Silt Layers Research Articles

Analisa Model Struktur Geologi Untuk Menduga Air Tanah Dengan Menggunakan Metode Geolistrik

Gondanglegi Kulon Village is located in Gondanglegi District, Malang Regency, the research location is in the Muhammadiyah Entrepreneur Islamic Boarding School area. From the results of information from local villagers, it was explained that in the study area there was no shallow groundwater found. This is also reinforced by the fact that there are no wells in the settlements of the residents around the Entrepreneur Muhammadiyah Islamic Boarding School, so that practically no residents use wells to fulfill clean water, they still depend on river water or PDAM services which are relatively expensive and continuous. still below expectations. As a center for religious education, Islamic boarding schools continue to develop supporting facilities. One of the most needed facilities is the availability of clean water. Quantitatively, the supply from the PDAM is not sufficient and the operational costs borne by the manager are too high. The use of groundwater is a solution that can be used to meet the needs of clean water at the research location. Therefore we need a technology to identify the point of exploration, the technology used in this research is geoelectric resistivity. By using the resistivity geoelectric method, it is expected to know the rock structure at the research location and see the potential for deep groundwater. Thus, the hope that in the future the Entrepreneur Muhammadiyah Islamic Boarding School (PPEM) will no longer depend on water raw materials from the PDAM, so the hope is that daily operational costs related to clean water needs can be minimized. From the results of the analysis and discussion, 2 (two) points of drilling recommendations were obtained, but with technical and non-technical considerations, exploration was suggested at point 3 with a potential of 4.2423 L / sec. Where at this location is a rock lithological arrangement consisting of a top soil layer, a clay layer, a tuff layer, a sandy silt layer, a sand layer and a gravel layer.

Prediction of Spatial Distribution of Organic Carbon in Lower Brahmaputra Active Floodplain Soils of Bangladesh

Soil acts as a large reservoir of Organic Carbon (OC) but the amount varies significantly with space and time. Thus, soil analysis and interpretation of spatial variability of Soil Organic Carbon (SOC) are keys to site-specific management. The study aimed to characterize the spatial variability of SOC in an active floodplain. Soil samples were collected in three major landform categories (natural levee, back slope, marsh land) from the lower Brahmaputra River floodplain and then analyzed for SOC measurement in the laboratory. The measured data were then analyzed for spatial variability interpretation using descriptive statistics and geo-statistical analysis. The study found that the amount of SOC varies with landform variation, soil texture and distance between sample points. The topsoil of marsh land has the highest (1.41%), back slope holds a moderate amount (1.15%) and the natural levee has the lowest (0.75%) amount of SOC. The amount of clay particles at the top layer was found to be positively correlated to the SOC whereas in the same layer of sand and silt showed a negative correlation. The geo-statistical analysis illustrated the nugget effect. Low (<1%) SOC is commonly found in the agricultural soils of Bangladesh which was corroborated in this study; moderate (1.1%) SOC was found in the floodplain. This study aimed to provide an insight into spatial variability to assist in predicting SOC in the active floodplain; consequently, the interpretation of spatial variability analysis can be implemented for site specific management strategies and to calculate carbon stock in floodplain soils.
 The Dhaka University Journal of Earth and Environmental Sciences, Vol. 8(2), 2019, P 33-40

The role of ecotones in the dehalogenation of chloroethenes in alluvial fan aquifers.

The presence of ecotones in transition zones between geological strata (e.g. layers of gravel and sand interbedded with layers of silt in distal alluvial fan deposits) in aquifers plays a significant role in regulating the flux of matter and energy between compartments. Ecotones are characterised by steep physicochemical and biological gradients and considerable biological diversity. However, the link between organic pollutants and degradation potential in ecotones has scarcely been studied. The aim of this study is to relate the presence of ecotones with the dehalogenation of chloroethenes. A field site was selected where chloroethene contamination occurs in a granular aquifer with geological heterogeneities. The site is monitored by multilevel and conventional wells. Groundwater samples were analysed by chemical, isotopic, and molecular techniques. The main results were as follows: (1) two ecotones were characterised in the source area, one in the upper part of the aquifer and the second in the transition zone to the bottom aquitard, where the aged pool is located; (2) the ecotone located in the transition zone to the bottom aquitard has greater microbial diversity, due to higher geological heterogeneities; (3) both ecotones show the reductive dehalogenation of perchloroethylene and trichloroethylene; and (4) these ecotones are the main zones of the reductive dehalogenation of the pollutants, given the more reductive conditions at the centre of the plume. These findings suggest that ecotones are responsible for natural attenuation, where oxic conditions prevailed at the aquifer and bioremediation strategies could be applied more effectively in these zones to promote complete reductive dehalogenation.

Study on early warning of rapid sinking of large land caisson in silt layer

Large caisson constructed in the soft soil layer is prone to rapid sinking during the sinking process. Rapid sinking is often accompanied by partial sinking, which affects construction safety and subsequent construction. There is no relevant early warning mechanism for early warning of rapid sinking. This paper takes the sinking construction of a large land caisson in a deep silt layer as an example, analysis the rapid sinking mechanism through the earth pressure and settlement rate of the sinking process, and proposes a rapid sinking early warning mechanism. Before the rapid sinking, the soil at the edge of the blade feet is partially plastic damaged, and the earth pressure decreases continuously after reaching its limit value; The strain softening of the overlying soft soil layer, the rapid reduction of side friction and the instability of open caisson caused by soil gushing after the plastic zone connecting are the important reasons for the rapid sinking. The rapid sinking process is divided into “sagging section, starting section, instability section and stable section”. The earth pressure early warning mechanism is the continuous decrease of the earth pressure at the blade feet. When the sinking rate exceeds the threshold value for two hours, it is regarded as the early warning mechanism of sinking rate. Using this dual control mechanism of end earth pressure and sinking rate can effectively warn the rapid sinking of the caisson.

СОСТОЯНИЕ ЭКОСИСТЕМ ВОСТОЧНОГО И ЗАПАДНОГО БАССЕЙНОВ САКСКОГО ОЗЕРА (РЕСПУБЛИКА КРЫМ)

Sakskoe Lake is the most thoroughly studied water body in Crimea. Its therapeutic mud and brine are exploited by balneological treatment methods. During the two centuries, when the lake was used by humans, it was subdivided into seven water bodies by dams, with two of these bodies (Eastern and Western) being now utilized for medical purposes, and the other five being protective. The Eastern (currently exploited) basin is now used to produce therapeutic mud and brine. The bottoms of the saline basins are covered by sediments: an upper layer of black silt, which is underlain by gray, steel-gray, occasionally bluish silt, which is used as therapeutic mud. The lake is fed by surface and groundwaters. Retaining dams and flood embankments erected in nearby ravines preclude desalination of the lake with flood and rain waters. Seawater is pumped to the lake through channels to preclude its drying. A quay is now actively constructed around the lake and will likely notably affect its hydrological and ecological conditions. The aim of the present study was the comparative analysis of the chemical and physical characteristics of the Eastern and Western basins of the Sakskoe Lake at the period of intensive building activity on their coasts at the summer period of 2019. Brine samples were collected at two tested sites in each of the lakes. Water salinity was measured by a PAL-06S LTA GO (Japan) refractometer and was expressed in ‰. The pH and Eh of the waters and oxygen dissolved in them were determined in the laboratory by an Expert-001 (Econix-Expert Moexa CoLtd, Russia) analyzer, with the use of appropriate Volta (Russia) selective electrodes. Ions concentration was determined spectrophotometrically and by atomic absorption method. Various living stages of Artemia populations in two water bodies were studied according the standard microscopic methods. The obtained results demonstrated, that the total content of the cations in the brine of the Western basin was in 1,5-fold higher as compared with the data of the brine in the Eastern basin (108,4 and 71,2 g/l respectively). The values were directly correlated with the high salinity of the Western basin brine. The identical trend was shown for the anions concentration, which was significantly greatly in the Western basin related to Eastern one (193,14 and 125,41 g/l correspondingly), which was connected with the different hydrogeological conditions of the formation of the ecosystems of the tested water bodies. At the other hand, pH, salinity and Eh of the brine in the Eastern basin were lower than in the brine of the Western basin, while the concentration of dissolved oxygen was higher. In the brine of the Eastern basin of the lake all living stages of Artemia, including cysts, nauplia and adults were found, while in the Western basin only cysts were shown. Therefore, according the obtained results we could suggest, that anthropogenic processes which were taken place on the coasts of the Sakskoe Lake accompanied with the intensive building activity did not influence on the lake ecosystem. The further monitoring studies including the testing of the ions concentrations in the brine of two basins, Artemia populations state are required for the understanding the changes of the both ecosystems and the possible reasons of their changes. It is important for development of the optimization of the management of Sakskoe lake and its resources exploitation.

Modeling Saline Mudflat and Aquifer Deformation Synthesizing Environmental and Hydrogeological Factors Using Time-Series InSAR

Clarifying the surface and subsurface deformation is important for protecting the infrastructures attached to the ground and reasonably exploiting the underground resources. This article presents an improved deformation model combining environmental factors (i.e., precipitation and temperature) with hydrogeological parameters to separate the saline-soil deformation from the aquifer deformation over Qarhan Salt Lake, China. First, the vertical ground deformation was derived by 119 ascending and 113 descending synthetic aperture radar images of Sentinel-1A collected from July 2015 to May 2020. Subsequently, we estimated the deformation components derived from temperature, precipitation, seasonal oscillation, magnitude, and decay coefficient of the hydrodynamic function by the proposed deformation model. The estimated deformation and decay coefficient maps pinpoint the existing and previously unknown faults. Next, we compared our proposed prototype with the sinusoidal and exponentially decaying model to present the reliability and efficiency in separating the deformation components and estimating the decay coefficient. Finally, we collected the stratigraphic data from 50 drilling wells to validate our model results by simulating the cumulative silt and clay layers (aquitard) thickness utilizing the Ordinary Kriging interpolation method. Findings show that by quantifying the aquitard thickness in the drilling wells, there is a strong relationship in the spatial distribution between cumulative thickness and the decay coefficient. The results suggested that both the decay coefficient and the aquitard-layer thickness can be used as the vital parameters to partition hydrogeological units, which provides an opportunity to detect and mitigate the potential geological hazards in the saline mudflat.

ДИНАМІКА МУТНОСТІ РІЧКОВОЇ ВОДИ ЛІВОБЕРЕЖНИХ ПРИТОК ДНІПРА (НА ПРИКЛАДІ СУМСЬКОЇ ОБЛАСТІ)

The article is devoted to the study of sediment runoff, especially one of the characteristics that reflects erosion processes in the catchment area, water turbidity using the example of the rivers of the Sumy region. The main purpose of the article is the spatial and temporal analysis of the turbidity indicators of the rivers of the Sumy region (left-bank tributaries of the Dnieper). The article highlights information on the sediment runoff of the rivers in the region for the entire period of observations, describes modern own studies of the turbidity of river water and establishes the features of the formation of sediment runoff in the rivers of the region. It was found that the indicators of turbidity of river water grow in the direction from north to south of the study area, in the zone of mixed forests are minimal, and in the forest-steppe – maximum; high values of the average turbidity index characteristic of small rivers in the region, аmong the average rivers, the maximum values were recorded for the Sula and Vorskla rivers; during floods, turbidity values are maximum, and during low water periods, they are minimal; there is a tendency to an increase in the indicators of maximum and average turbidity of river water. Particular attention is paid to the influence of river regulation on turbidity indicators. It was found that the deceleration of water exchange is facilitated by the accumulation of sediments in the channel above the dam (high indicators of the thickness of the silt layer), and also below the dam (the creation of a channel island, probably due to the uneven throughput of the dam’s gate valves, which creates a different flow rate from the right and left banks). Decreased flow velocity, increased water turbidity and, as a consequence, siltation, deterioration of river water quality (appearance of swamp odor, decrease in transparency, color change) leads to changes in the species composition of aquatic organisms, extinction of river species and the appearance of atypical river species, overgrowth. In their conclusions, the authors argue that sediment runoff is formed mainly due to washout from the surface of the catchment area, high turbidity indicators in rivers whose basin is more prone to erosion, where the indicators of plowing of the basin surface are maximum, water protection zones and coastal protective belts are destroyed, but when studying the turbidity of river water it is necessary take into account additional factors.

Microfacies and C/O-isotopes in lacustrine dolomites reflect variable environmental conditions in the Germanic Basin (Arnstadt Formation, Upper Triassic)

Abstract The conditions in ancient evaporative environments conducive to authigenic carbonate (especially dolomite [CaMg(CO3)2]) formation are still insufficiently understood. Insights from microfacies analysis can help to constrain the conditions in these environments. We provide a brief overview of the microfacies association and carbon and oxygen isotope compositions of dolomite beds intercalated in a claystone-rich succession from the Norian Arnstadt Formation in Thuringia and Lower Saxony (Germany) in order to gain further insight into the depositional conditions and processes leading to the formation of authigenic Mg/Ca-carbonates in the Germanic Basin. The studied intervals are ascribed to lacustrine, partially evaporitic conditions, while the sedimentary structures were not obliterated by recrystallization. The microfacies of the dolomites is diverse, showing homogeneous micrite, mudclasts, lamination, and peloidal structures, and reflects a shallow to deeper water (below wave base) and episodically evaporative environment. The dolomites exhibit oxygen isotope values (δ18O) in the range from −5.21 to −0.36‰ VPDB and, hence, only represent a weak meteoric influence, suggesting that the authigenic carbonate generally formed under evaporative conditions. Carbon isotope values (δ13C) in the range of −4.28 to 1.39‰ VPDB indicate a small contribution of remineralized organic carbon, mainly in sediments that were presumably deposited in deeper water or under brackish conditions. Sedimentary structures, such as lamination with graded silt layers, reworked mudclasts embedded in a fine dolomicrite matrix, and peloids showing plastic deformation, indicate that the sediment was still unlithified. These observations would be consistent with an authigenic formation of Mg/Ca-carbonates directly from the lake water, and their deposition under variable conditions in a large playa-lake/perennial lake system.

Reliability of CPT measurements in sand – influence of spacing

Geotechnical methods, such as cone penetration tests (CPTs), standard penetration tests (SPTs) and seismic cone penetration tests (sCPTs), are widely used to characterise the in situ properties of soil. In studies where more than one in situ method in close spacing is used, it is important for geotechnical engineers to balance between soil heterogeneity and the artefacts of disturbed testing zones. The same applies if detailed information about the subsoil is required and one in situ method is used in close spacing. There is no consensus on how to define the minimum spacing between testing zones and no study on the effect of disturbance caused by in situ tests. In this study, 33 CPTs were performed in natural sediments in northern Germany and a spacing threshold was defined at which cone resistance is affected by soil disturbance from previously performed CPTs. The CPTs were performed sequentially by successively refining the grid spacing, starting with a spacing of 119 cone diameters between CPTs, to a fine grid spacing of seven cone diameters. The cone resistance is affected by previous CPT measurements below a spacing threshold of 24 cone diameters in medium-dense sands. Silt and clay layers showed no reduction in the cone resistance for the minimum grid spacing of seven cone diameters.

Field performance of the radon-deficit technique to detect and delineate a complex DNAPL accumulation in a multi-layer soil profile.

The performance of the radon (222Rn)-deficit technique has been evaluated at a site in which a complex DNAPL mixture (mostly hexachlorocyclohexanes and chlorobenzenes) has contaminated all four layers (from top to bottom: anthropic backfill, silt, gravel and marl) of the soil profile. Soil gas samples were collected at two depths (0.8m and 1.7m) in seven field campaigns and a total of 186 222Rn measurements were performed with a pulse ionization detector. A statistical assessment of the influence of field parameters on the results revealed that sampling depth and atmospheric pressure did not significantly affect the measurements, while the location of the sampling point and ground-level atmospheric temperature did. In order to remove the bias introduced by varying field temperatures and hence to be able to jointly interpret 222Rn measurements from different campaigns, 222Rn concentrations were rescaled by dividing each individual datum by the mean 222Rn concentration of its corresponding field campaign. Rescaled 222Rn maps showed a high spatial correlation between 222Rn minima and maximum contaminant concentrations in the top two layers of the soil profile, successfully delineating the surface trace of DNAPL accumulation in the anthropic backfill and silt layers. However, no correlation could be established between 222Rn concentrations in superficial soil gas and contaminant concentration in the deeper two layers of the soil profile. These results indicate that the 222Rn-deficit technique is unable to describe the vertical variation of contamination processes with depth but can be an effective tool for the preliminary characterization of sites in which the distance between the inlet point of the sampling probe and the contaminant accumulation falls within the effective diffusion length of 222Rn in the affected soil profile.

Application of Grain Size Analysis for Saturated Hydraulic Conductivity Assessment of Bed Silts along Komárňanský Channel – Žitný Ostrov

The objective of this study is the evaluation of permeability of the bed silts located along the Komárňanský channel of the Žitný ostrov, Slovakia. Komárňanský channel is the largest one from three main channels at the Žitný ostrov area – the flat lowland with channel network. The bed silt permeability is expressed by value of saturated hydraulic conductivity. This parameter is one of the key inputs for estimating solute and water movement between surface water channel and surrounding groundwater in the scope of their interaction at this area. The bed silts were obtained by two ways, as disturbed samples and as undisturbed samples. In this study we deal with disturbed samples extracted from the Komárňanský channel and for that reason only the empirical formulas based on the grain size analysis could be used for saturated hydraulic conductivity assessment. The disturbed samples were extracted in three levels of silt - top, middle and bottom part of silt layer and subsequently as mixed samples in each selected profile of the Komárňanský channel. The selection of sampling place was made by thickness of bed silt in the measured profiles. The values of saturated hydraulic conductivity obtained from disturbed samples of bed silt - Kd were calculated according to three empirical formulas: 1. Bayer – Schweiger formula; 2. Špacek I formula and 3. Špacek II formula, firstly for samples from the top, middle and bottom part of the silt layer and then for mixed samples. The valid values Kd from single parts of the silt layers reached from 1.44 x 10−07 to 1.74 x 10−05 m s−1, the valid values Kd from mixed samples reached from 2.96 x 10−07 to 2.05 x 10−05 m s−1. According to results of comparison of Kd from single parts of silt layers and Kd from mixed samples it is not possible to assess explicitly the reliability of saturated hydraulic conductivity value set by that way. Therefore, in the next step, it will be necessary to compare these results with the values of saturated hydraulic conductivity from undisturbed samples of bed silt determined by the laboratory falling head method.

Slope stability analysis using deterministic and probabilistic approaches for poorly defined stratigraphies

The stability of slopes directly affects human lives, the environment, and the economy. Inaccurate geological profiles within numerical slope stability models can lead to potentially catastrophic consequences when model conditions do not appropriately reflect real-life stratigraphy. In cases where localised deposits are prevalent, probabilistic methods are often necessary to accommodate for unknown or poorly defined stratigraphies. Currently, there are no commercial geotechnical software packages that simulate probabilistic constitutive behaviour of materials within finite element methods for large-scale stratigraphic analysis. Instead, commercially available probabilistic methods such as the random limit equilibrium method are incapable of incorporating non-linear constitutive soil behaviour. For this reason, advanced constitutive models are seldom coupled with probabilistically varying soil layers or spatially variable soil parameters. The objective of this research is the implementation of a simplified method for probabilistic stratigraphic analysis within a commercially available FE environment, providing a technique to assess the effects of stratigraphic uncertainty on slope stability. The proposed method is presented, highlighting the impact of localised thin layers of soft material as well as their frequency and location on the slope of an operational open-pit mine. The significance of these stratigraphic effects is presented through a case study of Australia’s second-largest open-pit mine, at which the stability of a collapsed coal slope is analysed. To improve the reliability of the finite element method for slope stability assessment, the Monte Carlo approach has been incorporated to consider varying shear strength distributions for models incorporating advanced constitutive behaviour. Thicker probabilistically generated deposits of silty material resulted in increased slope Factors of Safety. Similarly, greater proportions of silty deposits within a predominantly clayey interseam produced larger safety factors than slopes without localised thin silty layers. Stratigraphic analysis indicated that the Factor of Safety was most sensitive to localised silt layers at depths greater than 83 m below ground level.

DEM STUDY ON THE PENETRATION OF JACKED PILES INTO LAYERED SOFT CLAY

In order to explore the variation law of soil particle displacement and pile force around piles during penetration process, the DEM (Discrete Element Method) model is used to test the penetration of pile foundation in layered soft soil foundation. The variation law of pile penetration force, radial pressure at pile-soil interface, friction resistance at pile side, displacement field and force field between particles during penetration process is analyzed. Research shows: (1) The penetration force increases with the increase of penetration depth and pile diameter. The increase of pile diameter is beneficial to overcome the influence of unfavorable strata. (2) At the same penetration depth, with the continuous penetration of the pile body, the radial pressure gradually decreases, showing a significant degradation phenomenon. The reason for the degradation of lateral friction is essentially the degradation of the radial pressure. (3) The distribution of contact force chain in different soil layers is similar, but the range of action is different. The contact force in silt layer is obviously larger than that in silty clay layer. The compressive stress of the soil at the end of the pile transfers radially with tensile stress. With the increase of pile diameter, the compressive stress and tensile stress in soil layer are gradually increasing, and the influence range of compressive stress and tensile stress is also gradually increasing. (4) The displacement of the soil below the pile tip is triangular, and the soil at the pile tip is squeezed around under the action of the pile tip. The influence range of particle displacement in each soil layer is different, and the influence range of particle displacement in silt layer is obviously smaller than that in silty clay layer.

Estimation of very slow groundwater movement using a Single-Well Push-Pull test

An estimation method for evaluating groundwater velocity by means of the Single-Well Push-Pull (SWPP) test by Leap and Kaplan (1988) was applied to a confined aquifer at 100 m depth with a very slow groundwater movement. The SWPP test consists of a push phase, a drift phase, and a pull phase, and the groundwater velocity is evaluated based on the Breakthrough Curves obtained from the SWPP test. In this study, the accuracy of the SWPP test system was evaluated by performing a SWPP test without drift time four times in total. Also, four types of SWPP tests with different drift times from 10 to 1802 days were conducted to obtain an estimate of the regional groundwater velocity for a maximum of approximately five years. Furthermore, the stable isotope of water (δ18O and δD) and uranine, which are known as conservative tracers, were used as tracers in the SWPP tests so as to evaluate their availabilities.The SWPP test results showed a higher reproducibility of the SWPP test using δ18O and δD than that using uranine. The sorption of uranine in the aquifer was suggested based on the SWPP test results, indicating that the hydrological properties can be obtained by comparing the SWPP test results using δ18O, δD and uranine as tracers. The SWPP test yielded an actual groundwater velocity of 0.37 m/year, which is similar to approximately 0.1 m/year order of the estimated groundwater velocity based on the results of past studies. Moreover, setting the appropriate correction and drift time in the SWPP test played an important role in investigating the very slow groundwater flow in the aquifer. When a long-term drift time was set, the recovery rate of the tracer and the chaser of δ18O and δD was decreased by diffusion in the aquifer’s silt and clay layer.

PROSPECTS FOR RATIONAL USE OF MINERAL RESOURCES OF THE DZHAKSY-KLYCH DEPOSIT, THE ARAL REGION

Rational use of mineral resources is becoming an important task for the development and economic growth of Kazakhstan. The purpose of the research was to study the state of salt-containing raw materials to determine the prospects for rational use of mineral resources of the Dzhaksy-Klych Deposit, one of the salty halite lakes of the Aral region. Exploration studies have shown that the Deposit is layered, where the halite layer is underlain by a sulfate layer: astrakhanite, mirabilite, tenardite, located on a layer of silt, the bed of salt deposits is dark brown clays, less often - clay Sands. Mineralogically, the halite formation is represented by, %: halite – 90-96, epsomite -1,2-2,6, mirabilite -0,2-1,9, gypsum-0,2-1,4. The production of table salt results in waste containing 65.5% chlorides, 24.5% sulfates, 6.5% sodium carbonates, and 3.5% sodium silicates, which can be used for pharmaceutical and medical purposes. Bottom silty mud by its origin and chemical composition belongs to the mainland silt-sulfide type and can be used for Spa and balneological treatment. The reserves of sulphate salts in the field are significant, with the average thickness of the sulphate reservoir in the southern basin being 0.87 m, and in the Northern basin 0.91 m. Intergranular and surface brine containing sodium and magnesium chloride-sulfate salts is of particular interest. Analysis of the state of mineral resources of the Dzhaksy-Klych Deposit revealed prerequisites for expanding the range of opportunities for using salt-containing raw materials. A promising direction for the development of the mineral resource base is the production of soda based on sodium chloride, as well as the production of a commercial product based on sodium sulfate and magnesium chloride. Microbiological examination showed the presence of non-pathogenic forms of halophilic bacteria in the salt-containing raw materials, which indicates safety for use in pharmaceutical and medical practice. In the Aral sea region, there is every reason for the development of the cosmetology industry, where a wide range of cosmetology and pharmaceutical products can be produced based on a combination of salt-containing and local vegetable raw materials.

Geological characteristics and exploration of shale oil in Chang 7 Member of Triassic Yanchang Formation, Ordos Basin, NW China

Abstract A set of shale-dominated source rocks series were deposited during the heyday of lake basin development in the Member 7 of Triassic Yanchang Formation, Ordos Basin, and the thickness is about 110 m. Aimed at whether this layer can form large-scale oil enrichment of industrial value, comprehensive geological research and exploration practice have been carried out for years and obtained the following important geologic findings. Firstly, widely distributed black shale and dark mudstone with an average organic matter abundance of 13.81% and 3.74%, respectively, lay solid material foundation for the formation of shale oil. Secondly, sandy rocks sandwiched in thick organic-rich shale formations constitute an oil-rich “sweet spot”, the average thickness of thin sandstone is 3.5 m. Thirdly, fine-grained sandstone and siltstone reservoirs have mainly small pores of 2–8 μm and throats of 20–150 nm in radius, but with a large number of micro-pores and nano-throats, through fracturing, the reservoirs can provide good conductivity for the fluid in it. Fourthly, continued high-intensity hydrocarbon generation led to a pressure difference between the source rock and thin-layer reservoir of up to 8–16 MPa during geological history, driven by the high pressure, the oil charged into the reservoirs in large area, with oil saturation reaching more than 70%. Under the guidance of the above theory, in 2019, the Qingcheng Oilfield with geologic oil reserves of billion ton order was proved in the class I multi-stage superimposed sandstone shale reservoir of Chang 7 Member by the Changqing Oilfield Branch through implementation of overall exploration and horizontal well volume fracturing. Two risk exploration horizontal wells were deployed for the class II thick layer mud shale interbedded with thin layers of silt- and fine-sandstones reservoir in the Chang 73 submember, and they were tested high yield oil flows of more than 100 tons per day, marking major breakthroughs in petroleum exploration in class I shale reservoirs. The new discoveries have expanded the domain of unconventional petroleum exploration.

Preliminary Investigation of Geothermal Potential in Pawam Site, Rokan Hulu, Indonesia

The site of research area is located in the back arc basin of Sumatra. It has the potential for the hot springs. This research used a Dipole-dipole array of geoelectrical resistivity method. The length of the survey line varies due to in the research location there are many buildings that become tourist attractions. The results showed that the subsurface structure consisted of silt, sandstone and meta sediment. The resistivity distribution shown that there was found the silt layer of soft wet mud in the hot spring zone. The distribution pattern of hot spring in this site is an overflow flow type. The flow is controlled by a fault zone. The direction of this flow is west of the river flow.

Seismic interaction of tunnel-building systems on soft clay

Seismic performance of structures located in urban areas, such as midrise buildings, can be significantly affected by its interaction with underground facilities, such as tunnels. To date however, there is still a lack of proper understanding regarding the interplay between incoming seismic waves reflected in underground infrastructure, and the energy feeding back from surface structures swinging back and forth during a large earthquake. In particular, due to its complexity, the effect that underground tunnels have in the seismic response of medium to low rise buildings is often ignored or its assessment is over simplified in practice. This, in turn, can lead to unsafe or costly designs. This paper presents a numerical study aimed at closing the gap in numerical data regarding the potential area of influence in which ground motion variability is strongly affected by the presence of an underground tunnel, and more importantly, the actual impact in the structural building seismic performance. This study is focusing on tunnel-building systems located in soft clay deposits, slightly intercalated by layers of silty sands and sandy silts, such as those found in Mexico City. Series of three-dimensional finite difference models were developed to study the proximity effect of the tunnel to the building, in the computed building structural response. From the results gathered in here, it was evident the ground motion modification in the surrounding soil that occur mostly in the transversal ground motion component due to tunnel-building interaction, establishing detrimental or beneficial soil-structure interaction effects, for both normal and subduction events.

Thermal and hydrogeological aquifers characterization by coupling depth-resolved thermal response test with moving line source analysis

In this paper for the first time the Moving Line Source (MLS) model is combined with a depth-resolved Thermal Response Test (TRT). The latter was performed in a heterogeneous and groundwater rich subsoil, composed by a layering of silty sand, medium-fine sand and coarse-medium sand, with a layer of clayey silt separating a shallow aquifer from a deep one.The temperature evolution in the ground along the vertical axis was analysed with both the standard Infinite Line Source (ILS) and the MLS. The two models lead to similar estimates of the thermal conductivity in those regions of the subsoil where conduction prevails, while the MLS performs better where a significant groundwater velocity is expected. In these layers, the MLS analysis allows to derive both the thermal conductivity and the Darcy velocity. The MLS results were validated by comparison with a numerical simulation on a multiple-layers ground model developed in MODFLOW/MT3DMS using a constant energy boundary condition. The combined depth-resolved TRT/MLS approach represents an important method for an accurate design of the Ground Heat Exchangers under the presence of groundwater flow.

Assessment of submarine groundwater discharge in the intertidal zone of Laizhou Bay, China, using electrical resistivity tomography

Coastal zones are the most sensitive and vulnerable ecological environments in the world. Submarine groundwater discharge (SGD) is an important pathway for material transport between land and sea in the low-lying coastal plains of coastal zones. In the present study, electrical resistivity tomography was used to monitor submarine groundwater discharge in the intertidal zone. The salinity change ratio was derived using Archie's law and Manheim's equation, and was used as an index to describe the dynamic discharge process. A model of the seawater circulation process in the multilayer coastal aquifer system was established. The model contains a window area between the upper unconfined and lower confined aquifer, and a highly permeable channel in the upper silt layer. The results of the study provide a theoretical basis and technical support for the rapid assessment of SGD in low-lying coastal plains, and will assist in the management of coastal zone environments.