Numerical Laplace–Fourier transform inversion technique for layered soil consolidation problems; II,Gibson soil layer     

T. Harnpattanapanich  I. Vardoulakis 《国际地质力学数值与分析法杂志》1987,11(1):103-112

The numerical Laplace–Fourier transformation technique previously presented by the authors¹¹ is used here for solving the consolidation problem of a finite inhomogeneous soil layer whose shear modulus is increasing linearly with depth. Parametric studies are performed and the results are critically discussed.  相似文献   

Torsional surface waves in inhomogeneous elastic media     

I. Vardoulakis 《国际地质力学数值与分析法杂志》1984,8(3):287-296

The dispersion of torsional surface waves in two types of inhomogeneous elastic media is discussed (1) in a half-space with shear modulus varying linearly with depth and with constant density (Gibson'S half-space) and (2) in a half-space with shear modulus varying with the square-root of the depth co-ordinate and with constant density. Inhomogeneous media with constant shear wave velocity are also reviewed and the obtained solutions are discussed in relation to appropriate boundary conditions.  相似文献   

Bifurcation analysis of deep boreholes: II. Scale effect     

P. C. Papanastasiou  I. G. Vardoulakis 《国际地质力学数值与分析法杂志》1989,13(2):183-198

This paper is a continuation of a previous one on bifurcation of deep boreholes under uniform stress at infinity,¹ and it focuses on the effect of borehole radius on borehole stability. Rock is described by the equations of a deformation theory of plasticity for cohesive-frictional, incompressible materials with Cosserat structure. The inhomogeneous bifurcation problem is formulated and the corresponding eigenvalue problem is solved numerically by the finite element method. It is demonstrated that the combined Cosserat and stress-gradient effects lead to an increase of the bifurcation stress with decreasing borehole radius (scale effect).  相似文献   

Development and validation of a novel-based combination operational air quality forecasting system in Greece   总被引：1，自引：1，他引：0  

Stamatis Zoras  Vasilios Evagelopoulos  Ioannis Pytharoulis  Georgios Kallos 《Meteorology and Atmospheric Physics》2010,106(3-4):127-133

In the present work, a model combination is developed in order to provide the public, in north-western Greece, with the next day air quality forecast. Generally, the development and deployment of a real-time numerical air quality prediction system is technically challenging while even more in complex terrain. The Air Pollution Model (TAPM) (http://www.cmar.csiro.au/research/tapm) is a hydrostatic prognostic mesoscale model. It has been calibrated for the area in recent studies and used in air quality assessments. In 2007, TAPM has started operating in a real-time operational mode for the prediction of next day’s weather forecast, particulate matter (PM₁₀ with an aerodynamic diameter <10 μm) daily average concentration and Air Pollution Indexes. The model setup is a link up between TAPM and SKIRON modeling system (http://forecast.uoa.gr).  相似文献   

Pile foundation analysis and design using experimental data and 3-D numerical analysis   总被引：1，自引：0，他引：1  

Emilios M. Comodromos  Mello C. Papadopoulou  Ioannis K. Rentzeperis 《Computers and Geotechnics》2009

Capacity based design of pile foundations limits the soil-structure interaction mechanism to group bearing capacity estimation, neglecting, in most cases, the contribution of the raft. On the other hand, a straightforward, nonlinear, 3-D analysis, accounting for soil and structural nonlinearities and the effects arising from pile–soil–pile interaction, would be extremely high CPU-time demanding and will necessitate the use of exceptionally powerful numerical tools. With the aim of investigating the most efficient, precise, and economical design for a bridge foundation, a hybrid method, compatible with the notion of sub-structuring is proposed. It is based on both experimental data and nonlinear 3-D analysis. The first step to achieve these targets is a back-analysis of a static pile load test, fitting values for soil shear strength, deformation modulus, and shear strength mobilization at the soil–pile interface. Subsequently, the response of 2 × 2 and 3 × 3 pile group configurations is numerically established and the distribution of the applied load to the raft and the characteristic piles is discussed. Finally, a design strategy for an optimized design of pile raft foundations subjected to non-uniform vertical loading is proposed.  相似文献   

Magnitude of latent heat in thermally loaded clays     

Sergio Samat  Laurent Brochard  Ioannis Stefanou 《国际地质力学数值与分析法杂志》2020,44(14):1926-1957

Temperature changes are known to induce specific couplings in clay, in particular, an anomalously high thermal pressurization in undrained conditions or a thermal compaction in drained conditions, both of which are potential threats for the mechanical stability and sealing capacity of the geomaterials. Thermodynamical analysis of those peculiar thermomechanical couplings points to a potentially important latent energy, which in turn could limit the temperature change upon heating or cooling. The direct measurement of latent energy developed during a laboratory geomechanical test is challenging. Instead, proper identification of thermal hardening in conventional experiments with temperature changes provides an alternative route to estimate latent energy. In this work, existing laboratory thermomechanical tests of clays are analyzed with a rigorous thermodynamic framework to quantify the magnitude of latent energy in thermomechanically loaded clays. A thermodynamically consistent constitutive model for fully saturated clays that combines two key features, (a) the temperature dependence of the blocked energy and (b) the framework of bounding plasticity, is proposed. The performance of the model is validated by reproducing results obtained in laboratory tests for Boom and Opalinus clays. The thermomechanical loads considered to validate the model performance were then used to estimate the percentage of work that remains latent in the clayey material during plastic yielding. We find that the magnitude of latent energy is quite significant, typically a few tens of percent of the total dissipated energy, and increases significantly with temperature. Accordingly, it is expected to play an important role in the thermomechanical response of clays.  相似文献   

Empirical seismic vulnerability assessment of Icelandic buildings affected by the 2000 sequence of earthquakes     

Ioanna Ioannou  Bjarni Bessason  Ioannis Kosmidis  Jón Örvar Bjarnason  Tiziana Rossetto 《Bulletin of Earthquake Engineering》2018,16(12):5875-5903

In June 2000, two Mw6.5 earthquakes occurred within a 4-day interval in the largest agricultural region of Iceland causing substantial damage and no loss of life. The distance between the earthquake epicentres and the fault rupture was approximately 15 km. Nearly 5000 low-rise residential buildings were affected, some of which were located between the faults and exposed to strong ground motion from both events. The post-earthquakes damage and repair costs for every residential building in the epicentral region were assessed for insurance purposes. The database is detailed and complete for the whole region and represents one of the best quality post-earthquake vulnerability datasets used for seismic loss estimation. Nonetheless, the construction of vulnerability curves from this database is hampered by the fact that the loss values represent the cumulative damage from two sequential earthquakes in some areas, and single earthquakes in others. A novel methodology based on beta regression is proposed here in order to define the geographical limits on areas where buildings sustained cumulative damage and predict the seismic losses for future sequence of events in each area. The results show that the average building loss in areas affected by a single event is below 10% of the building replacement value, whilst this increases to an average of 25% in areas affected by the two earthquakes. The proposed methodology can be used to empirically assess the vulnerability in other areas which experienced sequence of events such as Emilia-Romagna (Italy) in 2012.  相似文献   

Coupled wellbore erosion and stability analysis     

M. Stavropoulou  P. Papanastasiou  I. Vardoulakis 《国际地质力学数值与分析法杂志》1998,22(9):749-769

This paper extends earlier work on sand erosion and presents an attempt to couple sand erosion to mechanical damage of rock around a wellbore. Porosity which evolves in time and space as surface erosion progresses, is chosen as the coupling parameter. Both rock elasticity and strength (cohesion) are assumed to depend on porosity in such a way that the material becomes weaker with increasing porosity. The mathematical model, consists of erosion equations, mixture flow equations and stress equilibrium equations, is solved numerically by Galerkin finite element method. Numerical results suggest that erosion, resulting in sand production, is high close to the free surface. Erosion is accompained by changes in porosity and a significant permeability increase. Erosion in the vicinity of the wellbore induces alterations in the mechanical behaviour of the medium. Weakening of rock stiffness leads to severe alteration of both effective stresses and pore pressure near the cavity. Since cohesion decreases with increasing porosity, one can also identify the time instant at which rock mechanical failure starts. © 1998 John Wiley & Sons, Ltd.  相似文献   

An integrated macroelement formulation for the dynamic response of inelastic deformable rocking bodies     

Evangelos Avgenakis  Ioannis N. Psycharis 《地震工程与结构动力学》2020,49(11):1072-1094

This paper presents a macroelement formulation for the prediction of the planar dynamic response of inelastic deformable rocking bodies. The formulation is based on a previous macroelement developed by the authors able to describe the cyclic response of inelastic rocking bodies, which takes into account the deformability both along the height of the member, as well as near the rocking end. Modifications of this formulation to account for other motion modes of rocking members during their dynamic response, namely, sliding and upthrow, as well as modifications to account for damping in a uniform manner during the whole motion, including impacts, are introduced. The dynamic response predicted by the macroelement for free-standing rigid and deformable rocking bodies is presented and compared with existing theoretical solutions, and the effect of deformability, damping, inelasticity, and friction on the response is discussed.  相似文献   

Efficient strong motion duration of pulse-like records for nonlinear structural analyses     

Constantinos C. Repapis  Petros P. Mimoglou  Vicky V. Dimakopoulou  Ioannis N. Psycharis  Ioannis M. Taflampas 《地震工程与结构动力学》2020,49(5):479-497

The special interest produced by near-field directivity records and their effect on structural response has given a new significance in the velocity time history, its pulse-like content, and relevant parameters and indices. Recent research has shown that directivity pulses inherent in these records govern the linear and the nonlinear response of a wide range of structures. Based on this observation, it is suggested in this paper that a truncated ground motion, limited to the duration of the predominant velocity pulse, can be efficiently used to predict the structural response, instead of the base motion with the total duration, reducing significantly the required runtimes. The proposed methodology is verified for a series of medium to high rise reinforced concrete buildings, for which nonlinear time-history analyses are performed for a vast suite of pulse-like near-field records applied as base excitations with their total duration and the proposed truncated one. Comparison of the results for the response displacements and forces shows very good agreement, permitting the acceptance of the pulse duration as the efficient strong motion time interval of the original record, which determines the response and, thus, it can be used for nonlinear structural analyses.  相似文献