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Effects of temperature and thermally-induced microstructure change on hydraulic conductivity of boom clay

Journal of Rock Mechanics and Geotechnical Engineering 2017年第3期9卷 1-13页

作者： W.Z. Chen Y.S. Ma H.D. Yu F.F. Li X.L. Li X. Sillen Research Centre of Geotechnical and Structural Engineering Shandong University Jinan Shandong 250061 China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 China University of Chinese Academy of Sciences Beijing 100049 China European Underground Research Infrastructure for Disposal of Nuclear Waste in clay Environment EIG Euridice Mol 2400 Belgium ONDRAF/NIRAS Brussel 1210 Belgium

boom clay is one of the potential host rocks for deep geological disposal of high-level radioactive nuclear waste in Belgium. In order to investigate the mechanism of hydraulic conductivity variation under complex thermo-mechanical coupling conditions and to better understand the thermo-hydromechanical(THM) coupling behaviour of boom clay, a series of permeability tests using temperaturecontrolled triaxial cell has been carried out on the boom clay samples taken from Belgian underground research laboratory(URL) HADES. Due to its sedimentary nature, boom clay presents acrossanisotropy with respect to its sub-horizontal bedding plane. Direct measurements of the vertical(Kv)and horizontal(Kh)hydraulic conductivities show that the hydraulic conductivity at 80℃ is about 2.4 times larger than that at room temperature(23℃), and the hydraulic conductivity variation with temperature is basically reversible during heatingecooling cycle. The anisotropic property of boom clay is studied by scanning electron microscope(SEM) tests, which highlight the transversely isotropic characteristics of intact boom clay. It is shown that the sub-horizontal bedding feature accounts for the horizontal permeability higher than the vertical one. The measured increment in hydraulic conductivity with temperature is lower than the calculated one when merely considering the changes in water kinematic viscosity and density with temperature. The nuclear magnetic resonance(NMR) tests have also been carried out to investigate the impact of microstructure variation on the THM properties of clay. The results show that heating under unconstrained boundary condition will produce larger size of pores and weaken the microstructure. The discrepancy between the hydraulic conductivity experimentally measured and predicted(considering water viscosity and density changes with temperature) can be attributed to the microstructural weakening effect on the thermal volume change behaviour of boom clay. Based on the ex

关键词： boom clay Permeability Thermal effect Anisotropy Microstructure

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A critical state based thermo-elasto-plastic constitutive model for structured clays

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第6期9卷 1094-1103页

作者： Amir Hamidi Saeed Tourchi Fatemeh Kardooni Department of Civil Engineering School of Engineering Kharazmi University Department of Civil and Environmental Engineering Universitat Politècnica de CatalunyaBarcelona Tech

In this paper, a critical state based thermo-elasto-plastic constitutive model is developed for destructured, naturally structured and artificially structured saturated clays. The model is an extension of the previously developed thermo-mechanical model by the authors for saturated clays, considering the effects of structure on the mechanical behaviors of the soil. It is based on change in the position of normal consolidation line(NCL) in a compression plane(e-ln p′) due to the soil’s structure and variation of temperature. The present model is able to simulate the mechanical behavior of structured saturated clays in a triaxial plane at elevated temperatures lower than the boiling point of water. An attempt has been made to use the lowest possible number of parameters compared with that of Came clay model and to ensure that these new parameters have clear physical interpretations. The sufficiency of the model was verified by the test results on artificially and naturally structured soils using thermal triaxial tests.

关键词： Thermo-mechanical constitutive model Structured clays Cam clay Normal consolidation line boom clay

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Design and development of large-scale in-situ PRAclay heater test and horizontal high-level radioactive waste disposal gallery seal test in Belgian HADES

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Journal of Rock Mechanics and Geotechnical Engineering 2010年第2期2卷 103-110页

作者： X.L.Li W.Bastiaens P.Van Marcke J.Verstricht G.J.Chen E.Weetjens X.Sillen European Underground Research Infrastructure for Disposal of Nuclear Waste in clay Environment EURIDICEMol00Belgium Belgian Nuclear Research Center（SCK·CEN） Mol2400Belgium

In Belgium,the boom clay was selected as a potential host formation for the disposal of high-level radioactive waste（HLW）.To demonstrate the suitability of boom clay for bearing thermal load induced by the HLW,a large-scale in-situ heater test,called PRAclay heater test,will be conducted in the underground research laboratory（URL） in *** to the limitations of the test（a short period of time compared with that considered in a real repository,different boundary conditions,etc.）,the test is designed to simulate,in a conservative way,the most critical state and phenomena that could occur in the host *** PRAclay gallery was excavated at the end of 2007;the heating phase will begin in 2010 and will last for at least 10 *** PRAclay gallery itself leaves an opportunity to study the possibilities of sealing a disposal drift in boom clay and testing the feasibility of hydraulic cut-off of any preferential pathway to the main access gallery through the excavation damage zone（EDZ） and the lining with a seal in a horizontal drift（horizontal seal）.Indeed,this is a generic problem for all deep geological disposal facilities for *** annular seal made of compacted swelling bentonite will be installed in the front of the heated part of the PRAclay gallery for these *** paper provides detailed considerations on the thermo-hydro-mechanical（THM） boundary conditions for the design of the PRAclay heater test and the seal test with the support of numerical *** is believed that these important items considered in the PRAclay heater test design also constitute key issues for the repository *** outcome of the PRAclay heater test will be an important milestone for the Belgian repository design.

关键词： high-level radioactive waste(HLW) boom clay PRAclay heater test hydraulic cut-off thermo-hydro-mechanical(THM) boundary conditions scoping calculation

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考虑弹塑性应力渗流耦合作用的泥岩本构模型研究

考虑弹塑性应力渗流耦合作用的泥岩本构模型研究

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作者：张力伟长江大学

学位级别：硕士

泥岩是同时具有较低的渗透性、良好的蠕变特性、高吸附性以及遇水损伤自修复特性的富含粘土矿物,而boom clay继承了泥岩的上述特性的同时还有较好的膨胀性,使得boom clay地层具备非常好的化学封闭性,因此被比利时、法国、瑞士、德国等... 详细信息

泥岩是同时具有较低的渗透性、良好的蠕变特性、高吸附性以及遇水损伤自修复特性的富含粘土矿物,而boom clay继承了泥岩的上述特性的同时还有较好的膨胀性,使得boom clay地层具备非常好的化学封闭性,因此被比利时、法国、瑞士、德国等欧洲国家一致认定为处置核废料的最佳地层之一。为了能更确切的了解泥岩各地层不同的原位物理力学特性,欧洲内的数国均开展了地下实验项目,以对其进行系统的研究。本文结合比利时HADES地下实验室项目,对boom clay的弹塑性力学特性和应力-渗流耦合特性进行了研究,主要的研究内容如下:(1)对boom clay的地层分布、矿物组成颗粒粒径分布等基本物理参数进行了分析,结果表明:boom clay地层分布较为均匀;颗粒组成中,粒径小于32μm和小于62μm的居多;boom clay的矿物成分中粘土矿物占比大约在60%左右,这些粘土矿物包括伊利石、蒙脱石和高岭石;非粘土矿物主要为石英和长石组成。(2)对boom clay的室内三轴试验数据进行了分析,发现boom clay具有明显的峰前硬化和峰后软化力学特性,利用全应力-应变过程中的应变变化,建立了内变量,以此为参考,提出了能考虑应变硬化、软化的弹塑性耦合模型,并利用有限元软件ABAQUS对该模型进行了验证。验证结果发现,利用该模型所计算出的结果能够较贴切的反映boom clay在实际三轴压缩过程中的变形特征。(3)对boom clay在压缩变形过程中的渗透率演化规律进行了系统的分析,通过参考其他不同岩石在全应力-应变过程中的渗透性演化规律,并结合文中所建立的内变量将boom clay的渗透率演化过程分为三个阶段:扩容前的降低阶段、扩容后的极速增长阶段、达到残余阶段后的稳定阶段。为能充分考虑扩容点对渗透率突变的影响,引入了逾渗理论,在逾渗理论的基础上,结合围压与初始渗透率和峰值渗透率的关系,建立了能考虑围压效应的boom clay渗透率演化方程。(4)结合所建立的boom clay弹塑性耦合模型和考虑围压效应的boom clay渗透率演化方程,建立了boom clay应力-渗流耦合模型,利用USDFLD接口将模型嵌入到ABAQUS中,利用该模型对boom clay的三轴压缩试验进行了模拟,通过分析结果对该模型中的渗透率演化特征进行了验证。(5)基于boom clay各项物理力学参数、考虑应力-渗流耦合特征的boom clay模型等研究成果,结合比利时HADES地下实验室的CONNECTING GALLERY项目,建立boom clay地层中的盾构法巷道开挖有限元模型,对巷道开挖过程中的围岩应力、变形、和渗流特征变化进行模拟分析,为boom clay地层中的巷道开挖提供围岩的稳定性分析依据。

关键词： boom clay 应力-渗流耦合模型渗透率演化规律应变硬化软化围岩稳定性分析

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