The determination of the non-linear behaviour of multivariate dynamic systems often presents a challenging and demanding problem. Slope stability estimation is an engineering problem that involves several parameters. The impact of these parameters on the stability of slopes is investigated through the use of computational tools called neural networks. A number of networks of threshold logic unit were tested, with adjustable weights. The computational method for the training process was a back-propagation learning algorithm. In this paper, the input data for slope stability estimation consist of values of geotechnical and geometrical input parameters. As an output, the network estimates the factor of safety (FS) that can be modelled as a function approximation problem, or the stability status (S) that can be modelled either as a function approximation problem or as a classification model. The performance of the network is measured and the results are compared to those obtained by means of standard analytical methods. Furthermore, the relative importance of the parameters is studied using the method of the partitioning of weights and compared to the results obtained through the use of Index Information Theory.

No abstract

No abstract

A closed-form solution for the problem of the plastic zone and stress distribution around a circular tunnel in an elastic-plastic half space, derived using bipolar coordinates, is the main scope of this paper. By assuming a uniformly applied surface loading, the whole semi-infinite space is under uniform pressure: thus the gravitational effect is neglected, while the plastic zone formation around the circular tunnel is controlled by the applied internal support pressure. The plastic behaviour of the half space is described by the Mohr-Coulomb yield criterion, and the soil is assumed to be homogeneous and isotropic with earth pressure coefficient K 0 equal to unity. The critical internal pressure, where the initial yielding occurs at the tunnel wall, is derived, along with equations describing the plastic zone and plastic stresses. These equations are functions of the soil properties, which are cohesion and friction angle. This derived closed-form solution is validated through mathematical and computational analysis, and is also compared with numerical models under gravitational load, solved using the finite difference method. This innovative closed-form solution has a significant impact in practical problems by introducing a simple and effective method that allows the quick estimation of a shallow tunnel's behaviour, since it gives, in principle, the opportunity for quick and accurate calculation of the plastic zone and stress distribution around the circular tunnel. By applying different values of support pressure, the tunnel designer can easily evaluate the feasibility of different design alternatives, such as shotcrete shell and tunnel-boring machine support pressure. As a result, an efficient and innovative method of solving shallow tunnelling problems in cohesive-frictional soil is introduced.Le principal objet de la présente communication est une solution de forme close pour le problème de la zone plastique et de la distribution des tensions autour d'un tunnel dans un demi-espace élasto-plastique, dérivé en utilisant des coordonnées bipolaires. En supposant une charge alaire appliquée de façon uniforme, l'intégralité de l'espace semi infini se trouve sous une pression uniforme, en raison de laquelle l'effet gravitationnel est négligé, tandis que la formation de la zone plastique autour du tunnel circulaire est contrôlée par l'application de la pression de support interne. Le comportement plastique du demi-espace est décrit par le critère de limite élastique de Mohr-Coulomb, et le sol est supposé être homogène et isotrope, le coefficient de pression de la terre K o étant égal à l'unité. La pression interne critique, où le rendement initial survient sur la paroi du tunnel, est dérivée, de même que des équations décrivant la zone plastique et les contraintes plastiques. Ces équations sont des fonctions des propriétés du sol, à savoir la cohésion et l'angle de frottement. Cette solution de forme close dérivée est validée à travers des analyses mathématiques et computationnelles, et est également comparée avec d...

No abstract