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AbstractSimilar to pile group, the process of designing an anchor group requires the determination of an efficiency factor that describes the overlapping effects of neighboring anchors. This research article introduces an efficiency factor denoted as ξ, which represents the ratio of the ultimate uplift pressure of a single anchor within a group to the ultimate uplift pressure of an isolated anchor. The primary approach employed involves advanced 3D finite element limit analysis with an adaptive meshing technique, which can be utilized to examine the uplift stability problem of 3D anchor groups. Numerical findings are compared with those obtained from previous research, incorporating both experimental and analytical results. This would ensure that our results are validated and provide valuable information into the performance of anchor groups. In addition to these findings, we introduce a MARS machine learning model, which has been trained using a dataset of 875 data points. This model is designed to establish an empirical equation that can be practically used for design purposes. To further enhance our understanding, we present the relative importance index (RII). This index allows us to identify which factors have the most significant impact on the behavior of anchor groups. In conclusion, the results presented in this article are of practical significance for the geotechnical engineering community. [ABSTRACT FROM AUTHOR]

This study presents a finite difference model for analyzing ground stability and settlement of twin circular culverts in undrained clay. The model is verified through simulations of soil movement and relaxation around a tunnel-boring machine's shield. Stability numbers and ground settlement are evaluated across various culvert geometries and soil ratios and compared to rigorous solutions and previous models. The settlement data obtained is used to determine inflection point parameters for practical culvert design, considering dimensionless ratios. The findings highlight the importance of precise design methodologies that consider soil properties and geometry. The finite difference model proves to be a valuable tool in culvert design, providing accurate analysis of stability and settlement characteristics. The presented design figures and regression equations serve as practical tools for engineers in designing stable twin circular culverts in undrained clay. The study emphasizes the need to carefully consider soil properties and geometry for successful culvert design. In conclusion, the finite difference model offers insights into ground stability and settlement of twin circular culverts. The presented design figures and regression equations support engineers in making informed design decisions, ensuring the stability and long-term performance of culverts in undrained clay conditions. [ABSTRACT FROM AUTHOR]

The paper presents axisymmetric FEA solutions for the bearing capacity of conical footings embedded in anisotropic and inhomogeneous clays using NGI-ADP model. The bearing capacity factor of conical footings is defined to be a function of three dimensionless parameters: (i) the cone apex angle, (ii) the increasing strength gradient ratio, and (iii) the anisotropic shear strength ratio. A series of parametric studies is carried out to portray the influence of all input parameters on the bearing capacity factors. Based on the FEA results of 216 investigated cases, the artificial neural network (ANN) is adopted to capture the relationship between input parameters and output bearing capacity factors. The complex relationship between input parameters and output bearing capacity is studied through the use of design charts and failure patterns. A new accurate equation with a high value of R2 is proposed and the sensitivity of each input parameter on the output results is scored by adopting the results from the ANN model. This study has provided some practical insights into the performance of conical footings embedded in anisotropic and inhomogeneous clays. [ABSTRACT FROM AUTHOR]

Geotechnical engineers are faced with great uncertainty with regard to the stability design of soil structures such as retaining walls, foundations, and slope stability. Instead of using a deterministic approach by replacing the design parameter with a single mean number, Monte Carlo simulations could be used to provide better decisions by considering all possible outcomes under parametric uncertainty. This paper studies probabilistic failures of classical passive trapdoors in shallow depths with spatially random soils. The effects of soil strength variability are investigated for various spatial correlation lengths and trapdoor depths using the latest adaptive finite-element upper-bound limit analysis with second-order cone programming. In addition, probabilistic stability results are compared with those published in renowned literature, and a comprehensive probability of design failure (PF) charts is developed for a practical range of deterministic factors of safety. The extensive results reported in this paper would be of great interest to engineering practitioners because better decisions can be made in the design process and design confidence improved. [ABSTRACT FROM AUTHOR]

An automatic process for estimating ground stability and settlement of circular tunnels is developed for practitioners in this paper using finite difference method FLAC code. The numerical model aims to simulate the movement and relaxation of the soil around the shield and lining annulus that occurs due to the overcutting and grouting of the tunnel void by a tunnel boring machine. To achieve this, the model uses a pressure relaxation technique that progressively reduces the tunnel support pressure from the initial at rest condition until a point of failure is detected. At this stage, the stability number is calculated, and settlement data are exported for analysis. This is conducted for a range of geometry and soil ratios which cover most practical cases for cohesive soils. These stability numbers are then compared to rigorous upper and lower bound solutions. Using the settlement data, a trough width parameter ix is also determined for each case using regression of the commonly used Gaussian equation. The results of this study are quite positive, with the stability results from this study remaining within 5% of the upper and lower bound solutions; settlement results also compare well with previous experimental and observational results. The proposed automatic process can be used effectively and efficiently in most practical design projects. [ABSTRACT FROM AUTHOR]

A box culvert is a tunnel under roadways or railways that transports open drains or streams. The geotechnical design of such a structure involves accurate evaluation of the earth pressure on the structure. This short technical note pertains to findings of stability factors in tables and charts as an aid to civil engineers in designing unlined square box culverts. A conventional equation that is similar to Terzaghi's bearing capacity factors (Nc, Ns, and Nγ) is adopted to examine the use of stability factors (Fc, Fs, and Fγ) to estimate the critical support pressures at collapse. Rigorous upper-bound and lower-bound solutions of the stability factors are computed using the adaptive finite-element limit analysis. To validate the present bound solutions, numerical results are compared with those published previously using other methods. Design tables, figures, and examples are presented for practical uses. [ABSTRACT FROM AUTHOR]

Highlights: •A state of art approach to evaluate the elliptical tunnel stability of Hoek–Brown rock mass.•Rigorous upper bound and lower bound solutions of elliptical tunnel stability are derived using advanced finite element limit analysis.•Comprehensive design tables and equations are proposed for stability evaluation. [ABSTRACT FROM AUTHOR]

Sinkhole occurrences due to underground water mains operations have piqued people's curiosity. Most research works were in relation to geophysical practices to discover the subsurface cavity. Very few works can be found in relation to the investigation of soil stability due to underground cavity shapes. The actual shape of an underground cavity and its transformation is difficult to predict, though the sinkhole failures are mostly circular in shape on the ground surface. This study explores the three-dimensional collapse stability of three distinct idealized cavity geometries, namely the circular, semi-spherical, and spherical cavities. For an active failure, dimensionless parameters are used to investigate the combined impacts of soil cover, surcharge pressure, soil weight, and internal pressure using advanced finite element limit analysis. Numerical results are compared with the two-dimensional axisymmetric results, and design charts presented to cover a wide range of design parameters for practical applications. [ABSTRACT FROM AUTHOR]

Tunneling in soft clay requires accurate estimation of the inner support pressure to prevent undesired ground settlement and maintain the overall soil stability. Previous researchers have shown that the stability factor approach, which is analogous to Terzaghi's bearing capacity factors [critical stability number (Nc), Ns, and Nγ)], is effective and efficient to determine the limit loads of many geotechnical stability problems. Therefore, this paper aims to study the stability factors of four various tunnel shapes in undrained clay: the two-dimensional (2D) tunnels of circular, square, and heading in plane strain, and the three-dimensional (3D) circular tunnel heading. Using the advanced finite-element limit analysis (FELA), rigorous upper-bound (UB) solutions of the undrained stability factors (Fc, Fs and Fγ) will be produced for various tunnel depth ratios (C/D). Numerical UB results are compared with lower bound (LB) solutions. Comprehensive design charts, tables, and equations will be presented for practitioners to estimate the critical tunnel support pressure at collapse. [ABSTRACT FROM AUTHOR]

Highlights: A state of art approach to evaluate the stability of Hoek–Brown rock mass with a spherical cavity. Rigorous upper bound and lower bound solutions of stability factors are solved using advanced finite element limit analysis. Comprehensive design charts, tables and equations are presented for stability evaluation. [ABSTRACT FROM AUTHOR]

Underground water main leakage is one of the main causes of instability of soils and sinkholes. In the event of a water main burst, the pressure is upward and hence the soil layer should be analyzed for blowout stability. Conversely, leakage from low-pressure utilities such as sewer pipes would erode the surrounding soil media and leave it unstable with an internal opening created. In such a situation, the possible failure scenario would be in collapse stability. This study set out to quantify the collapse stability performance of three idealized cavity shapes above the damaged pipe. Advanced numerical limit analysis was used to obtain upper and lower bound solutions of the problem. The study provides useful engineering information in the form of design charts and tables for a wide range of design parameters, which can greatly assist in decision making by practical engineers. [ABSTRACT FROM AUTHOR]

Road-related sinkholes are of great concerns nowadays, appearing frequently in media stories. In the undrained stability analysis, a dimensionless stability number that is known as Broms and Bennermark's original stability number expresses the combined effect of surface surcharge pressure, self-weight of the soil, and the supporting pressure. This "critical" undrained stability number, Nc, is used in this paper to formulate three-dimensional (3D) upper-bound and lower-bound solutions in active (collapse) and passive (blowout) scenarios of sinkhole stability using the classic trapdoor problem. Design charts, tables, and equations were developed to cover a wide range of practical design parameters. Together with modern geophysics techniques for the detection of underground cavity as well as the findings of the associated failure patterns in this paper, the study should, therefore, be of value to practitioners in their daily decision making. [ABSTRACT FROM AUTHOR]

This paper aims to study the three-dimensional (3D) tunnel heading pressure of twin circular tunnels in a drained cohesive–frictional soil using a stability factor approach and finite-element limit analysis (FELA). The primary concept adopted will be the use of a conventional equation that is similar to the traditional bearing capacity factors (e.g., Nc, Ns, and Nγ) in Terzaghi's bearing capacity equation. For various spacing ratios (S/D) between the tunnels, the stability of the tunnels is expressed in terms of nondimensional tunnel stability factors (e.g., Fc, Fs, and Fγ), which are functions of the depth ratio (C/D) and soil internal friction angle (ϕ). For conciseness, the results will be presented in charts and tables with the tunnel stability factors that used the rigorous FELA upper (UB) and lower bound (LB) solutions. [ABSTRACT FROM AUTHOR]

This paper explores the uplift behavior of horizontal anchor plates in frictional-cohesive soils subjected to seismic loading. The study focuses on three seismic stability factors: F c , F q , and F γ , which depend on seismic coefficient K h , depth-to-width ratio H / B , and soil internal friction angle φ. To evaluate ultimate uplift load capacity while considering the influence of K h , H / B , and φ , Terzaghi's principle of superposition is introduced. Robust predictive models for these stability factors are developed using advanced computational techniques like finite element limit analysis (FELA) and Levenberg-Marquardt backpropagation neural networks (LMBPNN). These neural network models are meticulously optimized, resulting in high R-squared values (R2) and low root mean square errors (RMSE) for both training and testing datasets. Sensitivity analysis and feature importance assessments on the three stability factors indicate that the design parameter H / B has the largest SHAP value, that is followed by φ and K h. The findings significantly enhance our understanding of uplift behavior in frictional-cohesive soils under seismic loading conditions, as well as providing precise and reliable design of anchor plate systems in diverse soil environments exposed to seismic forces. • Innovative seismic uplift analysis combining stability factors and machine learning. • Meticulously curated dataset for robust and reliable engineering insights. • Practical implications for marine structures' stability and seismic safety. • Rigorous comparative analysis with existing studies validates our findings. • Interdisciplinary contribution at the intersection of marine and geotechnical engineering. [ABSTRACT FROM AUTHOR]

The problem considered in this paper is the passive earth pressure determination under various rigid wall geometry with negative wall-soil friction. An exact solution based on statically admissible stress fields is employed to evaluate the impact of negative wall-soil friction and inclined walls on the design of retaining walls. A series of conservative solutions for the passive earth pressure coefficient in the presence of negative wall friction is obtained, shedding light on the load transfer mechanism of cohesionless backfill materials. While focusing on the passive earth pressure coefficient, the study further identifies the stress state transition zone in the backfill and the influence of wall inclination on passive earth pressure. In addition, the load transfer mechanism of cohesionless backfill material in a retaining wall is affected by various factors, including wall geometry, degree of negative wall friction, the direction of the major principal stress at the wall, and the position and orientation of the transition zone and line of stress discontinuity. It follows that comprehensive design charts involving various rigid wall geometry and negative wall-soil friction are provided for engineering practice. Overall, the study successfully characterizes the admissible stress field in the backfill of rigid retaining walls, contributing to the knowledge of retaining wall design under the effect of negative wall friction. [ABSTRACT FROM AUTHOR]

Estimating active earth pressure in cohesionless backfill behind rigid retaining walls has been significantly improved through the application of cutting-edge soft computing techniques in this paper. This study delves into the intricate interplay of negative wall-soil friction with load transfer mechanisms, underpinned by a comprehensive dataset obtained from a conservative solution that leverages statically admissible stress fields. Utilizing a Bayesian regularization backpropagation neural network, we construct an explicit function for active earth pressure estimation, ensuring the model's reliability through its remarkable alignment with measured values. Furthermore, feature importance analysis and advanced mathematical modeling enrich the study, providing a practical tool for retaining wall design and analysis. This tool is adept at addressing complex scenarios, including those involving negative wall-soil friction, thereby advancing the state-of-the-art in geotechnical engineering. [ABSTRACT FROM AUTHOR]

Ring foundations are widely used to support various types of offshore structures because of the cost-effective reason. Unlike the traditional circular foundations, very few studies were reported with regard to the bearing capacity of ring foundations. In addition, the study on the stability effects of anisotropic and nonhomogeneous clays is yet to be found in the current literature. The purpose of the technical note is therefore to bridge the current research gap. By using the robust lower and upper bound finite-element limit analysis in axisymmetric conditions, new stability solutions of ring footings on anisotropic and nonhomogeneous clays are obtained using dimensionless parameters. The associated failure mechanisms are also examined and discussed, while the design equations are proposed for predicting the bearing capacity of ring foundations. The findings in this study provide a reliable solution to improve the current design standard for ring footings in anisotropic and nonhomogeneous clays. [ABSTRACT FROM AUTHOR]

The stability of a single circular tunnel in cohesive undrained soil was investigated under plain strain conditions using a two-dimensional finite-element limit analysis (FELA) program and a shear strength reduction method (SSRM). The stability for this problem was well expressed by using Broms and Bennermarks' original stability number (N = (σs + γH − σt)/Su) owing to the undrained loading conditions. The variations of the factor of safety and the critical stability number were presented for a series of tunnel cover-to-diameter ratios (C/D) in both collapse and blowout scenarios. Also, the extent of surface failure for some selected depth ratios was determined in the case of tunnel collapse. The obtained results were compared and validated by using the finite-difference method, as well as other existing solutions available in the literature. The dimensionless ratios employed in this study make the design charts suitable to cover a broad range of tunnel geometries and soil parameters. [ABSTRACT FROM AUTHOR]

This paper presents rigorous plasticity solutions to the classical active and passive earth pressure problems. The primary method adopted is a conventional equation based on the soil property and three stability factors (F c , F s, and F γ), that are analogous to Terzaghi's bearing capacity factors (N c , N s , and N γ) of strip footings. The proposed method is considered as a practical yet smart approach to the determination of earth pressures and is one of the main novelties in this study. To achieve this, the finite element limit analysis (FELA) of upper and lower bounds solutions, a powerful tool in studying the behaviour of soil stability, is employed to compute the three stability factors for a wide range of soil internal friction angles, wall roughness, and surcharge pressures. In addition, analytical solutions based on statistically admissible stress fields are adopted to validate the proposed FELA solutions. The validation satisfactorily demonstrated the accuracy and reliability of the proposed solutions. It follows that the numerical results are presented in the form of tables, figures, and several examples provided to demonstrate the practical use of the three factors in estimating active and passive earth pressures with various backfill soils, wall roughness, and surcharge pressure. The study should, therefore, be of value to practitioners. [ABSTRACT FROM AUTHOR]

The stability of a tunnel face is described by the combined effects of surcharge load, self-weight of the soil, and internal supporting pressure. This combination can cause failure in either blowout or collapse. Since the plastic shearing in undrained soils is independent of loading directions in homogeneous soils, this paper studies Broms and Bennermark's original stability number for the circular tunnel heading in cohesive soil using three-dimensional upper and lower bound finite-element limit analysis. Dimensionless ratios are used in this study to cover practical soil parameters and tunnel depths for collapse and blowout analyses. Numerical results of critical stability numbers are compared with two-dimensional and three-dimensional solutions available in the literature. Stability design charts and tables produced in this paper can be used to estimate safety factors for various design parameters. [ABSTRACT FROM AUTHOR]

Abstract This paper develops a numerical procedure for investigating settlement induced by circular tunnels in soft soils. The numerical procedure aims to simulate the movement and relaxation of the soil around the shield and lining annulus that occurs due to the overcutting and grouting of the tunnel void by a tunnel boring machine. A stress relaxation technique that progressively reduces the tunnel support pressure from a specific amount until a point of failure is detected. For three separate stages before this point of failure, the surface settlement data is exported for analysis. Using a regression of the commonly used Gaussian equation on the settlement data, i x values can be determined for each case. This is done for a number of geometry and soil stiffness and strength ratios which will cover the most practical range for soft cohesive soils. The results of this study are quite positive, settlement results compare well with previous experimental and observational results. Design charts using dimensionless ratios have therefore been presented. [ABSTRACT FROM AUTHOR]

A narrow backfill zone is formed when retaining walls are built near existing stabilized structures (e.g., rock faces). In such circumstances, the classical passive earth pressure coefficient is no longer applicable, and a correction factor is required for the design. This paper aims to develop analytical solutions for estimating the passive earth pressure problem of narrow cohesive-frictional backfills behind retaining walls. The novel arched differential element method considers both effects of the horizontal shear stress in backfills and the soil arching, and it is employed to estimate the passive earth pressure distribution along with wall depth. The solutions are compared against those published experimental data, analytical approaches, and finite-element limit analysis solutions. The factors influencing the distribution of passive earth pressure are also undertaken using a series of parametric studies. To implement the derived solutions into a routine design, a modified practical design equation is presented following the standard Coulomb's solutions. This work provides a theoretical guideline for the initial design of retaining walls with narrow soils, and it should be of great interest to practitioners. [ABSTRACT FROM AUTHOR]

Road subsidence and sinkhole failures due to shallow cavities formed by defective water main have increased in recent decades and become one of the important research topics in geotechnical engineering. The present paper numerically studies the stability and its associated failure mechanism of ellipse-shaped cavity above defective water mains using the finite element limit analysis technique. For a wide range of geometrical parameters, the pressure ratio method is used to formulate the stability solutions in both blowout and collapse scenarios. Even though there is no published solution for elliptical cavities under blowout failure conditions, the obtained numerical results are compared with available circular solutions. Several conclusions are drawn based on the failure mechanism study of the various ellipse shape transformations in this study, whilst design charts and equations proposed for practical uses. [ABSTRACT FROM AUTHOR]

The study presents an innovative hybrid machine learning model tailored for predicting the load-displacement characteristics of bored piles, specifically those integral to high-rise buildings. Incorporating critical design parameters—diameter, length, Standard Penetration Test (SPT) indices, and effective overburden pressure—the model leverages a dataset of 1650 samples from static load tests in Vietnam. This hybrid approach integrates the Three Modified Symbiotic Organisms Search algorithm (3mSOS) with the Levenberg–Marquardt backpropagation neural network (LMNN) to establish the intricate relationship between these design parameters and the load-displacement response of the piles. Numerical results underscore the model's exceptional performance in accurately predicting the load-displacement behavior of bored piles. Rigorous validation employs an independent dataset derived from bidirectional pile load tests, affirming the model's reliability. A comprehensive sensitivity analysis provides valuable insights into the mechanisms governing load-bearing. Feature importance analysis and partial dependence plots reveal nuanced relationships among input variables and output behavior. The model's novelty lies in pioneering the application of advanced metaheuristic algorithms, notably 3mSOS, in pile foundations—a distinctive contribution to geotechnical engineering. This research holds significant promise for enhancing the efficiency and accuracy of pile design in high-rise buildings, thereby bolstering the overall reliability of foundation design. • 3mSOS-LMNN transforms large bored pile foundation design, ensuring precise load-displacement predictions. • SHAP analysis pinpoints parameters influencing pile head displacement, aiding informed decision-making. • PDPs provide a profound understanding of influential parameters, emphasizing their crucial role in pile behavior. [ABSTRACT FROM AUTHOR]

• A state of art approach to study 3D sinkhole stability due to underground cavities. • Advanced 3D finite element limit analysis for circular and square openings. • Rigorous 3D upper bound and lower bound solutions of active and passive trapdoors. • Comprehensive design charts, tables and equations presented. • Stability numbers and factors of safety for a wide range of design parameters. There has been an increasing interest in the study of sinkhole occurrences due to frequent underground activities. Most of the research direction are related to the detection of the underground cavity using geophysics techniques. Very little is done in the area of soil stability. This paper investigates the three-dimensional stability of circular and square trapdoors. The combined effect of surcharge pressure, soil weight and supporting pressure is considered in Broms and Bennermarks' original stability number for a cohesive soil. The study uses the finite element limit analysis to compute upper bound and lower bound minimum supporting pressures for both collapse and blowout scenarios. The obtained critical stability numbers and factor of safety are compared with other published results in both two- and three- dimensions. Design charts, tables and equations are presented to cover a wide range of design parameters and a practical example is introduced to illustrate how to use the them. [ABSTRACT FROM AUTHOR]

This paper investigates the use of stability factors to estimate tunnel heading pressures. The primary method adopted is a conventional equation based on the soil property and stability factors, analogous to the bearing capacity factors (N c , N s and N γ) of strip footings. The finite element limit analysis (FELA) is employed to determine rigorous upper bound (UB) and lower bound (LB) solutions of stability factors (F c , F s and F γ), which are functions of the depth ratio (C/D) and soil internal friction angle (Ø). The obtained results are compared and validated by using the finite difference analysis as well as other available published results in the literature. A number of examples are illustrated on how to use the factors to estimate tunnel heading pressures. [ABSTRACT FROM AUTHOR]

This paper investigates the three-dimensional (3D) stability of a circular tunnel in drained cohesive-frictional soil. Numerical simulations are performed to study the face stability of a circular tunnel for various soil properties and tunnel diameter-to-depth ratios. The finite element limit analysis (FELA) is employed to determine rigorous upper and lower bounds solutions of tunnel stability factors (F c , F s and F γ), which are functions of the depth ratio and soil internal friction angle. These stability factors are used to estimate the critical heading pressures at collapse. The obtained results are compared with existing published solutions in the literature. The study aims to improve the available solutions by using the latest 3D finite element limit analysis technique. A number of examples are provided, which demonstrate the practical use of the three stability factors in estimating tunnel heading pressures. [ABSTRACT FROM AUTHOR]

Cement-based columns in combination with geosynthetic reinforcement is a well-established soft ground improvement technique to enhance embankment stability. This paper aims to present a finite-element (FE) study based on a case history of a geosynthetic-reinforced column-supported (GRCS) embankment over soft soil. In this study, the columns are simulated with an advanced Concrete model to simulate the development of possible cracking and induced strain-softening. Numerical results are compared against published centrifuge tests, giving confidence to the established FE model with the Concrete model. New insights into the progressive failure mechanisms of GRCS embankments over soft soil are then discussed by examining the stress paths, internal forces, and cracks, as well as the plastic failure zones of columns. In addition, the role of columns and geosynthetics on the progressive failure mechanisms (failure loads and sequences) is also examined by an extensive parametric study. The results suggest that provided the optimization of compressive and tensile forces in the columns combined with the tensile stiffness of the geosynthetics is put in place, more columns can be mobilized to resist global sliding failure and to improve the bearing capacity of GRCS embankments. • The crack-induced softening of DCM columns is captured using the Concrete model. • Progressive mechanisms of GRCS embankments over soft clay are interpreted. • The role of geosynthetic and columns on progressive failure mechanisms of GRCS embankments are identified. [ABSTRACT FROM AUTHOR]

An innovative approach that combines isogeometric analysis (IGA), limit analysis, machine learning, and the multivariate adaptive regression splines (MARS) model is presented in this paper to investigate sinkhole stability of circular cavity. The upper bound limit analysis method using IGA and second-order cone programming (SOCP) is employed to analyze circular cavity stability. Based on Bézier extraction, the non-uniform rational B-spline (NURBS) is used to generate a set of NURBS surfaces that define the boundary of the soil domain. The proposed approach is validated through comparative analysis with previous studies, demonstrating its effectiveness in accurately predicting soil stability. A large dataset consisting of 5000 randomly generated runs is used to train the machine learning algorithm that is integrated with the MARS model. The results show high accuracy, with a small mean squared error of 10–3, in predicting the undrained stability of circular cavities. The integration of IGA, limit analysis, machine learning, and the MARS model contributes significantly to advancing computational techniques for assessing soil stability. The proposed approach offers a comprehensive and precise tool for engineers and researchers, providing an accurate design formula for evaluating the undrained stability of circular cavities. [ABSTRACT FROM AUTHOR]

Every year in Japan, industry and household consumption generate a significant amount of clam shell waste. It has inevitably imposed a negative impact on the national environment and economics. To reduce those effects, this study proposes the reutilisation of abandoned clam shell for ground improvement. An experimental study was conducted to evaluate the shear strength of this new construction material. Soils were mixed with various percentages of clam shells as well as cement. The new soil-clam shellcement samples were tested under the triaxial consolidateddrained tests (CD tests). Test results showed that the addition of clam shell and cement in the soil leads to increase deviatoric stress. Furthermore, shear strength parameters of specimens were quantified in terms of cohesion and frictional resistance. Based on the results of the current study, it was concluded that approximately 9.50% increase of frictional angle can be achieved whilst the cohesion can only be improved by 6%. This new construction material can be used in the future for the base course of unpaved roads in agriculture engineering applications. [ABSTRACT FROM AUTHOR]

• Novel coupled approach for undrained stability of rectangular tunnels. • Isogeometric analysis and deep learning ensure accuracy and efficiency. • High accuracy with mean squared error of 10−6 in predicting tunnel stability. The problem considered in this paper is for the stability evaluation of a rectangular tunnel in undrained clay during lining process. The approach adopted involved the use of isogeometric analysis (IGA) and the upper bound limit analysis formulation for the stability analysis. For the geometrical representation, B-spline basis functions are used to generate a set of B-spline surfaces that define the boundary of the soil domain, allowing for the exact representation of the tunnel geometry. The upper bound limit analysis is then formulated as a second-order cone program (SOCP), which can be solved by using a numerical optimization algorithm. The accuracy and reliability of the proposed method are validated by comparing the results with those published in previous studies. Furthermore, a large dataset is generated by randomly varying the input parameters, and a deep learning model is trained to learn the dataset. The deep learning model is trained using the mean squared error (MSE) metric, which yields an MSE as small as 10−6, indicating the high accuracy and precision of the proposed approach. Feature analysis and Partial Dependence Plots (PDPs) were used to gain insights into physical behavior by identifying important variables and understanding their individual and collective effects. In conclusion, the coupling of IGA and upper bound limit analysis provides a comprehensive and reliable solution to the stability of rectangular tunnels. The results obtained from this approach are accurate and can be achieved with reduced computational cost, making it an attractive approach for practical engineering applications. This approach can be used as a basis for future research on tunnel and tunnel stability analysis and may be extended to other types of soil structures under complex geometries. [ABSTRACT FROM AUTHOR]

• A novel approach to study uplift resistance of suction caisson in NGI-ADP soils. • 2D finite element analysis for suction caisson. • Failure mechanism, respective calculated tables and charts are presented. • Machine learning approach for building empirical equation and sensitivity analysis. The paper presents a novel solution for evaluating the uplift resistance of caisson foundations in anisotropic clay using displacement finite element analysis (FEA) and artificial neural network (ANN). The commercial FEA PLAXIS code is used to examine the uplift resistance of caisson foundations with a built-in anisotropic soil model developed by Norwegian Geotechnical Institute (NGI) based on the Active-Direct Shear-Passive concept (NGI-ADP model). The uplift resistance is expressed by a dimensionless stability factor that is a function of four dimensionless design parameters, i.e., the ratio of depth to diameter, the adhesion factor at the interface between caisson and clay, the shear strength gradient ratio, and the anisotropic strength ratio. Using the produced numerical results, ANN is adopted as the data driven technique to propose an empirical equation to estimate the uplift resistance factor. Furthermore, a sensitivity study is implemented to evaluate the relative importance of the four considered parameters on the uplift resistance of the caisson. Design charts, tables and empirical equations are developed and can be used to assist in practical designs. [ABSTRACT FROM AUTHOR]

This paper presents a stability study on the collapse mechanisms of a plane-strain tunnel face in c - ϕ soils using the upper bound finite element method with rigid translatory moving elements (UBFELA-RTME) and nonlinear programming technique. Practical considerations are given to the unlined length influence behind the tunnel face. An advanced mesh adaptive updating strategy is adopted, aiming to improve the computational efficiency, the accuracy of upper-bound solutions, as well as the produced collapse mechanisms. The unlined length influence on the face stability and collapse mechanism of the tunnel face are determined with various combinations of tunnel depth ratios, soil friction angles, and dilatancy angles. Using the UBFELA-RTME with the Davis's approach and a mesh adapting strategy, the non-associated plasticity flow rule can be well approximated. The developed technique was validated against different numerical methods, and it is concluded that the tunnel face stability can be improved by increasing soil friction and dilatancy angles, and yet weakens as the unlined length increases where a mesh-liked collapse zone gradually appears on the tunnel vault top. It gradually evolves to a global collapse failure till the ground surface. The findings contribute to a better understanding of the ground surface failure under the unlined support length influence in tunnel construction. [ABSTRACT FROM AUTHOR]

Effective ground improvement technique is normally needed in improving agriculture land condition. This is to accommodate agriculture activities which have operational loadings due to tractor or rice transplanter. The use of soil - shell husk - cement combination is considered as one of the possible ground improvement techniques and it is environment friendly. In this study, several combinations of waste shell husk and cement are investigated for its effect on soil shear strength and bearing capacity. Specimens containing 10% and 20% of waste shell husk along with 2%, 4%, 6% cement were tested using California Bearing Ratio (CBR), Direct Shear Test (DST) and Unconfined Compressive Strength (UCS). Test results show that the addition of shell husk and cement typically improves the engineering properties of the soil. It is concluded that the use of soil - shell husk-cement combination for ground improvement is an effective method for agriculture land development. [ABSTRACT FROM AUTHOR]

The bearing capacity of subgrade soil plays an important role in the performance of agricultural earth structures such as farm roads or earth embankments. It also has a strong link to the budgeting efficiency of those agricultural earth structural projects. One way to improve the subgrade of soil is by using stabilised material in the subgrade layer. Shell husk waste is one of the construction materials that can be used as a substitute for the subgrade layer. The utilisation of shell husk waste has several purposes such as protecting natural aggregate and preventing problems that arise from the untreated abandoned shell husk waste. In this research, shell husk waste was used as farm road subgrade material. To understand the bearing capacity of soil specimens, a series of California bearing ratio (CBR) tests were carried out by using several types of subgrade layers containing different percentages of shell husk in the soil-shell husk mixture. Three types of subgrade layers were used: subgrade upper layer, subgrade bottom layer, and subgrade double layer, containing 0 (control), 10, 20, and 30% shell husk in soil-shell husk mixture. The experimental results showed that the addition of shell husk in soil leads to improvement in the CBR values of the ground as compared to control specimens. It was further revealed that by increasing the percentage of shell husk in the soil-shell husk mixture, the CBR value was improved significantly. The highest CBR value was achieved by using subgrade upper layer with a 30% shell husk in soil-shell husk mixture. The results obtained are encouraging with regard to the utilisation of the waste shell husks for improving the bearing capacity of agricultural earth structures such as farm roads and earth embankments. [ABSTRACT FROM AUTHOR]

Pit-in-pit (PIP) excavations in an aquifer-aquitard system likely undergo catastrophic failures under the hydraulic uplift, the associated undrained stability problem, however, has not been well analyzed in the past. To this end, a hypothetical model of PIP braced excavation in typical soil layers of Shanghai, China is developed using the finite element limit analysis (FELA) tool. The FELA solutions of safety factors (FSs) against hydraulic uplift are verified with the results from the finite element analysis with strength reduction technique (SRFEA) and existing design approaches. Subsequently, FELA is employed to identify the triggering and failure mechanisms of PIP braced excavations subjected to hydraulic uplift. A series of parametric studies considering the various geometric configurations of the PIP excavation, undrained shear strengths of aquitard, and artesian pressures are carried out. The sensitivities of relevant design parameters are further assessed using a multivariate adaptive regression splines (MARS) model that is capable of accurately capturing the nonlinear relationships between a set of input variables and output variables in multi-dimensions. A MARS-based design equation used for predicting FS is finally presented using the artificial dataset from FELA for practical design uses. [ABSTRACT FROM AUTHOR]

The use of oil-contaminated sand in building and construction is now being considered as an alternative and cost-effective way to minimize its adverse effect on the environment. To achieve this, the effect of oil contamination on the important mechanical properties of sand should be investigated first. This study investigated the effect of petroleum-derived contaminants on the water absorption, permeability, cohesion, friction angle, and shear strength of fine sand. Contaminated samples were prepared by mixing fine sand with different percentages of light crude oil (0 to 20%). The results indicated that the water absorption of fine sand decreases with an increase in crude oil. An increase in the cohesion was observed for sand with up to 1% of oil contamination, after which the cohesion began to decrease, which also results in the reduction in the permeability. A slight reduction in the friction angle was found for oil-contaminated fine sand. At a low normal stress of 50 kPa, as the percentage of light crude oil increased, the shear strength increased up to 1% of oil contamination and then it decreased. These results provided useful information on how oil-contaminated sand can be used safely and effectively in building and construction. [ABSTRACT FROM AUTHOR]

The use of finite elements and limit analysis in the stability analysis of geo-structures is not uncommon nowadays, with the assumption of associated flow rule and rigid perfectly plastic constitutive soil model. Nevertheless, the simplified assumption may lead to misevaluation of the objective function for the nonlinear optimisation solution, thus giving rise to uncertainty in the design of geo-structures. In this study, the influence of non-associated flow rule on the stability evaluations for obliquely- and eccentrically-loaded shallow foundations, as well as for retaining structures with cohesionless granular backfill, is examined using lower bound finite elements and second-order cone programming (SOCP). A wide range of dilation angles (ψ) is considered for the study (e.g., from zero to a maximum of soil internal friction angle φ), and it is generally observed that failing to consider the non-associated flow rule in the soil constitutive model would yield non-conservative designs of geo-structures. These inaccurate predictions and subsequent unreliable stability analysis are more pronounced in cases of large soil internal friction angles. The findings in this study would be of great importance for practical design applications. [ABSTRACT FROM AUTHOR]