Search results for "Geomatic"
showing 10 items of 506 documents
The open metastable structure of a collapsible sand: fabric and bonding
2015
This paper deals with the compositional and textural characteristics determining open metastable structures in the pleistocenic sand outcropping in the Agrigento district (Sicily). The aim of the study was to individuate the bonding types occurring between grains that could generate matric suction phenomena. The composition and microfabric were characterised by means of granulometry, porosimetry, permeability, optical and ESEM-EDS microscopy, thermogravimetry and XR diffractometry, electric conductivity, and ionic chromatography. The data thus acquired show that the skeleton of the sand is constituted mostly by bioclasts and microfossils, calcite and quartz monocrystalline grains. Moreover,…
Comparison of fully non-stationary artificial accelerogram generation methods in reproducing seismicity at a given site
2020
Abstract Seismic input modelling is a crucial step when Non-Linear Time-History Analyses (NLTHAs) are performed, the seismic response of structures being highly responsive to the input employed. When natural accelerograms able to represent local seismicity are not available, the use of generated accelerograms is an efficient solution for input modelling. The aim of the present paper is to compare four methods for generating fully non-stationary artificial accelerograms on the basis of a target spectrum, identified using seven recorded accelerograms registered in the neighbourhood of the construction site during a single event, assumed as target accelerograms. For each method, seven accelero…
Water retention and swelling behaviour of granular bentonites for application in Geosynthetic Clay Liner (GCL) systems
2016
Geosynthetic Clay Liner (GCL) systems are used as efficient hydraulic barriers in landfills for the disposal of hazardous municipal wastes. Along with geotextiles, bentonite materials are chosen as one of the primary components of GCLs due to their high retention, adsorption, and swelling capacities. GCLs are manufactured using bentonites at a high total suction and hydrated through the uptake of liquid from the subsoil and the confined material as soon as they are installed. Bentonites may exhibit considerable volume change upon wetting. Depending on the confinement stress, the void ratio may significantly increase with a decrease in suction, particularly at higher degrees of saturation. T…
Experimental study of a naturally weathered stiff clay
2016
Studying the shear strength of a naturally weathered clay is important to understand rain-induced slope failures in weathered soils. However, experimental studies on naturally weathered soils are limited. The paper focuses on the laboratory experimental investigation carried out to analyse the shear strength of a naturally weathered stiff clay that can be found in unsaturated conditions in situ. This has an important practical relevance in the evaluation of the stability conditions of natural slopes at clay outcrops. Different experimental techniques of suction measurement were used to obtain the soil-water retention curve of the clay over a wide range of suctions. Scanning electronic micr…
The bearing capacity of footings on sand with a weak layer
2017
Minor details of the ground, such as thin weak layers, shear bands and slickensided surfaces, can substantially affect the behaviour of soil–footing and other geotechnical systems, despite their seeming insignificance. In this paper, the influence of the presence of a thin horizontal weak layer on the ultimate bearing capacity of a strip footing on dense sand is investigated by single-gravity tests on small-scale physical models of the soil–footing system. The test results show that the weak layer strongly influences both the failure mechanism and the ultimate bearing capacity if its depth is lower than about four times the footing width. It is found that the presence of a thin weak layer …
A risk assessment proposal for underground cavities in Hard Soils-Soft Rocks
2018
Abstract Underground calcarenite quarries in Marsala (Sicily) have been involved in a number of collapses that have, seriously damaged numerous buildings. The stability conditions were therefore examined in order to assess risk conditions within the historical centre of the town and the surrounding areas, which are subject to urban expansion. Starting with an extensive collection of historical information, the research was carried out through surveys of the cavities, systematic sampling of material, petrographic analysis and geotechnical testing. The results of laboratory tests and in situ investigations provided a geotechnical characterization of both the intact material and the rock mass.…
On the reactivation of a large landslide induced by rainfall in highly fissured clays
2018
Abstract The paper discusses the field investigations, geotechnical characterization and time evolution of horizontal displacements in a wide landslide. The latter, triggered by an earthquake occurring in September 2002, is located in Sicily and involves a thick body of stiff and highly fissured clays belonging to a Varicoloured Clay formation. In order to characterise the reactivation of landslide mechanisms induced by rainfall, a three-year monitoring programme (2008–2011) was implemented to measure rain, pore water pressures, and deep and superficial displacements. The monitoring data made it possible to recognize three distinct landslides, which evolve at variable rates in different dir…
Role of particle characteristics in the compression behaviour of gap-graded sands
2019
Abstract The compression in gap-graded mixtures of sands with combined mineralogy has been investigated in recent research, focusing on the key factors that might imply the occurrence of convergent or non-convergent paths in compression (i.e., transitional or non-transitional behaviour). From previous work, the mineralogy of a matrix composed of larger grains seems to determine the possibility of the occurrence of transitional behaviour. Hence, if there is a strong and stiff matrix made of quartz sand particles, which are either larger than or at least of similar size to the other component, then non-convergent compression paths (i.e., transitional behaviour) are likely to occur. As a furth…
An attraction-based cellular automaton model for generating spatiotemporal population maps in urban areas
2015
We develop a cellular automaton (CA) model to produce spatiotemporal population maps that estimate population distributions in an urban area during a random working day. The resulting population maps are at 50 m and 5 minutes spatiotemporal resolution, showing clearly how the distribution of population varies throughout a 24-hour period. The maps indicate that some areas of the city, which are sparsely populated during the night, can be densely populated during the day. The developed CA model assumes that the population transition trends follow dynamics and propagation patterns similar to a contagious disease. Thus, our model designed to change the states of each grid cell (stable or dynami…
Compensation of Oxygen Transmittance Effects for Proximal Sensing Retrieval of Canopy–Leaving Sun–Induced Chlorophyll Fluorescence
2018
Estimates of Sun–Induced vegetation chlorophyll Fluorescence (SIF) using remote sensing techniques are commonly determined by exploiting solar and/or telluric absorption features. When SIF is retrieved in the strong oxygen (O 2 ) absorption features, atmospheric effects must always be compensated. Whereas correction of atmospheric effects is a standard airborne or satellite data processing step, there is no consensus regarding whether it is required for SIF proximal–sensing measurements nor what is the best strategy to be followed. Thus, by using simulated data, this work provides a comprehensive analysis about how atmospheric effects impact SIF estimations on proximal sensing, regarding: (…