Criteria for rapid sliding II.: thermo-hydro-mechanical and scale effects in Vaiont case

Thermally induced excess pore pressures have been included into a two-wedge evolutive model of Vaiont landslide. The problem requires the solution of a system of four coupled balance equations for the shear bands and the surrounding rock as well as the joint equation of motion of the entire slide. The model predicts the high velocities observed and is consistent with other data (slide geometry, residual strength, and conditions on the sliding surface). The interpretation of a sensitivity analysis suggests that there exists a threshold permeability band, in the range 10- 8 to 10- 10 m/s, which separates potentially fast motions from slow motions. This conclusion is maintained if the scale of the landslide is reduced.Peer ReviewedPostprint (author's final draft

Slope stability in slightly fissured claystones and marls

The final publication is available at Springer via http://dx.doi.org/10.1007/s10346-014-0526-5The paper deals with the behavior of some characteristic soft rocks found in the Iberian Peninsula. In geological terms, they belong to Tertiary basins, the Keuper period and the Jurassic-Cretacic transition. The discussion is organized around the following aspects: (a) the intact material and its brittle behavior; (b) the weathering action of atmospheric events; (c) the persistent discontinuities and scale effects; and (d) the modification of strength after failure. In all cases, instability phenomena are addressed in connection with several case histories. Regarding material brittleness and the initial stress state, two cases of first time failures are discussed. Practical implications concerning the selection of operative strength will be given. Field observations of the relevance of weathering and, also, on the rate of weathering, are given for a Weald claystone. Field observations emphasize the importance of sharp transitions between weathered and intact (or slightly weathered) levels. A recent long-term laboratory investigation on the nature of degradation will be summarized. Macroscopic variables such as stiffness and tensile strength have been found to be uniquely predicted by a degradation law in terms of the accumulated plastic deformations. Persistent discontinuities and, in particular, sedimentation planes play a dominant role to explain slope failures not related to the shallow failures, usually associated with weathered profiles. The strength of discontinuities in a Weald formation was investigated by means of tests performed at two scales. Finally, the evolution in time of residual strength induced by chemical actions, associated with groundwater flow, is highlighted in connection with actual field data of unstable slopes.Peer ReviewedPostprint (author's final draft

Criteria for rapid sliding I.: a review of Vaiont case

Vaiont slide has been represented by a model of two interacting evolutive wedges. Mass conservation during the motion implies that the upper wedge transfers mass to the lower one through an internal shearing plane. The model respects available in situ observations. It was formulated in dynamics terms. Outcomes of the analysis are the determination of safety factors of the valley before dam impoundment, and the calculation of run-out distance once the motion starts. Rock strength degradation as motion develops has also been included. This degradation, even if it is intense, was unable to explain the very high estimated landslide velocities.Peer ReviewedPostprint (author's final draft

Nicaraguan civil society caught in the pendulum's swing? Shifting roles from service delivery to lobbying and back

Until the end of the 1990s, Nicaragua was marked with social conflict and internal political struggles. From 2000 until 2006 Nicaragua experienced a relatively democratic period, in which the country drafted Poverty Reduction Strategy Papers (PRSPs) with participation of the civil society. In this period, the openness of the political system and the participatory dimension of the PRSPs helped to strengthen civil society and increase policy influencing. As a result a shift took place away from service delivery and towards more lobbying and advocacy. The election of Ortega in 2006 (Sandinista National Liberation Front (FSLN)) as president introduced the shrinking of this democratic space. From that moment onwards, donors encountered difficulties in dealing with the participation conditionality. At the same time, civil society organizations (CSOs) found it difficult to counterbalance the increasing undemocratic tendencies despite their efforts to organize mobilizations. This paper argues that the NAA, which pushes civil society into the watchdog role, is rather troublesome in contexts which are politically closing down. Imposing the single role of watchdog on civil society is ineffective. The NAA should not be treated as a rigid blueprint but, rather, as a guideline for policy implementation dependent on the actual situation in the country of concern.

Situació de la paràlisi cerebral a les illes

Abstract not availabl