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Effects of progressive strength degradation on seismic-induced displacements of rock slopes
No full textSeismic performance of slopes is typically assessed by evaluating the permanent displacements as a function of some earthquake response representative parameters. This paper presents the main results of a numerical study devoted to the evaluation of the influence of the progressive material strength reduction (from peak to ultimate values) induced by shear displacements on the seismic performance of jointed rock slopes. The parametric study refers to the simple one–dimensional problem of a rock slope characterized by the presence, at some fixed depth, of one planar joint. A simple modification of the Newmark rigid block model has been adopted in order to simulate the reduction of shear strength; different problem geometries (joint angle and depth) were considered in evaluating the distribution of permanent displacements induced by a selection of accelerometric records. Results seems to indicate that semiempirical relationships developed with reference to the original Newmark model (with constant shear strength) may be considered valid also in the case of gradually reducing shear strength, if the final value of yield acceleration is properly estimated. With increasing initial joint roughness only minor differences in the distribution of permanent displacements as obtained from constant or reducing shear strength rigid block models were found
Seismic Performance of Multi-propped Retaining Structures
No full textThe performance of retaining walls with multiple levels of props are typically evaluated numerically since it is a typical soil-structure interaction problem which cannot be expressed in a closed form. Under seismic conditions, the soil-structures interaction problem may require the evaluation of the permanent displacements or deformations developing to dissipate the earthquake energy through the formation of some possible kinematic mechanism. The latter cannot occur for multi-propped retaining structures unless yielding of one or more structural elements is achieved. In this paper, the dynamic behavior of a multi-propped embedded retaining structures is studied varying the characters of the input seismic motion. For this purpose, the results of several numerical dynamic analyses, carried out under plane-strain conditions and in the time domain, are presented and discussed. The results of the analyses indicate a very complex response of the system due to the effects of local seismic response and soil-structure interaction phenomena. However, it was possible to identify the main characters of motion that influence the system’s response in terms of resulting actions on structural elements. In particular, the analytical relationships presented in this work confirm that the effect of the frequency content of the seismic input compared to the natural frequencies of the soil profile and the geometry of the system are dominant. While peak ground acceleration seems to be appropriate to estimate the maximum (and instantaneous) increase of bending moments, Arias intensity seems to be a more effective parameter in order to evaluate the residual post seismic bending momen
EVALUATION OF DAMAGE IN MASONRY BUILDINGS DUE TO TUNNELING IN CLEYEY SOILS
No full textThis paper presents the first results of a numerical study aimed at the evaluation of tunneling-induced damage in masonry buildings in which the effect of soil-tunnel-building interaction was considered at different levels. Two-dimensional analyses were carried out using a simple elasto-plastic model for the soil; the masonry was modeled following a sort of ‘discontinuous’ approach, as elastic macro elements connected by vertical and horizontal elasto-plastic interfaces. The results of the analyses confirmed the importance of accounting the soil-tunnel-structure interaction to predict correctly the amount of damage
PREDICTION OF GROUND SETTLEMENTS DUE TO TUNNELING IN CLEYEY SOILS USING ADVANCED CONSTITUTIVE SOIL MODEL: A NUMERICAL STUDY
No full textMulti-Objective Approaches to Cross-Asset Resource Allocation in Transportation Asset Management
No full textA visco-plastic constitutive model for soft clays: implementation and validation
No full textIn the present paper the main aspects of the problem of modelling the viscous behaviour of cohesive soils are discussed. The first part of the paper deals with the experimental evidence for viscods behaviour of soils and reviews the available approaches to theoretical modelling. In the second part an elastic-visco-plastic model is proposed. This is based on the assumption that the inelastic components of deformation can be divided into a time independent plastic component and a time dependent viscous component. Other characteristics of the model
are the assumption of the similarity of the plastic and viscous potentials and the use of an equivalent time that governs the rate of creep within the state boundary surface. ln the third part of the paper single element predictions of the model for typical laboratory tests are illustrated.
Given the high difficulty of distinguishing the viscous behaviour from the elasto-plastic behaviour in both laboratory and field experimental investigations a certain amount of numerical experimentation may be act as a guideline for the planning of laboratory tests. Finally, in the last part of the paper, two boundary value problems relevant. to geotechnical engineering, two-dimensional consolidation in axisymmetric and plane strain condition, were analysed following implementation of the model in a finite element code. ln particular, the solution of problems having complex sets of boundary conditions is dealt with in detail using the finite element technique
Effectivness of the fast flow algorithm: 2D consolidation benchmarks and tunneling application
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