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For engineering waste soils with a large proportion of sand resources, an effective technique for sand extraction from waste soils still needs to be developed. This study investigates the degree and efficiency of sand resource extraction based on a hydro-cyclone separation principle via a series of experiments. The soil samples in the experiments contained a sand content ranging from 12.56% to 52.75% and a water content ranging from 155.96% to 597.04%. The results show that the water contents of test samples should reach a certain threshold to perform hydro-cyclone separation, and appropriately increasing the water content will have a positive effect on the separation degree, which can achieve a maximum value of 73.26%. However, the separation degree reaches an upper limit value when the water content is greater than approximately 400%, which is revealed by the characteristics of soil viscosity varying with water content, and high-water content for the separation efficiency is not beneficial. To balance the separation degree and efficiency, optimum sample water contents for sand extraction and an evaluation approach for different sand content samples are proposed. Through application of the proposed approach, an average sand extraction efficiency of 135.88 g/s can be achieved. [ABSTRACT FROM AUTHOR]

Three quarters of the world's significant urban centers are located in coastal regions where clay minerals are prevalent. The microstructures and physico-mechanical properties of clay sediments are highly susceptible to alterations in pore water chemistry. The pore water chemistry in soil changes easily due to groundwater pollution, seawater erosion, degradation, etc. However, there are several inconsistencies in the literature on the change of physical and mechanical properties of clay soils caused by the change of pore water chemical properties, i.e., disparate experimental results were reported for the same soil property, or varying explanations were proposed for the identical experimental results. Currently, the research in this field mainly focuses on the macroscopic behavioral modifications while lacking the explanations of microscopic mechanism. Therefore, this paper presents a comprehensive review of researches conducted over the past four decades on the impact of pore water chemistry (including salt type, salinity, ion valence, pH) on soil properties such as the microstructure, settlement, Atterberg limits, shear strength, conductivity, unsaturated soil mechanics properties and thermal properties. The fundamental mechanisms underlying the varied experimental observations on clay sediments affected by salt and pH are systematically explored, and deficiencies in this field are identified. The observed dispersion in the literatures is attributed to the spatial variation and heterogeneity of soil compositions, different test methods, and insufficiency of the fundamental microscopic mechanisms of the observed soil behaviors, etc. Therefore, it is necessary to further explore the essential mechanisms of the test results in the future to establish a unified conclusion. [ABSTRACT FROM AUTHOR]

This study presents an experimental inquiry into the effects of two independent variables on the draft force of a mouldboard plough/planter: planting depth (0 - 5 and 6 - 10 cm) and plowing depth (6 - 10 and 11 - 15 cm). A dual-purpose mouldboard plough/planter was developed to expedite the cultivation of maize by speeding up the ploughing and planting processes. Based on planting and ploughing depths, the draft force of the implement was evaluated. Field experimental procedures were used to conduct the trials, and parametric testing was used to analyze the data. The final formula for calculating the draft force depends on a number of soils engineering characteristics, including soil bulk density and type, tool specifications, such as cutting width and implement weight, and operational factors, such as ploughing depth and moisture content. The study's findings show that ploughing depth has a greater impact on a mouldboard plough/planter's draft force; the maximum draft force of 1.5 kN was recorded at planting depths of 6 to 10 cm and ploughing depths of 11 to 15 cm. The data indicates that the draft force of the cum planter is significantly (p~0.05) affected by the depth of ploughing. The ploughing depth and planting depth on draft force were shown to have a strong association in the linear regression model, with a coefficient of determination (R² = 0.75) for draft force indicating high correlations among the components. Ploughing depths are always responsible for explaining the difference in draft force. The results suggest that any change in the plowing depths provides a considerable forecast of the implement's draft force, since the plowing depth was the largest predictor of the draft force. The best results from the mouldboard plough/planter are achieved when planting and ploughing are done at depths of 0-5 cm and 5-10 cm, respectively. [ABSTRACT FROM AUTHOR]

The project aims to provide a comprehensive analysis of the various instruments and tools used in civil engineering laboratories. This study focuses on understanding the operational principles, applications, and significance of lab equipment in conducting essential experiments and tests. By examining a range of devices, including those used for soil mechanics, concrete testing, structural analysis, and fluid mechanics, the project seeks to highlight the critical role these instruments play in ensuring accurate and reliable data collection. The findings of this study will serve as a valuable resource for students, researchers, and professionals in the field, enhancing their knowledge of lab equipment functionality and its application in civil engineering projects. Additionally, the project will explore advancements in lab technology and suggest potential improvements to current practices, aiming to contribute to more efficient and effective experimental processes in civil engineering education and research. To improve the application of thought in laboratory exercises and to develop many useful skills in undergraduate Civil Engineering students, a laboratory course consisting of dual-step laboratory exercises and a report of recommendations/innovation from the student, was introduced for the Fluid Mechanics laboratory. The first step of the dual-step exercise consisted of a standard exercise (concise version) followed by rigorous analysis of the data; the second step consisted of either designing and carrying out a new experiment/addressing a different question with the same/slightly modified experimental setup or formulating and testing hypotheses for unexpected trends in the data. Students worked in groups under the direction of an elected group leader. The need, details, outcomes and experiences of the dual-step laboratory exercise/recommendations report are discussed and samples of some student exercises are presented. The student and laboratory staff responses are also presented. [ABSTRACT FROM AUTHOR]

In order to achieve the resource utilization of high moisture content shield soil in underground engineering and explore the feasibility of using geopolymer materials to solidify shield soil, this paper adopts slag-base geopolymer to solidify shield soil. By studying the influences of alkali activator modulus, mineral ratio, alkali activator dosage and temperature on unconfined compressive strength and engineering performance of different types of shield-cured soil, the design of cured soil mix proportion was determined. The influence of geopolymer content on water stability of cured soil was studied. Microscopic analysis of shield-cured soil using SEM to reveal the solidification mechanism. The results show that under the proposed water solid ratio in the test, the two kinds of fluid shield-cured soil with different soil properties have good mechanical and engineering properties. The aggregate of slag base produces amorphous gel, which enhances the cementation and compactness between soil particles. The unconfined compressive strength of shield-cured soil with 22% dry soil mass as cementing agent can reach 5.38 MPa in 28 d under standard curing, 8.08 MPa under 40 °C curing, and the water stability coefficient can reach 0.98. [ABSTRACT FROM AUTHOR]

Torpedo anchor is one offshore anchoring which has been gaining popularity recently for floating structures. The torpedo anchor was expected to resist the environmental loading transferred from the floating platform. Thus, the understanding of the holding capacity of torpedo anchors under vertical and horizontal combined loading is the key concern of its design. Nonetheless, most of the previous studies are deterministic without considering the common existing random heterogeneity nature of marine soil. In light of this situation, this paper reports a large deformation random finite element study under the framework of the Monte Carlo method. VH failure envelopes of torpedo anchors in heterogeneous soil were obtained by conducting simulations of continuous extraction procedures along different directions. Furthermore, the strain-softening behaviour of the soil was also accounted for considering the server deformation of the soil. The results show that both the size and shape of the VH failure envelope are significantly affected by random heterogeneity of soil. A series of VH failure envelopes of various probabilities of failure was thus given to guide the design. Results in this paper may be constructive for the safety design of the torpedo anchor. [ABSTRACT FROM AUTHOR]

The alkali-activated composites technique is a promising method for the in situ preparation of cavity filling/grouting materials from engineering waste soil. To investigate the feasibility of engineering waste soil utilization by the alkali activation process, the macroscopic and microscopic properties of the fly ash/slag-based alkali-activated composites, after solidification/stabilization (S/S) with sandy clay excavated at Baishitang Station of Shenzhen Metro, were studied. The unconfined compressive strength (UCS) test was conducted to evaluate the S/S effect of alkali-activated composites. The results show that the optimum quality ratio of slag and fly ash correspond to 7:3, the modulus of alkaline activator to 1.3, and the alkalinity of alkaline activator to 10%. The alkali-activated composite's strength under these parameters can reach 45.25 MPa at 3 days, 49.85 MPa at 7 days, and 62.33 MPa at 28 days. A maximum 3-day UCS of 21.71 MPa, 75% of the 28-day UCS, was achieved by an engineering waste soil and alkali-activated composites mass ratio of 5:5, slaked lime content of 4.5%, and a water-to-solid ratio of 0.26, and it can also meet the required fluidity and setting time for construction well. Fluidity is primarily affected by the soil-to-binder ratio, which decreases as the ratio decreases, while the water-to-solid ratio increases fluidity. Slaked lime has minimal impact on fluidity. The setting time is mainly influenced by the soil-to-binder ratio, followed by slaked lime content and water-to-solid ratio, with setting time shortening as the soil-to-binder ratio and slaked lime content increase, and lengthening as the water-to-solid ratio increases. Through Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS) tests, microscopic analysis showed that loose granular units are firmly cemented by alkali-activated composites. Based on the results of on-site grouting tests in karst caves, the alkali-activated grout materials reached a strength of 5.2 MPa 28 days after filling, which is 162.5% of the strength of cement grouting material, satisfying most of the requirements for cavity filling in Shenzhen. [ABSTRACT FROM AUTHOR]

This paper presents a novel application of machine learning models to clarify the intricate behaviors of expansive soils, focusing on the impact of sand content, saturation level, and dry density. Departing from conventional methods, this research utilizes a data-centric approach, employing a suite of sophisticated machine learning models to predict soil properties with remarkable precision. The inclusion of a 30% sand mixture is identified as a critical threshold for optimizing soil strength and stiffness, a finding that underscores the transformative potential of sand amendment in soil engineering. In a significant advancement, the study benchmarks the predictive power of several models including extreme gradient boosting (XGBoost), gradient boosting regression (GBR), random forest regression (RFR), decision tree regression (DTR), support vector regression (SVR), symbolic regression (SR), and artificial neural networks (ANNs and proposed ANN-GMDH). Symbolic regression equations have been developed to predict the elasticity modulus and unconfined compressive strength of the investigated expansive soil. Despite the complex behaviors of expansive soil, the trained models allow for optimally predicting the values of unconfined compressive parameters. As a result, this paper provides for the first time a reliable and simply applicable approach for estimating the unconfined compressive parameters of expansive soils. The proposed ANN-GMDH model emerges as the pre-eminent model, demonstrating exceptional accuracy with the best metrics. These results not only highlight the ANN's superior performance but also mark this study as a groundbreaking endeavor in the application of machine learning to soil behavior prediction, setting a new benchmark in the field. [ABSTRACT FROM AUTHOR]

The ongoing refinement of bearing capacity equations remains pivotal in soil mechanics and foundation engineering, reflecting its critical role in ensuring design efficacy and construction safety. This study conducts a thorough evaluation of classical bearing capacity methods—Terzaghi, Meyerhof, Vesic, and Hansen—and methods included in various design standards, such as EN1997:2004, prEN1997:2023, GEO, AASHTO, FHWA, and API. It explores the performance and applicability of these approaches, identifying areas for potential improvement. In response to identified challenges, the paper proposes the integration of a unified depth factor. This new factor is designed to be applicable across all N-terms, providing a more versatile and accurate tool for bearing capacity predictions. Unlike the original depth factors unique to each method, which may not fully address complex soil and footing conditions, the unified depth factor is developed to enhance prediction accuracy for a wide range of conditions, including both flexible and rigid footings under varying flow rules (ψ = 0 and ψ = φ). This depth factor corrects for modeling errors, emphasizing the importance of pairing the correct set of N-factors with their corresponding depth factor. By offering a singular depth factor that aligns with the outcomes of finite element analysis, this paper not only simplifies the computational process but also enhances the accuracy of bearing capacity predictions across a diverse range of soil conditions and footing types. The comparative analysis, based on finite element analysis, validates the proposed method's effectiveness, showcasing its potential to significantly refine foundation design practices by comparing it with both traditional and newly developed depth factors. [ABSTRACT FROM AUTHOR]

Amino acids aid in the growth and development of plants. Soil microbes outcompete plants for amino acids because they are great source of carbon and nitrogen for microbes. To overcome this problem, new agricultural practices are required. Due to minimal integration and ecological environmental preservation, polyethylene glycol is used as a soil-stabilizer to study its stabilization effect on soil. Six soil samples (0%-5% Polyethylene Glycol) were prepared to study the effect of polymer on soil-amino acid interaction. Five non-polar amino acids, viz., glycine, alanine, 2-aminobutyric acid, leucine and methionine, on soil were studied with soil thin layer chromatography. Scanning electron microscopy and X-ray diffraction studies successfully marked the presence of Polyethylene Glycol in the soil. Mobility of amino acid is positively correlated with the concentration of Polyethylene Glycol in the soil. The effect of polymer on soil-amino acid interaction could be applied as a new reference for polymer-improved soil engineering. [ABSTRACT FROM AUTHOR]

Excavation in foundation pits can result in serious issues for nearby tunnel structures like deformation, differential settlement, and seepage damage, which profoundly impact project timelines and potentially endanger life and property safety. Therefore, it is imperative to investigate these impacts before and after construction and to facilitate timely adjustments of construction measures and reinforcement where possible. In this study, a foundation pit construction project near a rail transit line is employed as a case to comprehensive study the impact of on-site deep foundation pit excavation on adjacent rail transit structures by numerical simulation. A three-dimensional finite-element model of the foundation pit based on site geological characteristics and construction procedures is established to study the excavation and maintenance processes. Through analysis of key parameters including soil deformation, displacement, shear force, and bending moment of the tunnel structures, the designed protective structure is found to have effectively mitigated soil deformation, ensuring the stability of the foundation pit. As excavation progresses, lateral soil deformation and vertical uplift gradually increase but remain within specified control values. During various excavation stages, the maximum displacement of the tunnel structure gradually increases, with the increase rates of maximum settlement being 29.09%, 20.51%, and 6.45%, respectively. This indicates a gradual enhancement of the stability of the tunnel structure. Additionally, excavation of the foundation pit has a significant impact on the bending moment distribution of the tunnel structure but does not affect the axial force and shear force of the tunnel structure. The findings of this study offer crucial scientific insights for evaluating the safety and stability of construction near tunnel structures. [ABSTRACT FROM AUTHOR]

Creep is recognised to be an important physical property of soils, exerting a profound influence on the stability of structures. In order to gain a comprehensive understanding of the advancements and focal points in soil creep research, the relevant literature was accessed from the Web of Science Core Collection database, totalling 3907 papers (as of 25 March 2024). Statistical analyses on publication volume, keyword co-occurrence, and clustering were conducted using the visualization software VOSviewer (1.6.20). The current hotspots in soil creep research were identified, and a systematic review was undertaken on the influencing factors of soil creep and the corrective methods of creep models. The research findings indicate that the number of papers on creep research exhibits a trend of increase followed by a decrease over time. Developed countries, such as those in Europe and America, initiated research in this field earlier than developing countries like China. Currently, the research focus is primarily centred on creep models. Significant differences exist in the creep deformation of soils under different influencing factors, with soil microstructure, moisture content, and stress path being important factors affecting soil creep deformation. Creep deformation in unsaturated soils primarily considers the influence of matric suction, while indoor creep tests are mainly conducted based on vertical loading, which differs significantly from the stress conditions experienced by soils in engineering construction sites. Currently, adjustments to soil parameters are mainly made through single-factor adjustments involving stress, time, damage, and matric suction to determine creep models under specific influencing factors, and then to modify the models accordingly. However, research on the creep deformation mechanism and creep models under multiple factors is relatively limited. Future research directions are expected to focus on the microscopic scale of creep mechanisms and multi-factor creep models. [ABSTRACT FROM AUTHOR]

In this paper, the numerical study of the ultimate bearing capacity (UBC) of two closely spaced strip footings on granular soil is investigated using the finite element method (FEM) and upper bound limit analysis (UBLA). Although the UBC of two adjacent footings has previously been studied in other experimental and numerical research, in all the previously reported studies, the footings were not allowed to rotate and move horizontally freely. Due to the deformation of the soil medium, two closely spaced footings are subjected to horizontal movements and tilting, even under central vertical loads. When the two adjacent footings are not permitted to rotate and move in the horizontal directions, the unwanted bending moment and horizontal force act on the footings. Indeed, the UBC of two closely spaced rough footings is evaluated under incorrect constraints in earlier research. In the present research, the UBC of two adjacent rough footings is evaluated with and without these incorrect constraints. The key finding of this study is that constraining the horizontal and rotational movement of the foundation artificially increases the UBC, which does not reflect field conditions. When foundations are permitted to rotate and move horizontally, there is no increase in UBC; however, there is an increased risk of differential settlement and structural instability. [ABSTRACT FROM AUTHOR]

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Education 4.0 can play a significant role in the future of geotechnical engineering education. It can provide personalized and equitable learning experiences and be used to develop skills for the fourth industrial revolution in geotechnical engineering. In this paper, we explore the application of Augmented Reality (AR) and Virtual Reality (VR) models, as part of Education 4.0, to enhance the presentation and communication of soil mechanics concepts. A detailed step-by-step process for creating 3D representations of geotechnical concepts, including texturing, UV mapping, animation, and export and publishing techniques, is introduced. For this purpose, two powerful 3D modeling and animation software programs, Autodesk Maya and Blender, are employed to develop geotechnical avatars in a soil mechanics laboratory. In Autodesk Maya, a detailed representation of the soil phase diagram is presented, while Blender is utilized to create a Consolidated Undrained (CU) triaxial laboratory experiment. The geotechnical testing avatars are then uploaded to Sketchfab, a popular publishing website that supports AR/VR formats. We also explore the potential for establishing a virtual laboratory for geotechnical engineering, highlighting the transformative possibilities it offers in terms of practical learning experiences and educational accessibility. [ABSTRACT FROM AUTHOR]

This document is a closure to a previous paper titled "Foundation Settlement and Tilt of Millennium Tower in San Francisco, California." The authors respond to comments and questions raised by discussers regarding the design, construction, and analysis of the tower's foundation movements. They emphasize that their goal was to objectively document the data and provide interpretations of the soil deformation mechanisms that caused the settlements. They encourage further investigation and analysis of the case history to advance foundation engineering practices in dense urban environments. [Extracted from the article]

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This paper discusses the influence of different sign conventions for strains and stresses, i.e. the solid mechanics sign convention and the soil mechanics sign convention, on the form of governing partial differential equations (the static equilibrium equations and the continuity equation) used to describe the wave-induced cyclic response of a poro-elastic seabed due to propagation of a sinusoidal surface water-wave. Some selected analytical solutions, obtained by different authors and published in specialist literature in the form of complex functions describing the wave-induced pore-fluid pressure, effective normal stress and shear stress oscillations in the seabed, have been analysed and compared with each other mainly with respect to different sign conventions for stains and stresses and also with regard to different orientations of the positive vertical axis of the two-dimensional coordinate system and different directions of surface water-wave propagation. The performed analyses of the analytical solutions has indicated many inaccuracies, or even evident errors and exemplary mistakes of wrong-signed values of basic wave-induced response parameters (the shear stress in particular), thereby disqualifying these solutions and their final equations from practical engineering applications. Most of the mistakes found in the literature must be linked to authors’ lack of understanding and consistency in an uniform application of a certain sign convention for strains and stresses in the soil matrix at both stages of mathematical formulation of the governing problem and correct interpretation of equations of the final analytical solution. The present paper, based mostly on a thorough literature review, ought to draw attention and arouse interest among coastal scientists and engineers in proper identification and use of the existing analytical solutions to the wave-induced cyclic seabed response – solutions which differ very often in the applied sign convention for stresses in the soil matrix.

This study introduces microbiologically induced calcium phosphate precipitation (MICPP) as a novel and environmentally sustainable method of soil stabilization. Using Limosilactobacillus sp., especially NBRC 14511 and fish bone solution (FBS) extracted from Tuna fish bones, the study was aimed at testing the feasibility of calcium phosphate compounds (CPCs) deposition and sand stabilization. Dynamic changes in pH and calcium ion (Ca2+) concentration during the precipitation experiments affected the precipitation and sequential conversion of dicalcium phosphate dihydrate (DCPD) to hydroxyapatite (HAp), which was confirmed by XRD and SEM analysis. Sand solidification experiments demonstrated improvements in unconfined compressive strength (UCS), especially at higher Urea/Ca2+ ratios. The UCS values obtained were 10.35 MPa at a ratio of 2.0, 3.34 MPa at a ratio of 1.0, and 0.43 MPa at a ratio of 0.5, highlighting the advantages of MICPP over traditional methods. Microstructural analysis further clarified the mineral composition, demonstrating the potential of MICPP in environmentally friendly soil engineering. The study highlights the promise of MICPP for sustainable soil stabilization, offering improved mechanical properties and reducing environmental impact, paving the way for novel geotechnical practices. [ABSTRACT FROM AUTHOR]

The construction of acoustic emission criterion system is crucial for monitoring and providing early warning of geological hazards. In the current soil acoustic emission monitoring methods, the signal generated by soil deformation and failure is weak and experiences high attenuation, resulting in a low level of the monitored signal. One approach to enhance the quality of monitoring data is by utilizing the active waveguide model. However, the current research on the active waveguide model system is not extensive. To address these issues, a set of active waveguide system was designed to improve the data quality of acoustic emission monitoring and early warning. The deformation and failure process of loess monitored by acoustic emission was divided into stages, and the precursor information of acoustic emission for geological disasters in loess areas was comprehensively deconstructed. The data quality advantage of the active waveguide model was verified through comparative experiments of with the passive waveguide model. This study investigates the AE signal characteristics of the active waveguide model. It explores various aspects such as the AE waveform parameter characteristics, the discrimination method for failure mode based on RA–AF value, the AE r-value characteristics, the AE b-value characteristics, and the frequency-amplitude characteristics. The study reveals the evolution law of AE signals in the active waveguide model, including early warning signs and failure morphological characteristics. Furthermore, it constructs a warning criterion for the active waveguide system. The development of this criterion system is of great importance in guiding the monitoring and early warning of geological disasters in loess areas. [ABSTRACT FROM AUTHOR]

This investigation examines the effect of clamshell ash (CSA) and lime additives on the physico-mechanical characteristics of kaolinite clay soil stabilized at the optimum silica fume content. Laboratory tests were performed to assess plasticity, shrink-swell characteristics, compaction characteristics, unconfined compressive strength (UCS), shear strength characteristics, mineralogical and morphological microstructure characteristics of stabilized soil specimens. The kaolinite clay soil was stabilized at its optimum silica fume content (6%) to produce the highest strength and was altered with three non-identical proportions of clamshell ash and lime (3%-9%). Cylindrical soil specimens, 76 mm in height and 38 mm in diameter, were moulded and treated for curing periods of 1, 7, 14, and 30 days to examine the strength of the altered soil. The findings revealed that, adding clamshell ash and lime significantly alters the plasticity, shrink-swell, maximum dry unit weights, and optimum moisture contents of the silica fume-stabilized soil. In terms of strength, the beneficial effects of CSA and lime additives were found to be more significant with more extended curing periods. Incremental increases in curing periods resulted in further enhancements in UCS, cohesion, and internal friction angle, indicating continued strength development over time. Microstructural analysis using field emission scanning electron microscopy and X-ray diffraction provided insights into the interparticle bonding mechanisms and microstructural changes induced by the addition of CSA and lime. The emergence of cementitious phases and pozzolanic responses between soil particles and stabilizers contributed to the densification and strengthening of the stabilized soil matrix. The findings of this study provide valuable insights into the potential of clamshell ash and lime additives to enhance the engineering properties of kaolinite clay soil stabilized with silica fume. These results have implications for sustainable soil stabilization practices, offering a promising approach to improve the performance of soils for various engineering applications, including construction and geotechnical projects. [ABSTRACT FROM AUTHOR]

AbstractThe present work aims to propose a model for calculating unconfined compressive strength (UCS) of soil stabilized by geopolymer based on gene expression programming (GEP). The new model is compared with earlier models developed from artificial neural networks (ANN), multivariable regression analysis (MVR), multi-gene genetic programming (MGGP), and support vector machines (SVM) models. The results indicate that the GEP model is superior to MVR and MGGP models and quite comparable to ANN and SVM models. The study demonstrates the robustness of the GEP model through parametric analysis. Additionally, this model is simpler and easier to use in practice. [ABSTRACT FROM AUTHOR]

To enhance comprehension of the improved arch cover construction method for underground metro stations and provide guidance for future construction techniques and programs, the paper examines the indoor improved arch cover method of construction in the underground concealed excavation station of Tianhe Road Station of Guangzhou Metro Line 10, China. It includes a similar model test of the key technology and an analysis of the evolution law of the surrounding rock stress, the law of the ground settlement, and the law of the arch top deformation after the tunnel excavation. The study found that increased over-support can decrease arch settlement, with the maximum settlement occurring near the arch. Ground settlement typically occurs in the same areas as arch settlement, but arch settlement may occur earlier. The excavation of the arch cover has little impact on the overlying soil pressure, and the supporting structure is more effective in controlling soil deformation. The upper part of the arch cap experiences mainly extrusion stress, with the maximum stress occurring near the middle of the arch. The stresses in the arch's base decrease significantly during the excavation of the side drifts but show an increasing trend during the excavation of the lower rock mass. The presence of the central column significantly affects both the settlement of the arch and the ground, as it bears most of the compressive stress of the arch. This stress decreases initially and then increases. The amplitude of deformation is more pronounced when the dismantled central column is closer to the middle of the arch. [ABSTRACT FROM AUTHOR]

In Japan, recently there has been an increase in the failure of dry masonry retaining walls located in an urban residential area due to strong earthquakes. However, currently there are no established optimal seismic reinforcement methods for such dry masonry retaining walls due to issues related to workability and construction cost. This paper presents a novel reinforcement method wherein the tilting reinforcement bars were installed from top of the retaining wall whose individual blocks were integrated. A detailed investigation and discussion on the mechanical behavior of a dry masonry retaining wall is made by comparing the results among different experimental cases which had different seismic reinforcement treatment with the help of tilting table experiments conducted in a geotechnical centrifuge. The results highlighted that the proposed method, the application of tilting reinforcement bars together with the integration of individual wall blocks, led to the best seismic resilient performance of the retaining wall with the least measured soil deformations and soil strains at the backfill. Among all the tested cases, the proposed method resulted in the least mobilization of axial force and bending moment at the top of reinforcement bars which may result in the overall reduction of the construction cost (i.e., by reducing the number of reinforcement bars) aiming toward a performance‐based design. Lastly, an analytical evaluation of the factor of safety (FOS) against collapse as per the Mononobe‐Okabe theory was made which was found to be in excellent agreement with the centrifuge experiments revealing the proposed method to perform best among all the cases. [ABSTRACT FROM AUTHOR]

The simple shear test has been an important tool in practical geotechnical engineering and the study of soil behaviour. The attractiveness of the simple shear test is founded in its relative ease of specimen preparation, similarity to at-rest conditions during consolidation and rotation of principal stresses during shear. Despite this test's attractive qualities, there are significant deficiencies in the interpretation of standard test results: horizontal normal stresses are not known and excess pore pressures are often interpreted from assumptions about constant-volume tests without saturation. To address this problem, a set of monotonic tests were performed on a sand, during which horizontal normal stresses were measured in the central portion of specimens. Based on the measurements, the full state of stress was defined, stress paths were drawn and directions of the principal stresses were determined. Outcomes showed that the conventional approach of estimating excess pore pressures as the change in vertical pressure to maintain constant volume in response to shear is problematic, and friction angles interpreted from conventionally measured shear and vertical stresses may be grossly underestimated in some cases. [ABSTRACT FROM AUTHOR]

Desiccation cracking can significantly affect the hydro-mechanical behaviour of soil in various engineering applications. Characterising the evolution of desiccation-induced shrinkage strain in soils is a key step in understanding the cracking mechanism. This study presents a novel framework for monitoring and early detecting soil cracking by utilising the distributed fibre optical sensing (DFOS) technique based on optical frequency domain reflectometry (OFDR). DFOS-OFDR was integrated into a set of experimental testing to simultaneously monitor water content, crack pattern and strain state. OFDR with 1 με strain measurement accuracy was employed to monitor the initiation and propagation of cracks. The results reveal a strong correlation between the spatiotemporal evolution of soil strain and crack, confirming the efficacy and reliability of the proposed framework. During the drying process, the compressive strain induced by soil shrinkage increases first and starts to decrease when cracking is initiated. Further, DFOS-OFDR demonstrated promising results to predict the position of cracks. Compared to traditional strain monitoring methods with discrete measurements, DFOS-OFDR offers a non-destructive, accurate yet efficient, high-resolution and continuous technique for monitoring and early detection of soil desiccation cracking. [ABSTRACT FROM AUTHOR]

Expansive soils are generally characterised by their volume change when subjected to variation in water content. This may result in significant damage to supported and nearby structures. In this study, the swelling properties of bentonite material as an expansive soil are first determined. The expansive soil is then improved using two different approaches, namely, micro-metakaolin (Mm) and ferric chloride (FeCl3) solution. The optimum percentages for both additives are determined using laboratory experiments, which are 25 and 1% for the Mm and the ferric chloride solution, respectively. The free swell index of the bentonite after being treated with Mm and ferric chloride solution at the optimum percentages is found to decrease by about 54 and 62%, respectively. Meanwhile, the swelling pressure for the expansive soil decreased by 33 and 43% when mixed with the same optimum values of Mm and ferric chloride solution, respectively. On the basis of the results obtained in this study, the addition of ferric chloride solution achieved better results compared with Mm. This improvement technique may be used to enhance the properties of expansive soils that support different construction engineering projects. [ABSTRACT FROM AUTHOR]

Viscous behaviour is a significant characteristic of soil, and to accurately capture this behaviour, a piecewise-linear model called ACLC has been developed specifically for modelling one-dimensional large-strain consolidation of soft clay. ACLC takes into account both the long-term deformation and anisotropy of the soil. Furthermore, it incorporates various factors such as soil heterogeneity, self-weight, time-dependent loading, vertical flows, and seepage force. In ACLC, the settlement of the soil layer is a result of both the net outflow of fluid from the soil element and the development of soil creep. To describe the creep behaviour of the soil, ACLC employs two yield surfaces: the Current State Surface (CSS) and the Normal Consolidation Surface (NCS). The creep rates are calculated based on the associated flow rule. To ensure the accuracy of ACLC, it is validated using the enhanced CS2 model, oedometer tests conducted on Xiaoshan soft clay, and observed data from the Murro test embankment. Finally, the influence of ACLC parameters on the consolidation behaviour of clay is thoroughly investigated. This analysis helps to understand the role of these parameters and their impact on the overall consolidation process. [ABSTRACT FROM AUTHOR]

Underground excavation is usually accompanied by complex soil-structure interaction problems in practical engineering. This paper develops a novel multi-scale approach for investigating the soil arching effect through trapdoor tests. This approach adopts the finite element method (FEM) and smoothed particle hydrodynamics (SPH) method to handle the particle-rigid body interaction in the trapdoor tests, incorporating a micromechanical 3D-H model to derive the nonlinear material response required by the SPH method. The variation of the earth pressure on the trapdoor in simulations exhibits good agreement with those of the experiments. Extensive parametric analyzes are performed to assess the effects of soil height and inter-particle friction angle on the evolution of load transfer and soil deformation. Three deformation patterns are observed under different buried conditions, including the trapezoid, the triangle, and the equal settlement pattern. Results indicate that the planes of equal settlement develop progressively with the trapdoor movement and then enter the range of experimentally observed values. Additionally, three failure mechanisms are identified that correspond to the three deformation patterns. Due to the advantages of the micromechanical model, mesoscale behavior is captured. The anisotropy of stress distribution in the plastic region is found during the arching process. [ABSTRACT FROM AUTHOR]

The paper presents a rigorous analytical approach to predicting the load–settlement behavior of axially loaded piles embedded in sandy soils, adopting the advanced SANISAND model. The problem of the soil state around the pile during loading is formulated as a system of first-order ordinary differential equations, which can be solved as an initial value problem. The derived load–settlement (t–z) curve is then implemented into the load-transfer method to determine the pile's load–settlement behavior in sands and the deformation mechanism of the soil around the pile during axial loading. To verify the proposed analytical approach, a FEM simulation is performed with a user-defined subroutine, demonstrating its capacity to capture the dilatancy behavior of sands as the pile moves downwards. Additionally, a parametric analysis is conducted to assess the influence of the initial void ratio on the stress–strain relationship of the sandy soil around the pile during the loading process. The proposed analytical approach is also compared with a well-established finite-element model and a centrifuge test. The results indicate that the present approach can well predict the elastoplastic load–settlement response of the pile and reflect important phenomena observed from pile tests. [ABSTRACT FROM AUTHOR]

In northern regions, the long-term serviceability of infrastructure founded on frozen ground is adversely affected by climate warming. Rates of change in temperature, which are not identical spatially and temporally, can remarkably dictate the magnitude and evolution of permafrost degradation. Investigating such impacts requires a non-isothermal rate-dependent geomechanical constitutive model for ice-contained geomaterials. In this paper, a critical-state thermo-elasto-viscoplastic (TEVP) constitutive model is developed for modeling time- and temperature-dependent behavior of frozen soils using the concepts of thermo-elasticity and thermo-viscoplasticity. Solid phase stress (defined as the excess of total stress over fluid pressure), in addition to the cryogenic suction, are considered as the two independent stress state variables to establish the model. The proposed model is able to satisfactorily capture the rate-dependent behavior of frozen soils observed in the experimental tests reported in the literature. [ABSTRACT FROM AUTHOR]

Soil arching is significantly influenced by relative density, while its mechanisms have barely been analyzed. A series of DEM numerical simulations of the classical trapdoor test were carried out to investigate the multi-scale mechanisms of arching development and degradation in granular materials with different relative density. For analysis, the granular assembly was divided into three zones according to the particle vertical displacement normalized by the trapdoor displacement δ. The results show that before the maximum arching state (corresponding to the minimum arching ratio), contact forces between particles in a specific zone (where the vertical displacement of particles is larger than 0.1δ but less than 0.9δ) increase rapidly and robust arched force chains with large particle contact forces are generated. The variation in contact forces and force chains becomes more obvious as the sample porosity decreases. As a result, soil arching generated in a denser particle assembly is stronger, and the minimum value of the arching ratio is increased with the sample porosity. After the maximum arching state, the force chains in this zone are degenerated gradually, leading to a decrease in particle contact forces in microscale and an increase in the arching ratio in macroscale. The recovery of the arching ratio after the minimum value is also more significant in simulations with a larger relative density, as the degeneration of contact force chains is more obvious in denser samples. These results indicate the importance of contact force chain stabilities in specific zones for improving soil arching in engineering practice. [ABSTRACT FROM AUTHOR]

Aims: Termites function as "soil engineers" in tropical agroforestry ecosystems. However, of their role in phosphorus (P) cycling little is known. We aimed to investigate the impact of termite activity on soil aggregate stability and P fractions at the aggregate level in a tropical rubber plantation. Methods: Fungus-growing termite mounds (active and abandoned) involving both above- and belowground locations were studied in a 24-year-old rubber stand. The mass percentage and stability of aggregates, P fractions contents and other major chemical properties of soil aggregates were measured. Aggregate-associated P preservation capacity was also calculated. Results: More aggregates < 1 mm in size were concentrated in active aboveground mounds than active belowground chambers, thus resulting in weaker stability and erosion resistance, whereas the opposite trend occurred in abandoned mounds. The concentrations of labile P (in > 2 mm aggregate size), moderately labile P (0.25–1 mm), and non-labile P (0.053–1 mm) in active aboveground mounds were significantly higher than other types. The changes in specific P forms enriched TPi in aggregates > 2 mm and TPo in 0.053–1 mm size of active aboveground mounds relative to others, implying the importance of Po storage in microaggregates induced by termite activity involved in long-term P transformation. Furthermore, middle-sized (0.25–2 mm) aggregates stored more P and represented the highest P storing capacity, especially for active belowground chambers. Conclusions: These results suggest that in the presence of termite activity, P cycling is greatly enhanced in aboveground mounds despite the poor aggregate stability, whereas P forms are stable after mound abandonment, except for a higher H2O-Pi concentration aboveground. Our study provides an important reason why mound soils can be considered as fertility amendments for agroforestry practices in P-deficient tropical soils. [ABSTRACT FROM AUTHOR]

Here, we theoretically and computationally study the frequency dependence of phase speed and attenuation for marine sediments from the perspective of granular mechanics. We leverage recent theoretical insights from the granular physics community as well as discrete-element method simulations, where the granular material is treated as a packing of discrete objects that interact via pairwise forces. These pairwise forces include both repulsive contact forces as well as dissipative terms, which may include losses from the fluid as well as losses from inelasticity at grain–grain contacts. We show that the structure of disordered granular packings leads to anomalous scaling laws for frequency-dependent phase speed and attenuation that do not follow from a continuum treatment. Our results demonstrate that granular packing structure, which is not explicitly considered in existing models, may play a crucial role in a complete theory of sediment acoustics. While this simple approach does not explicitly treat sound propagation or inertial effects in the interstitial fluid, it provides a starting point for future models that include these and other more complex features. [ABSTRACT FROM AUTHOR]

This paper re-evaluates the Edenville earth dam that failed in 2020 after a rapid rise in reservoir level caused by prolonged significant rainfall. The dam instability and possibility of static liquefaction–induced flow failure are assessed in the framework of critical state soil mechanics (CSSM). Both undrained loading and drained unloading stress paths are considered for flow liquefaction assessment. Using documented triaxial compression tests, the Norsand constitutive model is calibrated for finite-element numerical models. This study supplements the analyses conducted by an independent forensic team (IFT) in charge of failure investigation. The advances achieved by tailings dam practitioners are leveraged here to study flow liquefaction as recommended by the IFT. Multiple ways are employed to generate reasonable initial field stresses. Simulation of dam construction coupled with steady-state seepage analysis creates an appropriate starting condition for further flow liquefaction assessment. The numerical outputs confirm the result of the IFT's limit equilibrium analyses for an undrained boundary condition. Stress analyses with a drained boundary condition show that a major stress change with a constant-shear-drained (CSD) stress path develops below the dam crest due to a rising reservoir level. The results of our models with a CSD stress path and drained-to-undrained transition better explain the evolution of the Edenville dam failure. The current study provides a practical approach to earth dam design and evaluation. [ABSTRACT FROM AUTHOR]

Laboratory experiments on clayey soils under dynamic triaxial compression were conducted to establish a nonlinear relationship between the dynamic modulus of soil deformation and the frequency of impact. The most significant increase in the dynamic modulus of soil deformation is observed under an increase in frequency from 5 to 10 Hz. In comparison with fluvioglacial soils, the dynamic deformation modulus in glacial loams grows slower under an increase in frequency. This confirms the dependence of the obtained relations on the genesis of soils. The research results were used to develop vibration protection systems for high-precision equipment in high-tech industries. [ABSTRACT FROM AUTHOR]

The proposed generalized electric spring (G-ES) topology effectively reduces the redundancy caused by the parallel structure of multiple electric springs in a microgrid system. A modeling method for the G-ES is urgently needed to accurately determine the G-ES parameters and to evaluate its transient operation characteristics. The correspondence between Hamilton's principle in mechanics and electricity is introduced, and the feasibility of Hamilton's principle under the smart load topology is verified. The modeling method of the G-ES under Hamilton's principle is discussed, followed by the application of repetitive control strategies on the G-ES. The filter parameters are designed using the normalization method and a simplified parameter design using repetitive controllers was applied. This article introduces the impedance analysis method into the generalized electric spring to analyze its stability under weak network conditions. This work also derives the stability judgment criteria for generalized electric springs. Finally, the feasibility of modeling the G-ES based on the Hamilton's principle was verified using MATLAB and a DSP hardware system. In addition, the consistency between the G-ES and a single intelligent load was verified under the Hamilton's modeling principle. The G-ES stability and dynamic performance under this modeling method meet industry requirements. [ABSTRACT FROM AUTHOR]

The critical-state theory (CST) serves as the foundation of modern soil mechanics and has gained widespread acceptance for explaining the behavior of granular materials. The classical CST does not address the fabric anisotropy of granular materials, leading to questions about the uniqueness of the critical state when considering such anisotropy. Recently, the development of anisotropic critical-state theory (ACST) highlights that fabric anisotropy of granular materials should reach a unique normalized value at the critical state. However, ACST does not specify which fabric tensor is used to characterize the microstructure of soils. In this study, we present a comprehensive characterization of various soil fabrics, including contact-based fabric tensor, void-based fabric tensor, and particle–void fabric, respectively. We employ three-dimensional clumped particles to approximate different shapes of Toyoura sand particles, which makes the characterization of soil fabric more accurate. Discrete element method simulations of conventional triaxial compression tests under both drained and undrained conditions are conducted on soil samples with different initial confining pressures and void ratios. The evolution of various fabrics toward the critical state is compared and discussed. Moreover, we establish relationships among contact-based fabric, void-based fabric, particle–void fabric, mean effective stress, and void ratio at the critical state. The study provides new insights into understanding the relations between the critical state and the microstructure of granular soils. [ABSTRACT FROM AUTHOR]

This article centers its investigation on high-moisture-content solidified lightweight soil in the Binhai New Area of Tianjin. It examines the shear mechanical properties under conditions of significant deformation, supplying pertinent reference values and theoretical foundations for engineering practice. The results demonstrate that the curve for solidified lightweight soil under substantial shear conditions manifests a strain-softening tendency. As normal stress escalates, both peak and residual strength increase while the degree of softening diminishes. The peak strength envelope at varying shear rates forms an upward zigzagging line, with the bending degree of the line augmenting as the rate increases. As the shear rate elevates, the cohesive strength within the peak strength parameters intensifies, the internal friction angle remains constant, and the residual strength parameters remain unaffected by the shear rate. This furnishes theoretical guidance for the applied engineering of blown-cured lightweight soil. [ABSTRACT FROM AUTHOR]

The construction of deep foundation pits that are adjacent to an operating subway tunnel can cause significant disturbance to the surrounding soil and tunnel structure. Assessing the stability of the soil in the security area of the tunnel is key to controlling the displacement of the tunnel structure. Assuming that the soil behind the wall is in the elastic stage of small deformation, the unloading stress distribution law of the soil on the excavation surface of the side wall is inversely calculated using the horizontal displacement curve of the retaining structure. Based on the analytical solutions for the horizontal displacement and surface settlement of the soil behind the wall proposed in this paper, the spatial distribution characteristics of the deformation transfer of the soil in the security area are obtained. Considering the interaction between the soil in the security area and the tunnel structure, by simplifying the soil in the security area to a Pasternak foundation model, the tunnel displacement that is caused by deformation transfer can be obtained. The correctness of the theoretical model is verified by comparing it with the measured data for the soil displacement behind the wall and the tunnel structure in project cases of foundation pit excavation. [ABSTRACT FROM AUTHOR]

A simplified mechanical model for investigating pile–pile horizontal vibration is developed by combining the Pasternak model and the Timoshenko beam theory, with the consideration of the influence of axial load at the head of the source pile. The expressions for horizontal displacements and internal forces of the source pile are obtained with respect to the differential transform method and pile–soil boundary continuity conditions. Additionally, considering that the vibration of the source pile affects the dynamic displacements of the receiver pile, the dynamic equilibrium equation of the receiver pile is established. Then, a closed-formed solution for the response of the receiver pile is derived from the obtained expressions. Further, the pile–pile horizontal dynamic interaction factor is derived based on its definition and validated by comparison with existing related analytical solutions. Finally, the effects of the shear deformations of soil and pile, pile slenderness ratio, and axial load on the pile–pile horizontal dynamic interaction factors are examined. It is indicated that a smaller pile-to-soil modulus ratio of the near-surface layer results in a more significant effect of shear deformation of the soil. In particular, when L/d is small (i.e., L/d < 5) or the pile cross section is annular, the effect of shear deformation of the pile is not ignorable. [ABSTRACT FROM AUTHOR]

Atterberg limits are important index parameters used to classify soils for various engineering applications. Engineering properties of soils are predicted through simple correlations with index properties and thereby the engineering behavior of soils are qualitatively assessed. There are two popular methods of determining liquid limit, and plastic limit is commonly determined adopting rolling thread methods. To avoid operator related variations in determining plastic limit by conventional method, some researchers have explored using cone method as an alternative. However, there is no consensus about the depth of penetration to reckon the end of plastic state. Though various other test methods have been developed to determine plastic limit (like roll plate device), cone penetration with its limitation of determining plastic limit, is the only method to determine both liquid and plastic limit of soils. Since laboratory vane shear test is a simple and reliable method of determining undrained strength of fine-grained soils, the authors have explored to determine both liquid and plastic limits through correlations developed between undrained strength and water content over a range of consistencies between liquid and plastic states. This would eliminate determining liquid and plastic limit separately without sacrificing the reliability of results. [ABSTRACT FROM AUTHOR]

River and lake dredging projects inevitably produce significant quantities of wastewater and sediment. This accumulation results in dredged soil with high moisture content, characterized by low strength, rendering it unsustainable for use. To facilitate environmentally friendly utilization of wastewater and sediment, solidifying agents and basalt fibers are introduced to solidify the wastewater within the dredged sediment. This process transforms the wastewater, sediment, solidifying agents, and basalt fibers into a novel, strengthened material. This transformation allows for their application as stabilized soil for engineering endeavors. Indoor experiments and scanning electron microscope analyses were performed to examine the deformation characteristics of fiber-stabilized soil and analyze its micro-mechanisms. Research findings suggest that as the curing age increases, the curing agent's reaction becomes more comprehensive. Fibers have the potential to ameliorate soil damage. The proposed binary-medium model's applicability and accuracy were validated through the analysis of triaxial test results employing the reinforcement principle. These findings establish a theoretical foundation for the resourceful utilization of wastewater and sediment. [ABSTRACT FROM AUTHOR]