Riviste Online SApienza - R.O.SA - 2 (Sapienza University of Rome)
Not a member yet
1407 research outputs found
Sort by
Contribution to the hydrogeological knowledge of the Cremona aquifer system and to the exploitation of new water resources
Full text linkThis paper gives the results of a series of hydrogeological and hydrochemical investigations carried out on the multilayered aquifer system of Cremona – characterized by a fresh water/salt water inter- face 400-500 meters below ground level – where a new well field is to be built east of town (AEM, 2001). The well field project is being carried out by the Municipal Energy Company of Cremona (AEM) and calls for the abandoning of a number of older wells and the building of ten new wells. Up to now four piezometers and two wells have already been drilled, which pump at different levels from aquifers located at different depths. The pumping tests done at the two wells have provided transmissivity (~10-2 m2/s) and storage coefficient (10-3÷10-5) data for each aquifer horizon. A simplified model of the well field was built, calibrated from the pumping test results. The model was then used to simulate aquifer behavior with the well field completed.The simulation showed that the cones of depression would inter- fere with each other, causing a maximum drawdown of about 4 meters greater than that occurring with only one well in operation, if all the wells exploit only two of the usable aquifer horizons. The hydrochemical analysis revealed the natural presence of ammonia, iron, manganese and arsenic in all the aquifers, confirming the necessity of a water treatment plant. An analysis of both the pumping tests and the simulation results indicate that there is a realistic possibility that the salt/fresh water interface may rise up to the wells, although over a long time period (probably decades). Thus it is advisable that the putting into operation of the well field coincide with further investigations for planning solutions to eliminate the possibility of the rising of this interface
Proposed seismic classification of Italy and related actions
Full text linkThe paper reports the results of a study conducted on the classification of Italian seismic zones. The study investigated seismic clas- sification alternatives, identifying actions to be applied to the design of new structures and to the retrofitting of existing ones for seismic compliance. The findings from the study were compared with the contents of Prime Minister\u27s Decree 3274/03 and with the Consolidated Text of provisions arising from Decree of the President of the Republic no. 380 of 6 June 2001. An ad-hoc seismic hazard estimation, based on the latest data available in the literature, sup- ports the considerations made in the paper. Under the above Regulations, Italian municipalities are grouped into zones belonging to the same "seismic category" and the same spectral shape is used for defining the seismic action of all zones. These choices result into seismic actions that are more severe (or, in some cases, less severe) than the ones representing actual seismicity. To redress this situation, the paper suggests an alternative taking into account the specific seismicity of each municipality, so as to obtain a more homogeneous distribution of hazard levels (and of the related accepted risk) among municipalities. This goal is achieved by replacing the classification based on “seismic zones” with the defini- tion of a “municipality-specific” seismic action. The paper describes an approach to be applied to the hazard spectrum with a view to obtaining a regularised shape of the elastic spectrum. Moreover, as earthquakes have different distribution, frequency and intensity in the various zones of the country, different seismic actions should be defined for the Ultimate Limit State (ULS) and for the Damage Limit State (DLS)
The influence of rock bridges in block fall processes
Full text linkThe detailed study of the detachment surfaces left by rockfalls, together with the 3-D analysis of unstable rock volumes, confirm the fundamental role of intact rock bridges, with different location, that provide an elevated, localised, strength contribution and that are then broken at the moment of the collapse. The back-analysed case histories, carried out assuming a limit equilibrium principle, have ascertained that the limestone rocks involved in rockfalls had mean values of tensile and shear strength ranging from 1.5 to 5 MPa. In the case of overhanging columnar blocks, the stability condition is made possible by the presence of rock bridges with moderate extension (rock bridge area Ap = 400- 3600 cm2, on average) whose size increases for larger blocks and for weaker rock types (τ = 1-2 MPa). These results have been obtained considering the mean strength mobilised by the intact rock bridges, assuming the block weight as the only acting force and neglecting the influence of external forces of different nature (water seepage along the joints, earthquake). According to these assumptions the stability analyses have indicated a very limited extension of the rock bridges (0.2-1.6%) with respect to the whole area of the contact surfaces between block and stable rock mass. Rockfalls involving blocks with base sliding show very poor evidences of rock bridges, which are often very small (length = 10-30 cm) and irregularly distributed over the detachment surface
Use of electromagnetic, geoelectric and seismic tomography refraction geophysical methods to estimate the water content in the subsoil
Full text linkThe interpretation of combined geophysical methods [Ground Penetrating Radar (GPR), Electrical Resistivity Tomography (ERT) and Seismic Refraction Tomography (SRT)] are proposed to assess the physical properties characterizing the near surface porous formations, and in particular way the volumetric water content. The search was carried out in semi-controlled situations. The variations of several geophysical parameters (the electromagnetic (EM) wave velocity, the seismic wave velocity and the electrical resistivity) were considered in the subsoil to estimate the fluctuations of the volumetric water content in the same subsoil. Is, in fact, known that the values of the geophysical parameters, that can be obtained from measures in surface, are influenced by the presence of water in the pore and in the fractures of the materials in the subsoil. The esteem of the variations of these parameters can be makes by measures repeated in the time (i.e. measures realized before and after water’s immission in the subsoil). This type of monitoring can allow the individualization of the principal paths of outflow of the water in the subsoil. The study conducted in this paper point out as the use of combined geophysical methods providing models of water outflow from the surface down to some meter deep
Pumping response of volcanic aquifers: examples from the volcanic areas of Naples and Viterbo
Full text linkDetermining the sustainable well yield in heterogeneous aquifers is an arduous task, because of the variability of the time-drawdown relation. The present work deals with the pumping response of wells that penetrate in the volcanic rocks of Naples and Viterbo; in these areas the average aquifer yield is lower than 10 l/s per km2. Four wells have been tested at a constant discharge: P1, 20 m deep, penetrates a leaky aquifer in pyroclastic soils and Neapolitan Yellow Tuff and has been tested at 2.5 l/s for 3200 min; P2, 70 m deep, penetrates a perched aquifer in Peperino (a quartz-latitic ignimbrite) and has been tested at 0.3 l/s for 30 min; P3, 170 m deep, penetrates an unconfined aquifer in Peperino and has been tested at 0.9 l/s for 90 min; P4, initially 250 then 290 m deep, penetrates an unconfined aquifer in lavas and tuffs of Vico vulcano and has been tested at 25 l/s for 1410 min and 15 l/s for 1620 min. Drawdown has been measured during the pumping and residual drawdown during the recovery in the same pumped well. For all wells, the relation time-drawdown has a similar trend both during pumping and recovery without reaching the steady-state. A faster drawdown is instead observed during the pumping period. Transmissivity values, calculated with recovery data, ranges from 7.21 x 10-5 to 1.47 x 10-3 m2/s and are higher than those estimated through pumping data. Results were interpreted according to the heterogeneity of the aquifer, dual porosity of tuffs, well-loss, and aquifer recharge. These results highlighted a first hydraulic characterization of volcanic rocks and, at the same time, led to some suggestions for the determination of the sustainable well yield