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.     

邢台矿区三维地应力测量及应力场分析

介绍了空心包体法地应力测量的原理、特点及在邢台矿区４个矿井进行三维地应力测量的主要过程,并且对测量结果进行了分析．结果表明：邢台矿区浅部以自重应力为主,深部构造应力显著,最大主应力为北东偏北向的近水平压应力．测量结果与华北地区地应力场总体变化规律吻合．     

Rules of distribution in a plastic zone of rocks surrounding a roadway affected by tectonic stress

In order to study the rules of distribution in a plastic zone of rocks, surrounding a roadway, affected by tectonic stress, we first analyzed the mechanics of a roadway affected by tectonic stress and derived a theoretical formula for the plastic zone of rocks surrounding a roadway. We also analyzed the distribution characteristics of the plastic zone under different levels of tectonic stress, vertical pressure, cohesion and friction angle of the surrounding rock. Secondly, we used numerical simulation to analyze the range and shape features of the plastic zone of rocks surrounding the roadway, given different tectonic stress levels. Finally we used a rock drilling detector to carry out field measurements on the broken state of rock surrounding the roadway at the -700 substation and channels in the Xinzhuang mine of the Shenhuo mining area. Given the measured ground stress, we analyzed the relationship between tectonic stress and the distribution of this plastic zone. Our results show that the range of the plastic zone at the top and bottom of the roadway increases with an increase in tectonic stress and this increase is especially obvious at the roadway comer.     

不同受力状态下岩石破坏过程次声信号特征

采用室内试验方法,分别开展了岩石在压缩、剪切和拉伸状态下的破坏试验,利用高灵敏度的次声信号采集设备同步采集岩石破坏过程中的次声信号,对不同受力状态下岩石次声信号的特征差异进行了研究。结果表明:在压缩状态下,岩石次声信号发射主要在弹性和塑性变形阶段,次声信号的峰值频率在7 Hz左右,在岩石临近破坏前,次声信号振幅和频率范围均有所增加;在剪切状态下,次声信号主要集中在峰值后应力逐步下降的阶段,信号功率分布集中程度较压缩试件略低,峰值频率在8 Hz左右;在拉伸状态下,试件加载初始阶段便有次声信号发生,次声信号频率通常存在高、低两个中心,其中低频与压缩试件接近,高频则高出3 Hz,拉伸试件内部裂隙的萌生和发展较压缩和剪切状态下更为迅速、有序,随着试件内部裂隙的发展,次声信号频率逐渐升高。以上特征的发现为不同受力状态下次声信号的识别以及岩体灾变预测提供了依据。     

软质岩中压力型锚索锚固段应力分布特征

为了研究软质岩中压力型锚索锚固段应力分布和传递规律,进行了足尺现场试验。制作了与实际工程条件相似的试验锚索,在试验锚索的锚固段砂浆体中按一定间距设置了应变砖,记录了在不同张拉荷载下各测点的应变情况,测得压力型锚索锚固段的轴向应变和径向应变分布曲线。通过对试验结果进行分析处理,得到了锚固段与围岩界面剪应力分布曲线。测试结果与已有理论计算结果比较吻合。分析结果表明,在软质岩条件下,承载板附近的锚固体出现了明显的三向应力状态;锚固体中应力传递长度较短;注岩界面剪应力峰值可以达到较高的水平;随着荷载增大,剪应力有向前转移扩张的趋势。     

应变非线性软化的预应力衬砌隧洞弹塑性应力解

基于岩体单轴应变非线性软化本构模型,采用全量理论将其推广,获得考虑中间主应力影响的复杂应力状态下的岩体等效应力和等效应变关系,由此对灌浆式预应力衬砌隧洞进行弹塑性分析.指出预应力作用下围岩可能处于弹性或弹塑性两种状态,给出了两种情况下围岩压力、塑性区半径及衬砌应力的解析计算式,得到了围岩产生塑性变形的临界灌浆压力,并结合某工程进行了具体分析.     

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。     

论沉积区岩体地应力分布

本文通过对地表沉积作用过程中岩体受力状态的力学分析,结合对沉积区岩体实测地应力范例的讨论,论述了沉积区岩体地应力分布的一般特性。     

Research on Mechanism of Rock Burst Generation and Development for High Stress Rock Tunnels

Through the investigation and analysis of high stress distribution in surrounding rock during the excavation of rock tunnels,the key factors to cause rock burst and the mechanism of rock burst generation and development are researched. The result shows that the scale and range of rock burst are related with elastic deformation energy storied in rock mass and the characteristics of unloading stress waves. The measures of preventing from rock burst for high stress rock tunnels are put forward.     

基于有限元数学模型的隧道围岩初始地应力场反演

由于初始地应力场的分布是影响隧道围岩稳定性的重要因素之一,得合理有效地模拟地应力场的分布在隧道工程中的应用显的尤为重要.本文根据地应力实测数据和有限元数学模型,提出了区域构造应变回归分析方法.在此基础上结合工程实例,运用构造应变同归分析和当前应用广泛的边界应力同归分析两种方法模拟了隧道围岩的地应力场的分布,并对两种方法...     

公路隧道应力释放率对软弱围岩稳定性影响

近年来,由于新奥法广泛地运用于地下工程的施工过程中,围岩与支护结构之间的相互作用以及支护时机受到越来越多的关注。中条山隧道洞口段软弱围岩开挖步序多、工序及应力变化复杂,尤其是核心土解除后和二衬施工前安全风险大。本文采用有限差分软件对该隧道洞口段施工过程进行三维数值模拟,研究了洞周位移及支护结构在不同应力释放率下的力学响应,重点分析了典型断面处洞周围岩及支护结构的位移和受力情况,以及洞周位移随施工过程的动态变化规律。研究结果表明：对于软弱围岩公路隧道,应力释放率越大,围岩的塑性区发展范围越大,洞周位移越大;开挖过程中,拱顶沉降受到的持续性扰动较大;待二次衬砌施作后,仰拱隆起和收敛位移趋于稳定。     

含山陶厂石膏矿构造应力场数值模拟分析

为了分析井田内主要构造断裂的导水性,为断层岩柱留设提供依据,运用有限元法的三维数值模拟程序,对陶厂石膏矿现代构造应力场进行了模拟。模拟结果表明,在断层F17附近存在较大的压应力,在F1及F2断层附近的石膏矿体中存在拉应力,在石膏矿体中的应力水平相对较低且均一。断层附近的Z方向的应力相对石膏矿体的应力低。应力矢量分布中拉应力矢量主要分布在石膏矿体靠近断层附近,随着石膏矿体与断层距离的增加,逐渐转化为压应力,而在断层的交汇处压应力值较高。     

基于统一强度理论的井筒围岩应力分析

在考虑井筒周围岩石的渗流作用和孔隙水压力的基础上,对有效应力进行了修正;基于统一强度理论,充分考虑中间主应力,对井筒周围岩石进行了弹塑性分析,并给出了井筒周围岩石的应力分布表达式和保持井壁稳定的弹性极限荷载及塑性极限荷载的统一解析式。分析结果表明：通过改变统一解析式中的参数,可将其退化为其他强度理论条件下的解析式,所得的统一解适用于不同强度理论条件下各类岩石材料的弹塑性分析;有效应力修正后的极限分析为井壁稳定分析提供了理论依据,具有一定的理论及实际应用价值。     

初始应力状态对侧限条件黏土动态压缩过程和力学性能的影响

黏土的初始应力状态对其动力学性质有显著的影响。本文采用长时、分级、高压固结方式模拟了黏土的原始应力赋存环境,采用SHPB实验装置对侧限条件下的高压固结黏土进行应变率范围为200~800 s_^-1的冲击压缩实验,分析了黏土应力记忆效应、应变率效应和动态压缩过程。实验结果表明,黏土的应力历史影响了其动态压缩过程,试样依次经历压实段—线弹性加载段—线性卸载段,在动载下黏土压实段与线弹性加载段应力拐点的均值为3.8 MPa,与先期固结应力4.2 MPa具有相关性,并且压实段应变均值约为试样破坏应变的33%;采用200 mm和300 mm的短子弹进行冲击加载时,黏土试样未发生稳定的塑性变形,分析应力-应变率曲线发现,黏土的压实过程吸收了一部分动载能量,使其无法持续进行动态压缩行为,但进入动态压缩阶段后黏土受子弹长度影响较小;黏土试样动态加卸载段模量随应变率同步增加,但加卸载模量的比值稳定在0.45左右,表明更高的冲击速度没有造成试样进一步的损伤,这与冲击后的宏观破坏现象及塑性变形分析相互印证。实验结果也说明,针对软弱、松散颗粒体材料,高压固结方式为研究其动力学性质提供了一种思路。     

Zonal disintegration phenomenon in enclosing rock mass surrounding deep tunnels -- Elasto-plastic analysis of stress field of enclosing rock mass

The zonal disintegration phenomenon (ZDP) is a typical phenomenon in deep block rock masses. In order to investigate the mechanism of ZDP, an improved non-linear Hock-Brown strength criterion and a bi-linear constitutive model of rock mass were used to analyze the elasto-plastic stress field of the enclosing rock mass around a deep round tunnel. The radius of the plastic region and stress of the enclosing rock mass were obtained by introducing dimensionless parameters of radial distance. The results show that tunneling in deep rock mass causes a maximum stress zone to appear in the vicinity of the boundary of the elastic and the plas-tic zone in the surrounding rock mass. Under the compression of a large tangential force and a small radial force, the rock mass in the maximum stress zone was in an approximate uniaxial loading state, which could lead to a split failure in the rock mass.     

深部隧道围岩的流变

隧道围岩的流变对于隧道的长期稳定性影响很大,尤其对于深部隧道来讲更是如此. 目前利用线性及非线性粘弹性流变模型对于隧道围岩的研究较多,初始状态多取为弹性状态. 但在深部,由于初始地应力很大,在隧道开挖后,可能会马上出现塑性区. 因此初始参照状态应该取为弹塑性状态,而且应该考虑塑性区及弹性区力学性质的不同. 现利用Shvedov-Bingham模型理论研究了隧道围岩在初始时刻出现塑性区情况下的流变情况,并考虑塑性区及弹性区力学性质的不同, 给出了流变区半径及应力应变的解析解,并分析了应力分布及流变半径的变化规律.     

岩芯饼化的临界地应力及岩饼厚度与地应力的关系

本文用试验和电算的方法,找出了单向水平地应力在岩芯中波及的范围和分布规律,得出了应力释放后岩芯中残留应力范围的空间壳体曲面,作出了岩芯中贮存残留应力的体积为“台体”的假设,推导出了岩芯饼化的临界地应力公式和地应力与岩饼厚度的关系式。应用这两个公式,可以求得任何岩石饼化的单向水平临界地应力和任何岩芯饼化地区地应力的大小。本文用推导的公式,计算出了二滩电站坝区正长岩的临界地应力和岩芯饼化地层的地应力。     

Stress and deformation analysis on deep surrounding rock at different time stages and its application

Based on the characteristics of the deep circular tunnel, the surrounding rock was divided into three regions: the cracked region, the plastic region and the viscoelastic region. The process of rock stress deformation and change was divided into three stages after the roadway excavation. By using the elastic–plastic mechanics theory, the analytical solutions of the surrounding stress and displacement at different stages and the radii of cracked and plastic regions were formulated. We additionally explained the surrounding rock stress and displacement which appeared in practical project. Simultaneously, based on the problem which emerged from a mine in Xuzhou during the excavating process of rock roadway’s transport, we got the theoretical solutions for the stress and displacement in the process of rock roadway’s excavation and considered that the broken area of rock roadway was largely loosing circle. The results indicate that according to the rheological characteristics of surrounding rock, in the primeval excavation of rock roadway, we should increase the length of anchor bolt and cooperate it with anchor nets cable-U steel supporting frame. In addition, when the deformation rate of the surrounding rock is descending after the 15 days’ excavation, we should use the “three anchor” supporting method (anchor bolt spray, anchor note and anchor rope) and set aside about 20 cm as the reserved deformation layer.     

对轴对称荷载作用圆巷围岩理想弹塑性分析解的讨论

对轴对称荷载作用圆巷围岩理想弹塑性分析解——Kastner解适用于软岩和小变形情况,若用于非软岩和大变形情况,从Kastner方程会导得：不论巷道围岩塑性变形多大,巷道周边切应力恒等于岩体峰值强度;围岩所承受的地应力可以随围岩塑性区半径增大而持续增大,随巷道周边位移增大而持续增大;此外,Kastner解中切应力分布曲线在围岩弹、塑性区交界处有尖峰向上的应力集中.采用符合岩石实际的弹性、非线性硬化和软化光滑连接的应力-应变关系得到的巷道围岩分析解,可以弥补以上三点不足,恰当地反映巷道临界深度和巷道围岩自承地应力极限问题;所绘出的切应力分布曲线在围岩弹、塑性区交界处光滑连接,因而有更广的适用性和精确性,对巷、隧道围岩大变形支护设计有参考作用.     

基于测井和压裂资料的储层三向地应力求取方法

利用相关测井资料计算储层岩石的动态力学参数,并通过室内岩石力学三轴实验将动态的岩石力学参数转化为水力压裂工程可用的岩石力学静态参数,提出储层三向地应力剖面的计算方法.以义H井为例,计算连续的岩石静态力学参数和地应力剖面.