RDV■(dynamic vasoactive reactor)chemical technology represents a disruptive innovation operating under both surface and downhole conditions,producing irreversible and in situ adaptable effects.It has demonstrated tra...RDV■(dynamic vasoactive reactor)chemical technology represents a disruptive innovation operating under both surface and downhole conditions,producing irreversible and in situ adaptable effects.It has demonstrated transformative capacity across crude oils of various API gravities,with notable impact on extra-heavy crudes and bitumens,through a mechanism based on targeted proton donation that induces selective protonation of polar structures,generating transient carbocations that catalyze molecular fragmentation.This work presents a comprehensive analysis of the effects of RDV-DMG001■treatment(currently named RDV-01L■)on bitumen samples from the Primrose field,Alberta,Canada,using capillary chromatography,SARA analysis,and rheological evaluation,complemented with comparative data on prior applications of RDV-01L■in extra-heavy crudes from Venezuela(Boscán and El Salto).Results for Primrose bitumen show an 85%reduction in viscosity(from 500,000 to 75,000 cP),an increase in API gravity from 8.5 to 15.0(+76.4%),and molecular redistribution toward medium-chain hydrocarbons(C_(13)-C_(16)),with increases in molar and mass fractions up to 39.1%and 62.3%,respectively.SARA analysis confirmed fragmentation of asphaltenes(2.0%mass reduction)and a 5.8%increase in resins,improving colloidal stability and lowering precipitation risk.These changes align with RDV■’s mechanism of action based on carbocation generation.Notably,in field conditions-which are more dynamic and energetically favorable-RDV■treatment efficacy tends to exceed laboratory results,due to synergy among temperature,pressure,and fluid flow gradients which accelerate and enhance protonation and molecular fragmentation.Validated in contexts of advanced chemical transformation(Venezuela,Canada),the technology enables substantial improvements in fluidity,transport,processing,and recovery,with significant potential for annual cost savings in extraction and processing.This study positions RDV■as a disruptive,irreversible,and in situ adaptable chemical solution superior to conventional technologies such as surfactants,nanocatalysts,or aquathermolysis.RDV■is a quantum-impact chemical technology operating via molecular protonation reactions and controlled carbocation formation.The term“quantum”is used here as a conceptual analogy to describe the magnitude and specificity of the molecular reconfiguration induced by RDV■,without asserting direct experimental evidence of quantum reactivity.展开更多
In the sweltering heat of summer,a visitor to Nugusitai Town of Tongliao City,Inner Mongolia Autonomous Region,might find it hard to recognise the landscape.Once a desolate expanse of drifting sand,the hillsides are n...In the sweltering heat of summer,a visitor to Nugusitai Town of Tongliao City,Inner Mongolia Autonomous Region,might find it hard to recognise the landscape.Once a desolate expanse of drifting sand,the hillsides are now cloaked in lush forest.Tall wind turbines rotate quietly,and wetlands glimmer between groves of forest,providing a haven for waterfowl.展开更多
Calcareous sands are widely distributed on the coral reefs,continental shelf,and seashores between 30north and south latitude and are commonly utilized as filling materials for the construction of artificial islands a...Calcareous sands are widely distributed on the coral reefs,continental shelf,and seashores between 30north and south latitude and are commonly utilized as filling materials for the construction of artificial islands and infrastructure foundations.In this study,calcareous sands were cemented by enzymatically induced carbonate precipitation(EICP)technique.Drained triaxial tests were conducted on the EICPtreated calcareous sands.Results showed that the specimens with different cementation levels exhibited different responses in mechanical behavior.The differences in the sand fabric after consolidation under a relatively high confining pressure resulted in the untreated specimen exhibiting a higher peak strength compared to the lightly cemented specimen.High confining pressures exhibited a strongly inhibiting effect on dilatancy,which could be counteracted by increasing the cementation level.The EICP-treated specimen could have one or two yield points(smaller-strain and larger-strain yields).For lightly cemented specimens,the smaller-strain yield stress decreased under high confining pressures due to the partial carbonate bonding degradation during consolidation.The stress line of untreated particle breakage(UPB)was a critical boundary to distinguish failure mode in the p′-q space.For the EICP-treated specimens,the yield stress located above or below the UPB stress line indicates the simultaneous or sequential breakage of the carbonate bonds and sand particles,respectively.Accordingly,the EICPtreated specimen exhibited brittle or ductile properties.Failure mode transformation could be triggered by increasing cementation level or confining pressure.展开更多
The northwestern margin of Junggar Basin is the region with the richest oil sand resources in China.For better understanding the enrichment rules and deployment of exploration and development of regional oil sand,it i...The northwestern margin of Junggar Basin is the region with the richest oil sand resources in China.For better understanding the enrichment rules and deployment of exploration and development of regional oil sand,it is of great scientific significance to study the accumulation conditions of oil sand in different strata and mining areas of the Junggar Basin.Through a large number of field investigations,drilling verification and sampling tests,it is found that the oil sand in the region covers an area of 2000 km^(2),with shallow and thick reservoir,and predicted resource of 180 million tons.The oil sand resources are mainly distributed in four geological strata,namely the Middle Triassic Karamay Formation,Early Jurassic Badaowan Formation,Late Jurassic Qigu Formation,and Early Cretaceous Qingshuihe Formation.The reservoir is mainly composed of sandstone with high porosity and permeability,and the reservoir space is mainly intergranular pores with a medium average oil content.The oil sand deposit in the region is a typical destructive oil reservoir.The crude oil in the oil sand layer is degraded and thickened from the deep to the shallow,the content of saturated hydrocarbon decreased,and the content of aromatic hydrocarbon,non-hydrocarbon and asphaltene increased.The oil source comes from the deep Permian hydrocarbon-generating depression.Unconformities,faults and marginal fan delta-braided river depositional systems constitute effective migration and storage systems.Caprocks of the Upper Triassic Baijiantan Formation,Lower Jurassic Sangonghe Formation and Lower Cretaceous Hutubihe Formation were formed by three large scale lake transgressions.The Indosinian,Yanshan and Late Yanshan movements are the main driving forces for the migration of deep oil and gas to the shallow edge to form oil sand deposits.It is considered that the oil sand in the northwestern margin of Junggar Basin is of a slope complex migration type.展开更多
The aim of this article is to study and reveal the mineralogical composition of dune sands from the Bouarfa Figuiget region(eastern Morocco)and to find the potential source of these dune sands.The mineralogical study ...The aim of this article is to study and reveal the mineralogical composition of dune sands from the Bouarfa Figuiget region(eastern Morocco)and to find the potential source of these dune sands.The mineralogical study was made by combining field studies to collect samples and determine the facies of the surrounding area with labortory studies,including geochemical analysis(DRX analysis),morphoscopic study of the sands under a binocular magnifying glass according to the fractions making up these sands,heavy mineral extraction and analysis under a microscope,and calcimetric analysis.The results revealed two main categories of minerals in sandy deposits:light and heavy minerals.These include quartz,plagioclase feldspar,calcite platelets,and fragments of greyish,greenish,and whitish rock.Quartz was the dominant mineral.Heavy minerals include dark(opaque)minerals such as garnet,tourmaline,epidote,zircon,rutile,and rock fragments.This composition is the result of erosion,transport,and deposition processes in the crystalline sandstone and sedimentary formations of the eastern High Atlas,which feed the study area via aeolian pathways,including winds from ERG CHBI.The quartz grains in the dune sands of the eastern region,accumulated by wind action,are mainly round,matte grains of aeolian origin.The mineral associations observed show the presence of two types of sandy deposits:(1)Sand dominated by matte,round quartz grains(fraction 225μm),associated with accessory minerals(garnet,tourmaline,zircon,rutile,kyanite,and epidote),oxides(magnetite and ilmenite),and rock fragments of mixed mineral,crystalline,and sedimentary origin.(2)Totally dominant matte round quartz sand associated with iron oxides and a few rock fragments(fractions 142μm,180μm and 357μm).Sand with fraction 225μm consists almost entirely of quartz(8%)with garnets and a few rock fragments.These results suggest that the variation in the composition of the dune sands in the study area depends on the nature of the granulometric fraction studied,and therefore on the variety of sources feeding the sands studied(Chott Tigri,crystalline and sedimentary formations of the Eastern High Atlas).展开更多
The Longfengshan structural belt lies in the southern Changling Depression.The Yingcheng Formation is the primary gas-bearing unit.The Yingcheng Formation has low permeability and contains deep,tight gas that is chall...The Longfengshan structural belt lies in the southern Changling Depression.The Yingcheng Formation is the primary gas-bearing unit.The Yingcheng Formation has low permeability and contains deep,tight gas that is challenging to extract.Industrial gas flow has been achieved from the B218 and B220 well blocks in the sandstone layer of the first member of Yingcheng Formation(Ying I),indicating the potential of this sandstone group for gas production.Although oil and gas are widely distributed in the Ying I sandstone layer,production capacity varies significantly across the formation.into six sublayers.Drilling,logging,and laboratory testing data were integrated to subdivide the Ying I sandstone layer into six sublayers.Core and well logging analyses indicate a braided river delta depositional environment.Data and seismic inversion identify the Ying I-5 sublayer as the primary exploration target.The effective reservoir in the eastern fan body,where porosity ranges from 5%to 13%and maximum effective thickness reaches 34 m.This study basis for optimizing well placement and estimating gas reserve parameters in the Ying I sandstone layer of the Longfengshan area.The findings can guide the development of other tight gas reservoirs.展开更多
The Lower Cretaceous Manville Group of Upper Mc Murray Formation is one of the main bitumen reservoirs in Athabasca.In this study,the relationship between reservoirs heterogeneity and bitumen geochemical characteristi...The Lower Cretaceous Manville Group of Upper Mc Murray Formation is one of the main bitumen reservoirs in Athabasca.In this study,the relationship between reservoirs heterogeneity and bitumen geochemical characteristics were analyzed through core and microscopic observation,lab analysis,petrophysics and logging data.Based on the sedimentology framework,the formation environment of high-quality oil sand reservoirs and their significance for development were discussed.The results indicate that four types lithofacies were recognized in the Upper Mc Murray Formation based on their depositional characteristics.Each lithofacies reservoirs has unique physical properties,and is subject to varying degrees of degradation,resulting in diversity of bitumen content and geochemical composition.The tidal bar(TB)or tidal channel(TC)facies reservoir have excellent physical properties,which are evaluated as gas or water intervals due to strong degradation.The reservoir of sand bar(SB)facies was evaluated as oil intervals,due to its poor physical properties and weak degradation.The reservoir of mixed flat(MF)facies is composed of sand intercalated with laminated shale,which is evaluated as poor oil intervals due to its poor connectivity.The shale content in oil sand reservoir is very important for the reservoir physical properties and bitumen degradation degree.In the context of regional biodegradation,oil sand reservoirs with good physical properties will suffer from strong degradation,while oil sand reservoirs with relatively poor physical properties are more conducive to the bitumen preservation.展开更多
A series of undrained triaxial tests was conducted to investigate the effect of crushed mudstone with the immersion-induced degradation on the liquefaction and post-liquefaction properties,and the undrained shearing b...A series of undrained triaxial tests was conducted to investigate the effect of crushed mudstone with the immersion-induced degradation on the liquefaction and post-liquefaction properties,and the undrained shearing behavior without precedent cyclic-loading histories of sands containing crushed mudstone.The tested materials with a main particle diameter of 2-0.85 mm were prepared by mixing sands and crushed mudstone to reach the prescribed mudstone content defined by dry mass ranging from 0% to 50%.The mixtures were subjected to immersion under a certain stress level and were subsequently tested.In addition,one-dimensional compression tests were also supplementally performed to visually observe the immersion-induced degradation of crushed mudstone.The test results mainly showed that: (1) the liquefaction resistance,the post-liquefaction undrained strength,and the undrained strength without a precedent cyclic-loading history decreased significantly with increasing mudstone content,M c ,up to 20%;(2) even a small amount of crushed mudstone affected these strengths;(3) the above-mentioned large reductions in the strengths were attributed to the immersion-induced degradation of crushed mudstone;(4) at M_(c) >20%,the liquefaction resistance increased while the significant increase in the undrained static strengths with and without precedent cyclic-loading histories was not observed;and (5) the increase in the liquefaction resistance at M_(c) >20% may have been attributed to both the gradual increase in the plasticity and the formation of the soil aggregates among deteriorated crushed mudstone,while the increase in the specimen density did not play an important role in such behavior.展开更多
The sand bars, in perpetual transformation, observable in the middle course of the Kasai river on the section between the city of Ilebo (pk605) to the confluence of the Loange river (pk525), pose enormous navigability...The sand bars, in perpetual transformation, observable in the middle course of the Kasai river on the section between the city of Ilebo (pk605) to the confluence of the Loange river (pk525), pose enormous navigability problems. This may be dependent on hydrosedimentological characteristics of the Kasai River. This abundance of sand thus conditions the morphology of the middle course of the Kasai River in the section under our study. It therefore constitutes sedimentary navigation obstacles. The objective of this study is the granulometric and mineralogical characterization of the bar sands of the Kasai River in this study section. Particle size analyzes reveal these are moderately well classified to well classified unimodal sands (Classification coefficient between 1.29 to 1.742) largely presenting grain size symmetry and rarely fine asymmetry (Asymmetry coefficient—Skewness between −0.197 to 0.069) with mesorkurtic and rarely leptokurtic and platykurtic acuity (Angulosity coefficient—Kurtosis between 0.814 to 1.323). All these parameters evolve in sawtooth patterns from upstream to downstream. And then, an automated mineralogical analysis of the sands of the Kasaï River using a Qemscan FEG Quanta 650 made it possible to determine a very varied mineralogical procession with a sawtooth evolution. It is largely dominated by quartz (between 93.73% and 99.07%), followed by calcite (0.01% - 2.66%), iron oxides (0.01% - 1.88%), orthoclase (0.04% - 0.99%), plagioclase (0.01% - 0.75%) and Kaolinite (0.18% - 0.71%). Finally, this mineralogical procession is characterized by a group of minerals which do not reach the threshold of 0.55% such as: illite, apatite, ilmenite, muscovite, chlorite, biotite, montmorillonite, rutile, pyrophyllite, siderite, zircon and dolomite. The evolution of the mineralogical procession of the sands of the bars is not as clear as in the case of particle size parameters.展开更多
The depositional environment of the sands of the cover formation is discussed. This study aims to determine the paleoenvironments of deposition of the sands of the cover formation in the Batéké Plateaus by s...The depositional environment of the sands of the cover formation is discussed. This study aims to determine the paleoenvironments of deposition of the sands of the cover formation in the Batéké Plateaus by studying sedimentary dynamics based on the description of lithological facies in the field and granulometric analyses in the laboratory. In the field, six (6) lithostratigraphic logs were surveyed and 42 sand samples were taken for laboratory analysis. In the laboratory, the samples underwent granulometric, sieving and sedimentometry analyses, after washing with running water using a 63 µm sieve. These analyses made it possible to determine the granulometric classes of the samples. The sieving results allowed to determine the granulometric parameters (mean, standard deviation, mode, median, skewness, flattening or kurtosis) using the method of moments with the software “Gradistat V.8”, granulometric parameters with which the granulometric facies, the mode of transport and the deposition environment were determined using the diagrams. Morphoscopy made it possible to determine the form and aspect of the surface of the quartz grains constituting these sands. Granulometric analyses show that these silty-clay or clayey-silty sands are fine sands and rarely medium sands, moderately to well sorted and rarely well sorted. The dominant granulometric facies is hyperbolic (sigmoid), with parabolic facies being rare. The primary mode of transport of these sands is saltation, which dominates rolling. The dispersion of points in the diagrams shows that these sands originate from two depositional environments: aeolian and fluvial. Morphoscopic analysis reveals the presence of clean rounded matt grains (RM), dirty rounded matt grains (RS), shiny blunt grains (EL) and shiny rounded grains (RL). The rounded matt grains exhibit several impact marks. The presence of dirty rounded grains with a ferruginous cement on their surface indicates that these sands have been reworked. These sands have undergone two types of transport, first by wind (aeolian environment) and then by water (fluvial environment).展开更多
Darcy’s law is widely used to describe the flow in porous media in which there is a linear relationship between fluid velocity and pressure gradient. However, it has been found that for high numbers of Reynolds this ...Darcy’s law is widely used to describe the flow in porous media in which there is a linear relationship between fluid velocity and pressure gradient. However, it has been found that for high numbers of Reynolds this law ceases to be valid. In this work, the Ergun equation is employed to consider the non-linearity of air velocity with the pressure gradient in casting sands. The contribution of non-linearity to the total flow in terms of a variable defined as a non-Darcy flow fraction is numerically quantified. In addition, the influence of the shape factor of the sand grains on the non-linear flow fraction is analyzed. It is found that for values of the Reynolds number less or equal than 1, the contribution of non-linearity for spherical particles is around 1.15%.展开更多
Faced with the proliferation of quarries extracting silty sand and river sand used in the building and public works sector in Togo, recognition of the granular properties of these materials remains a major challenge f...Faced with the proliferation of quarries extracting silty sand and river sand used in the building and public works sector in Togo, recognition of the granular properties of these materials remains a major challenge for builders. This study aims to take stock of the use of sand in construction in Togo. One hundred and eighteen (118) sand quarries in operation, including thirty-eight (38) silty sand quarries and eighty (80) river sand quarries, were identified following surveys carried out among stakeholders involved in the chain of construction on 40% of the national territory. It appears from these surveys that river sands (59.43% to 84.68%) are prioritized over silty sands (15.32% to 40.57%). Three (3) main reasons are behind the choice of sand type;namely, proximity (28%), cleanliness (25%), good appearance (25%). These three (03) reasons partly explain the strong dependence of users on the sands located in their vicinity as well as the related expenses. Thus, making data available on the characteristics of sand, the materials most used in construction in Togo, would contribute to improving the housing conditions of the Togolese population. .展开更多
The sand-dust weather has become an environmental hazard in the world.However,it is still a challenge to control sandstorms and decrease sand-dust weather.The biomineralization technology for solidifying desert sands ...The sand-dust weather has become an environmental hazard in the world.However,it is still a challenge to control sandstorms and decrease sand-dust weather.The biomineralization technology for solidifying desert sands has been developed as a novel method in recent years.In this study,the wind erosion tests and verification tests of the sand solidification system were conducted via a series of laboratory experiments.The effects of sand barriers,injecting volume and concentration of the biochemical solution in the sandstorm protection were studied.Moreover,a field test of 60,000 square metres was conducted in the solidification area on both sides of the Wuma Highway in the Tengri Desert.The biomineralization technique was used to solidify sand to prevent the wind from blowing quicksand onto the newly built highway and causing accidents.Results demonstrated that the biomineralization sand solidification method had a good solidification==effect,improved the survival rate,and promoted the growth of plants in the desert.This innovative biomineralization technology is an environmentally responsible technology to control sandstorm disasters.展开更多
Natural minerals,abundant and easily obtained through simple physical processing,offer a cost-effective and environmentally friendly solution for dyeing wastewater disposal and air pollution treatment.This study inves...Natural minerals,abundant and easily obtained through simple physical processing,offer a cost-effective and environmentally friendly solution for dyeing wastewater disposal and air pollution treatment.This study investigates the photocatalytic removal of NO using natural different types of dyes,loaded on natural sand,under visible light illumination.By examining various coating concentrations of dyes and sand weights,we discovered that sand loaded with Rhodamine B(RhB)exhibits high activity for the photo-oxidation of NO.A combination results of X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FTIR)and thermogravimetric(TG)analyses confirm the presence of SiO_(2),CaCO_(3),Al_(2)O_(3)and iron oxides as the main components of the sand.Furthermore,studying RhB-loaded individual components reveals that CaCO_(3)plays a crucial role in enhancing the NO removal rate.Experimental results and theoretical calculations demonstrate the establishment of a directional charge transfer channel from CaCO_(3)to RhB,facilitating the adsorption and activation of molecular NO and O_(2).This work not only promotes the utilization of natural mineral resources but also enriches the fields of environmental photochemistry and semiconductor photocatalysis.展开更多
The Nigerian oil sands represent the largest oil sand deposit in Africa, yet there is little published information on the distribution and potential health and ecological risks of trace elements in the oil resource. I...The Nigerian oil sands represent the largest oil sand deposit in Africa, yet there is little published information on the distribution and potential health and ecological risks of trace elements in the oil resource. In the present study, we investigated the distribution pattern of 18trace elements(including biophile and chalcophile elements) as well as the estimated risks associated with exposure to these elements. The results of the study indicated that Fe was the most abundant element, with a mean concentration of 22,131 mg/kg while Br had the lowest mean concentration of 48 mg/kg. The high occurrence of Fe and Ti suggested a possible occurrence of ilmenite(Fe TiO_(3)) in the oil sands. Source apportionment using positive matrix factorization showed that the possible sources of detected elements in the oil sands were geogenic, metal production, and crustal. The contamination factor, geo-accumulation index, modified degree of contamination, pollution load index, and Nemerow pollution index indicated that the oil sands are heavily polluted by the elements. Health risk assessment showed that children were relatively more susceptible to the potentially toxic elements in the oil sands principally via ingestion exposure route(HQ > 1E-04). Cancer risks from inhalation are unlikely due to CR < 1E-06 but ingestion and dermal contact pose severe risks(CR > 1E-04). The high concentrations of the elements pose serious threats due to the potential for atmospheric transport, bioaccessibility, and bioavailability.展开更多
Water and sand leakage disasters are likely to occur during construction in water-rich sand layer areas,resulting in ground collapse.The stress-strain action characteristics of discontinuous graded sand under differen...Water and sand leakage disasters are likely to occur during construction in water-rich sand layer areas,resulting in ground collapse.The stress-strain action characteristics of discontinuous graded sand under different internal erosion degrees,and the evolution mechanism of water and sand leakage disasters caused by the internal erosion need to be further explored.Therefore,this paper takes the discontinuous graded sand in a water rich sand layer area in Nanchang City of China as the research object.Considering the influence of different fine particle losses(0,10%,20%and 30%)under the internal erosion of sand,the salt solution method is used to realize the specified loss of fine particles in the internal erosion.The stress-strain behavior after the loss of fine particles due to internal erosion is studied by triaxial shear test.Meanwhile,the physical model test and PFC-CFD method are both used to study the evolution rules of water and sand leakage disaster considered the influence of internal erosion degrees.Results show that:(1)under the same confining pressure,the peak failure strength of sand samples decreases along with the increase of fine particle loss.(2)In the water and sand leakage test of saturated sand,a natural filter channel is formed above the observed soil arch.The greater the loss of fine particles,the steeper and wider the collapse settlement area.(3)The relationship between the cumulative amount of water and sand leakage and time is nonlinear.The total mass loss of sand increases along with the increase of internal erosion degree.(4)After the soil arch is formed around the damaged opening,the sand continues to converge above the soil arch under the action of water flow,resulting in the dense convergence of contact force chains.展开更多
Bamendou (West Cameroon), has a huge potential in natural resources, especially sands. However, the use of these materials in civil engineering works leads to the appearance of numerous pathologies which in some cases...Bamendou (West Cameroon), has a huge potential in natural resources, especially sands. However, the use of these materials in civil engineering works leads to the appearance of numerous pathologies which in some cases lead to the total ruin of the works. In order to overcome these infrastructural problems, the main objective of this study is set at the improvement of the service life of structures built in Cameroon using local materials formed under climatic, geological and geotechnical conditions similar to those of materials in Bamendou. Eight sand samples were taken from the most representative and exploited quarries. The identification and classification of the sand taken from the most representative quarries in the study area show that they are mainly clayey, with an average sand equivalent of 57.54. In terms of granulometry, the curves of several sand samples do not fall within the granular range of sands used in the formulation of concrete. The modulus of fineness obtained by particle size analysis varies from 2.91 to 3.92 with an average of 3.31.展开更多
[Objective] To study the soil texture, water storage and related spectral characteristics of composited soil. [Method] 3 different ratios of composited soils was designed by using feldspathic sandstone and sand by 3 d...[Objective] To study the soil texture, water storage and related spectral characteristics of composited soil. [Method] 3 different ratios of composited soils was designed by using feldspathic sandstone and sand by 3 different ratios, 1：1（C1）, 1：2（C2） and 1：5（C3）, and the CK used loess soil and sand by 1：2, then the soil texture, water storage, soil and winter wheat spectral characteristic were measured and analyzed under those treatments in 2010-2013. [Result] （1） With the increasing of the plant- ing year, treatment C1, C2 and C3 all showed decreasing in the proportions of sand and increasing of silt and the CK showed decreasing of clay and increasing of sand, along 1-30 cm soil depth. Treatment C2 showed the proportion of sand, silt and clay were 76.69%, 18.72% and 4.70%, respectively. （2） The water contents of all the treatments were significant different from other in 0-60 cm soil depth, and showed increasing trend with the increasing of sand proportion. Treatment C2 had higher average water content during the 3 years than treatment CK, C1 and C3 by 21.34%, 11.59% and 3.91% in the same soil depth, respectively. （3） In 2013, the spectral reflection curve characters were similar for all treatment of winter wheat at the jointing stage and filling stage along the full-wave band （350-2 500 nm）, and the reflectance was higher in the jointing stage than the filling stage; the reflection peak was found around 550 nm, a part of green light wave band. Treatment C2 showed the highest canopy that all treatments had similar spectral curves, and the relative reflectance of soil increased during 350-1 750 nm wave length along with the increase of the sand proportion; for treatment CK, C1, C2 and C3, the soil spectral reflectance （y） and wave length （x） appeared highly correlated relationships, they were y=0.18 71 In（x）-0.979 4, y=0.158 7 In（x）-0.801 2, y=0.177 1 In（x）-0.910 8 and y=0.184 5 In（x）-0.944 5, respectively. [Conclusion] Synthesizing the soil physical properties and related spectral character indices, treatment C2 generated the best combination ratio of feldspathic sandstone and sand.展开更多
The ruin of several civil engineering works occurs due to shear rupture of the ground. When the stress is greater than the shear resistance, the internal friction angle and the cohesion of the soil loosen and rupture ...The ruin of several civil engineering works occurs due to shear rupture of the ground. When the stress is greater than the shear resistance, the internal friction angle and the cohesion of the soil loosen and rupture occurs. Cement and lime are often used to stabilize soils and improve soil strength. The costs and environmental problems of these technologies raise concerns and challenge researchers to innovate with clean, inexpensive materials, accessible to the most disadvantaged social classes. The question that this study seeks to answer is whether the binders derived from plant tannins, which also stabilize soils, improve the shear resistance of these soils. To do this, we determined for silty sand the shear parameters, notably the cohesion and the angle of internal friction in the non-stabilized state and when they are stabilized with the powder of the bark of the Bridelia under different water states. The results show that the addition of Bridelia powder to silty sand increases the cohesion of the soil by nearly 70.71% and the friction angle by 4.31%. But in unfavourable water conditions, the cohesion and internal friction angle of the silty sand material improved with Bridelia bark powder drops drastically by nearly 81.56%. but does not dissolve completely as for the same material. When it is not stabilized. This information is an invaluable contribution in the search for solutions to increase the durability of earthen constructions by improving the water-repellent properties of soils.展开更多
The repose angle is one of the most significant macroscopic parameters in describing the behavior of granular materials. Under a static condition, the repose angle is the steepest angle at which sediment particles can...The repose angle is one of the most significant macroscopic parameters in describing the behavior of granular materials. Under a static condition, the repose angle is the steepest angle at which sediment particles can rest without motion. In this paper, we use existing data and aeolian physics to analyze the main factors that influence the repose angle of sand dunes, and we investigate different repose angles involving various states and types of materials. We have determined that different factors have differential influence on the magnitude of the repose angle. Our results show that for powdery （〈400-μm diameter） desert sands, the main influential factor on the magnitude of repose angle is the molecular force among particles. Particle size does not influence the repose angle of desert sands directly, but has an indirect impact by affecting the grit sphericity and surface roughness, of which the grit sphericity acts as a major factor. Even at the same average particle size, the repose angle differs with different grain compositions. Furthermore, with increasing unevenness in grain composition, the repose angle increases correspondingly. Sand texture also has a direct influence on the repose angle of desert sands. In two sand samples having the same grain composition but different textures, the repose angles may be different. Water content has a stronger influence on the repose angle than any other factor. However, the relationship between the repose angle and water content is not a simple direct proportion. In fact, with increasing water content, the repose angle first increases and then decreases. These research results will be useful for understanding the mechanisms of dune transport, variations of dune morphology, and the stability and fluidity of dune sands.展开更多
文摘RDV■(dynamic vasoactive reactor)chemical technology represents a disruptive innovation operating under both surface and downhole conditions,producing irreversible and in situ adaptable effects.It has demonstrated transformative capacity across crude oils of various API gravities,with notable impact on extra-heavy crudes and bitumens,through a mechanism based on targeted proton donation that induces selective protonation of polar structures,generating transient carbocations that catalyze molecular fragmentation.This work presents a comprehensive analysis of the effects of RDV-DMG001■treatment(currently named RDV-01L■)on bitumen samples from the Primrose field,Alberta,Canada,using capillary chromatography,SARA analysis,and rheological evaluation,complemented with comparative data on prior applications of RDV-01L■in extra-heavy crudes from Venezuela(Boscán and El Salto).Results for Primrose bitumen show an 85%reduction in viscosity(from 500,000 to 75,000 cP),an increase in API gravity from 8.5 to 15.0(+76.4%),and molecular redistribution toward medium-chain hydrocarbons(C_(13)-C_(16)),with increases in molar and mass fractions up to 39.1%and 62.3%,respectively.SARA analysis confirmed fragmentation of asphaltenes(2.0%mass reduction)and a 5.8%increase in resins,improving colloidal stability and lowering precipitation risk.These changes align with RDV■’s mechanism of action based on carbocation generation.Notably,in field conditions-which are more dynamic and energetically favorable-RDV■treatment efficacy tends to exceed laboratory results,due to synergy among temperature,pressure,and fluid flow gradients which accelerate and enhance protonation and molecular fragmentation.Validated in contexts of advanced chemical transformation(Venezuela,Canada),the technology enables substantial improvements in fluidity,transport,processing,and recovery,with significant potential for annual cost savings in extraction and processing.This study positions RDV■as a disruptive,irreversible,and in situ adaptable chemical solution superior to conventional technologies such as surfactants,nanocatalysts,or aquathermolysis.RDV■is a quantum-impact chemical technology operating via molecular protonation reactions and controlled carbocation formation.The term“quantum”is used here as a conceptual analogy to describe the magnitude and specificity of the molecular reconfiguration induced by RDV■,without asserting direct experimental evidence of quantum reactivity.
文摘In the sweltering heat of summer,a visitor to Nugusitai Town of Tongliao City,Inner Mongolia Autonomous Region,might find it hard to recognise the landscape.Once a desolate expanse of drifting sand,the hillsides are now cloaked in lush forest.Tall wind turbines rotate quietly,and wetlands glimmer between groves of forest,providing a haven for waterfowl.
基金funding support from the National Nature Science Foundation of China(Grant No.42030714).
文摘Calcareous sands are widely distributed on the coral reefs,continental shelf,and seashores between 30north and south latitude and are commonly utilized as filling materials for the construction of artificial islands and infrastructure foundations.In this study,calcareous sands were cemented by enzymatically induced carbonate precipitation(EICP)technique.Drained triaxial tests were conducted on the EICPtreated calcareous sands.Results showed that the specimens with different cementation levels exhibited different responses in mechanical behavior.The differences in the sand fabric after consolidation under a relatively high confining pressure resulted in the untreated specimen exhibiting a higher peak strength compared to the lightly cemented specimen.High confining pressures exhibited a strongly inhibiting effect on dilatancy,which could be counteracted by increasing the cementation level.The EICP-treated specimen could have one or two yield points(smaller-strain and larger-strain yields).For lightly cemented specimens,the smaller-strain yield stress decreased under high confining pressures due to the partial carbonate bonding degradation during consolidation.The stress line of untreated particle breakage(UPB)was a critical boundary to distinguish failure mode in the p′-q space.For the EICP-treated specimens,the yield stress located above or below the UPB stress line indicates the simultaneous or sequential breakage of the carbonate bonds and sand particles,respectively.Accordingly,the EICPtreated specimen exhibited brittle or ductile properties.Failure mode transformation could be triggered by increasing cementation level or confining pressure.
基金granted by the Xinjiang Geological Exploration Fund。
文摘The northwestern margin of Junggar Basin is the region with the richest oil sand resources in China.For better understanding the enrichment rules and deployment of exploration and development of regional oil sand,it is of great scientific significance to study the accumulation conditions of oil sand in different strata and mining areas of the Junggar Basin.Through a large number of field investigations,drilling verification and sampling tests,it is found that the oil sand in the region covers an area of 2000 km^(2),with shallow and thick reservoir,and predicted resource of 180 million tons.The oil sand resources are mainly distributed in four geological strata,namely the Middle Triassic Karamay Formation,Early Jurassic Badaowan Formation,Late Jurassic Qigu Formation,and Early Cretaceous Qingshuihe Formation.The reservoir is mainly composed of sandstone with high porosity and permeability,and the reservoir space is mainly intergranular pores with a medium average oil content.The oil sand deposit in the region is a typical destructive oil reservoir.The crude oil in the oil sand layer is degraded and thickened from the deep to the shallow,the content of saturated hydrocarbon decreased,and the content of aromatic hydrocarbon,non-hydrocarbon and asphaltene increased.The oil source comes from the deep Permian hydrocarbon-generating depression.Unconformities,faults and marginal fan delta-braided river depositional systems constitute effective migration and storage systems.Caprocks of the Upper Triassic Baijiantan Formation,Lower Jurassic Sangonghe Formation and Lower Cretaceous Hutubihe Formation were formed by three large scale lake transgressions.The Indosinian,Yanshan and Late Yanshan movements are the main driving forces for the migration of deep oil and gas to the shallow edge to form oil sand deposits.It is considered that the oil sand in the northwestern margin of Junggar Basin is of a slope complex migration type.
基金supported by the Académie Hassan Ⅱ des Sciences et Techniques(Rabat,Morocco)as part of the AP-2018 project.
文摘The aim of this article is to study and reveal the mineralogical composition of dune sands from the Bouarfa Figuiget region(eastern Morocco)and to find the potential source of these dune sands.The mineralogical study was made by combining field studies to collect samples and determine the facies of the surrounding area with labortory studies,including geochemical analysis(DRX analysis),morphoscopic study of the sands under a binocular magnifying glass according to the fractions making up these sands,heavy mineral extraction and analysis under a microscope,and calcimetric analysis.The results revealed two main categories of minerals in sandy deposits:light and heavy minerals.These include quartz,plagioclase feldspar,calcite platelets,and fragments of greyish,greenish,and whitish rock.Quartz was the dominant mineral.Heavy minerals include dark(opaque)minerals such as garnet,tourmaline,epidote,zircon,rutile,and rock fragments.This composition is the result of erosion,transport,and deposition processes in the crystalline sandstone and sedimentary formations of the eastern High Atlas,which feed the study area via aeolian pathways,including winds from ERG CHBI.The quartz grains in the dune sands of the eastern region,accumulated by wind action,are mainly round,matte grains of aeolian origin.The mineral associations observed show the presence of two types of sandy deposits:(1)Sand dominated by matte,round quartz grains(fraction 225μm),associated with accessory minerals(garnet,tourmaline,zircon,rutile,kyanite,and epidote),oxides(magnetite and ilmenite),and rock fragments of mixed mineral,crystalline,and sedimentary origin.(2)Totally dominant matte round quartz sand associated with iron oxides and a few rock fragments(fractions 142μm,180μm and 357μm).Sand with fraction 225μm consists almost entirely of quartz(8%)with garnets and a few rock fragments.These results suggest that the variation in the composition of the dune sands in the study area depends on the nature of the granulometric fraction studied,and therefore on the variety of sources feeding the sands studied(Chott Tigri,crystalline and sedimentary formations of the Eastern High Atlas).
基金Supported by the Key Scientific and Technological Projects of Sinopec(No.P25165).
文摘The Longfengshan structural belt lies in the southern Changling Depression.The Yingcheng Formation is the primary gas-bearing unit.The Yingcheng Formation has low permeability and contains deep,tight gas that is challenging to extract.Industrial gas flow has been achieved from the B218 and B220 well blocks in the sandstone layer of the first member of Yingcheng Formation(Ying I),indicating the potential of this sandstone group for gas production.Although oil and gas are widely distributed in the Ying I sandstone layer,production capacity varies significantly across the formation.into six sublayers.Drilling,logging,and laboratory testing data were integrated to subdivide the Ying I sandstone layer into six sublayers.Core and well logging analyses indicate a braided river delta depositional environment.Data and seismic inversion identify the Ying I-5 sublayer as the primary exploration target.The effective reservoir in the eastern fan body,where porosity ranges from 5%to 13%and maximum effective thickness reaches 34 m.This study basis for optimizing well placement and estimating gas reserve parameters in the Ying I sandstone layer of the Longfengshan area.The findings can guide the development of other tight gas reservoirs.
基金sponsored by Major Science and Technology Special Project of CNPC(Grant No.2023ZZ07)。
文摘The Lower Cretaceous Manville Group of Upper Mc Murray Formation is one of the main bitumen reservoirs in Athabasca.In this study,the relationship between reservoirs heterogeneity and bitumen geochemical characteristics were analyzed through core and microscopic observation,lab analysis,petrophysics and logging data.Based on the sedimentology framework,the formation environment of high-quality oil sand reservoirs and their significance for development were discussed.The results indicate that four types lithofacies were recognized in the Upper Mc Murray Formation based on their depositional characteristics.Each lithofacies reservoirs has unique physical properties,and is subject to varying degrees of degradation,resulting in diversity of bitumen content and geochemical composition.The tidal bar(TB)or tidal channel(TC)facies reservoir have excellent physical properties,which are evaluated as gas or water intervals due to strong degradation.The reservoir of sand bar(SB)facies was evaluated as oil intervals,due to its poor physical properties and weak degradation.The reservoir of mixed flat(MF)facies is composed of sand intercalated with laminated shale,which is evaluated as poor oil intervals due to its poor connectivity.The shale content in oil sand reservoir is very important for the reservoir physical properties and bitumen degradation degree.In the context of regional biodegradation,oil sand reservoirs with good physical properties will suffer from strong degradation,while oil sand reservoirs with relatively poor physical properties are more conducive to the bitumen preservation.
基金financially supported by JSPS KAKENHI Grant Number JP19K15083.
文摘A series of undrained triaxial tests was conducted to investigate the effect of crushed mudstone with the immersion-induced degradation on the liquefaction and post-liquefaction properties,and the undrained shearing behavior without precedent cyclic-loading histories of sands containing crushed mudstone.The tested materials with a main particle diameter of 2-0.85 mm were prepared by mixing sands and crushed mudstone to reach the prescribed mudstone content defined by dry mass ranging from 0% to 50%.The mixtures were subjected to immersion under a certain stress level and were subsequently tested.In addition,one-dimensional compression tests were also supplementally performed to visually observe the immersion-induced degradation of crushed mudstone.The test results mainly showed that: (1) the liquefaction resistance,the post-liquefaction undrained strength,and the undrained strength without a precedent cyclic-loading history decreased significantly with increasing mudstone content,M c ,up to 20%;(2) even a small amount of crushed mudstone affected these strengths;(3) the above-mentioned large reductions in the strengths were attributed to the immersion-induced degradation of crushed mudstone;(4) at M_(c) >20%,the liquefaction resistance increased while the significant increase in the undrained static strengths with and without precedent cyclic-loading histories was not observed;and (5) the increase in the liquefaction resistance at M_(c) >20% may have been attributed to both the gradual increase in the plasticity and the formation of the soil aggregates among deteriorated crushed mudstone,while the increase in the specimen density did not play an important role in such behavior.
文摘The sand bars, in perpetual transformation, observable in the middle course of the Kasai river on the section between the city of Ilebo (pk605) to the confluence of the Loange river (pk525), pose enormous navigability problems. This may be dependent on hydrosedimentological characteristics of the Kasai River. This abundance of sand thus conditions the morphology of the middle course of the Kasai River in the section under our study. It therefore constitutes sedimentary navigation obstacles. The objective of this study is the granulometric and mineralogical characterization of the bar sands of the Kasai River in this study section. Particle size analyzes reveal these are moderately well classified to well classified unimodal sands (Classification coefficient between 1.29 to 1.742) largely presenting grain size symmetry and rarely fine asymmetry (Asymmetry coefficient—Skewness between −0.197 to 0.069) with mesorkurtic and rarely leptokurtic and platykurtic acuity (Angulosity coefficient—Kurtosis between 0.814 to 1.323). All these parameters evolve in sawtooth patterns from upstream to downstream. And then, an automated mineralogical analysis of the sands of the Kasaï River using a Qemscan FEG Quanta 650 made it possible to determine a very varied mineralogical procession with a sawtooth evolution. It is largely dominated by quartz (between 93.73% and 99.07%), followed by calcite (0.01% - 2.66%), iron oxides (0.01% - 1.88%), orthoclase (0.04% - 0.99%), plagioclase (0.01% - 0.75%) and Kaolinite (0.18% - 0.71%). Finally, this mineralogical procession is characterized by a group of minerals which do not reach the threshold of 0.55% such as: illite, apatite, ilmenite, muscovite, chlorite, biotite, montmorillonite, rutile, pyrophyllite, siderite, zircon and dolomite. The evolution of the mineralogical procession of the sands of the bars is not as clear as in the case of particle size parameters.
文摘The depositional environment of the sands of the cover formation is discussed. This study aims to determine the paleoenvironments of deposition of the sands of the cover formation in the Batéké Plateaus by studying sedimentary dynamics based on the description of lithological facies in the field and granulometric analyses in the laboratory. In the field, six (6) lithostratigraphic logs were surveyed and 42 sand samples were taken for laboratory analysis. In the laboratory, the samples underwent granulometric, sieving and sedimentometry analyses, after washing with running water using a 63 µm sieve. These analyses made it possible to determine the granulometric classes of the samples. The sieving results allowed to determine the granulometric parameters (mean, standard deviation, mode, median, skewness, flattening or kurtosis) using the method of moments with the software “Gradistat V.8”, granulometric parameters with which the granulometric facies, the mode of transport and the deposition environment were determined using the diagrams. Morphoscopy made it possible to determine the form and aspect of the surface of the quartz grains constituting these sands. Granulometric analyses show that these silty-clay or clayey-silty sands are fine sands and rarely medium sands, moderately to well sorted and rarely well sorted. The dominant granulometric facies is hyperbolic (sigmoid), with parabolic facies being rare. The primary mode of transport of these sands is saltation, which dominates rolling. The dispersion of points in the diagrams shows that these sands originate from two depositional environments: aeolian and fluvial. Morphoscopic analysis reveals the presence of clean rounded matt grains (RM), dirty rounded matt grains (RS), shiny blunt grains (EL) and shiny rounded grains (RL). The rounded matt grains exhibit several impact marks. The presence of dirty rounded grains with a ferruginous cement on their surface indicates that these sands have been reworked. These sands have undergone two types of transport, first by wind (aeolian environment) and then by water (fluvial environment).
文摘Darcy’s law is widely used to describe the flow in porous media in which there is a linear relationship between fluid velocity and pressure gradient. However, it has been found that for high numbers of Reynolds this law ceases to be valid. In this work, the Ergun equation is employed to consider the non-linearity of air velocity with the pressure gradient in casting sands. The contribution of non-linearity to the total flow in terms of a variable defined as a non-Darcy flow fraction is numerically quantified. In addition, the influence of the shape factor of the sand grains on the non-linear flow fraction is analyzed. It is found that for values of the Reynolds number less or equal than 1, the contribution of non-linearity for spherical particles is around 1.15%.
文摘Faced with the proliferation of quarries extracting silty sand and river sand used in the building and public works sector in Togo, recognition of the granular properties of these materials remains a major challenge for builders. This study aims to take stock of the use of sand in construction in Togo. One hundred and eighteen (118) sand quarries in operation, including thirty-eight (38) silty sand quarries and eighty (80) river sand quarries, were identified following surveys carried out among stakeholders involved in the chain of construction on 40% of the national territory. It appears from these surveys that river sands (59.43% to 84.68%) are prioritized over silty sands (15.32% to 40.57%). Three (3) main reasons are behind the choice of sand type;namely, proximity (28%), cleanliness (25%), good appearance (25%). These three (03) reasons partly explain the strong dependence of users on the sands located in their vicinity as well as the related expenses. Thus, making data available on the characteristics of sand, the materials most used in construction in Togo, would contribute to improving the housing conditions of the Togolese population. .
基金supported by the National Natural Science Foundation of China(No.52173248).
文摘The sand-dust weather has become an environmental hazard in the world.However,it is still a challenge to control sandstorms and decrease sand-dust weather.The biomineralization technology for solidifying desert sands has been developed as a novel method in recent years.In this study,the wind erosion tests and verification tests of the sand solidification system were conducted via a series of laboratory experiments.The effects of sand barriers,injecting volume and concentration of the biochemical solution in the sandstorm protection were studied.Moreover,a field test of 60,000 square metres was conducted in the solidification area on both sides of the Wuma Highway in the Tengri Desert.The biomineralization technique was used to solidify sand to prevent the wind from blowing quicksand onto the newly built highway and causing accidents.Results demonstrated that the biomineralization sand solidification method had a good solidification==effect,improved the survival rate,and promoted the growth of plants in the desert.This innovative biomineralization technology is an environmentally responsible technology to control sandstorm disasters.
基金financially supported by the National Natural Science Foundation of China(Nos.52370109,51808080 and 21707036)China Postdoctoral Science Foundation(No.2022M710830)+8 种基金the Venture and Innovation Support Program for Chongqing Overseas Returnees(No.cx2022005)the Natural Scienceof CQ CSTC(No.CSTB2022NSCQMSX1267)Chongqing Natural Science Postdoctoral Fund(No.cstc2019jcyj-bsh0107)the Research Project of Chongqing Education Commission Foundation(Nos.KJQN201800826,KJQN202000818 and KJQN202200830&KJQN201800840)the Science and Technology Research Program of Chongqing Municipal Education Commission of China(No.KJZD-K202100801)the Post-doctoral Program Funded by Chongqing,Chongqing University Innovation Research Group project(No.CXQT21023)the High Level Talent Scientific Research Startup Project of Chongqing Technology and Business University(No.1956044)support from FCT/MCTES(Fundacao para a Ciência e Tecnologia and Ministério da Ciência,Tecnologia e Ensino Superior)(Nos.UIDB/50006/2020 and UIDP/50006/2020)for the Scientific Employment Stimulus-Institutional Call(No.CEECINST/00102/2018)。
文摘Natural minerals,abundant and easily obtained through simple physical processing,offer a cost-effective and environmentally friendly solution for dyeing wastewater disposal and air pollution treatment.This study investigates the photocatalytic removal of NO using natural different types of dyes,loaded on natural sand,under visible light illumination.By examining various coating concentrations of dyes and sand weights,we discovered that sand loaded with Rhodamine B(RhB)exhibits high activity for the photo-oxidation of NO.A combination results of X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FTIR)and thermogravimetric(TG)analyses confirm the presence of SiO_(2),CaCO_(3),Al_(2)O_(3)and iron oxides as the main components of the sand.Furthermore,studying RhB-loaded individual components reveals that CaCO_(3)plays a crucial role in enhancing the NO removal rate.Experimental results and theoretical calculations demonstrate the establishment of a directional charge transfer channel from CaCO_(3)to RhB,facilitating the adsorption and activation of molecular NO and O_(2).This work not only promotes the utilization of natural mineral resources but also enriches the fields of environmental photochemistry and semiconductor photocatalysis.
文摘The Nigerian oil sands represent the largest oil sand deposit in Africa, yet there is little published information on the distribution and potential health and ecological risks of trace elements in the oil resource. In the present study, we investigated the distribution pattern of 18trace elements(including biophile and chalcophile elements) as well as the estimated risks associated with exposure to these elements. The results of the study indicated that Fe was the most abundant element, with a mean concentration of 22,131 mg/kg while Br had the lowest mean concentration of 48 mg/kg. The high occurrence of Fe and Ti suggested a possible occurrence of ilmenite(Fe TiO_(3)) in the oil sands. Source apportionment using positive matrix factorization showed that the possible sources of detected elements in the oil sands were geogenic, metal production, and crustal. The contamination factor, geo-accumulation index, modified degree of contamination, pollution load index, and Nemerow pollution index indicated that the oil sands are heavily polluted by the elements. Health risk assessment showed that children were relatively more susceptible to the potentially toxic elements in the oil sands principally via ingestion exposure route(HQ > 1E-04). Cancer risks from inhalation are unlikely due to CR < 1E-06 but ingestion and dermal contact pose severe risks(CR > 1E-04). The high concentrations of the elements pose serious threats due to the potential for atmospheric transport, bioaccessibility, and bioavailability.
基金funded by the Natural Science Foundation of China(No.41962015).
文摘Water and sand leakage disasters are likely to occur during construction in water-rich sand layer areas,resulting in ground collapse.The stress-strain action characteristics of discontinuous graded sand under different internal erosion degrees,and the evolution mechanism of water and sand leakage disasters caused by the internal erosion need to be further explored.Therefore,this paper takes the discontinuous graded sand in a water rich sand layer area in Nanchang City of China as the research object.Considering the influence of different fine particle losses(0,10%,20%and 30%)under the internal erosion of sand,the salt solution method is used to realize the specified loss of fine particles in the internal erosion.The stress-strain behavior after the loss of fine particles due to internal erosion is studied by triaxial shear test.Meanwhile,the physical model test and PFC-CFD method are both used to study the evolution rules of water and sand leakage disaster considered the influence of internal erosion degrees.Results show that:(1)under the same confining pressure,the peak failure strength of sand samples decreases along with the increase of fine particle loss.(2)In the water and sand leakage test of saturated sand,a natural filter channel is formed above the observed soil arch.The greater the loss of fine particles,the steeper and wider the collapse settlement area.(3)The relationship between the cumulative amount of water and sand leakage and time is nonlinear.The total mass loss of sand increases along with the increase of internal erosion degree.(4)After the soil arch is formed around the damaged opening,the sand continues to converge above the soil arch under the action of water flow,resulting in the dense convergence of contact force chains.
文摘Bamendou (West Cameroon), has a huge potential in natural resources, especially sands. However, the use of these materials in civil engineering works leads to the appearance of numerous pathologies which in some cases lead to the total ruin of the works. In order to overcome these infrastructural problems, the main objective of this study is set at the improvement of the service life of structures built in Cameroon using local materials formed under climatic, geological and geotechnical conditions similar to those of materials in Bamendou. Eight sand samples were taken from the most representative and exploited quarries. The identification and classification of the sand taken from the most representative quarries in the study area show that they are mainly clayey, with an average sand equivalent of 57.54. In terms of granulometry, the curves of several sand samples do not fall within the granular range of sands used in the formulation of concrete. The modulus of fineness obtained by particle size analysis varies from 2.91 to 3.92 with an average of 3.31.
基金Supported by the Special Fund for the Scientific Research in Public Interest of the Ministry of Land and Resources(201411008)~~
文摘[Objective] To study the soil texture, water storage and related spectral characteristics of composited soil. [Method] 3 different ratios of composited soils was designed by using feldspathic sandstone and sand by 3 different ratios, 1：1（C1）, 1：2（C2） and 1：5（C3）, and the CK used loess soil and sand by 1：2, then the soil texture, water storage, soil and winter wheat spectral characteristic were measured and analyzed under those treatments in 2010-2013. [Result] （1） With the increasing of the plant- ing year, treatment C1, C2 and C3 all showed decreasing in the proportions of sand and increasing of silt and the CK showed decreasing of clay and increasing of sand, along 1-30 cm soil depth. Treatment C2 showed the proportion of sand, silt and clay were 76.69%, 18.72% and 4.70%, respectively. （2） The water contents of all the treatments were significant different from other in 0-60 cm soil depth, and showed increasing trend with the increasing of sand proportion. Treatment C2 had higher average water content during the 3 years than treatment CK, C1 and C3 by 21.34%, 11.59% and 3.91% in the same soil depth, respectively. （3） In 2013, the spectral reflection curve characters were similar for all treatment of winter wheat at the jointing stage and filling stage along the full-wave band （350-2 500 nm）, and the reflectance was higher in the jointing stage than the filling stage; the reflection peak was found around 550 nm, a part of green light wave band. Treatment C2 showed the highest canopy that all treatments had similar spectral curves, and the relative reflectance of soil increased during 350-1 750 nm wave length along with the increase of the sand proportion; for treatment CK, C1, C2 and C3, the soil spectral reflectance （y） and wave length （x） appeared highly correlated relationships, they were y=0.18 71 In（x）-0.979 4, y=0.158 7 In（x）-0.801 2, y=0.177 1 In（x）-0.910 8 and y=0.184 5 In（x）-0.944 5, respectively. [Conclusion] Synthesizing the soil physical properties and related spectral character indices, treatment C2 generated the best combination ratio of feldspathic sandstone and sand.
文摘The ruin of several civil engineering works occurs due to shear rupture of the ground. When the stress is greater than the shear resistance, the internal friction angle and the cohesion of the soil loosen and rupture occurs. Cement and lime are often used to stabilize soils and improve soil strength. The costs and environmental problems of these technologies raise concerns and challenge researchers to innovate with clean, inexpensive materials, accessible to the most disadvantaged social classes. The question that this study seeks to answer is whether the binders derived from plant tannins, which also stabilize soils, improve the shear resistance of these soils. To do this, we determined for silty sand the shear parameters, notably the cohesion and the angle of internal friction in the non-stabilized state and when they are stabilized with the powder of the bark of the Bridelia under different water states. The results show that the addition of Bridelia powder to silty sand increases the cohesion of the soil by nearly 70.71% and the friction angle by 4.31%. But in unfavourable water conditions, the cohesion and internal friction angle of the silty sand material improved with Bridelia bark powder drops drastically by nearly 81.56%. but does not dissolve completely as for the same material. When it is not stabilized. This information is an invaluable contribution in the search for solutions to increase the durability of earthen constructions by improving the water-repellent properties of soils.
基金supported by the National Natural Science Foundation of China (Grant No. 50879033)the National Science Fund for Fostering Talents in Basic Research of the National Natural Science Foundation of China (Grant No.J0730536)
文摘The repose angle is one of the most significant macroscopic parameters in describing the behavior of granular materials. Under a static condition, the repose angle is the steepest angle at which sediment particles can rest without motion. In this paper, we use existing data and aeolian physics to analyze the main factors that influence the repose angle of sand dunes, and we investigate different repose angles involving various states and types of materials. We have determined that different factors have differential influence on the magnitude of the repose angle. Our results show that for powdery （〈400-μm diameter） desert sands, the main influential factor on the magnitude of repose angle is the molecular force among particles. Particle size does not influence the repose angle of desert sands directly, but has an indirect impact by affecting the grit sphericity and surface roughness, of which the grit sphericity acts as a major factor. Even at the same average particle size, the repose angle differs with different grain compositions. Furthermore, with increasing unevenness in grain composition, the repose angle increases correspondingly. Sand texture also has a direct influence on the repose angle of desert sands. In two sand samples having the same grain composition but different textures, the repose angles may be different. Water content has a stronger influence on the repose angle than any other factor. However, the relationship between the repose angle and water content is not a simple direct proportion. In fact, with increasing water content, the repose angle first increases and then decreases. These research results will be useful for understanding the mechanisms of dune transport, variations of dune morphology, and the stability and fluidity of dune sands.
