Isam Shahrour

A full 3-D finite element analysis of tunneling adjacent structures interaction

Abstract This paper concerns a study of the interaction between tunneling in soft soils and adjacent structures. Analysis is performed using a full three-dimensional finite element model, which takes into consideration the presence of the structure during the construction of the tunnel. The soil behavior is assumed to be governed by an elastic perfectly-plastic constitutive relation based on the Mohr–Coulomb criterion with a non-associative flow rule. The paper is composed of three parts. The first part describes the numerical model used in this study, the second part concerns a full three-dimensional analysis of the construction of a shallow tunnel close to a two level building. The last part includes comparison between the full 3D analysis and a simplified approach, which neglects the influence of the presence of the structure in the determination of the tunneling-induced ground movement.

Use of artificial neural network simulation metamodelling to assess groundwater contamination in a road project

The estimation of the extent of a polluted zone after an accidental spill occurred in road transport is essential to assess the risk of water resources contamination and to design remediation plans. This paper presents a metamodel based on artificial neural networks (ANN) for estimating the depth of the contaminated zone and the volume of pollutant infiltration in the soil in a two-layer soil (a silty cover layer protecting a chalky aquifer) after a pollutant discharge at the soil surface. The ANN database is generated using USEPA NAPL-Simulator. For each case the extent of contamination is computed as a function of cover layer permeability and thickness, water table depth and soil surface-pollutant contact time. Different feedforward artificial neural networks with error backpropagation (BPNN) are trained and tested using subsets of the database, and validated on yet another subset. Their performance is compared with a metamodelling method using multilinear regression approximation. The proposed ANN metamodel is used to assess the risk for a DNAPL pollution to reach the groundwater resource underneath the road axis of a highway project in the north of France.

An elastoplastic constitutive relation for the soil-structure interface under cyclic loading

Abstract This paper includes a presentation of cyclic interface tests performed with smooth and rough surfaces on loose and dense silica sand under either a constant value of the normal stress or a zero normal displacement. These tests are then used for the elaboration of an elastoplastic constitutive relation based on the bounding surface with two families of surfaces. The constitutive relation is checked over cyclic tests performed with rough interface on both loose and dense sands.

Application of Artificial Neural Networks (ANN) to model the failure of urban water mains

This paper presents an application of Artificial Neural Networks (ANN) to model the failure rate and estimate the optimal replacement time for the individual pipes in an urban water distribution system. The performances of the ANN are examined using a 14-year data set collected in a city in the north of France. The first part of the paper presents the collected data. The second part describes the construction and validation of six ANN models. After a discussion of the performances of these models, they are used for the prediction of water mains failure and the determination of the benefit index, which allows optimization of investment for the rehabilitation and maintenance of urban water mains. The spatial repartition of the risk of degradation is illustrated using a geographic information system, which constitutes an effective tool for the elaboration of strategies of rehabilitation of water distribution systems.

Study of the swelling behavior of a compacted soil using flexible odometer

Abstract This paper includes an experimental study of the swelling behavior of a compacted soil. The study is performed using a flexible odometer, which allows for lateral deformation during soil expansion and the measurement of the lateral swell pressure. The paper is composed of two parts. The first one describes the flexible device used in this study while the second presents experimental results and discusses the influence of the rigidity of the odometer ring on the swelling behavior of a compacted soil.

Calculation of marine foundations subjected to repeated loads by means of the homogenization method

Abstract This paper refers to the calculation of foundations of marine structures subjected to a large number of repeated loadings by means of the homogenization procedure. Assuming that the soil behaviour is elasto-visco-plastic, an asymptotic development with regard to the time variable shows that such a calculation is equivalent to the resolution of a creep problem. The fundamental bases of the homogenization method are first presented, then its introduction in the finite element program FONDOF is described. The validity of this method is studied through some examples: repeated undrained triaxial paths and a marine foundation subjected to repeated loads. In each example, numerical results obtained by the homogenization procedure are compared with those obtained by the classical incremental method.

Etude de la stabilité des murs en terre armée sous chargements sismiques

ABSTRACT We purpose to study the stability of reinforced earth walls subjected to seismic loading within the framework of conventional pseudo-static analysis applied to homogenous material. Firstly, we present a study of the stability of reinforced earth walls within the framework of the limit analysis. Secondly, we use the Newmark method for the determination of displacement field induced by seismic loading. Results of numerical simulations show a significant contribution of the reinforcement in the improvement of the resistance of reinforced walls to seismic loading.

Study of massive water injection by thermoporomechanical coupling model

Abstract In this paper, we present a numerical study of the massive water injection in petroleum reservoir. A finite element model is developed using a complete coupling algorithm. The thermal convective effect is taken into account. This allows to deal with high fluid flow rate and high temperature variation during the injection time. Evolutions of pore pressure, temperature and rock compaction as function of injection time are studied. A particular objective of this study is to evaluate importances of different terms of thermoporomechanical coupling in this kind of problems. The obtained results show that it is possible to use a semi-decoupled model by eliminating some negligible coupling terms.

Validation file for an elastoplastic-strain hardening model of soil behaviour

Abstract A validation file for the modified Nova and Wood elastoplastic model is presented. A short description of the model and of a methodology for the determination of constitutive parameters is outlined. The validation of the model is first carried out on homogeneous tests (conventional triaxial and true-triaxial) and then on boundary value problems (shallow foundations tests performed in a calibration chamber and in a centrifuge, respectively), Finally, the sensitivity of the model with regard to some factors which affect the prediction of the foundation behaviour (e.g. determination of constitutive parameters and numerical integration order) is analysed.

Virtual DMA Municipal Water Supply Pipeline Leak Detection and Classification Using Advance Pattern Recognizer Multi-Class SVM

Abstract In this paper we investigated and analyzed the concept of virtual district metered area (DMA) as the core objective of the research to resolve the current gap and limitations of the actual district metered area state of practice through the development of virtual district metered area pipeline leak detection and classification system using multi-class support vector machine (SVM) advanced pattern recognizer at Lille University water supply pipeline networks study area the so called “Zone-6”. The SVMs were trained on multiple cases representing the presence of leaks in various sizes and locations. The research results, and analysis showed a rather promising performance, which could be successfully implemented. Moreover, the proposed method could enable the water utility companies and other stakeholders to further reduce risks associated with pipeline leaks or breaks. This method also can be used during decision-making process for selecting which pipeline requires urgent action, and engineer the optimal short-term response or alternative for maintenance strategies. Furthermore, the proposed methodology could benefit the water utility companies by reducing the cost and operational drawbacks associated with implementing the actual district metered area (DMA). It also improve the day to day operational decision making process by detecting and classifying the different stages of pipelines leaks and breaks according to their severity, which can enable the operators to see the behavior of the network on the control room screens they are familiar with and enable them to quickly perform the best short term response strategy.