The study carried out concerns the valorization of agricultural waste for the development of biosourced materials that can be used as insulation in homes. This article is devoted to the influence of gum arabic on the ...The study carried out concerns the valorization of agricultural waste for the development of biosourced materials that can be used as insulation in homes. This article is devoted to the influence of gum arabic on the mechanical and thermal properties of clay soils in the town of Abéché. The mechanical tests were carried out using the CBR press equipped with two devices (bending device and compression device). Thermal property such as thermal conductivity was determined by the hot wire method and thermal resistance was derived by calculation. Thus, the tests were carried out on test pieces made from a mixture of clay and gum arabic in solution. The experimental program includes seven formulations (0%, 2%, 4%, 6%, 8%, 10% and 12%). The results obtained showed that the best flexural and compressive strengths are obtained by using gum arabic with a rate of 8% and a maximum stress of 4.3 MPa. In addition, the thermal results also showed that the thermal conductivity decreases when the percentage of gum arabic increases, which makes it possible to increase the thermal resistance, thus confirming the capacity of gum arabic to provide thermal insulation.展开更多
The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures an...The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.展开更多
This study introduces an advanced finite element model for the light weight deflectometer(LWD),which integrates contact mechanics with fully coupled models.By simulating LWD tests on granular soils at various saturati...This study introduces an advanced finite element model for the light weight deflectometer(LWD),which integrates contact mechanics with fully coupled models.By simulating LWD tests on granular soils at various saturation levels,the model accurately reflects the dependence of the LWD modulus on dry density,water content,and effective stress.This model addresses and overcomes the limitations of previous finite element models for this specific problem.Simultaneously,this research presents the first experimentally validated fully coupled contact impact model.Furthermore,the research provides a comparative assessment of elastoplastic and nonlinear elastic models and contrasts an enriched node-tosegment method(developed in this study)with the more precise mortar technique for contact mechanics.These comparisons reveal unique advantages and challenges for each method.Moreover,the study underscores the importance of careful application of the LWD modulus,emphasising the need for sophisticated tools to interpret soil behaviour accurately.展开更多
After landing in the Utopia Planitia,Tianwen-1 formed the deepest landing crater on Mars,approximately 40 cm deep,exposing precious information about the mechanical properties of Martian soil.We established numerical ...After landing in the Utopia Planitia,Tianwen-1 formed the deepest landing crater on Mars,approximately 40 cm deep,exposing precious information about the mechanical properties of Martian soil.We established numerical models for the plume-surface interaction(PSI)and the crater formation based on Computational Fluid Dynamics(CFD)methods and the erosion model modified from Roberts’Theory.Comparative studies of cases were conducted with different nozzle heights and soil mechanical properties.The increase in cohesion and internal friction angle leads to a decrease in erosion rate and maximum crater depth,with the cohesion having a greater impact.The influence of the nozzle height is not clear,as it interacts with the position of the Shock Diamond to jointly control the erosion process.Furthermore,we categorized the evolution of landing craters into the dispersive and the concentrated erosion modes based on the morphological characteristics.Finally,we estimated the upper limits of the Martian soil’s mechanical properties near Tianwen-1 landing site,with the cohesion ranging from 2612 to 2042 Pa and internal friction angle from 25°to 41°.展开更多
In Senegal, particularly in the Senegal River valley, agricultural mechanization remains limited, mainly due to a lack of agricultural equipment, a lack of expertise in agricultural machinery and an apprehension of th...In Senegal, particularly in the Senegal River valley, agricultural mechanization remains limited, mainly due to a lack of agricultural equipment, a lack of expertise in agricultural machinery and an apprehension of the consequences on soil quality. To better understand agricultural mechanization of rice cultivation, this survey study has been carried out in the Senegal river valley. Precisely, this work aimed to characterize farm machinery and its effects on soil and rice cultivation. A questionnaire was administered to 304 out of 1270 farmers, spread over 8 rice-growing areas, 4 of which are located in the Podor department, three in Dagana and one in Saint-Louis. The results showed that 99.3% of farmers used motorized equipment, with 95.7% using tractor and 3.6% a power tiller. Offset tillage, which is a shallow cultivation practice carried out to break up hard soil without turning it over, was most widespread among growers (95.4%). 78.3% of the valley’s farmers felt that the machinery used to carry out tillage operations was inefficient. According to the farmers, the main constraints on the use of agricultural machinery in the valley were: the upkeep and maintenance of equipment (57%), the lack of expertise in mechanization (31%), and issues adapting machinery to local conditions (12%). Those constraints have contributed to a drop in yields in recent years, the spread of weeds on cultivated plots and the gradual degradation of the soil in the area according to 78% of farmers.展开更多
The history of the formation of the alpine region is affected by the activities of the glaciers, which have a strong influence on underground works in this area. Mechanized tunneling must adapt to the presence of soun...The history of the formation of the alpine region is affected by the activities of the glaciers, which have a strong influence on underground works in this area. Mechanized tunneling must adapt to the presence of sound and altered rock, as well as to inhomogeneous soil layers that range from permeable gravel to soft clay sediments along the same tunnel. This article focuses on past experiences with tunnel-boring machines (TBMs) in Switzerland, and specifically on the aspects of soil conditioning during a passage through inhomogeneous soft soils. Most tunnels in the past were drilled using the slurry mode (SM), in which the application of different additives was mainly limited to difficult zones of high permeability and stoppages for tool change and modification. For drillings with the less common earth pressure balanced mode (EPBM), continuous foam conditioning and the additional use of polymer and bentonite have proven to be successful. The use of conditioning additives led to new challenges during separation of the slurries (for SM) and disposal of the excavated soil (for EPBM). If the disposal of chemically treated soft soil mate- rial from the earth pressure balanced (EPB) drive in a manner that is compliant with environmental legislation is considered early on in the design and evaluation of the excavation mode, the EPBM can be beneficial for tunnels bored in glacial deposits.展开更多
To reveal the deterioration mechanism and service life of concrete durability in the western saline soil area,the indoor accelerated test of the concrete specimen was simulated in the coupled environment of salt erosi...To reveal the deterioration mechanism and service life of concrete durability in the western saline soil area,the indoor accelerated test of the concrete specimen was simulated in the coupled environment of salt erosion and dry-wet cycles in the west saline soil area of China.The deterioration mechanism of concrete durability was revealed through the relative dynamic elastic modulus,relative quality evaluation parameters,SEM,and XRD evaluation indexes.Random Wiener distribution function was used for modeling life prediction.The results show that the relative dynamic elastic modulus evaluation parameter as an evaluation index of concrete durability under various environmental coupling effects is more reliable than the relative quality,there were holes and cracks in the concrete,and needle-like and layered crystals grow from the internal cracks.The corrosion products include ettringite,gypsum and other expansive crystals and non-gelling Mg(OH)_(2);the expansion stress caused by physical,chemical reaction,and temperature change under the action of drywet cycle aggravates the formation and development of cracks.The random Wiener distribution function can describe the degradation process of concrete specimen durability,and the established concrete reliability function can intuitively reflect the service life of concrete specimens.展开更多
Loess soil deposits are widely distributed in arid and semi-arid regions and constitute about 10% of land area of the world.These soils typically have a loose honeycomb-type meta-stable structure that is susceptible t...Loess soil deposits are widely distributed in arid and semi-arid regions and constitute about 10% of land area of the world.These soils typically have a loose honeycomb-type meta-stable structure that is susceptible to a large reduction in total volume or collapse upon wetting.Collapse characteristics contribute to various problems to infrastructures that are constructed on loess soils.For this reason,collapse triggering mechanism for loess soils has been of significant interest for researchers and practitioners all over the world.This paper aims at providing a state-of-the-art review on collapse mechanism with special reference to loess soil deposits.The collapse mechanism studies are summarized under three different categories,i.e.traditional approaches,microstructure approach,and soil mechanics-based approaches.The traditional and microstructure approaches for interpreting the collapse behavior are comprehensively summarized and critically reviewed based on the experimental results from the literature.The soil mechanics-based approaches proposed based on the experimental results of both compacted soils and natural loess soils are reviewed highlighting their strengths and limitations for estimating the collapse behavior.Simpler soil mechanics-based approaches with less parameters or parameters that are easy-to-determine from conventional tests are suggested for future research to better understand the collapse behavior of natural loess soils.Such studies would be more valuable for use in conventional geotechnical engineering practice applications.展开更多
The micaceous weathered granitic soil(WGS)is frequently encountered in civil engineering worldwide,unfortunately little information is available regarding how mica affects the physico-mechanical behaviors of WGS.This ...The micaceous weathered granitic soil(WGS)is frequently encountered in civil engineering worldwide,unfortunately little information is available regarding how mica affects the physico-mechanical behaviors of WGS.This study prepares reconstituted WGS with different mica contents by removing natural mica in theWGS,and then mixes it with commercial mica powders.The geotechnical behavior as well as the microstructures of the mixtures are characterized.The addition of mica enables the physical indices of WGS to be specific combinations of coarser gradation and high permeability but high Atterberg limits.However,high mica content in WGS was found to be associated with undesirable mechanical properties,including increased compressibility,disintegration,and swelling potential,as well as poor compactability and low effective frictional angle.Microstructural analysis indicates that the influence of mica on the responses of mixtures originates from the intrinsic nature of mica as well as the particle packing being formed withinWGS.Mica exists in the mixture as stacks of plates that form a spongy structure with high compressibility and swelling potential.Pores among the plates give the soil high water retention and high Atterberg limits.Large pores are also generated by soil particles with bridging packing,which enhances the permeability and water-soil interactions upon immersion.This study provides a microlevel understanding of how mica dominates the behavior of WGS and provides new insights into the effective stabilization and improvement of micaceous soils.展开更多
Yield loss(Y_(Loss)) in the ratoon crop due to crushing damage to left stubble from mechanical harvesting of the main crop is a constraint for wide adoption of mechanized rice ratooning technology.Soil drying before t...Yield loss(Y_(Loss)) in the ratoon crop due to crushing damage to left stubble from mechanical harvesting of the main crop is a constraint for wide adoption of mechanized rice ratooning technology.Soil drying before the harvest of the main crop has been proposed to overcome this problem.The objective of this study was to determine the effect of soil drying during the mid-to-late grain filling stage of the main crop on grain yield of the ratoon crop in a mechanized rice ratooning system.Field experiments were conducted to compare Y_(Loss) between light(LD) and heavy(HD) soil drying treatments in Hubei province,central China in 2017 and 2018.Y_(Loss) was calculated as the percentage of yield reduction in the ratoon crop with the main crop harvested mechanically,relative to the grain yield of the ratoon crop with the main crop harvested manually.In comparison with LD,soil hardness was increased by 42.8%-84.7% in HD at the 5-20 cm soil depth at maturity of the main crop.Soil hardness at 5 and 10 cm depths reached respectively 4.05 and 7.07 kg cm^(-2) in HD.Soil drying treatment did not significantly affect the grain yield of the main crop.Under mechanical harvesting of the main crop,HD increased the grain yield of the ratoon crop by 9.4% relative to LD.Consequently,Y_(Loss) was only 3.4% in HD,in contrast to 16.3% in LD.The differences in grain yield and Y_(Loos) between the two soil drying treatments were explained mainly by panicles m^(-2),which was increased significantly by HD in the track zone of the ratoon crop compared with LD.These results suggest that heavy soil drying practice during the mid-to-late grain filling stage of the main crop is effective for reducing Y_(Loss) of the ratoon crop in a mechanized rice ratooning system.展开更多
Accurate soil moisture(SM)prediction is critical for understanding hydrological processes.Physics-based(PB)models exhibit large uncertainties in SM predictions arising from uncertain parameterizations and insufficient...Accurate soil moisture(SM)prediction is critical for understanding hydrological processes.Physics-based(PB)models exhibit large uncertainties in SM predictions arising from uncertain parameterizations and insufficient representation of land-surface processes.In addition to PB models,deep learning(DL)models have been widely used in SM predictions recently.However,few pure DL models have notably high success rates due to lacking physical information.Thus,we developed hybrid models to effectively integrate the outputs of PB models into DL models to improve SM predictions.To this end,we first developed a hybrid model based on the attention mechanism to take advantage of PB models at each forecast time scale(attention model).We further built an ensemble model that combined the advantages of different hybrid schemes(ensemble model).We utilized SM forecasts from the Global Forecast System to enhance the convolutional long short-term memory(ConvLSTM)model for 1–16 days of SM predictions.The performances of the proposed hybrid models were investigated and compared with two existing hybrid models.The results showed that the attention model could leverage benefits of PB models and achieved the best predictability of drought events among the different hybrid models.Moreover,the ensemble model performed best among all hybrid models at all forecast time scales and different soil conditions.It is highlighted that the ensemble model outperformed the pure DL model over 79.5%of in situ stations for 16-day predictions.These findings suggest that our proposed hybrid models can adequately exploit the benefits of PB model outputs to aid DL models in making SM predictions.展开更多
Soil characterization and heavy metals in different layers (0 - 15 cm;15 - 30 cm and 30 - 45 cm depth) of automobile mechanic waste dumps were studied. The soils showed remarkably high levels of all the metals above b...Soil characterization and heavy metals in different layers (0 - 15 cm;15 - 30 cm and 30 - 45 cm depth) of automobile mechanic waste dumps were studied. The soils showed remarkably high levels of all the metals above background concentrations with most (Ni, Cu, Fe, Cr and Cd) decreasing with soil depth. The distribution pattern were in the following order Fe > Cu > Zn > Pb > Cr > Ni > Cd. Across all the sampling locations and profiles, Fe and Cd showed the highest (476.4 μg·g-1) and least (37.5 μg·g-1) mean concentrations respectively. Pollution load index (PLI) and index of geoaccumulation (Igeo) revealed overall high and moderate contamination respectively but the enrichment factors (EFs) for Pb Ni and Cd are severe. The inter-element relationship revealed the identical source of elements in the soils of the studied area. The accuracy of the results has been cheeked using the standard reference material;SRM (PACS-2). The mechanic waste dumps represent potential sources of heavy metal pollution to environment. The elevated levels of heavy metals in these soil profiles constitute a serious threat to both surface and groundwater.展开更多
Biopolymers have become popular in geotechnical engineering as they provide a carbon-neutral alternative for soil solidification.Xanthan gum(XG)and jute fiber(JF)were selected to solidify the Yellow River dredged soil...Biopolymers have become popular in geotechnical engineering as they provide a carbon-neutral alternative for soil solidification.Xanthan gum(XG)and jute fiber(JF)were selected to solidify the Yellow River dredged soil.The mechanical behavior of solidified dredged soil(SDS)was investigated using a series of uniaxial compression and splitting tension tests at different XG and JF contents and fiber lengths.The results indicate that on the 28th day,the unconfined compressive strength(UCS)values of SDS samples reached 2.83 MPa and splitting tensile strength(STS)of 0.763 MPa at an XG content of 1.5%.When the JF content was greater than 0.9%,the STS of the SDS samples decreased.This is because that the large fiber content weakened the cementation ability of XG.The addition of JF can significantly increase the strain at peak strength of SDS samples.There is a linear relationship between the UCS and STS of the dredged soils solidified by XG and JF.Microanalysis shows that the strength of SDS samples was improved mainly via the cementation of XG itself and the network structure formed by JF with soil particles.The dredged soil reinforced by XG and JF shows better mechanical performance and has great potential for application.展开更多
The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansive soil f...The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansive soil following absorption of water. The constitutive relationships of the mechanics model include the relationship among swelling under free load, swelling under load, and vertical pressure, and the relationship of swelling under free loading and swelling pressure. A concept of additional compression modulus is introduced and the method determining the modulus is proposed. Finally, the predicted results of swelling potential using the mechanics model compare well with the measured data.展开更多
The current study deals Swith thermo-mechanical properties of stabilized soil small bricks with the help of organic binders of sugar cane molasses and cassava starch. Different formulations of soil concrete have been ...The current study deals Swith thermo-mechanical properties of stabilized soil small bricks with the help of organic binders of sugar cane molasses and cassava starch. Different formulations of soil concrete have been suggested after the geotechnical characterization of samples of soil was taken. From these, it arises that the studied soil is the most plastically clay (of type A<sub>3</sub>) according to GTR classification. Samples made of small bricks and measured out at 4%, 6% and 8% of binders (molasses, starch or molasses + starch) have been warmed up to different temperatures (100°C, 150°C, 200°C and 250°C) for the rising of the thermic behavior under different conditions and submitted to crushing testings for the estimation of characteristic resistances to the compression. According to the mechanical behavior, we note an improvement of resistances for small bricks measured 4%, 6% and 8%, of molasses respectively of 32.44%, 32.06% and 23.43% against the value of reference for small bricks without molasses. In the same way, the binder (molasses + starch) also reveals an improvement of resistance to the compression of 13.27%, 26.17% and 26.17%. On the contrary, the stabilization with the starch binder did not bring a significative improvement. According to the thermic influence, the heating at 100°C of stabilized small bricks at 4%, 6% and 8% of molasses, reveals a significative improvement of resistances. Moreover, the stabilization with the starch reveals on the contrary a good behavior for heatings at 150°C and 250°C. In short, for the binder (molasses + starch), it is the heating at 200°C that shows some improvements of remarkable resistances. Different analyses of realized statistics also show the effectivity of obtained results. For all realized formulations, the measuring out at 6% of binders (molasses, or molasses + starch) seems as optimal in front of the best thermo-mechanical revealed properties.展开更多
This study assessed the effect of patch scarification and mounding on the physical properties of the root layer and the success of tree planting in various types of forests.This study was conducted on 12 forest sites ...This study assessed the effect of patch scarification and mounding on the physical properties of the root layer and the success of tree planting in various types of forests.This study was conducted on 12 forest sites in taiga forests of the European part of Russia.A total of 54 plots were set up to assess seedling survival;root collar diameter,height,and heigh increment were measured for 240 seedlings to assess growth.In the rooting layer,240 soil samples were taken to determine physical properties.The study showed that soil treatment methods had no effect on bulk density and total porosity in Cladina sites.However,reduced soil moisture was noted,particularly in mounds,resulting in increased aeration.In Myrtillus sites,there were increased bulk density,reduced soil moisture,and total porosity in the mounds.Mounding treatment in Polytrichum sites resulted in reduced soil moisture and increased aeration porosity.In the Myrtillus and Polytrichum sites,patch scarification had no effects on physical properties.In Polytrichum sites,survival rates,heights,and heigh increments of bareroot Norway spruce seedlings in mounds were higher than in patches;however,the same did not apply to diameter.In Cladina and Myrtillus sites,there was no difference in growth for bareroot and containerised seedlings with different soil treatments.Growing conditions and soil types should be considered when applying different soil treatment methods to ensure high survival rates and successful seedling growth.展开更多
The synergistic impact of mechanical ball milling and flue gas desulfurization(FGD)gypsum on the dealkalization of bauxite residue was investigated through integrated analyses of solution chemistry,mineralogy,and micr...The synergistic impact of mechanical ball milling and flue gas desulfurization(FGD)gypsum on the dealkalization of bauxite residue was investigated through integrated analyses of solution chemistry,mineralogy,and microtopography.The results showed a significant decrease in Na_(2)O content(>30 wt.%)of FGD gypsum-treated bauxite residue after 30 min of mechanical ball milling.Mechanical ball milling resulted in differentiation of the elemental distribution,modification of the minerals in crystalline structure,and promotion in the dissolution of alkaline minerals,thus enhancing the acid neutralization capacity of bauxite residue.5 wt.%FGD gypsum combined with 30 min mechanical ball milling was optimal for the dealkalization of bauxite residue.展开更多
With the advancement of agricultural mechanization,soil compaction has become a serious environmental problem.Soil compaction can increase soil bulk density and firmness,reduce porosity and permeability,and deteriorat...With the advancement of agricultural mechanization,soil compaction has become a serious environmental problem.Soil compaction can increase soil bulk density and firmness,reduce porosity and permeability,and deteriorate soil structure,ultimately inhibit sugar beet growth and reduce both root yield and sugar content.However,few farmers recognize the link between soil compaction and these adverse effects.Soil compaction has a cumulative effect,with significant differences observed in the vertical range of compaction accumulation.The most significant soil compaction occurs in the topsoil of 0-10 cm,and the influence depth can reach 70 cm,but it is small in deep soil,and the inflection point is at a soil depth of 10 cm.The degree of soil compaction is related to soil type,water content,tractor shaft load,tyre type,tyre pressure and operation speed,etc.Therefore,in the production process of sugar beet,it is advisable to avoid high-humidity operations,use low pressure tyres,reduce the number of tractor-units passes over the farmland,and implement agricultural and agronomic measures to minimize soil compaction.These practices will help protect the soil environment and ensure sustainable production of sugar beets.展开更多
The number workable days (NWD) for agricultural field operations is of great importance for sizing agricultural machinery fleets. This is especially pivotal for sugarcane harvest, which extends from 8 to 10 months/yea...The number workable days (NWD) for agricultural field operations is of great importance for sizing agricultural machinery fleets. This is especially pivotal for sugarcane harvest, which extends from 8 to 10 months/year. In light of this, the current study aimed at defining criteria for obtaining the NWD for rational sugarcane harvest at different sites in the state of São Paulo, southern Brazil, taking into account both a general and a specific criteria. For this purpose, data from harvest interruption of 30 sugar mills in southern Brazil throughout periods ranging from two to five years were used. The following variables were tested as criteria for defining harvest interruption: minimum precipitation (PREC);soil water holding capacity (SWHC);and the limit of the ratio between actual soil moisture (SM) and SWHC. Based on such a specific criterion ascribed to each site along with a general criterion, NWD maps were prepared for the state of São Paulo, Brazil. The results showed that there were variations from the definition criteria of NWD at the different sites in the state. However, the use of a general criterion for harvest interruption, based on PREC ≥ 3 mm, SWHC = 40 mm and SM/SWHC ≥ 90%, provided accurate results. During the validation of these criteria, the NWD maps generated from the individual criterion proposed for each site resulted in an average error of 24.9 days/year, whereas the map generated from the general criterion culminated in an average error of 4.4 days/year.展开更多
This paper analyzes a coupled thermo-hydro-mechanical behavior of unsaturated soils based on the theory of mixtures. Unsaturated soil is considered as a mixture composed of soil skeleton, liquid water, vapor, dry air,...This paper analyzes a coupled thermo-hydro-mechanical behavior of unsaturated soils based on the theory of mixtures. Unsaturated soil is considered as a mixture composed of soil skeleton, liquid water, vapor, dry air, and dissolved air. In addition to the mass and momentum conservation equations of each component and the energy conservation equation of the mixture, the system is closed using other 37 constitutive (or restriction) equations. As the change in water chemical potential is identical to the change in vapor chemical potential, a thermodynamic restriction relationship for the phase transition between pore water and pore vapor is formulated, in which the impact of the change in gas pressure on the phase transition is taken into account. Six final govern- ing equations are given in incremental form in terms of six primary variables, i.e., three displacement components of soil skeleton, water pressure, gas pressure, and temperature. The processes involved in the coupled model include thermal expansions of soil skeleton and soil particle, Soret effect, phase transition between water and vapor, air dissolution in pore water, and deformation of soil skeleton.展开更多
文摘The study carried out concerns the valorization of agricultural waste for the development of biosourced materials that can be used as insulation in homes. This article is devoted to the influence of gum arabic on the mechanical and thermal properties of clay soils in the town of Abéché. The mechanical tests were carried out using the CBR press equipped with two devices (bending device and compression device). Thermal property such as thermal conductivity was determined by the hot wire method and thermal resistance was derived by calculation. Thus, the tests were carried out on test pieces made from a mixture of clay and gum arabic in solution. The experimental program includes seven formulations (0%, 2%, 4%, 6%, 8%, 10% and 12%). The results obtained showed that the best flexural and compressive strengths are obtained by using gum arabic with a rate of 8% and a maximum stress of 4.3 MPa. In addition, the thermal results also showed that the thermal conductivity decreases when the percentage of gum arabic increases, which makes it possible to increase the thermal resistance, thus confirming the capacity of gum arabic to provide thermal insulation.
基金supported by the National Natural Science Foundation of China (No. 41471062, No. 41971085, No. 41971086)。
文摘The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.
基金This research work is part of a research project(Grant No.IH18.03.1)sponsored by the SPARC Hub at the Department of Civil Engineering,Monash University funded by the Australian Research Council(ARC)Industrial Transformation Research Hub(ITRH)Scheme(Grant No.IH180100010).
文摘This study introduces an advanced finite element model for the light weight deflectometer(LWD),which integrates contact mechanics with fully coupled models.By simulating LWD tests on granular soils at various saturation levels,the model accurately reflects the dependence of the LWD modulus on dry density,water content,and effective stress.This model addresses and overcomes the limitations of previous finite element models for this specific problem.Simultaneously,this research presents the first experimentally validated fully coupled contact impact model.Furthermore,the research provides a comparative assessment of elastoplastic and nonlinear elastic models and contrasts an enriched node-tosegment method(developed in this study)with the more precise mortar technique for contact mechanics.These comparisons reveal unique advantages and challenges for each method.Moreover,the study underscores the importance of careful application of the LWD modulus,emphasising the need for sophisticated tools to interpret soil behaviour accurately.
基金supported by the Key Research Program of the Institute of Geology and Geophysics,CAS(Nos.IGGCAS-202102 and IGGCAS-201904)the National Natural Science Foundation of China(No.42230111)the CAS Key Technology Talent Program。
文摘After landing in the Utopia Planitia,Tianwen-1 formed the deepest landing crater on Mars,approximately 40 cm deep,exposing precious information about the mechanical properties of Martian soil.We established numerical models for the plume-surface interaction(PSI)and the crater formation based on Computational Fluid Dynamics(CFD)methods and the erosion model modified from Roberts’Theory.Comparative studies of cases were conducted with different nozzle heights and soil mechanical properties.The increase in cohesion and internal friction angle leads to a decrease in erosion rate and maximum crater depth,with the cohesion having a greater impact.The influence of the nozzle height is not clear,as it interacts with the position of the Shock Diamond to jointly control the erosion process.Furthermore,we categorized the evolution of landing craters into the dispersive and the concentrated erosion modes based on the morphological characteristics.Finally,we estimated the upper limits of the Martian soil’s mechanical properties near Tianwen-1 landing site,with the cohesion ranging from 2612 to 2042 Pa and internal friction angle from 25°to 41°.
文摘In Senegal, particularly in the Senegal River valley, agricultural mechanization remains limited, mainly due to a lack of agricultural equipment, a lack of expertise in agricultural machinery and an apprehension of the consequences on soil quality. To better understand agricultural mechanization of rice cultivation, this survey study has been carried out in the Senegal river valley. Precisely, this work aimed to characterize farm machinery and its effects on soil and rice cultivation. A questionnaire was administered to 304 out of 1270 farmers, spread over 8 rice-growing areas, 4 of which are located in the Podor department, three in Dagana and one in Saint-Louis. The results showed that 99.3% of farmers used motorized equipment, with 95.7% using tractor and 3.6% a power tiller. Offset tillage, which is a shallow cultivation practice carried out to break up hard soil without turning it over, was most widespread among growers (95.4%). 78.3% of the valley’s farmers felt that the machinery used to carry out tillage operations was inefficient. According to the farmers, the main constraints on the use of agricultural machinery in the valley were: the upkeep and maintenance of equipment (57%), the lack of expertise in mechanization (31%), and issues adapting machinery to local conditions (12%). Those constraints have contributed to a drop in yields in recent years, the spread of weeds on cultivated plots and the gradual degradation of the soil in the area according to 78% of farmers.
文摘The history of the formation of the alpine region is affected by the activities of the glaciers, which have a strong influence on underground works in this area. Mechanized tunneling must adapt to the presence of sound and altered rock, as well as to inhomogeneous soil layers that range from permeable gravel to soft clay sediments along the same tunnel. This article focuses on past experiences with tunnel-boring machines (TBMs) in Switzerland, and specifically on the aspects of soil conditioning during a passage through inhomogeneous soft soils. Most tunnels in the past were drilled using the slurry mode (SM), in which the application of different additives was mainly limited to difficult zones of high permeability and stoppages for tool change and modification. For drillings with the less common earth pressure balanced mode (EPBM), continuous foam conditioning and the additional use of polymer and bentonite have proven to be successful. The use of conditioning additives led to new challenges during separation of the slurries (for SM) and disposal of the excavated soil (for EPBM). If the disposal of chemically treated soft soil mate- rial from the earth pressure balanced (EPB) drive in a manner that is compliant with environmental legislation is considered early on in the design and evaluation of the excavation mode, the EPBM can be beneficial for tunnels bored in glacial deposits.
基金Funded by National Natural Science Foundation of China(NSFC)(Nos.52178216,51868044)。
文摘To reveal the deterioration mechanism and service life of concrete durability in the western saline soil area,the indoor accelerated test of the concrete specimen was simulated in the coupled environment of salt erosion and dry-wet cycles in the west saline soil area of China.The deterioration mechanism of concrete durability was revealed through the relative dynamic elastic modulus,relative quality evaluation parameters,SEM,and XRD evaluation indexes.Random Wiener distribution function was used for modeling life prediction.The results show that the relative dynamic elastic modulus evaluation parameter as an evaluation index of concrete durability under various environmental coupling effects is more reliable than the relative quality,there were holes and cracks in the concrete,and needle-like and layered crystals grow from the internal cracks.The corrosion products include ettringite,gypsum and other expansive crystals and non-gelling Mg(OH)_(2);the expansion stress caused by physical,chemical reaction,and temperature change under the action of drywet cycle aggravates the formation and development of cracks.The random Wiener distribution function can describe the degradation process of concrete specimen durability,and the established concrete reliability function can intuitively reflect the service life of concrete specimens.
基金the Chinese Scholarship Council,which funded her Joint Ph D research programthe support from Natural Sciences and Engineering Research Council of Canada(NSERC)for his research programsthe Chinese Ministry of Science and Technology for supporting his research program(grant No.2014CB744701)
文摘Loess soil deposits are widely distributed in arid and semi-arid regions and constitute about 10% of land area of the world.These soils typically have a loose honeycomb-type meta-stable structure that is susceptible to a large reduction in total volume or collapse upon wetting.Collapse characteristics contribute to various problems to infrastructures that are constructed on loess soils.For this reason,collapse triggering mechanism for loess soils has been of significant interest for researchers and practitioners all over the world.This paper aims at providing a state-of-the-art review on collapse mechanism with special reference to loess soil deposits.The collapse mechanism studies are summarized under three different categories,i.e.traditional approaches,microstructure approach,and soil mechanics-based approaches.The traditional and microstructure approaches for interpreting the collapse behavior are comprehensively summarized and critically reviewed based on the experimental results from the literature.The soil mechanics-based approaches proposed based on the experimental results of both compacted soils and natural loess soils are reviewed highlighting their strengths and limitations for estimating the collapse behavior.Simpler soil mechanics-based approaches with less parameters or parameters that are easy-to-determine from conventional tests are suggested for future research to better understand the collapse behavior of natural loess soils.Such studies would be more valuable for use in conventional geotechnical engineering practice applications.
基金The financial supports of the National Natural Science Foundation of China(Grant No.42177148)the opening fund of State Key Laboratory of Geohazard Prevention and Geo-environment Protection(Grant No.SKLGP 2023K011)Postdoctoral Research Project of Guangzhou(Grant No.20220402)are gratefully thanked.
文摘The micaceous weathered granitic soil(WGS)is frequently encountered in civil engineering worldwide,unfortunately little information is available regarding how mica affects the physico-mechanical behaviors of WGS.This study prepares reconstituted WGS with different mica contents by removing natural mica in theWGS,and then mixes it with commercial mica powders.The geotechnical behavior as well as the microstructures of the mixtures are characterized.The addition of mica enables the physical indices of WGS to be specific combinations of coarser gradation and high permeability but high Atterberg limits.However,high mica content in WGS was found to be associated with undesirable mechanical properties,including increased compressibility,disintegration,and swelling potential,as well as poor compactability and low effective frictional angle.Microstructural analysis indicates that the influence of mica on the responses of mixtures originates from the intrinsic nature of mica as well as the particle packing being formed withinWGS.Mica exists in the mixture as stacks of plates that form a spongy structure with high compressibility and swelling potential.Pores among the plates give the soil high water retention and high Atterberg limits.Large pores are also generated by soil particles with bridging packing,which enhances the permeability and water-soil interactions upon immersion.This study provides a microlevel understanding of how mica dominates the behavior of WGS and provides new insights into the effective stabilization and improvement of micaceous soils.
基金supported by the Major International (Regional)Joint Research Project of National Natural Science Foundation of China (32061143038)the China Agriculture Research System(CARS-01-20)the Fundamental Research Funds for the Central Universities (2662020ZKPY015)。
文摘Yield loss(Y_(Loss)) in the ratoon crop due to crushing damage to left stubble from mechanical harvesting of the main crop is a constraint for wide adoption of mechanized rice ratooning technology.Soil drying before the harvest of the main crop has been proposed to overcome this problem.The objective of this study was to determine the effect of soil drying during the mid-to-late grain filling stage of the main crop on grain yield of the ratoon crop in a mechanized rice ratooning system.Field experiments were conducted to compare Y_(Loss) between light(LD) and heavy(HD) soil drying treatments in Hubei province,central China in 2017 and 2018.Y_(Loss) was calculated as the percentage of yield reduction in the ratoon crop with the main crop harvested mechanically,relative to the grain yield of the ratoon crop with the main crop harvested manually.In comparison with LD,soil hardness was increased by 42.8%-84.7% in HD at the 5-20 cm soil depth at maturity of the main crop.Soil hardness at 5 and 10 cm depths reached respectively 4.05 and 7.07 kg cm^(-2) in HD.Soil drying treatment did not significantly affect the grain yield of the main crop.Under mechanical harvesting of the main crop,HD increased the grain yield of the ratoon crop by 9.4% relative to LD.Consequently,Y_(Loss) was only 3.4% in HD,in contrast to 16.3% in LD.The differences in grain yield and Y_(Loos) between the two soil drying treatments were explained mainly by panicles m^(-2),which was increased significantly by HD in the track zone of the ratoon crop compared with LD.These results suggest that heavy soil drying practice during the mid-to-late grain filling stage of the main crop is effective for reducing Y_(Loss) of the ratoon crop in a mechanized rice ratooning system.
基金supported by the Natural Science Foundation of China(Grant Nos.42088101 and 42205149)Zhongwang WEI was supported by the Natural Science Foundation of China(Grant No.42075158)+1 种基金Wei SHANGGUAN was supported by the Natural Science Foundation of China(Grant No.41975122)Yonggen ZHANG was supported by the National Natural Science Foundation of Tianjin(Grant No.20JCQNJC01660).
文摘Accurate soil moisture(SM)prediction is critical for understanding hydrological processes.Physics-based(PB)models exhibit large uncertainties in SM predictions arising from uncertain parameterizations and insufficient representation of land-surface processes.In addition to PB models,deep learning(DL)models have been widely used in SM predictions recently.However,few pure DL models have notably high success rates due to lacking physical information.Thus,we developed hybrid models to effectively integrate the outputs of PB models into DL models to improve SM predictions.To this end,we first developed a hybrid model based on the attention mechanism to take advantage of PB models at each forecast time scale(attention model).We further built an ensemble model that combined the advantages of different hybrid schemes(ensemble model).We utilized SM forecasts from the Global Forecast System to enhance the convolutional long short-term memory(ConvLSTM)model for 1–16 days of SM predictions.The performances of the proposed hybrid models were investigated and compared with two existing hybrid models.The results showed that the attention model could leverage benefits of PB models and achieved the best predictability of drought events among the different hybrid models.Moreover,the ensemble model performed best among all hybrid models at all forecast time scales and different soil conditions.It is highlighted that the ensemble model outperformed the pure DL model over 79.5%of in situ stations for 16-day predictions.These findings suggest that our proposed hybrid models can adequately exploit the benefits of PB model outputs to aid DL models in making SM predictions.
文摘Soil characterization and heavy metals in different layers (0 - 15 cm;15 - 30 cm and 30 - 45 cm depth) of automobile mechanic waste dumps were studied. The soils showed remarkably high levels of all the metals above background concentrations with most (Ni, Cu, Fe, Cr and Cd) decreasing with soil depth. The distribution pattern were in the following order Fe > Cu > Zn > Pb > Cr > Ni > Cd. Across all the sampling locations and profiles, Fe and Cd showed the highest (476.4 μg·g-1) and least (37.5 μg·g-1) mean concentrations respectively. Pollution load index (PLI) and index of geoaccumulation (Igeo) revealed overall high and moderate contamination respectively but the enrichment factors (EFs) for Pb Ni and Cd are severe. The inter-element relationship revealed the identical source of elements in the soils of the studied area. The accuracy of the results has been cheeked using the standard reference material;SRM (PACS-2). The mechanic waste dumps represent potential sources of heavy metal pollution to environment. The elevated levels of heavy metals in these soil profiles constitute a serious threat to both surface and groundwater.
基金The authors would like to acknowledge the financial support provided by the National Natural Science Foundation of China(Grant Nos.51979267 and 52074143)the Major Science and Technology Program of Inner Mongolia,China(Grant No.2021ZD0007).
文摘Biopolymers have become popular in geotechnical engineering as they provide a carbon-neutral alternative for soil solidification.Xanthan gum(XG)and jute fiber(JF)were selected to solidify the Yellow River dredged soil.The mechanical behavior of solidified dredged soil(SDS)was investigated using a series of uniaxial compression and splitting tension tests at different XG and JF contents and fiber lengths.The results indicate that on the 28th day,the unconfined compressive strength(UCS)values of SDS samples reached 2.83 MPa and splitting tensile strength(STS)of 0.763 MPa at an XG content of 1.5%.When the JF content was greater than 0.9%,the STS of the SDS samples decreased.This is because that the large fiber content weakened the cementation ability of XG.The addition of JF can significantly increase the strain at peak strength of SDS samples.There is a linear relationship between the UCS and STS of the dredged soils solidified by XG and JF.Microanalysis shows that the strength of SDS samples was improved mainly via the cementation of XG itself and the network structure formed by JF with soil particles.The dredged soil reinforced by XG and JF shows better mechanical performance and has great potential for application.
文摘The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansive soil following absorption of water. The constitutive relationships of the mechanics model include the relationship among swelling under free load, swelling under load, and vertical pressure, and the relationship of swelling under free loading and swelling pressure. A concept of additional compression modulus is introduced and the method determining the modulus is proposed. Finally, the predicted results of swelling potential using the mechanics model compare well with the measured data.
文摘The current study deals Swith thermo-mechanical properties of stabilized soil small bricks with the help of organic binders of sugar cane molasses and cassava starch. Different formulations of soil concrete have been suggested after the geotechnical characterization of samples of soil was taken. From these, it arises that the studied soil is the most plastically clay (of type A<sub>3</sub>) according to GTR classification. Samples made of small bricks and measured out at 4%, 6% and 8% of binders (molasses, starch or molasses + starch) have been warmed up to different temperatures (100°C, 150°C, 200°C and 250°C) for the rising of the thermic behavior under different conditions and submitted to crushing testings for the estimation of characteristic resistances to the compression. According to the mechanical behavior, we note an improvement of resistances for small bricks measured 4%, 6% and 8%, of molasses respectively of 32.44%, 32.06% and 23.43% against the value of reference for small bricks without molasses. In the same way, the binder (molasses + starch) also reveals an improvement of resistance to the compression of 13.27%, 26.17% and 26.17%. On the contrary, the stabilization with the starch binder did not bring a significative improvement. According to the thermic influence, the heating at 100°C of stabilized small bricks at 4%, 6% and 8% of molasses, reveals a significative improvement of resistances. Moreover, the stabilization with the starch reveals on the contrary a good behavior for heatings at 150°C and 250°C. In short, for the binder (molasses + starch), it is the heating at 200°C that shows some improvements of remarkable resistances. Different analyses of realized statistics also show the effectivity of obtained results. For all realized formulations, the measuring out at 6% of binders (molasses, or molasses + starch) seems as optimal in front of the best thermo-mechanical revealed properties.
基金based on studies conducted under a governmental request to“Northern Research Institute of Forestry”for performance of applied research within the remit of the Federal Forestry Agency.Project registration No.122020100319-9。
文摘This study assessed the effect of patch scarification and mounding on the physical properties of the root layer and the success of tree planting in various types of forests.This study was conducted on 12 forest sites in taiga forests of the European part of Russia.A total of 54 plots were set up to assess seedling survival;root collar diameter,height,and heigh increment were measured for 240 seedlings to assess growth.In the rooting layer,240 soil samples were taken to determine physical properties.The study showed that soil treatment methods had no effect on bulk density and total porosity in Cladina sites.However,reduced soil moisture was noted,particularly in mounds,resulting in increased aeration.In Myrtillus sites,there were increased bulk density,reduced soil moisture,and total porosity in the mounds.Mounding treatment in Polytrichum sites resulted in reduced soil moisture and increased aeration porosity.In the Myrtillus and Polytrichum sites,patch scarification had no effects on physical properties.In Polytrichum sites,survival rates,heights,and heigh increments of bareroot Norway spruce seedlings in mounds were higher than in patches;however,the same did not apply to diameter.In Cladina and Myrtillus sites,there was no difference in growth for bareroot and containerised seedlings with different soil treatments.Growing conditions and soil types should be considered when applying different soil treatment methods to ensure high survival rates and successful seedling growth.
基金the National Natural Science Foundation of China(Nos.42177391,42077379)the Natural Science Foundation of Hunan Province,China(No.2022JJ20060)+1 种基金the Central South University Innovation-driven Research Program,China(No.2023CXQD065)the Fundamental Research Funds for the Central Universities of Central South University,China(No.2023ZZTS0800).
文摘The synergistic impact of mechanical ball milling and flue gas desulfurization(FGD)gypsum on the dealkalization of bauxite residue was investigated through integrated analyses of solution chemistry,mineralogy,and microtopography.The results showed a significant decrease in Na_(2)O content(>30 wt.%)of FGD gypsum-treated bauxite residue after 30 min of mechanical ball milling.Mechanical ball milling resulted in differentiation of the elemental distribution,modification of the minerals in crystalline structure,and promotion in the dissolution of alkaline minerals,thus enhancing the acid neutralization capacity of bauxite residue.5 wt.%FGD gypsum combined with 30 min mechanical ball milling was optimal for the dealkalization of bauxite residue.
基金Supported by China Agriculture Research System(Sugar Crops)of Ministry of Agriculture and Rural Affairs and Ministry of Finance(CARS-170601)Natural Science Foundation of Heilongjiang Province(C201239).
文摘With the advancement of agricultural mechanization,soil compaction has become a serious environmental problem.Soil compaction can increase soil bulk density and firmness,reduce porosity and permeability,and deteriorate soil structure,ultimately inhibit sugar beet growth and reduce both root yield and sugar content.However,few farmers recognize the link between soil compaction and these adverse effects.Soil compaction has a cumulative effect,with significant differences observed in the vertical range of compaction accumulation.The most significant soil compaction occurs in the topsoil of 0-10 cm,and the influence depth can reach 70 cm,but it is small in deep soil,and the inflection point is at a soil depth of 10 cm.The degree of soil compaction is related to soil type,water content,tractor shaft load,tyre type,tyre pressure and operation speed,etc.Therefore,in the production process of sugar beet,it is advisable to avoid high-humidity operations,use low pressure tyres,reduce the number of tractor-units passes over the farmland,and implement agricultural and agronomic measures to minimize soil compaction.These practices will help protect the soil environment and ensure sustainable production of sugar beets.
文摘The number workable days (NWD) for agricultural field operations is of great importance for sizing agricultural machinery fleets. This is especially pivotal for sugarcane harvest, which extends from 8 to 10 months/year. In light of this, the current study aimed at defining criteria for obtaining the NWD for rational sugarcane harvest at different sites in the state of São Paulo, southern Brazil, taking into account both a general and a specific criteria. For this purpose, data from harvest interruption of 30 sugar mills in southern Brazil throughout periods ranging from two to five years were used. The following variables were tested as criteria for defining harvest interruption: minimum precipitation (PREC);soil water holding capacity (SWHC);and the limit of the ratio between actual soil moisture (SM) and SWHC. Based on such a specific criterion ascribed to each site along with a general criterion, NWD maps were prepared for the state of São Paulo, Brazil. The results showed that there were variations from the definition criteria of NWD at the different sites in the state. However, the use of a general criterion for harvest interruption, based on PREC ≥ 3 mm, SWHC = 40 mm and SM/SWHC ≥ 90%, provided accurate results. During the validation of these criteria, the NWD maps generated from the individual criterion proposed for each site resulted in an average error of 24.9 days/year, whereas the map generated from the general criterion culminated in an average error of 4.4 days/year.
基金Project supported by the National Natural Science Foundation of China (Nos. 10672182 and 11072265)the Natural Science Foundation Project of Chongqing Science and Technology Commission (No. 2009BB7343)
文摘This paper analyzes a coupled thermo-hydro-mechanical behavior of unsaturated soils based on the theory of mixtures. Unsaturated soil is considered as a mixture composed of soil skeleton, liquid water, vapor, dry air, and dissolved air. In addition to the mass and momentum conservation equations of each component and the energy conservation equation of the mixture, the system is closed using other 37 constitutive (or restriction) equations. As the change in water chemical potential is identical to the change in vapor chemical potential, a thermodynamic restriction relationship for the phase transition between pore water and pore vapor is formulated, in which the impact of the change in gas pressure on the phase transition is taken into account. Six final govern- ing equations are given in incremental form in terms of six primary variables, i.e., three displacement components of soil skeleton, water pressure, gas pressure, and temperature. The processes involved in the coupled model include thermal expansions of soil skeleton and soil particle, Soret effect, phase transition between water and vapor, air dissolution in pore water, and deformation of soil skeleton.