Prediction of Dielectric Breakdown of OHTL Insulators Using Contact Angle Measurements

Porcelain insulators used in overhead transmission lines (OHTL) are exposed to pollution when operational. To observe the effect of external pollution on these insulators, the relationship between the flashover voltage and surface contamination was studied. The flashover voltage drops sharply when contaminants in the wind are deposited on the surface of the insulators in a humid environment. Under wet conditions, the flashover voltage demonstrates a difference of approximately 10 kV depending on the contamination levels. The higher the equivalent salt deposit density, the lower the contact angle. In particular, the flashover voltage under wet conditions decreases exponentially when the contact angle is below 30°. In this case, the condensation area becomes considerably wider, thus exhibiting the difference in the area of the electrolytic conductive film layer forming the leakage path on the surface. Depending on the equivalent salt deposit density and contact angle, the area of condensation is more than doubled. To measure the level of contamination on the surface using this principle, a contact angle measurement method was adopted to predict the dielectric breakdown of the insulator.

Improving the Stability of the Directional Room G 31-33, Horizon 210 - East, Ocnele Mari-Coceneṣti Salt Mine, By Reinforcement with Anchors and Shotcrete

The rock salt deposit from Ocnele Mari - Coceneşti was mined by the method with rooms and small square pillars, at the levels + 226m and + 210m. Although the saline is not deep, certain instability phenomena (cracks, exfoliations) have occurred in the resistance structures (pillars, ceilings), especially in the G31-33 directional room, horizon 210E. These instability phenomena were also highlighted following the 3D finite element numerical modelling. In order to prevent the degradation of the mining excavations and the resistance structures, the affected surfaces were supported with anchors and reinforced shotcrete. The ceiling of the consolidated section of the G31-33 directional room, horizon 210E is monitored by the systematic measurement, on topographic landmarks mounted on the ceiling, of the vertical and horizontal displacements.

Allocation of a deep-lying brine aquifer in the rocks of a chemogenic section based on the data of geophysical well logging and 2D seismic exploration

Advancement in the production of potassium fertilizers is an important strategic task of Russian agricultural industry. Given annually growing production rates, the reserves of discovered potassium-magnesium salt deposits are noticeably decreasing, which creates the need to ensure stable replenishment of the resource base through both the discovery of new deposits and the exploitation of deep-lying production horizons of the deposits that are already under development. In most cases, deposits of potassium-magnesium salts are developed by underground mining. The main problem for any salt deposit is water. Dry salt workings do not require any additional reinforcement and can easily withstand rock pressure, but with an inflow of water they begin to collapse intensively – hence, special attention is paid to mine waterproofing. Determination of spatial location, physical and mechanical properties of the aquifer and water-blocking stratum in the geological section represent an important stage in the exploration of a salt deposit. The results of these studies allow to validate an optimal system of deposit development that will minimize environmental and economic risks. On the territory of Russia, there is a deposit of potassium-magnesium salts with a unique geological structure – its production horizon lies at a considerable depth and is capped by a regional aquifer, which imposes significant limitations on the development process. To estimate parameters of the studied object, we analyzed the data from CDP seismic reflection survey and a suite of methods of radioactive and acoustic well logging, supplemented with high-frequency induction logging isoparametric sounding (VIKIZ) data. As a result of performed analysis, we identified location of the water-bearing stratum, estimated average thickness of the aquifers and possible water-blocking strata. Based on research results, we proposed methods for increasing operational reliability of the main shaft in the designed mine that will minimize the risks of water breakthrough into the mine shaft.

SALT PROCESSING AT THE NAKHICHEVAN SALT DEPOSIT

One of the topical issues is the study of the formation conditions, geological structure, chemical composition and methods of development of the "Duzdag" salt deposit, formed in the Babek region of the Nakhchivan depression on the territory of Azerbaijan, in order to meet the salt needs of the population. The field is divided into two sections: southern - Nakhchivan and Sust, located 4.5 km north-west of it. The physical and mechanical properties of both sections are close to each other. Losses are allowed during field development due to the fact that salt layers alternate with clay layers. The constantly growing demand for salt has predetermined the need to develop more advanced and progressive production methods based on the mechanization of technological processes, the use of new technologies and world experience. Depending on the formation of salt deposits, different methods of salt extraction are used in world practice. The main method of production of table salt in the world should be its extraction in the form of a solution and evaporation in the sun. The share of each of these methods is about 35%, and about 30% of the salt is extracted from an underground mine. The productive layer of the Nakhchivan rock salt deposit is 93-95% halite and is of high quality. The excess content of clay minerals in the field forces them to be used only in animal husbandry. Frosts drilled in the Nakhchivan rock salt deposit can be widely used in the treatment of liver diseases. The mountain has 130 million tons of natural salt reserves that are effective in treating respiratory ailments. Since the ice is horizontal, patients adapt to the underground part. To open new production facilities and treatment facilities in Duzdag, it is necessary to continue the installation of equipment that meets modern standards, the introduction of mines into a fully automated, controlled technological regime, equipped with a modern ventilation system. Keywords: Nakhchivan salt deposit, processing methods, salt beds.

Spatial Structure and Chronological Development of the Prehistoric Salt-production Complex of Provadia-Solnitsata

The prehistoric complex of Provadia-Solnitsata is located close to the modern-day town of Provadia in Northeastern Bulgaria. The remains represent the oldest salt-production site in Europe (5600 – 4350 BC) from which emerged the earliest prehistoric urban settlement on the continent (4700 – 4350 BC). The complex occupies an area of approximately 30 hectares. The emergence and development of the site were closely related to the largest and in fact the only rocksalt deposit in the Eastern Balkans, the so-called Mirovo salt deposit on which the settlement sits. Salt production on the site was based on the brine (thick saline water) that flowed out of this salt deposit. Brine boiling in ceramic pots at Provadia-Solnitsata is the earliest example on record in Europe for the use of this technology in salt production. It was practiced on this site for longer than one millennium. The heat needed for the process was generated in advance in a special installation or alternatively, was directly provided by an open fire, in both cases by burning firewood. At the end of the Chalcolithic, a change of technology had to be introduced – the water from the brine was then evaporated in a large ‘basin’ by using heat from solar radiation. The development of the five parts of the complex is presented: the tell with deposits from the Late Neolithic and the Chalcolithic, a cemetery from the Early Bronze Age, a Thracian ‘ruler’s residence’ from the 2nd – 1st centuries BC and a very large tumulus on top; a salt-production center from the Late Neolithic and the Chalcolithic together with ritual facilities from that time; a Late Neolithic pit sanctuary and a cemetery from the Middle Chalcolithic over it; a pit sanctuary from the Late Chalcolithic; a cemetery from the Late Chalcolithic.

Generalizing the results of fracture zones study in the Upper Kama potassium salt deposit with the help of gravity study

Introduction. The history of the Upper Kama potassium salt deposit (VKMKS) exploration and operation should be divided into two periods. The first period lasted from 1929, the start of exploitation, until 1986, when the water-protective barrier collapsed and the largest VKMKS mine, the 3rd Berezniki mine, was flooded. The second period began in 1986 and continues to the present day. The first period is characterized by a low level of technogenic load on the geological environment, significantly less than its long-term strength. After 60 years of VKMKS large-scale exploitation, the technogenic load on the geologic environment has increased significantly. As a result, its equilibrium state was upset, giving rise to destruction, accompanied by various dynamic events: caves-in, surface collapses, rockbursts, and tectonic rockbursts. VKMKS structural-tectonic profile study revealed that active faults, nodal structures, and fracture zones have a decisive effect on the geologic environment equilibrium state. Research methodology. When structural and tectonic elements are formed in the supra-salt, salt, and subsalt strata of the deposit, the geologic environment density characteristic changes naturally leading to the development of local density inhomogeneities within. It is possible to locate these inhomogeneities and establish their relationship with structural and tectonic elements of the geological environment, particularly, fractured zones, only by studying the gravity field of the deposit. For this purpose, an areawide, detailed, and high-precision gravimetric survey was performed at a scale of 1:25,000, the results of which were used to identify and study the fracture zones. Research results. Based on the results of gravity field anomalies interpretation on the territory of VKMKS, the horizontal position and size of about 200 local negative linear anomalies of the near northsouth, north-east, and north-west orientations were determined, the sources of which were confidently identified with the fracture zones. Conclusions. The experience of studying the structural and tectonic structure of VKMKS has shown that currently for the deposit’s physical and geological conditions, the detailed, high-precision aerial gravity study is the most effective geophysical method for fracture zones mapping

Construction and operation of batching plants in difficult geological conditions of Upper Kama potash mines

Scenarios of the component arrangement of batching plants in the system of a vertical mine shaft are discussed. The features of operation of batching plants in vertical shafts of potash mines are identified. The actual recorded damages generated in the lining of batching plants in the course of their longterm operation in potash mines are described. The geomechanical researches aimed to determine vertical convergence in batching rooms of mine shafts, as well as for monitoring of crack opening and displacements in sidewalls in the batching chambers are presented. The major results of the full-scale geomechanical observations are reported, and the main causes of fractures in concrete and reinforced concrete lining at junctures of shafts and batching rooms and shaft bins are identified. The set of the engineering solutions implemented for the protection of lining in batching facilities during construction of mine shafts is described, and its efficiency is evaluated. The mathematical modeling is carried out to estimate various negative impacts on deformation and fracture of concrete lining in shafts with regard to the time factor. From the modeling results, the dominant cause of concrete lining damage in batching chambers and in mine shaft is found. Based on the accomplished research results and actual long-term experience of operation of mine shafts, the most favorable factors are determined for the best design choices in construction and long-term maintenance-free operation of batching plants in potash mines of the Upper Kama Potash–Magnesium Salt Deposit.