Clayey Soils Research Articles

Morphology characterization of unsaturated soils under drying-wetting cycles: crack opening and closure

AbstractThe volumetric and hydrological responses of clayey soils subjected to drying-wetting (D-W) cycles are of paramount importance for the integrity of geoenvironmental infrastructures. The study aimed to investigate the cracking behavior of clayey soils under D-W cycles by using advanced 2D imaging and 3D scanning techniques to capture the initiation and propagation of desiccation cracks within a soil specimen. The temporal variation in the soil water content and the corresponding 2D digital photography and 3D morphology of cracks were simultaneously monitored, and the cracking characteristics were interpreted. It was found that the time-dependent evaporation process was independent of the D-W cycles. Both 2D and 3D characterization showed the cracking hysteresis phenomenon in the unsaturated soil, which indicates the dependency of the crack opening and closure on the degree of saturation. D-W cycles led to the formation of subcracks and the increase in the total crack length, reflecting the soil degradation. Additionally, it was demonstrated that the 3D characterization exhibited the advantage of capturing the volumetric change and the subtle change in the macroporosity of the cracked soil over the 2D visualization. The current study provides a perspective of combining 2D and 3D characterization for interpreting the volumetric change of cracked soils and enhancing the understanding of the hydromechanical responses and the soil-atmosphere interactions.

Effect of Moisture Content and Wet–Dry Cycles on the Strength Properties of Unsaturated Clayey Sand

Based on the actual situation of the project on the Weihai–Yanhai Expressway section of Rongwu Expressway, the effects of water content change and the dry–wet cycle on the mechanical behavior of unsaturated clayey sandy soil were analyzed in this study. In this study, ventilated undrained triaxial shear tests were carried out on unsaturated clayey sandy soils with different water contents (6%, 8%, 10%, 12%, 14% and 16%). Concurrently, the soil samples were subjected to three distinct wet and dry cycle pathways (2~22%, 2~12%, and 12~22%) to gain an understanding of how the mechanical features of the soil changed under the different conditions. The test findings demonstrate that when the water content increases, the unsaturated clayey sandy soil’s cohesiveness and shear strength diminish. The strength of shear decline exhibits a pattern of first being quick, followed by sluggish. The strength of shear and cohesiveness of clayey sandy soil declined under the influence of the dry and wet cycles, with the first cycle primarily affecting variations in cohesiveness and strength of shear. Furthermore, the strength of shear and cohesiveness of clayey sandy soil diminish more with increasing wet and dry cycle amplitude and upper water content limits. Lastly, the drying shrinkage and hygroscopic expansion of clay particles in clayey sandy soils during wet and dry cycles are not significant, resulting in less structural damage and deterioration of the mechanical properties of the soils. The study’s findings have a significant impact on the durability of roadbeds made of unsaturated clayey sandy soil in both wet and dry situations.

Optimizing properties of clayey soil using lime and waste marble powder: a sustainable approach for engineering applications

Several studies have explored the potential of waste marble powder (WMP) and lime (LM) as solutions for issues associated with clayey soils. While WMP enhances mechanical properties and addresses environmental concerns, LM effectively improves soil characteristics. This research investigates the efficacy of LM and WMP, both individually and in combination, in addressing challenges specific to clayey soils in Bouzaroura El Bouni, Algeria. These soils typically exhibit low load-bearing capacity, poor permeability, and erosion susceptibility. LM demonstrates promise in enhancing soil properties, while WMP not only addresses environmental concerns but also enhances mechanical characteristics, providing a dual benefit. The study utilizes a three-variable experiment employing Response Surface Methodology (RSM) Box-Behnken Design, with variations in clay content (88%–100%), LM treatment (1.5%–9%), and WMP inclusion (1.5%–9%). Statistical analysis, including ANOVA, reveals significant patterns with p-values <5%. Functional relationships between input variables (clay, LM, and WMP) and output variables (cohesion, friction angle, and unconfined compressive strength) are expressed through high determination coefficients (R2 = 99.84%, 77.83%, and 96.78%, respectively). Numerical optimization identifies optimal mixtures with desirability close to one (0.899–0.908), indicating successful achievement of the objective with 88% clay content, 3% LM, and 6% WMP. This study provides valuable insights into optimizing clay soil behavior for environmental sustainability and engineering applications, emphasizing the potential of LM and WMP as strategic additives.

Effect of Humic Amendment on Selected Hydrophysical Properties of Sandy and Clayey Soils

In recent years, products containing humic acids have been increasingly used in agriculture to improve soil parameters. Quantifying their impact on soil quality is, therefore, of key importance. This study seeks to evaluate the impact of the commercial humic acid product (HA) on the hydrophysical parameters of sandy and clayey soils sampled from different sites in Slovakia. Specifically, the study hypothesizes that humic amendment will enhance particle density (ρs), dry bulk density (ρd), porosity (Φ), saturated hydraulic conductivity (Ks), soil water repellency (SWR), and water retention capacity in sandy and clayey soils. The results of the laboratory measurements were analyzed using NCSS statistical software at a statistical significance of p < 0.05. In sandy soil, there was a statistically significant decrease in ρd and Ks and an increase in Φ and a contact angle (CA) after the application of 1 g/100 cm3 HA. At a dose of 6 g/100 cm3 HA, the values of ρs, ρd, and Ks decreased, and the Φ and CA values increased. In clayey soil, the Ks value significantly decreased by −35.5% only after the application of 6 g/100 cm3 HA. The addition of HA increased the full water capacity (FWC) and available water capacity (AWC) of clayey and sandy soils. The positive influence of HA on the studied soil parameters was experimentally confirmed, which can be beneficial, especially for their use in agricultural production.

Improvement of Geotechnical Properties of Clayey Soil Using Biopolymer and Ferrochromium Slag Additives

The geotechnical properties of clay soil and its mixtures with different proportions (0.75%, 0.85%, 1%, and 1.15%) of Agar Gum biopolymer and Ferrochromium Slag (0.25%, 0.50%, 0.75%, and 1%), having various curing times and freeze-thaw cycles, were studied through a series of soil mechanical tests to investigate possibilities to improve its undesired/problematic plasticity, compaction, and shear strength characteristics. The results revealed that treatment with an optimal ratio of 1% Agar Gum and 1% Ferrochromium Slag alone, as well as together with, improved the geotechnical properties of the clay soil considerably. Both the unconfined and shear strength properties, along with the cohesion and internal friction angle, increased as much as 47 to 173%, depending on the curing time. The higher the curing time, the higher the shear strength, cohesion, and internal friction angle are up to 21 days. Deteriorating the soil structure and/or fabric, freeze-thaw cycles, however, seem to have an adverse effect on the strength. The higher the freeze-thaw cycle, the lower the shear strength, cohesion, and internal friction angle. Also, some improvements in the plasticity and compaction properties were determined, and environmental concerns regarding Ferrochromium Slag usage have been addressed.

Experimental and numerical settlement analysis of railway track over geogrid reinforced ballast

PurposeThe main objective of the present research is to investigate the benefits of using geogrid reinforcement in minimizing the rate of deterioration of ballasted rail track geometry resting on soft clay and to explore the effect of load amplitude, load frequency, presence of geogrid layer in ballast layer and ballast layer thickness on the behavior of track system. These variables are studied both experimentally and numerically. This paper examines the effect of geogrid reinforced ballast laying on a layer of clayey soil as a subgrade layer, where a half full scale railway tests are conducted as well as a theoretical analysis is performed.Design/methodology/approachThe experimental tests work consists of laboratory model tests to investigate the reduction in the compressibility and stress distribution induced in soft clay under a ballast railway reinforced by geogrid reinforcement subjected to dynamic load. Experimental model based on an approximate half scale for general rail track engineering practice is adopted in this study which is used in Iraqi railways. The investigated parameters are load amplitude, load frequency and presence of geogrid reinforcement layer. A half full-scale railway was constructed for carrying out the tests, which consists of two rails 800 mm in length with three wooden sleepers (900 mm × 90 mm × 90 mm). The ballast was overlying 500 mm thick clay layer. The tests were carried out with and without geogrid reinforcement, the tests were carried out in a well tied steel box of 1.5 m length × 1 m width × 1 m height. A series of laboratory tests were conducted to investigate the response of the ballast and the clay layers where the ballast was reinforced by a geogrid. Settlement in ballast and clay, was measured in reinforced and unreinforced ballast cases. In addition to the laboratory tests, the application of numerical analysis was made by using the finite element program PLAXIS 3D 2013.FindingsIt was concluded that the settlement increased with increasing the simulated train load amplitude, there is a sharp increase in settlement up to the cycle 500 and after that, there is a gradual increase to level out between, 2,500 and 4,500 cycles depending on the load frequency. There is a little increase in the induced settlement when the load amplitude increased from 0.5 to 1 ton, but it is higher when the load amplitude increased to 2 ton, the increase in settlement depends on the geogrid existence and the other studied parameters. Both experimental and numerical results showed the same behavior. The effect of load frequency on the settlement ratio is almost constant after 500 cycles. In general, for reinforced cases, the effect of load frequency on the settlement ratio is very small ranging between 0.5 and 2% compared with the unreinforced case.Originality/valueIncreasing the ballast layer thickness from 20 cm to 30 cm leads to decrease the settlement by about 50%. This ascertains the efficiency of ballast in spreading the waves induced by the track.

Effect of Subbase Stabilization on the Bearing Capacity of Footing Resting on Clayey Soil

Effect of Subbase Stabilization on the Bearing Capacity of Footing Resting on Clayey Soil

Multi-scale analysis of carbon mineralization in lime-treated soils considering soil mineralogy

Mineral carbonation is emerging as a reliable CO2 capture technology that can mitigate climate change. In lime-treated clayey soils, mineral carbonation occurs through the carbonation of free lime and cementitious products derived from pozzolanic reactions. The kinetics of the reactions in lime-treated clayey soils are variable and depend primarily on soil mineralogy. The present study demonstrates the role of soil mineralogy in CO2 capture and the subsequent changes caused by carbon mineralization in terms of the unconfined compressive strength (UCS) of lime-treated soils during their service life. Three clayey soils (kaolin, bentonite, and silty clay) with different mineralogical characteristics were treated with 4% lime content, and the samples were cured in a controlled environment for 7 d, 90 d, 180 d, and 365 d. After the specified curing periods, the samples were exposed to CO2 in a carbonation cell for 7 d. The non-carbonated samples purged with N2 gas were used as a benchmark to compare the mechanical, chemical-mineralogical, and microstructure changes caused by carbonation reactions. Experimental investigations indicated that exposure to CO2 resulted in an average increase of 10% in the UCS of lime-treated bentonite, whereas the strength of lime-treated kaolin and silty clay was reduced by an average of 35%. The chemical and microstructural analyses revealed that the precipitated carbonates effectively filled the macropores of the treated bentonite, compared to the inadequate cementation caused by pozzolanic reactions, resulting in strength enhancement. In contrast, strength loss in lime-treated kaolin and silty clay was attributed to the carbonation of cementitious phases and partly to the tensile stress induced by carbonate precipitation. In terms of carbon mineralization prospects, lime-treated kaolin exhibited maximum carbonation due to the higher availability of unreacted lime. The results suggest that, in addition to the increase in compressive strength, adequate calcium-bearing phases and macropores determine the efficiency of carbon mineralization in lime-treated clayey soils.

Characterization of Lateralite: An Environment Friendly Chemical Additive for Soil Stabilization

The objective of this paper is to determine the chemical composition of Lateralite stabilizer and to characterize Lateralite, stabilizer as a solution for improving the engineering properties of fined grained lateritic and clayey soil for road construction. Oxides and metallic compositions of Lateralite was determined by Atomic Absorption Spectroscopy, AAS, composition of chemical elements of Lateralite stabilizer was determined by X-ray Photoelectron Spectroscopy (XPS) and a quantitative analysis by Scanning Electron Microscopy (SEM) associated with Energy Dispersive X-ray spectroscopy (EDX). The oxide composition of Lateralite as determined by AAS is: Calcium Oxide (63.89%), Silicon Oxide (18.31%), Aluminium Oxide (5.89%), Ferrous oxide (1.67%), Magnesium oxide (1.56%), Sulphur oxide (1.22%), Potassium oxide (0.78%), Sodium oxide (0.41%) and L.O.I 6.27%. The elemental composition analysis by XPS revealed ten (10) elements with Percentage Atomic Concentration, PAC, as: Oxygen (54.33%), Carbon (18.26%), Silicon (9.38%), Calcium (7.56%), Magnesium (4.08%), Aluminium (2.90%), Sodium (2.47%), Ferrous (0.44%), Sulphur (0.31%) and Nitrogen (0.27%) while SEM revealed eleven (11) elements: Oxygen (57.9%), Calcium (21.13%), Silicon (11.08%), Aluminium (4.23%), Ferrous (1.89%), Sulphur (1.07%), Magnesium (1.02%), Sodium (0.99%), Potassium (0.35%), Tin (0.18%) and Barium (0.17%). The three (3) characterization techniques used, (AAS, XPS and SEM) revealed the exchangeable cations in Lateralite are Calcium (7.56%), Magnesium (4.08%), Aluminium (2.90%) and Sodium (2.47%) which are in the ratio 3: 1.65:1.17:1, (Ca2+: Mg2+: Al3+ :Na+). This shows a high concentration and quantity of exchangeable calcium cations over other cations. This will enable the formation of Calcium compounds with very strong and stable inter-particle bonds and a stable Lateralite-stabilized soil mixture.

Enhancing in situ remediation of clayey soils contaminated with total petroleum hydrocarbons by combining pneumatic fracturing, plasma blasting, and vacuum extraction: A comprehensive field investigation

Oxidant injection technology is widely used in soil remediation; however, subsurface conditions, including soil properties and permeability, significantly influence its effectiveness. In this study, the potential of the combination of pneumatic fracturing, plasma discharge, and vacuum extraction (PPV) in enhancing soil permeability and remediating field-scale silt/clayey soils contaminated by total petroleum hydrocarbon (TPH) was studied. Improved soil permeability was assessed by measuring the chlorine and H2O2 concentrations in soil samples, and the remediation efficiency of PPV was evaluated by analyzing the TPH concentrations in the soil samples. The initial highest TPH concentration was 6,922mgkg-1; after a 42-day operation period, the TPH levels decreased to 541mgkg-1. The economic assessment of PPV revealed it to be cost-effective, with a total operating cost of US$ 3,077 for remediating 265m³ of contaminated soil, equating to US$ 11.6 per ton of soil. Since PPV requires a short operational period, is inexpensive, and is suitable for purifying low-permeability soil, it is a promising and economically advantageous approach for soil purification. Overall, PPV demonstrated the ability to enhance oxidizing agent transfer by increasing soil permeability, suggesting its potential for efficient and targeted soil remediation.

Pseudo-static analysis of 3D unsaturated bench slopes stabilized by multiple rows of piles

Bench slopes incorporated with multiple rows of anti-slide piles remain an effective technique in landslide disaster preventions and are widely employed in the design of new subgrades and embankments. To provide more realistic results for engineering guidance, the three-dimensional (3D) effect and suction in soils require explicit considerations. Employing the upper bound limit analysis method, a 3D limit analysis of bench slopes stabilized by multiple rows of piles is performed in this paper. The upper bound solutions of several illustrative slopes are optimized and compared with the published ones, indicating the validity of the optimization program and the proposed method. A series of parameter analyses are conducted regarding the roles of suction and anti-slide piles in slope safety assessments. The results show that the suction effect and pile reinforcement increase continually as the pile location increases and the influence of bench width can be ignored. The stability of bench slopes stabilized by multiple rows of piles differ with that of slopes stabilized by single row of piles dramatically. The maximum pile reinforcement reaches 70% for sandy soil slopes but only 30% for clayey soil slopes. The influences of surcharge load and seismic load on the pile reinforcement can nearly be neglected.

Microstructural and mechanical analysis of magnesium chloride stabilization in highly plastic swelling clayey soils

In recent years, there has been an increasing interest in investigating the use of non-traditional additives for stabilizing problematic soils. As the demand for eco-friendly alternatives to cement rises, magnesium chloride, a widely used deicer and dust suppressor, has emerged as a potential choice. This study aims to provide a comprehensive understanding of the microstructural changes that occur and affect the macro behavior of treated bentonite (B) and yellow marl (YM). To achieve this, MgCl2 solution was added to the soils at 3, 6, 9, and 12 percent by dry weight of the soil, and samples were cured for 7, 14, and 28 days at 5°C, 25°C, and 35°C. The mechanical properties of the treated soils were then evaluated using the unconfined compression test, direct shear test, and pressure chamber test (SWCC), while microstructural analysis techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDAX), and Fourier transform infrared spectroscopy (FTIR) were employed to examine the mechanism of MgCl2 stabilization. The results indicate that adding MgCl2 and extending the curing period significantly increased both soils' unconfined compressive strength (UCS). However, the UCS value decreased for treated samples cured at temperatures higher than 25°C due to an incomplete cation exchange process and the reduction of apparent cohesion. A part of the gained strength from apparent cohesion and matric suction in the unsaturated samples was lost when the samples reached full saturation during the direct shear test. Changes in the particle size, pore size, and pore void distribution due to the MgCl2 stabilization affected the SWCCs of the treated soils. Microstructural analyses revealed the formation of magnesium hydration products, such as magnesium silicate hydrate (M-S-H) and magnesium aluminate hydrate (M-A-H), which contributed to the strength increase by increasing grain size, filling the pores, binding fine particles within coarse grains, and forming a flocculated structure through recrystallization of MgCl2 and the formation of cementitious gel. Additionally, for B, adding MgCl2 led to soil flocculation through ion exchange, while for YM, the same process occurred due to the greater surface tension of the saline solution encircling the particles.

Investigational Study on the Influence of Sisal Fiber and Rice Husk Ash in the Stabilisation of Clayey Soil

The process of improving and enhancing the engineering qualities of soil so that it can support large loads without failing is known as "soil stabilization" in the realm of civil engineering. The behavior of the soil was examined in the current work at various proportions following the addition of Rice Husk Ash (fixed at 15%) and sisal fiber (varying at 1.5%, 2.0%, and 2.5%; length 40 mm). Various soil properties, such as OMC, MDD, CBR value, and UCS values, were then quantified. Utilizing Sisal Fiber and Rice Husk Ash together can enhance the diverse engineering features of soil, according to the conclusion of this experimental research project. Laboratory tests such Atterberg's Limits, Specific Gravity, Particle Size Distribution, Standard Proctor test, Unconfined Compressive Strength (UCS), and California Bearing Ratio (CBR) were carried out to examine the engineering qualities of the soil and its mixtures. The results showed that the engineering qualities of clayey soil were significantly enhanced by the addition of Sisal Fiber and Rice Husk Ash. As a result, Sisal Fiber and Rice Husk Ash may act as soil stabilizing agents, making clayey soil a better choice for building foundations. All testing were carried out in accordance with Indian standards regulations. Key Words: Compaction test, CBR, UCS, Rice Husk Ash, Sisal Fiber

USE OF NANO SILICA AND COIR FIBER TO STRENGTHEN THE ENGINEERING PROPERTIES OF CLAYEY SOIL

One of the problematic soils is expansive soil, which has a strong tendency to shrink when dried and to inflate when its moisture level changes. In India, expansive soils made up of clays are referred to as black cotton soils. The alternating swell-shrink tendency of expansive soils results in foundation structures, including buildings and earth retaining wall pavements, to become distressed. For geotechnical engineers, comprehending the behavior of expansive soil and implementing the proper control measures has been a challenging challenge. A lot of study is being done to develop solutions for soils that produce black cotton. This review study uses the soil index and engineering features to examine the behavior of clayey soil stabilized with different proportions of Nano silica and Coir Fiber. Coir is a naturally occurring, biodegradable material that is widely accessible in several coastal and southern regions of India. Nano silica is a type of filler material that increases ductility without compromising strength. With less swelling potential, the generated nano silica functioned as a hydraulic binder. In expansive soils, coir fiber and nano silica are combined for the goal of sustainable development. As part of this comparison study, laboratory tests including Atterberg's limit, Compaction test, CBR test, and UCS test were performed for both modified and unmodified clayey soil. In this work, expansive soil was stabilized using Nano silica and Coir Fiber. Coir Fiber was fixed at 3.5%, after that Nano silica was changed to 2%, 4%, and 6%. Key Words: Compaction test, CBR, UCS, Coir Fiber, Nano Silica

Hymenocallis ruenesiana (Amaryllidaceae), a new species from the Yucatan Peninsula, Mexico

Hymenocallis ruenesiana is described and illustrated as a new species from the Yucatan Peninsula, Mexico. When comparing the morphological characters of the leaf, inflorescence, fruit and pollen, as well as the environmental conditions of the habitat of H. ruenesiana, discontinuities were found with those of Hymenocallis littoralis. Hymenocallis ruenesiana is endemic to the Yucatan peninsula, inhabiting seasonal savannas with clayey and floodable soils, while H. littoralis naturally inhabits the coasts, on easily drained sandy soils and it is also widely cultivated as an ornamental plant.

Impacts on Soil and Cowpea Plants Fertigated with Sanitary Sewage through Subsurface Drip Irrigation

The application of sanitary sewage using subsurface drip irrigation can mitigate current challenges related to water availability and food production. However, before implementing these techniques, it is crucial to conduct studies to assess their impacts on soil and plants. The objective of this study was to evaluate chemical changes in the soil and the development of cowpeas subjected to sanitary sewage applied by drippers with different flow rates and installation depths. Drippers were positioned at various depths (0 to 30 cm) and operated with flow rates of 1.6 and 3.8 L h−1. Cowpeas were cultivated in pots with clayey soil, using synthetic sanitary sewage based on the maximum limit of nitrogen fertilization. Irrigation management was controlled in terms of soil moisture, which was monitored using TDR probes. The results indicated that reducing the depth of the drippers positively affected grain production and the development of cowpeas. Fertigation with sanitary sewage at greater depths increased soil phosphorus concentrations and base saturation. Dripper depth also influenced soil concentrations of phosphorus, potassium, calcium, and magnesium, while sodium concentrations decreased with greater depth. It is concluded that dripper flow rates did not impact soil chemical parameters or the agronomic characteristics of cowpeas. However, despite nutrient supply at greater depths, the subsurface drip irrigation system proved unsuitable for cowpea production in clayey soil.

Experimental Study on the Mechanical Strength, Deformation Behavior and Infiltration Characteristics of Coral Sand

In this investigation, coral sand is presented as a sustainable substitute for conventional river and machine-manufactured sand. This study comprehensively investigated the macro-scale strength, deformation, and permeability characteristics of coral sand, alongside analyzing the mechanical behavior, deformation, and permeability under various conditions and in relation to distinct particle characteristics. It revealed that coral sand primarily consists of biotite and high-Mg calcite, featuring abundant internal pore space. Its compressive properties resemble clayey soils, displaying minimal unloading rebound and predominant plastic deformation during compression. In direct shear tests, the stress–strain relationship follows an approximate hyperbola, with no pronounced strain softening. Describing particle fragmentation in the process proves challenging, making indicators like internal friction angle less applicable in engineering. Triaxial tests indicate a rapid initial bias stress increase, followed by a gradual decrease post-stress peak, suggesting a strain softening phenomenon. As surrounding pressure rises, the axial strain needed to reach peak strength also increases. The permeability coefficient of coral sand correlates linearly with pore ratio increase, represented by 10e. The complex interaction of multiple factors influences the strength, deformation, and permeability of coral sand blown fill mixes, with specimen porosity having the greatest impact. The design and construction of high-weight foundation elements in coral sand blown fill projects should consider porosity effects.

Comparative analysis of nutrient absorption in rice cultivation: Aerobic versus anaerobic conditions in furrow‐irrigated rice

AbstractRice (Oryza sativa L.) production in the Mid‐Southern United States has traditionally been under conventional flood (CF) production, namely, direct‐seeded and delayed‐flood production. However, furrow‐irrigated rice (FIR) has grown to comprise over 15% of Arkansas’ and 30% of Missouri's rice hectarage. The uptake of several nutrients, including phosphorus (P), potassium (K), and zinc (Zn), has been shown to differ between aerobic and flooded rice production. Hence, a nutrient uptake survey was conducted from 2018 to 2020 in FIR fields to determine the difference in nutrient uptake (macro‐ and micronutrients) between the upper generally aerobic environment at the top of the field and the bottom of the field, where a generally anaerobic or flooded environment existed from R1 to maturity. Aboveground biomass samples were taken at R3 from four nitrogen (N) treatments at the top and bottom of five sites on a clayey soil texture and four sites on a loamy soil texture. Results suggest that there is significantly lower P, K, sodium (Na), and manganese (Mn) uptake at the top of the field compared to the bottom of the field on both soil textures. Additionally, the N treatments that yielded the highest biomass generally led to the greatest uptake of all nutrients examined. The decrease in P and K uptake in the aerobic portion of an FIR field suggests that they may require altered fertilizer recommendations compared to the traditional CF rice system.

Influence of desiccation during freeze-thaw cycles on volumetric shrinkage and tensile strength of compacted clayey soils

Tensile strength is a crucial mechanical property that governs the initiation and propagation of soil tensile cracks. With the global prevalence of warming effects and extreme climatic events, the recurrent freeze-thaw (F-T) cycles intensify the complex evolutions of soil pore structure and tensile strength in regions with widespread seasonal freezing or permafrost active layers. This study investigates the combined influence of F-T cycles and desiccation on the tensile strength of clayey soils. Specimens with varying compaction water contents (14.5%, 16.5%, and 18.5%) and dry densities (1.5 Mg/m3, 1.6 Mg/m3, and 1.7 Mg/m3) were prepared and subjected to cyclic F-T actions. A direct tensile test apparatus was utilized to measure tensile strength (σt) along the desiccation path. Additionally, the changes in void ratio (e) and suction (s) during F-T cycles were analyzed to understand the mechanism behind the changes in σt. Experimental results reveal that as the number of F-T cycles (N) increases, water content (w) declines at a decreasing rate and eventually stabilizes. With increasing N, the tensile displacement at failure and σt show a pattern of initially decreasing and subsequently rising, with the inflection point typically around 1.5%–2.0% lower than the compaction water content (w0). Under a few F-T cycles, soils compacted at the optimum water content and on the wet side exhibit higher void ratio and lower suction and σt compared with dry-side compacted soils. However, this trend reverses with further increasing N. In addition, σt increases as compaction dry density (ρd0) rises within all water content ranges, primarily attributed to the significant interparticle cohesion controlled by a dense pore structure. The variation of σt under F-T and associated desiccation is linked with the microstructural evolution characterized by aggregates, interaggregate pores and water-bridges. It is recommended to compact soils both on the dry side of the optimum water content and at the maximum dry density to enhance the freeze-thaw resistance of earth-works in seasonally frozen regions.

Analysis Of Bearing Capacity Of Pile Foundations Using Analytical Method And Finite Element Method

The foundation is the lower part of a structure used as a load distributor for loads generated. The selection of foundation types in building construction must consider the type and characteristics of the soil at the construction site to avoid construction failures. This analysis is conducted to determine the bearing capacity of pile foundations using analytical and finite element methods. The type of foundation used in this analysis is a pile foundation with a pile length of 8 meters and a pile diameter of 0.4 meters. For the analytical calculation, Standard Penetration Test (SPT) data obtained from PT. Adhi Karya (Persero) for the Infrastructure Green House Biodiversity LIPI Cibinong-Bogor project are used, employing the analytical method (Alpha Method) and the finite element method with the assistance of Plaxis 2D V.8 software. The results of the analysis show that the bearing capacity of the group pile foundation (Qg) for a pile diameter of 0.4 meters and a pile length of 8 meters on clayey soil, based on SPT data using the analytical method (Alpha Method), is 60.432 tons. Meanwhile, the bearing capacity of the horizontal pile foundation using the Broms method is 6.03 tons. The bearing capacity obtained using the Finite Element Method yields an ultimate load on the group pile (Qq) of 57.89 tons. The bearing capacity of the group pile foundation (Qg) from both sets of data, with a difference of 2.5%, meets the requirement, being greater than the axial load (P) of 42.6 tons that must be supported.