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Abstract In this work, intelligent numerical models for the prediction of debris flow susceptibility using slope stability failure factor of safety (FOS) machine learning predictions have been developed. These machine learning techniques were trained using novel metaheuristic methods. The application of these training mechanisms was necessitated by the need to enhance the robustness and performance of the three main machine learning methods. It was necessary to develop intelligent models for the prediction of the FOS of debris flow down a slope with measured geometry due to the sophisticated equipment required for regular field studies on slopes prone to debris flow and the associated high project budgets and contingencies. With the development of smart models, the design and monitoring of the behavior of the slopes can be achieved at a reduced cost and time. Furthermore, multiple performance evaluation indices were utilized to ensure the model’s accuracy was maintained. The adaptive neuro-fuzzy inference system, combined with the particle swarm optimization algorithm, outperformed other techniques. It achieved an FOS of debris flow down a slope performance of over 85%, consistently surpassing other methods.

Abstract It has been imperative to study and stabilize cohesive soils for use in the construction of pavement subgrade and compacted landfill liners considering their unconfined compressive strength (UCS). As long as natural cohesive soil falls below 200 kN/m2 in strength, there is a structural necessity to improve its mechanical property to be suitable for the intended structural purposes. Subgrades and landfills are important environmental geotechnics structures needing the attention of engineering services due to their role in protecting the environment from associated hazards. In this research project, a comparative study and suitability assessment of the best analysis has been conducted on the behavior of the unconfined compressive strength (UCS) of cohesive soil reconstituted with cement and lime and mechanically stabilized at optimal compaction using multiple ensemble-based machine learning classification and symbolic regression techniques. The ensemble-based ML classification techniques are the gradient boosting (GB), CN2, naïve bayes (NB), support vector machine (SVM), stochastic gradient descent (SGD), k-nearest neighbor (K-NN), decision tree (Tree) and random forest (RF) and the artificial neural network (ANN) and response surface methodology (RSM) to estimate the (UCS, MPa) of cohesive soil stabilized with cement and lime. The considered inputs were cement (C), lime (Li), liquid limit (LL), plasticity index (PI), optimum moisture content (OMC), and maximum dry density (MDD). A total of 190 mix entries were collected from experimental exercises and partitioned into 74–26% train-test dataset. At the end of the model exercises, it was found that both GB and K-NN models showed the same excellent accuracy of 95%, while CN2, SVM, and Tree models shared the same level of accuracy of about 90%. RF and SGD models showed fair accuracy level of about 65–80% and finally (NB) badly producing an unacceptable low accuracy of 13%. The ANN and the RSM also showed closely matched accuracy to the SVM and the Tree. Both of correlation matrix and sensitivity analysis indicated that UCS is greatly affected by MDD, then the consistency limits and cement content, and lime content comes in the third place while the impact of (OMC) is almost neglected. This outcome can be applied in the field to obtain optimal compacted for a lime reconstituted soil considering the almost negligible impact of compactive moisture.

Abstract The current study investigated the primary and secondary compressibility characteristics of organic clay with two biopolymers, Chitosan (D ch ) and Casein (D ca ) at dosages of 0.5%, 1%, 2%, and 4%. The primary compression index (C c ) values were reduced by 18% and 59% at dosage (D ch and D ca ) of 4% at a consolidation pressure of 800 kPa. The secondary compression indices of chitosan and casein-treated soils fell below the normal range specified for organic soils and lay in the range of 0.01–0.017. The biopolymers also accelerated the consolidation process at all dosages (D ch ) and 2% D ca . The hydraulic conductivity increased for all dosages of chitosan whereas it declined for all dosages of casein compared to untreated soil. The reliability analysis was conducted for biopolymer-treated soils and presented a rational approach toward the selection of a suitable liner. Chitosan failed to achieve a target reliability index of 3 whereas casein-amended samples attained values equal to and greater than 3 at all dosages and consolidation pressures at COV of K max = 20%. At all dosages, the casein-treated soils exhibited reliability index values greater than 3 up to COV of K max = 40% indicating the higher stability of casein mixes as a liner material.

Enzyme-induced calcite precipitation (EICP) emerges as a highly effective and well-established technique within bio-cementation approaches, offering notable advantages over traditional methods. Conversely, lime, known for its accessibility, cost-effectiveness, and efficacy, serves as a valuable material in enhancing the engineering properties of problematic soils. This study explores the application of EICP and lime treatments separately on two distinct soils (low-plastic and high-plastic soil) exhibiting different mineralogical and plasticity characteristics to assess their impact on strength and swell characteristics. Various combinations of treatments, including jack bean (JICP), soya bean (SICP), and bio-enhancer (BICP), were employed for EICP treatment. Bio-enhancer, rich in natural urea and urease enzyme, was particularly remarkable due to its compatibility with urea supplementation. Similarly, jack bean and soya bean exhibited high efficacy in natural urease enzyme content. The study has revealed that the unconfined compression strength (UCS) of red soil increased significantly by six times at the end of 21 days of the curing period with JICP treatment, while lime treatment was more effective for the black soil. Specifically, the UCS of black cotton soil increased by 11 and 17 times when treated with Enzyme-Induced Calcite Precipitation (EICP) and lime, respectively. Moreover, EICP with J2 solution (jack bean solution with 1M urea and 4 g/L non-fat milk powder) reduced swell pressure by 60% and 67.5% in low-plastic and high-plastic soil, respectively. Lime treatment, on the other hand, led to a swell pressure reduction of 47% and 70% in low-plastic and high-plastic soil, respectively. As a result, EICP proved efficient in mitigating swell pressure for red soil, whereas lime treatment performed exceptionally well for black soil, highlighting the soil-specific effectiveness of each method. Furthermore, a life cycle assessment revealed substantial carbon footprint emission savings with EICP treatment strategy. In brief, this paper contributes to understanding the phenomena and significance of these two treatment techniques on distinct mineralogical soils.

Kuttanad region in Kerala, India, is a place that predominantly consists of soft soil formations with low shear strength and low water resistance rendering them problematic for construction purposes. Pavements constructed on such soft deposits have been subjected to structural rutting and the high erodibility of the in-situ soil necessitates the need to use suitable ground improvement techniques. The present environmental scenario demands the implementation of sustainable techniques for ground rejuvenation and effective stabilizers for enhancing engineering properties. This study investigates the amelioration of Kuttanad soft soil using chitosan as a soil amendment to improve its durability and erodibility characteristics. The untreated and chitosan-treated samples were exposed to 5 h of wetting cycle followed by 43 h of drying cycles until their failure. The unconfined compressive strength (UCS) of samples prepared with different dosages (0.5, 2, 4%) and cured for 14, 28, 60, and 90 days was evaluated at the onset and after each drying cycle to measure their durability index. Kuttanad soil was amended with 2% and cured for 90 days withstood five cycles with a UCS of more than 1,000 kPa. The drip erosion tests were used to check the erodibility performance for the aforementioned different dosages and curing periods. The 2% and 4% chitosan amended samples resisted the entire test duration of 10 min indicating the highest water erosion resistance. The findings of the current study evaluated through durability and erosion tests reinforced the effectiveness of chitosan as an effective biopolymer for soft soils subjected to constant water attack and can be easily implemented in places with such vulnerability. A typical earthen canal lining amended with chitosan reduced the carbon emissions by 8.74 and 7.44 times compared to conventional amendments like lime and cement in Carbon Footprint Analysis.

Traditional soil stabilization techniques, such as cement and lime, are known for their menacing effect on the environment through heavy carbon emissions. Sustainable soil stabilization methods are grabbing attention, and the utilization of biopolymers is surely one among them. Recent studies proved the efficiency of biopolymers in enhancing the geotechnical properties to meet the requirements of the construction industry. The suitability of biopolymer application in different soils is still unexplored, and the carbon footprint analysis (CFA) of biopolymers is crucial in promoting the biopolymers as a promising sustainable soil stabilization method. This study attempts to investigate the out-turn of cross-linked biopolymer on soils exhibiting different plasticity characteristics (Medium & High compressibility) and to determine the Embodied carbon factor (ECF) for the selected biopolymers. Guar (G) and Xanthan (X) biopolymers were cross-linked at different proportions to enhance the geotechnical properties of soils. Atterberg’s limits, Compaction characteristics, and Unconfined Compressive Strength were chosen as performance indicators, and their values were analyzed at different combinations of biopolymers before and after cross-linking. The test results have shown that Atterberg’s limits of the soils increased with the addition of biopolymers, and it is attributed to the formation of hydrogels in the soil matrix. Compaction test results reveal that the Optimum Moisture Content (OMC) of biopolymer-modified soil increased, and Maximum Dry Density (MDD) reduced due to the resistance offered by hydrogel against compaction effort. Soils amended with biopolymers and cured for 14, 28, and 60 days have shown an appreciable improvement in Unconfined Compressive Strength (UCS) results. Microlevel analysis was carried out using SEM (Scanning Electron Microscopy) and FTIR (Fourier-transform infrared spectroscopy) to formulate the mechanism responsible for the alteration in targeted performance indicators due to the cross-linking of biopolymers in the soil. The embodied energy in the production of both Guar and Xanthan biopolymers was calculated, and the obtained ECF values were 0.087 and 1.67, respectively.

Kuttanad is a region that lies in the southwest part of Kerala, India, and possesses soft soil, which imposes constraints on many civil engineering applications owing to low shear strength and high compressibility. Chemical stabilizers such as cement and lime have been extensively utilized in the past to address compressibility issues. However, future civilizations will be extremely dependent on the development of sustainable materials and practices such as the use of bio-enzymes, calcite precipitation methods, and biological materials as a result of escalating environmental concerns due to carbon emissions of conventional stabilizers. One such alternative is the utilization of biopolymers. The current study investigates the effect of chitosan (biopolymer extracted from shrimp shells) in improving the consolidation and shrinkage characteristics of these soft soils. The dosages adopted are 0.5%, 1%, 2%, and 4%. One-dimensional fixed ring consolidation tests indicate that consolidation characteristics are improved upon the addition of chitosan up to an optimum dosage of 2%. The coefficient of consolidation increases up to seven times that of untreated soil, indicating the acceleration of the consolidation process by incorporating chitosan. The shrinkage potential is reduced by 11% after amendment with 4% chitosan and all the treated samples exhibit zero signs of curling. Based on the findings from consolidation and shrinkage data, carbon emission assessments are carried out for a typical landfill liner amended with an optimum dosage of chitosan. In comparison to conventional stabilizers like cement and lime, the results indicate that chitosan minimized carbon emissions by 7.325 times and 8.754 times, respectively.

This paper assesses the significance of stabilizing clay soil with calcium lignosulphonate (CLS) and granite sand (GS). Unconfined compressive strength (qc) and hydraulic conductivity (K) are taken as performance indicators and the effect of varying dosages of GS (30%, 40%, and 50%) and CLS (0.5%, 1%, 1.5%, and 2%) at different curing periods on qc and K are examined. The best fit regression equations have been proposed to relate qc and K of untreated clay soil and stabilized clay using GS and CLS. The proposed nonlinear regression equations provide details of experimental data and aid in estimating qc and K very efficiently and reliably for targeted geotechnical applications from a sustainable perspective.

The increase in infrastructure requirement drives people to use all types of soils, including poor soils. These poor soils, which are weak at construction, must be improved using different techniques. The extinction of natural resources and the increase in cost of available materials require us to think of alternate resources. The usage of industry by-products and related methods for improving the properties of different soils has been studied for several years. Granite dust is an industrial by-product originating from the primary crushing of aggregates. The production of huge quantities of granite dust in the industry causes severe problems from the handling to the disposal stage. Accordingly, in the civil engineering field, the massive utilization of granite dust has been proposed for various applications to resolve these issues. In this context, the present review provides precise and valuable content on granite dust characterization, its effect as a stabilizer on the behavior of different soils, and its interaction mechanisms. The efficacy of the granite dust in replacing sand in concrete is explored followed by its ability to improve the geotechnical characteristics of clays of varying plasticity are explored. The review is even extended to study the effect of binary stabilization on clays with granite dust in the presence of calcium-based binders. The practical limitations encountered and its efficiency over other stabilizers are also assessed. This review is further extended to analyze the effect of the granite dust dosage for various field applications.

The development of alternatives to soil stabilization through mechanical and chemical stabilization has paved the way for the development of biostabilization methods. Since its development, researchers have used different bacteria species for soil treatment. Soil treatment through bioremediation techniques has been used to understand its effect on strength parameters and contaminant remediation. Using a living organism for binding the soil grains to make the soil mass dense and durable is the basic idea of soil biotreatment. Bacteria and enzymes are commonly utilized in biostabilization, which is a common method to encourage ureolysis, leading to calcite precipitation in the soil mass. Microbial-induced calcite precipitation (MICP) and enzyme-induced calcite precipitation (EICP) techniques are emerging trends in soil stabilization. Unlike conventional methods, these techniques are environmentally friendly and sustainable. This review determines the challenges, applicability, advantages, and disadvantages of MICP and EICP in soil treatment and their role in the improvement of the geotechnical and geoenvironmental properties of soil. It further elaborates on their probable mechanism in improving the soil properties in the natural and lab environments. Moreover, it looks into the effectiveness of biostabilization as a remediation of soil contamination. This review intends to present a hands-on adoptable treatment method for in situ implementation depending on specific site conditions.

Soil treatment methods to cope with ever-growing demands of construction industry and environmental aspects are always explored for their suitability in different in-situ conditions. Of late, enzyme induced calcite precipitation (EICP) is gaining importance as a reliable technique to improve soil properties and for contaminant remediation scenarios. In the present work, swelling and permeability characteristics of two native Indian cohesive soils (Black and Red) are explored. Experiments on the sorption and desorption of multiple heavy metals (Cd, Ni and Pb) onto these soils were conducted to understand the sorptive response of the heavy metals. To improve the heavy metal retention capacity and enhance swelling and permeability characteristics, the selected soils were treated with different enzyme solutions. The results revealed that EICP technique could immobilize the heavy metals in selected soils to a significant level and reduce the swelling and permeability. This technique is contaminant selective and performance varies with the nature and type of heavy metal used. Citric acid (C6H8O7) and ethylene diamine tetra-acetic acid (EDTA) were used as extractants in the present study to study the desorption response of heavy metals for different EICP conditions. The results indicate that calcium carbonate (CaCO3) precipitate deposited in the voids of soil has the innate potential in reducing the permeability of soil up to 47-fold and swelling pressure by 4-fold at the end of 21 days of curing period. Reduction in permeability and swell, following EICP treatment can be maintained with one time rinsing of the treated soil in water to avoid dissolution of precipitated CaCO3. Outcomes of this study have revealed that EICP technique can be adopted on selected native soils to reduce swelling and permeability characteristics followed by enhanced contaminant remediation enabling their potential as excellent landfill liner materials.

Las soluciones de forma cerrada simples para la capacidad de carga no drenada de zapatas escalonadas en suelos isotrópicos cohesivos se derivan al emplear el enfoque cinemático del análisis de límites. Se intentan utilizar tanto el mecanismo traslacional de fallas como el mecanismo modificado tipo Hill, con ángulos de incidencia variables. Se ha determinado, de forma analítica, la mejor cota superior para cada mecanismo, lo cual nos lleva a una expresión analítica para el factor de capacidad de carga. También se ha evaluado la influencia del grado de anisotropía del suelo en el valor correspondiente para el factor de capacidad de carga. Para un amplio rango de grados de anisotropía, la mejora en los valores predichos de la cota superior no garantiza el uso del mecanismo modificado del tipo Hill. En vez de eso, el mecanismo convencional de falla del tipo Hill, con un ángulo de incidencia fijo de n/4, nos entrega una expresión simple y concisa para el factor de capacidad de carga que es analíticamente equivalente al factor convencional de capacidad de carga de Prandtl-Reissner, para el caso de suelos isotrópicos multiplicado por el promedio de la suma del grado de anisotropía más la unidad.

In order to explore the possibility of using low-lime fly ashes, the physical and chemical properties which have a direct bearing on their geotechnical and geoenvironmental behaviors have been investigated. In this paper, two types of low-lime fly ashes, originating from India, have been used. A brief account of various methods adopted in characterizing their physical, chemical, and geotechnical properties is presented. The relative importance of each of these properties in enhancing the bulk applicability of fly ashes has been brought out.

Modern innovations increasingly prioritize eco-friendliness, aiming to pave the way for a sustainable future. The field of civil engineering is no exception to this approach, and, in fact, it is associated with almost every sustainable development goal framed by the United Nations. Therefore, the sector has a pivotal role in achieving these goals. One such innovation is exploring the possibilities of using nature-friendly materials in different applications. Biopolymers are substances that are produced either by the chemical synthesis of natural materials or by the biosynthesizing activities of microorganisms. Microbial-derived biopolymers are known for their non-toxic and nature-friendly characteristics. However, their applications are mostly restricted to the field of biotechnology and not fully explored in civil engineering. This article reviews various microbial-derived biopolymers, focusing on the types available on the market, their source and properties, and more importantly, their wide range of applications in the civil engineering field. Additionally, the article explores the prospects for future research and the potential for the practical implementation of these techniques in the pursuit of a sustainable future. [ABSTRACT FROM AUTHOR]

The current study evaluated the potential of crustacean polysaccharide and protein-based biopolymers, namely, chitosan and casein, in ameliorating a low organic soil. The inclusion of these biopolymers will ensure the reusability and recyclability of waste materials derived from the marine industry and dairy industry, respectively. The unconfined compressive strength and consolidated undrained shear parameters were investigated at varying dosages of chitosan and casein (0.5%, 1%, 2%, and 4%) and curing periods (up to 90 days). The compressive strength increased with an increase in the curing period and dosage and led to maximum values of 4.39 and 3.13 MPa for chitosan- and casein-treated soils, respectively, for 4% dosage and 90 days of curing. The effective cohesion (c′) and friction angle (ϕ′) improved after including chitosan and casein. The scanning electron microscopy images revealed that the filler characteristics of chitosan led to strength improvement up to 60 days and developed bond strength via fiber bridging after 60 days of curing at higher dosages. In contrast, the casein–soil mix revealed a higher fibrous structure after a curing period of 28 days, which resulted in strength improvement. This contributed to the highest effective friction angle of 21.57° for the 2% and 60-day-cured casein–soil mix. Casein outperformed chitosan in imparting higher effective shear parameters at 1% and 2% dosages. Fourier transform infrared analysis validated the absence of any new compounds within the soil structure. The research findings on chitosan and casein from the current study recommend the application of these materials for addressing the issues of unstable slopes and pavement subgrade. Practical Applications: The ground improvement industry must shift from environmentally harmful materials to sustainable and nontoxic materials to reduce carbon footprint. Biopolymers are innovative materials derived from various bacteria, plants, and other animals and can impart the required properties for the soils tested (Fatehi et al. 2021). Chitosan and casein are two biopolymers that satisfy the sustainability requirement by being environmentally safe products of waste materials (Chang et al. 2018; Kannan and Sujatha 2023). Applying casein and chitosan has imparted significant improvement in strength to the studied soil. The compressive strength achieved for the fine-grained soils treated with chitosan and casein lies in the range of 0.75–4.39 MPa. Thus, the strength obtained for the treated soils affirms the suitability of these biopolymers in pavement subgrade. The significant improvement in the effective cohesion (c′: 72–179 kPa) and friction angle (ϕ′: 10.57°–21.57°) of amended soils renders the chitosan- and casein-amended samples as excellent shallow foundation materials. Additionally, based on the higher undrained shear strength (125–400 kPa) obtained from consolidated undrained tests, the biopolymers can be recommended for unstable slopes. [ABSTRACT FROM AUTHOR]

Acacia gum (AG), a polysaccharide biopolymer, has been adopted to improve the strength of three cohesive soils by subjecting them to diverse environmental aging conditions. Being a polysaccharide and a potentially sustainable construction material, the AG yielded flexible film-like threads after 48 h upon hydration, and its pH value of 4.9 varied marginally with the aging of the stabilized soils. The soil samples for the geotechnical evaluation were subjected to wet mixing and were tested under their Optimum Moisture Content (OMC), as determined by the light compaction method. The addition of AG modified the consistency indices of the soils due to the presence of hydroxyl groups in AG, which also led to a rise in OMC and reduction in Maximum Dry Unit weight (MDU). The Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) were determined under thermal curing at 333 K as well as on the same day of sample preparation. The least performing condition of the soil's CBR was evaluated under submerged conditions after allowing the AG-stabilized specimens to air-cure for a period of 1 week. The UCS specimens tested after 7 days were subjected to the initial 7 days of thermal curing at 333 K. A dosage of 1.5% of AG yielded the UCS of 2530 kN/m2 and CBR of 98.3%, respectively, for the low compressible clay (LCC) after subjecting the sample to 333 K temperature for 1 week. The viscosity of the AG was found to be 214.7 cP at 2% dosage. Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and average particle size determination revealed the filling of pores by AG gel solution, adsorption, and hydrogen bonding, which led to improvements in macroproperties. [ABSTRACT FROM AUTHOR]

The 3D geological model serves as a cornerstone, establishing the essential foundation and prerequisite for numerical simulations, analytical assessments, and evaluative procedures that are integral to the disciplines of geotechnical and geological engineering. The task of integrating vast quantities of multi-source, heterogeneous modeling data, the absence of stratigraphic division standards to meet varying precision requirements, and addressing the application demands of 3D geological models beyond the geological domain, pose significant challenges to the endeavor of 3D geological modeling. This is especially true for the construction of large-scale, high-precision 3D geological models at the urban level. Our research introduces a methodology for 3D geological modelling, with a particular focus on the dual-weighted interpolation technique for the integration of land-sea data and the establishment of a three-tiered coding system for bedrock layers. Focusing on Qingdao, a city characterized by its bedrock geology and situated along the eastern coastal region of China, our proposed method has successfully catalyzed the creation of models across four distinct scales: a comprehensive city-wide model covering an area of 11,282 square kilometers, five general models, two demonstration models, and five refined models. Further application cases have demonstrated that these models are not only capable of meeting the requirements of geological and geotechnical engineering across various scenarios, but also exhibit excellent interoperability and significant application potential when integrated with Building Information Modeling (BIM), Geographic Information Systems (GIS), and Internet of Things (IoT) technologies. The outcomes of this study are significant for the theoretical development and technological advancement of 3D geological modeling, and can also bring inspiration and reference to the work of 3D geological modeling in other areas. [ABSTRACT FROM AUTHOR]