Depth Of Strata Research Articles

Influence of a firm stratum on probabilistic slope stability analyses with spatially variable undrained soil strength

The influence of a firm stratum on the stability of a slope under undrained conditions has long been of interest to geotechnical investigators, which has been studied in a number of previously important works in relation to slope stability analyses without considering soil spatial variability. This paper proposes another look at such a problem in the context of probabilistic slope stability analyses considering soil spatial variability. Here, the random field (RF) is used to simulate the spatially variable undrained soil strength. It is found that under stationary RF and non-stationary RF with the soil strength at the top ground surface (su0) larger than 0, the depth of the firm stratum (Hf) has a significant influence on the mean and standard deviation of factor of safety (i.e., μ[FS] and σ[FS], respectively). By contrast, under non-stationary RF with su0 = 0, Hf has a slight influence on μ[FS], but its influence on σ[FS] is non-negligible. In addition, the autocorrelation distance is found to have an insignificant impact on the influential effect of Hf on μ[FS]. However, for σ[FS], this impact is not negligible. When the autocorrelation distance is smaller, the influence of Hf on σ[FS] would be more significant. Under non-stationary RF, the influence of Hf on σ[FS] would be slight if the autocorrelation distance is large enough. Furthermore, the impacts of slope ratio, su0, isotropic and anisotropic features on the influential effects of Hf are also investigated and discussed.

EVALUATION OF DEFORMATION PARAMETERS OF SILO FOUNDATIONS REINFORCED WITH SOIL-CEMENT ELEMENTS

The mandatory controlled criterion for steel silos is the limitation of foundation settlement and tilting, which is regulated by DBN V.2.6-221:2021. The threshold value of silo settlement is Smax,u = 150 mm. The most economical foundation solution is a large-sized slab on a natural base or a soil cushion. It is possible to stabilise the weak base by reinforcing it with vertical soil-cement elements (SCE). In Ukraine, most foundations have an underground gallery or silo floor. When the silos are first loaded, there is geodetic monitoring of the vertical settlement of the silo base and comparison of its data with the threshold values of settlement and tilting. The objective is to investigate the effect of limited-depth soil reinforcement on the stabilisation of the soil base and the average total foundation settlement. The task of the study is to create a methodology for predicting the impact of reinforcement with soil-cement elements on the parameters of the soil base general stiffness for a silo foundation. The research methods are geodetic monitoring of settlements around the perimeter of silo foundations during initial loading at four different elevators with different geological conditions. Thus, the predicting method of the impact while reinforcing with soil-cement elements on the general stiffness parameters of the soil base for the silo foundation was tested on the bases of silos for four elevators. These elevators represent different engineering and geological conditions. The proof of the methodology’s validity is the coincidence with the results of geodetic subsidence monitoring along the perimeter of silo foundations. According to the research results, it is possible to state that the reinforcement of the foundation base with vertical soil-cement elements allows for the effective stabilisation of soil parameters. We propose an evaluation method of the reinforcement effect with soil-cement elements in the form of the stabilisation coefficient for the soil base, kEi. We further prove the primary role of the soil-cement reinforcing elements operation and their length while stabilising the base. The base stiffness is stabilised at the compressible stratum depth and beyond the foundation boundaries. It is possible to use the method of reinforcement influence evaluation to determine the actual parameters of the stabilised soil base, n, according to geodetic monitoring data. The authors have studied the effect of limited depth reinforcement for stabilising the foundation. The research obtained the empirical dependence of the reinforcement required depth at given depth values for the base compressible layer. The authors proposed using the linearly deformed layer method, considering the operation of soil-cement elements as discrete soil reinforcement. The numerous experiments with the Finite Element Method confirm the high convergence of the calculated results with those obtained analytically. Keywords: foundation settlement, soil-cement element, geodetic monitoring, steel silo, foundation stiffness.

Hydrogeochemical Characteristics and Formation Processes of Ordovician Limestone Groundwater in Zhuozishan Coalfield, Northwest China

A comprehensive understanding of the characteristics and formation mechanisms of groundwater in mining areas is essential for the effective prevention of coal mine water and the rational management of groundwater resources. The objective of this study was to examine the hydrogeochemical characteristics and evolution of Ordovician groundwater in the Zhuozishan coal mine, located in the northwest region of China. A total of 34 groundwater samples were collected for hydrogeochemical analyses and the investigation of their evolution processes, with the aid of a piper trilinear diagram, a Gibbs diagram, and an ion ratio diagram. The results indicate that the concentration of sodium (Na+), potassium (K+), bicarbonate (HCO3−), chloride (Cl−), sulphate (SO42−), total dissolved solids (TDS), and pH increases from the recharge area to the discharge area, whereas the concentration of calcium (Ca2+) and magnesium (Mg2+) decreases. The hydrogeochemical characteristics of the runoff from Zhuozishan to Gongdeer coalfield and further southward display a notable north–south directional change. The groundwater process is primarily controlled by rock weathering action and cation exchange, with Na+ and K+ deriving primarily from cation exchange and only to a minor extent from halite dissolution. In conclusion, the northern part of the coalfield is characterised by a geological structure that creates a retention area with groundwater, resulting in an unordered runoff process with a complex formation mechanism. The middle region is devoid of geological constraints that would alter the flow direction, thus simplifying the process of groundwater formation. In contrast, the southern area experiences an increase in strata depth and fault blocking, which creates a retention zone, thereby rendering the groundwater formation process more complex. This research contributes to the effective management of groundwater resources in this coalfield and other mining sites.

RESULTS OF MONITORING THE SETTLEMENT OF SILO FOUNDATIONS REINFORCED WITH SOIL-CEMENT ELEMENTS

During the first cycle of loading and in the subsequent process of steel silos operation to store grain, special attention goes to the observation of base settlement under silo foundations and their tilting. Traditionally, silo settlement tends to be monitored by geodetic measurements. To analyse the results of monitoring for the silos base settlement, we used the linearity changing of the base stiffness approach. The base stiffness is the ratio of the average pressure p (in kPa) under the foundation sole to the average settlement S (in mm). This approach relies on the following assumption: in the process of silo loading, thus gradually increasing the average pressure under the sole of the foundation, the modulus of deformation of the base soil gradually decreases, and the deformability of the base increases until the stresses in the soil mass under the foundation do not exceed the values of the calculated resistance and the development of plastic deformations begins. For grain storage elevator silos 10.1–10.12 located in the Khmelnytskyi region, we obtained the ratio of the average pressure p (in kPa) under the foundation sole to the average settlement S (in mm) during the geodetic monitoring, and then, we used it to construct the stiffness graphs of the silo base. The base stiffness indicators of silos 10.2 and 10.3 most closely match the calculated base stiffness. The specified values of base stiffness exceeding the measured ones by 3–5% are probably due to the higher calculated mechanical characteristics of the base reinforced with soil-cement elements. The rigidity of the silo base and the average pressure in the base under the foundations calculated based on geodetic measurement data are independent random variables, as evidenced by the graphs of the rigidity of the silo base 10.1–10.12. The study of the correlation between the specified random variables is of practical interest. The obtained value of the sample correlation coefficient r = –0.4687 indicates a negative correlation between the samples of the average pressure p (in kPa) under the foundation sole and the stiffness of the base (p / S, kPa/mm). The existence of negative correlation dependence has a clear physical meaning, such as when the pressure on the base increases, its stiffness decreases while increasing the deformability of the base, as confirmed by the results of silo geodetic monitoring. The calculated stiffness of the base decreases with increasing pressure due to the involvement of a greater depth of the compressible stratum, and, accordingly, the calculated deformability of the base increases. To determine the physical and mechanical properties of the base soil, the generally accepted pressure range during the tests does not exceed 250 kPa. A priori, this pressure range corresponds to the elastic section of the soil deformation diagram and the gradual decrease in mechanical characteristics. The average stresses under the foundations of the studied silos did not exceed 125 kPa. Therefore, the proposed method makes it possible to obtain not only quantitative conclusions – the magnitude of base settlement, but also to analyse qualitative indicators related to the stiffness characteristics (р / S, kPa/mm) of the base and to assess its deformation indicators acceptability. Keywords: foundation settlement, geodetic monitoring, reinforced concrete foundation, steel silo, base stiffness.

Modelling and validation of liquefaction potential index of fine-grained soils using ensemble learning paradigms

This study explores the utilization of ensemble-based soft computing techniques for predicting the liquefaction potential of fine-grained soils. Generally, deterministic methods are used to assess the possibility of liquefactions. However, recent advancements have highlighted the implementation of machine learning techniques considering the diverse geotechnical characteristics for liquefaction susceptibility analysis. The current study predicts liquefaction potential index (LPI) of soils using five ensemble-based soft computing paradigms viz., decision tree, random forest, gradient boosting, AdaBoost, and XGBoost regressors. Various influential factors including stress parameters, depth of soil stratum, peak ground acceleration, earthquake magnitude, cyclic stress ratio, fine content, and SPT- N value, were used for estimating the LPI of soils. Experimental results of the employed models were assessed using multiple statistical indices. The results demonstrate that the employed XGBoost model achieved higher predictive accuracy with 99 % accuracy (based on R2 index) during the testing phase. Overall results exhibit that the employed XGBoost paradigm can be utilized as a viable alternative to empirical approaches, enabling an early assessment of liquefaction susceptibility in different engineering projects. This will expedite identification and evaluation of liquefaction hazards, allowing engineers to make more informed decisions.

HETERO- AND HOMOGENEOUS STATES OF HYDROCARBON FLUIDS IN THE EARTH’S INTERIOR (FROM THE DATA OF THE STUDY OF SYNTHETIC FLUID INCLUSIONS)

We performed the experimental study combined with in situ investigations of the phase composition and states of water-hydrocarbon fluids in synthetic inclusions in quartz. Thermometric data indicating of heterogeneous state of fluids at shallow, medium and large depths of oil and gas strata were determined. It has been shown that even at depths up to 10–12 km at temperatures of 250–290°С, water-hydrocarbon fluids with an oil content of 10 or more vol. % retain a heterogeneous state. Homogenization in such fluids, as have shown experimentally, is achieved at temperatures above 380–400°C only. However, such temperatures have not yet been detected in any of the real oil and gas basins of the world. The results of performed study allow predict the future discovery of homogenous oil and other hydrocarbon deposits.

The high-frequency sea-level change in the aftermath of the Marinoan snowball Earth: Evidence from the Doushantuo formation in the northern margin of the Yangtze Craton, South China

The rapid rise of glacioeustatic change is the most extreme paleoenvironment alteration in the aftermath of Snowball Earth. Although geologists conducted a lot of multi-subdiscipline research on this issue previously, there still exists the potential room for further discussions of the process in detail. For decades, the practice proved that the Fischer plot is a simple and robust tool to illustrate the fluctuations of accommodation patterns v.s. cycle sets or strata depth which could be interpreted as relative sea-level changes. This research simulates the Fischer plot to unravel the sea-level change in the aftermath of Marinoan glaciation by measuring the lower Ediacaran Doushantuo Formation in Shennongjia, South China. The result shows that 131 fifth-order cycles and nine third-order cycles help us propose a completed second-order cycle variation of ice melting-forced sea-level change, i.e., (1) early high-frequency and slow to rapid stepwise rising, and (2) followed by a stable decrease in the latter. In addition, the vertical sedimentary facies of the lower Doushantuo Formation display, in ascending order, (1) intertidal carbonate rock, (2) subtidal clastics with turbidite, and (3) intertidal lagoon fine clastics, indicating the process of the relative waxing and waning of sea-level. Such interpretation of the Fischer plot and the sedimentary facies’ vertical evolution is beneficial for studying the high-frequency sea-level change and paleogeographic reconstruction of post-Marinoan deglaciation.

Estimation of soil overburden thickness/depth of rock strata using geo-physical survey at Himalayan region


 
 
 Estimation of soil overburden and depth of competent strata for construction of infrastructures in hilly terrain is a challenging job for engineers. Modern technologies like Electrical Resistivity Survey (ERS) techniques with site geological mapping have been carried out at the ridge area near Palace, Gangtok. Two independent 2D-electrical resistivity surveys profile sections using hybrid Schlumberger-Wenner method were conducted along the ridge line trending in the North-South direction. The ERS profile sections were taken on both the slopes of the ridge along its eastern and western flanks. With the collective information from field and geo-technical data, a comparatively stable slope has been identified with respect to geological conditions in the present work, which focuses on the vulnerable slope failure with respect to slope direction, local geological condition, depth of competent strata, thickness of soil overburden, water saturation zones and resistivity of the materials. Diamond core drilling of 15meters each was carried out at both the flanks of the slope to understand the sub-surface strata and correlate it with resistivity data generated by ERS survey. The result indicates that Sandy/silty soil with flakes of mica having resistivity of 107 ohm-m and weathered mica schist having resistivity more than 300 ohm-m in the present study area. Geological mapping in 1:3000 scale was carried in the area demarcation with various litho-units and rock type. The area is characterized by medium grade metamorphic rock sequence represented in the area by mica schist having dip of foliations towards NE direction and three sets of joint planes. The geometry of the rock orientation and slope direction plays a vital role for determining the overall stability condition of the area. The present study will provide technical input for structural engineers to design the structures in such geological conditions. Further, the thickness of overburden estimated from ERS has been validated by drilling data.
 
 

Lugeon Test and Grouting Application Research Based on RQD of Grouting Sections

Rock quality designation (RQD) and permeability coefficient are important reference indexes for grouting application. Based on the readily available RQD, RQD is found to have no relationship with the depth of rock stratum, and a method for calculating the mean RQD (RQDm) of long stratum is proposed, which is applied to the calculation of RQD of grouting sections. Through Lugeon and grouting tests on the grouting sections, RQDm of the grouting sections is found to be directly related to the average permeability coefficient, permeability, and units of grouting per amount of rock mass. It is found that RQDm has a symmetrical relationship with permeability and grouting volume as well as a negative exponential correlation with unit grouting volume and average permeability coefficient. According to the curve of RQD varying with depth, the grouting amount at different depths can be obtained by using the fitting formula of unit grouting amount and RQDm.

Evaluation of Liquefaction Potential of Nagpur Region Using SPT Data: Field Assessment

Liquefaction is a complex, controversial but important topic in the Geotechnical engineering especially in earthquake sensitive regions. This secondary effect of earthquake causes severe damage to infrastructure. Nagpur is third largest and fastest growing and developing city in Maharashtra. The main aim of this study is to map the Nagpur city in the view of liquefaction potential occurrence and to make readily available data for further use and research. SPT-N based method is used for liquefaction assessment of soil encountered in the Nagpur region during investigation. The liquefaction potential is assessed regarding component of factor of safety (FS) along the depth of different soil stratum encountered during investigation. This liquefaction potential is evaluated at 56 representative sites in the city using Standard penetration tests (SPT) conducted and recorded in bore holes. Present study for computing liquefaction potential shows sensitivity in computing liquefaction against the SPT blow count and peak ground acceleration. For estimating Cyclic Resistance Ratio (CRR), the SPT-N value is corrected which indicates that the soil in the region is not identical at all locations, water table is of fluctuating nature and N values are varying according to soil properties but are mostly on higher sides which means that liquefaction potential is much low.

Suitability Evaluation of Three Tropical Pasture Species (Mulato II, Gatton Panic, and Rhodes Grass) for Cultivation under a Subtropical Climate of Australia

Exploring improved tropical forages is considered to be an important approach in delivering quality and consistent feed options for dairy cattle in tropical and subtropical regions. The present study aimed to study the suitability of three improved tropical grasses, Chloris gayana ‘Rhodes grass cv. Reclaimer’ (RR), Megathyrsus maximus ‘Gatton Panic’ (GP), and Brachiaria ruziziensis x B. decumbens x B. brizantha ‘Brachiaria Mulato II’ (BM) evaluating their carbon assimilation, canopy structure, herbage plant–part accumulation and quality parameters under irrigated conditions. An experiment was conducted at Gatton Research Dairy (27°54′ S, 152°33′ E, 89 m asl) Queensland, Australia, which has a predominantly subtropical climate. Photosynthesis biochemistry, canopy structure, herbage accumulation, plant part composition, and nutritive value were evaluated. Photosynthesis biochemistry differed between pasture species. Efficiency of CO2 assimilation was highest for GP and quantum efficiency was highest for BM. Pasture canopy structure was significantly affected by an interaction between pasture species and harvest. Forage biomass accumulation was highest in GP, while BM produced more leaf and less stem compared to both GP and RR. A greater leafy stratum and lower stemmy stratum depth were observed in the vertical sward structure of BM. Brachiaria Mulato II showed greater carbon partitioning to leaves, leaf: stem ratio, canopy, and leaf bulk density. It also demonstrated greater nutritive value (Total digestible nutrients (TDN), acid detergent fibre (ADF), neutral detergent fibre (NDF), neutral detergent insoluble protein (NDICP), Starch, nonfibre carbohydrates (NFC), metabolisable energy (ME), mineral profile (Mg, P, K, Fe, Zn) and dietary cation–anion difference (DCAD) for leaf, stem, and the whole plant. Greater quantum efficiency, leaf accumulation, and nutritive value of BM observed in the present study suggest BM as an attractive forage option for dairying that warrants further research in pasture-based systems in tropical and subtropical climates.

Distribution and biomass of gelatinous zooplankton in relation to an oxygen minimum zone and a shallow seamount in the Eastern Tropical North Atlantic Ocean

Physical and topographic characteristics can structure pelagic habitats and affect the plankton community composition. For example, oxygen minimum zones (OMZs) are expected to lead to a habitat compression for species with a high oxygen demand, while upwelling of nutrient-rich deep water at seamounts can locally increase productivity, especially in oligotrophic oceanic waters. Here we investigate the response of the gelatinous zooplankton (GZ) assemblage and biomass to differing oxygen conditions and to a seamount in the Eastern Tropical North Atlantic (ETNA) around the Cape Verde archipelago. A total of 16 GZ taxa (>1100 specimens) were found in the upper 1000 m with distinct species-specific differences, such as the absence of deep-living species Atolla wyvillei and Periphylla periphylla above the shallow seamount summit. Statistical analyses considering the most prominent groups, present at all stations, namely Beroe spp., hydromedusae (including Zygocanna vagans, Halicreas minimum, Colobonema sericeum, Solmissus spp.) and total GZ, showed a strong positive correlation of abundance with temperature for all groups, whereas oxygen had a weak negative correlation only with abundances of Beroe spp. and hydromedusae. To account for size differences between species, we established length-weight regressions and investigated total GZ biomass changes in relation to physical (OMZ) and topographic characteristics. The highest GZ biomass was observed at depths of lowest oxygen concentrations and deepest depth strata at the southeastern flank of the seamount and at two stations south of the Cape Verde archipelago. Our data suggest that, irrespective of their patchy distribution, GZ organisms are ubiquitous food web members of the ETNA, and their habitat includes waters of low oxygen content.

A python code for automatic construction of Fischer plots using proxy data

Fischer plots are widely used in paleoenvironmental research as graphic representations of sea- and lake-level changes through mapping linearly corrected variation of accumulative cycle thickness over cycle number or stratum depth. Some kinds of paleoenvironmental proxy data (especially subsurface data, such as natural gamma-ray logging data), which preserve continuous cyclic signals and have been largely collected, are potential materials for constructing Fischer Plots. However, it is laborious to count the cycles preserved in these proxy data manually and map Fischer plots with these cycles. In this paper, we introduce an original open-source Python code “PyFISCHERPLOT” for constructing Fischer Plots in batches utilizing paleoenvironmental proxy data series. The principle of constructing Fischer plots based on proxy data, the data processing and usage of the PyFISCHERPLOT code and the application cases of the code are presented. The code is compared with existing methods for constructing Fischer plots.

Bucket positioning and its load content during mining in inundated mineral deposit

In this paper, we discuss an issue of underwater mining and why modern mining equipment does not fit this purpose. Working in such complicated conditions often has an unsatisfying performance level. We analyzed the processes of mining materials that have not been preliminary dewatered. We also describe variations of positioning system and the importance of their use in underwater mining. A theoretical analysis of excavation process with a perforated bucket has been performed. We present a formula that allows assessing extent of bucket loading by parameters of the working face development. Another formula that allows determining the number of excavation cycles required to complete the bucket loading. A formula for parametric length of working face arc determining by the given stratum depth was introduced. Basing on the acquired formulae, we formulated another one that determines the number of excavation cycles necessary for complete face development for specified cutting parameters. An aggregated graph showing the dependency of the number of excavation cycles on peat shavings width and thickness variables. On the basis of the resulting graph, the best variant for the most complete bucket loading was chosen. In conclusion, we highlighted the peculiarities of underwater mining.

Multi-layer Gaussian Mixture Model algorithm and its application in lithology classification

Even in the same block, the difference in lithology distribution is small, but there is still a big difference in the distribution of the central wells and the edge wells in the block at the same level of depth. This is because we need to find data points of the same stratum depth instead of being disturbed by data points of horizontal depths. According to this problem, we propose two GMM algorithms based on EM: multi-layer GMM and two-layer GMM. The feature of multi-layer GMM is that even if there are edge wells far away from the exploratory well, this algorithm can still filter out data points that are not in the same formation depth through continuous averaging of initialization information in order to achieve a better effect of accurately predicting the lithology distribution of the stratum. Moreover, the robustness is more suitable for the general situation. In addition, in the blocks with relatively concentrated wells, we also propose a two-layer GMM method complementary. Compared with the multi-layer structure, due to the parallel structure, it is faster but less robust. The simulation results show that the multi-layer GMM algorithm proposed in this paper is compared with the multi-resolution clustering method based on graph theory, single-layer GMM and double-layer GMM. This algorithm achieves a better clustering effect than other methods.

Influence of complex geological conditions on the in situ stress field of the SK Hydropower Station in Pakistan

The Suki–Kinari hydropower station is situated in a landform with high mountains and deep valleys in northwest Pakistan. Affected by some geological conditions such as topography and faults, the in situ stress distribution of the project area is highly complex. To determine the in situ stress associated with this project, hydraulic fracturing in situ stress tests are conducted in four representative boreholes. Generally, the relation of the three principal stresses is σ H > σ z > σ h . However, the measured stress directions associated with the headrace tunnel and the powerhouse area are clearly different. The direction of the maximum horizontal principal stress of the headrace tunnel is NNE–NEE, whereas that of the underground powerhouse area is NNW–NWW. To identify the mechanism responsible for this difference, the present study simulates the stress field in the project area based on the three-dimensional finite element regression analysis method. Two theories are proposed on the basis of the numerical simulation results. On the one hand, the direction of the maximum horizontal principal stress in the rock mass above the valley elevation is controlled mainly by topography. On the other hand, the fault will disturb the stress field, causing noticeable changes in the stress direction and value of the fault-affected zone. By comparing the characteristics of the stress direction distribution at three elevations, the direction of maximum horizontal principal stress of the shallow strata is determined to be affected mainly by the topography and faults, and topography may be the most important factor. Moreover, with an increase in strata depth, the influence of the topography and faults on the stress direction decreases gradually. After reaching a particular strata depth, the direction of maximum horizontal principal stress tends to be the same as that of the regional tectonic stress, i.e., NNE.

Variation of Ground Temperature along the Stratum Depth in Ice-rich Tundra of Hinggan Mountains Region, NE China

A pile foundation in a permafrost region is in a negative-temperature environment, so concrete is affected by the negative temperature of the surrounding soil. It not only affects the formation of concrete strength but also leads to engineering quality accidents in serious cases. With the support of the two permafrost bridge projects of the national highway from Beijing to Mohe in the Greater Khingan Mountains region, a systematic remote dynamic monitoring method for ground temperature in ice-rich tundra is proposed. Based on the actual measurement of temperature at different strata depths and the comprehensive consideration of surface temperature, terrestrial heat flux and other parameters, the ground temperature profile evolution in relation to depth in Greater Khingan was established. The theoretical ground temperature profile curve is similar to the measured profile. The results show that the variation trends of ground temperatures in relation to the strata depth at different monitoring sites is similar, and all show seasonal variation: From June to November, the ground temperature at different depths tends to be constant. From December to May, the ground temperature at any depth within the range of 0 to 5.5 m follows the curve of the cosine function. Below 5.5 m, the earth temperature no longer varies with depth. The research results can be used as reference for pile foundation construction in a negative-temperature environment in ice-rich tundra.

Settlement Computation of Homogeneous Base

Purpose of reseach. This article proposes the development of a new methodology for determining the settlement of a homogeneous foundation base on the basis of the layer-by-layer summation method, which reduces the amount of calculations performed.Methods. The boundary of the compressible stratum can be determined graphically from the condition that the additional stresses are equal to half the natural stresses. Knowing the value of the depth of the compressible stratum, we can determine the total value of the coefficients included in the well-known formula for calculating the settlement of the base by the method of layer-by-layer summation. Having determined the value of the specified coefficient in the layer located directly below the base of the foundation, we introduce the coefficient Kα, which reflects the proportion of sediment in the layer under consideration.Results. The application of the developed coefficient Kα allows determining the base settlement by calculating the deformations of one soil layer located directly below the base of the foundation, which greatly simplifies the design of underground structures. As an example, we consider a foundation, the average pressure under the sole of which is 1200 kPa, the laying depth d = 2 m, the base is homogeneous with a deformation modulus of 20 MPa and a specific gravity of γ = 18 kN / m3. The settlement of the building-basement system was calculated by the method of layer-bylayer summation and the critical analysis of the results was performed. When calculating precipitation by the method of layer-by-layer summation according to the known formulas given in SP 22.13330. 2016 “Foundations of buildings and structures”, it was obtained a draft value of 9 cm. When calculating the base deformations according to the proposed method, the boundary of the compressible thickness Hc = 5.7 m was graphically determined. The coefficient value was 0.203, and the draft was 9 cm.Conclusion. The settlement values determined in accordance with current regulatory documents and the developed methodology are the same, which allows us to conclude that the proposed method has a sufficient degree of reliability and can significantly facilitate the process of determining the deformations of the base of buildings and structures.

РОЗПОДІЛ РТУТІ У ВУГІЛЬНОМУ ПЛАСТІ C7Н ПОЛЯ ШАХТИ «ПАВЛОГРАДСЬКА»

Purpose. Investigation of regularities of mercury distribution in coal of formation c7n of the Pavlogradska mine field. Methodology. Method of atomic absorption analysis of furrow samples of wells. Processing of geochemical and structural-geological data by methods of mathematical statistics using Excel 2016 and Statistica 6.0. The computer program Surfer was used to build maps/ Results. In article considered the distribution of mercury in the coal seam c7н of the Pavlohradska mine field of the Pavlohrad-Petropavlivka geological and industrial district of Donbas. As a result of the study, a map of isoconcentrates and a map of the regional component of mercury content in the coal of the seam were constructed and analyzed. Correlation coefficients between mercury concentration and formation morphological parameters and coal sulfur were calculated. The regression equations between this element and the ash content of coal are also established, which will allow predicting their concentration in the main working coal seams of the geological-industrial area relative to the values of coal ash content. The nature of sulfur distribution is established and the weighted average concentrations and the main descriptive statistics of this element are calculated. Scientific novelty. Peculiarities and regularities of mercury accumulation in coal of formation c7n are revealed. Practical significance. The constructed maps and established correlations are the factual basis for long-term forecasting of mercury concentrations in extracted raw materials and adjustment of technological schemes of coal beneficiation. Keywords: mercury, mine, coal height, ash content, stratum depth, sulfur content, regression equation, correlation coefficient.

Stability of a Roadway below a Coal Seam under Dynamic Pressure: A Case Study of the 11123 Floor Gas Drainage Roadway of a Mine in Huainan, China

Coal and gas outburst is an important risk faced by coal seam mining in the Huainan region of China. In order to control gas outburst, the gas is predrained by digging a floor gas drainage roadway. To study deformation due to dynamic pressure, the failure characteristics of the floor, and their effect on the stability of the floor gas drainage roadway, a comprehensive monitoring method combining Brillouin optical time‐domain reflectometry‐ (BOTDR‐) distributed fiber optics and self‐potential exploration was adopted. Dynamic data monitoring of the rock strata between the 11123 working face floor and the floor gas drainage roadway of a mine in Huainan was carried out. The field data obtained showed that, when stabilized by rock bolts and other fixed components in the surrounding rock mass of the floor gas drainage roadway, under the influence of mining, the area of concentrated stress appeared at a depth of 20.7 m, when cracks eventually formed, but the overall structural stability of the surrounding rock mass remained good. The stress distribution and crack evolution of the bottom plate under the influence of dynamic pressure showed spatiotemporal characteristics. Of these, the effect of the lead support stress was 107.48 m, and the range of effect of the hysteresis stress was 34.42 m. When the working face mining position arrives and is far from the monitoring station, the failure depth of floor rock stratum shows the following rule: unchanged in the early stage, deepened continuously in the middle stage, and finally remained stable. It takes about eight days for the dynamic adjustment of this process to finally stabilize. The results of this study can provide guidance for devising suitable procedures for carrying out intelligent green safety mining and for warning about the hazards of roadway damage.