The Experts below are selected from a list of 27942 Experts worldwide ranked by ideXlab platform
A. Shakas - One of the best experts on this subject based on the ideXlab platform.
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The Buried caldera boundary of the Vesuvius 1631 eruption revealed by present-day soil CO2 concentration
Journal of Volcanology and Geothermal Research, 2019Co-Authors: M. Poret, G. P. Ricciardi, Anthony Finizola, T. Ricci, N. Linde, G. Mauri, S. Barde-cabusson, X. Guichet, L. Baron, A. ShakasAbstract:Volcanic risk at Vesuvius is one of the highest in the world due to the ~670,000 inhabitants living in the Red Zone, the area exposed to both pyroclastic flows and tephra fallout, to be evacuated before renewal of any eruptive activity. The national emergency plan for Vesuvius builds its risk zonation on a scenario similar to the last sub-Plinian eruption, which occurred in 1631. This study aims at providing new insights on the geometry of the caldera associated with this historical eruption. The impact of past Vesuvius eruptions on present-day soil CO2 concentration has been investigated by means of an extended geochemical survey carried out for identifying the circulation pathways of hydrothermal fluids inside the volcano. We performed 4018 soil CO2 concentration measurements over the whole Somma-Vesuvius volcanic complex, covering an area of 50 km2. Besides relatively low values, the results show a significant spatial CO2 concentration heterogeneity over Somma-Vesuvius ranging from the atmospheric value (~400 ppm) up to ~24,140 ppm. The summit of Vesuvius shows an area with anomalous CO2 concentrations well matching the crater rim of the 1906 eruption. Along the cone flanks, secondary CO2 anomalies highlight a roughly circular preferential pathway detected along 8 radial profiles at distances between ~840 m and ~1150 m from the bottom of the present-day crater resulting from the last eruption in 1944. In depth review of the available literature highlights an agreement between this circle-like shaped anomaly and the 1631 sub-Plinian eruption caldera boundary. Indeed, based on the historical chronicles the depression produced by the 1631 eruption had a diameter of 1686 m, whereas the CO2 circular anomaly indicates a diameter of 1956 m. Finally, the results were compared with a 3-D density model obtained from a recent gravity survey that corroborates both the literature and the CO2 data in terms of potential Buried Structure at the base of the Vesuvius cone.
Mohamed A Meguid - One of the best experts on this subject based on the ideXlab platform.
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investigation of soil geosynthetic Structure interaction associated with induced trench installation
Geotextiles and Geomembranes, 2017Co-Authors: Mohamed A Meguid, M. G. Hussein, M R Ahmed, Z Omeman, J WhalenAbstract:Abstract The design of subsurface Structures associated with transportation and other underground facilities, such as Buried pipes and culverts, requires an understanding of soil-Structure interaction. Earth loads on these Structures are known to be dependent on the installation conditions. To reduce earth pressures acting on Buried Structures installed under high embankments, the induced trench method has been recommended and applied in practice for several decades. It involves the installation of a compressible material (e.g. EPS geofoam blocks) immediately above the Buried Structure to mobilize shear strength in the backfill material. A first step towards understanding this complex soil-geosynthetic-Structure interaction and accurately modeling the load transfer mechanism is choosing a suitable material model for the geofoam that is capable of simulating compressive testing results. In this study, an experimental investigation is conducted to measure the changes in contact pressure on the walls of a rigid Structure Buried in granular backfill with an overlying geofoam layer. Validated using the experimental results, finite element analysis is then performed and used to study the role of geofoam density, thickness and location on the load transferred to the Buried Structure. Conclusions are made regarding the effect of modeling EPS inclusion as a non-linear material and the role of EPS configuration on the earth pressure distribution around the Buried Structure.
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on the role of geogrid reinforcement in reducing earth pressure on Buried pipes experimental and numerical investigations
Soils and Foundations, 2015Co-Authors: M R Ahmed, Viet D H Tran, Mohamed A MeguidAbstract:Abstract Understanding the distribution of earth pressure on Buried Structures is essential for the analysis and design of pipes, tunnels and vertical shafts. This paper presents the results of an experimental investigation that has been conducted to measure the distribution of contact pressure on rigid pipes using tactile sensing technology. The method allows for a continuous pressure profile to be measured around the pipes using flexible sheets that can follow the cylindrical shape of the pipes. The physical model involves a Buried pipe installed in granular material subjected to strip surface loading. The effect of introducing a geogrid reinforcement layer above the pipe on the distribution of contact pressure is also examined. To further study the distribution of pressure on the Buried Structure and the soil-geogrid interaction, numerical analyses are performed using a multi-scale finite-discrete element framework that allows for both the explicit modeling of soil particles using discrete elements and the modeling of the embedded Structure using finite elements. The numerical framework is first validated using the experimental results and then used to investigate the detailed behavior of the soil-pipe system.
M. Poret - One of the best experts on this subject based on the ideXlab platform.
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The Buried caldera boundary of the Vesuvius 1631 eruption revealed by present-day soil CO2 concentration
Journal of Volcanology and Geothermal Research, 2019Co-Authors: M. Poret, G. P. Ricciardi, Anthony Finizola, T. Ricci, N. Linde, G. Mauri, S. Barde-cabusson, X. Guichet, L. Baron, A. ShakasAbstract:Volcanic risk at Vesuvius is one of the highest in the world due to the ~670,000 inhabitants living in the Red Zone, the area exposed to both pyroclastic flows and tephra fallout, to be evacuated before renewal of any eruptive activity. The national emergency plan for Vesuvius builds its risk zonation on a scenario similar to the last sub-Plinian eruption, which occurred in 1631. This study aims at providing new insights on the geometry of the caldera associated with this historical eruption. The impact of past Vesuvius eruptions on present-day soil CO2 concentration has been investigated by means of an extended geochemical survey carried out for identifying the circulation pathways of hydrothermal fluids inside the volcano. We performed 4018 soil CO2 concentration measurements over the whole Somma-Vesuvius volcanic complex, covering an area of 50 km2. Besides relatively low values, the results show a significant spatial CO2 concentration heterogeneity over Somma-Vesuvius ranging from the atmospheric value (~400 ppm) up to ~24,140 ppm. The summit of Vesuvius shows an area with anomalous CO2 concentrations well matching the crater rim of the 1906 eruption. Along the cone flanks, secondary CO2 anomalies highlight a roughly circular preferential pathway detected along 8 radial profiles at distances between ~840 m and ~1150 m from the bottom of the present-day crater resulting from the last eruption in 1944. In depth review of the available literature highlights an agreement between this circle-like shaped anomaly and the 1631 sub-Plinian eruption caldera boundary. Indeed, based on the historical chronicles the depression produced by the 1631 eruption had a diameter of 1686 m, whereas the CO2 circular anomaly indicates a diameter of 1956 m. Finally, the results were compared with a 3-D density model obtained from a recent gravity survey that corroborates both the literature and the CO2 data in terms of potential Buried Structure at the base of the Vesuvius cone.
Wenjun Luo - One of the best experts on this subject based on the ideXlab platform.
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new understandings of the seismic modes of high productivity wells in the sinian dengying fm gas reservoirs in the gaoshiti area sichuan basin
Natural Gas Industry B, 2018Co-Authors: Fusen Xiao, Kang Chen, Qi Ran, Xuan Zhang, Bing Xie, Xinggang Liu, Wenjun LuoAbstract:Abstract The Sinian Dengying Fm in the Sichuan Basin is a set of fractured-vuggy reservoirs mainly dominated by sedimentation and karstification, and characterized by small fractures and vugs, complex stratigraphy and lithology, and strong vertical and lateral reservoir heterogeneity. As a result, the drilling rates are lower and single-well gas productivity varies greatly there. And the reservoir identification results based on seismic data in this area are ambiguous. In view of this, the Deng 4 Member in the Gaoshiti Buried Structure on the southern flank of the Leshan–Longnusi palaeohigh was precisely divided in stratigraphy. Then, the types of reservoir assemblages were determined based on gas well logging and test data, and the seismic response characteristics of typical wells with different types of reservoir assemblages and the seismic modes of high productivity wells were studied by using high-resolution seismic data. It is indicated that the Deng 4 Member in this area is divided into three types of reservoir assemblages, which correspond to three seismic modes. Seismic mode I: It presents the seismic response characteristics of “wide wave troughs + double highlights” or “wide wave troughs + complex waves”, indicating that fractures and vugs are developed. It is the preferred seismic mode of high productivity wells in the stage of development. In this mode, the technology of highly deviated wells or horizontal wells can be implemented. Seismic mode II: It presents the seismic response characteristics of “wide wave troughs”, indicating that fractures and vugs are relatively developed. It is the mode of moderate productivity wells. In this mode, the technology of highly deviated wells can be implemented. Seismic mode III: It presents the seismic response characteristics of “wide wave troughs + highlights”, indicating that fractures and vugs are underdeveloped. It is mode of low productivity wells, in which the technology of horizontal wells can be implemented. The new understandings on seismic modes were applied on site. It is shown that the reservoir drilling rate is over 60% and the average gas production rate during the production test of 8 wells is up to 75.34 × 104 m3/d. It is concluded that the seismic mode of high productivity wells based on seismic facies, fracture and vug prediction and integrated target design provides a support for the well arrangement and drilling trajectory adjustment in natural gas exploration and development in the Gaoshiti area and good results have been achieved.
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New understandings of the seismic modes of high productivity wells in the Sinian Dengying Fm gas reservoirs in the Gaoshiti area, Sichuan Basin
'Elsevier BV', 2018Co-Authors: Fusen Xiao, Kang Chen, Qi Ran, Xuan Zhang, Bing Xie, Xinggang Liu, Wenjun LuoAbstract:The Sinian Dengying Fm in the Sichuan Basin is a set of fractured-vuggy reservoirs mainly dominated by sedimentation and karstification, and characterized by small fractures and vugs, complex stratigraphy and lithology, and strong vertical and lateral reservoir heterogeneity. As a result, the drilling rates are lower and single-well gas productivity varies greatly there. And the reservoir identification results based on seismic data in this area are ambiguous. In view of this, the Deng 4 Member in the Gaoshiti Buried Structure on the southern flank of the Leshan–Longnüsi palaeohigh was precisely divided in stratigraphy. Then, the types of reservoir assemblages were determined based on gas well logging and test data, and the seismic response characteristics of typical wells with different types of reservoir assemblages and the seismic modes of high productivity wells were studied by using high-resolution seismic data. It is indicated that the Deng 4 Member in this area is divided into three types of reservoir assemblages, which correspond to three seismic modes. Seismic mode I: It presents the seismic response characteristics of “wide wave troughs + double highlights” or “wide wave troughs + complex waves”, indicating that fractures and vugs are developed. It is the preferred seismic mode of high productivity wells in the stage of development. In this mode, the technology of highly deviated wells or horizontal wells can be implemented. Seismic mode II: It presents the seismic response characteristics of “wide wave troughs”, indicating that fractures and vugs are relatively developed. It is the mode of moderate productivity wells. In this mode, the technology of highly deviated wells can be implemented. Seismic mode III: It presents the seismic response characteristics of “wide wave troughs + highlights”, indicating that fractures and vugs are underdeveloped. It is mode of low productivity wells, in which the technology of horizontal wells can be implemented. The new understandings on seismic modes were applied on site. It is shown that the reservoir drilling rate is over 60% and the average gas production rate during the production test of 8 wells is up to 75.34 × 104 m3/d. It is concluded that the seismic mode of high productivity wells based on seismic facies, fracture and vug prediction and integrated target design provides a support for the well arrangement and drilling trajectory adjustment in natural gas exploration and development in the Gaoshiti area and good results have been achieved. Keywords: Sichuan Basin, Gaoshiti area, Sinian, Dengying Formation, Karst, Fractured-vuggy reservoir, Seismic response, Seismic mode of high productivity well, Fracture and vug predictio
G. Natale - One of the best experts on this subject based on the ideXlab platform.
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The volcanic and geothermally active Campi Flegrei caldera: an integrated multidisciplinary image of its Buried Structure
International Journal of Earth Sciences, 2014Co-Authors: M. Piochi, C. R. J. Kilburn, M. A. Vito, A. Mormone, A. Tramelli, C. Troise, G. NataleAbstract:The Campi Flegrei caldera in southern Italy is one of the greatest geohazard areas on Earth. Evidence of an active magmatic and geothermal system is provided by ongoing ground uplift, with volcano-tectonic and long-period (LP) seismicity, the persistent degassing of ~1500 tonnes of CO_2 per day, the presence of hot fumaroles at temperatures of 90–150 °C, brine-rich aquifers (with total dissolved solids up to 33 g l^−1) and high thermal gradients in the crust (with temperatures reaching 420 °C at 3,050 m b.s.l.). Since the 1940s, more than 100 exploratory boreholes have been drilled in the area to depths of 80–3,100 m by the Azienda Geologica Italiana Petroli (AGIP) and the Società Anonima Forze Endogene Napoletane (SAFEN). To date, however, no systematic reanalysis of the drilling data has been carried out, and the Buried volcanic Structure has not been updated using the most recent scientific results and previous findings. By integrating unpublished data from the AGIP and SAFEN reports with published information from geological, volcanological, petrological, petrophysical and geophysical studies, this paper presents an improved picture of the Campi Flegrei caldera that will be useful for volcanic hazard assessment and mitigation in the Naples area and for future research planning. The results suggest that intra-caldera activity has been influenced by how the magmatic system at depths greater than about 4 km has determined the transfer of magma, volatiles, and heat to the overlying geothermal system and, ultimately, to the surface. In particular, intriguing is that the most volcanically active central-eastern sector of the caldera, which is subject to intense bradyseismic ground movement and gas emission, coincides with a structurally delimited subsurface rock volume characterized by an uprising of the 100 °C isotherm, a deep water supply to the shallower aquifer, the early disappearance of secondary calcite, LP seismicity and high seismic S-wave attenuation. In this area, we also document evidence of repeated injection at depths of c. 1.5–3.0 km of isolated and small-volume batches of magma, where occurred their crystallization and degassing. Shallow intrusions and degassing of magma are thus identified as two of the key processes that drive unrest in Campi Flegrei.
