共查询到20条相似文献，搜索用时 31 毫秒
1.
Avi Dutt M. S. Saini T. N. Singh A. K. Verma R. K. Bajpai 《Environmental Earth Sciences》2012,66(8):2327-2341
In our study, a coupled hydrologic-mechanical analysis is done of the excavation damaged zone, before the emplacement of nuclear waste. This is followed by a coupled thermal-hydrologic-mechanical analysis to evaluate the impact of nuclear waste repository in porous water containing rock mass. This analysis has been under taken in accordance with the Indian reference disposal system. The paper considers the changes in pore pressure and stresses due to excavation of disposal holes. A critical study of rock mass permeability, porosity, thermally induced stresses, strains, and temperature distribution after the emplacement of nuclear spent fuels in disposal holes has also been done. Coupling to the mechanical constitutive equations is done via ??effective?? normal strain rates. 相似文献
2.
Numerical study of the performance of tunnel plugs 总被引：1，自引：0，他引：1
High axial flow rates within and along tunnels, excavated for deposition of high level nuclear waste, may increase the transport capacity of potential escape routes for radionuclides that have been released to the buffer surrounding the waste canisters, or to the tunnel backfill materials, from leaking fuel canisters. High flow rates may be found if the tunnel interior has a high permeability, either initially due to the composition of the backfill material or at later times due to degradation of low permeability backfill material components. If a disturbed rock zone, a DRZ, of increased permeability was created as a result of direct damage done to the wall region during tunnel excavation, this zone may contain additional possible escape routes. Low-permeability tunnel plugs, keyed into slots cut in the rock walls, have been suggested as means of reducing axial flow rates. This paper deals with different aspects of such tunnel-plug systems. A preliminary estimate of the potential for tunnel plugs to reduce axial flow rates is made using analytical expressions. A number of numerical techniques are employed to investigate the hydraulic, mechanical and hydromechanical performance. These include μFLOW (FEM flow calculations), FLAC (finite difference mechanical calculations) and 3DEC (distinct element mechanical calculations). The mechanical calculations concern the mechanical stability in the rock surrounding the slot and permeability changes in that rock caused by stress redistribution. The results show that the effects of tunnel plugs are very significant in most cases. A discussion on the validity of the results and the applicability of the used methods is provided. 相似文献
3.
Elastic Solution for Deep Tunnels. Application to Excavation Damage Zone and Rockbolt Support 总被引：1，自引：1，他引：0
A. Bobet 《Rock Mechanics and Rock Engineering》2009,42(2):147-174
Summary A new formulation is presented for deep circular tunnels in rock with cylindrical anisotropy. The formulation is an exact
solution since it satisfies equilibrium, strain compatibility, and the anisotropic constitutive model. Complete solutions
have been found for two scenarios: tunnel with excavation damage zone, and tunnel with rockbolt support. The solution is based
on the assumption of a deep, circular tunnel in a medium with two homogeneous zones: an inner zone surrounding the tunnel,
which is either isotropic or anisotropic, and an outer zone, for the remainder of the medium, which is isotropic. Plane strain
conditions, elastic response of rock, rockbolts and support, and simultaneous excavation and support installation are also
assumed. For tunnels surrounded by an excavation damage zone with reduced rock properties, the tangential stresses and the
radial deformations at the tunnel wall are very sensitive to both the magnitude of stiffness reduction of the damaged rock
and the size of the damaged zone. The effect of the rockbolts on the rock is approximated by treating the rockbolt-rock composite
as a material with cylindrical anisotropy with stiffnesses related to the properties of the rock and rockbolts, and spacing
of the rockbolts. Comparisons between the analytical solution and a numerical method show small differences and provide confidence
in the approach suggested. 相似文献
4.
The elasto-visco-plastic analysis for rock displacement of the foundation pit of a water power plant 总被引：3，自引：0，他引：3
SummaryThe Elasto-Visco-Plastic Analysis for Rock Displacement of the Foundation Pit of a Water Power Plant In this paper a method used in the elasto-visco-plastic analysis is proposed. It has been employed for deformation analysis of the foundation pit of a large water power plant in China.The back analysis of this rock engineering problem shows that the relief of the rock initial stresses due to excavation and the rheological properties of the weak intercalations and the rock masses as well are the main factors which caused the large deformation of the foundation pit.The results from the calculations are coincided fairly well with the data measured and observed in situ.With 16 Figures 相似文献
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6.
现有基坑相关研究主要关注土方开挖过程引起的变形,认为围护结构变形起点是土方第1次开挖。然而,一些工程实测表明,基坑开挖前降水阶段即可引起围护结构及周边地层发生厘米级的变形。显然,未考虑开挖前变形的基坑监测数据将低估基坑施工的环境效应。为了研究基坑开挖前降水引发基坑变形的机制,开展了室内模型试验,对基坑开挖前降水过程进行了缩尺精细化模拟。通过微型降水井的设置与调控,模型试验真实再现了实际基坑降水过程中井流效应对围护结构受力变形的影响。试验过程中发现,随着降水的进行,坑外降水漏斗不断扩展,围护结构悬臂式侧移及坑外拱肩式地面沉降也随之产生。另外,降水导致墙前水压力明显减小,并诱发墙前侧向总压力重分布（以减小为主）,围护结构为此发生指向坑内的悬臂式运动以寻求新的受力平衡,并通过墙后土体损失诱发坑外地层变形。 相似文献
7.
某水力枢纽基坑开挖过程渗流耦合数值模拟 总被引：1，自引：0，他引：1
岩土工程中存在多种耦合作用,在水利水电工程中,渗流场与应力场的耦合是最重要的。以某水利枢纽厂房基坑开挖为工程背景,比奥固结理论为理论基础,莫尔-库仑准则为土体屈服判据,对基坑开挖过程中渗流耦合进行了数值模拟。计算结果显示：回填后的应力略大于开挖过程中的应力,沉井附近出现一定程度的应力集中。回填前后塑性区变化不大且范围较小,因而土体的屈服破坏不是该工程的重点。由于土体渗透系数大,厂房区地下水位高,基坑开挖过程中渗水量较大,回填后沉井及基坑底部防渗底板的防渗效果显著,因而在基坑开挖过程中防渗排水是该工程的重点问题。 相似文献
8.
开挖卸荷状态下深基坑变形特性研究 总被引：1，自引：0，他引：1
深基坑开挖时因为卸荷作用会引起土体强度一定程度的降低,土体强度的降低会引起支护结构上土压力的变化,利用卸荷前土体强度指标进行土压力计算势必会小于实际情况,从而导致土体及支护结构变形计算值与实测值有一定的偏差。在深基坑开挖时,仅采用施工监测等手段进行事中控制是不够的,必须预先对变形值的发展规律做出模拟和预测。为探索深基坑开挖时,卸荷作用对基底土体和侧向土体强度特性和变形特性的影响规律,结合天津富力响锣湾大型基坑开挖,对开挖过程中土体基底回弹情况、支护结构以及周边土体的变形情况进行了全过程监测,利用试验结果数据计算出天津市富力响锣湾大型基坑开挖项目的卸荷强度参数,为后续数值模拟计算参数的选取提供了依据;利用ABAQUS有限元软件建立了三维数值模型,分别采用原状土的强度参数和卸荷参数对开挖过程中土体基底回弹、支护结构以及周边土体的变形情况进行了模拟,研究了两种情况下土体基底回弹、支护结构以及周边土体的变形规律,并将有限元模拟结果与监测结果进行了对比。研究发现,本工程土体卸荷后的扰动区在基底以下3～4 m范围,强度折减可达到20%～35%,根据卸荷比确定了周边土体强度折减为10%～15%;有限元模拟结果与实测值基本一致。通过分析可以看到,考虑基坑开挖卸荷作用是符合工程实际情况的,因此,建议在深基坑开挖设计时考虑土体的卸荷效应。该分析方法可为同类深基坑设计提供参考。 相似文献
9.
Poro‐mechanical and thermo‐mechanical processes change the fracture aperture and thus affect the water flow pattern in the fracture during the cold water injection into enhanced geothermal systems (EGS). In addition, the stresses generated by these processes contribute to the phenomenon of reservoir seismicity. In this paper, we present a three‐dimensional (3D) partially coupled poro‐thermoelastic model to investigate the poroelastic and thermoelastic effects of cold water injection in EGS. In the model, the lubrication fluid flow and the convective heat transfer in the fracture are modeled by the finite element method, while the pore fluid diffusion and heat conductive transfer in the reservoir matrix are assumed to be 3D and modeled by the boundary integral equation method without the need to discretize the reservoir. The stresses at the fracture surface and in the reservoir matrix are obtained from the numerical model and can be used to assess the variation of in situ stress and induced seismicty with injection/extraction. Application of the model shows that rock cooling induces large tensile stresses and increases fracture conductivity, whereas the rock dilation caused by fluid leakoff decreases fracture aperture and increases compressive total stresses around the injection zone. However, increases in pore pressure reduce the effective stresses and can contribute to rock failure, fracture slip, and microseismic activity. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
基于卸荷岩体的理论和方法,对大岗山水电站坝肩边坡进行研究。以大型通用有限元程序ADINA为计算平台,对比分析坝肩边坡卸荷后,不同地震加速度及不同锚固长度和锚固吨位在卸荷条件下关键点的位移和应力以及塑性区的变化规律,认为边坡开挖变形由两部分组成,一部分为卸荷回弹,另一部分是由于大吨位锚索施加后产生的朝向坡内的压缩变形。研究表明,由于锚索穿过V岩体底部界线,在可能的滑坡剪出口形成强大的阻滑键,增加锚索长度或吨位均可有效地减小坝肩塑性区,地震加速度为0.1g和0.15g时,在各加固吨位下均可能形成塑性区的贯通;在不同的地震加速度下,受不同锚固长度和锚固力影响,不同关键点处水平向位移呈现线性变化和非线性变化,非线性关系中的拐点应重点关注;若要减少岩体塑性区,相同比例下增大锚固长度效果更好。为了有效减少在高地震烈度时边坡塑性区的发育,建议采用增加120%的锚固长度。 相似文献
11.
锦屏二级水电站引水隧洞爆破开挖损伤特性研究 总被引：1，自引：0，他引：1
爆破开挖导致的围岩损伤是围岩稳定性的重要影响因素。采用数值分析及现场检测的方法研究了锦屏二级引水隧洞岩体爆破开挖损伤特性。数值模拟结果表明,引水隧洞开挖引起的围岩应力重分布是围岩损伤的主要原因,爆炸荷载和应力重分布的耦合作用将增大引水隧洞围岩损伤区范围,增大的损伤深度可达1.5 m,考虑开挖荷载瞬态卸荷动态损伤效应的损伤区范围最大,较单独考虑围岩地应力准静态重分布所导致的损伤深度可增大1.9 m,平均损伤深度增大近1倍。现场检测成果较好地验证了数值模拟结果,表明爆破开挖可显著增大围岩的损伤范围。锦屏二级水电站引水隧洞开挖过程中,不可忽视爆炸荷载及开挖瞬态卸荷对围岩的损伤作用。 相似文献
12.
M.A. Coulthard 《Geotechnical and Geological Engineering》1999,17(3-4):373-385
Numerical modelling has been used to investigate a variety of problems in underground mining and tunnelling: subsidence induced by longwall coal mining; stresses generated when an open stope is filled cemented backfill and the stability of exposures created during subsequent mining of adjacent stopes; the interaction of two tunnels; and the effects of under-mining a pre-existing tunnel and shaft. In each case, results from nonlinear stress analyses can be used to guide the design of excavations and rock support mechanisms. 相似文献
13.
软岩浅埋隧道施工工法比选 总被引：2，自引：0，他引：2
目前在高速公路软岩浅埋隧道施工中均不同程度地出现了围岩坍塌、地表产生大面积沉降等问题。广福隧道某浅埋段,地质条件复杂,断面大、岩性差,受构造影响比较严重,而且顶板厚度比较薄,易发生坍塌、冒顶现象。为确保浅埋段隧道的施工安全,尽量减少隧道开挖引起的地层沉降和围岩变形,采用FLAC3D对4种施工工法全断面法、短台阶法、单侧壁导坑法和双侧壁导坑法进行模拟,分析了4种工法下地表沉降、隧道围岩周边位移和塑性区的变化特点,选出一种技术可行、经济合理的施工工法,得出一些有意义的结论。 相似文献
14.
根据流固耦合理论,采用有限元数值模拟的方法,针对承压水体上采煤过程中断层参数(断距、倾角)对煤层、围岩的应力、变形和水压力变化的影响进行了模拟分析,探讨了存在断层时突水的机理和可能的突水点位置,并定量分析了防水煤柱的预留距离。得出以下结论:(1)当存在正断层时,多发生断层破坏型突水,而底板破坏型突水发生的几率较小;(2)突水性质和突水发生位置受断层断距和倾角的影响不大,煤层和采煤工作面附近的底板围岩都可能成为突水涌出点;(3)随着断层断距和倾角的增加,防水煤柱的合理留设距离应随之增大。以上结果可为实际矿井采煤防突水设计提供参考。 更多还原 相似文献
15.
Three-Dimensional Back-Analysis of an Instrumented Shallow Tunnel Excavated by a Conventional Method
Mohamed Nabil Houhou Fabrice Emeriault Émilie Vanoudheusden 《Geotechnical and Geological Engineering》2016,34(4):1101-1117
The excavation of a shallow tunnel induces deformations of the soil volume in the vicinity and above the tunnel and consequently on the nearby buildings. The range of these deformations depends among other on the geological conditions, the geometry of the tunnel, and the excavation method. In this context, this research focuses on the 3D numerical modeling of a shallow tunnel instrumented during its construction, located on the Toulouse (France) subway line B for which the excavation has been carried out in a conventional manner in an over consolidated molassic geological context. The objective of this analysis is to estimate the tunnel behavior in terms of vertical and horizontal movements of the surrounding soil and the deformations of the existing buildings. The explicit finite differences numerical code FLAC3D is used to model the various implementation phases of the work where the fluid–soil interaction is taken into account through an undrained coupled analysis. The results of this 3D model are compared to those of the in situ measurements in order to validate the geotechnical characteristics of the molasses. The latter are a useful basis for the back-analysis of the different monitoring sections implemented in areas where the tunnel excavation is made by TBM with pressurized front. 相似文献
16.
The deformation of a deep foundation pit in Ulanqab city was analyzed by in situ monitoring and numerical simulation data. First, a limit equilibrium method was used to evaluate the stability of foundation pit under non-supporting and ribbed plate anchored retaining wall support. The results show that the ribbed plate anchored retaining wall support could control the soil deformation effectively in deep foundation pit. Additionally, a three-dimensional finite difference model of excavation zone and reinforcement structure was established using FLAC3D software to simulate the excavation of deep foundation pit. The simulation results were verified by monitoring field data. The simulation results show that all the bolts are in the tension state, and the maximum axial force is located at the end of the bolt, with a value of 46.4 kN. Foundation pit excavation is a continuous stress release process, making the rock and soil of side wall of foundation pit slide towards the free surface. The largest deformation is 4.0 mm, near the side wall of foundation pit, consistent with the deformation monitoring results.
相似文献17.
A plastic deviatoric model with hardening is developed on the basis of geomechanical tests performed in the saturated case on low permeable porous material such as argillite. This model is a generalized Mohr–Coulomb plastic criterion combined with a Drucker–Prager plastic potential and the hardening parameter is the plastic distortion. Three different hardening functions have been introduced on the basis of triaxial tests: an increase of friction angle, a decrease of cohesion after a threshold and a contractancy to dilatancy transition for volumetric plastic strain. This plastic model has been adapted to the partially saturated case. The effective stress is expressed thanks to the equivalent interstitial pressure π. Numerical results are presented for the excavation and monotonous ventilation of a deep cylindrical cavity. A first plastification due to excavation is followed by a second one due to desaturation. The extent of the non-saturated zone provokes an extent of a plastic zone in the rock mass. Analysis shows that the origin of the plastification can be found in the deviatoric stresses because mean effective stresses are compressive during drying. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
18.
隧道围岩非线性体积膨胀影响施工安全,如何正确评价隧道围岩塑性区域内扩容机制非常重要。多数研究从理论上推导深埋圆形隧洞应变软化围岩应力-应变场时仅采用恒定或线性变化剪胀模型,针对此不足,提出了一种基于有限差分法的分析方法,能够合理地考虑围岩非线性剪胀效应及其应变软化特性。利用已有的研究成果,验证了该方法的合理性,并进一步探讨了不同质量石灰岩与支护压力下剪胀系数在围岩塑性区域内的影响因素,比较了恒定与非线性变化剪胀模型下围岩变形的不同。结果表明:对于地质强度指标(GSI)较小、质量较差的岩体,塑性区域内主要由围压控制剪胀效应程度;恒定与非线性变化剪胀模型下围岩洞壁变形差别显著。 相似文献
19.
Mining backfill is commonly used in underground mines. A critical concern of this practice is to evaluate the pressures and total stresses in backfilled stopes to ensure a safe and economic design of barricades, constructed to retain the backfill. When a slurried backfill is placed in a mine stope, excess pore water pressure (PWP) can instantaneously generate and progressively dissipate. The dissipation of the excess PWP and consolidation lead to the development of effective stresses, which in turn lead to an arching effect in the backfilled stope. Until now, arching effect has been largely considered for stress estimation in dry or submerged backfill. The former corresponds to the final state at the end process of the drainage and consolidation of the backfill with a pervious while the latter with an impervious barricade. However, previous studies have shown that the most critical moment for the stability of barricades is during the stope filling. Therefore, the design of barricades requires a proper estimation of the pressure and total stresses during the filling operation. This in turn needs joint consideration of the arching effect and consolidation of the backfill. In this paper, a new solution is developed to evaluate the pressures and stresses in backfilled stopes during the filling operation of cohesionless backfill by considering the self-weight consolidation and arching effect. The proposed solution is validated by numerical modeling with Plaxis2D. It can thus be used to evaluate the pressures and stresses in backfilled stopes during the stope filling with an impervious barricade. 相似文献
20.
Jonny Rutqvist Ann Bäckström Masakazu Chijimatsu Xia-Ting Feng Peng-Zhi Pan John Hudson Lanru Jing Akira Kobayashi Tomofumi Koyama Hee-Suk Lee Xiao-Hua Huang Mikael Rinne Baotang Shen 《Environmental Geology》2009,57(6):1313-1324
This simulation study shows how widely different model approaches can be adapted to model the evolution of the excavation
disturbed zone (EDZ) around a heated nuclear waste emplacement drift in fractured rock. The study includes modeling of coupled
thermal-hydrological-mechanical (THM) processes, with simplified consideration of chemical coupling in terms of time-dependent
strength degradation or subcritical crack growth. The different model approaches applied in this study include boundary element,
finite element, finite difference, particle mechanics, and elasto-plastic cellular automata methods. The simulation results
indicate that thermally induced differential stresses near the top of the emplacement drift may cause progressive failure
and permeability changes during the first 100 years (i.e., after emplacement and drift closure). Moreover, the results indicate
that time-dependent mechanical changes may play only a small role during the first 100 years of increasing temperature and
thermal stress, whereas such time-dependency is insignificant after peak temperature, because of decreasing thermal stress. 相似文献