An eighteenth century tunnel as possible archive for palaeoclimate studies

The former Silva Lake (present “Pian del Lago”, Siena, Italy) developed during late Quaternary and formed as a poljie on the Triassic limestones. The depression, nowadays completely drained, is N-S oriented, 4.5 km wide and 12 km long. The lake never exceeded 6 m in depth, and it was mainly a grassy swamp during the dry season. The lake depression is filled with 20 to 30 m of a reddish siltyclayey succession. Starting from the Middle Age till late 18th century, the shallow waters of the lake and the humid area around acted as a swampy area infested by malaria. In 1766 a Sienese nobleman, Francesco Bindi Sergardi drained the lake excavating a drainage 2124m-long tunnel in Triassic limestones to connect the Silva Lake with the closeby Rigo Creek. However, quite often the tunnel was filled with debris and the lake swamped up again. In 1780 Pietro Leopoldo Grand Duke of Tuscany definitively reclaimed the Silva Lake and completed the construction of the drainage tunnel by paving and extending it for an additional 197 m. Since then, the tunnel is called the ”Canale del Gran Duca”. The entrance altitude of the canal is at 252 m a.s.l., and the exit is at 247 m a.s.l. The altitude difference is therefore of 5 m, and the canal floor has a slope of 0.2 %. The canal is for the most part paved but, in places, solid walls of Triassic limestone are still visible. Diffuse karst features are forming locally. Stalactites have lengths varying from 5 to 10 cm, and flowstones occur along the tunnel walls. The presence of these speleothems has allowed geochemical investigations to establish climatic variations of the last two centuries. The tunnel was probably cleaned and well maintained for sometime after its construction (1780), and it is likely that all the remaining speleothems have developed in the last two centuries with an estimated growth of a 0.5/6 mm per year. A petrographic investigation of a well laminated flowstone with a parasitic stalagmite has been undertaken to determine the growth mechanisms. Oxygen and carbon isotope data (δ18O and δ13C values) were used as indirect proxies for palaeoenvironmental reconstructions. Preliminary, data show significant variations along the axis of the flowstone possibly related to environmental and climatic variations within and above the “canale”

Radioactive elements in the environment

Indicated role of natural radioactive elements (U, Th) in geospherical layers and various environmental components is discussed. Induced radionuclide problems are examine

An eighteenth century tunnel as possibile archivi for paleoclimate studies

The former Silva Lake (present “Pian del Lago”, Siena, Italy) developed during late Quaternary and formed as a poljie on the Triassic limestones. The depression, nowadays completely drained, is N-S oriented, 4.5 km wide and 12 km long. The lake never exceeded 6 m in depth, and it was mainly a grassy swamp during the dry season. The lake depression is filled with 20 to 30 m of a reddish siltyclayey succession. Starting from the Middle Age till late 18th century, the shallow waters of the lake and the humid area around acted as a swampy area infested by malaria. In 1766 a Sienese nobleman, Francesco Bindi Sergardi drained the lake excavating a drainage 2124m-long tunnel in Triassic limestones to connect the Silva Lake with the closeby Rigo Creek. However, quite often the tunnel was filled with debris and the lake swamped up again. In 1780 Pietro Leopoldo Grand Duke of Tuscany definitively reclaimed the Silva Lake and completed the construction of the drainage tunnel by paving and extending it for an additional 197 m. Since then, the tunnel is called the ”Canale del Gran Duca”. The entrance altitude of the canal is at 252 m a.s.l., and the exit is at 247 m a.s.l. The altitude difference is therefore of 5 m, and the canal floor has a slope of 0.2 %. The canal is for the most part paved but, in places, solid walls of Triassic limestone are still visible. Diffuse karst features are forming locally. Stalactites have lengths varying from 5 to 10 cm, and flowstones occur along the tunnel walls. The presence of these speleothems has allowed geochemical investigations to establish climatic variations of the last two centuries. The tunnel was probably cleaned and well maintained for sometime after its construction (1780), and it is likely that all the remaining speleothems have developed in the last two centuries with an estimated growth of a 0.5/6 mm per year. A petrographic investigation of a well laminated flowstone with a parasitic stalagmite has been undertaken to determine the growth mechanisms. Oxygen and carbon isotope data (d18O and d13C values) were used as indirect proxies for palaeoenvironmental reconstructions. Preliminary, data show significant variations along the axis of the flowstone possibly related to environmental and climatic variations within and above the “canale”

ИССЛЕДОВАНИЕ ХАРАКТЕРА МЕХАНИЧЕСКОГО ВЗАИМОДЕЙСТВИЯ РАБОЧИХ ПОВЕРХНОСТЕЙ СИЛЬНОТОЧНЫХ РАЗРЫВНЫХ КОНТАКТОВ

Introduction. The nature of the interaction of high-working surfaces of the electrical contact uniquely affects their performance. By the failure of the contacts in the main drive processes resulting from complex destructive factors affecting their performance. However, not all processes are studied in detail and give in modeling. The purpose of the paper is to show the possibility of using the method of holographic interferometry to estimate the plastic deformation in the zone of contact interaction. One of the significant factors affecting the work of the contact pair is the compressive force of the contact surfaces. Compression discontinuous contact is directly connected with the processes of elastic and plastic deformation of the contact material, which is particularly evident in the contact details of the powder or composite materials. The paper focuses on the plastic deformation of the surface layers of discontinuous contact in circuit, it is believed that it is directly related to the mechanism of conductivity of contacts. As shown, a significant effect on the deformation of the contact surfaces and renders the working environment, in particular transformer oil. Methodology. Assessing the impact of compression forces on the deformation of the contact surface was conducted experimentally using the method of holographic interferometry. Results. Experimental studies, which indicated that the compact and powder materials plastic deformation in and around the area microcontacts simplistically stated that requires experimental verification. A method for evaluating the state of stress, which affects the formation and destruction of the local contact spots. Practical value. Using the experimental method of determining the movement of the contact region allows you to optimize discontinuous contacts from composite and powder materials.Характер взаимодействие рабочих поверхностей сильноточных электрических контактов однозначно влияют на их работоспособность. К отказу в работе контактов в основном приводят процессы, возникающие в результате комплекса факторов деструктивно влияющих на их работоспособность. При этом не все процессы подробно изучены и поддаются моделированию. Одним из существенных факторов, влияющим на работу контактной пары, служит усилие сжатия контактных поверхностей. Сжатие разрывных контактов напрямую связано с процессами упругой и пластической деформации контактных материалов, что особенно наглядно проявляются на контакт-деталях из порошковых или композиционных материалов. В статье основное внимание уделяется пластической деформации поверхностных слоев разрывных контактов в процессе замыкания, поскольку считается, что она напрямую связана с механизмом проводимостью контактов. Как показано, существенное влияние на деформацию контактных поверхностей оказывает и рабочая среда, в частности трансформаторное масло. Оценка влияния усилия сжатия на деформацию контактной поверхности проводилась экспериментально с использованием метода голографической интерферометрии. Приведены результаты исследования, в которых указывалось, что для компактных и порошковых материалов пластическая деформация внутри и вокруг зоны микроконтактов указывается упрощенно, что требует экспериментального уточнения.Характер взаємодії робочих поверхонь сильнострумних електричних контактів однозначно впливає на їх працездатність. До відмови в роботі контактів в основному приводять процеси, що виникають в результаті комплексу факторів деструктивно впливаючи на їх працездатність. При цьому не всі процеси докладно вивчені і піддаються моделюванню. Одним з істотних чинників, що впливає на роботу контактної пари, служить зусилля стискання контактних поверхонь. Стискання розривних контактів прямо пов'язане з процесами пружної і пластичної деформації контактних матеріалів, що наочно виявляються на контакт-деталях з порошкових або композиційних матеріалів. У статті основна увага приділяється пластичній деформації поверхневих шарів розривних контактів у процесі замикання, оскільки вважається, що вона прямо пов'язана з механізмом провідності контактів. Як показано, істотний вплив на деформацію контактних поверхонь має і робоче середовище, зокрема трансформаторне масло. Оцінка впливу зусилля стиснення на деформацію контактної поверхні проводилася експериментально з використанням методу голографічної інтерферометрії. Наведено результати експериментальних досліджень, в яких вказується, що для компактних і порошкових матеріалах пластична деформація всередині і навколо зони мікроконтактів наводиться спрощено, що вимагає експериментального уточнення

Stratigraphic evidence for a “pluvial phase” between ca 8200–7100 ka from Renella cave (Central Italy)

A stratigraphic and chronological study of the upper level of Renella Cave (Apuan Alps, Central Italy) reveals that two episodes of flowstone accumulation bracket a thick clastic layer deposited between ca 8.2 and 7.1 ka. This layer, which represents a period of enhanced cave flooding, is substantially in phase with an interval of depleted oxygen isotope values previously recorded in a stalagmite from nearby Corchia Cave, interpreted to have resulted from an increase in local precipitation. These data confirm that during this period of time the region experienced relatively wetter conditions, including an increase in high-magnitude events capable of invading the higher passages of Renella Cave. The timing of the clastic phase occurred when the Eastern Mediterranean experienced deposition of sapropel layer S1, which is thought to reflect the stagnation of sea water produced largely by enhanced flood activity along the Nile in response to increased monsoon intensity in northern equatorial Africa. Recent estimates suggest that S1 may have lasted from ca 10.8 to ca 6.1 ka cal BP. Combined evidence from Renella and Corchia Cave indicates that the period corresponding to the wettest phase in the Apuan Alps was much shorter than this, and suggests that there is no straightforward connection between increased advection of water vapour from the Atlantic between 8.2 and 7.1 ka, as recorded in the Corchia and Renella records, and monsoon-driven enhancement of Nile discharge and S1 deposition in the eastern Mediterranean

Stratigraphic evidence for a “pluvial phase” between ca. 8200-7100 ka from Renella Cave (Central Italy)

A stratigraphic and chronological study of the upper level of Renella Cave (Apuan Alps, Central Italy) reveals that two episodes of flowstone accumulation bracket a thick clastic layer deposited between ca 8.2 and 7.1 ka. This layer, which represents a period of enhanced cave flooding, is substantially in phase with an interval of depleted oxygen isotope values previously recorded in a stalagmite from nearby Corchia Cave, interpreted to have resulted from an increase in local precipitation. These data confirm that during this period of time the region experienced relatively wetter conditions, including an increase in high-magnitude events capable of invading the higher passages of Renella Cave. The timing of the clastic phase occurred when the Eastern Mediterranean experienced deposition of sapropel layer S1, which is thought to reflect the stagnation of sea water produced largely by enhanced flood activity along the Nile in response to increased monsoon intensity in northern equatorial Africa. Recent estimates suggest that S1 may have lasted from ca 10.8 to ca 6.1 ka cal BP. Combined evidence from Renella and Corchia Cave indicates that the period corresponding to the wettest phase in the Apuan Alps was much shorter than this, and suggests that there is no straightforward connection between increased advection of water vapour from the Atlantic between 8.2 and 7.1 ka, as recorded in the Corchia and Renella records, and monsoon-driven enhancement of Nile discharge and S1 deposition in the eastern Mediterranea

Stratigraphic evidence for a “pluvial phase” between ca 8200–7100 ka from Renella cave (Central Italy)

A stratigraphic and chronological study of the upper level of Renella Cave (Apuan Alps, Central Italy) reveals that two episodes of flowstone accumulation bracket a thick clastic layer deposited between ca 8.2 and 7.1 ka. This layer, which represents a period of enhanced cave flooding, is substantially in phase with an interval of depleted oxygen isotope values previously recorded in a stalagmite from nearby Corchia Cave, interpreted to have resulted from an increase in local precipitation. These data confirm that during this period of time the region experienced relatively wetter conditions, including an increase in high-magnitude events capable of invading the higher passages of Renella Cave. The timing of the clastic phase occurred when the Eastern Mediterranean experienced deposition of sapropel layer S1, which is thought to reflect the stagnation of sea water produced largely by enhanced flood activity along the Nile in response to increased monsoon intensity in northern equatorial Africa. Recent estimates suggest that S1 may have lasted from ca 10.8 to ca 6.1 ka cal BP. Combined evidence from Renella and Corchia Cave indicates that the period corresponding to the wettest phase in the Apuan Alps was much shorter than this, and suggests that there is no straightforward connection between increased advection of water vapour from the Atlantic between 8.2 and 7.1 ka, as recorded in the Corchia and Renella records, and monsoon-driven enhancement of Nile discharge and S1 deposition in the eastern Mediterranean