Resistant Rocks Research Articles

Experimental and numerical investigation of the TBM disc cutter wear using a new tunnel boring machine laboratory simulator

One of the essential and practical issues on TBM performance is the wear during the excavation process of abrasive and resistant rock. The wear of the disc cutter, which is caused by the gradual and uniform reduction of the diameter of the disc cutter, is caused by the rock-machine interaction during excavation, and various factors can intensify this phenomenon and reduce the wear life of the disc cutter. To obtain a proper view of the relationship between the operating parameters of the excavation machine and the disc cutter wear, a new laboratory device has been designed and built in the mechanized excavation laboratory of the Sahand University of Technology. By using this device, the amount of wear of cutting tools in excavation machines can be obtained against rough rock samples, and from the results, the amount of wear of cutting tools of excavation machines can be minimized so that the efficiency of the excavation machine can be increased. In the current research, the laboratory wear results obtained from this device have been compared with those obtained from the numerical modelling of the same device in PFC3D discrete element software, both for the cutting blades and the sample itself. This research showed that in the first abrasion stage of the sample, the difference in the abrasion weight of the experimental study and numerical modelling for the samples varies from 0.91 to 0.768 g, and the average is 0.202 g. Also, the difference between the abrasion percentage of laboratory study and numerical simulation for the samples varies from 6 to 14 %, and the average is 10 %. In step 2 of abrasion, the difference in the abrasion weight of the experimental study and numerical modelling for the samples varies from 0.118 to 0.556 g, and the average is 0.278 g. Also, the difference in the abrasion percentage of laboratory study and numerical simulation for the samples varies from 7 to 14 %, and the average is 11 %. The results of the new tunnel boring machine laboratory simulator revealed insights into wear behavior during different stages of excavation.

Misidentified subglacial lake beneath the Devon Ice Cap, Canadian Arctic: a new interpretation from seismic and electromagnetic data

Abstract. In 2018 the first subglacial lake in the Canadian Arctic was proposed to exist beneath the Devon Ice Cap, based on the analysis of airborne radar data. Here, we report a new interpretation of the subglacial material beneath the Devon Ice Cap, supported by data acquired from multiple surface-based geophysical methods in 2022. The geophysical data recorded included 9 km of active-source seismic-reflection profiles, seven transient electromagnetic (TEM) soundings, and 17 magnetotellurics (MT) stations. These surface-based geophysical datasets were collected above the inferred locations of the subglacial lakes and show no evidence for the presence of subglacial water. The acoustic impedance of the subglacial material, estimated from the seismic data, is 9.49 ± 1.92 × 106 kg m−2 s−1, comparable to consolidated or frozen sediment. The resistivity models obtained by inversion of both the TEM and MT measurements show the presence of highly resistive rock layers (1000–100 000 Ω m) directly beneath the ice. Re-evaluation of the airborne reflectivity data shows that the radar attenuation rates were likely overestimated, leading to an overestimation of the basal reflectivity in the original radar studies. Here, we derive new radar attenuation rates using the temperature- and chemistry-dependent Arrhenius equation, and when applied to correct the returned bed power, the bed power does not meet the basal reflectivity threshold expected over subglacial water. Thus, the radar interpretation is now consistent with the seismic and electromagnetic observations of dry or frozen, non-conductive basal material.

Identification of Marine Landforms as a Form of Coastal Area Management in Pangandaran District

Changes in marine landforms in coastal areas are relatively rapid and need to be analyzed to determine environmental management policies. Complex marine landforms are found in the coastal areas of Pangandaran Regency and have strong pressure to fulfill community activities, not only for local communities but also for outside communities. Basically, community activities are adapted to regional environmental conditions. The aim is to optimize the potential of natural resources and minimize environmental degradation, but in reality, this has not been fully implemented. The method used in this research is a descriptive method using a field survey approach. Marine landforms resulting from the accretion process in the Pangandaran coastal area are spit landforms, aeolian-marine sedimentation in the form of coastal dunes, fluvio-marine sedimentation in the form of estuaries and alates, organic-marine landforms and white sand beaches associated with reefs. The landforms resulting from erosion are Cliffs, notches, wave-cut platforms, stacks, and stumps. The impact of landforms resulting from sedimentation in the Pangandaran coastal area is mainly spit landforms that cover river mouths and the occurrence of flooding, puddles, and even accumulation of organic waste, landforms resulting from erosion, the impact of which is the decline of the coastline accompanied by avalanches of material towards the sea, especially on beaches that have non-resistant rocks such as sedimentary rocks and alluvial deposits. Management of the Pangandaran coastal environmental area must be carried out in an integrated manner, land buritan (hinterland), which has steep slopes and resistant rock, is designated as limited production land, and the development of the spit at the river mouth is made into a jetty, and the beach has beach cups waves with rip currents and water bathymetry. -10 meters above sea level, a wave-protecting wall must be built, and the coastal border area must be used as vegetative-based conservation land.Keywords: Marine landforms, Coastal Management, Pangandaran

Morphometric Analysis for Sustainable River Management: A Case Study of Ciujung Watershed, Banten, Indonesia

Ciujung watershed is located in Banten province, Indonesia. The Ciujung watershed is one of the watersheds that have a significant area coverage, such as Serang, Lebak, and the eastern part of Pandeglang. These areas are developing both in terms of population growth and infrastructure. Therefore, a more in-depth study of the Ciujung watershed, namely morphometric studies, is needed to optimize the utilization of the river's renewable natural resources and mitigate potential flood hazards in the watershed area. The method used is remote sensing based on DEMNAS satellite data using QGis software. The parameters analyzed were watershed shape, watershed area, river branch ratio, and river density. The results show that the Ciujung watershed is divided into 14 sub-watersheds. In general, the sub-watersheds have a bird feather shape, and some are radial and parallel, which causes some research areas to be very at risk of flooding. From the condition of river branching, most areas are unaffected by deformation. A small part of the deformed area occurs in the middle area of the Ciujung watershed. This is interpreted to be related to tectonic activity. The drainage density shows that the Ciujung watershed is based on resistant rocks and materials, so it is easily eroded and causes siltation of the river in the downstream area, which can trigger flooding.

DEM-based analysis of water inrush process of underground engineering face with intermittent joints in karst region


 
 
 
 Water inrush disaster of karst tunnel often lead to significant economic losses and serious casualties, which is an urgent engineering roadblock to be solved in the construction of tunnel in karst area. In this paper, three-dimensional discrete element method considering fluid-solid coupling effect and structural characteristics of water-mud resistant rock mass is adopted to systematically study the evolution law of displacement field and seepage field of intermittent joint type water-mud resistant rock mass of tunnel face and its water inrush critical characteristics during the process of sequential excavation of karst tunnel close to the frontal high-pressure water-rich karst cavity. The results show that: With the tunnel face gradually approaching the front-concealed high-pressure water-rich karst cavity, the stability of water-mud resistant rock mass is increasingly affected by high-pressure karst water, and karst water pressure gradually becomes the main control factor. The closer the tunnel face is to the front-concealed high-pressure water-rich karst cavity, the greater the extrusion displacement of karst tunnel face and its increase amplitude, the higher damage degree of water-mud resistant rock mass of face. With the advance of tunnel excavation, the intermittent cracks in the water-mud resistant rock mass of face gradually connect and form a stable hydraulic connection. The flow velocity and seepage pressure of karst water rise significantly at the moment of overall instability of face and the formation of water inrush channel, showing obvious precursor characteristics. The research achievements provide a reference for early warning and prevention and control of water inrush disaster of karst tunnel face.
 
 
 

Landscape evolution in orogenic plateaus: Insights from quantitative morphotectonic analysis of the Turkish–Iranian Plateau and Caucasus regions

AbstractTo investigate the recent landscape evolution of the orogenic Turkish–Iranian Plateau (TIP) and the Lesser/Greater Caucasus ranges, we perform a quantitative analysis of topography and drainage networks at a regional scale. This analysis focuses on climatic–topographic swath profiles, local relief distribution, longitudinal river profiles, normalized channel steepness index (ksn), paleo‐river profile, and chi analysis (χ). In general, we find that the evolution of topographic relief and river networks are locally controlled by Late Cenozoic volcanism, contrasts in rock strength, and neotectonic activity along regional tectonic structures. However, our results show that the influence of these factors on the landscape evolution of the Greater Caucasus is significantly different from the Lesser Caucasus and TIP. This study shows that a combination of enhanced aridity, rapid uplift of orographic barriers along the TIP margins, and exposure of resistant rock types associated with the regional volcanic activity resulted in low‐relief plateau and the Lesser Caucasus surfaces that are preserved in the upper/middle Kura–Arax and Qezel‐Owzan river catchments. High local relief in the flanks of the Greater Caucasus and west Alborz, downstream increase in channel steepness, and perturbations in the χ plots of the three main rivers indicate that the topography is in a transient state.We reconstruct the paleo‐river profiles from the relict section of the upper Kura–Arax and Qezel‐Owzan rivers and show that the last drastic fall of the Caspian base‐level, which occurred during the Late Miocene–Early Pliocene, can explain the incision of ~500–1000 m gorges (i.e., Amardos) below major knickpoints. Furthermore, local cross‐divide differences of the χ parameter reveal that disequilibrium in the plan‐form geometry of the drainage networks, attributed to the upstream migration of the regional knickpoints towards the plateau interior and integration of plateau areas into the external fluvial system.

Morpho-Hydrological Analysis and Preliminary Flash Flood Hazard Mapping of Neom City, Northwestern Saudi Arabia, Using Geospatial Techniques

Neom city is a unique cross-border city connecting Saudi Arabia, Jordan, and Egypt. Although Neom city is of great and critical importance for Saudi Arabia, few hydrological, natural hazard, and geomorphological studies have been undertaken on this region. This work aims to investigate the hydro-geomorphological characteristics and assess the flash flood hazards in Neom city by investigating several valuable morphometric parameters. The Shutter Radar Topography Mission (SRTM) digital elevation model and hydrological and geological data were analyzed in this study using ArcGIS software. Based on the morphometric parameter results, total stream lengths and stream orders were relatively high (17,956.03 km and 5, respectively), whereas the average bifurcation ratio was recorded to be low at 3.54. Basins 10, 12, 17, 30, 31, 32, and 34 were described as large basins, coarse-textured, elongated, with a medium drainage density, low infiltration values, long overland flows, and high values of constant maintenance. Additionally, the El-Shamy approach for flood hazard assessment was applied side by side with the morphometric analysis, which indicated that the possibility of an intense flood hazard is very low. In general, this study suggests that most of the studied basins cover similar and resistant rocks and soils. They have minimal conditions for flooding events and suitable conditions for underground and surface water resources. Therefore, they display high signals of susceptibility to erosion. The morphometric analysis and flash flood assessment techniques applied in this study were time- and cost-effective for the morphometric characterization of landforms. This text deals with the analysis of several environmental characteristics including hydro-morphological characteristics, drainage topography and lithology, soil erosion, groundwater recharge impact, and flash flood signals. Excellent sustainability plans should be reliant on extensive and varied information about the environment. Thus, integrated analyses incorporating environmental characteristics and flood hazard assessment play an important role in adjusting and adapting the suitable socioeconomic and scientific sustainability of the development of the study city. They build up the basic and essential information required to help decision-makers and sustainability managers design and adjust the most suitable sustainability plans for the study city over the long term.

Karst Rock Relief of Qara and White Desert (Western Desert of Egypt)

The karst rock relief clearly reveals the ways in which the karst surface and caves have been shaped and how they have developed. The oldest traces are the rock features of old karst caves, which were formed under climate conditions entirely different from the current ones, i.e., in the Pleistocene, and which have been dry for a longer period of time. Today, the wind is the prevailing factor in shaping the rock on the surface and in the karst of the White Desert near Farafra in particular, where we can witness the development of an entire range of wind rock features which helps us sort and classify them logically. However, in the wadis near the Qara Oasis a unique rock relief is forming, in which traces of water flow and dissolution of the rock under the sandy deposits are utterly predominant. The rainfall volume is low, however, the heavy rainfall events lasting short periods of time are enough to shape the less resistant rock. The rock features dominating the walls are co-shaped by dissolution and aeolian erosion. Crust forms on those parts of the rock surface that come in contact with water. The bare surfaces, on the other hand, are carved out by the wind. In the places where the crust has flaked off, the wind carves out cups.

Performance of a novel resistant rock bolt with periodic energy absorption and release: theory and experiment

Performance of a novel resistant rock bolt with periodic energy absorption and release: theory and experiment

Lithological controls influence river form in contrasting sub‐catchments: The Scamander and Avenue Rivers, Tasmania

AbstractBedrock influence on river channel form is difficult to assess, with many catchments dominated by glacial erosion and with blanketing sediments from both pluvial and fluvial sources. The Scamander catchment in Tasmania lacks glacial history and features two bedrock‐confined sub‐catchments of similar area and maximum flow length, but one dominated by Mathinna Group sedimentary rocks, and the other with large areas in granite lithology. Lithology types, stream network parameters and near stream slope angles were analysed using geographical information systems, and results of stream cross sections, channel form and planforms were compared for each lithology. Results showed that granite features low gradient, shallow streams with channel slope cross sections of <10°. Granite channels are irregular and dominated by large boulders that create channel roughness and resist incision. Weathering products of coarse quartz sand provide anchorages for in‐channel vegetation. By contrast, sedimentary Mathinna Group rocks feature steeply incised trough‐like channels, with near‐channel hillslope gradients mostly between 30° and 50°. Rectangular blocks disintegrate to gravel cobbles on the channel bed, providing poor anchorage for vegetation. Mathinna lithology influences steep, low roughness channels, and stable, incised recurved meanders formed by river interaction with vertical layers of resistant rock. The resistant bedrock lithology is demonstrated in this study to influence varied river planforms, near‐channel slope gradients, channel sediments and cross sections.

УРАН И ТОРИЙ В СИСТЕМЕ ВОДА – ПОРОДА (НА ПРИМЕРЕ НЕФТЕГАЗОНОСНЫХ ОТЛОЖЕНИЙ СЕВЕРНЫХ РАЙОНОВ ЗАПАДНОЙ СИБИРИ)

The paper presents the first data on the distribution of uranium and thorium in the underground waters of Mesozoic sediments of northern regions of the West Siberian oil and gas basin. The studied waters are very diverse in chemical composition and the amount of total mineralization (from ultrafresh to weak brines). The contents of natural radionuclides vary in a wide range (mg/cu dm): U (4,90•10–7–5,14•10–3), Th (1,90•10–6–8,93•10–3). The Th/U ratio varies from 0.07 to 93.1 and its maximum values characterize the waters of the Valanginian aquifers. The Th/U ratio in water – resistant rocks is in a rather narrow range, it amounts to 1.82–5.24, with an average of 3.56. Against this background, rocks of the Bazhenov Formation are distinguished by the lowest values of Th/ U = 0.07–1.71, its nature of radioactivity is associated with uranium. The formation of the radionuclide composition of underground waters of oil-and-gas-bearing deposits with high Th/U ratios took place in a sharply reducing medium, where thorium has a greater migration capacity than uranium. The evolution of the sedimentary rock basin has led to the widespread development of erosion processes and the redistribution of U and Th in the water-rock system.

Influence of climate-dependent variables on deformation and differential erosion of stratified sedimentary rocks

Rockfalls are major natural hazards for road users and infrastructures in northern Gaspésie (Eastern Canada) where nearly 25 km of road runs along imposing rockwalls. Since 1987, the Ministère des Transports du Québec (MTQ) has reported >17,500 rockfalls that have reached the roadway. While rockfalls are primarily gravitational phenomena, other factors contribute to their development. The long-term interaction of a series of processes leads to rock instabilities. They are never caused solely by the most recent visible change. This study aims to better understand the influence of climate-dependent variables on the mechanical deformations that leads to the erosion of stratified sedimentary rock sequences. To achieve this, a flysch rockwall was instrumented with crack meters and a network of hydrometeorological sensors. The major deformations affecting stratum of siltstone and sandstone were identified and correlated with climate-dependent variables. Results highlighted that irreversible deformations in the first decimeters of rock wall surface are mainly induced by rainfall and snowmelt, by temperature fluctuations around the freezing point and to a lesser extent, by large thermal variations. The water content fluctuations at the rock surface are more effective at generating irreversible deformations in the clayey siltstone strata than freeze-thaw cycles and high amplitude thermal variations. In the sandstone strata, irreversible deformations were primarily caused by freeze-thaw cycles and water content fluctuations at the rock surface. The long-term trends in the sandstone and siltstone strata recorded by crack meters, along with field observations, highlight mechanisms that lead to the development of superficial rock instabilities in this type of geology. Our results show that the retreat and settlement of the weak rock strata (clayey siltstone) causes the gradual overhang of the resistant rock strata (sandstone). As a result, sandstone blocks will eventually slide or topple on the eroding weak rock strata below. The results of this study underscore the importance of studying rock wall dynamics as a whole to understand the mechanisms that lead to the development of hazardous large-scale rock instabilities.

When knickzones limit upstream transmission of base-level fall: An example from Kaua‘i, Hawai‘i

AbstractA threshold drainage area limits fluvial transmission of base-level fall and may be expressed in the form of a waterfall or a series of waterfalls, defined here as a knickzone. Knickzones on the west coast of Kaua‘i, Hawai‘i (USA), exhibit evidence of a threshold drainage area. Eighteen (18) of the 25 knickzones in our study area are located at the coast or a tributary junction, have a drainage area <1.5 km2, and have been stationary for at least 1.5 m.y. The other seven knickzones are located >1 km upstream from the coast or nearest tributary junction and range in drainage area from 1 to 5.5 km2. Both sets of knickzones limit incision relative to canyons without knickzones. Field observations show strong ‘a‘ā flows and dikes always crop out at the lip of knickzones, suggesting these resistant rocks and coarse sediment generated from them act to inhibit knickzone migration. A model incorporating flood records and channel conditions above knickzones shows thresholds of coarse sediment entrainment are never exceeded below 1 km2. Our results demonstrate knickzones on the west coast of Kaua‘i are enduring features explained by resistant lava flows and physical limits in bedrock incision.

Ongoing landscape transience in the eastern Amazon Craton consistent with lithologic control of base level

AbstractGeomorphic features such as drainage captures, knickpoints, paleochannels, and wind‐gaps have long been observed in the Amazon region and typically thought to result from climate change and intraplate tectonics. The influence of rock type as a trigger of these landscape transients is largely overlooked. In the eastern Guiana Shield of the Amazon Craton, shield rivers flow over to the sedimentary rocks of the Amazon Basin across a sharp lithologic transition before their confluence with the Amazon River. This transition is marked by an expressive main escarpment (ME) formed over resistant sandstones of the basal units of the Amazon Sedimentary Basin. Here, systematic patterns of divide migration and river captures provide a natural laboratory to study the influence of rock type in landscape transience in a cratonic setting. Through quantitative geomorphologic analysis of the topography, drainage divides, and rivers, we investigate if this sharp lithologic transition contributed to the observed patterns of drainage rearrangement. The results revealed that rivers of larger drainage areas flowing across shorter lengths over the resistant rocks of the ME systematically capture neighbouring basins. We argue that, as tributaries draining the shield respond to downcutting and/or base‐level fall of the Amazon River, bedrock incision and knickpoint propagation are differentially slowed down by the resistant rocks according to their incision capacity, generating a series of transients such as drainage capture and divide migration. The widespread and systematic geomorphic features suggest this mechanism could be an important autogenic control of drainage network rearrangement in the Amazon region and other post‐orogenic landscapes as well. The protracted exhumation of resistant rocks in cratons and intraplate settings may keep landscapes in perpetual disequilibrium depending on their lithological complexity and offer an exceptional natural laboratory to study landscape dynamics associated with rock type.

Fluvial evolution in a growing thrust-fold range of the Yumu Shan, NE Tibetan Plateau

In an active thrust-fold belt, the drainage evolution, such as the alternation between transverse and longitudinal rivers, will influence the surface erosion within the range and the sedimentary sequence in the foreland basin. However, knowledge of the controls of changes in transverse or longitudinal drainage patterns in an uplifting range is limited. The Yumu Shan, on the northeastern margin of the Tibetan Plateau, is an example for a young and active thrust-fold range that shows evidence for drainage reversals since ∼3 Ma. The materials we used are the late Cenozoic depositional sequences around the Yumu Shan. Analyses of the lithology, grain size, roundness, and clast orientation of gravel deposits on the northern and southern flanks, combined with the results of cosmogenic nuclide burial dating, reveal that a transverse river, the Liyuan River, crossed the Yumu Shan range during 3.0–1.8 Ma by eroding weak Cenozoic sedimentary rocks. After 1.8 Ma, however, this transverse river was deflected and flowed along the edge of the range, and a longitudinal river developed along the back flank of the range. This process was synchronous with the exposure of resistant Paleozoic rocks by the continuous uplift of the range. After comparison with other potential controlling factors for drainage reversals, such as variations in rock uplift, climate or upstream aggradation, we find that the change in bedrock resistance was the most likely control on the change from a transverse to a longitudinal drainage pattern in this relatively young thrust-fold belt. Furthermore, through comparison with a series of active fold-thrust belts worldwide, we propose a simple conceptual model for the drainage evolution of active fold-thrust belts. In the earlier stage of the uplift, the exposed soft sedimentary rocks will cause transverse (antecedent) rivers to cross the range. After the continuous uplift of the range, resistant rocks cause the deflection of a transverse river and its change to a longitudinal river along the back flank of the range. In the final stage, after the several million years to around ten million years of uplift, with the development of a mature range, the local base level of the foreland will greatly fall, promoting a return to a transverse drainage pattern by headward erosion and capture of longitudinal rivers.

Integrated geophysical signatures and structural geometry of the Kabinakagami Lake greenstone belt, Superior Province, Ontario, Canada: Exploration implications for concealed Archean orogenic gold deposits

Geophysical exploration for concealed orogenic gold deposits is challenging because petrophysical contrasts between the gold lodes and their host rocks are normally subtle. Most greenstone-hosted lode‑gold deposits do not contain strong conductors as they normally contain <5 vol% of poorly conductive disseminated arsenopyrite and pyrite. Where there is no outcrop, reliance must be placed on lithological and structural interpretations from aeromagnetic data.Airborne Induced Polarization (AIP) Cole-Cole parameters from helicopter time-domain electromagnetic (HTEM) surveys are demonstrated to be effective in geophysical exploration for concealed gold deposits in the Kabinakagami Lake greenstone belt in Ontario, Canada. Interpretation reveals that most AIP positive responses are associated with clays and all known gold deposits in the study area are in resistive rock formations. Hence, resistivity-scaled chargeability (RSC) can be used to detect weakly chargeable zones within these resistive units.Deep Neural Network (DNN) predictive targeting analysis is utilized to integrate the AIP apparent resistivity, resistivity-scaled chargeability (RSC), EM induction time-constant, and magnetic data. The DNN results imply that the known gold occurrences coincide with high DNN probabilities, and hence exploration targets can be identified based on DNN analysis. From a geological perspective, gold prospects also occur at triple-point junctions between granite intrusions and at probable intersections between potentially hosting shear zones and oblique cross faults or dykes, both common structural geometries for orogenic gold deposits. Consequently, DNN predictive targeting results based both on HTEM and magnetic data, and consistent with expected structural geometries, are proposed as a vectoring tool in the generation of drill targets during exploration for concealed orogenic gold deposits in greenstone belts such as those of the Superior Province, Canada.

Morphometric Analysis of Bhesra Kalan Micro-watershed using Remote Sensing and GIS Technique

The present study has been carried out to analyse morphometric characteristics of Bhesra Kalan micro-watershed of Udaipur (Rajasthan) by using remote sensing and GIS technique. The area of the micro-watershed is 1060 ha. Bhuvan DEM data of 30 m spatial resolution and topographical maps have been utilised to analyse stream network and determine geomorphological parameters (linear, areal and relief aspects) using in the GIS environment. The drainage network of the research area came out to be dendritic and the 4 order stream thobserved as trunk order. The bifurcation ratio (3.24) indicates an undistorted drainage network and low structural disturbance in area. Form factor (0.227), elongation ratio (0.538) and circulatory ratio (0.276) shows elongated shape of watershed. Drainage density (2.626 km km ) -2implies permeable sub-surface material with sparse vegetation, mountainousrelief and coarse drainage. The value of constant of channel maintenance (0.381 km km ) shows steep slope, high surface runoff and low permeability in the watershed. The low value of relief ratio (0.052) 2 -1 characterises less resistant rocks in area. The ruggedness number (0.922) indicates the steep slope of the watershed. The findings of this study provide complete information about the watershed's geomorphological characteristics, which may help in watershed planning and management and explore groundwater potential.

Comparison of transient electromagnetic fields excited by single- and double-line grounded-wire sources on land

SUMMARY The lack of a systematic comparison of field surveys on land makes it challenging to select a suitable grounded-wire transient electromagnetic (TEM) source. Therefore, in this study, we compare land-based TEM methods with single- and double-line grounded-wire sources in the broadside direction. The comparison results indicate that the amplitude of the electric field from the double-line source is one or two orders weaker than that of the single-line source in the same time range. Further, we compare the detectability of horizontal electric fields for resistive or conductive targets by analysing the root mean square misfit and decay curves. According to the decay curve analysis, the double-line source shows better detectability for resistive targets, whereas the single-line source has a larger depth of investigation in the broadside direction. In the presence of a resistive target, sign reversal is more likely in the broadside direction for the double-line source than for the single-line source. In the field survey over Kalatongke Ni-Cu sulphide deposits in Xinjiang, China, both single- and double-line configurations can locate the resistive target; however, the latter configuration outperforms the former in discriminating the different values of the resistive rocks in the broadside direction. The double-line source will be the preferred choice for exploring resistive targets in the broadside direction.

Study on Catastrophe Information Characteristics of Water Inrush in Karst Tunnel by Drilling and Blasting Method

When building tunnels in karst areas, the hidden high‐pressure water‐bearing karst caves are prone to cause geological disasters such as water inrush and mud gushing. In order to study the disaster process of water and mud resistant rock mass with the quasi‐masonry structure and the accompanying catastrophe information of water inrush in karst tunnels by the drilling and blasting method, a new method based on the DEM and fictitious joint technology is adopted to simulate the evolution process of water inrush and study the evolutionary characteristics of catastrophe information like seepage pressure and displacement under the conditions of different joint inclination angles, tunnel depths, and thickness of the water and mud resistant rock mass. The research results show that (1) the seepage pressure and displacement in the water and mud resistant rock mass decrease and increase respectively along the water and mud resistant rock mass from top to bottom in the process of water inrush. (2) The displacement and seepage pressure in the water and mud‐resistant rock mass increases with the increase of the joint inclination angle. The greater the tunnel depth and thickness of the water and mud‐resistant rock mass, the faster the propagation speed of the fissure zone. (3) With the increase of the water and mud‐resistant rock mass thickness, the failure mode of the tunnel outburst layer structure gradually changes from the overall collapse to the partial collapse of the vault to form a relatively stable slump arch. The research results can provide some guidance for tunnel construction in the karst tunnel.

International cooperation of S. I. Subbotin Institute Geophysics, NAS of Ukraine for 2010—2020

The geological structure of the lithosphere of the main tectonic structures has been refined for the territory of Ukraine and adjacent regions of Slovakia, Poland, Romania, Russia, as well as Bulgaria, the Antarctic Peninsula (West Antarctica) and Southeast Asia, and new data have been obtained on geophysical impacts that can affect the environment. A geodynamic scenario has been developed for the formation of large-scale folding of the Fore- Dobrudzja Trough, the South Ukrainian monocline and the Ingul block of the Ukrainian Shield, caused by tectonic events associated with the closing of the Paleotethys and Neotethys oceans in the Mesozoic. In the Pripyat-Dnieper-Donets Basin, the structure of the earth’s crust and upper mantle can reflect different intensities of rifting, from its passive stage in the Dnieper Graben to active rifting in the Pripyat Trough. An analysis of the geoelectric structure of the Earth’s crust in the Ukrainian Eastern Carpathians indicates that seismic events occur mainly in resistive solid rock domainswhich surrounded by aseismic high conductive zones consisting of at least partially melted material. The present-day mutual position of the Ukrainian shield and Fennoscandia stabilized 1720—1660 Ma. The age, distribution, orientation and composition have been studied for the LatePalaeoproterozoicdykes in the Volyn, Ingul and Azov blocks of the Ukrainian Shield. Eastern Crimea and the Sorokin Trough are fragments of a tectonic wedge formed after the Paleocene. The geothermal conditions of the Intra-Carpathian region are due to subduction during the closure of the Pannonian sea basin and the collisional interaction of the Eurasian plate with the microplates system of this region. In Bulgaria, most earthquakes occur outside high-resistive domains. The tectonic stages are reconstructed for the formation of the northern part of the Antarctic Peninsula in the Mesozoic-Cenozoic. The relationship has been established between the geomagnetic field and climate change, with it being different for the Northern and Southern Hemispheres. The results have been obtained within the framework of 25 international projects and 6 temporary international target teams of S. I. Subbotin Institute of Geophysics, NAS of Ukraine consisting of researchers from 23 countries. The results are presented in 53 publications, 38 of which are indexed in the Web of Scienct database, and 32 papers are published in 20 international journals and special publications of 10 countries with different impact factors (from 0,101 to 4,214), whose average impact factor is 3,341, and the total one is 66,815.