This study explores a novel stabilization technique combining Persian gum (PG), an eco-friendly biopolymer, and glass fiber (GF) to enhance the strength and durability of fine-grained soils under freeze-thaw (F-T) cycles. Specimens were prepared at maximum dry density (MDD) with varying PG and GF contents, cured for 0, 7, or 14 days, and subjected to 0, 5, 7, or 10 F-T cycles. Tests included Standard Proctor compaction, Scanning Electron Microscopy (SEM), Unconfined Compressive Strength (UCS), and Direct Shear (DS). Results demonstrated that GF significantly improved durability, ductility, and strength by enhancing interparticle interaction and friction angle. The results indicated that at an optimum GF content of 1%, UCS and E-5(0) increased by up to 35%. Also, after 10 F-T cycles, UCS decreased by 46% for untreated soil and 36% for treated soil. PG enhanced cohesion through interparticle bonding, which was curing-time-dependent. Specimens with 2.5% PG (optimum content) showed a 133% UCS increase after 14 days of curing but a 9% reduction after 5 F-T cycles, with 70% of total UCS loss occurring in the first 5 cycles. The tests indicated that formation of large and stable soil-PG-GF matrix with improved rigidity, strength, and F-T resistance. The results demonstrated that the suggested soil stabilization method, which utilizes low-cost, eco-friendly materials, was effective.

The instability of clay soil as a road subgrade due to its high shrinkage properties, results in frequent road damage. Therefore, adequate soil improvement is required to improve soil performance in order to satisfy post-construction stabilization requirements. Soil improvement is one of the efforts made to overcome it, such as the soil stabilization method. In recent years there has been an increase in research related to the chemical soil stabilization to improve the physical and mechanical properties of soils. The addition of chemicals such as palm bunch ash, lime, fly ash, and cement to clay soil results in hydration and pozzolanic reactions. This process results in changes in the physical and mechanical properties of the soil. The degree of soil stabilization is influenced by the type of additive, additive content, length of treatment, and soil mineralogy. This study discusses the changes that can affect clay soil when chemical stabilization is carried out, based on information provided by the authors.

Hydrothermal solidification offers an effective, sustainable method for stabilizing clay soil, addressing environmental concerns while improving geotechnical properties. Facilitating pozzolanic reactions between lime and clay under controlled temperature and pressure significantly enhances compressive strength and soil durability. This process promotes calcium silicate hydrate (C-S-H) formation, reduces industrial waste, and supports lime reuse, making it an energy-efficient soil improvement approach. This study investigates the impact of lime addition (0-20%) and various chemical and physical parameters on clay soil compressive strength. Key chemical components include SiO2 (20.1-76.9%), Al2O3 (7.6-34.8%), Fe2O3 (0.6-32.9%), CaO (0.1-43.5%), MgO (0-9.56%), Na2O (0.01-2.8%), and K2O (0.1-3.9%). Physical properties such as density, plasticity index (6-34.5%), and liquid limit (24-65.2%) were analyzed alongside process parameters like heating temperature (60-1000 degrees C), curing time (0-120 days), and curing temperature (20-41 degrees C). Using a dataset of 152 samples divided into training and testing groups, the statistical analysis focused on the leaching coefficient (Lc) and silica-sesquioxide ratio (Kr). Lc emerged as the most significant factor, achieving an R2 of 0.89 and an RMSE of 1.13 MPa. This study found that the compressive strength of lime-treated clay soils varied from 0.02 MPa to 11.9 MPa, influenced by lime concentration, chemical composition, and processing factors. Increased lime additions, particularly when combined with hydrothermal treatment, led to significant strength enhancements owing to improved pozzolanic activity. The plasticity index (PI) markedly diminished with lime stabilization, enhancing workability and mitigating volumetric variations. The density of treated soils rose from 0.8 g/cm3 to 2.1 g/cm3, signifying improved particle compaction and less porosity. The mechanical enhancements indicate that hydrothermal solidification efficiently converts expanding clay into a robust and stable material appropriate for geotechnical applications. Increased Lc improved compressive strength through enhanced pozzolanic activity and density, while higher Kr values, indicating lower CaO availability, yielded limited strength gains. Lc consistently outperformed Kr and other chemical compositions in enhancing clay soil compressive strength.

Due to the increasing frequency of extreme weather events, drought damage to trees threatens forestry production and forest ecosystems worldwide. Assessing the site conditions under which trees are vulnerable to drought damage provides key information for the establishment of countermeasures to prevent such damage. This study aimed to clarify the differences in drought vulnerability of young planted forests between regions and species by using forest insurance claims from all over Japan as a damage indicator. We targeted the two most damaged species in two of the most drought-affected regions from 2016 to 2021. Although landform and soil type were found to be influential factors in the Kamikawa Subprefecture of Hokkaido, these factors did not affect the drought damage in Yamaguchi Prefecture. In Kamikawa, the drought damage risk was high for Larix kaempferi on river terraces and for Abies sachalinensis on mountain areas with compacted brown forest soil. Clayey soil, which can prevent plants from absorbing water, has been known to distribute on the terraces and the mountains with compacted soil in Kamikawa. Therefore, our analysis identified clayey soil as a cause of drought vulnerability in Kamikawa. In addition, L. kaempferi was suggested to be especially vulnerable on flat terraces with less permeable clayey soil due to root damage associated with excessive soil moisture before drought. This study demonstrated that forest insurance can be used not only for damage compensation, but also as a source of information for identifying region- and species-specific risk factors for meteorological damage in forests.

Fluidisation in saturated subgrades of transport infrastructure is a huge problem in many countries around the world caused by dynamic cyclic loads due to heavy haul trains on railways and heavy trucks on highways. The mechanism of subgrade fluidisation has been experimentally studied to a significant extent. However, numerical studies that have been carried out for studying fluidisation are limited. The first part of the paper includes a critical review of previous studies on the mechanism and the effect of cyclic loading factors on fluidisation. It is vital to conduct a comprehensive study with numerical modelling to simulate the actual field conditions of transport infrastructure to find reliable and cost-effective solutions to mitigate subgrade fluidisation. This goal can be achieved only by choosing a soil constitutive model that can capture the changes to the soil stiffness and strength due to excess pore pressure generation and dissipation, along with accumulated deformations in clay soil subjected to cyclic loading. Therefore, in this study, the SANICLAY constitutive model is selected as the suitable candidate to fulfil those requirements. It is implemented in the ABAQUS/Standard finite element program using the user-developed material subroutine UMAT. In the second part of the paper, the validation of the SANICLAY model that accounts for the anisotropy and structure of natural clay was presented using triaxial test data found in the literature for undisturbed clay. Application of the model to simulate cyclic loading shows that the version of SANICLAY used in the simulations needs modifications to capture the stiffness and strength degradation during cyclic loading.

Environmental vibrations produced often by industrial and construction processes can affect adjacent soils and structures, sometimes resulting in foundation failure and structural damage. The application of confined cells under foundations as a mitigation technique against dynamic sources, such as generators, is investigated in this study. Numerical models were developed using Plaxis 3D software to simulate the effect of a vibrating source on a circular footing, both with and without confined cells filled with sand soil at varying depths and diameters. In these cells, the soil modeling considered compaction loads typical in actual construction conditions. Results indicate that placing a minimum-diameter cell closer to the foundation with adequate penetration depth can significantly enhance dynamic response and reduce subgrade deformation. The effectiveness of confined soil in minimizing displacement amplitude in the foundation is evaluated, revealing an impressive 86% reduction with specific cell dimensions (Hc/D = 0.50 and Dc/D = 1.15). Moreover, peak particle velocity and excess pore water pressure at monitored points in the surrounding environment experience reductions of 62% and 87%, respectively, demonstrating substantial vibration attenuation. The study does effectively highlight the novelty of the confined sand cell approach, positioning it as a more targeted, efficient, and cost-effective alternative to existing methods, especially for conditions where large-scale, deep vibrations are a concern.

Clay is one type of soil frequently used as a subgrade. Clay soils as subgrade soils with poor performance are found in expansive, soft, and very soft clays. The clay soils have low CBR value and low bearing capacity. Problematic soil characteristics can interfere with the performance of the road construction above it. Inadequate subgrade soils require improvement with soil stabilization to improve characteristic properties. Therefore, an experiment was conducted by adding marble ash to clay soil to improve soil characteristics and increase the CBR value. The research method was conducted through field testing, laboratory testing, and physical model testing in a test box. This research utilized the addition of marble ash content of 3%, 6%, 9%, and 12%, which were mixed with clay soil in thicknesses of 10 cm, 20 cm, and 30 cm. The results showed that the increase in CBR value for 6-12% marble ash is not much different. The average increase in CBR for 6% marble ash is 5.11 times, for 9% marble ash is 5.28 times, and for 12% marble ash is 5.70 times, while for 3% marble ash, it is only around 2.99 times. The minimum CBR value of 5% for subgrade soil was obtained at 6% marble ash content with a soil thickness of about 20-30 cm. CBR values above 5% can be used as a subgrade for road construction.

Foundation elements with rough (textured) surfaces mobilize larger interface shear resistance than ones with conventional smooth or random rough surfaces when sheared against soils under monotonic loading. The overall performance of foundation elements such as piles supporting offshore wind turbines, suction caissons supporting tidal energy converters, soil nails, and soil anchors installed in cohesive soils could be enhanced through utilizing rough (textured) surfaces to resist applied static and/or cyclic loading. This paper describes the shear behavior of smooth and rough (textured) surfaces in kaolinite clay and kaolinite clay-sand mixture soils under static and cyclic axial loading. The experimental investigation presented herein consists of a series of interface shear tests performed on 3D printed rough (textured) surfaces and a 3D printed smooth reference surface utilizing the Cyclic Interface Shear Test system. The paper includes a description of the interface testing system components, cohesive soil specimens' preparation procedure, smooth and rough (textured) surfaces details, testing procedure, and results of static and cyclic tests. Test results indicate that kaolinite clay-sand mixture soil mobilized larger static and post-cyclic interface shear resistance and volume contraction relative to kaolinite clay soil when sheared against the smooth reference surface. When tested against rough (textured) surfaces with variable asperity height, larger shear resistance was mobilized and larger soil dilation greater than that mobilized by the reference untextured surface in both soils. The results also indicate rough (textured) surfaces exhibited a prevalent frictional anisotropy increases with asperity angle and height in cohesive soils, the surfaces mobilized larger shear resistance and volume change in one direction (i.e., against the asperity right-angled side) than the other direction (i.e., along the asperity inclined side).

The present study aimed to assess the potential of a bio-inspired algorithm, multi-objective grey wolf optimization algorithm (MOGWO), to optimize the strength properties (California bearing ratio (CBR) and unconfined compressive strength (UCS)) of an expansive subgrade soil. This optimization process involves the use of two additives, namely a bio-polymer, pregelatinized corn starch (PGCS), and a nanoparticle agro waste, rice husk ash (RHA), blended with the soil in different mix ratios determined by a 32 factorial experimental design. The CBR samples were cured for 7 days, while the UCS samples were cured for 1, 7, and 28 days. To optimize the expansive subgrade soil strength, regression models were developed using PGCS and RHA as predictors for CBR and UCS, serving as fitness functions in the slightly modified MOGWO optimization technique. Next, the optimization analysis produced non-dominated solutions. The results obtained from the laboratory experiments and optimization analysis revealed that there was significant improvement in the UCS and CBR of the soil. These improvements can be attributed to the pozzolanic reaction between the soil-RHA matrix, the formation of intercalated and exfoliated nanocomposites, and the hydrophilic interaction of PGCS. By applying the slightly modified MOGWO technique, the study achieved optimal enhancements in UCS (710.3 kN/m2) and CBR (24.2%) when the expansive subgrade soil was mixed with 0.2637% PGCS and 12.2413% RHA. The results demonstrate the potential of the MOGWO technique in improving the properties of expansive subgrade soil.

Olden adobe structures had been commonly built on raw clayey earth hence the technique was exposed to be an eco-green and globally sustainable construction. Nowadays, modern construction materials lack long-lasting stability, affordability, and eco-friendliness. On the other hand, overutilization of earth-based materials led to the depletion of natural resources. So, global construction societies were raised to develop organic construction for an eco-friendly environment. This paper reviewed the recent research on the earthen clay adobe bricks and mortar stabilized with Agro-wastes and how they contended with adaptability and stability standards. The literature study focuses on the ability of the rejuvenated clay adobes rather than the traditional clay adobes of historical times. Agro-waste, non-agro-waste, and some synthetic components were used to enhance the adobe's mechanical, durable, and thermal behavior. This review emphasized altering raw clay and Agro-waste or waste additives by endorsing W/B proportions. From the literature, the scientific interpretations were conferred to attain possible usage of alternate binders and Agro-waste additives with viable W/B ratio. The prime findings of this review were subjected to define modifications of raw clay by adding disposal wastes and alternate binders to resolve the shortage of raw clay resources. Nominal mixing strategies of altered clay bricks are to be prescribed since adobes have no specific standards. The renovations of earthen adobe construction are essential to progress and to satisfy commercial needs as an environmentally sustainable material.