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Soil-atmosphere interaction in earth structures

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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Micro-macro models for viscoelastic fluids： modelling, mathematics and numerics Dedicated to the NSFC-CNRS Chinese-French summer institute on fluid mechanics in 2010

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Science China Mathematics 2012年第2期55卷 353-384页

作者： LE BRIS Claude LELIVRE Tony CERMICS Ecole des Ponts ParisTech INRIA Rocquencourt MICMAC team

This paper is an introduction to the modelling of viscoelastic fluids, with an emphasis on micromacro （or multiscale） models. Some elements of mathematical and numerical analysis are provided. These notes closely follow the lectures delivered by the second author at the Chinese Academy of Science during the Workshop ＂Stress Tensor Effects on Fluid Mechanics＂ in January 2010.

关键词： viscoelastic fluids micro-macro models entropy methods Monte Carlo methods

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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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Nonlinear Conformal Electromagnetism

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Journal of Modern Physics 2022年第4期13卷 442-494页

作者： J.-F. Pommaret CERMICS Ecole des Ponts ParisTech France

In 1909 the brothers E. and F. Cosserat discovered a new nonlinear group theoretical approach to elasticity (EL), with the only experimental need to measure the EL constants. In a modern language, their idea has been to use the nonlinear Spencer sequence instead of the nonlinear Janet sequence for the Lie groupoid defining the group of rigid motions of space. Following H. Weyl, our purpose is to compute for the first time the nonlinear Spencer sequence for the Lie groupoid defining the conformal group of space-time in order to provide the mathematical foundations of electromagnetism (EM), with the only experimental need to measure the EM constant in vacuum. With a manifold of dimension n, the difficulty is to deal with the n nonlinear transformations that have been called “elations” by E. Cartan in 1922. Using the fact that dimension n=4 has very specific properties for the computation of the Spencer cohomology, we prove that there is thus no conceptual difference between the Cosserat EL field or induction equations and the Maxwell EM field or induction equations. As a byproduct, the well known field/matter couplings (piezzoelectricity, photoelasticity, streaming birefringence, …) can be described abstractly, with the only experimental need to measure the corresponding coupling constants. The main consequence of this paper is the need to revisit the mathematical foundations of gauge theory (GT) because we have proved that EM was depending on the conformal group and not on U(1), with a shift by one step to the left in the physical interpretation of the differential sequence involved.

关键词： Nonlinear Differential Sequences Linear Differential Sequences Lie Groupoids Lie Algebroids Conformal Group Spencer Cohomology Maxwell Equations Cosserat Equations

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Minimum Resolution of the Minkowski, Schwarzschild and Kerr Differential Modules

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Journal of Modern Physics 2022年第4期13卷 620-670页

作者： J.-F. Pommaret CERMICS Ecole des Ponts ParisTech France

Our recent arXiv preprints and published papers on the solution of the Riemann-Lanczos and Weyl-Lanczos problems have brought our attention on the importance of revisiting the algebraic structure of the Bianchi identities in Riemannian geometry. We also discovered in the meantime that, in our first GB book of 1978, we had already used a new way for studying the compatibility conditions (CC) of an operator that may not be necessarily formally integrable (FI) in order to construct canonical formally exact differential sequences on the jet level. The purpose of this paper is to prove that the combination of these two facts clearly shows the specific importance of the Spencer operator and the Spencer δ-cohomology, totally absent from mathematical physics today. The results obtained are unavoidable because they only depend on elementary combinatorics and diagram chasing. They also provide for the first time the purely intrinsic interpretation of the respective numbers of successive first, second, third and higher order generating CC. However, if they of course agree with the linearized Killing operator over the Minkowski metric, they largely disagree with recent publications on the respective numbers of generating CC for the linearized Killing operator over the Schwarzschild and Kerr metrics. Many similar examples are illustrating these new techniques, providing in particular a few resolutions in which the orders of the successive operators may go “up and down” surprisingly, like in the conformal situation for various dimensions.

关键词： Formal Integrability Involutivity Compatibility Conditions Spencer Operator Janet Sequence Spencer Sequence Differential Module Homological Algebra Extension Module

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Homological Solution of the Lanczos Problems in Arbitrary Dimension

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Journal of Modern Physics 2021年第6期12卷 829-858页

作者： Jean-Francois Pommaret CERMICS Ecole des Ponts ParisTech France

When D is a linear partial differential operator of any order, a direct problem is to look for an operator D1 generating the compatibility conditions (CC) D1η = 0 of Dξ = η. Conversely, when D1 is given, an inverse problem is to look for an operator D such that its CC are generated by D1 and we shall say that D1 is parametrized by D = D0. We may thus construct a differential sequence with successive operators D, D1, D2, ..., each operator parametrizing the next one. Introducing the formal adjoint ad() of an operator, we have but ad (Di-1) may not generate all the CC of ad (Di). When D = K [d1, ..., dn] = K [d] is the (non-c

关键词： Differential Sequence Variational Calculus Lanczos Potential Lanczos Operator Vessiot Structure Equations

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Effect of water chemistry on the hydro-mechanical behaviour of compacted mixtures of claystone and Na/Ca-bentonites for deep geological repositories

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第2期14卷 527-536页

作者： Zhixiong Zeng Yu-Jun Cui Jean Talandier Laboratoire Navier/CERMES Ecole des Ponts ParisTechMarne La Vallée77455France French National Radioactive Waste Management Agency(Andra) Châtenay-Malabry92298France

In the French deep geological disposal for radioactive wastes,compacted bentonite/claystone mixtures have been considered as possible sealing *** emplacement in place,such mixtures are hydrated by the site solution as well as the cement solution produced by the degradation of *** this study,the effects of synthetic site solution and cement solution on the hydro-mechanical behaviour of compacted mixtures of claystone and two types of bentonites(MX80 Na-bentonite and Sardinia Cabentonite)were investigated by carrying out a series of swelling pressure,hydraulic conductivity and mercury intrusion porosimetry(MIP)*** was found that for the MX80 bentonite/claystone mixture hydrated with synthetic site solution,the swelling capacity was reduced compared to the case with deionised water owing to the transformation of Na-montmorillonite to multi-cation dominant montmorillonite by cation *** the Sardinia bentonite/claystone mixture,the similar increasing rate of swelling pressure was observed during the crystalline swelling process for different solutions,suggesting insignificant cation ***,the cations in the synthetic site solution could reduce the thickness of diffuse double layer and the osmotic swelling for both MX80 bentonite/claystone and Sardinia bentonite/claystone *** large-pore volume increased consequently and enhanced water *** the cement solution,the hydroxide could also dissolve the montmorillonite,reducing the swelling pressure,and increase the large-pore volume,facilitating the water ***,the decrease of swelling pressure and the increase of hydraulic conductivity were more significant in the case of low dry density because of more intensive interaction between montmorillonite and hydroxide due to the high permeability.

关键词： Bentonite/claystone mixture Synthetic site solution Cement solution Bentonite type Swelling pressure Hydraulic conductivity

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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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