Search results for "Trench"
showing 10 items of 33 documents
The Impact of a Very Weak and Thin Upper Asthenosphere on Subduction Motions
2019
Recent geophysical observations report the presence of a very weak and thin upper asthenosphere underneath subducting oceanic plates at convergent margins. Along these margins, trench migrations are significantly slower than plate convergence rates. We use numerical models to assess the role of a weak upper asthenospheric layer on plate and trench motions. We show that the presence of this layer alone can enhance an advancing trend for the motion of the plate and hamper trench retreat. This mechanism provides a novel and alternative explanation for the slow rates of trench migration and fast-moving plates observed globally at natural subduction zones.
Hydraulic conductivity and strength of pervious concrete for deep trench drains
2019
Abstract Pervious concrete for deep trench drains, used to stabilise slopes, must meet many requirements, namely, adequate hydraulic conductivity, adequate shear strength a few days after pouring, capacity to act as a protective filter for soils in which the drain is installed, good resistance to clogging and adequate residual hydraulic conductivity. In current engineering practice, the composition of pervious concrete for drains is improperly selected according to criteria used for no-fines concrete for road pavements. To detect more suitable and specific criteria, a laboratory investigation has been conducted aimed at identifying the composition and the properties of pervious concrete sat…
Long Term Efficiency Analysis of Infiltration Trenches Subjected to Clogging
2018
Abstract: In recent years, limitations linked to traditional urban drainage schemes have been pointed out and new approaches were developed introducing more natural methods for retaining and/or disposing of stormwater. Such practices include infiltration and storage tanks in order to reduce the peak flow and retain part of the polluting components. The impact of such practices on stormwater quantity and quality is not easily assessable because of the complexity of physical and chemical processes involved. In such cases, integrated urban drainage models may play a relevant role providing tools for long term analysis. In this study, the effect of the clogging phenomenon has been assessed by m…
The Permeable Concrete: A Low Energy Consumption Solution for Deep Draining Trenches
2018
The reduction of pore water pressures is one of the very effective measures to improve the stability conditions of marginally stable water-bearing slopes or to stabilise landslides. For this purpose the trench drains have been used long since. Like filling material of deep trenches the permeable concrete can be effectively employed. It presents relatively high hydraulic conductivity, filtering capacity in order to prevent the internal erosion of the soil in which the trench drain is installed, enough residual hydraulic conductivity after possible clogging, sufficient shear strength after a short curing time to avoid the instabilisation of adjacent previously built panels or piles. Results o…
CEOs entrenchment and shareholders' wealth
1998
In the agency relation between the shareholders and the CEO, everybody try toreinforce his or her position. For the CEO, it means the pursuit of a betterentrenchment, which allows him to reduce the risk of being dismissed. Theentrenchment model develops the importance for the CEO to get internal or externalconnections and to make efforts in order to attain a higher performance. From a sampleof 1747 annual observations concerning 258 CEOs of public firms for the 1966-1990period, empirical measures allow us to estimate the importance of internal networksand past performance by establishing a measure of CEO entrenchment. Furthermore,we observed, for the shareholders, the existence of an optimu…
Colonisation process of vegetative fragments of Posidonia oceanica (L.) Delile on rubble mounds
2005
Seagrass colonise new areas via the dispersion of seeds or vegetative fragments. Independent of the manner of colonization, habitat requirements need to be met for the successful establishment of seagrasses. Here we report on the colonization process of Posidonia oceanica in a highly disturbed area: a gas pipeline trench at Capo Feto (SW Sicily, Italy). A trench dredged through a P. oceanica bed was back-filled with rubble added from dump barges leading to the formation of a series of rubble mounds on the seabed. Over time, these mounds became colonised with P. oceanica. In order to understand the pattern of P. oceanica colonization, shoot density was quantified over 3 years (2001-2003) on …
An experimental investigation into the permeability and filter properties of pervious concrete for deep draining trenches
2018
The reduction of pore water pressures is one of the most effective measures that can be taken to stabilise landslides or to improve the stability conditions of marginally stable water-bearing slopes. To this end, draining trenches have been used long since. When deep trenches are needed, the usual conventional construction techniques fail and recourse must be made to secant piles or to adjacent vertical panels built by means of the methods well established for diaphragm walls. However, unbonded materials cannot be used, since the excavation of a panel adjacent to previously built ones will instabilise these latter. The problem can be solved using pervious concrete rather unbonded material. …
Uncertainty and cross-border banking flows
2019
Abstract While global uncertainty—measured by the VIX—has proven to be a robust global “push” factor of international capital flows, there has been no systematic study assessing the role of uncertainty in driving bilateral capital flows. This paper examines the effects of higher country-specific uncertainty on cross-border banking flows using data from the Bank for International Settlements Locational Banking Statistics. The bilateral structure of this data allows disentangling supply factors from demand factors, thereby helping identify the effect of higher uncertainty on cross-border banking flows from other confounding factors. The results of this analysis suggest that: (i) uncertainty i…
Successful turnarounds in bankrupt firms? Assessing retrenchment in the most severe form of crisis
2019
During economic downturns, firms file for bankruptcy in an effort to attempt a “turnaround.” The objective of this study is to assess the effectiveness of retrenchment strategies in the context of bankruptcy, as the most severe form of crisis. We conducted a longitudinal analysis of a sample of 868 bankrupt Spanish firms during the period 2004–2017. The empirical results show that stakeholder support and deep cost retrenchment increase the likelihood of survival and performance recovery, while aggressive layoffs are detrimental for turning bankrupt firms around. Surprisingly, intense asset retrenchment had no significant effects on firm survival and also pushed performance downward. The fi…
Biological groundwater denitrification systems: Lab-scale trials aimed at nitrous oxide production and emission assessment
2018
Bio-trenches are a sustainable option for treating nitrate contamination in groundwater. However, a possible side effect of this technology is the production of nitrous oxide, a greenhouse gas that can be found both dissolved in the liquid effluent as well as emitted as off gas. The aim of this study was to analyze NO3 − removal and N2O production in lab-scale column trials. The column contained olive nut as organic carbon media. The experimental study was divided into three phases (I, II and III) each characterized by different inlet NO3 − concentrations (30, 50, 75 mg NO3-N L−1 respectively). Sampling ports deployed along the length of the column allowed to observe the denitrification pro…