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Ultra‐deep excavations in karst areas pose a substantial risk due to the presence of unknown karst caves. However, the literatures on deep excavations in karst regions remain limited and lack comprehensive discussion. This study investigates the effects of karst caves on the stability of the diaphragm walls (D‐walls) during an ultra‐deep excavation. A statistical analysis was conducted to examine the distribution of various parameters related to karst caves, including height, embedded depth, and roof thickness. It is revealed that these parameters follow a log‐normal distribution. There is a strong probability (99.8%) that the embedded depth will exceed 10 m, a high likelihood (82.6%) of the height being under 6 m, and similarly, an 82.2% chance that the roof thickness will be less than 5 m. A three‐dimensional finite element analysis was conducted to investigate the effects of the karst cave height, roof thickness, and location on the horizontal displacement of the D‐walls. The results show that the karst cave have significant effects on the horizontal displacement of the D‐wall, particularly at the bottom of the D‐wall. Specifically, when the karst cave has a height of 6 m, a roof thickness of 1 m, and is located at a distance of 1 m from the wall, the horizontal displacement at the bottom of the D‐wall can increase by 59 times compared with the condition without the presence of the karst cave. This severe increase in displacement results in a pronounced kick‐in failure of the D‐wall. The reason lies in the presence of the karst cave greatly reduces the bearing capacity of the bedrock within the foundation pit, thereby, rending it incapable of resisting the active earth pressure. The findings in this study can provide valuable references for formulating principles and treatment planes of the karst caves. [ABSTRACT FROM AUTHOR]

This study introduces a local radial basis function collocation method (LRBFCM) to analyzing structural deformation in deep excavation within a two dimensional geotechnical model. To mitigate the size effect caused by a large length-to-width ratio, a technique known as the 'direct method' is employed. This method effectively reduces the influence of the shape parameter, thereby improving the accuracy of the partial derivative calculations in LRBFCM. The combination of LRBFCM with the direct method is applied to the deep excavation problem, which consists of both the soil and support structures. The soil is modeled using the Drucker-Prager (D-P) elastic-plastic model, while an elastic model is employed for the support structure. Elastic-plastic discretization is performed using incremental theory. The proposed approach is validated through four different examples, comparing the results with numerical solutions obtained from traditional finite element methods (FEM). This study advocates the use of the direct method to optimize the distribution of local influence nodes, particularly in cases involving large length-to-width ratios. The combination of LRBFCM with incremental theory is shown to be effective for addressing elastic-plastic problems. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the influence of earthmoving vehicle load position on the deformation and internal force characteristics of a deep excavation (DE) support structure. The position of the earthmoving vehicle load near a DE is described by the horizontal distance between the earthmoving vehicle load and the DE. A two-dimensional finite element model is established for simulating DE engineering under the earthmoving vehicle load. The load of the earthmoving vehicle is treated as the static load, and the influence of the earthmoving vehicle load on the excavation support structure is considered from the static point of view. The numerical results of the finite element model agree well with the measured data from the field, which verifies the validity of the model. On the basis of this model, multiple models are established by changing the horizontal distance (D) between the earthmoving vehicle and the DE. The influence of D on the support structure and its critical magnitude for ensuring safety were studied. The results show that the underground diaphragm wall (UDW) is the main component for which horizontal displacement occurs under the earthmoving vehicle load. The horizontal displacements of the support structure exhibit an asymmetric distribution. When D decreases from 20 m to 0.5 m, the horizontal displacement of the UDW near the loading side increases, and the maximum horizontal displacement occurs at the top of the excavation support structure. The critical magnitude of D for ensuring safety is found to be 1 m. When D is less than 1 m, the DE is in an unsafe state. The UDW is the main component subject to the bending component. The bending moment distribution exhibits an "S" shape. The maximum bending moment increases with the decrease in D, and it occurs at the intersection of the second support and the UDW. As D decreases, the axial force in the first internal support changes from pressure to tension. The axial forces in the second and third internal supports are both pressures. The axial force in the third internal support is the largest. The research results have a positive effect on the design and optimization of DE support structures under the earthmoving vehicle load. [ABSTRACT FROM AUTHOR]

Traditional numerical analyses often overlook the potential impact of adjacent building basements on ground surface deformation. This study investigated the influence of neighboring structures on diaphragm walls and ground surface deformation during deep excavation for building foundations using PLAXIS 3D finite element software. This study simulated the top–down construction method with plate elements for diaphragm walls retaining H-shaped steel for support and pre-stressed anchors. The adjacent structures were modeled using plate elements. Numerical analysis results were compared with field observations for model validation. The results show that the lateral displacement of the retaining wall varies with the depth of neighboring basements. At 0.5 times the excavation depth, displacement was significant, and it stabilized at 1.0 times the depth. When the distance between adjacent buildings and the retaining wall was about twice the excavation depth, the deformation curve converged, indicating negligible influence beyond this distance. Ground surface settlement increased as the neighboring basement depth reached half the excavation depth, and stabilized at 1.6 times the depth. A closer proximity resulted in greater ground surface settlement. These findings offer practical references for deep excavation design and assessment, aiding engineers in ensuring project stability and safety. [ABSTRACT FROM AUTHOR]

The object of the present paper is to determine the minimum support requirements provided for the safe execution of trench excavation works for underground network receptacles. This term is used to define the open excavations, which are carried out for underground networks to be installed or constructed, and which are classified in terms of place of execution and soil categories. This paper focuses on the study of the free earth support method in excavations carried out in earthy soils and in places where the passage of the pipeline requires deep excavations of vertical front. In these cases, for reasons of safety of both the personnel and the equipment, it is necessary to support the vertical excavation fronts, even when the analyses indicate their stability. In this context, and to avoid the consequences, before the start of the excavation and at its limit, the formation of vertical support structures is required, which are commonly known as "retaining bulkheads". The basic criteria for selecting the type of the support system are soil characteristics, local conditions (surface load, groundwater table) and finally, the lifetime of the trench. Based on the above, the objective of the study is to investigate the temporary support of vertical fronts of depth trenches about 10 m, the excavation of which is carried out on earthy soil. The study is based on the implementation of the limit equilibrium method, which is applied according to the provisions—guidelines set out in Eurocode 7 (EN 1997). The study investigates the distribution of earth pressures in an anchored retaining structure of a deep excavation by extracting the main design parameters of similar systems. The goal of this work is to select the type of the support system depending on the soil properties (c, γ, φ and Ε) and local conditions, as a prerequisite for safe and rational design, while in the end of the project useful conclusions are drawn. [ABSTRACT FROM AUTHOR]

Though a comprehensive in situ measurement project, the performance of a deep pit-in-pit excavation constructed by the top-down method in seasonal frozen soil area in Shenyang was extensively examined. The measured excavation responses included the displacement of capping beam and retaining pile, settlement of ground surface, and deformation of metro lines. Based on the analyses of field data, some major findings were obtained: 1) the deformations of retaining structures fluctuated along with the increase of temperature, 2) the deformation variation of retaining structures after the occurrence of thawing of seasonal frozen soil was greater than that in winter, although the excavation depth was smaller than before, 3) the influence area of ground settlement was much smaller because of the features of seasonal frozen sandy soil, 4) the displacement of metro line showed a significant spatial effect, and the tunnel lining had an obviously hogging displacement pattern, and 5) earth pressure redistribution occurred due to the combined effects of freezing-thawing of seasonal frozen soil and excavation, leading to the deformation of metro line. The influence area of ground settlement was obviously smaller than that of Shanghai soft clay or other cases reported in literatures because of special geological conditions of Shenyang. However, the deformation of metro lines was significantly lager after the thawing of the frozen soil, the stress in deep soil was redistributed, and the metro lines were forced to deform to meet a new state of equilibrium. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to capture the mechanical response of the support structure of deep excavation subject asymmetric load. A two-dimensional (2D) numerical analysis model was established by taking a pipe gallery deep excavation subject to asymmetric load as an example. The numerical analysis results were in good agreement with the measured data, thus verified the validity of the numerical model. On this basis, the stress and displacement of support structure caused by the change in foundation asymmetric load were studied. According to the numerical results, horizontal displacement of the diaphragm wall (DW) was dominant, and the maximum horizontal displacement of the DW was 7.54 mm when the deep excavation was completed. With the increase in asymmetric load, the left wall displacement continued to increase, while the displacement of the right DW continued to decrease, and the maximum horizontal wall displacement occurred near the excavation face. The DW was the main bending component, and the maximum wall bending moment when the deep excavation was completed was 173.5 kN·m. The maximum wall bending moment increased with the increase in asymmetric load, and the maximum wall bending moment on the left of the deep excavation was greater than that on the right. The inner support sustained the main component of axial force, with the axial force peaking at 1051.8 kN when the deep excavation was completed. The axial force of the inner support increased with increasing the asymmetric load, and the axial force of the second inner support was obviously greater than that of the first inner support. This research has a positive effect on the design and optimization of deep excavation support structure subject to asymmetric load on ground surface. [ABSTRACT FROM AUTHOR]

This paper investigates the use of a protective pile row barrier to mitigate the risk due to a deep excavation in soft soils adjacent to an existing tunnel. The study includes two reduced-scale 1 g model tests with and without the barrier, along with monitoring data from a case history in Wuhan, the Huazhong Science and Technology Industrial Park basement; physical testing and numerical sensitivity study results are compared to the case history to evaluate the barrier efficiency. The monitoring data show successful excavation and basement construction within allowable displacement thresholds in the presence of the barrier. The entire tunnel settled and translated towards the excavation, although different types of ovalization of the tunnel cross-sections were recorded depending on their alignment to the excavation (centre and corners). Experimental results indicate that the pile row barrier can withstand a portion of the soil pressure on the diaphragm wall, leading to a substantial reduction in tunnel bending moments and displacements; in particular, experimental results showed a greater percentage reduction in settlements than horizontal movements of the existing tunnel. When a pile row barrier is constructed in proximity to the retaining wall, it can help to minimise the detrimental effects of the deep excavation on the existing tunnel, similar to twin retaining wall scenarios. [ABSTRACT FROM AUTHOR]

This paper focuses on the performance of a braced deep excavation in soft soil based on field monitoring and numerical modeling. Laboratory tests were conducted to determine the soil parameters used in the modified Cam-Clay (MCC) model. Intelligent field monitoring means were adopted and a three-dimensional model was established. Spatial and temporal effects induced by the excavation are investigated for the deep-large foundation pit in soft soil. Deformation characteristics of the enclosure structure and the surrounding environment throughout the excavation process are presented. The behaviors of diaphragm walls, columns, the maximum wall deflection rate, ground surface settlement, and utility pipelines were focused on and investigated during the whole excavation process. Besides, the axial forces of the internal supports are analyzed. Based on the measured and simulated data, the following main conclusions were obtained: the numerical simulation results are in good agreement with the measured values, which proves the accuracy of the model parameters; the wall and the ground surface showed the maximum displacement increment at stage 9, which was a coupled product of the "creep effect" of the soft soil in Nanjing, China and the "depth effect" of the excavation; as the excavation progressed, the ground settlement changed from a "rising" to a "spoon-shaped" trend, dvm was measured between dvm = 0.0686%H and dvm = 0.1488%H; the rebound deformation curve of the pit bottom was corrugated, and the depth of disturbance of the pit bottom after the completion of soil unloading was 2-3 times the excavation depth; the closer the pipeline is to the corner of the pit, the less the excavation process will affect the settlement of the pipeline and the less the obvious pit corner effect will occur; the support strength of the buttress and the longest corner brace should be strengthened during the actual construction process to ensure the stability of the foundation deformation. [ABSTRACT FROM AUTHOR]

The application of steel strut force servo systems in deep excavation engineering is not widespread, and there is a notable scarcity of in-situ measured datasets. This presents a significant research gap in the field. Addressing this, our study introduces a valuable dataset and application scenarios, serving as a reference point for future research. The main objective of this study is to use machine learning (ML) methods for accurately predicting strut forces in steel supporting structures, a crucial aspect for the safety and stability of deep excavation projects. We employed five different ML methods: radial basis function neural network (RBFNN), back propagation neural network (BPNN), K-Nearest Neighbor (KNN), support vector machine (SVM), and random forest (RF), utilizing a dataset of 2208 measured points. These points included one output parameter (strut forces) and seven input parameters (vertical position of strut, plane position of strut, time, temperature, unit weight, cohesion, and internal frictional angle). The effectiveness of these methods was assessed using root mean square error (RMSE), correlation coefficient (R), and mean absolute error (MAE). Our findings indicate that the BPNN method outperforms others, with RMSE, R, and MAE values of 72.1 kN, 0.9931, and 57.4 kN, respectively, on the testing dataset. This study underscores the potential of ML methods in precisely predicting strut forces in deep excavation engineering, contributing to enhanced safety measures and project planning. [ABSTRACT FROM AUTHOR]

This research advances the understanding of deep excavation impacts by integrating a refined Finite Element Method (FEM) analysis with empirical data, specifically examining the behavior of retaining structures in urban environments. Unlike prior studies that predominantly relied on theoretical models, this paper combines FEM with statistical methods, particularly ANOVA, to identify critical factors affecting the performance of barrette walls during excavation. The primary objective of this study is to analyze the deformation and force behaviors at various depths, thereby enhancing the predictive capabilities of existing models. The findings highlight significant variations in horizontal displacements (Uy) and vertical displacements (Uz) across different excavation stages, with notable mean differences ranging from 0.000529420 m to 0.000700240 m for Uy and -0.017563652 m for Uz. Axial forces (N1) also show significant increases with depth, reaching a mean difference of 516.137991 kN/m. These results underscore the importance of adaptive design strategies in deep excavation projects. However, the study is limited by the specific geological conditions and the scope of empirical data used for model validation. Practical recommendations include enhancing real-time monitoring systems and applying refined methodologies. [ABSTRACT FROM AUTHOR]

This study introduces the Passive Earth Reinforcement for Lateral Equilibrium Optimisation (PERLEO) methodology, a novel approach to enhancing stability in deep excavations. Aimed at addressing limitations in existing geotechnical practices, especially in reducing deformations and bending moments in retaining structures, PERLEO utilises soil–cement blocks as passive reinforcement. Employing comprehensive numerical analysis through PLAXIS 2D software, the research advances traditional methods with sophisticated computational modelling. This study thoroughly evaluates the effect of soil–cement blocks’ geometrical configurations on the lateral displacement and bending moments of retaining walls. Key findings indicate that optimal dimensions of these blocks significantly mitigate wall deflection and bending moments, thereby enhancing the stability and the overall integrity of deep excavation projects. Additionally, this research introduces design charts, providing tools for engineers to determine the estimates for maximum lateral displacement and maximum bending moment, based on the specific dimensions of soil–cement block configurations and the depths of excavation and embedment. This methodology not only contributes to improved safety and efficiency in deep excavation works but also offers a more economical approach by reducing potential financial and temporal hazards associated with structural failures in complex geotechnical projects.

The objective of this paper is to investigate the effects of spatial variability in coastal silty soil properties on the stability and failure probability of deep excavation. A super-large irregularly shaped deep excavation in the coastal area in Wenzhou, China, is considered. A numerical model is established based on the random field theory, finite difference method and Monte-Carlo simulation method. Focusing on the friction angle and cohesion, the effects of horizontal and vertical correlation distances and variation coefficients on excavation stability are systematically studied. Meanwhile, the reliability evaluation approach is also applied to systematically examine the impact of the correlation distance on the surface settlement and horizontal displacement of pile. The results show that the greater correlation distance leads to a larger dispersion degree of the ground settlement curve and the displacement curve of the diaphragm wall around. The influence of the horizontal correlation distance on land settlement is more significant. The horizontal and vertical displacements of the pile top are less affected by the correlation distance. Compared with the deterministic analysis, the random analysis results considering the soil spatial variability produce larger displacement.

To minimize the impact on nearby structures during deep excavations, choosing an appropriate soil constitutive model for analysis holds significant importance. This study aims to conduct a comparative analysis of various constitutive soil models—namely, the Mohr–Coulomb (MC) model, the hardening soil (HS) model, the hardening soil small strain (HSS) model, and the soft soil (SS) model—to identify the most suitable model for the lacustrine deposit. To implement these models, the soil’s index properties and mechanical behavior were evaluated from undisturbed soil samples. The numerical simulation and verification of these properties were carried out by comparing the laboratory test results with the outcome of the finite element method; the most suitable constitutive soil model for the soil was identified as the HSS model. Upon analyzing the wall deflection and ground settlement profiles obtained from respective constitutive models, it was observed that the HS and HSS models exhibit similar characteristics and are well-suited for analyzing typical lacustrine soil. In contrast, the MC and SS models yield overly optimistic results with lower wall deflection and ground settlement and fail to predict realistic soil behavior. As a result, this research highlights the significance of selecting the appropriate constitutive soil model and refining the parameters. This optimization process contributes significantly to the design of support systems, enhancing construction efficiency and ensuring overall safety in deep excavation projects.

As urbanization gathers pace, projects involving adjacent subway tunnels are increasing, thereby amplifying the need for robust tunnel protection measures. Currently, there exists a notable lack of precise analyses on the three‐dimensional (3D) deformation laws and mechanisms of tunnels affected by adjacent deep excavation. Moreover, the influence patterns of retaining wall stiffness and deep excavation depth on the 3D deformation of pit‐side tunnels remain unclear. The purpose of this research is to bridge the existing disparity by adopting the hypoplastic model, which effectively captures soil stiffness that is dependent on soil state, strain, and stress path, even at small strains, as well as soil strength, based on reported centrifuge model tests. This approach facilitates a comprehensive, precise numerical analysis of the interaction between deep excavation and preexisting tunnels located outside the retaining wall. The analysis sheds light on the deformation mechanisms and trends of pit‐side tunnels not solely confined to the longitudinal axis but extending to the transverse plane as well, while systematically examining the influence of varying excavation depths and retaining wall stiffness on key tunnel parameters, including longitudinal deformation, diameter changes, bending strains, and soil pressure distributions around the tunnels. The study reveals that if the tunnel situated outside the retaining structure lies beneath the foundation pit's base, deep excavation only slightly deforms the tunnel. However, when the tunnel outside the retaining structure is positioned above the pit's base, its deformation progressively intensifies with deeper excavation, but the growth rate has a decreasing trend. An enhancement in the stiffness of the retaining wall results in a notable decrease in the deformation exhibited by the adjacent tunnels. The findings contribute to a deeper understanding of the complex responses of pit‐side tunnels to excavation activities, ultimately facilitating the design and construction of safer and more resilient urban subway infrastructure. [ABSTRACT FROM AUTHOR]

Excavation-induced soil arching is a key factor influencing the responses of the ground and underlying structures. This soil arching below an excavation base is defined as downward soil arching in comparison with that above a trapdoor or tunnel, featured with the downward developing direction. To recognize and assess the downward soil arching, two centrifuge tests in the plane-strain condition were conducted in the dense and loose sand. Variations of Earth pressure, basal heave, and shear wave velocity below the excavation base were observed, and the influence of the relative density was also investigated. The test results indicated the existence of differential deformation and stress transfer below the excavation base, and the downward soil arching is confirmed. The contributions of the downward soil arching to the restriction of the excavation-induced stress release and the ground response were found. Further, the boundary of the loosened zone and the width of the arch foot were determined in the dense and loose sand, respectively. In addition, the arched-type basal heave and stress-related shear wave velocity were observed. The significant ground heave and reduction of the shear wave velocity were found within the loosened zone. [ABSTRACT FROM AUTHOR]

The prevailing design methodology for foundation pit support structures conventionally treats the pit cross section as a two-dimensional plane, facilitating the computation of soil and water pressures acting upon the retaining structure. Regrettably, this conventional approach tends to overlook the critical corner effect, particularly when the foundation pit is in proximity to a subway tunnel, where the nuanced nature of this corner effect remains indeterminate. Consequently, this research is directed toward an in-depth investigation of a deep foundation pit contiguous to a subway tunnel. A systematic evaluation and optimization of the corner effect pertaining to the deep foundation pit are undertaken through a combination of comprehensive field monitoring and simulation methodologies. The results show that a substantial mitigation in the deformation of the supporting structure, settlements of the ground surface and adjacent buildings, as well as the displacement of the subway tunnel, were achieved through a consideration of the corner effect. Notably, the ameliorative impact of adjacent buildings on the corner effect is observed. Further scrutiny reveals that the supporting structure within a distance of 12 m from the pit corner is most susceptible to the corner effect, as evidenced by a plane strain ratio (PSR) falling below 0.8. Beyond a spatial threshold of 20 m, the PSR attains a value of 1.0, indicative of a negligible corner effect and the foundation pit section existing in a plane strain state. The adjustment of pile length or diameter based on the PSR emerges as a viable strategy that can realize the construction cost optimization on the premise of ensuring the stability of the foundation pit. The impact of pile diameter variation is paramount, corresponding to a reduction in the range of PSR values below 0.8 from 12 m to 9.8 m. The corner effect is significantly diminished. [ABSTRACT FROM AUTHOR]

Currently, the use of underground automatic car parks is becoming increasingly popular in Bangkok as it can help maximize space usage without ramps. However, an automatic system requires large openings in the basement slab, resulting in the slab possibly having insufficient axial capacity. This paper focused on one of the latest underground automatic car park construction projects in Bangkok's city center, True Digital Park, which comprises a total of four basements with a 13.20 m maximum excavation depth, including mat foundation and lean concrete. An 800mm-thick diaphragm wall (D-wall) was proposed to serve as a soil-retaining structure with 3 layers of full-temporary bracing. The Finite Element Method (FEM) with the Mohr-Coulomb soil model was employed for the D-wall design and horizontal movement prediction, and the actual construction of the basement and building have since been completed. The field performance of the D-wall construction was evaluated through horizontal movement using installed inclinometers. During every stage of construction, including soil excavation and bracing installation, horizontal displacement was monitored carefully and strictly controlled to minimize the D-wall movement. The monitoring results showed suitable agreement with the FEM analysis. However, movement of the retaining wall was detected during upward construction, even though the basement was fully cast, suggesting insufficient axial basement slab capacity as well as care and control for similar projects. This article describes the construction and monitoring of the project together with field performance results. [ABSTRACT FROM AUTHOR]

To minimize the impact on nearby structures during deep excavations, choosing an appropriate soil constitutive model for analysis holds significant importance. This study aims to conduct a comparative analysis of various constitutive soil models—namely, the Mohr–Coulomb (MC) model, the hardening soil (HS) model, the hardening soil small strain (HSS) model, and the soft soil (SS) model—to identify the most suitable model for the lacustrine deposit. To implement these models, the soil's index properties and mechanical behavior were evaluated from undisturbed soil samples. The numerical simulation and verification of these properties were carried out by comparing the laboratory test results with the outcome of the finite element method; the most suitable constitutive soil model for the soil was identified as the HSS model. Upon analyzing the wall deflection and ground settlement profiles obtained from respective constitutive models, it was observed that the HS and HSS models exhibit similar characteristics and are well-suited for analyzing typical lacustrine soil. In contrast, the MC and SS models yield overly optimistic results with lower wall deflection and ground settlement and fail to predict realistic soil behavior. As a result, this research highlights the significance of selecting the appropriate constitutive soil model and refining the parameters. This optimization process contributes significantly to the design of support systems, enhancing construction efficiency and ensuring overall safety in deep excavation projects. [ABSTRACT FROM AUTHOR]

Compared to conventional support methods, the close-fitting pile–wall integration technique features a minimized construction spacing between the retaining pile and the basement retaining wall. This approach leverages the pile stiffness to minimize the wall thickness and enhance underground space utilization. However, it currently lacks significant discussions and measured data about the interaction laws between the pile and the wall. The model test and finite element method (FEM) are employed to study the deformation and internal force interaction laws of two typical close-fitting pile–wall integrated structures, and a comparison with conventional design is conducted. Furthermore, this study separately investigates the impact of sensitivity factors, specifically the pile–wall stiffness ratio and floor plate stiffness, on both structures during the basement construction and serviceability stages. The test results can closely match the numerical simulation. The study results reveal that the wall impacts the bending moment of the pile to some extent. The internal force in the wall is significantly influenced by the lateral deformation of the pile and the floor plate. Compared to conventional designs, this structure significantly reduces the bending moment of the wall, particularly in the composite structure. Additionally, the analysis of sensitivity factors reveals their considerable influence on the pile–wall interaction. [ABSTRACT FROM AUTHOR]

Shanghai clay exhibits overconsolidation, soil structural, and small-strain characteristics. While there have been several studies on the effects of small-strain characteristics on the deformation caused by deep excavation, the effects of overconsolidation and structural behaviors on this deformation remain unexplored. Therefore, in this study, a constitutive model considering the aforementioned three characteristics is developed and then implemented in the commercial software program FLAC3D (version 7.00) to investigate the effects of overconsolidation and structural behaviors. Initially, validation and parametric study of the constitutive model are conducted based on a cylindrical numerical model. Subsequently, the constitutive model is validated by a well-documented case history of a deep excavation in Shanghai. Thereafter, the effects of overconsolidation and structural behaviors on wall deflection and ground settlement induced by deep excavation are investigated. It is observed that overconsolidation has a significant effect on the deformation induced by deep excavation, while the effect of soil structure is negligible. With an increase in excavation depth, the effect of overconsolidation on the deformation increases, and its effect on ground settlement is more significant than that on wall deflection. According to the results of the parametric study, it is revealed that by the time the shear strain induced by deep excavation reaches a maximum value, overconsolidation has partially degraded while soil structure has not yet collapsed, which accounts for the magnitude of the aforementioned effects induced by deep excavation. [ABSTRACT FROM AUTHOR]

Determining the modulus of elasticity for soil is crucial in geotechnical engineering when conducting stress-deformation analyses. However, due to the difficulty involved in calculating this parameter, as well as the fact that the modulus of elasticity for soil is nonlinear in nature, there is often uncertainty surrounding its value. A study was therefore conducted to investigate these uncertainties and their impact on geotechnical analyses and plans. The study involved modeling and numerically analyzing a deep drilling guard structure using the anchoring method. To obtain the necessary information, two projects – depth and guard structure, which were both undertaken by Jahan Mall and Baran - in Mashhad were selected as case studies. In this study, the Jahan Mall project pit was analyzed using both two- and three-dimensional numerical models. Four different models were used: Moore-Coulomb (MC), hardening soil (HS), hardening soil with small strain stiffness (Cysoil HSS), and a newly developed nonlinear model based on the Moore-Coulomb model. To carry out the analysis, information obtained from barometric tests, standard penetration tests, and shear wave propagation was used. The results of the analysis were compared with each other and with the monitoring data. It was found that for the Moore-Coulomb behavior model, the pressure modulus (Ep) should be corrected to three to five times its original value in order to obtain accurate results. However, for the Cysoil HSS, HS models, and the newly developed model, there was no need to correct the pressurometric data or shear wave propagation. Additionally, it was determined that while no correction is necessary when using standard penetration numbers, an appropriate relationship should be used to convert them into the modulus of elasticity. Based on these findings, the Gud Baran project was analyzed, and it was concluded that the newly developed model and method for converting standard penetration numbers can be applied broadly and produce desirable results. [ABSTRACT FROM AUTHOR]

The objective of this study is to assess the impact of utilizing a BW (Buttress wall) to control the deflection of a diaphragm wall in colluvial soil conditions in Vietnam. The physical and mechanical properties of the colluvial layers are evaluated using data closely monitored during a specific project, serving as validation for 3D numerical simulations utilizing the Hardening Soil Model. The analysis results closely match the field monitoring data, which has tested the accuracy of the simulation model. This forms the basis for further investigations into the dimensional parameters of BW walls, including length, thickness, and spacing between them. The results obtained from the parametric study demonstrate that altering the wall length and spacing between BWwalls significantly limits the deflection of the diaphragm wall, while changes in thickness have a negligible effect. Through the 3D numerical simulations, a linear relationship between the maximum wall deflection and parameters such as wall length and spacing between BW walls has been established.

Abstract Traditional support structures cannot meet the complex conditions of different excavation depths and areas in underground transportation hubs. On the basis of fully considering the spatial position relationship of foundation pit groups, this article proposes a multilevel retaining system that meets the requirements of multilevel foundation pit excavation. The evolution law of the support structure during the excavation process of the inner pit was explored using on-site monitoring and numerical simulation methods. The results indicate that the excavation of the inner pit reduces the passive earth pressure, and the deformation of the outer support structure can be effectively suppressed by setting a retaining structure or a bottom slab in the bench zone. The excavation of the inner pit causes significant vertical deformation of the support structure adjacent to the foundation pit, while the impact on the structure far away from the foundation pit is relatively small. According to the contact force chain and soil pressure between the two rows of support structure, the soil in this area is divided into a “relaxation zone” and a “compression zone.” The evolution mechanism of earth pressure in the case of mutual-effect failure between two rows of piles is revealed. This paper addresses the deformation properties of multilevel support structures as well as the mechanism of earth pressure evolution between structures.

Real-time prediction of excavation-induced displacement of retaining pile during the deep excavation process is crucial for construction safety. This paper proposes a modified back analysis method with multi-objective optimization procedure, which enables a real-time prediction of horizontal displacement of retaining pile during construction. As opposed to the traditional stage-by-stage back analysis, time series monitoring data till the current excavation stage are utilized to form a multi-objective function. Then, the multi-objective particle swarm optimization (MOPSO) algorithm is applied for parameter identification. The optimized model parameters are immediately adopted to predict the excavation-induced pile deformation in the continuous construction stages. To achieve efficient parameter optimization and real-time prediction of system behavior, the back propagation neural network (BPNN) is established to substitute the finite element model, which is further implemented together with MOPSO for automatic operation. The proposed approach is applied in the Taihu tunnel excavation project, where the effectiveness of the method is demonstrated via the comparisons with the site monitoring data. The method is reliable with a prediction accuracy of more than 90%. Moreover, different optimization algorithms, including non-dominated sorting genetic algorithm (NSGA-II), Pareto Envelope-based Selection Algorithm II (PESA-II) and MOPSO, are compared, and their influences on the prediction accuracy at different excavation stages are studied. The results show that MOPSO has the best performance for high dimensional optimization task.

This work proposes a novel technique to conduct back‐analysis of lateral displacement of deep cement mixing (DCM) columns in deep excavation construction. For the first time, we propose a process to investigate both soil and underground structure end‐to‐end automatically. The novel technique is a complex combination of three crucial factors: (1) a nature‐inspired optimization algorithm (O), (2) a three‐dimensional PLAXIS Geotechnical Engineering software (P) and (3) a modern Python language programming (P), hereinafter called the a nature‐inspired optimization algorithm (O), a three‐dimensional PLAXIS Geotechnical Engineering software (P) and a modern Python language programming (P) (OPP) technique. The novel meta‐heuristic algorithm simulated the co‐evolved partnership behavior of shrimps and goby fishes, termed Shrimp and Goby Association (SGA), which plays an important role in complex analyses. A series of exams to determine the SGA's performance is conducted on 38 benchmark test functions (IEEE Congress on Evolutionary Computation 2017 and 2019) and three real‐world engineering design problems to showcase its applicability. The metaheuristic and PLAXIS 3D analysis work well together, which makes the back‐analysis technique powerfully to determinate stiffness parameters instead of the traditional approaches. Based on the optimized parameters, the lateral deflection of DCM and soil are well predicted for excavation. This study proposes a technique to estimate efficiently the stiffness parameter for very soft soil. As a consequence of the optimization process, an equation to determine the stiffness parameter of DCM columns from laboratory test is also proposed. Based on the obtained results, this research provides a comprehensive methodology for predicting risk, enhancing safety, saving time and money, and effectively designing and constructing underground structures. [ABSTRACT FROM AUTHOR]

The cross wall is commonly implemented to restrain the excessive wall displacement induced by deep excavation, which has been verified through comprehensive studies and case histories. However, no study has been conducted on the excavation stability with the cross wall, which is the main concern in the deep excavation problem. In this study, a series of three-dimensional finite element methods were carried out to evaluate the performance of cross walls in resisting the basal heave in deep excavations. The results concluded that the frictional resistance acting on the contact surface area between the cross wall and the surrounding soil plays an important role in the basal heave resistance. Thus, enlarging the dimension of the cross wall would enhance the frictional resistance area and increase the factor of safety. In addition, a new simplified method is proposed to estimate the factor of safety against basal heave for the case with and without the cross wall and further validated by the finite element results. Finally, a new design chart was introduced to predict the maximum wall displacement for deep excavations with the cross wall based on the proposed system stiffness ratio and factor of safety against basal heave, which was verified through the case histories. [ABSTRACT FROM AUTHOR]

Environmental responses to deep excavations are combined results of numerous factors. The effects of some factors are relatively straightforward and can be considered carefully during the design. On the other hand, more features impact excavation-induced performances indirectly, making their influences difficult to be clearly understood. Unfortunately, the complexity and non-repeatability of practical projects make it impossible to thoroughly understand these issues through realistic deep excavation projects. Therefore, parametric studies based on repeatable laboratory and numerical tests are desired to investigate these issues further. This work examines the influence of several key features on excavation-induced displacements through a series of 3D numerical tests. The study includes the choice of soil constitutive models, the modeling method of the soil–wall interface, and the influences of various key soil parameters. The comparison shows that the MCC model can yield a displacement field similar to the HSS model, while its soil movement is greatly improved compared to the MC model. Both the soil–wall interface properties and soil parameters impact the excavation-induced displacement to a large extent. In addition, the influence mechanisms of these parameters are analyzed, and practical suggestions are given. The findings of this paper are expected to provide practical references to the design and construction of future deep excavation projects. [ABSTRACT FROM AUTHOR]

Traditional support structures cannot meet the complex conditions of different excavation depths and areas in underground transportation hubs. On the basis of fully considering the spatial position relationship of foundation pit groups, this article proposes a multilevel retaining system that meets the requirements of multilevel foundation pit excavation. The evolution law of the support structure during the excavation process of the inner pit was explored using on-site monitoring and numerical simulation methods. The results indicate that the excavation of the inner pit reduces the passive earth pressure, and the deformation of the outer support structure can be effectively suppressed by setting a retaining structure or a bottom slab in the bench zone. The excavation of the inner pit causes significant vertical deformation of the support structure adjacent to the foundation pit, while the impact on the structure far away from the foundation pit is relatively small. According to the contact force chain and soil pressure between the two rows of support structure, the soil in this area is divided into a "relaxation zone" and a "compression zone." The evolution mechanism of earth pressure in the case of mutual-effect failure between two rows of piles is revealed. This paper addresses the deformation properties of multilevel support structures as well as the mechanism of earth pressure evolution between structures. [ABSTRACT FROM AUTHOR]

Given their high cost, servo steel struts typically are used only in specific sections of foundation pits in which nearby buildings are sensitive to excavation-induced deformation. Servo steel strut adjustments affect the mechanical behaviors of adjacent ordinary-steel-strut-supported areas. However, the plane strain assumption is used in current designs, ignoring this influence. To propose a more reasonable design, the effects of servo steel strut adjustments should be examined. In this study, a model support system with adjustable strut axial forces was constructed (scale: 1∶20 , under 1g), and several groups of tests with different adjustment schemes were conducted. The lateral earth pressure, lateral wall deflection, and strut axial forces were monitored and analyzed. The results indicated the following: (1) the first level of struts is not suitable to be actively adjusted because this can increase the maximum lateral wall deflection; (2) increasing the strut axial forces can lead to redistribution of lateral earth pressure along the horizontal direction, which can be divided into two areas with different characteristics, and whereas the lateral wall deflection decreases in both areas, the lateral earth pressure increases in the area adjacent to the adjusted strut and decreases in the other area; and (3) a transition section can be designed between the servo-steel-strut-supported area and the ordinary-steel-strut-supported area, within which strut adjustment diminishes as one approaches the ordinary-steel-strut-supported area. However, the horizontal length of the transition section should exceed a threshold value, which is approximately 3 times the horizontal strut distance, to effectively mitigate the axial force reduction in ordinary steel struts. [ABSTRACT FROM AUTHOR]

Excessive column pile heave may result in engineering disasters such as instability of retaining structures and cracking of existing engineering piles in deep excavations. However, factors such as support weight, changeable support restraint resistance, and soil disturbance at the bottom of the excavation are often ignored or simplified in existing calculation methods but have a significant impact on the calculation results. Based on field soil parameters obtained by the rebound–recompression method, a semi-analytical method is proposed for estimating column pile heaves in a deep excavation. This method considers the influence of soil disturbance, the weight of the retaining structure, and the changeable horizontal support restraint, making the calculation result more consistent with the realistic situation. This method can also be used to analyze load transfer between the pile and the surrounding soil. The rationality of this proposed calculation method is verified by measured data, where the variation in pile stress state during deep excavation is analyzed. Finally, a parametric study is conducted, and the results show that the excavation size and the excavation depth have a great influence. However, the heave is hardly affected by the value of the limit relative displacement. The use of long piles with small diameter and the method of small block excavation are effective means to control the column pile heave. When the excavation area is large or the effective pile length is short, the factor of the position of the column pile cannot be ignored. [ABSTRACT FROM AUTHOR]