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1.
Around galleries excavated at depth in geological media, the creation of a damaged zone with significant irreversible deformation is generally unavoidable. In the case of a geological disposal system for high-level radioactive waste, the resulting change in the host rock properties in this damaged zone may potentially be important with respect to the long-term evolution and the performance of that system. In this context, predicting the extent of the so-called Excavation Damaged Zone (EDZ) and, possibly, the fractures’ network topology remains a challenge. This study is aimed to simulate numerically the extension of this zone at the large scale’s excavation, around the Connecting gallery (HADES URL, Mol, Belgium), in Boom clay host rock through analyzing the evolution of strain localization in shear bands mode. To realistically model the involved phenomena, the concrete lining is considered on the gallery wall highlighting its impacts on the evolution of convergence and EDZ around the gallery. The focus of the current paper is made on analyzing the coupled hydro-mechanical behavior of Boom clay host rock during and after the gallery excavation with respect to the evolution of localized shear bands around the gallery. This study is accompanied by the analysis of the contact mechanism on the interface between the clay massive and the lining. The obtained results reveal some interesting features regarding the contact phenomenon relatively to the evolution pattern of shear bands within the clay around the gallery. To assess the reliability of the proposed approach, a discussion on some in-situ observations during the gallery’s construction is also performed based on which a good agreement is found between the in-situ evidence and simulated results. 相似文献
2.
含有多层软弱夹层的开挖边坡具有坡体结构复杂、稳定性评价及治理难度大的特点。以黔西地区现场开挖高边坡为研究对象,建立室内物理试验模型,通过不同的工况开挖,呈现变形破坏演化过程,分析变形破坏模型及形成机理,确定失稳破坏范围。结果显示:开挖边坡裂隙产生由表及里,由上及下,由最初的陡倾短小裂隙扩展延伸,最终贯通,形成近似平行岩层的长大裂缝;缓坡度开挖变形破坏为浅表层,整体稳定性较好,失稳范围及规模较小;陡坡度开挖变形破坏规模大,稳定性较差,以滑移-拉裂深层失稳为主;浅层滑坡滑面以层间泥化夹层剪切为主,基本呈直线状;深层滑坡滑面以层间泥化夹层剪切以及陡倾裂隙组合形成阶梯状。该研究成果对于黔西地区的顺层开挖高边坡设计、稳定性评价、治理措施选择等具有重要的指导意义。 相似文献
3.
Hossein Mirmehrabi Mohammad Ghafoori Gholamreza Lashkaripour Sadegh Tarigh Azali Jafar Hassanpour 《Environmental Earth Sciences》2012,66(2):529-535
Occurrence of hydrogen sulfide gas (H2S) is one of the most important engineering geological hazards during tunneling. Its hazards and consequent challenges are
very difficult and costly to solve. During site investigation, one of the tasks for engineering geologists is prediction and
evaluation of the risk of H2S gas in the underground spaces. In this study, water conveyance tunnel of Aspar, which was excavated in H2S-bearing environments, is discussed. The tunnel is excavated in the hydrocarbon formations. Applied experiments suggest that
geological formations pertaining to hydrocarbon resources are crucial in formation and reservation of H2S gas. This paper briefly discusses hazards and geological sources of H2S, as well as remedial measures for decreasing the risks and problems in excavation of the tunnel. To predict the risk of
H2S gas in the underground spaces, it is possible to use some precursors such as: sulfur springs, organic traces, organic argillaceous
rocks, exposure of H2S odor from fresh surface of rock and smell of H2S during boreholes drilling. Controlling the inflow of groundwater into the excavation, diluting the concentration of H2S, training the personnel and utilization of some proper safety equipment have been used to mitigate risks and problems in
tunnel excavation. 相似文献
4.
泥质砂岩属于黏土岩,具有典型的遇水软化特征。在泥质砂岩富水地层中进行隧道开挖是地下工程的一个挑战性问题。研究了围岩软化与未软化条件下泥质砂岩地层中输水隧洞的稳定性和支护时间。首先,介绍了泥质砂岩遇水软化的力学试验结果;然后,采用基于Hoek-Brown强度准则的岩体参数评价方法,评估泥质砂岩在围岩软化与未软化条件下的力学参数;再后,以兰州水源地引水隧洞为依托工程,采用数值模拟方法对泥质砂岩隧洞软化与未软化工况的围岩稳定性进行了计算分析,得出泥质砂岩遇水软化对隧洞安全性存在显著影响;最后,采用位移收敛法,研究了泥质砂岩软化与未软化工况中,保障隧洞施工安全的合理支护时机。研究表明,泥质砂岩未软化工况中,可考虑隧道围岩初期支护在距掌子面4～5 m位置实施;而在泥质砂岩遇水软化工况中,初期支护建议在掌子面开挖后立刻支护。研究成果可为泥质砂岩地层隧洞的安全施工提供依据。 相似文献
5.
6.
The Callovo-Oxfordian claystone (COx) is considered as a potential geological formation to host an industrial radioactive waste repository in France. A detailed understanding of the thermo-hydro-mechanical (THM) behavior of the COx is a key issue for design of different repository structures and the safety calculations of the project. More particularly, numerical modeling of induced fracture networks around drifts excavated at the main level of the Andra’s Meuse/Haut-Marne Underground Research Laboratory (M/HM URL) and short and long term behavior of the COx around these drifts are of great interest. Several constitutive models have been developed/used in the framework of the R&D and simulation programs of Andra. A model benchmark exercise has been launched since 2012 to provide an overall view of the developed models regarding the in situ observations. In this view, two series of test cases, respectively at material point scale and at drift excavation scale are defined. Different kinds of constitutive models based on the elasto-visco-plasticity concept, continuum damage mechanics, the rigid block spring method and two-scale computational homogenized model (CHM) are used within this exercise. The obtained results show that accounting for material anisotropy and strain localization treatment techniques can improve the obtained results when elasto-visco-plastic models are used. Damage mechanics based approaches and methods accounting for discontinuities through discrete elements provide also interesting insights especially when fracturing processes must be modeled. However, more efforts are necessary to improve the robustness of these kinds of approaches in the complex context of COx response to excavation works. 相似文献
7.
Numerical Modelling of the Anisotropic Mechanical Behaviour of Opalinus Clay at the Laboratory-Scale Using FEM/DEM 总被引：1，自引：1，他引：0
Andrea Lisjak Bryan S. A. Tatone Giovanni Grasselli Tim Vietor 《Rock Mechanics and Rock Engineering》2014,47(1):187-206
The Opalinus Clay (OPA) is an argillaceous rock formation selected to host a deep geologic repository for high-level nuclear waste in Switzerland. It has been shown that the excavation damaged zone (EDZ) in this formation is heavily affected by the anisotropic mechanical response of the material related to the presence of bedding planes. In this context, the purpose of this study is twofold: (i) to illustrate the new developments that have been introduced into the combined finite-discrete element method (FEM/DEM) to model layered materials and (ii) to demonstrate the effectiveness of this new modelling approach in simulating the short-term mechanical response of OPA at the laboratory-scale. A transversely isotropic elastic constitutive law is implemented to account for the anisotropic elastic modulus, while a procedure to incorporate a distribution of preferentially oriented defects is devised to capture the anisotropic strength. Laboratory results of indirect tensile tests and uniaxial compression tests are used to calibrate the numerical model. Emergent strength and deformation properties, together with the simulated damage mechanisms, are shown to be in strong agreement with experimental observations. Subsequently, the calibrated model is validated by investigating the effect of confinement and the influence of the loading angle with respect to the specimen anisotropy. Simulated fracture patterns are discussed in the context of the theory of brittle rock failure and analyzed with reference to the EDZ formation mechanisms observed at the Mont Terri Underground Research Laboratory. 相似文献
8.
ABSTRACT The local site experience is a valuable component for the success of rock mass classification systems as tunnel design methods. The Ituango hydroelectric project is a very important source of information in order to evaluate the usefulness of the main rock mass classification systems. The objective of this research is to improve understanding of some important features of excavated rock mass, such as discontinuities, block size, shear strength and joint alteration, by analyzing some hundreds of data obtained during excavation cycle. The field study included a survey of exposures after drilling and blasting rounds. Rock mass classification and support measures for each type of terrain along 1400 m tunnel were performed. The rock mass classes could be better explained if shear strength, alteration or block size is calculated. The assessment of these data allows evaluating the block fall risk, improving support and liner. A local correlation between the RMR and Q system was also obtained. 相似文献
9.
10.
The understanding of the thermo-hydro-mechanical behaviour of a clay barrier is needed for the prediction of its final in situ properties after the hydration and thermal transient in a radioactive waste repository.
As part of the CEC 1990–1994 R&D programme on radioactive waste management and storage, the CEA (Fr), CIEMAT (Sp), ENRESA (Sp), SCK · CEN (B), UPC (Sp) and UWCC (UK) have carried out a joint project on unsaturated clay behaviour (Volckaert et al., 1996). The aim of the study is to analyse and model the behaviour of a clay-based engineered barrier during its hydration phase under real repository conditions. The hydro-mechanical and thermo-hydraulic models developed in this project have been coupled to describe stress/strain behaviour, moisture migration and heat transfer. A thermo-hydraulic model has also been coupled to a geochemical code to describe the migration and formation of chemical species.
In this project, suction-controlled experiments have been performed on Boom clay (B), FoCa clay (Fr) and Almeria bentonite (Sp). The aim of these experiments is to test the validity of the interpretive model developed by Alonso and Gens (Alonso et al., 1990), and to build a database of unsaturated clay thermo-hydro-mechanical parameters. Such a database can then be used for validation exercises in which in situ experiments are simulated.
The Boom clay is a moderately swelling clay of Rupellian age. It is studied at the SCK · CEN in Belgium as a potential host rock for a radioactive waste repository. In this paper, suction-controlled experiments carried out on Boom clay by SCK · CEN are described. SCK · CEN has performed experiments to measure the relation between suction, water content and temperature and the relation between suction, stress and deformation. The applied suction-control techniques and experimental setups are detailed. The results of these experiments are discussed in the perspective of the model of Alonso and Gens. The influence of temperature on water uptake was rather small. The measured swelling-collapse behaviour can be explained by the Alonso and Gens model. 相似文献
11.
西南某大型水电站拱肩槽边坡开挖的变形响应研究 总被引：1，自引：0，他引：1
对在复杂地质条件和高地应力环境下,高达近330m的人工岩石拱肩槽高边坡的研究,尤其是在大坡比、强开挖条件下所表现的变形响应规律的研究具有重要的理论与现实意义。论文通过大量现场跟踪施工的地质调查工作和利用丰富的监测资料的基础上,系统地研究了此类边坡变形响应的基本规律及特殊表现,得到了拱肩槽高边坡开挖过程中,边坡的变形与开挖过程有较强的同步性。变形主要受开挖卸荷影响;随开挖的进行,坡体的变形随开挖面的远离表现出总体衰减的特征等。开挖后的坡体的变形量较小,变形深度较浅,而且在开挖12~18个月后,变形趋于稳定。这些结论对类似边坡开挖及其稳定性的控制具有重要的借鉴意义。 相似文献
12.
The Tournemire underground laboratory is situated in a clay formation and consists of a disaffected railway tunnel and two perpendicular drifts. The paper presents modelling and 3D simulations of the hydraulic behaviour of the argillaceous formation around the works. Experimental measurements of porosity, permeability and specific storage coefficients allowed us to model the hydraulic properties of the shale. Numerical simulations are performed with the code CASTEM. Numerical results of hydraulic heads are compared to experimental measurements. Calculations show that the excavation of the tunnel and drifts has induced an hydraulic decompression of the indurated argillaceous formations. The zones of decompression are centred around the structures and extend depending on the values of hydraulic parameters such as permeability and specific storage selected in the model. Six years after the excavation of the drifts, the hydraulic steady state in the fractured zone is not yet reached. 相似文献
13.
A numerical investigation of the desaturation process at the argillaceous Tournemire site has been carried out. This desaturation
is initialized by the contact of the saturated rock with the ambient air in excavated openings. The used hydraulical model
is based on the Richards’ approximation for unsaturated one phase flow coupled with the deformation of a porous medium with
anisotropic linearly elastic behavior. In relation to the extent of the desaturated zone around an excavated opening, the
intrinsic permeability and the relative permeability have been identified to be the most important model parameters. The mechanical
deformation process itself, the seasonal influences and the tunnel lining are less important for the formation of the desaturated
zone. The comparison with measured saturation values bares some difficulties but indicates the principle capacity of the applied
finite element codes to simulate the desaturation process. The consideration of seasonal changes in humidity in the ambient
air results in a constantly recurring desaturation–resaturation cycle in the near field of the openings. This seasonally influenced
zone amount 1–2 m and is nearly independent from time and from a variation of model parameters within a reasonable range.
The possibility of material weakening in this zone is of special interest, since claystone is a potential host rock for the
disposal of radioactive waste. 相似文献
14.
Bertrand François Vincent Labiouse Arnaud Dizier Ferdinando Marinelli Robert Charlier Frédéric Collin 《Rock Mechanics and Rock Engineering》2014,47(1):71-86
Boom Clay is extensively studied as a potential candidate to host underground nuclear waste disposal in Belgium. To guarantee the safety of such a disposal, the mechanical behaviour of the clay during gallery excavation must be properly predicted. In that purpose, a hollow cylinder experiment on Boom Clay has been designed to reproduce, in a small-scale test, the Excavation Damaged Zone (EDZ) as experienced during the excavation of a disposal gallery in the underground. In this article, the focus is made on the hydro-mechanical constitutive interpretation of the displacement (experimentally obtained by medium resolution X-ray tomography scanning). The coupled hydro-mechanical response of Boom Clay in this experiment is addressed through finite element computations with a constitutive model including strain hardening/softening, elastic and plastic cross-anisotropy and a regularization method for the modelling of strain localization processes. The obtained results evidence the directional dependency of the mechanical response of the clay. The softening behaviour induces transient strain localization processes, addressed through a hydro-mechanical second grade model. The shape of the obtained damaged zone is clearly affected by the anisotropy of the materials, evidencing an eye-shaped EDZ. The modelling results agree with experiments not only qualitatively (in terms of the shape of the induced damaged zone), but also quantitatively (for the obtained displacement in three particular radial directions). 相似文献
15.
J.-F. Thovert V.V. Mourzenko P.M. Adler C. Nussbaum P. Pinettes 《Engineering Geology》2011,117(1-2):39-51
This paper deals with the reconstruction of a fracture network observed in an underground gallery of a tunnel buried in clay stones in Switzerland, below Mont Terri. The trace maps of the Gallery 04 and of the EZ-G niche of this site have first been digitized and used in various ways to characterize the data. The traces have been divided into two groups, i.e., the pre-existing faults in the gallery and the fractures of the excavated damaged zone (EDZ) in the niche. Each group has been analyzed individually. The number of data for the faults has turned out to be statistically significant, while it was very limited for the EDZ fractures. For both cases, the major statistical characteristics of the traces have been extracted and a reconstruction procedure developed and tested. A full example has been worked out; a gallery immersed in a reconstructed fractured porous medium has been meshed, and the electrical field created by a dipole at the wall calculated by solving the three dimensional Laplace equations in the fractures and in the porous medium. 相似文献
16.
江苏某抽水蓄能电站,上库主坝为混凝土面板堆石坝,由于上库防渗面板基础开挖量大,开挖料大多数为强风化粉砂质泥岩和强风化泥质粉砂岩,拟利用部分强风化中下部开挖料作为主坝填筑料,对于达到挖填平衡、保护环境、减少弃料及提高经济效益具有重要意义。为此对强风化岩石进行了岩石物理性质、抗压强度、压缩变形、矿物成份分析、化学分析等试验研究,同时进行了岩石干湿、变温多次循环疲劳物理力学特性试验,揭示了强风化岩石在干湿、变温循环条件下的变化规律,对于强风化岩石的可利用性及预测其长期稳定性提供了科学依据。 相似文献
17.
Numerical simulation of a discontinuous gallery lining's behavior,and its interaction with rock 
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下载免费PDF全文 Deep excavation in some geological media needs lining of the gallery. This could limit the extent of the so‐called excavation damaged zone and the resulting convergence of the material due to tunneling. Boom clay, the reference potential host rock in Belgium for disposal of high‐level radioactive waste, is one of these media for which lining of the gallery walls is essential. A correct simulation of the lining behavior in the course of the excavation process, where the rock comes into contact with the lining, and in the long term, remains a significant challenge in analysis of the whole coupled phenomena of rock in interaction with the lining. This study aims to numerically model the lining behavior. The main objective is to develop a model that could realistically simulate the behavior of a discontinuous lining made of concrete segments. We propose to numerically analyze the response of the blocks in contact with each other and in interaction with rock, with the use of zero‐thickness interface elements. To validate the developed model and a proposed approach, a particular analysis compares the obtained results with the available in situ measurements. This study then discusses the deficiency of the simplistic model that considers a continuous lining. In addition, regarding the contact mechanism on the interface between the rock and the lining, the obtained results demonstrate an interesting relation between the contact phenomena and the shear banding within the rock around the gallery. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
18.
In spite of the considerable area covered by argillaceous sedimentary rocks (comprising shales, mudrocks and siltstones) in Brazil and the number of engineering works associated with these materials, little is known about their geotechnical, physical, chemical, mineralogical and textural characteristics and the effects of weathering processes on them. This work presents results obtained in a research project aiming primarily at identifying degradation processes responsible for the weathering of some of these rocks in Brazil. The rocks under investigation come from two different parts of the country, each one related to a specific engineering problem and to different geoenvironments. The project involved a comprehensive laboratory testing program for basic characterization (chemical and mineralogical composition, index properties, etc.) and evaluation of durability characteristics of these rocks. The present paper describes the testing program carried out and discusses the results obtained. 相似文献
19.
Tetsuya Tokiwa Kimikazu Tsusaka Makoto Matsubara Taiki Ishikawa Daisuke Ogawa 《地学前缘(英文版)》2013,4(1):105-111
This paper focuses on the formation mechanism of fractures induced by excavation of a gallery in soft sedimentary rocks in the Horonobe area of Japan.Detailed fracture mapping of the gallery indicates that the fractures consist of both pre-existing shear fractures and excavation damaged zone(EDZ) fractures. EDZ fractures correspond to weak planes associated with bedding planes or transgranular cracks.The EDZ fractures terminate against pre-existing shear fractures.Therefore,even for excavations in soft sedimentary rocks,formation of the EDZ fractures are controlled by pre-existing fractures and earlier weak planes. 相似文献
20.
You-Liang Chen Rafig Azzam Tomas M. Fernandez-Steeger Lei Li 《Geotechnical and Geological Engineering》2009,27(1):155-167
The ground freezing construction technique is one of the most effective and widely applied site construction methods in soft
soil areas, like Shanghai. Some elevation-inclined refrigeration pipes are arranged for the artificial freezing excavation
of the Pudong-side first-storey connection aisle, which is designed to connect two adjacent tunnel lanes of Shanghai East-Fuxing-Road
tunnel project. No advanced research results could be found for computing the temperature field of tunnels and aisles frozen
with inclined refrigeration pipes. Anyhow the computation of the relevant temperature field is of high importance for the
safe and economical excavation of the above-mentioned aisle. In this paper, a method for computing the aisle temperature field
using 3D FEM is given, and the computation accuracy is verified by contrasting the computed and site measured results. The
back propagation neural networks are also applied to the temperature prediction using self-developed Neural Network-Expert
System software, the predicted results are also very satisfactory. The mechanism during freezing and aisle excavation will
be discussed on the basis of 3D FEM simulation. The authors believe that studying the parameter-sensitivity of temperature
field is very important for the optimum selection of parameter values. So, in this paper, the parameter-sensitivity of temperature
field is also discussed. In order to obtain the optimum frozen wall thickness, the relation between the frozen wall thickness
and the initial freezing brine temperature is studied. At the end, an excavation pre-control plan is proposed by means of
fuzzy logic theory for improving the excavation safety. The research result of the current paper is very helpful for projects
that will be excavated by freezing construction technique. 相似文献