Smart monitoring system for risk management in the underground space

This paper presents a smart monitoring system for risk management in the underground space. This space has a major role in cities, but it suffers from high vulnerability to hazards such as fire, flood and accidents. The paper provides analysis of the vulnerability of the underground space and shows how a smart monitoring system of human presence, indoor conditions, underground space access and equipment performances with advanced data analysis could help in improving the risk management in this space

Numerical model for unsaturated sandy soils in seismic area (application to liquefaction)

Ce travail comporte la formulation d'un modèle numérique pour les sols sableux partiellement saturés et son application à l'analyse de la liquéfaction de ces sols. La liquéfaction est un phénomène important qui peut se produire sous sollicitation sismique. Depuis le séisme de Niigata en 1964, des recherches importantes ont été menées sur ce phénomène. La plupart de ces recherches ont été consacrée aux sols saturés. Cependant, les observations montrent qu'une légère diminution de la saturation en eau engendre une augmentation significative de la résistance des sols à la liquéfaction. A noter que dans le domaine de la géotechnique, les sols sont souvent en condition partiellement saturée. Les couches des sols liquéfiables qui sont situées au-dessous de la nappe sont dans un état quasi-saturé. Il est donc nécessaire d'étudier la liquéfaction des sols sableux en condition partiellement saturée. A partir des observations expérimentales, des hypothèses sont proposées dans ce travail pour la construction d'un modèle numérique: égalité de la pression de l'air et celle de l'eau dans l'espace poreux; absence d'interaction entre ces deux phases; absence du flux d'air. Un modèle est formulé pour les sols partiellement saturés dans le cadre de la théorie de la poromécanique fondée par Coussy. Le modèle proposé est adapté aux problèmes des sols en condition saturée ou partiellement saturée. Les sols saturés sont considérés comme un cas particulier. Les analyses du module de compressibilité et du coefficient de Skempton confirment les fondements théoriques du modèle proposé. Enfin, le modèle est validé sur des observations expérimentales. Dans la dernière partie, un modèle élastoplastique cyclique est utilisé dans le cadre du modèle proposé pour étudier l'influence de la saturation sur la liquéfaction des sables. Les résultats montrent que la diminution de la saturation en eau conduit à une augmentation de la résistance des sables à la liquéfaction. L'étude de la réponse en champ libre montre que la saturation initiale influence d'une manière significative la liquéfaction de sols. Elle conduit à réduire le risque de liquéfaction de ces sols. Le tassement pendant la phase de chargement (avant la dissipation de la surpression) augmente avec la diminution de la saturation en eau. L'influence de la perméabilité des sols partiellement saturés est moins significative que celle en condition saturée.LILLE1-BU (590092102) / SudocSudocFranceF

Progress on the exploitation of urban underground space (UUS) in China

With the rapid urbanization in China, the disasters and the problems related with the urban underground space (UUS) exploitation increase. As an inevitable choice for sustainable urban development, how to increase the efficiency of the underground space use and augment the resilience of the UUS are the main challenges today in China. In this study, the strategic demands of the sustainable urban development on the underground space exploitation in Chinese cities have been analyzed and discussed. The associated problems and difficulties on the underground space exploitation were discussed. Moreover, the possible solutions were also proposed

Influence of soil saturation on the free field response of liquefiable soils

International audienceThe present paper presents analysis of the influence of the soil saturation on the free -field response of liquefiable soils. Analyses are conducted using a finite element program developed for partially saturated soils subjected to cyclic loading. The performances of the proposed model are analysed by simulation of undrained triaxial tests with different water saturations. The finite element program is then used for the analysis of the influences of the soil saturation, density and position of the water table on the liquefaction of a soil layer subjected to cyclic loading. Results show that the soil saturation significantly affects the liquefaction of partially saturated sandy layers. The decrease in the soil saturation results in a reduction of liquefaction risk

A coupled elastoplastic and visco-plastic damage model for hard clay and its application for the underground gallery excavation

The numerical modelling of the excavation of an underground gallery in hard clay has been discussed in current article. A constitutive model is proposed to describe poromechanical behaviour of the hard clay. The main features of the hard clay observed in laboratory and in-situ experimental investigation have been taken into account in the proposed constitutive model, in particular the plastic deformation, the visco-plastic deformation, the damage, etc. The influence of the initial in-situ stress and the pore pressure has been taken into consideration. The numerical modelling of the underground excavation has been implemented by using a fully coupled hydro-mechanical finite element calculation code. The performance of the model is examined by comparing numerical simulations with in situ measurements. The proposed model and the calculation procedure for the modelling of the excavation of an underground gallery have the capacity to reproduce well the excavation damaged/distributed zone and other main features and phenomena observed during the excavation process. However, the in-situ observed convergence could not be reproduced correctly. More effort on the discontinuous problem should be made for the reproduce the observed convergence. Keywords: Full coupled hydro-mechanical processes, Elasto-plastic-damage model, Visco-plastic model, Underground excavatio

GIS-Based Spatiotemporal Mapping of Groundwater Potability and Palatability Indices in Arid and Semi-Arid Areas

International audienceThis paper aims to assess groundwater potability and palatability in the West Bank, Palestine. It combines the adjusted weighted arithmetic water quality index method (AWAWQIM), a close-ended questionnaire, and step-wise assessment ratio analysis (SWARA) to develop groundwater potability (PoGWQI) and palatability (PaGWQI) indices. Both a geographic information system (GIS) and the kriging interpolation method (KIM) are employed to create spatiotemporal mapping of PoGWQI and PaGWQI. The research is based on data from 79 wells, which were provided by the Palestinian Water Authority (PWA). Data include fecal coliform (FC), nitrate (NO3), pH, chloride (Cl), sulfate (SO4), bicarbonate (HCO3), total dissolved solids (TDS), turbidity, and hardness. Results indicate that 2% and 5% of water samples were unpotable and unpalatable, respectively. Unpotable samples were found in areas with poor sewer networks and intensive use of agrochemicals. All groundwater samples (100%) in the eastern part of the West Bank were unpalatable because of seawater intrusion. Unconfined aquifers were more vulnerable to potability and palatability contamination. It was noticed that PoGWQI is sensitive to FC and NO3, while PaGWQI is sensitive to HCO3, TDS, and Cl. Consequently, these quality parameters should be monitored well. The proposed method is of great interest to water decision-makers in Palestine for establishing strategies to protect water resources

Applicability of UH model to coarse-grained soil

Large-scale triaxial, K0 compression and constant stress ratio path tests were carried out on two kinds of coarse-grained soils. Stress-strain relationships of these tests were simulated by using UH model for sands to study the applicability of the model to different stress paths of coarse-grained soil, and the results were compared with those of Duncan’s E-B model. It is shown that the mechanical behaviors of coarse-grained soil can be well described by the UH model, and overall its capacity to reflect stress-strain relationship under different stress paths is better than that of Duncan’s E-B model. Finally, the UH model and Duncan’s E-B model were used for stress-deformation analysis of a core rockfill dam. The applicability of UH model for sands to coarse-grained soil was verified

Numerical modelling of desiccation shrinkage and cracking of soils

International audienc

Smart technology applications for the optimal management of underground facilities

This study centers on the use of smart technology to improve the lifecycle management of underground facilities. It presents a comprehensive digital solution that addresses the challenges of underground facilities, particularly those related to the extensive use of underground space, as well as the requirements for safety, sustainability, and quality of services. The proposed solution emerged from discussions with experts, companies, and cities involved in the design, construction, and management of underground facilities. In this paper, we first discuss the major challenges of underground facilities, then, we present the development of a smart solution to address these challenges. This study demonstrates a promising perspective for the use of smart technology in the optimal management of underground facilities, and paves the way for its implementation

Synthesis of numerical methods for the design of segmental tunnel lining

International audienceThis paper presents a numerical study that aims to compare the behavior of the segmental tunnel lining using the direct, indirect and experimental methods. This model is based on a practical case applied in university of Tongji: a project of water conveyance tunnel. A reduction in the bending moment and increasing of the displacement in the tunnel lining is showed in numerical results, when taking into account the effect of the joints. It has been shown that the number of joints in the tunnel-lining structure highly affects the results in terms internal forces and displacements. Furthermore, the internal forces obtained by the continuous method are high compared to the other methods when the effects on segmental joints on tunnel lining behaviour are usually considered. Additionally, the bending moment of the direct method with behaviour of rotation spring linear and experimental method is comparable