Displacement Of Soil Particles Research Articles

Two‐Dimensional Analytical Solution for Transient Flow in Unsaturated Soils Considering Hydromechanical Coupling

AbstractThis paper presents a two‐dimensional solution for unsaturated transient seepage flow in a trapezoidal region using analytical solutions for flow in a series of rectangular regions. The coupled formulation considers the interaction among fluid flow due to differences in head and displacement of soil particles. The solution in each rectangular region is derived using Laplace Transform and Discrete Fourier Series for two top boundary conditions: specified pressure head and specified flow rate. The accuracy of the proposed solution is verified by comparing the results against those attained from the finite difference method. The proposed solution is applied to two example problems, demonstrating its efficacy and accuracy. The findings show a significant difference in the coupled and uncoupled results for fine‐grained soils possessing a small Gardner's coefficient. Additionally, the uncoupled pressure heads advanced quicker to a steady state than the coupled ones for soils with a small Gardner's coefficient. The coupling effect becomes less prominent as Gardner's coefficient increases. This study is the first attempt in the literature to provide a solution for unsaturated flow in a trapezoidal or non‐rectangular domain using analytical solution techniques, which can better represent complex real‐world applications (e.g., slopes, embankments, dams).

Recommendations on Use of DIC in Experimental Geotechnics

Abstract Image-based deformation measurement techniques, like digital image correlation (DIC), are used to measure the displacement of soil particles and thereby to investigate the behavior of geo-structure in experimental geotechnics. The precision of the measurement from the DIC technique depends on the position of the camera and light panels, the color temperature of light, size of the region of interest (RoI), type and relative density of sand, seeding ratio, type of camera, and strain rate used in experiments. In the paper, the effect of above-mentioned parameters is investigated experimentally in 1-g model tests. The studies show that the precision in DIC measurements is dependent on the position of camera and light panels, size of RoI, texture of the sand, and seeding ratio. However, the relative density of sand and strain rate do not significantly affect the results from the DIC analysis. The efficacy in the measurement of the large deformations and suitability of smartphone cameras using DIC are also addressed. Last, we developed recommendations to obtain precise results from DIC in experimental geotechnics.

Influence of primary tillage on the displacement of soil particles

Influence of primary tillage on the displacement of soil particles

Effect of Rotary Speed on Soil and Straw Throwing Process by Stubble-Crushing Blade for Strip Tillage Using DEM-CFD

Strip tillage is a widely used land preparation approach for effective straw management in conservation agriculture. Understanding the dynamic throwing process during the stubble-crushing operation has important implications for seedbed preparation. However, the airflow generated by the high-speed rotation of stubble-crushing blades has yet to be considered. We established a coupled DEM-CFD simulation model and explored the dynamic motion of soil particles varied with their initial depth (at 0, 20, 40, 60, 80 mm depth) and surface straw under different blade rotary speeds (270, 540, 720, and 810 rpm) based on the model. The coupled model simulation results were proved to be well correlated with the field test results by the field high-speed camera test. The simulation results showed that airflow had a significant effect on the longitudinal displacement of straw (p < 0.05). An increase in rotary speed could increase the longitudinal and lateral throwing displacement of soil particles and straw and increase the blade–soil–straw interaction, while there was no directional effect on the vertical motion. The lateral movement of soil particles decreased with increasing soil particle depth. The stubble-crushing operation allowed the exchange of deep and shallow soil layers, as well as the burial of straw. Plain, straight stubble-crushing blades with a rotary speed of 540 rpm were able to form the optimal seeding row with a width of 80.86 mm. The simulation results were useful for assessing the design solutions of high-speed rotational tools and evaluating seedbed preparation practices.

Soil deformation after one water-drop impact – The effect of texture and soil moisture content

The splash phenomenon (being the first stage of water erosion) is caused by the drops’ impact on the soil surface, resulting in the displacement of soil particles and the creation of a deformation – a small-sized crater. The aim of this research was to analyse the effect of the drops' impact energy, the initial moisture content, and the texture of the soils used (loamy sand, sandy loam, silty loam) on the size of the formed craters. Measurements were made using a 3D surface scanner to determine the depth and volume of craters along with the equivalent diameter and circularity of their top cross-sections. In each of the experiment variants, the impact of the drops resulted in changes on the soil surface. Moisture content was the factor with the highest influence on crater formation (increase in moisture resulted in an increase in the size of the craters). The highest circularity was observed in craters formed on silty loam, which had the largest amount of silt content among the investigated soils. Increasing the drop energy resulted in an increase in the average values of the measured quantities, but only in a few cases were these changes statistically significant. The conducted research demonstrates the utility of surface scanners in accurately measuring soil deformation after drop impact. In addition, the acquired results can support the development of erosion models, increase the knowledge regarding the splash phenomenon, and help to make further steps in linking the splash to subsequent stages of water erosion.

The Recent Sediment Record as an Indicator of Past Soil-Erosion Dynamics. Study in Dehesa Areas in the Province of Cáceres (Spain)

The work presented is a study of the recent sediment deposits in a pilot basin in dehesa areas in the province of Cáceres (Spain) through analysis of the sediment record, radiocarbon dating and correlation with historic data to assess the factors that conditioned the deposit in these areas over time. It is a qualitative study based on the important role of sediments as recorders of history, given that sediment facies and their architecture provide one of the best records of past processes and environmental factors. For the study, sediment profile surveys were used to determine the configuration and characteristics of the infill and its chronology. The sediment model of the facies studied is associated with a context of slope water erosion that led to the infill of the watercourse areas, mainly sand and fine gravel, where alterations in the normal rate were detected due to the insertion of a thicker level of materials (soil stoniness) that was able to be dated. The sediment and chronological results obtained can be used to determine the historical events in the area that could have affected the erosion and deposit processes in the basin for the estimated period, from the late 18th to the early 19th century. During this period, pastureland that maintained the ecological balance of the dehesa, with a balanced, stable displacement of soil particles, was converted to cropland, in most cases resulting in soil with a limited profile, overuse and the consequent loss of structure and texture, making it more vulnerable to erosion. Greater remobilisation would have carried thicker material to the watercourses than the material deposited as a result of limited ploughing. This study provides data for the dehesa areas studied with regard to their hydrogeomorphological dynamics, from which past environmental impacts due to tillage can be inferred.

Simulation Analysis on Pile-driving Process of Anti-flood Bionic Screw Pile

In order to reduce the dynamic energy consumption of pile-driving of the anti-flood screw piles, the unsmoothed surface is applied to the screw pile tip to form an anti-flood bionic screw pile. In ANSYS, the FEM-SPH coupling algorithm is used to model and simulate the pile-driving process of bionic screw piles, and the simulation results of soil stress distribution, radial displacement of soil particles and pile-driving torque are obtained. The results of the pile-driving test show that the test torque is less than the simulated torque, and the soil pressure is consistent with the simulation results. The correctness of the simulation model is verified, which provides a theoretical basis for further improving the bionic screw pile and the pile-driving equipment.

Fluid Coupled-DEM Simulation of Lateral Loading Experiment for Buried Pipe in Saturated Sand

Two-dimensional simulation was carried out using a fluid coupled-DEM (discrete element method) analysis on lateral loading experiments for a pipe buried in saturated sand. The interaction between soil and pore water was reproduced by dividing the model into solid and fluid phases. The variation of the excess pore water pressure was calculated on a fluid mesh based on the pore volume change and was then given to the soil particles in the solid phase. The head difference between the fluid meshes produced upward seepage to the soil model. Liquefaction was reproduced by the decrease of the contact force between the soil particles due to the upward seepage. The force-displacement curves obtained from lateral loading simulations showed good agreement with the experimental results under various effective stress conditions. Distribution maps of contact force and displacement of soil particles revealed displacement mechanism of the buried pipe and its surrounding soil. The variation of the void ratio and the excess pore water pressure with the pipe displacement could be reproduced to some extent, and the applicability of this analysis method to interaction problems has been verified.

Earth Structures Stability Under Rapid Drawdown Conditions

Abstract The paper presents the slope stability analysis of the unmodernised section of the Groszowice separation levee in the condition of water level changes, particularly after rapid drawdown. Based on soils field and laboratory tests, the stability analysis of the construction was conducted with GEO5 software. For the upper levee, the utilisation degree of slopes resistance was determined according to the Eurocode 7. Calculations were conducted for normal and high water level, as well as after rapid drawdown. The analysis was carried out with the use of five most commonly applied methods. The results have shown that at normal and high water level, the structure was stable. However, it does not correspond with its existing damages. The loss of stability was proved only under rapid drawdown conditions. Additionally, for the central part of the separation levee, the filtration curve position was conducted with the use of the Finite Elements Method (FEM). The water seepage on the slope above normal water level explains the suffosion displacement of soil particles that occurs due to damaged slope sealing and drainage.

Effect of water drop energy of sprinkler irrigation on clay and silt particles transporation in different gypsifereous soils

A laboratory study have been conducted to investigate the influence of sprinkler water droplets energy generated from nozzles with two flow rates (9 and 15 mm.hr-1) on soil aggregates and the displacement of soil particles in some gypsifereous soil samples. Five soil samples with different gypsum contents were prepared by mixing between low and high gypsum content soil samples. These soils were sampled from AP and C of profile horizons. The prepared soil samples of different gypsum contents were G0 (83), G1 (133), G2 (211), G3 (472) and G4 (592) gm.kg-1. After the incubation of the prepared for two months, the soil samples were passed through sieves of 2 and 4 mm openings to obtain soil aggregates ranged between 2- 4mm diameters. The soil aggregates were packed with a 6 mm thickness (13 gm) in a plastic tube underlined by pure sand with 26 cm length and an inner diameter of 5 cm. The tubes were placed in a moveable circular base with a 60 cm diameter and a circumference of 188.4 cm. The soil sample tubes were distributed randomly with a 37.6 cm separating distance separating. Each tube sets were subjected to 9 and 15 mm.h-1 sprinkler flow rates. The droplets size distribution for each sprinkler flow rate was studied as well as the droplets energy.The results showed that the droplets energy were increased with increasing droplets size and sprinkler flow rate. Maximum droplet energy was obtained with 1.5 mm droplet diameter, while the minimum droplet energy was obtained with 0.18 mm. Silt and clay transportation were decreased with increasing soil gypsum content under the two sprinkler flow rates. The high flow rate sprinkler was more effective on silt and clay transporting.

Evaluation of the Impermeability of a Curtain Formed from Alluvial Clayey Loams Based on Study of the Microstructure of the Soil and Filtration Investigations

Results of complex investigations of the microstructure and filtration strength of alluvial clayey loams used for experimental backfilling of a curtain for the ash dump at the Ryazan’ state regional power plant are presented. It is demonstrated that clayey loams with a plasticity index of more than 0.10 dec. units can be layered in a curtain with the in situ moisture content and, moreover, should be mandatorily compacted to a state characterized by an average degree of saturation of 0.9. The permeability of the clayey loams compacted in this manner is diminished by tens of thousands of times with respect to the in situ structure. The clayey loams in the curtain are characterized by essentially homogeneous and a slightly oriented matrix microstructure, exhibit high impermeability, and take up pressure differentials of up to 400 with no internal displacement of soil particles.

A soil cultivating roller

Structure and operation principle of an improved soil cultivating roller are given. Interaction between teeth and perforations on roller plates and cultivated soil prevents the displacement of soil particles to one of roller side faces. It ensures the uniformity of both cultivation depth and soil density, which are necessary for further high-quality sowing.

Can Infrared Spectroscopy Be Used to Measure Change in Potassium Nitrate Concentration as a Proxy for Soil Particle Movement?

Displacement of soil particles caused by erosion influences soil condition and fertility. To date, the cesium 137 isotope (137Cs) technique is most commonly used for soil particle tracing. However when large areas are considered, the expensive soil sampling and analysis present an obstacle. Infrared spectral measurements would provide a solution, however the small concentrations of the isotope do not influence the spectral signal sufficiently. Potassium (K) has similar electrical, chemical and physical properties as Cs. Our hypothesis is that it can be used as possible replacement in soil particle tracing. Soils differing in texture were sampled for the study. Laboratory soil chemical analyses and spectral sensitivity analyses were carried out to identify the wavelength range related to K concentration. Different concentrations of K fertilizer were added to soils with varying texture properties in order to establish spectral characteristics of the absorption feature associated with the element. Changes in position of absorption feature center were observed at wavelengths between 2,450 and 2,470 nm, depending on the amount of fertilizer applied. Other absorption feature parameters (absorption band depth, width and area) were also found to change with K concentration with coefficient of determination between 0.85 and 0.99. Tracing soil particles using K fertilizer and infrared spectral response is considered suitable for soils with sandy and sandy silt texture. It is a new approach that can potentially grow to a technique for rapid monitoring of soil particle movement over large areas.

Measurement of Soil Deformation at the Ground Contact Surface of a Traveling Wheel

In order to clarify the soil deformation at the ground contact surface, traveling tests using a rubber-coated rigid wheel were carried out with -5%, 5%, 10%, 20% and 40% slip using a sophisticated soil bin test apparatus. The displacement of soil particles at the ground contact surface was observed through the movement of acrylic wires (1 mm in diameter) laid down on the soil surface. PTV (Particle Tracking Velocimetry), an effective image processing technique, was employed to detect the movement of the acrylic wires using image processing of a series of pictures. The detected movement is assumed to coincide with that of soil particles at the same position. Accordingly, the movement of soil particles could be successfully measured and analyzed. In addition, the soil deformation under the wheel was also measured using PIV (Particle Image Velocimetry). Both measures were then analyzed and the characteristics of soil deformation clarified. The mathematical model for the soil displacement at the ground contact surface showed good agreement with the measured values, except for at high slip.

Effects of decreasing soil water content on seminal lateral roots of young maize plants

AbstractSoil micropores that contain water at or below field capacity cannot be invaded by seminal or first‐order lateral roots of maize plants because their root diameters are larger than 10 μm. Hence, at soil‐water levels below field capacity plant roots must establish a new pore system by displacement of soil particles in order to access soil water. We investigated how decreasing soil water content (SWC) influences growth and morphology of the root system of young maize plants. Plants were grown in rhizotrons 40 cm wide, 50 cm high, and approximately 0.7 cm thick. Five SWC treatments were established by addition of increasing amounts of water to soil and thorough mixing before filling the rhizotrons. No water was added to treatments 1–4 throughout the experiment. Treatment 5 was watered frequently throughout the experiment to serve as a control. Seminal‐root length and SWC in soil layers 0–10, 10–20, 20–30, 30–40, and 40–50 cm were measured at intervals of 2–3 d on scanner images by image analysis. At 15 d after planting, for treatments 1–4 shoot dry weight and total root length were directly related to the amount of water added to the soil, and for treatments 4 and 5, total root length and shoot dry weights were similar. Length of seminal roots visible at the transparent surface of the rhizotron for all treatments was highest in the uppermost soil layer and decreased with distance from the soil surface. For all layers, seminal‐root elongation rate was at maximum above a SWC of 0.17 cm3 cm–3, corresponding to a matric potential of –30 kPa. With decreasing SWC, elongation rate decreased, and 20% of maximum seminal root elongation rate was observed below SWC of 0.05 cm3 cm–3. After destructive harvest for treatment 1–4, number of (root‐) tips per unit length of seminal root was found uninfluenced over the range of initial SWC from 0.10 to 0.26 cm3 cm–3. However, initial SWC close to the permanent wilting point strongly increased number of tips. Average root length of first‐order lateral (FOL) roots increased as initial SWC increased, and the highest length was found for the frequently watered treatment 5. The results of the study suggest that the ability to produce new FOL roots across a wide range of SWC may give maize an adaptive advantage, because FOL root growth can rapidly adapt to changing soil moisture conditions.

Composition, Fabric, and Porosity of an Arenic Haplustalf of Northeast Thailand

Sandy uplands of northeast Thailand have subsoils with high resistance to root penetration that varies even though there is no variation in bulk density (Db). The objective of this study was to determine how the resistance to penetration in these soils is related to the size, mineralogy, and arrangement of the elementary particles. We studied the tilled topsoil (Ap horizon), upper subsoil (E horizon), and lower subsoil (Bt horizon) of an Arenic Haplustalf. Results showed similar skeleton grain‐size distribution in the three horizons. Results also showed similar Db in the E and Bt horizons, and higher resistance to penetration in the E horizon. Dispersion of the material indicated the absence of a cementing agent between elementary particles. The <2‐μm fraction content was 37, 53, and 88 g kg−1 in the Ap, E, and Bt horizons, respectively, and that fraction was about one‐third quartz. The clay minerals were kaolinite with a small amount of swelling 2:1 clays in the Ap and Bt horizons. Mercury porosimetry and scanning electron microscopy (SEM) showed a closer arrangement of the sand resulting in less interparticle porosity in the E horizon than in the Bt horizon. The smaller interparticle porosity in the E horizon was compensated for by greater macroporosity resulting from biological activity, thus explaining the similar Db in the E and Bt horizons. Despite similar Db, the greater penetration resistance in the E horizon results from a close packing of sand particles that restricts the displacement of soil particles during penetration by probe or roots.

Composition, Fabric, and Porosity of an Arenic Haplustalf of Northeast Thailand

Sandy uplands of northeast Thailand have subsoils with high resistance to root penetration that varies even though there is no variation in bulk density (Db). The objective of this study was to determine how the resistance to penetration in these soils is related to the size, mineralogy, and arrangement of the elementary particles. We studied the tilled topsoil (Ap horizon), upper subsoil (E horizon), and lower subsoil (Bt horizon) of an Arenic Haplustalf. Results showed similar skeleton grain-size distribution in the three horizons. Results also showed similar Db in the E and Bt horizons, and higher resistance to penetration in the E horizon. Dispersion of the material indicated the absence of a cementing agent between elementary particles. The <2-μm fraction content was 37, 53, and 88 g kg−1 in the Ap, E, and Bt horizons, respectively, and that fraction was about one-third quartz. The clay minerals were kaolinite with a small amount of swelling 2:1 clays in the Ap and Bt horizons. Mercury porosimetry and scanning electron microscopy (SEM) showed a closer arrangement of the sand resulting in less interparticle porosity in the E horizon than in the Bt horizon. The smaller interparticle porosity in the E horizon was compensated for by greater macroporosity resulting from biological activity, thus explaining the similar Db in the E and Bt horizons. Despite similar Db, the greater penetration resistance in the E horizon results from a close packing of sand particles that restricts the displacement of soil particles during penetration by probe or roots.

Sediment enrichment ratios after mechanical site preparation for Pinus radiata plantation in the Basque Country

The enrichment of organic matter, total nitrogen, phosphorus, and exchangeable calcium, magnesium, sodium, and potassium in runoff sediment was studied by means of sediment traps in two steep slopes (25–34°) for a period of 18 months after site preparation (scalping and down-slope ripping) for Pinus radiata plantation. Total nitrogen concentration was significantly higher in the source soils than in their sediments. Phosphorus, and exchangeable calcium, magnesium, and potassium concentrations were higher in the sediments, although not significantly. No relation was found between sediment enrichment ratios and total rainfall and rainfall intensity. Steep slopes and hydraulic soil-surface conditions favourable to runoff production are suggested to govern the high erosive power of runoff, which results in a nonselective displacement of soil particles. In spite of this lack of enrichment of the sediments, surface soil samples taken 18 months after site preparation showed significantly lower concentrations of organic matter, total nitrogen, phosphorus, and exchangeable magnesium, sodium, potassium, and aluminium, and higher aluminium saturation of the exchange complex in relation to samples taken before site preparation. Removal of the nutrient-rich organic and mineral surface horizons by scalping, rather than soil water erosion taking place afterwards, is the process responsible for most of the decrease in soil nutrient concentration occurring as a result of site preparation.

Modification of silt microstructure by hydrocarbon contamination in freezing ground

AbstractThe thermodynamic conditions within the active layer overlaying perennially frozen ground and in ground subjected to seasonal frost are such that there is continuing translocation of water and ice and the displacement of soil particles. The introduction of an immiscible hydrocarbon contaminant (Arctic diesel fuel) into this dynamic porous medium results in microstructural changes that take place as a function of both cryogenic processes and contaminant concentration. Micromorphological and scanning electron microscope observations combined with image analysis revealed evidence of reorganisation of silt microfabric and changes to intra-particle porosity. The degree of interaggregate porosity increased as a function of increasing concentration of the hydrocarbon contaminant. Intra-particle porosity within individual soil aggregates was observed to decrease as a function of increasing contaminant concentration.

A measurement of basic mechanical quantities of off-the-road traveling performance

A new test apparatus was developed for the precise measurement of mechanical properties related to the traveling performance of off-road vehicles. In particular the apparatus is capable of performing the experiment under the condition of constant contact load between the wheel and the soil, which most of the existing apparatus do not fulfill satisfactorily, and of measuring the displacement of soil particles beneath the wheel. The test results obtained by the apparatus for a rigid wheel on sand are discussed with some mechanical interpretations.