Displacement Zone Research Articles

Dike-induced stresses and displacements in layered volcanic zones

During a volcanic unrest period with dike injection, one of the main scientific tasks is to assess the geometry and the propagation path of the dike and, in particular, the likelihood of the dike reaching the surface to erupt. Currently, the dike path and geometry (including depth and opening/aperture) are both partly determined from geodetic surface data using mostly dislocation models that assume the volcanic zone/volcano to be an elastic half space of uniform mechanical properties. By contrast, field observations of volcanic zones/volcanoes (active and extinct) show that they are composed of numerous layers whose mechanical properties (primarily Young's modulus) vary widely and whose contacts commonly arrest dikes. Here we provide field observations and numerical models on the effects of a typical variation in Young's modulus in an active volcanic zone on the internal and surface stresses and displacements induced by a dike whose tip is arrested at 0.5 km depth below the surface of the volcanic zone. Above the layer or unit hosting the dike are four layers of equal thickness. We vary the Young's modulus or stiffness of the fourth layer (the one adjacent to the layer or unit hosting the dike) from 10 GPa to 0.01 GPa, while all the other layers/units maintain their Young's moduli in the model runs. The results show that as the fourth layer becomes more compliant or soft (0.1–0.01 GPa) dike-induced stresses and displacements (lateral and vertical) above the layer, including those at the surface, become suppressed but the stresses and displacements of the layer/unit hosting the dike increase and their peaks do not coincide in location or magnitude with those of the other layers. Thus, the dike-induced internal deformation of the volcanic zone increases as the fourth layer becomes softer. Also, the tensile-and-shear stress peaks at the surface occur at locations widely different from those of maximum surface uplift. More specifically, for a comparatively stiff fourth layer (1–10 GPa), the surface tensile and shear stresses peak at lateral distances of 0.5–0.7 km from the projection of the dike to the surface. (Essentially no tensile/shear stresses reach the surface when the fourth layer is as soft as 0.1–0.01 GPa, so that there are no stress peaks). By contrast the maximum surface displacements (uplift) peak at lateral distances of 2.8–3.3 km from the dike projection to the surface. If tension fractures or faults – in particular the boundary faults of a graben – are induced by the dike, they should form at the tensile/shear stress peaks and not, as is commonly suggested, at the location of the surface displacement peaks. Our results thus suggest that any dike-induced graben is likely to be of a width about twice the depth to the tip/top of the arrested dike. The results demonstrate that elastic half-space models overestimate the dike-induced surface stresses, and thus the depth to the tip/top of the associated dike. In particular, the models presented here indicate that, for typical dikes little or no dike-induced surface deformation would be expected until the dike tip propagates to depths below the surface of less than a kilometre.

Investigation of the joining zone displacement of cross-wedge rolled serially arranged hybrid parts

Within the Collaborative Research Centre (CRC) 1153 “Tailored Forming “the manufacturing of hybrid bulk components is investigated. Therefore, a process chain consisting of joining, forming, milling and quality control has been established by multiple subprojects. Within subproject B1 of the CRC forming of hybrid parts by the incrementally forming cross-wedge rolling (CWR) process is investigated. The superior aim is to determine process limits and capabilities, when forming parts consisting of different materials joined by varying technologies. In this paper, the investigation of cross-wedge rolling of serially arranged hybrid parts made of steel and aluminium is described. The focus of the research presented in this publication is the displacement of the joining zone of hybrid parts due to the cross-wedge rolling process. Therefore, finite element simulations have been developed, that allow the investigations of hybrid solid components. After simulation of various variations of the cross-wedge rolling process, i.e. differently shaped tools and forming velocities, experimental trials were carried out with identical parameter sets. A comparison of simulation and experiment, showed that the simulation model is capable of describing the cross-wedge rolling process of hybrid parts. The standard deviation of the displacement of the joining zone between simulation and experimental trials is 8.8% with regard to all investigated cases.

Peculiarities of surgical technique using a capsule ring for intra-capsular fixation of IOL in children with congenital subluxation of the lens

The aim of the work is to develop a differentiated method of surgical treatment of children with congenital ectopia of the lens using a capsule ring and intra — capsule fixation of IOL. Material and methods. 15 children (28 eyes) at the age of 5–8 years with congenital ectopic lens I–III degree with the syndrome of Marfan, Weil — Marchesani, homocystinuria and isolated pathology were operated. The lens was removed after the introduction of the capsular ring by the method of phakoaspiration and aspiration — irrigation using viscoelastics. One-pieces models of the Acrysof IOL SN60AT and Hoya iSert model 251 were implanted. Anterior capsulorhexis was performed manually (сystotomy, needle, collet tools) and/or using an YAG laser. After hydrodissection of the lens masses, the ring was injected in the capsular bag using the injector, and then removed the lens masses and implanted a one-piece IOL. Results. The technique of performing individual stages was determined by the lens ectopia degree. At I–II degree of ectopia, manual or YAG-laser circular anterior capsulorhexis was performed. Limited anterior vitrectomy was performed in the zone of lens displacement at the III degree of ectopia and the presence of vitreous body. Visual acuity before surgery was from 0.04 to 0.1–0.15, after surgery — 0.1–0.15 — 0.6. Conclusion. The use of differentiated methods of different stages of surgery and the intra — capsule ring in congenital ectopia of the lens allows intra-capsular IOL implantation with high functional and anatomical results at a low level of intra-and postoperative comp lications.

Ecological and Hydrogeological Problems of the Old Industrial Regions of the Middle Urals (Russia)

Mining of mineral deposits leads to the formation of mining landscapes, within which specific hydrogeochemical systems arise. Following the dewatering to the depths of tens and hundreds of meters, processes of technogenic hyper-genesis and mineral formation are developing, especially in areas where the continuity of rocks is disturbed. Here, the sulfuric acid weathering crust is formed, which contains secondary minerals, including readily soluble crystalline hydrates of sulfates. The article presents the results of the analysis of the hydrochemical situation within the abandoned Levikha mine (Middle Urals). It is shown that the reason for the formation of unloading of acid mine waters on the surface during postmining is the change in the hydrodynamic conditions (cessation of the drainage and the filling of the depression cone), the dissolution of secondary minerals in the technogenic zone of hypergenesis (in the zones of collapse and displacement). The mass consumption of components at the post-operational stage is comparable to the rate of oxidative weathering of sulfides during the operation of the dewatering. The half-life of the components is about 5 years, and the formation of contaminated mine waters will last at least 50 years. These results are the basis for determining the strategy and tactics of planning work to eliminate the accumulated damage to the environment of the mining landscapes of the Middle Urals at the post-mining stage.

Deformation and Failure Response Pattern of Schistosed Surrounding Rock to Its Anisotropic Properties

The anisotropy of schist usually has a complex influence on stability of tunnel surrounding rock. In this study, the schist anisotropy and its variation with the confining pressure are analyzed by the triaxial compression test. Then, geological models of tunnel under typical schistose angles α are established based on the highway tunnel project from Shiyan City to Fangxian County in China. Furthermore, the anisotropic failure mechanism, plastic zone distribution and displacement distribution of surrounding rock are investigated to understand its deformation and failure response pattern to the buried depth of tunnel and variable anisotropy. The results show that increased confining pressure weakens deformation anisotropy and weakly strengthens strength anisotropy of the schist. As the buried depth of tunnel changes from 60 to 140 m, the plastic morphology of surrounding rock with α = 0° presents a similar oval and it has a horizontal development trend. When α = 45°, it shows a spiral sector which has oblique extension as well as the increased angle θ between the long and short axis. While a cap shape with vertical development trend when α = 90°. With the weakening deformation anisotropy of surrounding rock, the anisotropic influence coefficient $$\gamma_{1}$$ decreases gradually, indicating that schistose plane engenders a diminishing effect on the anisotropic deformation of surrounding rock as buried depth of tunnel increases.

Solving the cohesive zone model analytic function for concrete based on wedge-splitting test on a compact tension specimen

In this paper, the cohesive zone of concrete is investigated using wedge-splitting test on a compact tension specimen. First, the stress function of the wedge-splitting test on a specimen was obtained by the boundary collocation method. Followed by the actual the wedge-splitting test on a compact tension specimen, the cohesive zone length and the crack opening displacement (COD) in the cohesive zone were obtained by using the digital image correlation method (DICM). Based on the stress function and test data, the weight function that satisfied the conditions of COD in the cohesive zone was determined by superposition of analytic functions with the same crack length but different cohesive zone lengths. Next, the cohesive zone model analytic solutions was determined by the weighted integral method, and the tensile strain softening curve and the fracture energy were obtained. Finally, by comparing the results, it was found that the COD obtained from the cohesive zone model analytic solution was close to the experimental COD, and in addition, the fracture energy was very close to the fracture energy determined using softening curve forms those are frequently used, and the calculated fracture energy was very close to the measured fracture energy. The work shows that the method of determining cohesive zone model analytic solutions using the COD works, revealing a new method for solving the tensile strain softening curve.

Regularities of groundwater quality formation at the abandoned copper mines of Levikha ore field (Middle Urals, Russia)

In the Urals region in recent decades, dozens of copper mines, which are the most dangerous in terms of environmental impact, have been closed and flooded. In many of them, acid mine waters continue to form, the concentrations of most components in which exceed the permissible values by several orders of magnitude. The formation of the chemical composition of acidic groundwater has a pronounced unsteady character: a sharp increase in the content of all components in the water after flooding and a gradual decline for many years. On Levikha copper mine (Sverdlovsk region) after filling the depression con in 2007, a site of concentrated discharge of groundwater was formed (technogenic reservoir-a failure in the zone of collapse and displacement). The concentrations of many components 10 years after the completion of flooding are higher than during the development. The analysis of regularities of non-stationary character of hydrogeochemical processes is made on the basis of the data of detailed monitoring and extended definitions of groundwater quality indicators. The main source of acidic water with increased mineralization is the collapse zone, within which the process of drainage for several decades formed technogenic sulfuric acid weathering crust enriched with secondary minerals. According to the data of numerical geofiltration modeling, in the hydrodynamic balance the lateral flow coming from the surrounding areas is 60%, its value is manifested in the dilution of the solution, which is formed in the collapse zone. The time of movement of this flow in the area of collapse is 6–8 years, extremely high values of almost all indicators in the man-made reservoir are observed during this period. According to the inverse physical-chemical modeling (program code Visual MINTEQ ver. 3.0 / 3.1 was used) the composition of rocks, as a result of dissolution-deposition of which underground waters in the area of the flooded mine can be formed, is determined. The duration of the process of formation of acidic groundwater is estimated at tens of years.

Scaling of fault damage zones in carbonate rocks

A renewed interest in fault damage zones is aimed at better understanding stress perturbation around faults, earthquake ground motions and fluid flow in the upper crust. In this study, we analyse fault/fracture systems at the outcrop and map scale and define displacement - thickness (D-T) scaling of fault damage zones using scanlines, in carbonate rocks in France and Spain. We determine fault displacement and damage zone thickness perpendicular to fault planes and far from fault tips for 12 selected faults in four study sites. The data show a logarithmic decrease of fracture frequency from the fault cores. This decrease is characterized by local frequency peaks corresponding to variably-linked secondary fault segments and abandoned tips within the fault damage zone. D-T data comprised between 0 and 100 m of net fault displacement show a nearly linear scaling with very little scattering. Including two additional data for D > 100 m, the best fit corresponds better to a power law. We propose a new model based on fault segmentation and linkage to explain the linear scaling observed up to 100 m displacement, and we discuss the non-linear behaviour with respect to the role of mechanical layer thickness and the inhibition of the segmentation process down dip for large-scale faults.

Особенности расчетов потерь мощности в тяговых сетях с учетом перемещения электрических потребителей энергии

Summary Objective: To study the specificities of average currents and power loss calculation in electric traction networks in conditions of constantly changing load. Methods: Probabilistic methods of calculation were applied. Results: Occurrence probability of a certain number of trains in an inter-substation zone was calculated on the basis of train schedule analysis. Calculations of currents and power loss in different elements of a traction energy system with a fixed number of trains in an inter-substation zone were given. It was found that the obtained values of currents and power loss correspond with their occurrence probability depending on the number of trains in an inter-substation zone. For reasons given, a conclusion was made that average values of currents and power loss in traction network elements may be considered as expectation values. Due to the presence of trains with different weight in an inter-substation zone, the method of reducing the currents of these trains to averaged values based on occurrence probabilities of the currents in question was shown for trains with relevant weight range as well as their expectation values. Practical importance: Due to constant electric traction load displacement in an inter-substation zone, and uneven current consumption as well as the presence of a different number of trains, the conducted calculations based on probabilistic methods are the most applicable for determination of energy consumption and power loss in traction energy systems.

EVALUATION OF THE TECTONIC DISPLACEMENTS IN FAULT ZONES OF THE ALTAI, ACCORDING TO THE EARTHQUAKE FOCAL MECHANISMS

The characteristics of horizontal displacements in fault zones of the Altai-Sayan mountain region are revealed with use of the earthquake focal mechanisms data. Left-lateral strike-slips are characteristic for the Bogdo, Southern Tannuol and Sayan-Tuva faults, and for the eastern part of the Bollnay fault. Right-lateral strikeslip is characteristic for the Koktokay fault.

The MW 7.8 Earthquake of July 17, 2017 off the Commander Islands and Other Large Earthquakes at the Western Segment of the Aleutian Island Arc

This paper discusses the tectonic setting, seismological characteristics, and the aftershock process for the great (MW = 7.8) Near-Islands Aleutian earthquake of July 17, 2017 off the Commander Islands. Our analysis showed that the rupture zone as inferred from the distribution of aftershock epicenters in the shape of an elongate narrow zone approximately 400 km long completely covered the north slope of the Commander Islands uplift and was confined to the Bering Fault. The rupture zone involved this entire earthquake-generating area as far as a transverse structure west of the Near Islands group (Attu Island). The fault-plane solutions and the inferred displacements in the rupture zones of the main shock and of the largest foreshocks and aftershocks revealed the rupture to be a practically pure right lateral movement. The aftershock process of the July 17 earthquake was occurring at rather a sluggish pace for such a large earthquake. In addition, the process involved two other features to distinguish it from the aftershock processes of most Kuril–Kamchatka earthquakes: (1) a low release of the cumulative scalar seismic moment (M0cum aft), which amounted to between 0.75% and 1.0% of the mainshock seismic moment (M0me), according to several estimates; and (2) a very slow increase in the deficit of seismic moment (M0) release. At the same time, the duration of the quasi-stationary phase in the release of M0cum by aftershocks, which is estimated to have lasted approximately half a year and which occupied much of the entire duration of the aftershock process for this earthquake seems to be unusually long. These features in the aftershock process of the Near-Islands Aleutian earthquake of July 17, 2017 distinguish the process from those common to most large Kuril–Kamchatka earthquakes. Overall, the rupture zone can be regarded as a transform feature between two Benioff zones (The Aleutian and the Kuril–Kamchatka ones) rather than as a subduction event, as is typical of the two latter arcs.

Analogue Modeling of Plate Rotation Effects in Transform Margins and Rift‐Transform Intersections

AbstractTransform margins are first‐order tectonic features that accommodate oceanic spreading. Uncertainties remain about their evolution, genetic relationship to oceanic spreading, and general structural character. When the relative motion of the plates changes during the margin evolution, further structural complexity is added. This work investigates the evolution of transform margins and associated rift‐transform intersections, using an analogue modeling approach that simulates changing plate motions. We investigate the effects of different crustal rheologies by using either (a) a two‐layer brittle‐ductile configuration to simulate upper and lower continental crust, or (b) a single layer brittle configuration to simulate oceanic crust. The modeled rifting is initially orthogonal, followed by an imposed plate vector change of 7° that results in oblique rifting and plate overlap (transpression) or underlap (transtension) along each transform margin. This oblique deformation reactivates and overprints earlier orthogonal structures and is representative of natural examples. We find that (a) a transtensional shift in the plate direction produces a large strike‐slip principal displacement zone, accompanied by en‐echelon oblique‐normal faults that accommodate the horizontal displacement until the new plate motion vector is stabilized, while (b) a transpressional shift produces compressional structures such as thrust fronts in a triangular zone in the area of overlap. These observations are in good agreement with natural examples from the Gulf of California (transtensional) and Tanzania Coastal Basin (transpressional) shear margins and illustrate that when these deformation patterns are present, a component of plate vector change should be considered in the evolution of transform margins.

Evolution of E-W strike-slip fault network, the northwestern foreland of Tunisia

The northwestern foreland of Tunisia (El Kef region and its surroundings) is a key area to study the tectonics of main E-W basement strike-slip faults and related structures. To achieve this goal, we used multidisciplinary approaches including field work, paleo-stress analyses and geophysical data. These approaches allowed us to propose a new structural model based on the evolution in space and time of Riedel shear type faults and to highlight their role in the structuring of the study region. During the Mesozoic, E-W normal oblique-slip basement faults (D1: Ghardimaou fault, D2: El Kef-Ouergha fault, D3: Jebel Harraba-Guern Halfaya fault and D4: Tajerouine fault) controlled the architecture and the subsidence of the El Kef Basin within a transtensive setting by block tilting, NE-SW negative flower structures, Triassic salt ascent and deposits thicknesses and facies variations. During the Eocene and Late Miocene, the NW-SE shortening (tectonic inversion) is expressed by the oblique reactivation of the pre-existing E-W faults as dextral strike-slip faults. This reactivation is accompanied by map-scale Riedel shear type faults, where D1, D2, D3 and D4 formed the principal displacement zones (PDZs). The successive movements of these faults cut the study area in several right-lateral shear bands in which subsidiary Riedel fractures (R, R', X, P, T and Y) and NE-SW folds are developed. Fault slip data and fractures analyses, across the study area, show several fracture systems which interact under a NW-SE SHmax. During Quaternary, the NNW-SSE shortening reactivated the preexisting E-W fault networks (PDZs). It also, formed NS left-lateral strike-slip faults, NW-SE grabens, NE-SW reverse faults, and ENE en echelon folds arranged within Riedel shear bands.

Evaluation and prediction of carbon fiber–reinforced polymer cable anchorage for large capacity

Aiming to address the problems of stress concentration on conical wedge anchorage, a fiber-reinforced polymer cable anchorage with segmental variable stiffness of the load transfer medium was proposed. The key parameters that affect the anchorage behavior were investigated. The mechanical properties of the carbon fiber–reinforced polymer tendon and load transfer medium were tested. The failure mode, anchoring efficiency, stress, and displacement in the anchor zone were studied. The parameter optimization was performed using an experimentally verified finite element simulation. The parameters of the anchorage system with large capacity were evaluated. The results demonstrate that the compressive strength of the load transfer medium is the designed stress limit for the anchorage system. The cable does not slip or become damaged in the anchor zone, and the anchoring efficiency reaches 91%. The distribution of the shear and radial stress on the cable surface is smooth, and the stress concentration is greatly relieved. The result of the finite element simulation is consistent with the experimental values when the friction coefficient is 0.15, and the material and geometric parameters of the anchorage system with cable forces of 5000, 10,000, 15,000, and 20,000 kN are suggested. The geometric parameters of the anchor system with diverse cable capacity can be preliminarily designed based on the fitting equations.

Structural expression of a fading rift front: a case study from the Oligo-Miocene Irbid rift of northwest Arabia

Abstract. Not all continental rifts mature to form a young ocean. The mechanism and duration of their cessation depend on the crustal structure, modifications in plate kinematics, lithospheric thermal response, or the intensity of subcrustal flow (e.g., plume activity). The cessation is recorded in the structure and stratigraphy of the basins that develop during the rifting process. This architecture is lost due to younger tectonic inversion, severe erosion, or even burial into greater depths that forces their detection by low-resolution geophysical imaging. The current study focuses on a uniquely preserved Oligo-Miocene rift that was subsequently taken over by a crossing transform fault system and, mostly due to that, died out. We integrate all geological, geophysical, and previous study results from across the southern Galilee to unravel the structural development of the Irbid failing rift in northwest Arabia. Despite tectonic, magmatic, and geomorphologic activity postdating the rifting, its subsurface structure northwest of the Dead Sea fault is preserved at depths of up to 1 km. Our results show that a series of basins subsided at the rift front, i.e., rift termination, across the southern Galilee. We constrain the timing and extent of their subsidence into two main stages based on facies analysis and chronology of magmatism. Between 20 and 9 Ma grabens and half-grabens subsided within a larger releasing jog, following a NW direction of a deeper presumed principal displacement zone. The basins continued to subside until a transition from the transtensional Red Sea to the transpressional Dead Sea stress regime occurred. With the transition, the basins ceased to subside as a rift, while the Dead Sea fault split the jog structure. Between 9 and 5 Ma basin subsidence accentuated and an uplift of their margins accompanied their overall elongation to the NNE. Our study provides for the first time a structural as well as tectonic context for the southern Galilee basins. Based on this case study we suggest that the rift did not fail but rather faded and was taken over by a more dominant stress regime. Otherwise, these basins of a failing rift could have simply died out peacefully.

Finite element analysis of crack-tip opening displacement and plastic zones considering the cyclic material behaviour

Propagation and behavior of fatigue cracks are governed by strain fields in the vicinity of the crack tip. The numerical description of strains in the crack tip presents some challenges in the modelling by the multiscale involved in the fracture analysis. In this study, it is proposed a 2D finite element analysis conducted for fatigue crack propagation experiments (mode I) performed for a railway axle steel EA4T under plane stress conditions. The analysis considers a geometric approach to define a multiscale mesh on a center-crack tension (CCT) specimen for which a nonlinear material model with kinematic hardening was assumed. Crack tip opening displacement (CTOD) and plastic zones were determined for several load levels during loading and unloading states. The results show that the applied correction factors approximate better the crack propagation rate. Furthermore, the quadratic dependence of CTOD with the stress intensity factor was in good agreement with the numerical solutions.

A New Unified Solution for Circular Tunnels Based on Generalized SMP Criterion considering the Strain Softening and Dilatancy

According to the strain‐softening characteristics of rock mass, an ideal elastic strain‐softening model is developed, and the surrounding rock of tunnels is subdivided into the plastic broken zone, plastic strain‐softening zone, and elastic zone. Based on the generalized spatially mobilized plane criterion, an elastic‐plastic analytical solution of a circular tunnel is derived. The effects of intermediate principal stress, strain softening, and dilatancy are considered in the unified solution. The stress, displacement, and plastic zone radius of surrounding rock based on the SMP criterion are compared with those based on the Mohr–Coulomb criterion. Furthermore, the effects of parameters such as the softening modulus, dilatancy angle, and internal friction angle on the deformation and stress of tunnels are discussed. It has been found that the larger the dilatancy angle is, the larger the plastic zone displacement and the radius of the broken zone are. The larger the internal friction angle, the smaller the sizes of the plastic zone, the strain‐softening zone, and the broken zone are. The deformation of surrounding rock in the broken zone is more sensitive to the internal friction angle than that in the strain‐softening zone. The unified solution based on the SMP criterion provides a well understanding for the elastic‐plastic state of tunnels, which can be the guidance for tunnel excavations and support designs.

Working Mechanism of Pile Group with Different Pile Spacing in Dense Sand

Complex interaction mechanism exists between the pile group and soil. To realize the pile‐soil load transmission mechanism in detail, the failure pattern of pile groups installed in dense sand considering different pile spacing was investigated by means of laboratory experimental model test and three‐dimensional discrete element method. The results suggested that the narrow pile spacing was beneficial to the development of the pile tip resistance, and it enhanced the bearing performance of the pile group at the initial stage of settlement. The pile spacing changed the shaft resistance pattern with modification of the strain energy mechanism released within the subsoil. The pile group with 6b pile spacing had higher composite group efficiency. A joint fan‐shaped displacement zone was formed beneath the pile tip for the pile group with 3b pile spacing; this pile foundation presented the block failure mechanism. The sand displacement beneath the cap for the pile group with 6b pile spacing mainly located on the upper part of the piles, the sand displacement around both sides of the piles presented asymmetric, and a relatively independent fan‐shaped displacement zone was formed beneath the pile tip.

Sample Rocks Tests and Slope Stability Analysis of a Mine Waste Dump

The safety and stability of waste dump are vital influencing factors to the mine sustainability and mine employees. Based on a real mine project in a certain open-pit mine waste dump in Tibet, the in situ test on waste rocks from waste dump, including measurements of density, water content, rock size, and natural repose angle, was conducted. Afterwards, these sample waste rocks, of which grain size is less than 5 cm, were selected for indoor large-scale shear test under natural and saturated conditions. By using some engineering methods, the physical and mechanical parameters of waste rocks layer were then determined accordingly. MIDAS-GTS/NX has the advantage of pre-processing modeling. FLAC3D has good computational and analytical capabilities. The process of dump accumulation is simulated numerically. According to the calculation results of FLAC3D, the distribution of stress, displacement and plastic zone in the dump is obtained. FOS (factor of safety) for each analytical step in this model was then calculated through the strength reduction method. The limit equilibrium method is used for waste dump stability analysis considering three states: only applied gravity, applied gravity and rainfall, and applied gravity and underground water. The results from this analysis show that the waste dump is stable. The potential failure modes of waste dump mainly consist of the “combined sliding mode” which has circular sliding in upper side and broken line sliding that cuts through gravel-soil layer into heavily weathered layer in the bottom. This paper documents some of the procedures and approaches utilized for waste dump life-of-mine design analysis. It provides reference for further waste dump optimization.

Evaluation of GPR capabilities in the study of seismogenic faulting and deformation in the bottom sediments of Lake Upoloksha (northeast of the Fennoscandian shield)

The article describes the experience of using the GPR method to study the bottom sediments of Lake Upoloksha located in the Kola Peninsula, Russia. Such sediments are viewed as good archives of various Holocene geodynamic processes, including tectonic and paleoseismic events. This small lake is located in the zone of the active NW-striking lineament, which length is more than 20 km. A series of åsars (eskers) stretches along the lineament. In the previous studies, the bottom sediments of the lake were investigated by geological methods, including core sampling, lithological and micro-palaeontological analysis of sediments. The studies have revealed a horizon which features are indicative of catastrophic changes in the sedimentation conditions due to a single impact. Our study aimed at evaluating the level of informativeness of the GPR method for detecting disturbances in the bottom sediments and new paleoseismic dislocations. The study referred to the hypothesis of the distribution of seismic foci in the Kola Peninsula in the Holocene. A ground-penetrating radar OKO-2 and an antenna unit (150 MHz) were used to survey of Lake Upoloksha in detail. The positions of the main stratigraphic horizons of the bottom sediments were clarified, and their thicknesses were measured more precisely. The GPR measurement error in comparison to the drilling data did not exceed ±0.2 m, which corresponds to the resolution of the antenna used in the survey. The GPR data confirmed the existence of seismic dislocations identified by the geological methods and discovered new zones of displacement and deformation in the organogenic and mineral bottom sediments. The survey detected vertical displacements, which amplitudes vary from 1.3 to 1.7 m, and landslides caused by seismogravitational rock collapse. Based on the GPR data, a bathymetric map was constructed. It shows the positions of the two basins of Lake Upoloksha. The survey provided the basis for a model showing the isosurface of the top of the mineragenous sequence. In the central part of the mineral-base model, there is a series of individual stepwise blocks of the sublatitudinal strike, which result from seismic movements. The GPR survey of Lake Upoloksha demonstrates that the GPR method can be successfully applied to estimate the mineral and organogenic parts of the bottom sediments, study their lithostratigraphic features, and detect changes in the structure of the bottom sediments. Based on the GPR data, it becomes possible to map even the small-scale disturbances.