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

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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Investigation of the hydro-mechanical behaviour of fouled ballast

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第4期14卷 244-255页

作者： Yu-jun CUI Trong Vinh DUONG anh minh tang Jean-Claude DUPLA Nicolas CALON Alain ROBINET Laboratoire Navier/CERMES Ecole des Ponts ParisTechBlaise PascalCité DescartesChamps-sur-Marne 77455 Marne-la-Vallée Cedex-France French National Railway Company 93574La Plaine St DenisFrance

In this study,a fouled ballast taken from the site of Sénissiat,France,was *** the hydraulic behaviour,a large-scale cell was developed allowing drainage and evaporation tests to be carried out with monitoring of both suction and volumetric water content at various positions of the *** was observed that the hydraulic conductivity of fouled ballast is decreasing with suction increase,as for common unsaturated *** effect of fines content was found to be *** the mechanical behaviour,both monotonic and cyclic triaxial tests were carried out using a large-scale triaxial *** water contents were *** results were interpreted in terms of shear strength and permanent axial *** appeared that the water content is an important factor to be accounted for since any increase of water content or degree of saturation significantly decreases the shear strength and increases the permanent *** modelling has been attempted based on the experimental *** model in its current state is capable of describing the effects of stress level,cycle number and water content.

关键词： Fouled ballast Degree of saturation Hydraulic behaviour Mechanical behaviour Fines content Constitutive modelling

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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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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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Effects of lime treatment on the microstructure and hydraulic conductivity of Héricourt clay

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Journal of Rock Mechanics and Geotechnical Engineering 2014年第5期6卷 399-404页

作者： Thanh Danh Tran Yu-Jun Cui anh minh tang Martine Audiguier Roger Cojean Mines ParisTech-Centre de Géosciences FontainebleauFrance Laboratoire Navier/CERMES Ecole des Ponts ParisTech6 et 8 Avenue Blaise Pascal77455 Marne-la-Vallée Cedex 2France Mines ParisTeche-Centre de Géosciences FontainebleauFrance

This study aims at evidencing the effects of lime treatment on the microstructure and hydraulic conductivityof a compacted expansive clay, with emphasis put on the effect of lime hydration and *** this purpose, evolutions of hydraulic conductivity were investigated for both lime-treatedand untreated soil specimens over 7 d after full saturation of the specimens and their microstructureswere observed at the end. Note that for the treated specimen, dry clay powder was mixed with quicklimeprior to compaction in order to study the effect of lime hydration. It is observed that lime hydration andmodification did not affect the intra-aggregate pores but increased the inter-aggregates pores size. Thisincrease gave rise to an increase of hydraulic conductivity. More precisely, the hydraulic conductivity oflime-treated specimen increased progressively during the first 3 d of modification phase and stabilisedduring the next 4 d which correspond to a short period prior to the stabilisation phase. The microstructureobservation showed that stabilisation reactions took place after 7 d. Under the effect of stabilisation,a decreasing hydraulic conductivity can be expected in longer time due to the formation ofcementitious compounds. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

关键词： Clays Lime hydration Hydraulic conductivity Microstructure Temperature effect

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膨胀土收缩开裂过程及其温度效应

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岩土工程学报 2012年第12期34卷 2181-2187页

作者：唐朝生崔玉军 anh-minh tang 施斌南京大学地球科学与工程学院南京210093 法国国立路桥大学法国巴黎77455

温度作为主要的外部环境因素之一,对膨胀土水-力学性质有重要影响。为了了解膨胀土在不同温度条件下的干缩开裂特性,开展了一系列干燥试验。试验中共配制了9组初始饱和的泥浆试样,干燥环境温度分别为22℃,60℃和105℃。在干燥过程中,实... 详细信息

温度作为主要的外部环境因素之一,对膨胀土水-力学性质有重要影响。为了了解膨胀土在不同温度条件下的干缩开裂特性,开展了一系列干燥试验。试验中共配制了9组初始饱和的泥浆试样,干燥环境温度分别为22℃,60℃和105℃。在干燥过程中,实时监测试样的含水率变化及表面裂隙的演化过程,利用数字图像处理技术,对裂隙图像进行了定量分析,获得了表面裂隙率Rsc;采用填充法,测量了裂隙的体积。结果表明:在干燥初期,试样中水分蒸发速率为常数,且随温度的增加而增加,试样达到残余含水率所需时间随温度的增加而减小;裂隙出现时对应的临界含水率wIC受温度的影响非常明显,当温度从22℃增加到105℃时,wIC从38.0%增加到90.9%;在裂隙发展前期,Rsc增速较缓,随后进入快速发展期,较小的含水率变化可导致Rsc迅速增加;当含水率接近终期临界含水率wFC或缩限时,裂隙发展趋于稳定,且wFC基本不受温度的影响;在高温环境下,膨胀土的裂隙发育程度较低温环境高,存在明显的温度效应。

关键词：膨胀土温度蒸发收缩裂隙图像处理

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土体干燥过程中的体积收缩变形特征

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岩土工程学报 2011年第8期33卷 1271-1279页

作者：唐朝生崔玉军 anh-minh tang 施斌南京大学地球科学与工程学院江苏南京210093 中国矿业大学深部岩土力学与地下工程国家重点实验室徐州221008 法国国立路桥大学巴黎77455

通过开展室内试验,分别研究了初始饱和的糊状试样和不同压实状态的压实试样的体积收缩变形特征。对于糊状试样,采用液体体积置换法测量了试样干燥过程中的体积变化,获得了完整的收缩曲线,试验结果表明:糊状试样的收缩过程可分正常收缩... 详细信息

通过开展室内试验,分别研究了初始饱和的糊状试样和不同压实状态的压实试样的体积收缩变形特征。对于糊状试样,采用液体体积置换法测量了试样干燥过程中的体积变化,获得了完整的收缩曲线,试验结果表明:糊状试样的收缩过程可分正常收缩、残余收缩和零收缩3个阶段;绝大部分收缩变形发生在进气点之前即土体处于饱和状态。对于压实试样,初始干密度和含水率对收缩特征有重要影响:初始干密度增加对体积收缩变形起抑制作用,而初始含水率的增加对体积收缩变形起促进作用。此外,压实试样的体积收缩存在明显的各向异性,且对初始含水率的敏感程度高于初始干密度。最后,根据试验结果,提出了压实试样收缩应变与初始干密度和含水率之间的函数关系式。

关键词：土体收缩收缩曲线压实条件影响因素土结构含水率

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Studying the stress-suction coupling in soils using an oedometer equipped with a high capacity tensiometer

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Frontiers of Structural and Civil Engineering 2011年第2期5卷 160-170页

作者： Trung Tinh LE Yu-Jun CUI Juan Jorge MUÑOZ Pierre DELAGE anh minh tang Xiang-Ling LI Ecole des ponts ParisTech Navier/CERMES6-8av.B.PascalCitéDescartesChamps-sur-Marne77455 Marne-la-Vallée cedex 2France The China Three Gorges University Yichang 443002China EURIDICE Group c/o SCK./CENBoeretang 2002400 MolBelgium

In the context of research into deep nuclear waste disposal,various works have concerned the hydromechanical behavior of Boom clay,a stiff plastic clay extracted in the SCK-CEN Underground Research Laboratory near the Mol City(Belgium),at a depth of 223 *** to some amount of smectite minerals in the clay fraction,Boom clay exhibits swelling properties when hydrated under low *** investigate some aspects of the hydromechanical behavior of Boom clay,oedometer compression tests were carried out on samples of Boom clay close to saturation and submitted to an initial *** oedometer compression,the changes in suction with increased vertical stress are monitored by means of a high capacity tensiometer installed at the bottom of the *** aspects related to hydromechanical couplings are examined through the investigation of the changes in suction during oedometer compression,a somewhat delicate and poorly documented experimental approach.A comparison is also made with a completely different soil sample under suction,i.e.a statically compacted unsaturated low plasticity *** technical difficulties typical of this new experimental approach are first described in detail so as to optimize the interpretation of the data *** experiment allows the determination of the point at which suction is changed to positive pressure during *** this point,the ratio between the vertical stress and the change in suction are *** this point,the data show that positive pore pressures are dissipated in a common *** suction/stress behavior during unloading is also described and ***,an interpretation in terms of microstructure effects is provided for both *** experimental approach initiated here seems to provide interesting further application to better understand hydromechanical couplings in natural soils in relation with suction increase during stress release.

关键词： Oedometer tensiometer swelling physicochemical and mechanical effects stress/suction coupling soil plasticity

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高放废物处置库中COx回填材料的水-力耦合性质

高放废物处置库中COx回填材料的水-力耦合性质

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第三届废物地下处置学术研讨会

作者：唐朝生崔玉军 anh-minh tang 施斌南京大学地球科学与工程学院法国国立路桥大学

目前,粉碎后的Callovo-Oxfordian(COx)泥岩在法国被提议为可选回填材料应用在高放废物处置库的工程屏障中。通过开展一维压缩试验,研究了粗、细两种COx泥岩粉末在循环加荷-卸荷条件下的压缩特征,当干密度达到2.0g/cm后,对土样通水饱和,... 详细信息

目前,粉碎后的Callovo-Oxfordian(COx)泥岩在法国被提议为可选回填材料应用在高放废物处置库的工程屏障中。通过开展一维压缩试验,研究了粗、细两种COx泥岩粉末在循环加荷-卸荷条件下的压缩特征,当干密度达到2.0g/cm后,对土样通水饱和,探讨了初始轴向应力大小和粒度成分对土样水力学性质的影响。结果表明:压缩曲线受粒度成分的影响非常明显,为了获得同等的压实度,细粒土所需的压实功能较粗粒土高,除此之外,细粒土的压缩指数也高于粗粒土;土样卸荷时回弹指数随干密度的增加而增加,受粒度成分的影响不明显;饱和过程中,当初始轴向应力较低时,粗颗粒和细颗粒土样均表现出明显的膨胀性,轴向应力逐渐增加;在初始高轴向应力作用下,粗颗粒土样体积发生塌陷,轴向应力逐渐减小,而细颗粒土样的轴向应力则呈减小-增加-再减小的趋势;饱和结束后,细颗粒土样的最终平衡轴向应力均高于粗颗粒土。

关键词：核废料处置回填材料 Callovo-Oxfodian泥岩膨胀塌陷粒度成分

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BTEX pollution caused by motorcycles in the megacity of HoChiminh

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Journal of Environmental Sciences 2013年第2期25卷 348-356页

作者： Tran Thi Ngoc Lan Pham anh minh University of Science Vietnam National University227 Nguyen Van CuHoChiMinh 70000Vietnam

Monitoring of benzene, toluene and xylenes （BTEX） was conducted along with traffic counts at 17 roadside sites in urban areas of HoChiminh. Toluene was the most abundant substance, followed by p,m-xylenes, benzene, o-xylene and ethylbenzene. The maximum observed hour-average benzene concentration was 254 μg/m3 . Motorcycles contributed to 91% of the traffic fleet. High correlations among BTEX species, between BTEX concentrations and the volume of on-road motorcycles, and between inter-species ratios in air and in gasoline indicate the motorcycle-exhaust origin of BTEX species. Daily concentrations of benzene, toluene, ethylbenzene, p,m-xylenes and o-xylene were 56, 121, 21, 64 and 23 μg/m 3 , respectively. p,m-xylenes possess the highest ozone formation potential among the BTEX family.

关键词： air pollution benzene BTEX HoChiminh motorcycle exhaust

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