Lucio Di Matteo

Compressibility of Kaolinitic Clay Contaminated by Ethanol-Gasoline Blends

In this work, oedometer tests were used to examine the effects of ethanol-gasoline blends on the consolidation characteristics of a kaolinitic soil from northwestern Spain. As the fraction of ethanol in blends increases, the equivalent liquid limit of soil decreases, showing a dividing point for blends containing about 85% of ethanol. By means of a database of compression indexes of remolded clayey soils mixed with differing kinds of alcohol and petroleum hydrocarbon contaminants, a multivariable model for estimating the compression index of the contaminated soil is presented, on the basis of the virgin compression index, normalized liquid limit, and normalized pore fluid viscosity. The model is valid only for percentages of active clays up to 10–15% in weight in kaolinitic soil. The authors would like to encourage others to further validate and refine the approach, which may be useful for preliminary estimation of the compression index of contaminated soils, reducing operators’ risk of inhaling vapors released by the ethanol-gasoline blends while performing the test and also reducing damage to conventional oedometer equipment.

Best-Fit Models to Estimate Modified Proctor Properties of Compacted Soil

Regression models were developed to estimate the optimum moisture content and maximum dry density of clayey and fine-grained soils using physical and index properties from 30 soil samples collected in Central Italy and 41 soils described in the literature. The liquid limit of the soils analyzed ranged between 18 and 82%, the plasticity index between 1 and 51%, and specific gravity between 2.47 and 3.09. The most significant regression variables were the specific gravity and the Atterberg limits. The developed models are accurate and can be used as a simple tool to approximate the maximum dry density and optimum water content of clayey and fine-grained soils.

Climatic characterization and response of water resources to climate change in limestone areas: some considerations on the importance of geological setting

AbstractThis work analyzes the response of springs fed by karst/fractured limestone aquifers, which extensively outcrop in central Italy, to climatic variations. In the central Italy area, climatic variations are represented by a general decrease in annual and winter precipitation. It is shown how groundwater regime, the discharge of springs, and their response to climate change depend to a great extent on the geologic and structural setting of the system. Some mountain springs of central Italy are local systems representing the overflow of a deeper regional flow feeding larger base springs, often of poor quality. A dynamic groundwater divide separates the recharge areas of base springs from those of local springs: if, due to low recharge, the piezometric surface lowers, the watershed moves toward systems located at higher altitudes, reducing their recharge areas. Therefore, local springs connected to a base flow are more vulnerable to climate change than those which are not. The Bagnara and Lupa springs,...

Liquid limit of low- to medium-plasticity soils: comparison between Casagrande cup and cone penetrometer test

For liquid limit determination, the European Standards require the cone penetrometer technique or, alternatively, the Casagrande cup method; but the latter is widely used in practice. As most European soil classification systems are not adapted to the new European Standards, a systematic study was carried out to verify the differences between the two techniques for liquid limit determination, examining clayey soils from various geologic units. Comparison of 100 liquid limit values ranging between 20 and 50% indicates that the liquid limit obtained by the fall cone method is generally 2.2% points higher than that obtained by the hard base Casagrande apparatus. Comparison of data from different sources consistently indicates that the equation proposed in this study may be useful in revising existing soil classification systems, avoiding problems of soil classification due to the technique used for liquid limit determination.RésuméPour la détermination de la limite de liquidité, les normes européennes recommandent la méthode du pénétromètre de consistance, ou bien la méthode de la coupelle de Casagrande; mais cette dernière méthode est largement utilisée en pratique. Comme la plupart des systèmes européens de classification des sols ne sont pas adaptés aux nouvelles normes européennes, une étude systématique a été réalisée pour analyser les différences entre les deux techniques pour la mesure de la limite de liquidité, examinant des sols argileux de différentes formations géologiques. La comparaison de 100 valeurs de limites de liquidité comprises entre 20% et 50% montre que la limite de liquidité obtenue à partir du pénétromètre de consistance est généralement supérieure de 2,2 points de pourcentage à celle obtenue à la coupelle de Casagrande. La comparaison avec des données de différentes sources indique clairement que l’équation proposée dans cette étude peut être utile pour la révision des systèmes de classification des sols, évitant ainsi des problèmes, dans ce domaine, qui seraient dus à la technique utilisée pour la détermination des limites de liquidité.

Climate change, water supply and environmental problems of headwaters: The paradigmatic case of the Tiber, Savio and Marecchia rivers (Central Italy)

River headwaters, in spite of their importance for habitats and water supply, are often inadequately studied and managed. This study discusses the effects of the hydrogeological system and climatic variations on the environment of Monte Fumaiolo (Central Italy), which corresponds to the headwaters of the rivers Tiber, Savio and Marecchia. The area is a key system for supplying drinking-water and is also the habitat of amphibians such as the endemic and endangered Bombina pachypus and other amphibian species. Ongoing climate change is affecting the area: during the last 30years, five prolonged droughts have occurred, against only one in the preceding 40years. On all time-scales, there is a decrease in rainfall during the recharge period and an increase of temperature: these trends correspond to a decrease in water yield of about 12% over the last 30years. The hydrologic system of the study area is composed of one basic aquifer and a few perched aquifers feeding springs. Their resilience to drought depends on their geological setting: study of some depletion curves helped us to understand the geological setting of the various types, and two promising sites for the habitat preservation of amphibians were identified. Study results indicate new approaches to the study and management of the environment and its water supply, which could be useful in similar areas.

Reliability of water content estimation by profile probe and its effect on slope stability

Shallow landslide failures are distributed worldwide and cause economic losses and fatalities. A proper evaluation of the possible occurrence of shallow landslides requires reliable characterization of water content. Volumetric water content (θ) is commonly estimated using dielectric sensors, which use manufacturers’ calibration curves developed for specific soil types. In this study, we present the experimental results achieved during a laboratory calibration of a capacitance probe (PR2/6 probe), tested on two sandy soils widely outcropping in Central Italy. The proposed equations demonstrate a more reliable estimation of θ with respect to the generalized soil equation provided by the manufacturer, which overestimates θ by up to 10 percentage points. Such overestimation could affect the evaluation of suction stress in partially saturated shallow soils affecting the slope stability analysis. Although the use of θ from correct calibration equations provides less precautionary factor of safety values, a reliable evaluation of the soil moisture condition is fundamental when mapping and predicting the spatial and temporal occurrence of shallow landslides. The use of the PR2/6 probe with the appropriate soil calibration equations in early warning monitoring systems will provide a more reliable forecast, minimizing the number of false alarms.

A contribution to the definition of the ongoing climate change and its impacts on the water resources: the case of Monte Fumaiolo (Central Italy)

Monte Fumaiolo plateau, located at 1407 m a.s.l. in Northern Apennines (Central Italy), has an extension of about 11 km2. Monte Fumaiolo plateau is constituted by a set of sub-horizontal sandstone formations (San Marino and Monte Fumaiolo sandstones), having a medium-high permeability; the plateau rests on top of a low permeability rock sequence. The plateau is a good aquifer, which gives origin to a large number of small springs and to a few large ones. The Tiber River, one of the largest in Italy, originates from Monte Fumaiolo. In spite of the scarcity of hydrometric data, this preliminary paper attempts to evaluate the water budget of the plateau and the impact of the ongoing climatic change. The results so far obtained indicate statistically significant decrease of the rainfall in winter (i.e. during the recharge season) and a strong increase of temperature, due to a linear gradient of +0.44 °C/decade. This caused a decrease of the total water yield of the plateau, which will continue if the detected trends should keep going.

Reliability of GBInSAR Monitoring in Ingelsberg Landslide Area (Bad Hofgastein, Austria)

The present work shows and discusses the GBInSAR measurements for the Ingelsberg area, where one of the most dangerous landslide of Salzburg region is located (Bad Hofgastein – Austria). It is a rockfall developing on an area of about 40000 m2 which is characterized by the outcropping of anti-dip stratified green and calc-mica schists. The GBInSAR monitoring campaign started on March, 2013 (scan time of about 5 minutes): data acquired by the radar instrument were integrated with those from other traditional monitoring systems consisting in 3 cameras placed near the slope and 5 extensometers placed in the landslide Head Area. In order to evaluate the reliability of GBInSAR monitoring, a comparison with displacement data from extensometers was made. During March-December 2013 at least 5 events were observed, the main of which occurred during April-May-June period (3 events), representing a key period for the landslides occurrence in this region. Taking as reference this period, the comparison of the two monitoring techniques showed a good correlation, indicating that the monitoring system of the Ingelsberg landslide is reliable and useful for further analysis, such as the application and checking of the techniques to predict the time to slope failure (TSF).

The Ingelsberg landslide (Bad Hofgastein, Austria): description and first results of monitoring system (GBInSAR technique)

The present work shows the first results of a monitoring campaign performed at the Ingelsberg slope in Bad Hofgastein (Austria). The Groung-Based Interferometric Synthetic Aperture Radar (GBInSAR) was used to create displacement maps, providing information on the location and magnitude of the phenomena studied. These information provide a significant support to decision makers during landslide emergencies, allowing the civil protection authorities to assess the risk and to manage an efficacious emergencies response. In detail, the landslide assessment and the correlation of the GBInSAR data with meteorological data and those obtained by other monitoring instruments are discussed highlighting the open problems related to data acquisition, processing and analysis.

Pumping water wells near large surface water bodies

Estimates of water coming from surface water bodies (stream or lake depletion) are particularly necessary when siting drinking water wells near rivers or lakes with poor quality water. A finite difference model was used to analyze several hydrogeological systems characterized by large surface water bodies (i.e., lakes). A sensitivity analysis of lake width on lake depletion was made. MODFLOW model simulations show that, when lake width is more than about 2000 m, lake depletion becomes independent of its width indicating that rivers behave like lakes when width exceeds 2000 m. After about 600 modelling simulations and a best-fitting procedure a new empirical formula, allowing lake depletion to be estimated, is proposed. It expresses lake depletion as a function of various hydraulic and hydrogeological parameters, such as unit inflow to the lake, lake depth, distance between well and surface water body, filter length of the well, and pumping rate. The new formula can also be applied, with even larger approximations, to the estimation of stream depletion in cases of pumping close to surface water bodies less than 2000 m wide. The formula proposed here should be useful in deciding where to locate a pumping well and the appropriate length of its screen. Key terms: Surface water bodies, Numerical modeling, Stream depletion, Lake depletion