Discontinuous Zone Research Articles

Enhanced rock mass rating prediction from tunnel face imagery: A decision-supportive ensemble deep learning approach

Ensuring safety in tunnel construction necessitates a rapid and objective evaluation of exposed tunnel faces for proactive rock mass risk assessment. The diversity of rock types and discontinuities contributes to structural complexity and local variability, introducing subjectivity and uncertainty in traditional evaluations based on the experience of field engineers. In this study, a convolutional neural network (CNN) is employed for regression to enhance the objectivity and consistency of rock mass classification via rock mass rating (RMR). The model interprets the entire tunnel face image holistically by identifying and learning from complex patterns, rather than detecting specific geological features like fractured or discontinuity zones. The network model, comprising feature extraction and regression blocks, utilizes the EfficientNet family for computational efficiency and accuracy. Data augmentation and ensemble learning address prediction variability due to image quality, optimizing the model for accurate RMR predictions and providing error ranges. The RMR predictions using excavation site images closely follow the field-evaluated evolution. A server communication-based mobile application is developed for real-time RMR evaluation, enhancing its practical field applicability. In geology, tunnel, and geotechnical engineering, where decisions rely on extensive experience, our approach demonstrates that deep learning can enhance decision-making by analyzing large accumulated datasets to predict optimal outcomes.

Crustal deformation from GNSS measurement and earthquake mechanism along Pieniny Klippen Belt, Southern Poland

The dynamic geological features of the Pieniny Klippen Belt (PKB) in southern Poland are nowadays a focal point of researchers as it is recognised as an active zone of crustal discontinuity. In the present study, we employed long-term analysis of ground-based global navigation satellite system (GNSS) measurements (from 2004 to 2020) to probe the crustal deformation, strain rates, and rotational rates in the PKB unit and the surrounding region, i.e., Magura Nappe (MN) and Podhale Flysch (PF) units. Measured velocities from GNSS observables are modelled by the auto-regressive integrated moving average (ARIMA) method to comprehend the long-term tectonic deformation. Our results showed that the ARIMA-modelled velocity varied from ~ 0.15 to ~ 8.86 mm/yr, indicating about 8.71 mm/yr difference along all units. Such differences suggest that crustal slip along the active thrusts and folds is the major factor causing regional deformation. The strain rates in PKB are also varying from the western to the eastern part. The rotational rates in PKB show a counterclockwise (CCW) pattern similar to the strain rates. These patterns suggesting that the PKB was rotated in the CCW direction with a large angle during the Miocene period. Finally, we analysed the seismicity for a period from 2004 to 2020 by using Bayesian moment tensor inversion and multivariate Bayesian inversion. The Bayesian inversion was applied based on bootstrapping chain analysis to figure out the earthquake mechanism using moment tensor inversion for the mainshock that occurred in Poland on 20 July 2018. The inversion results for the 2018 earthquake resolved a thrusting mechanism with nodal plane-1 having a strike of 346°, dip of 32°, and rake of 92° and a nodal plane-2 with a strike of 163°, dip of 58°, and rake of 89°. Since the seismicity in the Poland region has experienced less significant earthquakes in the last century, it is reasonable to attribute this lower seismic activity to the correspondingly low slip rates discerned through geodetic monitoring efforts.

Modelling permafrost distribution using the temperature at top of permafrost model in the boreal forest environment of Whatì, NT

Current permafrost models in Canadian boreal forests are generally of low spatial resolution as they cover regional or continental scales. This study aims to understand the viability of creating a temperature at the top of permafrost (TTOP) model on a local scale in the boreal wetland environment of Whatì, Northwest Territories from short-term field-collected temperature data. The model utilizes independent variables of vegetation, topographic position index, and elevation, with the dependent variables being ground surface temperature collected from 60 ground temperature nodes and 1.5 m air temperature collected from 10 temperature stations. In doing this, the study investigates the relationship vegetation and disturbance have on ground temperature and permafrost distribution. The model predicts that 31% of the ground is underlain by permafrost, based on a mean annual temperature at TTOP of <0 °C. This model shows an accuracy of 62.5% when compared to cryotic assessment sites (CAS). Most inaccuracies, showing the limitations of the TTOP model, came from peat plateaus that had been burned in the most recent forest fire in 2014. These resulted in out-of-equilibrium permafrost and climatic conditions that TTOP cannot handle well. Commonly, permafrost mapping places Whatì in the extensive discontinuous zone, estimating that between 50% and 90% of the ground is underlain by permafrost. The study shows that a climatically driven TTOP model calibrated with CAS can be used to illustrate ground temperature heterogeneity from short-term data in boreal forest wetland environments. However, this approach likely underestimates permafrost extent and is perhaps not the best-suited modelling choice for near-surface permafrost, which is currently out of equilibrium with the current climate.

Age-related changes in geometry and transparency of human crystalline lens revealed by optical signal discontinuity zones in swept-source OCT images

BackgroundThe shape and microstructure of the human crystalline lens alter with ageing, and this has an effect on the optical properties of the eye. The aim of this study was to characterise the age-related differences in the morphology and transparency of the eye lenses of healthy subjects through the optical signal discontinuity (OSD) zones in optical coherence tomography (OCT) images. We also investigated the association of those changes with the optical quality of the eye and visual function.MethodsOCT images of the anterior segment of 49 eyes of subjects (9–78 years) were acquired, and the OSD zones (nucleus, C1–C4 cortical zones) were identified. Central thickness, curvature and optical density were measured. The eye’s optical quality was evaluated by the objective scatter index (OSI). Contrast sensitivity and visual acuity tests were performed. The correlation between extracted parameters and age was assessed.ResultsThe increase in lens thickness with age was dominated by the thickening of the cortical zone C3 (0.0146 mm/year). The curvature radii of the anterior lens surface and both anterior and posterior nucleo-cortical interfaces decreased with age (− 0.053 mm/year, − 0.013 mm/year and − 0.006 mm/year, respectively), and no change was observed for the posterior lens radius. OCT-based densitometry revealed significant correlations with age for all zones except for C1β, and the highest increase in density was in the C2–C4 zones (R = 0.45, 0.74, 0.56, respectively, P < 0.001). Increase in OSI was associated with the degradation of visual function.ConclusionsOCT enables the identification of OSD zones of the crystalline lens. The most significant age-related changes occur in the C3 zone as it thickens with age at a faster rate and becomes more opaque than other OSD zones. The changes are associated with optical quality deterioration and reduction of visual performance. These findings contribute to a better understanding of the structure–function relationship of the ageing lens and offer insights into both pathological and aging alterations.

Continuous vs. discontinuous garnet growth in mylonitic micaschists from northeastern Sardinia, Italy: Evidence from LA-ICPMS trace element mapping

Garnet with complex, discontinuous zoning is a common occurrence in metamorphic terrains, and the relationship between major and trace element zoning can provide insight into the metamorphic evolution of the host rock. Mylonitic micaschists along the Posada-Asinara Shear Zone in the Axial Zone of the Sardinia Variscan chain contain garnet porphyroblasts, enveloped by the S2 schistosity, with distinct core and rim domains. A large garnet porphyroblasts was investigated by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) mapping. The major element compositional variation follows a bell-shaped zoning, with Ca and Mn contents progressively decreasing, and Fe and Mg increasing, from the core to the outer rim. LA-ICPMS mapping revealed a thin and sharp annular enrichment zone in Y, Sc, Dy, Ho, Er, Tm at the mantle-rim boundary. The trace element (TE) compositional profiles show a central enrichment area for HREE (Tm, Yb, Lu). This enrichment decreases progressively, as a function of atomic number, for Er, Ho and Dy. Elements with even lower atomic number (Tb, Gd, Eu and Sm), are depleted in this central domain, but their content increases in broad shoulders towards the garnet rim. The position of these lateral shoulders migrates progressively rimwards with decreasing atomic number. The REE distribution, trend and behavior in the growth zones of the garnet is an example of TE control during a continuous growth ruled by diffusion-limited REE uptake. The Y + HREE annular enrichment zone, interpreted as resulting from a decrease in the garnet growth rate, reflects a short-lived episode in the garnet growth history.

Tracing fluid infiltration into oceanic crust up to ultra-high-pressure conditions

Fluid–rock interaction within the altered oceanic crust and across the slab–mantle boundary during subduction facilitates element transfer, but the dynamics of fluid transport and fluid–rock exchange during upward fluid migration are still unclear. A study of metamorphic fluid–rock interaction within a section of subducted oceanic crust was carried out on eclogites and metasediments of the ultra-high-pressure Lago di Cignana Unit (NW Italian Alps). The P–T modeling of a quartzschist shows that garnet grew during the prograde and sporadically during the retrograde path and that phengite mainly records the peak to retrograde conditions. Microscale geochemical analysis of garnets has revealed a systematic evolution of oxygen isotopic composition with garnet major element zonation, with extreme within-sample core–rim variations in δ18O between 18 and 4‰ providing evidence for external fluid influx. Garnet in eclogites and calcschists, as well as garnet cores in quartz-rich lithologies, shows normal compositional zoning, as expected for prograde garnet growth, and a relatively constant oxygen isotopic composition. The outer garnet growth zones within a few metasediments show reverse or discontinuous zoning and progressively lower δ18O. Despite major element zoning, the isotopic composition of mica is homogeneous across chemical zoning in one eclogite and one quartzschist, but shows 6‰ variability in another quartzschist. In the underlying Zermatt–Saas serpentinites, antigorite from nine serpentinite samples shows some variation in δ18O, with average δ18O values for individual samples ranging from 1 to 6‰. These results provide evidence for two main stages of external fluid infiltration: (i) fluids from the dehydration of mafic lithologies entered the sequence at peak conditions around 3 GPa, as indicated by the oxygen composition of intermediate zones of mica and garnet, and (ii) low δ18O fluids from serpentinites infiltrated parts of the sedimentary package during exhumation prior to 1.5 GPa, as recorded by the 4‰ garnet outer rims. Samples recording external fluid infiltration are concentrated in the lower part of the sequence, indicating channelized fluid flow, suggesting focused fluid infiltration due to permeability contrasts between metasedimentary and eclogitic lithologies. Channelized fluid flow in the ultra-high-pressure metasediments of Lago di Cignana has not resulted in systematic decarbonation of the metasediments.

GIN method applied to the consolidation of cracked rocks: case study of the Memve’ele hydroelectric dam (southern Cameroon)

The empirical GIN (grouting intensity number) method is one of the most popular methods for structural stabilization and is increasingly used in many projects. The concept of this method is to limit the combination of pressure and volume injected to a specific grouting intensity number in order to control the energy induced in the rock fractures and to avoid heaving. In order to ensure the water tightness of the foundation of the Memve’ele hydroelectric dam, the treatment by the GIN method was implemented. The protocol implemented consisted to carry out a veil of injection drilling, consolidation, and control of effective treatment on each geotechnical hazard zone. Thus, 1240 injection boreholes were opened over a total length of 1600 m, i.e.: 613 pre-treatment boreholes and 627 consolidation boreholes. The results of the monitoring tests show that the 0.7 cement grouting treatment contributed to a reduction in crack permeability to less than 5 Lu (Lugeon units), a reduction of over 94%. This confinement of the rock was confirmed by geophysical imagery whose signature at the fractured interval varied after treatment. Geophysical and geohydrological characterization through permeability testing and electrical tomography revealed the existence of highly permeable discontinuity zones (over 90 Lu) below the bedrock surface, up to 15 m wide. Notwithstanding the volume of drilling carried out, the results obtained support the use of the GIN method in the stabilization of foundations of structures in the granite-gneissic basement zone.

Numerical Simulation of Downward Flame Propagation in Discontinuous Region of Solid Fuel

This paper presents a numerical model that investigates the characteristics of flow, heat, and mass transfer on downward flame propagation in the discontinuous region of solid fuel. Simulations were carried out for various discontinuous distances to analyze the morphology of the flame front and the competition between the “jump” of flame spread and heat transfer from the flame to the unburned area. The results demonstrate that there is a “jump” in the flame propagation in the discontinuous zone, with the flame front exhibiting a defined “acute angle” that undergoes a process from large to small during the flame spreading in the discontinuous area and deflects towards the discontinuous area of the material. The temperature in the discontinuous zone reaches a peak, and the average flame spread rate initially increases and then decreases with the increase of discontinuity distance until the flame spread stops. The study provides valuable insights into the growth and development of fires involving discretely distributed combustible materials.

Geological Investigation of Lead Mineralization Associated with Silicified Zone in Büyük Kızılcık (Göksun-K.Maraş) Region

Doğu Toroslar'da farklı ortam ve tektonik koşullarda oluşmuş birbirinden farklı istifler yüzeylemektedir. Bu istifler tabandan tavana Üst Jura-Kretase yaşlı peridotitler, bantlı gabro, izotrop gabro, levha dayk karmaşığından oluşan Kömürhan Ofiyolitleri ve Bodrum Napı’na ait metamorfik kaya birimleri yer almaktadır. Kömürhan Ofiyolitleri ve Bodrum Napı Geç Kretase yaşlı Baskil Granitoyidleri tarafından kesilmiştir. Baskil Granotoyidinin kesmiş olduğu birimler içerisinde cevherleşmeye ilişkin alterasyon zonları gözlemlenmektedir. Cevher mikroskopi çalışmalarında pirit, sfalerit, galenit, arsenopirit, manyetit ve hematit tespit edilmiştir. Pirit üzerinde yapılan izotop analizinde δ 34S değeri -3 %o olarak belirlenmiştir. Kuvars mineralleri üzerinde yapılan sıvı kapanım analizinde 69-127 °C arasında ve ortalama olarak 103 °C epitermal oluşum sıcaklığı belirlenmiştir. Çalışma alanında cevherleşmelerin birincil kökeni Miyosen’den itibaren bölgeyi etkileyen asidik karakterli volkanizmanın etkisiyle metamorfik istifler içerisindeki fay ve kırık çatlak sistemlerinde yerleşmiş sülfürlü yataklanma şeklinde oluşurken, ikincil cevherleşmelerin birincil sülfürlü minerallerin çözünerek tektonik olaylar sonucu oluşan süreksizlik zonlarında depolandığı düşünülmektedir.

Crack propagation in quasi-brittle materials by fourth-order phase-field cohesive zone model

A phase-field approach becomes a more popular candidate in modeling crack propagation. It uses a scalar auxiliary variable, namely a phase-field variable, to model a discontinuity zone in a continuity domain. Furthermore, the fourth-order phase-field approach produces a better convergence rate and more accurate solutions than the second-order one. However, it is available for modeling crack propagation in brittle material. This study addresses the fourth-order phase-field model combining the non-standard phase-field form with a cohesive zone model (CZM) to predict crack propagation in quasi-brittle material. A Cornelisson's softening law is used to capture the high precision of crack propagation prediction. The concrete material is considered as a quasi-brittle one. For computation efficiency using NURBS-based finite elements, Virtual Uncommon-Knot-Inserted Master-Slave (VUKIMS) technique is employed to derive a local refinement mesh. Numerical results are verified by the published ones from literature. It was found that the peak load and crack path are independent of the element size and insensitive to the length-scale number using the fourth-order phase-field CZM. Our proposed model shows the most significant advantage compared to the standard phase-field approach in terms of computational cost and solution accuracy.

Slope stability calculation method for highwall mining with open-cut mines

Slope stability is a prominent problem for the efficient application and promotion of highwall mining technology, especially when mining residual coal under high and steep end-slope conditions. This study proposes the concept of target time pillar strength based on the required coal pillar service time. Creep tests were performed to measure the time-varying properties of coal shear strength parameters under different loads, and a time-varying function was established by regression. The highwall mining length is divided into three categories based on discontinuous structural plane theory, including goaf, yielding, and elastic zones, all of which are considered to have resistances against shear stress. The basal coal seam is prone to weakening owing to the weight of overlying strata, which may shift the slope failure mode from circular to sliding along the weak layer. Numerical modeling was used to study the influence of the bearing stress and target time strength on the development of the yielding zone at the coal pillar ribs. The coefficients of the three zones were determined, and the temporal and spatial evolution patterns of the shear strength parameters of the weak layer were acquired. A slope stability calculation method is proposed based on rigid body-limit equilibrium theory that can quantify the influence of highwall mining operations on slope stability, which is significant for popularizing highwall mining technology.

Shocks and Discontinuities Treatment in Multi-species Flows Using a Riemann Solver

The diversity of industrial configurations presenting a flow of mixtures of several species calls on researchers to develop a reliable, easily usable tool capable of treating this type of flow in the presence of an interface. The present work contributes to the numerical solution of multi-species equations in the presence of shocks and contact discontinuities. A shock capture-type method based on the separation of roe flux differences is associated with a two-parameter equation of state. The results presented here show that the model has the ability to correctly capture the present shocks and discontinuities and provide an accuracy compatible with the requirements zones of discontinuity existing in the flow.

Carbon-Based Nanoparticle-Filled Protective Coatings for Enhanced Damage Tolerance and Corrosion Resistance of Structural Weldment

AbstractWelded joints and surrounded material discontinuity zones in metallic infrastructures are highly vulnerable to severe corrosion-induced damage, which significantly shortens the service life...

Rainfall of the Sudan: Characteristics and Prediction

The paper highlights challenges facing the water sector at the global and national levels. The impacts of rainfall variability on the environment and socioeconomic conditions of the Sudan were discussed. Taking into consideration factors affecting rainfall of the country like the position of the Inter-Tropical Discontinuity Zone (ITDZ), the subtropical anticyclones and climate change. Recent studies showed that the areal annual averaged rainfall values of the country decreased markedly since early sixties. It varies from almost nil in the North to about 1500 mm at the extreme Southwest. The rain-producing clouds in tropical areas including Sudan belong to the vertically-developing group. The months of July –August-September were found to constitute the general rainy season of the Sudan. The paper also reviews rainfall prediction studies that use both the El Nino Southern Oscillation (ENSO) event and global Sea Surface Temperatures (SSTs) as predictors. However, more emphasis has been given on the ENSO event because of its global popularity as a rainfall-predictor. The paper concluded that Sudan’s rainfall can reasonably be predicted and more accuracy can be obtained with further studies.&#x0D; &#x0D;

Unprecedented acceleration of winter discharge of Upper Yenisei River inferred from tree rings

The Yenisei River is the largest contributor of freshwater and energy fluxes among all rivers draining to the Arctic Ocean. Modeling long-term variability of Eurasian runoff to the Arctic Ocean is complicated by the considerable variability of river discharge in time and space, and the monitoring constraints imposed by a sparse gauged-flow network and paucity of satellite data. We quantify tree growth response to river discharge at the upper reaches of the Yenisei River in Tuva, South Siberia. Two regression models built from eight tree-ring width chronologies of Larix sibirica are applied to reconstruct winter (Nov–Apr) discharge for the period 1784–1997 (214 years), and annual (Oct–Sept) discharge for the period 1701–2000 (300 years). The Nov–Apr model explains 52% of the discharge variance whereas Oct–Sept explains 26% for the calibration intervals 1927–1997 and 1927–2000, respectively. This new hydrological archive doubles the length of the instrumental discharge record at the Kyzyl gauge and resets the temporal background of discharge variability back to 1784. The reconstruction finds a remarkable 80% upsurge in winter flow over the last 25 years, which is unprecedented in the last 214 years. In contrast, annual discharge fluctuated normally for this system, with only a 7% increase over the last 25 years. Water balance modeling with CRU data manifests a significant discrepancy between decadal variability of the gauged flow and climate data after 1960. We discuss the impact on the baseflow rate change of both the accelerating permafrost warming in the discontinuous zone of South Siberia and widespread forest fires. The winter discharge accounts for only one third of the annual flow, yet the persistent 25 year upsurge is alarming. This trend is likely caused by Arctic Amplification, which can be further magnified by increased winter flow delivering significantly more fresh water to the Kara Sea during the cold season.

Analytical design of selected geotechnical solutions which protect civil structures from the effects of underground mining

This paper presents the authors' computational methods based on Knothe's theory. The methods enable the estimation of the reduction coefficient for effects which originate from mining operations performed via the application of a longitudinal structure which is sunk in to the ground. It could be, for example, a partition, which as a structural gap fulfils the function of an expansion grout, or via breaking the subsoil continuity (e.g. because of creating a peat-filled ditch or using a natural gap). Demonstrative calculations have been carried out in a few cases, i.a. to protect a structure situated in the vicinity of a planned tunnel. Additionally, some examples of the discontinuity zone which impact the obtained deformation values have been presented. The calculation method has been tested in case studies. The results of the calculations clearly show the positive influence of the applied geotechnical solutions on the minimisation of mining damage.

Satellite Observation of Spatio-temporal Variations in Nitrogen Dioxide over West Africa and Implications for Regional Air Quality.

Background.Nitrogen dioxide (NO2) is known to affect human health, causing heart and cardiovascular diseases, and it has been shown that locations with long term NO2 pollution recorded a high number of fatalities due to the COVID-19 pandemic. There are no ground stations monitoring emissions of NO2 over West Africa. The present study aimed to use satellite observations to examine pollutant trends over this region.Objective.To examine the trend of NO2 over the entire West Africa sub region in relationship to contributions to environmental emissions using satellite-derived data. This enables the assessment of West Africa regional air pollution hot spots in relationship to enhancing atmospheric factors. The results from this study will also be useful guidance for setting air quality standards for air pollution controls to minimize health hazards.Methods.The present study examined thirteen years of average monthly values of nitrogen dioxide (NO2) to determine the spatio-temporal variation of this pollutant over West Africa. Satellite data for NO2 between 2005 and 2017 were used to determine the variation in pollution levels over West Africa. Correlations between NO2 and meteorological variables (wind speed, rainfall and air temperature) were obtained to explain the influence of West African weather on the region's pollution accumulation.Results.The present study observed that NO2 concentrations varied from place to place and from season to season. Nitrogen dioxide concentrations during the dry season were higher (sometimes 200% higher) than values observed in the wet season which ranged between 0.5 and 6×1015 molec/cm2. Nitrogen dioxide north-south oscillation during the course of a year is largely controlled by the inter-tropical discontinuity (ITD) zone as high concentrations of NO2 are found in the vicinity of the ITD where wind speeds and horizontal vorticity approaches zero. Correlation analysis between NO2 and some atmospheric variables indicated NO2 concentrations are well influenced by atmospheric variables showing bipolar signals depending on the season. An increasing trend of NO2 was also found over selected cities of the region. This indicated that regional air quality is gradually deteriorating.Conclusions.The implications of worsening regional air quality were examined in the light of the prevailing COVID-19 pandemic. The dominant atmospheric factor determining pollution episodes in the region is the inter-tropical discontinuity line which marks the meeting point between the two wind regimes over the region. Densely populated areas are characteristically prone to elevated pollution and have experienced high fatalities during the COVID-19 pandemic.Competing Interests.The authors declare no competing financial interests.

Geological-structural mapping and geocronology of shear zones: A methodological proposal

The deformation registered in rocks in the field can be characterized based on the structures preserved in outcrops, which can related be to wide discontinuity zones named faults and shear zones. The geological-structural mapping and the geochronology of these tectonic structures are a topic of great interest not only for tectonic modeling but also for reconstruction of the geological evolution of the national territory. The methodology suggest for the analysis of faults and shear zones is based on eight steps, including: 1) definition of the geological context in which the structure was developed; 2) photointerpretation, image geoprocessing, and geological-structural mapping of the structural and lithological characteristics of the faults and shear zones; 3) petrographic analysis of field-oriented samples; 4) quantification of strain orientation and geometry through 3D finite strain analyses and quantification of non-coaxiliaty of deformation through vorticity analyses; 5) SEM-TEM-EBSD microanalysis; 6) quantification of the P-T conditions of deformation through phase-equilibria modeling or conventional geothermobarometry; 7) dating of syn-kinematic minerals phases and mylonitic rocks through Ar-Ar analyses, in order to determine the reactivation and deformation ages of the structure, respectively, as well as the implementation of the U-Pb technique in syn-kinematic calcite crystals developed in the fault planes; and 8) dating of geological elements adjacent to the structure, such as syn-kinematic intrusive bodies associated with the deformation event using zircon U-Pb dating, rocks hydrothermally altered through Ar-Ar method, and zircon and apatite fission-tracks dating of the blocks adjacent to the faults for determining exhumation ages.

Influence of discontinuity on groundwater flow and depressurisation plans in mine water pumping for an open cast lignite mine

Mining is the backbone of industrial development in many countries. During mining, groundwater levels generally cut across the mining and has led to flooding of the mine floors hindering the progress of mining and jeopardising the safety of the working force. Most of the mines adopt depressurisation schemes to pump out the excess water that causes mine flooding. The groundwater flow during mining is usually predicted using numerical models. In the present study, the discontinuities in the lignite deposit lying above a confined aquifer was modeled using Visual MODFLOW. The results showed an increased inflow flux by 2.64 times to the confined aquifer because of the presence of discontinuities, which in turn raised the piezometric levels in the confined aquifer resulting in more pumping. A rise of 3.3 m in water level was observed in the region of discontinuity, which needs to be pumped out for safe mining. The presence of discontinuity resulted in 30% additional pumping near the discontinuous zone for carrying out safe mining operations. When recharge was given to the semi-confined aquifer overlying the discontinuous lignite layer, the downward flux to upper confined aquifer increased by 4.62 times in comparison with the case without discontinuities. Particle tracking analysis was also performed to identify the source of additional flux in the zone of discontinuity.

Analytical design of selected geotechnical solutions which protect civil structures from the effects of underground mining

This paper presents the authors' computational methods based on Knothe's theory. The methods enable the estimation of the reduction coefficient for effects which originate from mining operations performed via the application of a longitudinal structure which is sunk in to the ground. It could be, for example, a partition, which as a structural gap fulfils the function of an expansion grout, or via breaking the subsoil continuity (e.g. because of creating a peat-filled ditch or using a natural gap). Demonstrative calculations have been carried out in a few cases, i.a. to protect a structure situated in the vicinity of a planned tunnel. Additionally, some examples of the discontinuity zone which impact the obtained deformation values have been presented. The calculation method has been tested in case studies. The results of the calculations clearly show the positive influence of the applied geotechnical solutions on the minimisation of mining damage.