Weak Soil Research Articles

Underground structures and cultural layers XIX – beginning of XX century in 101 quarters of Samara

The article studied cultural layers and underground structures that were discovered during security and rescue archaeological excavations in the 101 quarter of Samara. The types of foundations of buildings of different ages were identified and an attempt was made to determine the stages of use of the territory for construction. Petrographic study of brick images is described. Natural weak soils were investigated in the territory of 101 quarters of Samara.

The Evaluation of Effect of Jet Grout Columns to the Settlements in Soils with Numerical Methods

Increasing population bring together the need for construction on weak soils. At this point, soil improvement methods gain importance in which the problematic properties of soils aimed to enhance. Among these, jet grout columns are widely applied method and have advantages such as increasing the bearing capacity, reducing settlements and the risk of liquefaction. In this paper, jet grout columns utilized to reduce settlements in weak soil layers and the effect of several parameters on settlement examined. The analyzes, performed with Plaxis 2D and Plaxis 3D. The jet grouts are modeled with both single columns and composite region by changing jet grout length, diameter and spacing. To assess the soft clay effect, columns were socketed into different clay layers. The results proved that improvement with jet grout reduces the settlements, but the change in diameter, length and spacing affects the results at different rates. Through 3D analysis, up to 22% reductions in settlements obtained in case where the longest columns were assigned at the lowest spacings. The most effective factor was found as spacing rather than diameter. The increase in diameter after a certain value led to lower the performance due to the group effect. In case of the composite region, 3D and 2D analyzes converge very much, so it would be practical to perform 2D analysis for the composites. However, the ones modelled with single columns predicted more settlement and remained on the safe side. Additionally, jet grout columns performed better than in weak soils.

Quantitative Evaluation of Soil Erosion in Loess Hilly Area of Western Henan Based on Sampling Approach

The terrain in the loess hilly area of western Henan is fragmented, with steep slopes and weak soil erosion resistance. The substantial soil erosion in this region results in plenty of problems, including decreased soil productivity and ecological degradation. These problems significantly hinder the social and economic development in the region. Soil conservation planning and ecological development require accurate soil erosion surveys. However, the studies of spatio-temporal patterns, evolution, and the driving force of soil erosion in this region are insufficient. Therefore, based on a multi-stage, unequal probability, systematic area sampling method and field investigation, the soil erosion of the loess hilly area of western Henan was quantitatively evaluated by the Chinese Soil Loss Equation (CSLE) in 2022. The impact forces of soil erosion were analyzed by means of a geographic detector and multiple linear regression analysis, and the key driving factors of the spatio-temporal evolution of soil erosion in this region were revealed. The results were as follows. (1) The average soil erosion rate of the loess hilly area in western Henan in 2022 was 5.94 t⋅ha−1⋅a−1, with a percentage of soil erosion area of 29.10%. (2) High soil erosion rates mainly appeared in the west of Shangjie, Xingyang, and Jiyuan, which are related to the development of production and construction projects in these areas. The areas with a high percentage of soil erosion area were in the north (Xinan and Yima), west (Lushi), and southeast (Songxian and Ruyang) of the study area. Moreover, areas with the most erosion were found in forest land, cultivated land, and areas with a slope above 25°. (3) At the landscape level, the number and density of patches of all land types, except orchard land, increased significantly, and the boundary perimeter, landscape pattern segmentation, and degree of fragmentation increased. (4) The geographical detector and multiple linear regression analysis indicated that the driving forces of soil erosion are mainly topographic and climatic (slope length, elevation, precipitation, and temperature). Soil erosion was significantly influenced by the density of landscape patches. These maps and factors influencing soil erosion can serve as valuable sources of information for regional soil conservation plans and ecological environment improvements.

Enhancing Load-Bearing Capacity of Weak Soils Using Geosynthetics: A Finite Element Analysis

In the context of mining applications and the increasing demand for high load-bearing soils, utilizing weak soils poses a significant challenge. This study investigates the effectiveness of geosynthetics in stabilizing weak soils through numerical modeling using Abaqus software (R2016X)and validation via laboratory model testing. We examined the impact of various geosynthetic lengths and embedment depths across three soil types: clay loam (ML), sand (SM), and well-graded sand (SW). Our results reveal that ML and SM soil types exhibit local shear failure, while SW soil types demonstrate general shear failure. Notably, the bearing capacity of soils increases with coarser particle sizes due to higher Meyerhof parameters, leading to soil failure at lower settlements. Optimal geotextile embedment depths were determined as H/B = 0.125 for ML soil, H/B = 0.250 for SM soil, and H/B = 0.5 for SW soil. Additionally, the effect of geotextile length on bearing capacity is more pronounced in ML soil, suggesting greater effectiveness in fine-grained soils. The optimal geotextile lengths for installation are approximately 1.5 times the width for ML soil, 1.0 times for SM soil, and 1.0 times for SW soil. We also found that SW soil typically fails at lower settlements compared to ML and SM soils. Consequently, geotextile placement at shallower depths is recommended for SW soil, where the soil experiences higher tension and pressure. These findings contribute to enhance soil stabilization and load management in mining geotechnics.

Soil erodibility mapping using remote sensing and in situ soil data with random forest model in a mountainous catchment of Indian Himalayas.

Land degradation is accelerating in the Himalayan ecosystem, resulting in the loss of soil nutrients due to severe erosion. Soil erosion presents a significant environmental challenge, resulting in both on-site and off-site consequences, such as reduced soil productivity and siltation in reservoirs. Soil erodibility (K factor), an inherent soil property, determines the susceptibility of soils to erosion. Sampling across hilly and mountainous terrain pose challenges due to its complex landscape. Despite these challenges, it is essential to study K factor variations in different land use/land cover types to comprehend the threat of erosion. Digital soil mapping offers an opportunity to overcome this limitation by providing spatial predictions of soil properties. The objective of our study is to map the spatial distribution of soil erodibility using the Random Forest (RF) model, a machine learning method based on sampled in situ soil data and environmental covariates. We collected 556 surface soil samples from the mountainous catchment (Tehri dam catchment) using the stratified random sampling approach. The model performed satisfactorily in both training (r2 = 0.91; RMSE = 0.00185) and testing (r2 = 0.45; RMSE = 0.00318) phases. Subsequently, we generated a digital map with a resolution of 12.5m to depict the distribution of the K factor. Our analysis revealed that key environmental variables influencing the prediction of the K factor included geology, mean NDVI, and climatic factors. The average K factor value was estimated at 0.0304 and ranging from 0.0251 to 0.0400 t ha h ha-1MJ-1mm-1. A higher K factor was observed in the barren land (0.0344) primarily located in the higher and trans-Himalayan region of seasonally snow-covered areas. These areas typically feature young soils with weak soil formation and unstable soil aggregates. Subsequently cropland/cultivated soils (0.0307) exhibited higher K factor values due to the breakdown of soil aggregates by ploughing activities and exposing carbon to decomposition. The average K factor value of evergreen (0.0294) and deciduous (0.0295) forests were the lowest compared to other land use/land cover types indicating the role of forests in resisting soil erosion. By assessing and predicting soil erodibility, land planners and farmers can implement erosion control measures to protect soil health, prevent sedimentation in water bodies, and sustain agricultural productivity in the Himalayas.

Quantitative analysis of construction risks in shallowly buried biased tunnel portal section

To address the prominent problem of collapse instability in shallow buried soft ground tunnels, a non-invasive stochastic finite element method was introduced. Taking Fujian Puyan Wenbishan tunnel as the background project, ABAQUS finite element software was used to analyze the tunnel excavation mechanics and parameter sensitivity. And developed the software interface program based on Python to output explicit limit state equation for the key mechanical indexes of the tunnel, so as to evaluate the tunnel reliability under different excavation methods, quantitatively. Study results show a significant improvement in efficiency and accuracy when calculating the probability of failure in tunnel excavation by the non-invasive stochastic finite element method. The maximum displacement monitoring points for the Wenbishan tunnel portal section were all vault settlement, with displacements of 33.6 mm, 30.2 mm, and 25.3 mm, respectively, using the annular retained core soil method, single sidewall guide pit and double sidewall guide pit method, with probabilities of failure of 36.11%, 28.03%, and 20.02%. It is found that the reliability of the tunnel is mainly determined by the geotechnical weight, elastic modulus and cohesion of the weak sandy soil layer, which can provide ideas for this type of engineering researches.

Fresh and Hardened Properties of Alkali-Activated POFA-GGBFS Pastes Cured in Ambient Temperature – An Initial Mix Design

Weak soils are characterised by their high compressibility and low shear strength, which requires stabilisation to improve their compaction and strength characteristics before being used for construction projects. Recent trends in soil stabilisation show an increased interest in the application of waste-derived geopolymers as low-carbon materials to address the carbon emission problem related to cement production. This paper presents the preliminary findings of using Palm Oil Fuel Ash (POFA) and Ground Granulated Blast Furnace Slag (GGBFS) binary blends as geopolymer precursor materials. These binary waste material blends were activated using alkaline solutions, namely Sodium Hydroxide (NH) and Sodium Silicate (NS), to synthesise geopolymers at ambient temperatures. Three main factors were considered for the optimisation of the geopolymer mix design, as recommended by past research: alkali equivalent (8-11.5%), activator modulus (0-0.7), and slag replacement (fixed at 30%). Alkali equivalent and activator modulus parameters were varied and tested to establish its initial and final setting times, workability and strength properties, while the slag replacement percentage was set at 30%. This study aimed to determine the most influential parameters to produce the geopolymer material with the highest compressive strength and satisfactory setting times and workability. Single-source alkali activators (NH only) used on POFA-GGBFS produced specimens with smaller flow diameters, longer initial and final setting times, and lower compressive strength than specimens activated with NH and NS. Geopolymer specimens synthesised with NH and NS produce stiffer compounds possessing higher compressive strength values and explosive-type failure modes due to their higher silica content. At ambient temperatures, TM-Mix 2 (7% alkali equivalent and 0.7 activator modulus) produced the highest compressive strength value of 67.3 MPa at 28 days curing, flow diameter of 227 mm, with the initial and final setting time of 25 minutes and 45 minutes, respectively. Consequently, the results show that the preliminary POFA-GGBFS geopolymer mix design could produce sustainably sourced geopolymer compounds with adequate strength and acceptable setting time and workability. This study is part of a current investigation to further optimise the POFA-GGBFS mix design for the purpose of weak soil stabilisation.

Evaluation of the methods used for estimating the bearing capacity of stone columns

Stone columns have been utilized for several decades due to their ability to improve the mechanical behavior of weak and marginal soil deposits. Reducing the cost of a project necessitates accurate estimation of the stone column capacity. This paper considers the existing analytical methods for estimating the bearing capacity of stone columns and evaluate their prediction accuracy. For this purpose, the results of 36 full-scale field tests on footings supported by stone columns are considered, and the measured bearing capacity (QM) are compared with estimated bearing capacity (QE) values computed from 15 analytical solutions predicting the stone column capacity. For this comparison, five statistical approaches are employed in order to evaluate these 15 methods and identify the level of their prediction accuracy. Finally, the methods are ranked by the degree of accuracy with which they can estimate the load capacity. The findings of this research help designers and decision makers to choose a more reliable design method when dealing with stone columns.

Freeze-thaw durability of clayey soils stabilized by alkaline-activated kaolin and recycled cement kiln dust

Weak soils pose significant challenges for civil engineering projects, particularly in cold regions. Stabilizing such soils with additives is a common practice to enhance their geotechnical properties. This research aimed to evaluate the durability of clayey soils stabilized by alkaline-activated kaolin at 10, 25, and 50%, along with 10% recycled cement kiln dust (CKD). The stabilization process involved curing the soils at different temperatures (40, 60, and 80°C) for varying durations (1, 7, 14, and 28 days). The stabilized soils underwent 5, 10, and 20 freeze-thaw (F-T) cycles to evaluate their durability. The results indicated F-T cycling led to a reduction in the unconfined compressive strength (UCS) of unstabilized soils, with a more pronounced impact as the number of cycles increased. However, this adverse effect was mitigated by additive stabilization. The improvement in UCS in stabilized soils was directly linked to the additive content, curing duration, and temperature. Both additives demonstrated superior resistance to F-T cycles, with CKD outperforming kaolin. These findings provide guidelines for utilizing kaolin and CKD for earthwork applications in cold regions with economic and sustainability advantages.

Stabilisation of subsoil using colloidal silica beneath shallow foundation - a case study

Shallow foundations are commonly used to support various equipment in industrial projects. If the subsoil is too weak to withstand the equipment loads, the settlement or tilting of the foundations takes place. To avoid further distress to such foundations, weak soil beneath the damaged foundation is required to be strengthened. This paper presents a similar case study wherein the strengthening of subsoil was performed beneath the shallow foundations which experienced settlement and tilting beyond the permissible limits due to the presence of weak subsoil. The stabilisation of soil was performed using injection grouting with colloidal silica-based chemical grout to prevent further settlement and tilting of foundations. The particulars of the chemical stabilisation program, injection methodology, chemical consumption, field trials, and laboratory test results are explicated in this paper with the details of post rectification performance of the test foundation. The properly executed injection grouting using chemical components was observed to be an effective measure to stabilise the subsoil by enhancing its engineering properties to a certain extent. The key factors that can affect the performance of colloidal silica-based chemical and precautions to be considered during soil stabilisation are also discussed in this paper.

STUDIES OF THE EFFECT OF REINFORCEMENT WITH GEOSYNTHETIC MATERIALS ON THE STRENGTH OF SOILS UNDER CONDITIONS OF TRIAXIAL COMPRESSION AND SINGLE-PLANE SECTION

The study is a comprehensive analysis of the effect of geosynthetic materials on the strength characteristics of soils under triaxial compression and single plane shear conditions. The triaxial compression method is used to investigate the complex effects on soil specimens, which reflects real conditions and ensures the reliability of the results.The aim of the study is to evaluate the effectiveness of geosynthetic materials as a means of soil reinforcement. Particular attention is paid to analysing changes in the mechanical properties of soils reinforced with different types of geosynthetics compared to unreinforced samples. The study includes laboratory tests, during which the parameters of strength, deformability and stability of soils under different loads and variations of test conditions are evaluated.The results of the study provide important information for specialists in geotechnical design and construction. They help to evaluate the effectiveness of geosynthetic materials in strengthening soil structures under high loads and complex conditions.Additionally, the study includes an analysis of the effect of geogrid on the strength of weak soils, which allows to identify optimal strengthening options and compare their effectiveness.Thus, the study is a relevant contribution to the development of knowledge on the interaction between geosynthetic materials and soil structures, contributes to the optimisation of design and increases the durability of soil structures

Use of rise husks to improve the efficiency of MICP-based soil improvement technique

Biogrouting has been identified as the best alternative approach for the conventional cement and chemical grouts. Among the various types of biogrouting techniques, microbial induced carbonate precipitation (MICP) has been recently recognized as a promising pathway for producing biogrout material, hence densifying the weak soils. In MICP, calcium carbonate (CaCO3) biocement is produced through biochemical reactions induced by the urease enzyme. The efficiency and productivity of MICP can be further improved by introducing various additives, including fibers, organic polymers, powders, waste materials, etc. In this research, rice husk was sustainably incorporated into the MICP process, and (i) the effect of the rice husk content, (ii) the concentration of the cementation solution and (iii) the treatment time on the unconfined compressive strength (UCS) of the sandy soil were investigated at the laboratory-scale. Cementation solutions with higher concentrations exhibited a higher UCS values than solutions with lower concentrations. Interestingly, the content of rice husk had a marked influence on the UCS, and the optimum rice husk content was 15%. Compared to that of the control sample (0% rice husk), a threefold greater UCS was obtained for 15% of the rice husk content sample. The outcomes further suggested that longer treatment with lower concentration of cementation solution was the best combination for achieving effective cementation within the sand matrix. Rice husk acted as the template for CaCO3 crystals to nucleate while promoting the efficient formation of CaCO3, indicating that the rice husk is an excellent additive to improve the efficiency of the MICP biocementation in a sustainable way.

Effect of kaolin-nano-silica mixture on geomechanical properties enhancement of soils

Weak soil is a major obstacle facing the urban development of any site with other exceptional merits. The current study aims to investigate the utilization of nano-silica in enhancing the mechanical properties of weak kaolin soils. Design mixes using different percentages of nano-silica were investigated in the range between 0.25–1.20% from the dry weight of the kaolin soil. Various chemical, physical, and mechanical properties of each mixture have been investigated. The obtained results indicated that nano-silica addition to such kaolin soils decreased the plasticity index and the maximum dry density while increasing the plastic limit, the Liquid limit, and the optimum moisture content. In different curing days of the tested mixtures, maximum dry density was decreased, while the optimum moisture content increased. The optimum value of added nano-silica was less than 1% of the soil dry weight. In the modified kaolin soil with 0.9% nano-silica, the plastic limit was increased by 29%, while the liquid limit decreased by 13% in comparison with the untreated sample. After 28 days of the cured sample, the unconfined compressive strength readings increased by almost 14% compared to its reading on day one. Also, the California bearing ratio results recorded significant enhancement with nano-silica additives in comparison with the untreated kaolin soil. After 28 curing days, the sonicated samples recorded enhancement in the unconfined compressive strength readings by more than 5% and 9% with the additive N-Si (0.3% and 0.9%), respectively, when compared with the unsonicated samples.Graphical

Research on mechanical properties of weak expansive soil under conditions of different confining pressures and moisture contents based on triaxial test.

To explore the mechanical properties of weak expansive soil under different moisture contents and confining pressures. The triaxial remolded soil samples with different moisture contents (14%, 16%, 18%, and 20%) were prepared for the obtained Nanyang weak expansive soil. Four groups of 16 consolidated drained triaxial shear tests with a confining pressure of 50, 100, 200, and 300 kPa were carried out to study the effects of confining pressure and water content on the deviatoric stress and pore pressure of weak expansive soil with strain. The study showed that the shear strength of weak expansive soil samples gradually increased with the increase of the water content, but its increase nonlinearly decreased as the confining pressure increased. When the axial strain was small, the pore pressure significantly increased, and the pore pressure increased tended to be stable slowly and gradually as the axial strain gradually increased. Therefore, the research results could be used to avoid the diseases caused by the characteristics of weak expansive soil in engineering construction and provide theoretical references for improving engineering foundations in weak expansive soil areas.

Monitoring of Architectural Monuments

The article presents the main provisions that it is advisable to follow when organizing and conducting monitoring during the operation of cultural heritage sites. It is noted that the existing regulatory documents do not take into account the specifics of monitoring during operation, but are mainly aimed at protecting the monument from neighboring construction.Criteria are proposed to control the technical condition of historical buildings. Among them is the rate of development of long-term precipitation, which is considered as an indicator of the intensity of natural and man-made impacts on the building.Among them is the rate of development of long-term precipitation, which is considered as an indicator of the intensity of natural and man-made impacts on the building. It is noted that for stone structures, critical masonry stretching deformations serve as an effective criterion for the preservation of historical buildings, since in calculating the interaction of structures and foundations they are the primary criterion for calculating the second group of limiting states. In relation to it, the criterion of absolute precipitation and relative difference of precipitation is secondary. It is shown that over time, for buildings built on weak water-saturated clay soils, an increase in the unevenness of precipitation occurs. Special attention is paid to taking into account the accumulated uneven precipitation of buildings of historical development. The article presents the most characteristic types of deformations of buildings, among which in St. Petersburg the bend is most common, which is due to the regularity of building and rebuilding sections of urban neighborhoods.Monitoring is also considered as a reliable means of diagnosing the technical condition of the monument. The monitoring function is considered as a means of controlling the limitations of the monument’s operability, which continues to be operated in conditions of limited operational technical condition.

Theoretical Basis for Forecasting the Expansion of the Diameter of the Leading Well in Water-Saturated Soil with a Crushed Stone Bored Pile

In the process of construction and operation of buildings and structures located on weak water-saturated clay foundations, there is often a need to change their physical and mechanical properties. Currently, various methods of surface and deep compaction are used to improve the characteristics of weak soils. It is known that in the process of deep compaction, the soil is compressed under the action of radial stress on the wall of the leading well using an auger (in reverse motion), pile foundation technology, a rotor, etc. In this paper, the main attention will be paid to solving the axisymmetric problem of consolidation of a soil cylinder under the influence of radial pressure. The diameter of the well in this case increases by 2–3 times and is filled with working material – sand and gravel mixture. The purpose of this study is to carry out a theoretical analysis based on a different approach to solving the problem of the stress-strain state of weak soil during compaction of weak foundations and determining the required characteristics of the compacted composite massif transformed by a bored crushed stone pile. The results of the study convincingly prove that the technology under consideration, based on the expansion of the diameter of the leading borehole in water-saturated soil using crushed stone pile drains, is one of the most cost-effective and efficient solutions. It can compete with traditional compaction methods and the more expensive use of deep foundations.

Model Modification of the Soil–Water Characteristic Curve of Unsaturated Weak Expansive Soil

This study evaluates the impact of compaction on the soil–water characteristic curve of unsaturated remodeled weakly expansive soils by assessing changes in soil pore structure resulting from variations in compaction. The remodeled weakly expansive soil in the Xinjiang Hami area is taken as the research subject to investigate how compaction affects microscopic pore structure using mercury intrusion testing. Subsequently, mercury intrusion porosimetry is employed to examine pore structure and distribution patterns at different dry densities. Based on the capillary principle and experimental methods (filter paper method and pressure plate method test), modified soil–water characteristic curves are obtained by fitting them with a three-parameter model law. The results indicate that higher dry density leads to an increased air intake value and significantly reduces the total volume of large pores within samples. Both the Fredlund and Xing model and the three-parameter model effectively capture the influence of initial dry density on the development pattern of the soil–water characteristic curve.

Enhancing Weak Soil Strength in an Eco-friendly and Sustainable Manner: Reusing Waste from Indigenous Bamboo Dwellings in Arunachal Pradesh

Enhancing Weak Soil Strength in an Eco-friendly and Sustainable Manner: Reusing Waste from Indigenous Bamboo Dwellings in Arunachal Pradesh

Geotechnical and microstructural analysis of high-volume fly ash stabilized clayey soil and machine learning application

The weak soil stabilization using solid wastes is one of the most common solutions for improving geotechnical characteristics as well as for problematic waste dumping in landfills. The present experimental study aims to examine the effect of high-volume Class-F fly ash on the geotechnical and microstructural properties of clayey soil by adding them in ranges between 5 % and 50 %. The results show that as the amount of fly ash in clayey soil increases, properties like the specific gravity, plasticity index, permeability, optimum moisture content, maximum dry density and free swelling index improves. Moreover, these geotechnical properties were analyzed to develop machine learning models using three different algorithms, namely K-nearest neighbor regression, random forest, and support vector regression, for obtaining the optimum amount of fly ash contents in weak expansive soils. The predicted and experimental results found to be in close-relation for predicting the geotechnical behavior of modified clayey soil. Furthermore, the performance of the ML models degrades as the number of components reduces, with KNN regression consistently outperforming SVR and RF but suffering significantly with fewer components. The results of the testing set in the case of four components are MSE of 77, R² of 0.896, RMSE of 0.846, MAE of 0.327, and SEE of 0.858, indicating precise and consistent predictions. However, the prediction accuracy considering lesser components shows MSE as 262, R² as 0.648, MAE as 5.606, SEE as 16.707, and GPI as 1.056, confirming the elevated error rates. Overall, it has been concluded that combining comprehensive experimental work and machine learning techniques outperforms in enhancing geotechnical data processing, optimized waste contents in weak soils, improves sustainability in construction, saves resources, reduces the possibility of human mistakes, and increases reliability.

Assessment of the utilization of cement-treated geotextile as a reinforcement element for highway base layer under cyclic loading

This study conducted large-scale cyclic loading experiments on the base layer overlying a weak subgrade soil. Geotextile and cement-treated geotextile were utilized to reinforce the base material and to separate the interface of soils between the base layer and the subgrade. The results obtained from the repeated loading tests using geotextile and cement-treated geotextile were analyzed and evaluated in terms of some benchmark indicators such as total deformation, permanent deformation, elastic deformation, percentage of elastic deformation, traffic benefit ratio (TBR), elastic modulus (MR), improvement factor (If), and rut depth reduction ratio (RDR). Based on the experimental results, the use of cement-treated geotextile as a base layer reinforcement element or as an interfacial separation element demonstrated better performance compared to the use of geotextile. Utilization of a cement-treated geotextile as both reinforcement and separation element resulted in an RDR value of 49.26 % after 5000 cycles. Additionally, using a cement-treated geotextile for both reinforcement and separation increased the TBR value to 14.62 at 27 mm deformation, decreased the permanent deformation value from 53.67 mm to 27.23 mm, and approached approximately 2 improvement factor values, compared to using the geotextile solely for separation.