Sand Distribution Research Articles

The Impact of Mining Waste and Biogas Digestate Addition on the Durability of Soil Aggregates

Waste management is one of the greatest contemporary challenges as the world strives for sustainable development. We set out to investigate the impact of mining waste (carboniferous rock) and organic waste (biogas digestate) on the physical properties of soils. The wastes were applied to Podzol, soil characterised by low chemical and physical quality with the particle size distribution (PSD) of loamy sand. The paper sets out to answer the question of whether a one-time application of mine and/or biogas digestate onto soil positively affects the durability of the soil structure and if the changes were permanent. For this purpose, we analysed soil texture, total organic carbon (TOC), water-stable aggregates and the mean weight diameter of water-stable aggregates (MWD). The combined addition of biogas digestate and the two types of waste improved the soil structure. The content of soil water-stable aggregates with dimensions 5–10 mm (A5–10) and 1–5 mm (A1–5) increased the MWD and the content of aggregates of diameters <1 mm (A<1) decreased. The effects of the experiment were permanent, as differences resulting from the soil treatments were still visible four years after the application. This shows that wastes, especially biogas digestate, could be successfully used in agriculture.

Identification of the Distribution and Volume of Iron Sand in the Gura Beach Area Using the Wenner-Schlumberger Configuration Geoelectric Method

The Naniura NRD300 HF tool has been used in research using the Wenner-Schlumberger configuration geoelectric method to determine the direction of iron sand distribution, the volume of iron sand, and the concentration of iron sand in the Gura beach area. The collected measurement results are then processed by the RES2DINV software into a 2 Dimension (2D) cross-section that shows the distribution values of the subsurface layer as shown by a color image. Once saved in (.xyz) format, the RES2DINV software results are processed in RockWork software to create pseudo-3D cross sections. The RES2DINV software's results show that line 1's resistivity value ranges from 39.6 to 1000 Ωm, whereas line 2's resistivity value ranges from 0.16 to 1.7 Ωm. These findings suggest that line 2 has a lower resistivity value than line 1 does. The volume of iron sand processed by RockWork software is 221,000 cubic meters for linek 2 and 273,000 cubic meters for line 1. The distribution of iron sand deposits in the study region is south to north, based on the volume of iron sand in line 1, which is bigger. A method used to determine the composition of the minerals present in a sample is called X-ray fluorescence (XRF). The results of analyzing the Fe content in line 2 are 55.01%, which is higher when compared to the Fe content in line 1, which is 40.5%.

Can Mud Deposits Indicate Inundation Extent of Paleotsunamis? Insights From Sediment‐Transport Simulations for Sand and Mud

AbstractField surveys following the 2011 Tohoku‐oki tsunami showed that mud tsunami deposits reached close to the tsunami inundation limit. However, the factors controlling the distribution of mud tsunami deposits remained unclear. We investigated these influencing factors by numerically simulating sand and mud transport after validating the tsunami inundation and distributions of sand and mud deposits during the 2011 Tohoku‐oki tsunami based on our sensitivity analysis of parameters used in the mud and sand sediment simulations. We have revealed that when the source of mud sediments is only on the seafloor (i.e., no terrestrial source), mud is deposited along less than 10% of the inundation distance. In contrast, if a terrestrial source of mud is present, mud deposits can cover 100% of the inundation distance. We have also revealed that mud sediments are not formed when topographic slopes are steep (1/20–1/500), irrespective of a terrestrial mud source, because flow stagnation does not occur. Therefore, to reproduce past inundation ranges of tsunamis from the distribution of mud deposits, two conditions are required: (a) regions with onshore mud sediments and (b) a gentle topographic slope (around 1/1,000) to allow for long‐time (more than 100 min) flow stagnation.

Identification of candidate paleotsunami deposit from sediment layers drilled in Seubadeh located in South Aceh of Indonesia

This study is conducted to identify prehistoric tsunami deposit (paleotsunami) in Seubadeh village, located in South Aceh Regency, Aceh province, Indonesia. Regional morphologic and seismic characteristics suggest that Seubadeh village is an area that stores tsunami deposits, both new tsunami deposits and prehistoric tsunami deposits. Therefore, in this study, the search for paleotsunami deposits was carried out in Seubadeh village. The tsunami deposit samples were taken at several points in Seubadeh village using a hand drill with a depth of more than 2 m. Sediment classification of the collected samples using Troels-Smith method shows a candidate layer of paleotsunami tsunami deposit was found between two clay deposits. The layer is dominated by plant roots and shell material. In addition, the sediment samples were sieved using a mesh to evaluate the grain size distribution of clay, silt and sand. The results of the grain size distribution and color evaluation of the respective layer are presented. The results of the analysis of the particle size distribution in the sample and the color of the sample indicate that there are 2 layers that show characteristics as a paleotsunami deposit, namely at a depth of about 170-200 cm and 280-292 cm. The paleotsunami deposit found will be further characterized by an emission spectroscopic technique.

Efficiency and mechanism of fire suppression through pneumatic sandblasting firefighting

With the increasing demand for improved firefighting performance, there is a need to explore innovative approaches. The study examines the injection of sand in pneumatic fire extinguishers to create a pneumatic sandblasting fire extinguisher that can enhance firefighting performance. A self-built pneumatic sandblasting fire extinguishing experimental platform was utilized to investigate the distribution of sand, efficiency of fire extinguishing, and mechanism of fire suppression. The study concludes that sand can be effectively accumulated at a distance of 1.5–2.34 m from the outlet, and the use of a pneumatic sandblasting fire extinguishing machine can considerably reduce the extinguishing time. The primary mechanism behind pneumatic sandblasting fire extinguishing involves the collaboration of airflow and sand. The research suggests exploring the use of sand in pneumatic fire extinguishers to improve firefighting performance in the early stage of forest fires.

Highlighting relationships between sand thicknesses, reservoir-seal pairs and paleobathymetry from a sequence stratigraphic perspective: An example from Tortonian Serravallian deposits, onshore Niger Delta Basin

The utilization of sequence stratigraphic concepts in identifying sands and their spatial continuity in distinct gross depositional settings is key, especially in frontier settings where data paucity is a common challenge. In the Baka field, onshore Niger Delta, detailed reservoir correlation guided by sequence stratigraphic framework analysis showed the distribution of sand and shale units constituting reservoir-seal pairs (RSP) correlatable across the field. Within the 3rd-order packages, it is observed that the lowstand systems tract (LST) and highstand systems tract (HST) contain more RSPs and thicker 4th- and 5th-order sands than the transgressive systems tract (TST). In terms of bathymetry, it is noted that irrespective of systems tracts, the RSP Index (RI) decreases from the proximal shallow/inner shelf settings to the more distal outer shelf areas. Amongst all three systems tracts, intervals interpreted as lowstand prograding complexes contain the best developed sands and highest RSP. Sand development within the LSTs has been controlled by a pronounced growth fault regime accompanied by high subsidence and sedimentation rates. This is linked to the basinward migration of the sands during prolonged sea-level fall, creating significant accommodation space for sand deposition. On the other hand, the TSTs known to mark periods of progressive sea-level rise and landward migration of sandy facies, show thinner sands enclosed in much thicker, laterally extensive, and better-preserved deeper marine shales. Interpreted seismic sections indicate intense growth faulting and channelization that influenced the syn- and post-depositional development of the sand packages across the field. The initial timing of deformation of sub-regional faults in this area coincides with periods of abrupt falls in sea level. This approach could be useful for predicting sand-prone areas in frontier fields as well as possible reservoir-seal parameters required for some aspects of petroleum system analysis and quick-look volume estimation.

Variables that contribute to tabia's high mechanical strength — A study using traditional residential flooring tabia from Zhejiang, China

Tabia has a long history of application in China, particularly as traditional residential flooring. In this work, we analyzed traditional residential flooring tabia samples from six residential flats in Zhejiang Province, China, to determine its composition and physical properties. We performed surface Leeb hardness test, compressive strength test, specific density and total porosity test, component composition test, sand and clay grain size distribution test, organic additives test, SEM, and XRD tests, capillary water absorption rate test, freeze-thaw damage test for the tabia samples. Results showed that these residential flooring tabia samples exhibit high compressive strength that can reach as high as 10 MPa. Furthermore, additional analysis determined that the high compressive strength is a function of the following criteria: 1) high density; 2) suitable mass ratio of sand, lime, and clay; 3) the appropriate sand particle size ratio; and 4) formation of hydrated calcium silicate (C-S-H). Moreover, sticky rice and egg white were also detected in the residential flooring tabia samples. The tabia's water absorption coefficient rate decreases with their density. The freeze-thaw resistance of tabia is related to many factors such as calcite content, density and porosity, microstructure. The data obtained from this study will provide guidance for conservators in the protection and restoration of tabia relics.

Presence of Phthalate Esters Used as Common Plasticisers in Maltese Shoreline Sand

DBP and DEHP are two of the most common plasticisers used in modern industries, which have aroused a major concern over their ubiquitous occurrence and hazardous environmental effects. This study presents the first data of phthalates occurrence and distribution in Maltese shoreline sand. DBP and DEHP occurrence was investigated in three busy and secluded beaches, respectively. Analytical determination involved quantifying DBP and DEHP from 75 samples using UPLC–MS/MS through triple repeatability. The concentrations ranged between 0.0095 and 0.07034 µg/g and <LOQ and 0.0977 µg/g for DBP and DEHP, respectively. Statistical analysis of the comparison of phthalates in different beaches demonstrated that the occurrence of DBP and DEHP in Maltese shoreline sand varies. The differences in the occurrence of phthalates were attributed to the beach topography and anthropogenic pressures. Analysis of the effects of anthropogenic activities on the occurrence of phthalates showed a positive association. Distribution analysis showed that DBP and DEHP exhibit an uneven distribution along the shoreline. Conversely, different distributions were observed at distances away from the sea. The uneven distributions observed were associated with anthropogenic activities, different chemodynamic properties and wave action. Cluster analysis was performed to prove the interactions between the phthalates concentrations and the characteristics of the beaches.

Assessment of a new pluviation system designed to prepare uniform samples of sand

In soil and soil-structure interaction laboratory experiments, the technique applied to prepare the sand deposit remarkably influence the performance of the system, including the stress–strain behavior. Air pluviation techniques represent the most suitable choice when a wide range of densities is required. This study presents the details of a simple and effective air pluviation system designed to be suitable for reconstituting small specimens of sand. Many of the previous studies have focused on traveling the pluviator in the horizontal direction only, without paying much attention to the vertical movement during pluviation. The apparatus described in this paper has the ability to overcome this issue by providing automatic lifting tools to the sand container while the thickness of the sand deposit builds up inside the collecting mold. To understand the influence of grain size distribution of sand on the achieved relative density (RD), three different samples of poorly graded sands were used in the experiments. Parametric studies, including the influence of the height of drop (HD) and deposition intensity (DI) on the relative density, were carried out on the three sand samples. It was observed that the range of obtained RDs depends mainly on the grain size distribution of the sand used. Three distinguished zones were observed in the RD-HD relationship, starting with a linear variation, followed by a nonlinear relationship until achieving a constant RD regardless of the increase of HD value. The uniformity of pluviated sand was assessed using a cone penetration test (CPT). Results of the CPT test showed that denser and more uniform samples could be obtained by raising the container up during the pluviation process.

Major advancement in oil and gas exploration of Jurassic channel sandstone in Well Bazhong 1HF in northern Sichuan Basin and its significance

In January 2023, Well Bazhong 1HF in the northern Sichuan Basin obtained high-yield industrial oil flow of over 100 cubic meters from the Jurassic channel sandstone for the first time, realizing a major breakthrough. In order to provide more support for further oil and gas exploration in this area, this paper analyzes the sedimentary and reservoir characteristics of the Jurassic Lianggaoshan Formation in Bazhong region of northern Sichuan Basin and their control factors based on the exploration achievements of Well Bazhong 1HF. Then, oil and gas reservoir characteristics and oil and gas sources are comparatively analyzed. Finally, the key technologies for the exploration of channel sandstone oil and gas with multi-stage vertical superimposition, lateral migration, thin reservoir and strong heterogeneity are researched and developed, and the next oil and gas exploration direction in the Lianggaoshan Formation of northern Sichuan Basin is pointed out. And the following research results are obtained. First, in the second member of Lianggaoshan Formation (“Liang 2 Member” for short) in Bazhong region, multi-stage underwater distributary sand bodies of delta front are developed with sandstone thickness of about 25 m and average porosity of 5.6%. The pore types are mainly primary intergranular pores and feldspar/debris intragranular dissolved pores, the pore throat structure is good, and the development of good-quality reservoirs is controlled by the sedimentary microfacies of underwater distributary channel. Second, the oil and gas reservoir of Liang 2 Member is a highly oil-bearing condensate gas reservoir/volatile oil reservoir, whose oil and gas is mainly sourced from the semi-deep lacustrine shale of Liang 1 and 2 Members. Third, channel sand bodies are superimposed and developed continuously in the upper part of Liang 2 and Liang 3 Members, and the source-reservoir configuration is good, with the characteristics of near-source hydrocarbon accumulation and overpressure hydrocarbon enrichment. Fourth, for the channel sandstones with multi-stage vertical superimposition, lateral migration, thin reservoir and strong heterogeneity, the reservoir prediction technology of “high-frequency sequence stratigraphy slice, seismic frequency decomposition and facies-constrained seismic waveform indication inversion” is developed to precisely characterize the “sweet spot” target of narrow channel sandstone, and the key fracturing technology of “dense cutting + composite temporary plugging + high-intensity proppant injection + imbibition and oil-increasing” is formed to realize the large-scale reconstruction of channel sandstone reservoir. In conclusion, the breakthrough of Well Bazhong 1HF in the exploration of Lianggaoshan Formation oil and gas in Bazhong region reveals the huge potential of Jurassic oil and gas exploration in the Sichuan Basin, and plays a positive role in promoting the exploration and development of the Jurassic channel sandstone oil and gas in the Sichuan Basin.

Geologic Causatives and Seismic Attributes Heterogeneities for Structural and Stratigraphic Interplays, Sitra Area, North Western Desert, Egypt

Sand-lithofacies distributions are a vital component of reservoir characterisation and the generation of successful reservoir models, particularly in thin reservoirs thickness. The integration between seismic attributes and conceptual geologic models is important to identify the sand distributions and reservoir geometries. The aim of this work is illustrating the uses of seismic data in revealing the structural and stratigraphic elements of two main reservoir units. It is important to identify and list the attributes, which can be involved in analysing the reservoirs and their degree of involvement in the characterisation of the hydrocarbon accumulation zones. The study was carried out for the reservoirs: Abu Roash C and Abu Roach E in Sitra oil and gas concession, which is located in the northern part of the Egyptian Western Desert. Four seismic attributes are used: 1- Coherence (Variance) 2- 3D Curvature attributes were used for resolving mainly the structural features and also the stratigraphic features 3- Instantaneous phase 4- Instantaneous frequency attributes were used mainly for resolving the stratigraphic features. Through the integration of selected seismic attributes with post-stack seismic data, reservoir distributions and architectures are accurately delineated for the Upper Cretaceous reservoir (Abu Roash ‘C’ and ‘E’). Five wells were used to match the results of the seismic attributes and establish the regional trends of reservoir parameters. The integration of wells data, conventional seismic interpretation and extracted the relevant seismic attributes help in reaching a robust geologic model for the reservoirs of interest. Stratigraphic and structural interpretation objectives based on extracting the seismic attributes for reservoir characterisation become more dominant, as they go deeper in seismic data, to derive more subsurface geologic data than traditional interpretation. 3D structure model of the concern area was established by interpreting the available seismic data as both reservoirs implicated by two fault trends: NW-SE and ENE-WSW. By the end a 3D geological model was defined based on the results of the conventional interpretation of the seismic and seismic attributes to reflect all structural and stratigraphic elements of the two reservoir units.

Numerical Investigation on the Compressive Behavior of Desert Sand-Based Backfill Material: Parametric Study.

As a key node in the promotion of the "Western Development" strategy in Xinjiang, China, the large-scale mining of coal resources is bound to cause a series of ecological and environmental problems, such as surface subsidence. Desert areas are widely distributed in Xinjiang, and from the perspective of reserves and sustainable development, it is crucial to fully utilize desert sand to make filling materials and predict its mechanical strength. In order to promote the application of High Water Backfill Material (HWBM) in mining engineering, a modified HWBM doped with Xinjiang Kumutage desert sand was used to prepare a desert sand-based backfill material, and its mechanical properties were tested. The discrete element particle flow software PFC3D is used to construct a three-dimensional numerical model of desert sand-based backfill material. The parameters such as sample sand content, porosity, desert sand particle size distribution, and model size are changed to study their impact on the bearing performance and scale effect of desert sand-based backfill materials. The results indicate that a higher content of desert sand can effectively improve the mechanical properties of HWBM specimens. The stress-strain relationship inverted by the numerical model is highly consistent with the measured results of desert sand-based backfill materials. Improving the particle size distribution of desert sand and reducing the porosity of filling materials within a certain range can significantly improve the bearing capacity of desert sand-based backfill materials. The influence of changing the range of microscopic parameters on the compressive strength of desert sand-based backfill materials was analyzed. This study provides a desert sand-based backfill material that meets the requirements of mine filling, and predicts its strength through numerical simulation.

Characterization and quantification of calcite distribution in MICP-treated sand using μ-XRF image processing technique

Characterization and quantification of calcite distribution in MICP-treated sand using μ-XRF image processing technique

Crosshole Ground‐Penetrating Radar in Clay‐Rich Quaternary Deposits: Toward Characterization of High‐Loss Media

AbstractKnowing the centimeter‐to meter‐scale distribution of sand in clayey deposits is important for determining the dominating water flow pathways. Borehole information has a high vertical resolution, on the millimeter‐ to centimeter‐scale, but provides poor lateral coverage. For highly heterogeneous deposits, such as glacial diamicts, this detailed borehole information may not be sufficient for creating reliable geological models. Crosshole ground‐penetrating radar (GPR) can provide information on the decimeter‐ to meter‐scale variation between boreholes, but has mainly been used in sandy environments. In this study, we investigate whether crosshole GPR can provide information on the structural relationship of diamicts and their material properties, such as water content, bulk density, and clay content. To achieve ground truth, we compare the crosshole GPR data with geological information from boreholes and an excavation at the field site. The GPR data was analyzed comprehensively using several radar wave attributes in both time‐ and frequency domain, describing the signal velocity, strength, and shape. We found small variations in signal velocity (between 0.06 and 0.07 m/ns) but large variations in both amplitude and shape (either order of magnitude variation or doubling/tripling of attribute values). We see that the GPR response from wetter and more clayey diamicts have both lower amplitudes and lower centroid frequencies than the response from their drier and sandier counterparts. Lastly, we find that the variation in amplitude and shape attributes is better correlated to the diamicts' material properties than the signal velocity.

A mathematical examination of the impact of mould transparency to infrared radiation on solidification during the investment casting process

Investment casting is a highly dynamic process during which multiple competing physical phenomena are at work. Those seeking to understand and simulate such processes computationally are confronted with a considerable task, balancing accuracy with efficiency. Approximations and models based on well-understood and documented fundamental physics are powerful tools in a modeller’s arsenal. Driven by observed discrepancies between experimental thermocouple measurements and simulation predictions of casting temperatures, this work explores the additional alloy cooling mechanism of mould transparency to infrared radiation, targeting a new mathematical approximation applicable in such situations. Direct attenuation, scattering from coarse sand, sand distribution in the mould and material temperatures play a role in the extent of radiation transparency that must be considered. From this model, estimation of the additional cooling rate resulting from expected mould transparency can be determined and applied as a corrective measure to computation fluid dynamics (CFD) simulation results that do not capture this phenomenon.

Different depositional models of wave-dominated shoreface deposits: An integrated process-oriented analysis (“Donghe sandstones” in Tarim Basin, China)

Wave-dominated shoreface sands are important marine clastic reservoirs. Their depositional characteristics and evolutionary history becomes one of the hot spots for oil and gas exploration and development. Limited by the traditional conception in typical depositional models, the geological contradictions on the late reservoir development of such type become increasingly prominent. The recognition of the different depositional models of wave-dominated shoreface deposits, therefore, becomes an alternative to solve the production problems in the developmental phase. Taking the “Donghe sandstones” of Tarim Basin as an example, the depositional characteristics and facies associations of wave-dominated shoreface deposits in different regions were analyzed on the basis of seismic, core, and logging data. Three types of different depositional models were proposed, namely the wave-dominated shoreface deposits of transgressive type with reworked delta background, wave-dominated shoreface deposits of transgressive–regressive type with shoal background, and wave-dominated shoreface deposits of transgressive type with gentle–slope background. On this basis, the differences of main controlling factors such as source supply and relative sea level change, hydrodynamic conditions, paleogeomorphology, their influences on wave-dominated shoreface deposits, and the evolution and distribution of shoreface sands under unique sedimentary mechanisms were further discussed. Limited by different depositional models, the “Donghe sandstones” showed an overall vertical retrogradational sedimentary sequence, and with similar distribution on the whole, it had distinct features in detail. In Donghe 1 area, it appeared to be with a morphological characteristic of both reworked original delta and latter shoreface deposits; in Hudson area, a sand-bodies superimposition and migration under model framework; and in Tazhong 4 area, a typical distribution of bar and beach sand-bodies. The different depositional models of wave-dominated shoreface deposits expand the explanation on various sub-environments from the point of formation mechanism, and guide the reservoir analysis and further oil and gas exploitation for such reservoirs.

Industrial neighborhoods in desert cities: Designing urban landscapes to reduce sandstorm effects in Mussafah

Labor housing projects in many Gulf countries are located in less favorable sites in the desert hinterland. They are characterized by grid-based compositions, simple facades, and block buildings positioned on the outskirts of cities. This development type was implemented in the industrial sector of Abu Dhabi, known as Mussafah. Gradually, this industrial area redeveloped its urban fabric by transforming many of its buildings into mixed-use structures with small gardens that provide open air spaces to the community and promote social interaction. Interventions from the community via introducing small garden stock increased the sense of belonging, improved the urban fabric, and reduced sand movement in the area. This is important in the Gulf region’s desert environment, which gives rise to sandstorms. This study evaluates the amount and distribution of sand around a selected group of buildings in the Mussafah area through experimental work. The methodology involves a coupled air and sand experiment in an environmental wind tunnel. The experiments have shown that adding a fence around the small gardens of the buildings in Mussafah reduced the sand pollution effects significantly.

Extended wet sieving method for determination of complete particle size distribution of general soils

The traditional standard wet sieving method uses steel sieves with aperture ≥0.063 mm and can only determine the particle size distribution (PSD) of gravel and sand in general soil. This paper extends the traditional method and presents an extended wet sieving method. The extended method uses both the steel sieves and the nylon filter cloth sieves. The apertures of the cloth sieves are smaller than 0.063 mm and equal 0.048 mm, 0.038 mm, 0.014 mm, 0.012 mm, 0.0063 mm, 0.004 mm, 0.003 mm, 0.002 mm, and 0.001 mm, respectively. The extended method uses five steps to separate the general soil into many material sub-groups of gravel, sand, silt and clay with known particle size ranges. The complete PSD of the general soil is then calculated from the dry masses of the individual material sub-groups. The extended method is demonstrated with a general soil of completely decomposed granite (CDG) in Hong Kong, China. The silt and clay materials with different particle size ranges are further examined, checked and verified using stereomicroscopic observation, physical and chemical property tests. The results further confirm the correctness of the extended wet sieving method.

Model-constrained and data-driven double-supervision acoustic impedance inversion

Seismic impedance inversion is an important technique for structure identification and reservoir prediction. Model-based and data-driven impedance inversion are the commonly used inversion methods. In practice, the geophysical inversion problem is essentially an ill-posedness problem, which means that there are many solutions corresponding to the same seismic data. Therefore, regularization schemes, which can provide stable and unique inversion results to some extent, have been introduced into the objective function as constrain terms. Among them, given a low-frequency initial impedance model is the most commonly used regularization method, which can provide a smooth and stable solution. However, this model-based inversion method relies heavily on the initial model and the inversion result is band limited to the effective frequency bandwidth of seismic data, which cannot effectively improve the seismic vertical resolution and is difficult to be applied to complex structural regions. Therefore, we propose a data-driven approach for high-resolution impedance inversion based on the bidirectional long short-term memory recurrent neural network, which regards seismic data as time-series rather than image-like patches. Compared with the model-based inversion method, the data-driven approach provides higher resolution inversion results, which demonstrates the effectiveness of the data-driven method for recovering the high-frequency components. However, judging from the inversion results for characterization the spatial distribution of thin-layer sands, the accuracy of high-frequency components is difficult to guarantee. Therefore, we add the model constraint to the objective function to overcome the shortages of relying only on the data-driven schemes. First, constructing the supervisor1 based on the bidirectional long short-term memory recurrent neural network, which provides the predicted impedance with higher resolution. Then, convolution constraint as supervisor2 is introduced into the objective function to guarantee the reliability and accuracy of the inversion results, which makes the synthetic seismic data obtained from the inversion result consistent with the input data. Finally, we test the proposed scheme based on the synthetic and field seismic data. Compared to model-based and purely data-driven impedance inversion methods, the proposed approach provides more accurate and reliable inversion results while with higher vertical resolution and better spatial continuity. The inversion results accurately characterize the spatial distribution relationship of thin sands. The model tests demonstrate that the model-constrained and data-driven impedance inversion scheme can effectively improve the thin-layer structure characterization based on the seismic data. Moreover, tests on the oil field data indicate the practicality and adaptability of the proposed method.

Evaluation of indicators for desertification risk assessment of Oleshky sands desertification based on Landsat data time series

Earth's surface monitoring allows the assessment of the dynamics and mapping of desertification indicators and is currently one of the priority research regions in remote sensing. In addition to the fact that desertification is a serious global threat to economic, social and food security, the risks of desertification have also become relevant for southern Ukraine. In recent years, climate change has become more and more noticeable in Ukraine. As a result, the time frames of the seasons are blurred, the boundaries of natural zones are shifting, abnormal values of meteorological indicators are increasingly observed, and the intensity of natural disasters is increasing. Since southern Ukraine is most vulnerable to adverse climate and landscape changes, including desertification, the article considered long-term landscape changes on the right bank of the Dnieper River in the Kherson region, mainly represented by sandy massifs of the Oleshky region, which are called the Oleshky Sands. Arid landscapes, which include the vast majority of Oleshky, are especially vulnerable to degradation processes, so space monitoring this territory is an urgent task given the current global climate changes. Within the framework of the presented study, the long-term dynamics of several indicators of desertification within the sandy arenas of the Oleshkovsky sands were mapped. Based on a series of multispectral space images obtained by Landsat satellites for the period 1986-2020 was considered. Spectral ranges characterize the key biophysical aspects of arid landscapes: the degree of soil moisture, vegetation density and sand distribution. Regression analysis was used to illustrate the dynamics of each indicator, which showed a general increase in each indicator over the experimental period. Furthermore, we determined the relationship between the values of the rise in desertification indicators and landscape changes that occurred in the research region, the classification of several images for different years was also carried out, and spatial and quantitative changes in the distribution of land cover classes were characterized.