The numerical simulation helps in obtaining additional information about the stress distribution and failure-induced stress re-distribution in the vicinity of the anti-shear galleries that cannot be directly observed in the field. Finally, the potential sliding surface of the right-bank slope is numerically obtained, which generally agrees with the spatial distribution of the in-situ monitored microseismic events. The safety factor of the slope reinforced with the anti-shear gallery increases by approximately 36.2%. Both the numerical results and microseismic data show that the anti-shear galleries have a good reinforcement effect.

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 structures of both sides of a roadway and of two weak lithological simulation was carried out on the models of 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.

Mechanical response features and failure process of soft surrounding rock around deeply buried three-centered arch tunnel

Due to the extreme complexity of mechanical response of soft surrounding rock(SR) around a tunnel under high geostatic stress conditions, the integration of physical and numerical modeling techniques was adopted. Based on the similarity theory, new composite-similar material was developed, which showed good agreement with the similarity relation and successfully simulated physico-mechanical properties(PMP) of deep buried soft rock. And the 800 mm×800 mm×200 mm physical model(PM) was conducted, in which the endoscopic camera technique was adopted to track the entire process of failure of the model all the time. The experimental results indicate that the deformation of SR around a underground cavern possessed the characteristics of development by stages and in delay, and the initial damage of SR could induce rapid failure in the later stage, and the whole process could be divided into three stages, including the localized extension of crack(the horizontal load(HL) was in the range of 130 k N to 170 k N, the vertical load(VL) was in the range of 119 k N to 153.8 k N), rapid crack coalescence(the HL was in the range of 170 k N to 210 k N, the VL was in the range of 153.8 k N to 182.5 k N) and residual strength(the HL was greater than 210 k N, the VL was greater than 182.5 k N). Under the high stress conditions, the phenomenon of deformation localization in the SR became serious and different space positions show different deformation characteristics. In order to further explore the deformation localization and progressive failure phenomenon of soft SR around the deeply buried tunnel, applying the analysis software of FLAC3 D three-dimensional explicit finite-difference method, based on the composite strain-softening model of Mohr-Coulomb shear failure and tensile failure, the calculation method of large deformation was adopted. Then, the comparative analysis between the PM experiment and numerical simulation of the three centered arch tunnels was implemented and the relationship of deformation localization and progressive failure of SR around a tunnel under high stress conditions was discussed.

Numerical simulation study on hard-thick roof inducing rock burst in coal mine

In order to reveal the dynamic process of hard-thick roof inducing rock burst, one of the most common and strongest dynamic disasters in coal mine, the numerical simulation is conducted to study the dynamic loading effect of roof vibration on roadway surrounding rocks as well as the impact on stability. The results show that, on one hand, hard-thick roof will result in high stress concentration on mining surrounding rocks; on the other hand, the breaking of hard-thick roof will lead to mining seismicity, causing dynamic loading effect on coal and rock mass. High stress concentration and dynamic loading combination reaches to the mechanical conditions for the occurrence of rock burst, which will induce rock burst. The mining induced seismic events occurring in the roof breaking act on the mining surrounding rocks in the form of stress wave. The stress wave then has a reflection on the free surface of roadway and the tensile stress will be generated around the free surface. Horizontal vibration of roadway surrounding particles will cause instant changes of horizontal stress of roadway surrounding rocks; the horizontal displacement is directly related to the horizontal stress but is not significantly correlated with the vertical stress; the increase of horizontal stress of roadway near surface surrounding rocks and the release of elastic deformation energy of deep surrounding coal and rock mass are immanent causes that lead to the impact instability of roadway surrounding rocks. The most significant measures for rock burst prevention are controlling of horizontal stress and vibration strength.Key words

Roadway failure and support in a coal seam underlying a previously mined coal seam

The influence of an upper,mined coal seam on the stability of rock surrounding a roadway in a lower coal seam is examined.The technical problems of roadway control are discussed based on the geological conditions existing in the Liyazhuang Mine No.2 coal seam.The stress distribution and floor failure in the lower works after mining the upper coal is studied through numerical simulations.The failure mechanism of the roof and walls of a roadway located in the lower coal seam is described.The predicted deformation and failure of the roadway for different distances between the two coal seams are used to design two ways of supporting the lower structure.One is a combined support consisting of anchors with a joist steel tent and a combined anchor truss.A field test of the design was performed to good effect.The results have significance for the design of supports for roadways located in similar conditions.

Deformation tests and failure process analysis of an anchorage structure

In order to study the failure process of an anchorage structure and the evolution law of the body＇s defor- mation field, anchor push-out tests were carried out based on digital speckle correlation methods （DSCM）. The stress distribution of the anchorage interface was investigated using the particle flow numerical simulation method. The results indicate that there are three stages in the deformation and fail- ure process of an anchorage structure： elastic bonding stage, a de-bonding stage and a failure stage. The stress distribution in the interface controls the stability of the structure. In the elastic bonding stage, the shear stress peak point of the interface is close to the loading end, and the displacement field gradually develops into a ＂V＂ shape, in the de-bonding stage, there is a shear stress plateau in the center of the anchorage section, and shear strain localization begins to form in the deformation field. In the failure stage, the bonding of the interface fails rapidly and the shear stress peak point moves to the anchorage free end. The anchorage structure moves integrally along the macro-cracl~ The de-bonding stage is a research focus in the deformation and failure process of an anchorage structure, and plays an important guiding role in roadway support design and prediction of the stability of the surrounding rock.

Interaction analyses between tunnel and landslide in mountain area

This paper focuses on the analytical derivation and the numerical simulation analyses to predict the interaction influences between a landslide and a new tunnel in mountain areas. Based on the slip-line theory, the disturbance range induced by tunneling and the minimum safe distance between the tunnel vault and the sliding belt are obtained in consideration of the mechanical analyses of relaxed rocks over the tunnel opening. The influence factors for the minimum safe crossing distance are conducted,including the tunnel radius, the friction angle of surrounding rocks, the inclination angle of sliding belt,and the friction coefficient of surrounding rocks. Secondly, taking account of the compressive zone and relaxed rocks caused by tunneling, the Sarma method is employed to calculate the safety factor of landslide. Finally, the analytical solutions for interaction between the tunnel and the landslide are compared with a series of numerical simulations, considering the cases for different perpendicular distances between the tunnel vault and the sliding belt. Resultsshow that the distance between the tunnel vault and the slip zone has significant influence on the rock stress and strain. For the case of the minimum crossing distance, a plastic zone in the landslide traversed by tunneling would be formed with rather large range, which seriously threatens the stability of landslide. This work demonstrates that the minimum safe crossing distance obtained from numerical simulation is in a good agreement with that calculated by the proposed analytical solutions.

A NEW COMPUTATION METHOD FOR THE UNSTEADY HEAT TRANSFER COEFFICIENT IN A DEEP MINE

In mine geothermal prediction, the unsteady heat transfer coefficient is an important parameter for heat transfer computation between country rock and mine airflow. In this paper, the rock temperature distributions in the geothermal fields have been derived in mathematics, the unsteady heat transfer coefficients that can expound the relation between its nature and influencing factors have been derived also based on this analytic formula. It is shown both by numerical simulations and through in situ measurernents that the new computation method for determining the unsteady heat transfer cofeeicient is accurate, rapid and simple.

Control technology and coordination deformation mechanism of rise entry group with high ground stress

Based on engineering practices of Wuyang Coal Mine, we carried out X-ray diffract researches on No. 3 coal; and the rocks of its roof and floor by XRD meter, and simulated the interactive effect of the surrounding rock deformation by FLAC2DS.0 numerical simulation software under the condition of different tunneling method of multimine roadway in parallel. The internal structures of the surrounding rocks of 76 belt roadway were monitored by borehole observation instruments： and then, we analyzed the reason of fhilure and deformation of surrounding rocks of several rise entry, and proposed the technical mea- sures for controlling interactive effect of several rise entry surrounding rock deformation at last. For the thickness seam rise roadway, two conclusions were drawn： one is that the co-deformation among roadway groups mainly reflect on that both shear failure and deformation in coal pillar among roadways have decreased the width of pillar core region and clamping action of coal pillar to roof strata, increased the actual span of roof strata, intensified the flexural failure of roof strata and prized the bed separation of roof deep rock strata. The other conclusion is that the factors controlling the interactive deformation among roadways is obvious when appropriate re-adjustment in construction sequence of the tunneling of multimine parallel roadways because the construction sequence among roadways also has great effects on deformation of the surrounding rock in roadway.

Numerical analysis on stability of surrounding rock mass around deep roadway

Numerical simulations of the deep roadway were carried out through application of the strain-softening constitutive model. Differences between the deep and shallow roadway of the rock bearing structure were analyzed. Influences of the supporting resistance on the rock bearing structure at the deep roadway were discussed. The results show that there is alternation of strong and weak strength-softening region in the surrounding rock of deep roadway. However, the increase in the supporting resistance cuts down the size of strength-softening region of surrounding rock, decreases its strength-softening degree, and im- proves the stress distribution condition of the surrounding rock mass. It is concluded that the supporting resistance can raise the self-supporting ability of surrounding rock through controlling its strength-softening so as to make the rock bearing structure of deep roadway stable.