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1.
The effect of opening size, rock properties and stress conditions on the radial displacements ahead and behind of the advancing face of a circular opening is one of the most important topics in civil and mining engineering. In this paper we develop a prediction system for radial displacements around the face of an opening by combining rock mass rating classification system, a three dimensional finite difference code and multiple regression modeling. Predictive equations and response surfaces for rock mass response are proposed. By using these equations and response surfaces, it is possible to assess radial displacements around the face and to construct the longitudinal deformation profile of a circular opening with different diameters excavated in weak rock mass under different stress conditions. The predictive equations were validated by means of statistical tests and analytical solution. Proposed response surfaces and equations can provide the basis of guiding the design and construction of underground openings.  相似文献   

2.
非轴对称荷载下圆形隧道弹性围岩应力解析解   总被引:1,自引:0,他引:1       下载免费PDF全文
隧道开挖后需依据岩体的变形特性对隧道围岩进行合理分区。针对隧道围岩弹塑性临界变形时强度逐渐降低的特性,结合非轴对称荷载作用的模型特点,选用俞茂宏双剪统一强度理论中双剪三参数准则,采用半逆解法,侧压力系数在[1/3,1)区间取值,推导出圆形隧道在非轴对称荷载作用下弹性围岩区应力分布解析解。实例分析表明,考虑了地应力非轴对称分布的力学模型可很好地反映围岩变形特点,所选强度理论符合岩体材料自身特殊的强度特征,其解析思路更贴近围岩的实际状态,对围岩支护设计具有现实指导意义。  相似文献   

3.
In this study, numerical modeling on the damage of existing circular tunnel subject to blast-induced shock wave was carried out with DEM-based code UDEC. The disturbed zones including failure zones, open zones and shear zones around circular tunnel and peak particle velocities (PPVs) at tunnel surface are employed to analyze the damage of tunnel. The effects of joint spatial and mechanical properties, initial stress of rock mass, and magnitude of shock wave amplitude to damage of tunnel were evaluated in this study. The difference of damage between non-supported circular tunnel and bolt-supported circular tunnel subject to the same blast-induced shock wave was also studied. It is found that the orientations of joints in rock mass around the tunnel have great effects on tunnel damage. The initial stress around tunnel has relatively small influence on tunnel damage. The bolt support could greatly increase the stability of tunnel by changing the vibration form of particle velocity rather than the decreasing of PPV.  相似文献   

4.
深部坑道围岩的变形与承载能力问题   总被引:8,自引:5,他引:8  
通过传统连续介质力学理论描述宏观尺度上的岩块行为,借助光滑函数的组合描述岩块间间断位移场的不光滑性,从而揭示了岩块界面的局部变形行为,使得能量在介质中的存储、耗散与通过间断界面边界转移的能得到数学刻画。在该理论框架下,以圆形坑道围岩压力确定为例,通过简化的应力–滑移关系,计算出围岩各区所承受的荷载比例,阐明了岩石压力与坑道的埋深、坑道的尺寸和形状、围岩的物理力学性质以及支护的柔度等具有直接的关系。  相似文献   

5.
Shale gas is becoming an important energy source worldwide.The geomechanical properties of shale rocks can have a major impact on the ef fi ciency of shale gas exploration.This paper studied the mineralogical and mechanical characteristics of a typical gas shale in Ohio,USA.Scanning electron microscope(SEM)with energy dispersive X-ray(EDX)analyses was employed to measure the microstructure and material composition of the shale rock.The anisotropic behaviors of shale rock,including compressive and tensile strengths,were experimentally measured.The characteristics of shale rock were also studied by nondestructive wave speed measurements.The shale demonstrated strong anisotropic behaviors with the tensile strengths perpendicular to the bedding plane around 300e360 times of that parallel to bedding plane.Results of ultrasonic tests indicated that both compression and shear wave velocities show strong anisotropic patterns.The compression wave speed was the smallest in the direction perpendicular to the bedding plane;while the shear wave speed was the smallest in the direction parallel to the bedding plane.The ratio of wave speed anisotropy is around 1.3e1.4 for compression wave;the ratio of shear wave speed anisotropy is larger and more diverse compared with the compression wave anisotropy.This might be related to the larger variability in the frictional adhesive strength along bedding plane than the compressive adhesive strength.  相似文献   

6.
史孝辉  齐和涛 《山西建筑》2010,36(9):339-340
以深部静水平压力条件下的圆形隧道为背景,分析了隧道周围的主应力差值分布规律及其导致岩体失稳的破坏机理,研究表明:在隧道周围存在一个界限明确的应力剪切带,剪切带内具有较大的主应力差值,是岩体破坏的易发区域,进行锚杆支护时,锚杆的长度必须大于该区域的深度才能取得可靠的支护效果。  相似文献   

7.
An analytical model is proposed to predict the axial force of grouted rock bolt in the tunnelling design. The interaction mechanism of the rock bolt and the soft rock mass has been described according to their consistent displacement. Coupling and decoupling behaviors of the rock bolt around a circular tunnel have been analyzed. According to case studies, the theoretical prediction of the axial force agrees well with the in situ measured results. The installing time and the length of the rock bolt, and the deformation modulus of the rock mass are taken as study parameters to analyze the supporting behavior of the rock bolt. According to the results of the theoretical analysis, there are some conclusions as followings: (1) a lower axial force is resulted because of the delay of installing rock bolt and its supporting effect may be reduced; (2) the larger displacement is caused by the lower deformation modulus of the rock mass, and a higher axial force is resulted in the rock bolt. If the shear strength of the rock mass is not enough, the decoupling behavior will take place interior the rock mass, and the performance of rock bolt may be reduced; (3) the position of a neutral point is related with the radius of tunnel, the physical properties of the rock bolt and the rock mass. It is found that the position of the neutral point and the maximum axial force of the rock bolt installed in the soft rock may tend to be constant when its length is long enough, which means that the supporting effect of the rock bolt can not be improved significantly only by increasing the length of the rock bolt. By using this model, a way is supplied to analyze the supporting behavior of the rock bolt, and a method is provided for the quantitative evaluation of its supporting effect in NATM tunnelling.  相似文献   

8.
流变岩体中既有隧道与新建平行隧道相互影响的理论解   总被引:1,自引:0,他引:1  
在流变岩体中进行隧道施工时,既有隧道与新建隧道的相互作用将使围岩应力、位移分布与单隧道问题有明显不同,且与时间相关。针对黏弹性岩体中深埋双圆形隧洞考虑施工顺序问题,用复变函数方法、Laplace变换、黏弹性叠加关系导出两隧道周边开挖增量位移和应力场的求解方法和理论解答,并与有限元解进行了比对。根据解答分析了既有和新建隧道孔边增量位移与全应力分布特点;隧道周边增量位移随时间的变化;周边位移随隧道间距的变化规律。可用于黏弹性岩体中双圆形隧道顺序开挖的施工分析。相比数值方法,理论解可更方便地进行参数分析和初步设计。  相似文献   

9.
以锦屏二级水电站TBM开挖的圆形断面施工排水洞为例,首先根据围岩实际破坏特性明确指出围岩劈裂后产生弧形岩板的客观存在性,然后提出其存在发生凹曲变形(指其发生弯曲方向指向隧洞外部、半径减小即曲率增大的弯曲变形)的可能性,最后从力学分析与数值试验两个方面对弧形岩板发生凹曲变形的可能性进行了论证。论证显示:对处于垂直地应力与水平地应力不相等条件下的深埋圆形隧洞,弧形岩板可以发生凹曲变形,发生的控制因素是两向应力差对圆形隧洞产生的垂直方向压缩、水平方向拉伸的压扁作用。弧形岩板凹曲变形的论证对今后深入认识深埋圆形隧洞完整或较完整硬岩动力破坏的发生机制提供了一条新思路。  相似文献   

10.
岩体非均质性研究是地质资源与地质工程领域的重要内容,对地下空间及矿产能源的合理开发利用有着重要的意义。为了实时准确地评价页岩储层岩体的非均质性,将钻孔过程监测(Drilling Process Monitoring, DPM)引入铜川地区鄂尔多斯盆地延长组陆相页岩的现场勘察钻孔试验中,分别监测了钻头转速、钻杆前推压力、钻杆回撤压力、动力头位置4个参数,利用DPM钻进速率参数从多尺度对页岩岩体的非均质性进行了刻画。相关性分析及回归分析结果表明:DPM钻进速率与岩石可钻性、岩体完整性存在显著的相关性。具体地,储层尺度上,DPM钻进速率的变化可反映出储层岩性的变化,DPM钻进速率可定量地评价岩石的可钻性;岩心尺度上,DPM钻进速率的变化可定性地反映出岩芯的完整程度,但在≤100 mm完整岩芯上的钻进速率并不能有效反映出纹层岩性的变化。进一步地,纹层尺度上,>100 mm厚度页岩纹层的纯钻过程位移曲线可被较好地进行线性拟合,而100 mm以下,泥岩、粉砂岩及凝灰岩纹层的纯钻过程位移曲线线性拟合性较差。研究结果对于正确认识DPM对岩体非均质性的划分及应用有着重要的指导意义。  相似文献   

11.
A closed-form solution is presented in this paper for the prediction of displacements around circular openings in a brittle rock mass subject to a hydrostatic stress field. The rock mass is assumed to be governed by Hoek–Brown yield criterion and a non-associated flow rule is used. For the elastic–brittle–plastic analysis of circular openings in an infinite Hoek–Brown medium, the existing analytical solutions were found to be incorrect. The present closed-form solution is based on a theoretically consistent method and the solution does not require the use of any numerical method.The present closed-form solution was validated by using the finite element method. In the finite element analysis, the infinite boundary was simulated “exactly” by using the newly developed elastic support method. Several cases were analyzed and the present closed-form solutions for stresses and displacements were found to be in an excellent agreement with those obtained by using the finite element method.  相似文献   

12.
 将岩体看成不含原生宏观裂隙而仅含原生微裂纹的颗粒材料。在开挖卸荷过程中,原生微裂纹启裂、扩展并穿过岩石基质,产生次生裂纹。此时,岩体出现非连续和非协调变形,经典的弹塑性力学理论不再适用于研究岩体的非连续和非协调变形情况。基于自由能密度、平衡方程和变形非协调条件,提出一种新的非欧模型,确定微裂纹半长度和密度对标量曲率和自平衡应力的影响,获得深部圆形洞室围岩应力场,它包括弹性应力和自平衡应力。由于自平衡应力的影响,当微裂纹的密度和半长度较大时,深部圆形洞室围岩的应力场具有明显的振荡特性。但是,当微裂纹的密度和半长度较小时,深部圆形洞室围岩的应力场振荡特性不明显。对于位于波峰附近的微裂纹,其尖端的应力集中将导致次生裂纹的失稳扩展、连接、合并成宏观裂隙,形成破裂区;而对于位于波谷附近的微裂纹,其尖端应力集中不足以导致次生裂纹发生失稳扩展,因此出现非破裂区。深部圆形洞室围岩应力场交替出现波峰和波谷现象导致破裂区和非破裂区的交替出现,即分区破裂化现象。通过数值模拟,详细研究微裂纹半长度和密度对深部岩体分区破裂化现象的影响。  相似文献   

13.
岩体节理平均迹长估计   总被引:4,自引:4,他引:4  
分析总结岩体节理平均迹长的估计方法后,扩展了测线法节理平均迹长估计的理论基础。扩展后的测线法在相同的现场节理调查数据下,可更加准确地估计岩体节理的平均迹长。同时指出,采用圆形窗口法平均迹长估计时,假设迹线中点在窗口中均匀分布与实际情况偏差很大,为避免迹线中点不均布的情况必须保证窗口的尺度足够大。随着圆形取样窗口的增大,迹线中点密度在窗口中的变化减小,估计所获得的节理平均迹长的准确度较高。通过现场节理调查获得丰富的节理数据,采用扩展的测线法和圆形窗口法分别估计岩体节理的平均迹长。当圆形窗口的直径与测线法删节长度相等时,扩展测线法和圆形窗口法估计所得的岩体节理平均迹长比较接近,由此可确定研究区域的岩体节理平均迹长。  相似文献   

14.
深埋巷道分区破裂化机制   总被引:6,自引:17,他引:6  
深部巷道外部受到远场原岩应力的作用,而内壁受到一个随时间变化的内压作用,开挖过程是动力问题,其运动方程可以用位移势函数来表达。通过对运动方程进行Laplace变换,进而求得其通解。根据弹性力学知识和边界条件得到巷道围岩由于开挖扰动和原岩应力作用引起的弹性应力场和位移场。当该弹性应力场满足破裂条件时,岩体发生破裂,位移不连续,形成破裂区。结合断裂力学知识,确定破裂区岩体的残余强度和产生破裂区的时间,进而确定破裂区和非破裂区的宽度和数量。数值分析结果表明,巷道分区破裂化的产生跟开挖速度与岩石强度有关。该研究可为深部岩体的开挖和支护设计提供初步的理论基础。  相似文献   

15.
某膨胀岩洞段,围岩强度低,抗风化能力弱,水理性质不良,易发生吸水膨胀失水收缩现象。基岩洞段褶皱、褶曲发育,地层产状变化大,围岩呈层状~碎裂结构。双护盾TBM开挖后,隧洞发生不同程度的坍塌与塌方。现采取“三低一连续”(低推力、低转速、低贯人度;快速连续掘进)快速封闭围岩,严格控制施工用水;使用化学材料灌浆固结围岩等施工应用技术,成功通过了泥质软岩类隧洞长地段,为今后双护盾掘进机施工提供了宝贵经验,社会和经济效益巨大。  相似文献   

16.
本文运用复变函数方法给出了带有一个裂隙的圆孔周围的应力分布,特别在单轴或双轴应力场中,对任意方位的单一裂隙的解答都可用该方法获得。在该方法中,使用施瓦茨(Schwartz)积分推导出了从带有任意方位单一裂隙的圆孔到单位圆的映象函数。 根据这个理论结果,完成了对五种不同裂隙方位和四种不同裂隙长度的数值计算,获得了相应的圆孔周围的应力相位移分布。运用岩石的脆性断裂理论,分析了这些裂隙对圆形隧道周围应力和位移分布及围岩断裂的影响。分析结果表明裂隙的方向和位置对围岩断裂的影响是显著的。  相似文献   

17.
针对岩体自身承载能力的评价,修改抗力系数提出了岩体新的自承载系数,给出其物理意义,并以理想弹–塑性围岩中圆孔收缩和扩张为例,推导了岩体缩孔自承载系数Kc和扩孔自承载系数Ke,得出各参数的影响特性。研究结果表明:岩体自承载系数是一个受多因素共同影响的综合评价指标,应力状态和孔壁压力对其具有显著影响;岩体自承载系数随岩体强度参数和统一强度理论参数的增加而增大,随剪胀参数的增加岩体缩孔自承载系数Kc减小,而扩孔自承载系数Ke却增大。应充分考虑岩体强度参数的变化、中间主应力效应和剪胀特性的影响,合理利用岩体的强度潜能和自承载能力。  相似文献   

18.
深部岩体具有典型的不均匀、不连续的自应力块系等级构造结构。由于浅部巷道围岩应力场分析是基于连续介质力学理论,没有考虑岩体的块体特性,因而无法应用于深部巷道块系围岩的应力场分析。考虑到深部巷道块系围岩破坏类型主要表现为峰后岩块沿软弱接触面的剪切滑移破坏,通过建立深部巷道的平面应变块系围岩模型,得到了轴对称条件下岩块相互作用的解析解;分别假设岩块之间的接触满足刚塑性和Mohr-Coulomb屈服条件,推导得出上述两种屈服条件下的块系围岩模型和连续介质模型的围岩支护力的计算公式。对比分析表明:围岩块体构造特性对深部巷道施工和承载力设计计算有重要的影响;通过假设块体间剪应力与剪切滑移满足分段线性关系,得到了块系围岩径向位移,剪应力和剪切滑移量的解析表达式,引入无量纲化的深部巷道块系围岩稳定性参数λ,并得出当λ<1时块系围岩是稳定的,当λ>1时块系围岩是不稳定的。  相似文献   

19.
Fractures that develop progressively around underground excavations can be simulated using a numerical code called RFPA (rock failure process analysis). This code incorporates the mesoscopic heterogeneity in Young’s modulus and rock strength characteristic of rock masses. In the numerical models of a rock mass, values of Young’s modulus and rock strength are realized according to a Weibull distribution in which the distribution parameters represent the level of heterogeneity of the medium. Another notable feature of this code is that no a priori assumptions need to be made about where and how fracture and failure will occur – cracking can occur spontaneously and can exhibit a variety of mechanisms when certain local stress conditions are met. These unique features have made RFPA capable of simulating the whole fracturing process of initiation, propagation and coalescence of fractures around excavations under a variety of loading conditions. RFPA is used herein to simulate progressive fracturing processes around three common shapes of underground excavations – circular, elliptical and inverted U-shaped. The results of the simulations show that the code can be used not only to produce fracturing patterns similar to those reported in previous studies, but also to predict fracturing patterns under a variety of loading conditions. Based on these fracturing patterns, failure mechanisms are identified for various loading conditions.  相似文献   

20.
在水工圆形压力隧洞衬砌应力计算中,假定岩体是弹性体,这与岩体变形特性不完全相符。本文根据原位岩体变形试验结果,考虑了岩体弹-塑性变形,按线性强化材料处理,建立了衬砌应力计算方法,给出了岩体产生塑性变形的临界内水压力,并指出了岩体力学参数如何确定。  相似文献   

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