http://hdl.handle.net/2117/3577 2013-05-20T12:37:32Z http://hdl.handle.net/2117/13298 Title: Evaluation of self-combustion risk in tire derived aggregate fills Authors: Arroyo Alvarez de Toledo, Marcos; San Martin, Ignacio; Olivella Pastallé, Sebastià; Saaltink, Maarten Willem Abstract: Lightweight tire derived aggregate (TDA) fills are a proven recycling outlet for waste tires, requiring relatively low cost waste processing and being competitively priced against other lightweight fill alternatives. However its value has been marred as several TDA fills have self-combusted during the early applications of this technique. An empirical review of these cases led to prescriptive guidelines from the ASTM aimed at avoiding this problem. This approach has been successful in avoiding further incidents of self-combustion. However, at present there remains no rational method available to quantify selfcombustion risk in TDA fills. This means that it is not clear which aspects of the ASTM guidelines are essential and which are accessory. This hinders the practical use of TDA fills despite their inherent advantages as lightweight fill. Here a quantitative approach to self-combustion risk evaluation is developed and illustrated with a parametric analysis of an embankment case. This is later particularized to model a reported field self-combustion case. The approach is based on the available experimental observations and incorporates well-tested methodological (ISO corrosion evaluation) and theoretical tools (finite element analysis of coupled heat and mass flow). The results obtained offer clear insights into the critical aspects of the problem, allowing already some meaningful recommendations for guideline revision. 2011-09-22T11:22:54Z http://hdl.handle.net/2117/13278 Title: An insight into the water retention properties of compacted clayey soils Authors: Romero Morales, Enrique Edgar; Della Vecchia, G.; Jommi, Cristina Abstract: Experimental data from different testing methodologies on different compacted clayey soils, with dominant bimodal pore size distribution, are presented and analysed, to provide a comprehensive picture of the evolution of the aggregated fabric along hydraulic and mechanical paths. Fabric changes are analysed both from the porous network viewpoint, by means of careful mercury intrusion porosimetry investigation, and from the soil skeleton viewpoint, by quantifying swelling and shrinkage of the aggregates in an environmental scanning electron microscopy study. The consequences of the aggregated fabric evolution on the water retention properties of compacted soils are analysed and discussed. A new model for water retention domain is proposed, which introduces a dependence of the intra-aggregate pore volume on water content. The model succeeds in tracking correctly the evolution of the hydraulic state of the different soils investigated along generalised hydromechanical paths. The proposed approach brings to light coupling between intra-aggregate and inter-aggregate pores in the retention properties of compacted clayey soils. Dependence of the air entry and the air occlusion values on swelling and shrinking of aggregates, besides void ratio, is introduced and discussed. 2011-09-21T10:00:40Z http://hdl.handle.net/2117/13273 Title: Benchmark of experimental techniques for measuring and controlling suction Authors: Muñoz, Juan Jorge; Tarantino, A; Gallipoli, Domenico; Augarde, C. E.; Gennaro, V. de; Gómez, R.; Laloui, L.; Mancuso, C.; El Mountassir, G.; Wheeler, S. J.; Tombolato, S.; Toll, D. G.; Rojas Arias, Juan Carlos; Raveendiraraj, A.; Romero Morales, Enrique Edgar; Pisoni, G.; Peron, H.; Pereira, J.-M. Abstract: The paper presents a benchmarking study carried out within the ‘Mechanics of Unsaturated Soils for Engineering’ (MUSE) network aimed at comparing different techniques for measurement and control of suction. Techniques tested by the eight ‘Mechanics of Unsaturated Soils for Engineering’ research teams include axis-translation (pressure plate and suction-controlled oedometer), highcapacity tensiometer and osmotic technique. The soil used in the exercise was a mixture of uniform sand, sodium bentonite (active clay) and kaolinite (non-active clay), which were all commercially available. Samples were prepared by one team and distributed to all other teams. They were normally consolidated from slurry under one-dimensional conditions (consolidometer) to a given vertical stress. The water retention characteristics of the initially saturated specimens were investigated along the main drying path. Specimens were de-saturated by applying suction through the liquid phase when using an axis-translation technique or osmotic method and de-saturated by air-drying, when suction was measured using igh-capacity tensiometers. In general, the same technique was tested by at least two teams. The water retention curves obtained using the different techniques are compared and discrepancies are discussed in the paper. 2011-09-20T12:42:58Z http://hdl.handle.net/2117/12628 Title: Cone penetration tests in a virtual calibration chamber Authors: Arroyo Alvarez de Toledo, Marcos; Butlanska, Joanna; Gens Solé, Antonio; Calvetti, Francesco; Jamiolkowski, Michael Abstract: A virtual calibration chamber was built using a threedimensional model based on the discrete-element method. The chamber was then filled with a scaled granular equivalent of Ticino sand, the material properties of which were selected by curve-fitting triaxial tests. Cone penetration tests were then performed under different initial densities and isotropic stresses. Penetration resistance in the virtual calibration chamber was affected by the same cone/chamber size effect that affects physical calibration chambers and was corrected accordingly. The corrected cone resistance obtained from the virtual calibration chamber cone penetration tests shows good quantitative agreement with correlations that summarise previous physical results. 2011-05-20T12:41:23Z http://hdl.handle.net/2117/11733 Title: Modeling evaporation processes in a saline soil from saturation to oven dry conditions Authors: Gran Esforzado, Meritxell; Carrera Ramírez, Jesús; Olivella Pastallé, Sebastià; Saaltink, Maarten Willem Abstract: Thermal, suction and osmotic gradients interact during evaporation from a salty soil. Vapor fluxes become the main water flow mechanism under very dry conditions. A coupled nonisothermal multiphase flow and a reactive transport model of a salty sand soil was developed to study such an intricate system. The model was calibrated with data from an evaporation experiment (volumetric water content, temperature and concentration). The retention curve and relative permeability functions were modified to simulate oven dry conditions. Experimental observations were satisfactorily reproduced, which suggests that the model can be used to assess the underlying processes. Results show that evaporation is controlled by heat, and limited by salinity and liquid and vapor fluxes. Below evaporation front vapor flows downwards controlled by temperature gradient and thus generates a dilution. Vapor diffusion and dilution are strongly influenced by heat boundary conditions. Gas diffusion plays a major role in the magnitude of vapor fluxes. 2011-03-08T18:41:08Z http://hdl.handle.net/2117/11178 Title: Effect of thermo-coupled processes on the behaviour of a clay barrier submitted to heating and hydration Authors: Sánchez, M.; Gens Solé, Antonio; Olivella Pastallé, Sebastià Abstract: The storage of high level radioactive waste is still an unresolved problem of the nuclear industry, being geological disposal the most favoured option and, naturally, the one requiring the strongest geo-mechanical input. Most conceptual designs for the deep geological disposal of nuclear waste envisage placing the canisters containing the waste in horizontal drifts or vertical boreholes. The empty space surrounding the canisters is filled by an engineered barrier often made up of compacted swelling clay. In the barrier and the near field, significant thermo-hydro-mechanical (THM) phenomena take place that interact in a complex way. A good understanding of THM issues is, therefore, necessary to ensure a correct performance of engineered barriers and seals. The conditions of the bentonite in an engineered barrier for high-level radioactive waste disposal are being simulated in a mock-up heating test at almost scale, at the premises of CIEMAT in Madrid. The evolution of the main Thermo-Hydro-Mechanical (THM) variables of this test are analysed in this paper by using a fully coupled THM formulation and the corresponding finite element code. Special emphasis has been placed on the study of the effect of thermo-osmotic flow in the hydration of the clay barrier at an advanced staged of the experiment. 2011-01-24T15:10:53Z http://hdl.handle.net/2117/10974 Title: A rockfill triaxial cell with suction control Authors: Chavez, C.; Romero Morales, Enrique Edgar; Alonso Pérez de Agreda, Eduardo Abstract: This paper describes the development of a new triaxial cell specifically built to test coarse granular material under partially saturated conditions. The partial saturation is achieved by imposing a total suction that is correlated with the relative humidity. Relative humidity control was achieved by water vapor transfer using a forced convection system, which is driven by an air pump transporting the air humidity to the sample, and it is controlled by saturated saline solutions placed in a vessel.A double-wall cell was designed to monitor global volume changes of the material on compression and shearing. In addition, the cell uses a novel technique to measure local axial and radial deformations. The use of both global and local measurements allows detecting experimental problems such as membrane penetration on isotropic compression and shearing, as well as membrane sliding on shearing at low confining stresses. Selected test results are presented to show the capability of the cell during isotropic compression and shearing made with strain and stress control. The results of the test with strain control show a nonlinear increase in strength and dilatancy of the material in relation to the decrease of the relative humidity. Also they have a tendency to reach the critical state, and it can be seen that such a critical state line is a function of the relative humidity. Under a constant deviator stress, a collapse test of the rockfill was carried out and the results showed that the deformation depends strongly on the time. Furthermore, it is larger than that produced by making a test under saturated conditions, commonly taken as final reference. 2011-01-12T09:51:42Z http://hdl.handle.net/2117/10336 Title: Physical and geotechnical properties of clay phyllites Authors: Garzón, E.; Sánchez-Soto, P.J.; Romero Morales, Enrique Edgar Abstract: An experimental programme is presented with the aim of characterising –from physical, microstructural and geotechnical perspectives– the main properties of compacted clay phyllites. These clay phyllites are widely used as waterproofing material for roofs in the Alpujarras (Andalusia, Spain), as sealing liners in irrigation ponds, and as core material of small earthen zoned dams. An exhaustive physical-characterisation programme on the powder fraction has been followed using X-ray fluorescence (XRF), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), chemical analysis by energy dispersive X-ray spectroscopy (EDX), thermal analysis, particle-size distribution analysis, consistency limits, and density of solid particles. From a microstructural standpoint, mercury intrusion porosimetry (MIP) tests, as well as nitrogen-adsorption tests, were carried out to characterise the pore network and surface area of the material in both natural and compacted states. The geotechnical characterisation programme on the compacted material was focused on the water-permeability and water-retention properties, the volume change on soaking (swelling or collapse), the compressibility on loading, the shearstrength properties, and the mechanical-penetration properties. In this way, an important physical and hydro-mechanical data base is provided, which could help in evaluating the suitability for using this material in a wide range of earthen constructions (liners, road subgrades, embankments, core material in zoned dams). It has been found that the material contains illite, chlorite and quartz as the main components, and feldspar, iron oxide and interstratified illite–smectite as minor ones. Despite the presence of active clay minerals, the compacted material did not display an important swelling on soaking at low stresses, as a consequence of its low specific surface and low water-retention ability. The material exhibited good compaction properties and, consequently, low water permeability plus a stiff response on loading. Nevertheless, despite the low porosity attained on the dry-side compaction, the material underwent some collapse on soaking at stresses greater than 100 kPa. 2010-11-17T12:32:21Z http://hdl.handle.net/2117/10131 Title: Description and analysis of the debris flows occurred during 2008 in the Eastern Pyrenees Authors: Portilla, Modesto; Chevalier, G.; Hurlimann Ziegler, Marcel Abstract: Rainfall-triggered landslides taking place in the Spanish Eastern Pyrenees have usually been analysed on a regional scale. Most research focussed either on terrain susceptibility or on the characteristics of the critical rainfall, neglecting a detailed analysis of individual events. In contrast to other mountainous regions, research on debris flow has only been performed marginally and associated hazard has mostly been neglected. In this study, five debris flows, which occurred in 2008, are selected; and site specific descriptions and analysis regarding geology, morphology, rainfall data and runout were performed. The results are compared with worldwide data and some conclusions on hazard assessment are presented. The five events can be divided into two in-channel debris flows and three landslide-triggered debris flows. The inchannel generated debris flows exceeded 10 000m3, which are unusually large mass movements compared to historic events which occurred in the Eastern Pyrenees. In contrast, the other events mobilised total volumes less than 2000m3. The geomorphologic analysis showed that the studied events emphasize similar patterns when compared to published data focussing on slope angle in the initiation zone or catchment area. Rainfall data revealed that all debris flows were triggered by high intensity-short duration rainstorms during the summer season. Unfortunately, existing rainfall thresholds in the Eastern Pyrenees consider long-lasting rainfall, usually occurring in autumn/winter. Therefore, new thresholds should be established taking into account the rainfall peak intensity in mm/h, which seems to be a much more relevant factor for summer than the event’s total precipitation. The runout analysis of the 2008 debris flows confirms the trend that larger volumes generally induce higher mobility. The numerical simulation of the Riu Runer event shows that its dynamic behaviour is well represented by Voellmy fluid rheology. A maximum front velocity of 7 m/s was backanalysed for the transit section and even on the fan velocities larger than 2 m/s were obtained. This preliminary analysis of the major Eastern Pyrenean debris flows represents the first background for future studies. Additional research on other events is necessary to support the results presented herein, and to properly assess and reduce hazard related to debris flows. 2010-11-04T19:21:31Z http://hdl.handle.net/2117/9951 Title: A review of expansive phenomena in Wagenburg North Tunnel Authors: Berdugo de Moya, Iván Rafael; Alonso Pérez de Agreda, Eduardo; Romero Morales, Enrique Edgar; Gens Solé, Antonio; Albis, María Abstract: The paper deals on tunnelling and swelling in anhydritic-gypsiferous claystones. The geology of the Gipskeuper in Baden-Württemberg (Germany) and the phenomenology of expansions in Wagenburg North tunnel are described. Consistent swelling triggering events, mechanisms and exhaustion causes were identified using a thermo-hydro-chemo-mechanical theoretical analysis. It is suggested that long-term swelling in tunnels excavated through anhydritic-gypsiferous claystones is a result of solvent-way gypsum crystal growth due to ventilation induced groundwater evaporation and rock drying; an opposite concept to the usual consequences of drying in argillaceous materials, which causes shrinkage strains. 2010-10-25T07:32:55Z http://hdl.handle.net/2117/9798 Title: Influence of electroosmotic treatment on the hydro-mechanical behaviour of clayey silts: preliminary experimental results Authors: Gabrieli, L.; Jommi, Cristina; Musso, G.; Romero Morales, Enrique Edgar Abstract: Preliminary results of an investigation focused on the influence of electrokinetic treatment on the mechanical and hydraulic behaviour of clayey soils are presented. The experimental programme aims at providing a contribution to the sustainability of contaminant extraction or containment via electroosmosis. Changes in the hydraulic and mechanical properties of two illitic clayey soils, subjected to a DC electric field, were investigated. Samples of the two soils were subjected to electrokinetic filtration, for different periods of time, and under different constant loads. Afterwards, they were tested under onedimensional compression to detect changes in stiffness and hydraulic conductivity due to the electrical treatment. After the application of a DC field for a few hours, a small reversible increment in the average soil stiffness was observed, with respect to the untreated soil, while the hydraulic conductivity was not affected substantially. Dramatic changes of the mechanical and hydraulic soil properties, correlated to changes of the soil pH, were observed following non-conditioned electrokinetic treatment with duration of the order of days. 2010-10-19T10:04:16Z http://hdl.handle.net/2117/9786 Title: Microstructure et potentiel de gonflement d'une argile du Sahara algérien Authors: Lamara, M; Derriche, Z; Romero Morales, Enrique Edgar Abstract: Durant les années 80, une raffinerie de pétrole et des bâtiments résidentiels divers, construits dans la région d’In-Áménas (au sud-est de l’Algérie), ont subi des dommages sévères dus au gonflement du sol. Quelques années seulement après sa réception, la raffinerie a du être fermée et les constructions touchés sont tombées en ruine et on dû être déblayées. Des études réalisées sur le sol de la région ont montré qu’il s’agit d’une argile de type kaolinite contenant des inter stratifiés : illite vermiculite. Ces argiles présentent habituellement un potentiel de gonflement relativement faible. Dans le but de comprendre pourquoi les argiles d’In-Aménas ont développe un gonflement aussi dévastateur, les résultats d’une campagne d’essais de gonflement on été analysées. Des investigations expérimentales complémentaires portant sur la microstructure et les propriétés de rétention d’eau du sol on été effectuées. A la lumière de ces derniers résultats, l’importance de la microstructure du sol sur le comportement au gonflement est mise en évidence. 2010-10-18T21:16:27Z http://hdl.handle.net/2117/9682 Title: Assessment of the use of the vapour equilibrium technique in controlled-suction tests Authors: Pintado Llurba, Xavier; Lloret Morancho, Antonio; Romero Morales, Enrique Edgar Abstract: This paper presents a study on suction control methodology using the vapour equilibrium technique. To reduce the time needed to reach equilibrium, humid air is forced to flow through the sample boundaries. An analysis of the physical process that occurs in the tested soil samples using a numerical approach is included. The test is numerically simulated and the key parameters of the process calibrated. A sensivity analysis of the unmeasured and variables is performed. It could be observed that forcing humid air to flow through the sample reduces the equalization time, but the results from the numerical simulations highlight that this flow must be carefully applied to avoid reaching, under steady-state conditions, a different suction than that whished for. When the circulation of air along the boundaries is slow, an increase in air velocity tends to increase the rate of suction changes in the sample. However, if the circulation of air increases over some limit, the flow conditions inside the soil control the development of process. 2010-10-14T08:16:38Z http://hdl.handle.net/2117/9625 Title: Applications of multiphysical geomechanics in underground nuclear waste storage Authors: Gens Solé, Antonio; Garitte, Benoit; Olivella Pastallé, Sebastià; Vaunat, Jean Abstract: Deep geological disposal in suitable host rocks is the favoured strategy for the storage and disposal of heat-emitting high level nuclear waste. A rational design of repositories requires a good understanding of the interacting thermo-hydro-mechanical phenomena that occur in the engineered barrier and adjacent rock. To this end, a multiphysical formulation is described that allows the performance of coupled THM analyses capable of reproducing observed phenomena. The formulation and computer code is applied to the simulation of two large scale tests: a mine-by test involving the excavation of a shaft in an argillaceous rock and a large-scale high- temperature heating test in fractured rock. 2010-10-11T13:57:08Z http://hdl.handle.net/2117/9595 Title: Tunnelling and swelling in triassic sulphate-bearing rocks: part II: case studies from Jura Mountains Authors: Berdugo de Moya, Iván Rafael; Alonso Pérez de Agreda, Eduardo; Romero Morales, Enrique Edgar; Gens Solé, Antonio Abstract: Part II of this series of paper deals with the phenomenology of swelling in tunnels from Jura Mountains (Switzerland) excavated through the Gipskeuper and the Anhydritgruppe. The main features of expansions observed in the presented case studies are summarized and the performance of resisting and yielding support systems is compared. Evidences presented in this series of papers indicate that the transformation of anhydrite into gypsum is not a reasonable explanation for long-term expansive phenomena occurring in sulphate-bearing rocks. It is suggested that these phenomena are strongly related to rock degradation due to both tunneling induced drainage towards the bottom of excavations and tunneling induced ventilation. 2010-10-08T17:19:07Z