Mechanics of a tectonized soil slope: influence of boundary conditions and rainfall

The Vadoncello landslide was mobilized in December 1993 and is still active. It involves highly tectonized soils and is the reactivation of a landslide dragged by a larger landslide at the toe of the slope soon after the 1980 Irpinia (Southern Italy) earthquake. Investigations and monitoring of the Vadoncello landslide were carried out, between 1994 and 1996, within an EC funded research project. The slope has been found to be formed of chaotic successions of soil and rock strata which have been grouped into soil complexes. The soil mechanical properties are shown to be very poor, the deep soils being prone to large plastic straining even due to relatively small loading changes. The soil displacements show that a shallow fast rotational sliding has occurred at the top of the slope and a shallow earthflow has developed downslope, both lying above deeper soils involved in a mechanism of slow and long-lasting irrecoverable movements. These slow deep movements are considered to be consequent to the plastic flow of the clayey soils. They can be activated by the effects of seasonal rainfall, of low-medium intensity seismic events and by the effects of the morphological changes resulting from the slow movements themselves. The landslide reactivation in 1993 is seen to have been the combination effect of a low return-period rainfall event and the slow movements active at depth in the slope

Characterisation of the Ionian-Lucanian coastal plain aquifer

This paper deals with a Southern Italy area, 40 km by 10 km wide, located where four river valleys anastomose themselves in the coastal plain. The geological and hydrogeological features of the study area and the chemical-physical groundwater characterisation have been inferred from the data analysis of 1130 boreholes. Some aquifers, connected among them, constituted by soils of different geological origin -marine terraces deposits, river valley alluvial deposits and alluvial and coastal deposits - have been considered. The coastal plain aquifer is the most interesting for practical utilisation. Groundwater flow is mainly unconfined in the marine terraces and in the river valleys while it becomes mostly confined in the coastal plain aquifer. An upper clayey layer overlies the sandy coastal aquifer characterised by a mean hydraulic conductivity value equal to 2.3 10-4 m/s. The bottom is a silty-clayey bed which lies under the sea level. Being the direct natural recharge extremely low, the recharge of this coastal aquifer is mainly guaranteed by the discharge from upward aquifers and from the river leakage. The new acquired knowledge permits to delineate scenarios useful for an optimization of the groundwater resources tapping and for pursuing the safeguard of them

Characterisation of Ionian-Lucanian coastal aquifer and seawater intrusion hazard

e paper deals with the seawater intrusion hazard along the Ionian coastal plain (Southern Italy), between the mouths of Sinni and Bradano Rivers. Subjected to intense agricultural activities, the good-quality of the tapped groundwater is seriously important for the economic growth of this coastal area. The stratigraphical and hydrogeological set-up of the area as the geochemical features of the groundwater arise from the data analysis of 1130 boreholes, widespread over the whole area and from 1.3 up to 423 meters deep. The contribution of seawater intrusion to salinization processes of the studied groundwater system is characterised. As pointed out by chemical-physical data, this phenomenon involves the studied coastal plain for a width of 1-1.5 km on average and it is less evident moving inwards where the altitude of the clayey bottom of the aquifer becomes progressively higher than the sea level. A preliminary seawater hazard map has been carried out through piezometric and aquifer geometrical data

Post-symposium written discussion: Ground movements in highly tectonized soil slopes - The Vadoncello-Serra dell'Acquara landslides

The town of Senerchia (Sele river valley - southern Apennines) lies in a tectonically active area close to the epicentre of the 1980 earthquake (M=6.8). The slope south-cast of the town includes three major landslides, principally in structurally complex formations. The Serra dell' Acquara mudslide involves clays and marls of the Sicilide Unit and is 33 m deep at maximum. The 1980 earthquake remobilized it. Its left flank is bordered upslope by a detrital slab crossed by the crown of the Cimitero landslide, deep seated in the clayey units, which was not remobilized by the earthquake. In 1980 ground movements took place on this side of the slope shortly south of the slab. where more clayey soils outcrop, giving rise to the subsidiary Vadoncello landslide. Since 1980 this slope had not undergone significant deformations until 1993, except for some retrogression of the crown. On 29 December 1993 major movements started. giving rise to a significant extension of the Vadoncello landslide, which is currently still active (Figure 2). The development of this landslide has been under monitoring during I 995 and 1996 (Figure I) as part of a research project founded by the European Community (EEC 1996). Although shallow mudsliding downslope and crown retrogression at the top are the fastest processes on the slope, these are not che leading instability processes. They are related to deeper, although slower, soil deformations, which interact with the other landslide bodies, as briefly discussed in the following

Santa Cesarea coastal thermal springs (southern Italy)

The coastal carbonate Apulian aquifers, located in southern Italy, feed numerous coastal cold springs and constitute the main local source of high quality water. The group of Santa Cesarea springs constitutes the unique occurrence of thermal groundwater outflow, observed in partially submerged coastal caves. The spring water is rich of hydrogen sulfide; temperature ranges from 25 to 33 C°. For their properties, spring waters are used for spa activities from several decades. Hydrogeological spring conceptualisations proposed up now were not able to justify water geochemical peculiarities or were not completely confirmed up now. To reduce these uncertainties, a complex hydrogeological survey has been defined. Geological and structural surveys, chemical and isotopic groundwater analyses, spring and well discharge measurements, well loggings, multi-parameters spring automatized measurements, and cave explorations are ongoing. All available data have been used to improve the knowledge of groundwater flow system, including the valuable deep aquifer, the origin of the thermal waters, and to investigate the possibility of using low-enthalpy geothermal fluids to fulfil the thermal needs of the town of Santa Cesarea Terme

Coastal hydrogeological system of Mar Piccolo (Taranto, Italy)

The Mar Piccolo basin is an internal sea basin located along the Ionian coast (Southern Italy), and it is surrounded primarily by fractured carbonate karstic environment. Because of the karstic features, the main continental water inflow is from groundwater discharge. The Mar Piccolo basin represents a peculiar and sensitive environment and a social emergency because of sea water and sediments pollution. This pollution appears to be caused by the overlapping effects of dangerous anthropogenic activities, including heavy industries and commercial and navy dockyards. The paper aims to define the contribution of subaerial and submarine coastal springs to the hydrological dynamic equilibrium of this internal sea basin. A general approach was defined, including a hydrogeological basin border assessment to detect inflowing springs, detailed geological and hydrogeological conceptualisation, in situ submarine and subaerial spring measurements, and flow numerical modelling. Multiple sources of data were obtained to define a relevant geodatabase, and it contained information on approximately 2,000 wells, located in the study area (1,600 km2). The conceptualisation of the hydrogeological basin, which is 978 km2 wide, was supported by a 3D geological model that interpolated 716 stratigraphic logs. The variability in hydraulic conductivity was determined using hundreds of pumping tests. Five surveys were performed to acquire hydro-geochemical data and spring flow-yield measurements; the isotope groundwater age was assessed and used for model validation. The mean annual volume exchanged by the hydrogeological basin was assessed equal to 106.93 106 m3. The numerical modelling permitted an assessment of the mean monthly yield of each spring outflow (surveyed or not), travel time, and main path flow

Caratterizzazione idrogeologica della piana di Metaponto, qualità e rischi di degrado delle acque sotterranee

The study area falls within the Ionian coastal plain (Southern Italy), bounded on the West by the Sinni River and on the East by Bradano River. It covers 40 km along the coast and 6 km inland. The geological and hydrogeological features of the study area and the chemical-physical groundwater characterisation have been inferred from the data analysis of 1130 boreholes. Some aquifers, connected among them, constituted by soils of different geological origin, exist in the area also if the coastal plain aquifer is the most interesting for practical utilisation. Groundwater flow is mainly unconfined inland, where the aquifer is constituted by terraced deposits and confined in the alluvial coastal plain. An upper clayey layer overlies the sandy coastal aquifer characterised by a mean hydraulic conductivity value equal to 2.3 10-4 m/s. Being the direct natural recharge extremely low, the recharge of this coastal aquifer is mainly guaranteed by the discharge from upward aquifers and from the river leakage. The bottom of the aquifer is a silty-clayey bed which lies under the sea level permitting so the seawater intrusion. This phenomenon involves the studied coastal plain for a width of 1-1.5 km on average and it is less evident moving inwards where the altitude of the clayey bottom of the aquifer becomes progressively higher than the sea level. Other chemical-physical data, studied to determine the quality of the waters, showed that the pollution of the groundwater is considered a grave environmental problem for the studied area

A geo-chemo-mechanical study of a highly polluted marine system (Taranto, Italy) for the enhancement of the conceptual site model

The paper presents the results of the analysis of the geo-chemo-mechanical data gathered through an innovative multidisciplinary investigation campaign in the Mar Piccolo basin, a heavily polluted marine bay aside the town of Taranto (Southern Italy). The basin is part of an area declared at high environmental risk by the Italian government. The cutting-edge approach to the environmental characterization of the site was promoted by the Special Commissioner for urgent measures of reclamation, environmental improvements and redevelopment of Taranto and involved experts from several research fields, who cooperated to gather a new insight into the origin, distribution, mobility and fate of the contaminants within the basin. The investigation campaign was designed to implement advanced research methodologies and testing strategies. Differently from traditional investigation campaigns, aimed solely at the assessment of the contamination state within sediments lying in the top layers, the new campaign provided an interpretation of the geo-chemo-mechanical properties and state of the sediments forming the deposit at the seafloor. The integrated, multidisciplinary and holistic approach, that considered geotechnical engineering, electrical and electronical engineering, geological, sedimentological, mineralogical, hydraulic engineering, hydrological, chemical, geochemical, biological fields, supported a comprehensive understanding of the influence of the contamination on the hydro-mechanical properties of the sediments, which need to be accounted for in the selection and design of the risk mitigation measures. The findings of the research represent the input ingredients of the conceptual model of the site, premise to model the evolutionary contamination scenarios within the basin, of guidance for the environmental risk management. The study testifies the importance of the cooperative approach among researchers of different fields to fulfil the interpretation of complex polluted eco-systems

The degradation hazard of groundwater resources of the Metaponto coastal plain (Southern Italy)

During the last century the land reclamation works, the built-up of dams and modern irrigation systems, the farm and industrial activities, and the overexploitation of the wells, associated to several periods of drought, have deeply modified the quantity and the chemical state of the groundwater resources of the Metaponto coastal plain (Southern Italy). The degradation of the groundwater systems seems to be increased with the time as shown by the piezometric trends (1927-1990) and by the chemical-physical data (1990-2003). The chemical-physical state of the groundwater has been defined according to the hydrochemical classification proposed by an Italian legislative decree