Sand Layer Research Articles

Behaviour of Spread Footings Resting on Fibre-Reinforced Green Binder-Stabilised Sand Layers

Behaviour of Spread Footings Resting on Fibre-Reinforced Green Binder-Stabilised Sand Layers

Nonlinear consolidation finite element analysis of a layered soft soil foundation under multistage loading based on the continuous drainage boundary

To comprehensively consider the impacts of stratification, residual pore water pressure, soil nonlinearity, and boundary permeability on consolidation settlement of soft soil foundations for accurate prediction, a continuous drainage boundary condition is proposed in this study that reflects the residual pore pressure under multistage loading, and a nonlinear elastic constitutive model based on the double logarithmic model is adopted to account for the nonlinear consolidation behaviour of soils. A UMAT subroutine is developed based on the proposed boundary condition and nonlinear elastic constitutive model. Subsequently, the developed subroutine is compared with the built-in linear elastic soil constitutive model in ABAQUS and engineering examples. The application of continuous drainage boundaries in stratified foundations is analysed, as well as the influence of factors such as the loading rate and soil nonlinearity on consolidation settlement. The results indicate that, compared to the built-in model, the subroutine developed in this study can be employed to more accurately calculate the nonlinear consolidation of multilayered foundations under multistage loading. By adjusting the loading rate parameter αk, consolidation under different loading conditions can be predicted. Additionally, the proposed boundary condition simplifies the calculations for soft soil foundations with sand layers, providing a novel computational approach for the design of construction loading schemes and long-term settlement predictions in soft soil foundations.

Recovery of microbial biomass and purification performance after scraping of full-scale slow sand filters

Slow sand filters (SSFs) are widely used in drinking water production to improve microbial safety and biological stability of water. Full-scale SSFs are maintained by scraping the biomass-rich top layers of sand. The period of downtime required for filter recovery after scraping is a major challenge due to limited knowledge of the re-stabilisation of purification processes. This study examined the recovery of microbial biomass, and removal of dissolved organic carbon (DOC) and ammonium (NH4+) in water phase and/or on sand along the depth of a scraped full-scale SSF. Scraping reduced microbial biomass on sand in the top layers, while the main prokaryotic taxa remained unaltered. Cellular ATP (cATP) and intact cell counts (ICC) in water sampled from the top layers increased, indicating a temporary disruption in functionality for 37 days. However, stable concentrations of cATP and ICC and similar microbial community composition in the effluent after scraping revealed that deeper layer biofilms offset any scraping effect. Consistent DOC and NH4+ removal after scraping showed that deeper layers effectively performed the role of the top layer. These findings highlight the resilience and robustness of microbial communities in mature full-scale SSFs and their contribution to water treatment efficiency after disturbances caused by scraping.

Study on the Mechanism of Water and Sand Leakage in a Foundation Pit Retaining Structure Based on the Computational Fluid Dynamics–Discrete Element Method

The existence of defects in the enclosure structure is the primary cause of water and sand leakage in foundation pits, as well as being a significant source of danger in pit construction, but current research lacks an in-depth investigation of the generation mechanism and gestation process. In this paper, which comprehensively considers the microscopic particles and macroscopic level, the development mechanism of a water and sand leakage disaster in a foundation pit with a water-rich sand layer was studied using the principle of computational fluid dynamics and discrete element method coupled analysis (CFD–DEM); moreover, based on the anisotropy of the particle force and fluid energy analysis, the deformation of the stratum and ground stress field were analyzed. The results show that the stress field will produce a plugging effect at a certain distance from the defect, and the strata exhibit a dominant displacement tendency in the vertical direction, resulting in the emergence of a gradually concave stress relaxation zone and an elliptical contour in the strata displacement map near the defect. The fluid energy describes the displacement of the sand layer very well, and it is separated into the sand layer’s centralized loss region and the major loss area based on the high and low levels of the fluid energy class. The impact of fluid at the defect reaches the maximum kinetic energy, which penetrates the structural weakness and causes the loss of sand particles, and the cross-section of the water influx near the defect gradually expands with the loss of particles, indicating that there is a danger of further expansion of the defect under the impact of water flow. These results have technical implications for the management of water and sand leakage disasters in foundation pit engineering.

Early Pleistocene depositional and environmental conditions at Dachangliang, Nihewan Basin, NE China

Early Pleistocene depositional and environmental conditions at Dachangliang, Nihewan Basin, NE China

A Grain Size Profile Prediction Method Based on Combined Model of Extreme Gradient Boosting and Artificial Neural Network and Its Application in Sand Control Design

Summary The grain size distribution along the well depth is of great significance for the prediction of the physical properties and the staged sand control design of the unconsolidated or weakly consolidated sandstone reservoir. In this paper, a new method for predicting the formation median grain size profile based on the combination model of extreme gradient boosting (XGBoost) and artificial neural network (ANN) is proposed. The machine learning algorithm and weighted combination model are applied to the prediction and analysis of reservoir grain size. The prediction model is improved from two aspects: First, the feature engineering of the XGBoost-ANN model is constructed by using the data of multiple sampling points on the logging curve. Second, the prediction accuracy is improved by increasing the dimension of the prediction model, that is, the XGBoost and ANN single-prediction models are weighted by the error reciprocal method and a combined prediction model containing multidimensional information is established. The research results show that compared with the single-point mapping model, the prediction accuracy of the multipoint mapping model considering the vertical geological continuity of the reservoir is higher than that of the single-point prediction and the coefficient of determination in the testing set can be improved up to 14.5%. The influence of different weighting methods on prediction performance is studied, and the prediction performance of original XGBoost, ANN, and XGBoost-ANN combined models is compared. The combined prediction model has a higher prediction accuracy than the single XGBoost and ANN models with the same number of sampling points and the coefficient of determination can be improved by up to 16.5%. The prediction accuracy and generalization ability of the XGBoost-ANN combined model are evaluated comprehensively. The combined model is used to design layered sand control of a well in an adjacent block, and good results have been achieved in production practice. This study provides a new method with high accuracy and efficiency for the prediction of unconsolidated sand median grain size profile.

Centrifuge modeling of a large-scale surcharge on adjacent foundation

This study investigates the ground and structural response of adjacent raft foundations induced by large-scale surcharge by ore in soft soil areas through a 130g centrifuge modeling test with an innovative layered loading device. The prototype of the test is a coastal iron ore yard with a natural foundation of deep soft soil. Therefore, it is necessary to adopt some measures to reduce the influence of the large-scale surcharge on the adjacent raft foundation, such as installing stone columns for foundation treatment. Under an acceleration of 130 g, the model conducts similar simulations of iron ore, stone columns, and raft foundation structures. The tested soil mass has dimensions of 900 mm × 700 mm × 300 mm (length × width × depth), which is remodeled from the soil extracted from the drilling holes. The test conditions are consistent with the actual engineering conditions and the effects of four-level loading conditions on the composite foundation of stone columns, unreinforced zone, and raft foundations are studied. An automatic layer-by-layer loading device was innovatively developed to simulate the loading process of actual engineering more realistically. The composite foundation of stone columns had a large settlement after the loading, forming an obvious settlement trough and causing the surface of the unreinforced zone to rise. The 12 m surcharge loading causes a horizontal displacement of 13.19 cm and a vertical settlement of 1.37 m in the raft foundation. The stone columns located on both sides of the unreinforced zone suffered significant shear damage at the sand-mud interface. Due to the reinforcement effect of stone columns, the sand layer below the top of the stone columns moves less. Meanwhile, the horizontal earth pressure in the raft foundation zone increases slowly. The stone columns will form new drainage channels and accelerate the dissipation of excess pore pressure.

Measurements of the frequency dependence of geo-alpha in clayey silt at low frequencies

Transmission loss (TL) measurements in the Santa Barbara Channel, together with co-located chirp measurements, show that geo-alpha (dB/l) in clayey silt increases approximately linearly with frequency (f) at f < 3 kHz. TL was measured between a fixed source and fixed vertical array at 3.7 km at 0.3 < f < 5 kHz. Geo-alpha was inverted from the TL data at 0.3, 1.1 and 1.9 kHz. Inversion calculations at 1.1 and 1.9 kHz considered both geo-alpha and bio-alpha due to layer of anchovies at 12 m. Inversion calculations at 0.3 kHz considered only the effect of geo-alpha; the effect bio-alpha on TL was small. Geo-alpha was also inferred from chirp sonar measurements at 3.2 and 6.2 kHz at the ends and middle of the TL track. Chirp sonar showed that the bottom consisted of a layer of unconsolidated sediments overlying a layer of sand. Co-located cores revealed that the unconsolidated layer consisted of clayey silt. Bio-alpha data were compared to Biot and VGS theories and the theory of attenuation in suspended sediments (Pierce et al., 2017). The measured frequency dependence is consistent with Pierce et al.’s theory. This research was supported by The Office of Naval Research Ocean Acoustics Program.

Amplitude Variation with Offset (AVO) Inversion for Reservoir Visualization: A Case Study of Taje Field, Niger Delta, Nigeria

Amplitude Variation with Offset (AVO) inversion analysis was performed on pre-stack seismic data and well information gathered from the shallow offshore area of the Niger Delta. This analysis aimed to improve reservoir visualization and employed the Hampson Russell Geoview, AVO, and STRATA software tools. The seismic data were provided in Seg-Y format, covering an in-line range from 4503 to 5569, an x line range from 1434 to 2026, and an angle of incidence range of 0 to 45°. The study centered on the Taje well_026. Within the subsurface, the authors identified five distinct reservoirs, labeled A to E, located at various depths ranging from 3057.50 to 3115.00 m, 3115.00 to 3157.50 m, 3157.50 to 3190.00 m, 3190.00 to 3200.00 m, and 3200.00 to 3239.00 m, respectively. These reservoirs exhibited different fluid compositions. Reservoir A, primarily composed of sandstone, contained brine, whereas Reservoirs B and D, dominated by shale, contained gas. On the other hand, Reservoirs C and E, both comprised of sandstone, held oil. Reservoir C is distinguished by its clean sandstone unit. The inversion results revealed that both Reservoirs C and E consisted of low impedance sand layers surrounded by higher impedance shale layers. The gas migrated from the reservoir and was trapped within the shale units due to deformation of the lithological units, likely induced by stress accumulation. This migration process was facilitated by the shale’s inability to undergo smearing, possibly as a result of faulting mechanisms.

Electrical Resistivity Tomography (ERT) for investigating subsurface structures in the karst area of the Ek Leuntie Cave, Aceh Province

Ek Leuntie Cave, in the southern city of Banda Aceh, Aceh Province, is recognized as an educational media based on geopark sites because it holds a 7400-year paleotsunami track record. As a karst area, Ek Leuntie Cave is vulnerable to the impact of geological disasters such as earthquakes, sinkholes and subsidence. As an effort to reduce the negative impact of geological disasters, geophysical studies have been applied in the Ek Leuntie Cave Karst area. The study aims to identify the subsurface geological structure of the Karst area. The identification was carried out using the Electrical Resistivity Tomography (ERT) method of Wenner-Schlumberger configuration applied to two measurement trajectories that have South-North and West-East directions in front of the Ek Leuntie Cave door. ERT data acquisition results were then modeled in inversion using Res2Dinv software to produce a 2D model of the subsurface geological structure of the Ek Leuntie Cave karst area based on variations in rock resistivity values. Interpretation of subsurface geological structure modeling is validated with shallow drilling data (Hand Auger). The inversion modeling results show that the rock resistivity value in the Ek Leuntie Cave area reaches a depth of 30 m which has a resistivity value of 0 - 1000 Ωm. The results of the interpretation of resistivity values and validation of drill data show that the Ek Leuntie Cave area is covered by a layer of sand with fine to coarse texture and the layer below is a layer of limestone at a depth of ± 0.4 meters with a resistivity value of 50 - 250 Ωm. Limestone generally shows porosity with the possibility of caves or pores in the rock formation at Ek Leuntie Cave, making it vulnerable to damage from earthquakes, landslides, and subsidence. The results of the study are expected to provide updated information in efforts to develop the Ek Leuntie Cave geopark area.

Vertical bearing capacity of spun precast concrete pile in liquefiable soil: a case study

Spun precast prestressed concrete (SPC) pile has been used in many parts of the world as a viable foundation alternative. This study assesses the load-carrying capacity of SPC piles passing through a deep soft subsoil layer and resting on a dense sand layer. The vertical bearing capacity of the SPC pile has been estimated using various analytical methods and static pile load tests for the Jolshiri area of Dhaka. The liquefaction potential of the site has been assessed using local seismic site conditions, field and laboratory test data. The liquefaction analysis suggests that the topsoil layer is liquefiable to a depth of 4.5 m. The capacity obtained from the load test is compared with those obtained from the different methods, ultimate push-in load, and local design guidelines. Finite Element Analysis (FEA) was performed considering the hardening soil (HS) model using PLAXIS 3D to simulate field conditions. The load settlement response obtained from FEA shows a good agreement with the test results. The capacity examinations primarily suggest that the SPC pile can be a viable foundation solution for the subsoil conditions of Jolshiri Abasion area of Dhaka.

Rare faction of flora of the designed landscape reserve “Balka Shchurovka”

The article is devoted to the study of the modern distribution of certain rare plant species within the "Balka Shchurovka" beam system (near the settlements of Dniprovske, Novomykolaivka of the Verkhnyodniprovska OTG of the Dnipropetrovsk region) and substantiation of the prospects for granting the object the status of a nature conservation area. The natural diversity of the vegetation cover of the designed reserve consists of zonal steppe vegetation, bairach forests, psamophilic and petrophilic communities, and meadow vegetation. According to indicators of biodiversity, the territory b. Shchurovka is one of the most valuable within the borders of Verkhnyodniprovska OTG of Dnipropetrovsk region. In the process of researching the flora of the planned reserve, a number of new locations of species rare for the region and the region were discovered. 26 regionally rare plant species grow here, 13 species listed in the Red Book of Ukraine, 3 species from Resolution 6 of the Berne Convention and Annexes of the Habitats Directive, presented in the flora of Ukraine, 1 species from the World Red List. The list of plants of the Dnipropetrovsk region included in the Red Book of Ukraine includes 56 species of vascular plants, of which 13 species grow within the b. Rat, which is 23% of the total number of red book species of Dnipropetrovsk region. An important and interesting feature of the layer of sand exposed on the right slope of the gully is the presence of blocks of red sandstone enriched with iron oxides. Near the sandstone outcrops, a characteristic complex of flora has formed on sandy soil with the participation of Sempervivum ruthenicum Schnittsp. & C.B. Lehm, Pulsatilla pratensis (L.) Mill. s.l., Thymus pallasianus Heinr.Braun, Peucedanum arenarium Waldst. & Kit. (Taeniopetalum arenarium (Waldst. & Kit.) V. N. Tichomirov), Achillea leptophylla M. Bieb. Jurinea cyanoides (L.) Rchb and Pulsatilla patens (L.) Mill grow here. s.l. - rare species from the Annexes of the Habitats Directive, Annex I of the Berne Convention, which prefer biotopes with an intact structure as part of rare coenoses. The study of the rare fraction of the flora of the beam system in the context of the conservation of biodiversity of the Right Bank Steppe of the Dnieper region can become the basis of the nature conservation concept of sustainable development of the region.

Rare faction of flora of the designed landscape reserve “Balka Shchurovka”

The article is devoted to the study of the modern distribution of certain rare plant species within the "Balka Shchurovka" beam system (near the settlements of Dniprovske, Novomykolaivka of the Verkhnyodniprovska OTG of the Dnipropetrovsk region) and substantiation of the prospects for granting the object the status of a nature conservation area. The natural diversity of the vegetation cover of the designed reserve consists of zonal steppe vegetation, bairach forests, psamophilic and petrophilic communities, and meadow vegetation. According to indicators of biodiversity, the territory b. Shchurovka is one of the most valuable within the borders of Verkhnyodniprovska OTG of Dnipropetrovsk region. In the process of researching the flora of the planned reserve, a number of new locations of species rare for the region and the region were discovered. 26 regionally rare plant species grow here, 13 species listed in the Red Book of Ukraine, 3 species from Resolution 6 of the Berne Convention and Annexes of the Habitats Directive, presented in the flora of Ukraine, 1 species from the World Red List. The list of plants of the Dnipropetrovsk region included in the Red Book of Ukraine includes 56 species of vascular plants, of which 13 species grow within the b. Rat, which is 23% of the total number of red book species of Dnipropetrovsk region. An important and interesting feature of the layer of sand exposed on the right slope of the gully is the presence of blocks of red sandstone enriched with iron oxides. Near the sandstone outcrops, a characteristic complex of flora has formed on sandy soil with the participation of Sempervivum ruthenicum Schnittsp. & C.B. Lehm, Pulsatilla pratensis (L.) Mill. s.l., Thymus pallasianus Heinr.Braun, Peucedanum arenarium Waldst. & Kit. (Taeniopetalum arenarium (Waldst. & Kit.) V. N. Tichomirov), Achillea leptophylla M. Bieb. Jurinea cyanoides (L.) Rchb and Pulsatilla patens (L.) Mill grow here. s.l. - rare species from the Annexes of the Habitats Directive, Annex I of the Berne Convention, which prefer biotopes with an intact structure as part of rare coenoses. The study of the rare fraction of the flora of the beam system in the context of the conservation of biodiversity of the Right Bank Steppe of the Dnieper region can become the basis of the nature conservation concept of sustainable development of the region.

Effect of Water Conservation and Nitrogen Reduction on Root Growth and Yield in Spring Maize in Typical Sand Interlayered Soil

Given the low water and fertiliser use efficiency and the extensive distribution of sand interlayered soil in the Hetao irrigation district (HID), this study aimed to investigate the effects of different irrigation and fertilisation regimes on root parameters and yield in spring maize grown in sand interlayered soil. A two-year field plot experiment was conducted using the spring maize “Ximeng 3358” under three irrigation and nitrogen levels. Root length (RL), surface area (RS), diameter (RD), volume (RV), and length density (RLD), grain yield, and water use efficiency (WUE) were examined. Root growth was inhibited at the sand layer, with approximately 72.46–87.37% of the roots concentrated in the 0–40 cm soil layer. Notably, the proportion of roots in the bottom layer was 24.61–87.37% higher than that in the sub-bottom layer. Moreover, RL, RS, RD, and RV peaked in the medium irrigation and nitrogen fertilisation (I2F2) treatment. Furthermore, correlation analysis showed that the root parameters were significantly positively correlated with yield and WUE, with RS being most correlated to yield and WUE. Roots at a narrow row spacing of 20 cm (NR20) and at a depth of 10–20 cm were strongly correlated with yield and WUE. Conclusively, the I2F2 treatment can be used as the optimal combination of water and nitrogen for sand interlayered soil farmlands.

Study on Effect of Particle Size Distribution on Water-Retention Capacity of Coral Sand from Macro and Micro Perspective

The reclamation coral sand (CS) layer is the survival environment for island reef vegetation in the South China Sea. The root system within the CS bed draws water necessary for vegetation growth, implying that the water-retention capacity of CS plays a pivotal role in determining vegetation viability. Particle size distribution (PSD) significantly influences the water-retention capacity of geomaterials. This study examines the impact of PSD on the water-retention capacity of CS from both macro (soil–water characteristic curve, SWCC) and micro (pore water distribution) perspectives using the pressure plate test and nuclear magnetic resonance technique, and an F&X model was used to analyze the SWCC of CS. The findings indicated that the F&X model aptly describes the SWCC of CS with different PSDs. Both the air entry value and residual water content rise with an increased content of fine grains (d < 0.25 mm), suggesting that the presence of fine grains augments the water-retention capacity of CS. It is considered that a size range of d = 0.075–0.25 mm predominantly impacts the water-retention capacity of CS. The PSD primarily influences the water-retention capacity by affecting the pore size distribution of CS. The volume of small pores swells with the surge of fine-grain content, while the maximum pore size contracts with increasing fine-grain content. Limited pore connectivity in CS means macropores can retain water even under high suction, bolstering the water-retention capacity of CS. These findings offer theoretical guidance for selecting gradation parameters for the planting layer on island reefs.

Investigating the Martian soil at the InSight landing site

The InSight mission is a geophysical mission aimed at better understanding the structure of Mars and of the other rocky planets of the solar system. To do so, a lander accommodating two cameras, a very sensitive seismometer, and a dynamic self-penetrating heat probe nicknamed the mole were placed on the Mars surface by the Instrument Deployment Arm (IDA). Besides geophysical data (which definitely enriched the existing knowledge on the structure of Mars), the InSight instruments significantly increased the knowledge of the geological and geotechnical characteristics of the surface material at the InSight site. Small strain (elastic) parameters were derived from wave velocity measurements during the hammering sessions between the self-penetrating probe and the seismometer. A detailed observation of the soil profile along a depth of 37 cm was made possible thanks to the photos taken by the cameras, and to a detailed analysis of the mole penetration process. Further information was provided by an intense campaign of scraping and piling conducted by the IDA on the surface sand/dust layer. It was shown that the soil profile was composed of a surface 1 cm thick sand/dust layer, overlaying an around 20 cm thick loose duricrust made up of a cohesive matrix containing some pebbles, located above a 12 cm layer of sand overlaying a gravel/sand deposit. It is believed that the geology and soil mechanics data provided by the InSight mission will help for further robotic exploration of Mars.

Load transfer mechanism of geotextile-reinforced sand layer over semirigid column-improved soft soil

Load transfer mechanism of geotextile-reinforced sand layer over semirigid column-improved soft soil

Damage to Natural Gas Distribution Steel Pipelines caused by Rigid Bodies resulting from the Excavation of Laying Trenches

The present paper focuses on analyzing the occurrence of defects such as dents and local deformations by laboratory simulations of a real case of a defect detected on a natural gas distribution pipeline lain at a depth of approximately 0.6 m. The defect is caused by a river stone which due to the compression forces, damages the pipe to the point of cracking. In the laboratory, the simulation was carried out on a steel pipe insulated with extruded polyethylene which was acted upon by a mandrel made of duralumin. The purpose of the tests is to determine the maximum values at which the pipe material fractures. It was found that the fracture of the pipes when there are rigid bodies in the protective layer of sand is accelerated by the sand existing between them and the pipe and by the change in the properties of the steel the pipes are made of when they are kept in water.

Reactive transport modeling of organic carbon degradation in marine methane hydrate systems

Natural methane hydrate has often been observed in sand layers that contain no particulate organic carbon (POC), but are surrounded by organic-rich, fine-grained marine muds. In this paper, we develop a reactive transport model (RTM) of a microbially-mediated set of POC degradation reactions, including hydrolysis of POC driven by extracellular enzymes, fermentation of the resulting high-molecular weight dissolved organic carbon (HMW-DOC), and methanogenesis that consumes low-molecular weight dissolved organic carbon (LMW-DOC). These processes are mediated by two groups of microbes, fermenters and methanogens that are heterogeneously distributed in different lithologies, with the largest numbers of microbes in the large pores of coarse-grained layers. We find that the RTM can reproduce methane hydrate occurrences observed in two different geological environments, at Walker Ridge Site 313-H (Gulf of Mexico) and IODP Site U1325 (Cascadia Margin). We also find that microbes can degrade POC even if they are physically separated, as extracellular enzymes and DOC can diffuse away from where they are produced by microbes. Microbial activity is highest at relatively early times after burial at shallow depths and near lithological boundaries, where concentration gradients transport solutes to intervals that contain the most microbes.

Construct a Geomechanical Model to Estimate the Critical Drawdown Pressure for the Sandstone Reservoirs

Abstract The petroleum industry is becoming more concerned about sand production because of the mounting difficulties it causes, along with the accompanying technological and operational obstacles. In this study, a field case in the south of Iraq was carried out to analyze the potential of sanding and rock collapse. This investigation has focused on the upper and lower sand layers, which are sandstone reservoirs within this field. To achieve the purpose of this study, a One-Dimensional Geomechanical Model was established along the area of interest. The critical drawdown pressure (CDDP) at which the well may be produced without experiencing shear failure or sanding was then determined at various depletion rates. The results indicated that as the rocks strength increases, so does depletion and the quantity of sand-free drawdown. Because the upper sand unit has a higher critical bottom-hole flowing pressure (Pcw), it is possible that it will begin producing sand before the lower unit. Sanding becomes more likely with each drawdown when the reservoir pressure reaches approximately 2400 psi. Finally, this research may be used as a predictor of the likelihood of sanding over the well’s productive life and as a guide for production engineers seeking to achieve optimal completion performance.