共查询到20条相似文献，搜索用时 31 毫秒
1.
环境湿度在水敏感岩体中的扩散对隧洞等地下空间的变形起到至关重要的作用,不仅改变岩体的应力状态,还在很大程度上造成岩体物理力学性能的弱化,增强了岩体的时效变形特性。通过在数值模型中引入湿度扩散计算,并建立湿度扩散与岩体力学响应之间相互关系的描述,使得数值模型能模拟水敏感岩体受湿度影响的时效变形特征。针对具有支护系统的隧洞岩体在湿度扩散过程中的变形和应力特性的数值模拟研究表明：开挖初期,只有围岩表面的湿度产生变化,湿度引起的隧洞变形量也较小,但其变形速率却较大。随着湿度的进一步扩散,隧洞的变形总量增加,但变形速率逐渐降低,并最终得以收敛;数值计算再现了锚杆系统中的应力演化过程,其中拉应力的逐渐增大限制了围岩的部分变形;湿度在围岩中的扩散造成较大范围内围岩的强度降低,承载能力减弱,隧洞周边逐渐产生破坏。破坏的产生不仅引起局部应力集中,促使裂纹的进一步扩展,还有助于水分在围岩中的扩散。因此,湿度扩散和破坏（损伤）是一个相互影响的过程,也即湿度-应力-损伤耦合作用 相似文献
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Analytical Solutions for the Construction of Deeply Buried Circular Tunnels with Two Liners in Rheological Rock 总被引：1，自引：0，他引：1
H. N. Wang Y. Li Q. Ni S. Utili M. J. Jiang F. Liu 《Rock Mechanics and Rock Engineering》2013,46(6):1481-1498
The construction of underground tunnels is a time-dependent process. The states of stress and strain in the ground vary with time due to the construction process. Stress and strain variations are heavily dependent on the rheological behavior of the hosting rock mass. In this paper, analytical closed-form solutions are developed for the excavation of a circular tunnel supported by the construction of two elastic liners in a viscoelastic surrounding rock under a hydrostatic stress field. In the solutions, the stiffness and installation times of the liners are accounted for. To simulate realistically the process of tunnel excavation, a time-dependent excavation process is considered in the development of the solutions, assuming that the radius of the tunnel grows from zero until its final value according to a time-dependent function to be specified by the designers. The integral equations for the supporting pressures between rock and first liner are derived according to the boundary conditions for linear viscoelastic rocks (unified model). Then, explicit analytical expressions are obtained by considering either the Maxwell or the Boltzmann viscoelastic model for the rheology of the rock mass. Applications of the obtained solutions are illustrated using two examples, where the response in terms of displacements and stresses caused by various combinations of excavation rate, first and second liner installation times, and the rheological properties of the rock is illustrated. 相似文献
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基于湿度应力场理论,推导了考虑膨胀应力和剪胀特性的圆形隧道开挖后围岩力学响应的弹塑性解。将隧道软弱围岩遇水膨胀现象视为湿度-应力耦合过程,基于Fick第二定律,推导了圆形隧洞围岩内湿度扩散非稳态解。采用非关联流动法则,获得了隧道高膨胀势区的应力和位移解答。以两种不同质量岩体开挖的隧洞为例,分析了膨胀围岩应力和变形的影响因素。结果表明,考虑膨胀应力（取决于围岩含水率变化和湿度膨胀系数）时,塑性区扩大,松动圈厚度增加,应力收敛变慢。当膨胀应力增大到一定程度时,塑性区将出现拉应力区。膨胀岩隧洞开挖遇水作用,膨胀应力增加的围岩变形远大于地应力引起的围岩变形。同时,应力剪胀对膨胀性围岩的变形影响不容忽视,尤其是在支护抗力较小的情况下,洞壁处径向位移增加显著。 相似文献
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Seyed Erfan Saberhosseini Reza Keshavarzi Kaveh Ahangari 《Arabian Journal of Geosciences》2017,10(6):152
One of the crucial consequences of steam assisted gravity drainage (SAGD) process is abnormal reservoir uplifting under thermal steam injection, which can significantly influence the reservoir rock deformation, specifically thin bed reservoirs and causes intensive failures and fractures into the cap rock formations. A thorough understanding of the influences of rock thermo-mechanical properties on reservoir uplifting plays an important role in preventing those aforementioned failures within design and optimization process in SAGD. In addition, coupling of reservoir porous medium and flowing of specific fluid with temperature as an additional degree of freedom with initial pore pressure and in-situ stress condition, are also very challenging parts of geomechanical coupled simulation which would be clearly explained. Thus, a fully coupled thermo-poro-elastic geomechanical model with finite element codes was performed in ABAQUS to investigate the role of rock thermo-mechanical parameters on reservoir vertical uplift during steam injection. It is clearly observed that, any increase in rock thermo-mechanical properties specifically rock’s thermal properties such as specific heat, thermal expansion, and formation’s thermal conductivity, have significant influences on reservoir uplift. So by coupling the temperature as an additional degree of freedom with the coupled pore-fluid stress and diffusion finite element model of SAGD process, the more realistic simulation will be conducted; hence, the errors related to not having heat as an additional degree of freedom will be diminished. In addition, Young’s modulus and specific heat are the rock thermo-mechanical parameters which have the maximum and minimum effects on the reservoir uplift, respectively. 相似文献
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The use of yield in supports to control the final loading that develops upon a support system has been one of the most important deformation control techniques used by tunnelling engineers, both historically and currently. Successful use of this approach requires a thorough understanding of the process of rock–support interaction as it is an approach that can fail dramatically if incorrectly applied. There is a fine line between the yield support technique improving the conditions, and the approach resulting in the development of a large area of failed rock, which could ultimately be detrimental. The relationship between the support action and the rock has historically been studied using analytical approaches with the application of significant simplifying assumptions.This paper presents a new approach, where a state-of-the-art numerical model is run repeatedly to develop rock–support interaction curves. This has the advantage of allowing more realistic tunnel geometry, stress states and ground conditions to be simulated. It does, however, use the familiar output form of the relatively simple rock–support interaction curve as opposed to complex and voluminous graphics. Its disadvantage lies in the considerable number of computer runs required to develop the full solutions. Computer software has, however, been written to automate much of this process using a programming language within the modelling package.The analysis approach has been further improved by plotting not one rock–support interaction curve but a whole family of curves representing variations in the rock mass quality of the assumed ground, since this is the most variable of the input parameters for most tunnelling situations. This form of output allows engineers to study the practical range of yield they may require for their rock conditions and also to define at what rock mass quality they can expect the yielding approach to cease to be an effective strategy. This new approach has been presented on a test case history with idealized rock mass properties to illustrate the approach. However, it is an approach that can be specially tailored to any set of rock conditions, tunnel geometry or stress. 相似文献
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地震作用下预应力锚索加固危岩体的动力响应分析 总被引：2，自引：0，他引：2
针对预应力锚索加固危岩体的特点,以某危岩体加固工程的3个典型工程剖面为实例,通过对不同动荷载作用下预应力锚索加固的危岩位移场、应力场分布特征的数值模拟计算,揭示了预应力锚索加固危岩体在地震作用下的动态响应和变化规律。分析结果表明,随着地震动峰值加速度（PGA）、反应谱特征周期（Tg）的增大,被加固危岩体的位移和应力值明显增大,应力集中区的范围扩大,围岩损伤的可能性增加,稳定性降低。其成果为危岩体抗震加固与减灾提供理论基础和实践依据。 相似文献
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甘肃省关山隧道是一条受高地应力影响的大埋深硬脆性闪长岩铁路隧道,位于青藏高原东北缘,构造活跃,运动速率较大,且方向变化显著的六盘山挤压隆升构造区。在隧道开挖过程中围岩变形破坏现象明显,围岩等级低于前期岩体质量分级,表现出强烈的岩体质量劣化和各向异性。针对该问题,除了采用矿物成分和微结构分析寻找原因,还通过现场结构面统计分析对围岩质量劣化和各向异性进行描述,同时运用自行研发的钻孔电视进一步分析开挖前后一定时间间隔内围岩的渐进式变形和破坏。钻孔电视试验结果表明,尽管闪长岩作为一种硬脆性岩体,单轴抗压强度（UCS）高于现场地应力值,但其变形和破坏却普遍发生,开挖过程中新生裂隙迅速发育,原先在高地应力下闭合的裂隙也会重新张开和发展,围岩劣化,稳定性降低。为了进一步分析围岩的变形破坏过程,设计了变压力大小和方向的单轴抗压试验,试验中闪长岩的单轴压力值低于单轴抗压强度,试验结果与钻孔电视试验观测结果吻合,证明了在开挖引起的地应力剧烈变化条件下硬脆性闪长岩结构劣化,存在变形破坏的可能性。在大埋深高地应力条件下,除了岩体的各向异性,地应力的变化也是硬脆性围岩稳定性的重要考量因素。 相似文献
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S. Y. Wang S. W. Sloan S. G. Fityus D. V. Griffiths C. A. Tang 《Rock Mechanics and Rock Engineering》2013,46(5):1165-1182
Rock is a heterogeneous geological material. When rock is subjected to internal hydraulic pressure and external mechanical loading, the fluid flow properties will be altered by closing, opening, or other interaction of pre-existing weaknesses or by induced new fractures. Meanwhile, the pore pressure can influence the fracture behavior on both a local and global scale. A finite element model that can consider the coupled effects of seepage, damage and stress field in heterogeneous rock is described. First, two series of numerical tests in relatively homogeneous and heterogeneous rocks were performed to investigate the influence of pore pressure magnitude and gradient on initiation and propagation of tensile fractures. Second, to examine the initiation of hydraulic fractures and their subsequent propagation, a series of numerical simulations of the behavior of two injection holes inside a saturated rock mass are carried out. The rock is subjected to different initial in situ stress ratios and to an internal injection (pore) pressure at the two injection holes. Numerically, simulated results indicate that tensile fracture is strongly influenced by both pore pressure magnitude and pore pressure gradient. In addition, the heterogeneity of rock, the initial in situ stress ratio (K), the distance between two injection holes, and the difference of the pore pressure in the two injection holes all play important roles in the initiation and propagation of hydraulic fractures. At relatively close spacing and when the two principal stresses are of similar magnitude, the proximity of adjacent injection holes can cause fracturing to occur in a direction perpendicular to the maximum principal stress. 相似文献
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The process of creating man made or “cut” slopes in rock invariably leads to stress relief within the rock mass which in turn induces a certain degree of fracturing and disturbance. The level of disturbance can be particularly significant when the slope is formed using blasting techniques. However, the effects of this disturbance on the overall rock slope stability have not been investigated thoroughly in the current literature. In order to account for rock mass disturbance during construction, a disturbance factor has been included in the Hoek–Brown failure criterion [1]. This paper uses finite element upper and lower bound limit analyses to estimate rock slope stability based on the Hoek–Brown failure criterion whilst including the effect of rock mass disturbance. A rigorous set of analyses have been performed where the level of disturbance is considered as constant or linearly varying throughout the slope. The results are then compared to a number of reported case histories for verification purposes. From the results of this study, the disturbance factor was found to have significant influence on the rock slope stability assessment, especially for poorer quality rock masses. Hence, cautious engineering judgement must be exercised when estimating the level of disturbance. In addition, utilising stability charts to estimate the stability of cut rock slopes without considering the rock mass disturbance may lead to significant overestimations. 相似文献
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针对煤层注水防尘过程中注水压力设置不合理、注水渗流效果差等问题,采用CT扫描技术与RFPA软件相结合的方法,构建了可以表征注水煤岩体内部孔裂隙结构的三维细观非均匀渗流损伤数值模型。通过对经过CT三维重构的煤岩模型进行不同注水压力的渗流损伤模拟,研究了煤层注水压力对煤样的渗流破坏、渗透率演化及声发射特性变化的影响;并通过对重构的煤岩模型进行缩放处理,研究了煤岩尺寸对煤样的渗流破坏和声发射变化的影响。研究结果表明：在煤样微观裂隙扩展过程中,随着注水压力的递增,煤样损伤单元数、渗流运动的渗流场分布范围、渗透率、声发射数目和能量总体呈上升趋势,局部范围内有波动发生,发生波动的原因是由于渗流运动的渗流场与煤样裂隙内部应力场发生临界反应,致使煤样破坏单元位置发生改变;煤样渗透率由3.82×10−5 μm2上升至0.314 μm2,孔隙率由5.45%上升至48.45%,揭示了煤岩体裂隙总体上随注水压力增大而不断扩展贯通,局部上随注水压力增大而扩展趋势有所下降的影响规律;随着煤样尺寸的增加,注水破坏后煤样的孔隙率呈现先下降后逐渐平稳的趋势,声发射特性变化趋势正好与之相反,表明煤样的尺寸对注水煤岩渗流破坏有显著影响,但当煤样尺寸超过40 mm时,煤样尺寸对注水煤岩渗流破坏的影响趋于稳定。CT扫描技术与RFPA软件相结合的方法能够有效模拟注水煤岩的裂隙渗流扩展行为。 相似文献
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通过轮廓法追踪岩石裂纹扩展轨迹,将其嵌入ABAQUS扩展有限元（EFE）平台,对单轴压力下裂隙试件受压过程进行了模拟验证,裂纹起裂扩展效果良好。以此为平台,将推导得到的弧形裂纹应力强度因子嵌入其中,以最大周向拉应力准则为开裂准则,认为当其大于岩体断裂韧度时,硐室围岩体内初始裂纹将开始扩展。在此基础上,以发现分区破裂现象的圆形隧道模型试验为背景开展了分区破裂的数值模拟试验。模拟结果发现,深部巷道围岩出现了3~4层破裂分区,证实深部巷道围岩存在分区破裂现象。将数值模拟结果与模型试验完成后模型围岩破坏状态对比,发现二者破裂区分布特征基本一致。数值模拟结果表明,EFEM方法在处理复杂岩体裂纹问题方面的有效性。 相似文献
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The influence of the intermediate principal stress on rock strength has been studied comprehensively by previous researchers. However, the reason why rock strength firstly increases and subsequently decreases with the increase of intermediate principal stress is still unclear. In this paper, the mechanism of the intermediate principal stress effect on rock failure behaviour is revealed through a numerical method using the EPCA3D system (Elasto-Plastic Cellular Automaton). In this study, both homogeneous and heterogeneous rocks are considered. The heterogeneity of a rock specimen is modelled by introducing Weibull's statistical distribution. Two criteria, i.e. the Drucker–Prager and Mohr–Coulomb models, are used to determine whether a meso-scopic element in the rock specimen is in a failure state or not during the polyaxial stress loading process. The EPCA3D simulation reproduces the typical phenomenon of the intermediate principal stress effect that occurs in some rock experiments. By studying the EPCA3D simulated acoustic emission and complete stress–strain curves illustrating failure initiation, propagation and coalescence in the failure process of rocks, the essence of the intermediate principal stress effect is tracked. It is concluded that the heterogeneous stress distribution induced by the natural heterogeneity of rocks and the effect of the loading platen are two of the reasons producing the intermediate stress effect. Studies indicate that a moderate intermediate principal stress delays the onset of local failure, which in turn leads to an increase in the rock strength. However, once the intermediate principal stress reaches a certain value, local failure will be formed through the application of the intermediate principal stress. It is the number of failed elements in the pre-peak region that determines whether the rock strength decreases or not. The extent of rock strength reduction when the intermediate principal stress reaches a certain value is lessened with the increase in the minimum principal stress. 相似文献
14.
Wenxue Wang Tong Jiang Boris Faybishenko Zhongfu Wang Wei Hu Qingjie Zhao 《Geotechnical and Geological Engineering》2016,34(5):1525-1537
In situ measurements of deformations, stresses, and closure of fractures, affecting water inflow following coal mining, are challenging due to the inaccessibility of fractured rock. In this paper, the authors studied the closure process of the fractured rock mass with the cover stress re-establishment based on a theoretical analysis and a scale model testing. A quantitative analysis is used to study the fracture distribution in the fractured zone. A function to describe a fracture aperture distribution in the fractured zone is proposed, which takes into account the curvature and thickness of the fractured rock. The theoretical analysis and a scale model testing both indicate that the cover stress re-establishment with mining distance increasing and the relationship between the fracture closure and cover stress re-establishment both satisfy a logarithmic function. The scale model test also shows the following features: (1) the fracture ratio (which is the fracture area divided by the total area of fracture and intact rock with a unit width in the vertical or horizontal direction) in the lower part of the fractured rock mass is greater than that in the upper part; (2) the initially fast decreased of fracture ratios is then followed by a slower decrease during the cover stress re-establishment process; (3) in the upper part of the rock mass, the vertical directional fractures with small apertures are being closed with cover stress re-establishment, which indicates an increase in the water resistance reducing the seepage from these parts of the fractured zone. This study improves the general understanding of the fracture closure process and cover stress re-establishment in the fractured rock mass after coal mining ceased, and provides a theoretical basis for water resource protection in case of underground coal mining. 相似文献
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Determining anisotropic deformation surrounding underground excavations for tunnels is an intuitional task that involves many difficulties due to the inherent anisotropies in the strength and deformability of natural rocks. This study investigates joint-induced anisotropic deformation surrounding a tunnel via a numerical simulation that accounts for the mechanical behavior of intact rock, the orientations of joint sets, and the mechanical behavior of joint planes; this numerical simulation can model the complete stress–strain relationship with anisotropic rock mass characteristics. Simulation results demonstrate that the well-known excavation-induced stress variation–decrease in the radial component and increase in the tangential component–decrease shear strength and increase shear stress for the joint plane tangential to the tunnel wall, resulting in joint sliding failure and considerable shear deformation. This joint sliding failure and significant shear deformation account for the joint-induced anisotropic deformation surrounding a tunnel. When a rock mass has two joint sets with unfavorable joint orientations, the area with joint sliding failure can deteriorate mutually, resulting in large anisotropic deformation. Additionally, for a rock mass containing three joint sets with well-distributed orientations, joint sliding in various joint sets and associated stress variations can counter balance each other, resulting in less anisotropic deformation than those of rock masses containing one or two joint sets. 相似文献
17.
巷道开挖围岩能量释放与偏应力应变能生成的分析计算 总被引：1，自引：0，他引：1
巷道开挖,围岩能量释放,同时在围岩中产生偏应力。围岩应力是原岩应力与偏应力的叠加,偏应力或偏应力能控制岩体破坏。在静水压力 和岩体体积应变为0的条件下,利用文[1]在弹性、非线性软化本构模型导得的巷道围岩应力分布表达式,用重积分计算了围岩弹性区和软化区中的偏应力应变能 ,证明了 可以简捷地用地应力 关于巷壁位移 做一次积分再乘巷壁周长的途径来得到,阐述了该计算途径的原理。巷道开挖过程围岩释放的能量等于围岩压力 关于 的积分乘巷壁周长。由此,可通过 ~ 曲线、 ~ 曲线所围面积的几何形式,表示围岩偏应力能、围岩弹性能释放量随 变化的情况。所得研究结果可以深化围岩由于开挖产生的力学响应及挖成后围岩工况规律的认识。 相似文献
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干热岩水压致裂过程中低温诱导热应力与注入水压共同影响裂缝的萌生与扩展。首先通过THM耦合分析了低温压裂液注入过程中注入水压与热应力的相互作用及其对裂缝萌生的影响,随后建立描述岩石细观结构的THMD耦合模型对热应力影响下高温岩石水压致裂过程进行初探。结果表明：低温压裂液注入高温岩石产生的热应力包括岩石自身温度梯度形成的热应力与岩石颗粒非均匀膨胀导致的热应力,并在井筒周围呈现为拉应力。高注入压力将抑制热应力导致的多裂缝萌生,井筒附近热应力的存在对注入压力也具有削弱作用。基岩温度升高,裂缝萌生阶段更多裂缝在井筒附近起裂,缝网沿最大地应力方向的扩展速度减慢,但改造规模增加,同时多裂缝的存在也使得裂缝延伸压力增加。 相似文献
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岩体的声学特性与应力状态和破坏程度密切相关,通过岩体声学特性的变化来分析岩体应力状态进而评价工程稳定性是一种行之有效的工程措施。针对砂岩开展了单轴压缩试验,并在加载过程中同步进行3个方向的声波测试,获得了砂岩加载过程中3个不同方向声波波速与应力的演化规律。试验结果表明：随着应力的增加,轴向波速逐渐增大,横向波速表现出先增后减的趋势。考虑到不同方向声波测试结果的差异性,采用含不同倾角裂隙的石膏试样进行声波试验。结果表明,当裂隙方向与声波传播方向一致时,波速最大,与声波传播方向垂直时,波速最小;此外,为分析岩样波速与应力状态的相关性,建立了波速与体应变的关系,结果表明,随着体应变的增加,平均波速逐渐增大,在体应变达到最大值附近时,平均波速达到最大值,在体应变下降阶段,波速开始下降;根据轴向波速与应力的变化规律,得到了应力与波速的指数函数拟合公式,据此可以通过现场测试获得的波速预测现场岩体的应力范围,进而评价工程岩体稳定性。 相似文献
20.
This paper evaluates the existing equivalent medium methods for jointed rock mass and further develops the equivalent viscoelastic medium method proposed by the authors. The advantages and limitations of different equivalences to the discontinuous rock mass are discussed. Theoretical derivation of stress wave propagation through the equivalent viscoelastic medium is carried out by adopting the Fourier transformation method, and the parameters of the equivalent viscoelastic medium method are determined analytically. The frequency dependence and the wave attenuation phenomenon can be properly described when the imaginary terms of the complex moduli of the rock mass are included. The results show that the equivalent viscoelastic medium method is able to predict the effective velocity and the stress wave transmission coefficient in a rock mass more accurately than the conventional effective elastic moduli methods. An example of the stress wave propagation through rock mass with parallel joints shows that the equivalent viscoelastic medium method is promising and worthy to be further explored for application in practical rock engineering problems. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献