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Modelling the viscoplastic behaviour of Callovo-Oxfordian claystone with consideration of damage effect

Journal of Rock Mechanics and Geotechnical Engineering 2024年第1期16卷 303-316页

作者： Hao Wang Yu-Jun Cui Minh Ngoc Vu Jean Talandier Ecole des Ponts ParisTech Laboratoire Navier/CERMES6 et 8 avenue Blaise PascalMarne La Vallée cedex 277455France Andra R&D DepartmentChâtenay-Malabry92290France

In order to evaluate the performance of deep geological disposal of radioactive waste,an underground research laboratory(URL)was constructed by Andra in the Callovo-Oxfordian(COx)claystone formation at the Meuse/Haute-Marne(MHM).The construction of URL induced the excavation damage of host formations,and the ventilation in the galleries desaturated the host formation close to the gallery ***,it is expected that the mechanical behaviour of COx claystone is *** study presents a constitutive model developed to describe the viscoplastic behaviour of unsaturated and damaged COx *** this model,the unsaturation effect is considered by adopting the Bishop effective stress and the van Genuchten(VG)water retention *** terms of the viscoplastic behaviour,the nonstationary flow surface(NSFS)theory for unsaturated soils is used with consideration of the coupled effects of strain rate and suction on the yield stress.A progressive hardening law is ***,a non-associated flow rule is used,which is similar to that in Barcelona basic model(BBM).In addition,to describe the damage effect induced by suction change and viscoplastic loading,a damage function is defined based on the crack volume *** damage function contains two variables:unsaturated effective stress and viscoplastic volumetric strain,with the related parameters determined based on the mercury intrusion porosimetry(MIP)*** the model validation,different tests on COx claystone under different loading paths are *** between experimental and simulated results indicated that the present model is able to well describe the viscoplastic behaviour of damaged COx claystone,including swelling/shrinkage,triaxial extension and compression,and triaxial creep.

关键词： Callovo-Oxfordian(COx)claystone Excavation damage Time-dependent behaviour Suction Viscoplastic model

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Soil-atmosphere interaction in earth structures

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第1期14卷 35-49页

作者： Yujun Cui Laboratoire navier Ecole des Ponts ParisTechFrance

The soil-atmosphere interaction was investigated through laboratory testing,field monitoring and numerical *** the laboratory,the soil water evaporation mechanisms were studied using an environmental chamber equipped with a large number of sensors for controlling both the air parameters and soil *** sand and clay were *** case of sand,a dry layer could be formed during evaporation in the near surface zone where the suction corresponded to the residual volumetric water *** evaporative surface was situated at a depth where the soil temperature was the *** case of clay,soil cracking occurred,changing the evaporative surface from one-dimensional to three-dimensional *** suctionbased evaporation model was adapted to take these phenomena into account by adopting a function of dry layer evolution in the case of sand and by adopting a surface crack ratio and a retative humidity ratio in the case of *** the field,the volumetric water content,and the suction as well as the runoff were monitored for an embankment constructed with lime/cement treated *** appeared that using precipitation data only did not allow a correct description of the variations of volumetric water content and suction inside the soils,the consideration of water evaporation being *** was possible to use a correlation between precipiration and *** hydraulic conductivity was found to be a key parameter controlling the variations of volumetric water content and *** the numerical modelling,a fully coupled thermohydraulic model was developed,allowing analyzing the changes in temperature,volumetric water content and suction of soil,with the upper boundary conditions at the interface between soil and atmosphere determined using meteorological *** between simulations and measurements showed the performance of such numerical approach.

关键词： Environmental chamber Soil water evaporation Suction-based evaporation model Embankment Field monitoring Numerical modeling

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On the thermal impact on the excavation damaged zone around deep radioactive waste disposal

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Journal of Rock Mechanics and Geotechnical Engineering 2013年第3期5卷 179-190页

作者： P.Delage Ecole des ponts ParisTech Navier/CERMES

Clays and claystones are considered in some countries （including Belgium, France and Switzerland） as a potential host rock for high activity long lived radioactive waste disposal at great depth. One of the aspects to deal with when assessing the performance of the disposal is related to the effects of the temperature elevation due to the placement of exothermic wastes on the host rock. The potential effects of the thermal impact on the excavation damaged zone （EDZ） in the near field are another important issue that was the goal of the TIMODAZ European research project. In this paper, some principles of waste disposal in clayey host rocks at great depth are first presented and a series of experimental investigations carried out on specific equipment specially developed to face the problem are presented. Both drained and undrained tests have been carried out to investigate the drained thermal volume changes of clays and claystone and the thermal pressurization occurring around the galleries. The importance of proper initial saturation （under in situ stresses） and of satisfactory drainage conditions （in spite of the significantly low perme- ability of claystones） is emphasized, leading to the development of a new hollow cylinder apparatus. It is observed that claystones cannot be considered as overconsolidated clays given that they can exhibit, as the Callovo-Oxfordian claystone does, a thermoplastic contraction. Mechanical and thermal hardenings are however observed, extending the knowledge already gained on clays to claystones. A new method of determining the thermal pressurization coefficient in the laboratory is described and the data obtained allow completing existing data in the field. Finally, the hollow cylinder apparatus makes it possible to demonstrate that the good self-sealing properties of clays and claystones can be extended to temperature effects, an important conclusion in terms of performance assessment.

关键词： Radioactive waste Thermal impact Hollow cylinder triaxial Thermal behaviour Thermal pressurization Clay Claystone

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On the chemo-thermo-hydro-mechanical behaviour of geological and engineered barriers

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Journal of Rock Mechanics and Geotechnical Engineering 2013年第3期5卷 169-178页

作者： Yu-Jun Cui Anh Minh Tang Laboratoire navier/CERMES Ecole des Ponts ParisTech

An overview of the recent findings about the chemo-hydro-mechanical behaviour of materials used for both geological and engineered barriers in nuclear waste disposal is presented, through some examples about the natural Boom Clay （BC） and compacted bentonite-based materials. For the natural BC, it was found that compression index identified from both oedometer and isotropic compression tests is sim- ilar and the compressibility of BC from the Mol site is higher than that of BC from the Essen site： the shear strength of Mol BC is also higher than that of the Essen BC, suggesting a significant effect of carbo- nates content; the thermal volume change is strongly overconsolidation ratio （OCR） dependent-low OCR values promote thermal contraction while high OCR values favour thermal dilation; the volume change behaviour is also strongly time dependent and this time dependent behaviour is governed by the stress level and temperature; the effect of pore-water salinity on the volume change behaviour can be signif- icant when the smectite content is relatively high. For the bentonite-based materials, it was found that thermal contraction also occurs at low OCR values, but this is suction dependent--suction promotes ther- mal dilation. Under constant volume conditions, wetting results in a decrease of hydraulic conductivity, followed by an increase. This is found to be related to changes in macro-pores size-wetting induces a decrease of macro-pores size, followed by an increase due to the aggregates fissuring. The presence of technological voids can increase the hydraulic conductivity but does not influence the swelling pressure.

关键词： Boom Clay (BC) Bentonite-based materials Mechanical behaviour Hydraulic conductivity Pore-water salinity Technological voids

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Improved Methods for In-situ Measurement Railway Noise Barrier Insertion Loss

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第1期35卷 58-68页

作者： Li Qiutong Duhamel Denis Luo Yanyun Yin Honoré Université Paris-Est Laboratoire NavierENPC-IFSTTAR-CNRS Institute of Railway Transit Tongji University

Many countries which seek to understand the acoustic performance of railway noise barriers have established standards for the conduct of in-situ ***,there are no universally acknowledged receiver positions for the evaluation of the barrier performance,a fact which may be leading to uncertainty over the noise reduction capabilities of available *** terms of the descriptor of the barrier performance,the general recommendation is the A-weighted sound pressure level,although the latter is considered to underestimate low frequencies for railway noise ***,in this study,the comparison of receiver positions and the descriptors among existing Chinese,ISO and European standards were *** upon a combination of diffraction theory and standards,a rearrangement of receiver positions and one-third-octave-band analysis were *** addition,in line with improved methods,an in-situ measurement of insertion loss for a 1.5 mhigh railway noise barrier was designed and *** results of the experiment validate as effective and applicable the new receiver *** results also suggest that one-third-octave-band analysis is indispensable.

关键词： railway noise noise barrier in-situ experiment A-weighting insertion loss one-third-octave-band analysis grid receiver positions

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聚合物和新拌混凝土性能研究进展（英文）

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硅酸盐学报 2015年第10期43卷 1401-1407页

作者： Nicolas ROUSSEL IFSTTAR East Paris UniversityNavier Laboratory

通过对颗粒/颗粒和颗粒/液相之间相互作用进行理论和微观力学研究,首先提出了稳定状态下水泥净浆在简单剪切力作用下,以剪切速率和固体体积分数为参数的主要影响因素理论方程。在此框架下,对水泥混凝土工业中常用聚合物掺入后,胶凝材料... 详细信息

通过对颗粒/颗粒和颗粒/液相之间相互作用进行理论和微观力学研究,首先提出了稳定状态下水泥净浆在简单剪切力作用下,以剪切速率和固体体积分数为参数的主要影响因素理论方程。在此框架下,对水泥混凝土工业中常用聚合物掺入后,胶凝材料浆体基本物理性能研究的最新进展进行了阐述。最后,讨论了水泥净浆流变性能和新拌混凝土性能之间的转换关系。

关键词：流变学屈服强度黏度聚合物新拌混凝土

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微观结构对用于工程屏障的高压实膨胀黏土性状的一些作用(英文)

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岩石力学与工程学报 2006年第4期25卷 721-732页

作者： Delage Pierre CERMES-I. navier法国国立路桥大学

近 10 a 来,用于高放废物工程屏障的高压实膨胀黏土的性状受到了广泛关注。据此通过吸力控制试验获取了一些高压实膨润土的试验数据,并从微观结构特性角度进行了解释。水分滞留和迁移特性,以及吸力变化下的膨胀反应都与微观机理相关,同... 详细信息

近 10 a 来,用于高放废物工程屏障的高压实膨胀黏土的性状受到了广泛关注。据此通过吸力控制试验获取了一些高压实膨润土的试验数据,并从微观结构特性角度进行了解释。水分滞留和迁移特性,以及吸力变化下的膨胀反应都与微观机理相关,同时对吸附阳离子的作用也进行了评价。

关键词：工程屏障膨胀性黏士微观结构核废物吸力

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Microstructure and anisotropic swelling behaviour of compacted bentonite/sand mixture

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Journal of Rock Mechanics and Geotechnical Engineering 2014年第2期6卷 126-132页

作者： Simona Saba Jean-Dominique Barnichon Yu-Jun Cui Anh Minh Tang Pierre Delage Ecole des Ponts ParisTech Laboratoire Navier Institut de Radioprotection et de Surete Nucleaire(IRSN)

Pre-compacted elements （disks, tutus） of bentonite/sand mixture are candidate materials for sealing plugs of radioactive waste disposal. Choice of this material is mainly based on its swelling capacity allowing all gaps in the system to be sealed, and on its low permeability. When emplaced in the gallery, these elements will start to absorb water from the host rock and swell. Thereby, a swelling pressure will develop in the radial direction against the host rock and in the axial direction against the support structure. In this work, the swelling pressure of a small scale compacted disk of bentonite and sand was experimentally studied in both radial and axial directions. Different swelling kinetics were identified for different dry densities and along different directions. As a rule, the swelling pressure starts increasing quickly, reaches a peak value, decreases a little and finally stabilises. For some dry densities, higher peaks were observed in the radial direction than in the axial direction. The presence of peaks is related to the microstructure change and to the collapse of macro- pores. In parallel to the mechanical tests, microstructure investigation at the sample scale was conducted using microfocus X-ray computed tomography （BCT）. Image observation showed a denser structure in the centre and a looser one in the border, which was also confirmed by image analysis. This structure heterogeneity in the radial direction and the occurrence of macro-pores close to the radial boundary of the sample can explain the large peaks observed in the radial swelling pressure evolution. Another interesting result is the higher anisotropy found at lower bentonite dry densities, which was also analysed by means ofμCT observation of a sample at low bentonite dry density after the end of test. It was found that the macro-pores, especially those between sand grains, were not filled by swelled bentonite, which preserved the anisotropic microstructure caused by uniaxial compression

关键词： Bentonite/sand mixture Nuclear waste disposal Anisotropy Swelling pressure Microstructure Microfocus X-ray computed tomography(μCT)

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Elastic behavior of saturated porous materials under undrained freezing

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Acta Mechanica Sinica 2013年第6期29卷 827-835页

作者： Qiang Zeng Teddy Fen-Chong Ke-Fei Li Civil Engineering Department Tsinghua University Universit Paris-Est Laboratoire Navier(UMR 8205)CNRSENPCIFSTTAR2 alle KeplerF-77420 Champs-sur-MarneFrance

The elastic behavior of saturated porous materi- als under undrained freezing is investigated by using a poro- mechanical approach. Thermodynamic equilibria are used to describe the crystallization process of the partially frozen solution in bulk state and confined state in pores. By phase transition at freezing, fusion energy, thermal contraction of solid, solution and ice crystals, volume changes of crystallization build up remarkable pore pressure that induces expansion or shrinkage of solid matrix. Owing to the lower chemical potential when pore water mixes with salts, fewer ice forms in pores. Penetration of ice into the porous materials increases the capillary pressure, but limits effect on the pore liquid pressure and the strain of solid matrix. On the contrary, the pore pressure induced by solution density rises as salt concentration increases and causes significant shrinkage of solid matrix.

关键词： Poromechanics Crystallization Cement Salt solution

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Investigation of the hydro-mechanical behaviour of compacted expansive clay

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Frontiers of Structural and Civil Engineering 2010年第2期4卷 154-164页

作者： Yujun CUI An Ninh TA Anh Minh TANG Yingfa LU Ecole des Ponts ParisTech UR Navier-CERMESParis 77455France The China Three Gorges University Yichang 443002China

The hydro-mechanical behaviour of compacted expansive Romainville clay was *** soil was air-dried,crushed,and passed through a 2 mm sieve before being statically compacted to a dry density of 1.35 Mg/*** mechanical behaviour was investigated by tests in oedometer with controlled suction using the vapor equilibrium technique(suction s=0,9,39,and 110 MPa).The vertical stress was applied in the range of 0-800 *** experimental results are shown as follows:1)wetting-induced swelling was higher at lower vertical stresses;2)the vertical stress under which no swelling occurred during water flooding was estimated at 60 kPa,which can be considered as the swelling pressure of the soil tested;3)the soil compressibility(changes of volume upon stress increases)was strongly influenced by the soil suction:the lower the suction,the higher the *** hydraulic behaviour was investigated using a large-scale infiltration chamber(800mm×1000 mm in section and 1000mm high).The large size of the soil column allowed bttrying the volumetric water content sensors(ThetaProbe)without significantly affecting the water transfer and the soil swelling during *** soil suction was monitored along the soil height(every 100 mm)using various relative humidity sensors and *** the infiltration test,water was kept on the soil surface and changes in suction and volumetric water content were monitored for 338 *** wetting front has reached the bottom of the soil column at the end of the *** data from the simultaneous monitoring of suction and water content were used to determine the water retention curve and the unsaturated hydraulic conductivity using the instantaneous profile *** has been observed that the soil water retention curve depends on the soil depth;that is to be related to the soil depthdependent *** unsaturated hydraulic conductiv-ity was found to be quite low,comprised between 3×10-11m/s(at saturated state)and 10-14

关键词： Romainville clay suction control oedometer test large infiltration task hydro-mechanical behaviour

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