The paper presents an experimental, theoretical and numerical approach in order to describe the effects of rock weathering on bonded geomaterials. The term rock weathering is used to refer to a number of chemical and physical phenomena that continuously transform a rock mass into granular soil. From an engineering point of view, rock weathering can be interpreted as a generalised decay of the mechanical properties of the original material. It acts at a constitutive level essentially by reducing the strength of the bonds joining the grains together. Such a material degradation can occur in a time scale which is comparable to the average life of engineering structures. Weathering can be crucial for what concerns the stability of slopes, cliffs and abandoned underground caves. In the experimental part of the paper micro and macro experimental investigations performed on calcarenite, a natural soft rock, are shown; short- and long-term debonding processes are identified as characterising rock weathering. A large set of hydro-chemo-mechanical data are recovered to properly characterise debonding processes by means of specific weathering tests. In particular, to reproduce long-term rock weathering in laboratory time, the progressive chemical debonding has been induced through the exposition of the rock to a uniform flow of an acid solution. In the theoretical part, it is shown how the progressive deterioration of the intergranular bonds due to weathering has been modelled satisfactorily by extending a strain hardening elastoplastic model by means of multiscale approach coupling hydro-chemo-mechanical processes. Such a model has been corroborated by simulating some tests of the previous part. Finally, in the numerical part of the work, some boundary value problems are presented, in which weathering effects cannot be neglected.
Jamei, M.; Guiras, H.; Olivella, S. European journal of environmental and civil engineering Vol. 19, num. 9, p. 1033-1058 DOI: 10.1080/19648189.2014.996670 Data de publicació: 2015-10 Article en revista
In some arid and semi-arid regions, different types of infrastructure assets suffer from degradation of the roads, the embankment failures, erosion due to cyclic hydraulic actions and the effects of rainfall infiltration on slopes. Typical cases, such as the national roads in the north-west of Tunisia (Beja city) have been affected dramatically. Recent landslide is manifested in this region, especially in a plastic clay soil. Stability problems are caused by soil saturation and the presence of abundant cracks which are developed after a long dry summer. In fact, due to geotechnical problems, the annual loss due to the damage is estimated at $1 million in Beja area (30 km(2)). The effect of rainfall infiltration into the unsaturated clay during wet seasons characterised by either long duration low intensity rain or short duration high intensity rain have been analysed. The elastoplastic Barcelona Basic Model (BBM) has been used and soil movements leading to slope failure were calculated according to the unsaturated state evolution. The effects of cyclic hydraulic paths on the yield function have also been investigated. The yield function evolution depends on the cohesion and the apparent consolidation stress variations. The numerical calculations were evaluated against the field measurement displacements.
Jiang, M.; Sun, C.; Rodriguez-Dono, A.; Zhang, N.; Shao, J. European journal of environmental and civil engineering Vol. 19, num. Sup. 1, p. S108-S118 DOI: 10.1080/19648189.2015.1064624 Data de publicació: 2015-01-01 Article en revista
This article investigates the time-dependent influence on the shear failure behaviour of parallel rock joints in the echelon arrangement due to chemical weathering, which can be treated as a generalised time-dependency of the rock material. A time-dependent parameter alpha, identifying the accumulated relative mass removal of bonding material, has been implemented into a novel distinct element method bond contact model. This model is based on a series of mechanical test on bonded aluminium rods with different bond geometries. The numerical direct shear test results of echelon rock joints characterised by different values of alpha show that increasing time-dependent parameter alpha can lead to a lower crack initiation and peak stresses. This is accompanied by a growing ratio of the microscopic compressive-shear-torsional (CST) bond failure number of bond failures to the total number of failures, except for the case without weathering influence. High values of alpha render the material bridge a weaker part to be cut through, generating a large number of CST bond breakages along the central shear axis.
This is an Accepted Manuscript of an article published by Taylor & Francis Group in [European Journal of Environmental and Civil Engineering] on [September 2015], available online at: http://www.tandfonline.com/10.1080/19648189.2015.1064624
Climent, N.; Arroyo, M.; O'Sullivan, C.; Gens, A. European journal of environmental and civil engineering Vol. 18, num. 9, p. 983-1008 DOI: 10.1080/19648189.2014.920280 Data de publicació: 2014-01-01 Article en revista
Sand production in oil wells is often predicted using continuum fluid-coupled models. However, a continuum approach cannot capture important features of the sanding problem, such as erosion and localised failure. This shortcoming of continuum-based analyses can be overcome using the particulate discrete element method (DEM). However, these models, apart from issues of computational cost, have the disadvantage of being difficult to calibrate. One way forward is to calibrate DEM models to capture the response observed in continuum models, where the material parameters can be selected with greater confidence. Adopting this philosophy here, a 3D numerical model based on DEM coupled with Computational Fluid Dynamics was built to simulate sand production around perforations. In the first instance, the basic DEM model (i.e. a dry case) is calibrated against a well-known poro-elastoplastic analytical solution by Risnes et al. (1982). Subsequently, a range of hydrostatic scenarios involving different levels of pore pressure and effective stress are considered. The numerical model shows an asymmetry of the eroded zone that is related to initial microscale inhomogeneity. The stress peak of the analytical solution at the elastic-plastic interface is smoothed because of that asymmetry. The presence of hydrostatic fluid decreases the plastic region and reduces the amount of sand produced. This is not due to changes in effective stress but rather by the particle-scale stabilizing effect of the fluid drag.
Limeira, J.; Agulló, L.; Etxeberria, M. European journal of environmental and civil engineering Vol. 16, num. 8, p. 906-918 DOI: 10.1080/19648189.2012.676376 Data de publicació: 2012 Article en revista
This work deals with the study of dredged marine sand (DMS) from the Port of Sant Carles de la Ràpita (Tarragona, Spain) as construction material. The analysis of its
influence on paste, mortar and concrete production is described. Two experimental phases were carried out after the chemical and physical characteristics of DMS were determined. Firstly, pastes and mortars were made using CEM II/A-M 42.5R cement, different
percentages of DMS in replacement of raw sand and plasticizer additive in order to obtain the fresh and hardened properties of the mixes studied. After that, DMS was used for the production of concretes as fine aggregates. A pilot study was carried out with harbor concrete pavements produced at industrial scale. The results were compared to those of the control mixes and proved the satisfactory behavior of DMS as construction material when incorporated into concrete as granular corrector.
M. Molero; Segura, I.; S. Aparicio; Fuente, J. European journal of environmental and civil engineering Vol. 15, num. 4, p. 501-517 DOI: 10.1080/19648189.2011.9693343 Data de publicació: 2011-10-04 Article en revista
We present in this paper a numerical model of the erosion of a soil that accounts for both the flow in the open fluid and the flow of fluid through the porous soil. The interface between the open fluid and the soil is represented using a level-set function, and the erosion is controlled by the shear stress vector. The evaluation of the approximate value of this gradient is particularly focused on, and an improved method, called XFE+ method, is presented. Numerical results in 2D and 3D illustrate the accuracy and the potentiality of this method.
This is an Accepted Manuscript of an article published by Taylor & Francis Group in "European journal of environmental and civil engineering" on 2011, available online at: http://www.tandfonline.com/doi/abs/10.1080/19648189.2011.9714848
Gens, A.; Garitte, B.; Olivella, S.; Vaunat, J. European journal of environmental and civil engineering Vol. 13, num. 7-8, p. 937-962 DOI: 10.3166/EJECE.13.937-962 Data de publicació: 2009 Article en revista
Deep geological disposal in suitable host rocks is the favoured strategy for the
storage and disposal of heat-emitting high level nuclear waste. A rational design of
repositories requires a good understanding of the interacting thermo-hydro-mechanical
phenomena that occur in the engineered barrier and adjacent rock. To this end, a
multiphysical formulation is described that allows the performance of coupled THM analyses capable of reproducing observed phenomena. The formulation and computer code is applied to the simulation of two large scale tests: a mine-by test involving the excavation of a shaft in an argillaceous rock and a large-scale high- temperature heating test in fractured rock.