bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting the shear modulus and damping ratio of soils using machine learning models
Authors: Bayat M , Mousavi Z , Feng W W
Published: May 2024

In geotechnical engineering, the accurate estimation of fundamental soil properties, such as the shear modulus ratio (G/G
max) and damping ratio (D), is crucial to design and analyze various structures subjected to dynamic loads. This study presents a comprehensive investigation on harnessing the power of machine learning techniques to precisely predict G/G
max and D of granular soils. Using an extensive dataset gathered from cyclic triaxial and resonant column tests on diverse mixtures of sand and gravel, combined with previous research findings, a series of advanced machine learning algorithms including shallow neural networks, support vector regression, gradient boosting regression, and deep feed forward neural network (DFFNN) were developed. The proposed models elucidate various influential parameters, including the grading characteristics, void ratio, confining pressure, consolidation stress ratio, and specimen preparation techniques. The superiority of the DFFNN model in terms of accuracy and predictive performance was demonstrated through rigorous evaluation and comparison. This study contributes to a better understanding of soil behavior under dynamic conditions. It also provides a robust framework to employ machine learning in predicting G/G
max and D of granular soils, thereby enhancing the efficiency and reliability of geotechnical designs and construction practices.
Natural frequency of offshore wind turbines on monopiles in sand
Authors: Zhang Chenrong , Wang Ruilai , Wang Zhenyu
Published: May 2024

Offshore wind turbines are important for developing sustainable alternative energy sources. Assessing their natural frequencies is a major challenge since resonance can cause damage and even failure, especially for long-term dynamic behavior owing to environmental loads. Several model tests were conducted to understand the long-term dynamic responses of monopile-supported wind turbines buried in sand. An electrodynamic actuator was used to obtain the resonant responses of the structure and a cyclic loading device based on eccentric masses was used to apply long-term cyclic loading. The development of the natural frequency under long-term cyclic loading was investigated for two relative sand densities, three cyclic load amplitudes, and four cyclic numbers. Based on the test results, the frequency increased with increased cyclic number owing to the densification of sand. A larger amplitude results in a larger frequency for medium-dense sand, whereas the opposite tendency exists for dense sand; this is attributed to the reduced embedded depth of the monopile in dense sand accompanied by the subsidence of sand. A non-dimensional framework was used to interpret the change in the natural frequency when subjected to long-term cyclic loads. The empirical equation with the non-dimensional parameter provides an assessment of the long-term natural frequency.
Machine learning ground motion models for a critical site with long-term earthquake records
Authors: Zhan W W , Chen Q S
Published: May 2024

Ground motion models derived using data from widespread stations and earthquakes induce significant aleatory variability when applied to predict ground motions for a single site. This issue can be even worse when the sites of interest show complex site response characteristics and do not have enough similar sites in the ground motion model development dataset. This work provides a machine-learning-based ground motion modeling framework for sites with numerous earthquake recordings. The Onahama Port Array, a liquefiable site in Japan that has recorded more than 1200 earthquakes in the last 25 years, was selected as a case study. The gradient boosting method was employed to predict response spectra with periods from 0.01 to 10 s for earthquakes with Japan Meteorological Agency (JMA) magnitude ranging from 2.4 to 9.0. Different predictor combinations were tested, and two gradient boosting models were recommended: the basic model that requires earthquake magnitude and epicentral distance as inputs, and the optimal model that requires three additional inputs, focal depth, azimuth, and rainfall. The basic and optimal gradient boosting models have the root mean square error of 0.004 and 0.001 g, average r2 of 5-fold cross validation of 0.915 and 0.983, respectively. The results shed light on seismic hazard assessment for critical sites with long-term earthquake recordings.
Pore pressure development model of fiber-reinforced calcareous sand based on shear strain characteristics
Authors: Zhou Lin , Chen Jian-Feng , Li Xiao-Jun , Zhu Yan
Published: May 2024

In this study, the pore pressure buildup characteristics of fiber-reinforced calcareous sand were investigated by examining the influences of fiber contents and fiber length through a series of cyclic simple shear tests. The test results indicate that the generation mechanisms of pore pressure ratio and shear strain of fiber-reinforced calcareous sand are interrelated under cyclic loading. The fiber content and fiber length have a significant influence on the relationship of pore pressure ratio versus number of cycles. Nevertheless, the correlation of pore pressure ratio versus shear strain is independent of fiber content and fiber length. According to the unique relationship, a pore pressure development model based on shear strain was established, exhibiting excellent predictive accuracy in simulating the pore pressure generation of fiber-reinforced calcareous sand with various fiber content and fiber lengths under cyclic loading. Moreover, the proposed model is also applicable to clean calcareous sand and siliceous sand.
Effects of freeze-thaw cycles on the tensile properties of geogrids and shear behavior of geogrid-soil interface
Authors: Meng Ya , Xu Chao
Published: May 2024

The tensile strength of geogrids and the shear strength of the reinforced soil interface are critical technical indicators for designing reinforced soil structures. This study developed a temperature-controlled apparatus to examine the tensile properties of geogrids subjected to freeze-thaw cycles within the soil, and the effect of interface temperature and freeze-thaw cycles on the shear behavior of the geogrid-soil interface. Eight and four groups of direct shear and tensile tests were conducted on the geogrid-soil interface and geogrids, respectively, under varying conditions. The peak tensile strength of geogrids remained similar to that of non-freeze-thaw samples after experiencing freeze–thaw cycles within the soil. tensile properties of geogrids were independent of the number of freeze–thaw cycles. At constant water content (w=6%), the peak shear stress at the geogrid-soil interface decreased by 24% (7 freeze-thaw cycles) compared to the non-freeze-thaw group. The cohesion and friction angle of the geogrid-soil interface decreased with increasing freeze-thaw cycles but tended to stabilize after 4 freeze-thaw cycles. The reinforcement provided by the geogrid enhanced with decrease in the interface temperature. The shear stress was higher at interface temperature under 0 °C, whereas in a non-frozen state, the interface exhibited lower shear stress with a consistent stable value.
Hydraulic conductivity of bentonite–polymer geosynthetic clay liners subject to wet–dry cycles used in landfill cover systems
Authors: Zhao Hanrui , Stark Benjamin M , Tian Kuo
Published: May 2024

This study evaluated the hydraulic conductivity of bentonite–polymer (B-P) geosynthetic clay liners (GCLs) subjected to wet-dry cycles that simulated seasonal conditions on a GCL installed in a landfill cover system. Hydraulic conductivity tests were conducted on B-P GCLs and NaB GCLs at 10 kPa in accordance with the ASTM D5084 standard. Two wet–dry methods were used to investigate the hydraulic conductivity of the GCLs under different field exposure conditions. The hydraulic conductivities of the NaB and B-P GCLs gradually increased during four wet–dry cycles. However, the hydraulic conductivity of the B-P GCL (K = 2.3 × 10-12 m/s) was lower than that of the NaB GCL (K = 6.3 × 10-11 m/s) by two orders of magnitude after four permeation–drying cycles. In addition, the hydraulic conductivity of the B-P GCL was lower (K = 5.8 × 10-12 m/s) than that of the NaB GCL (K = 7.8 × 10-10 m/s) by two orders of magnitude after four saturation–drying cycles. The results suggest that B-P GCLs can enhance the effectiveness of landfill cover systems compared to Na-B GCLs in managing conditions during wet and dry seasons.
Simulation of microbial transport and petroleum hydrocarbon compound biodegradation in a fracture–matrix coupled system
Authors: Li J , Feng S J , Zheng Q T
Published: May 2024

In-situ bioremediation technology is considered an ideal and environment-friendly approach for the largescale treatment of petroleum-contaminated soil. Most earlier studies on bioremediation have focused on the biostimulation techniques, which can enhance the biodegradation capabilities of indigenous bacteria, rather than on bioaugmentation involving the introduction of exogenous microorganisms. Additionally, contaminated soil sites typically contain both natural and artificial fractures. These fractures serve as preferential transport pathways, complicating the transport of bacteria and related solutes. This study proposes a mathematical model to simulate the transport of exogenous bacteria and electron acceptors during the degradation of petroleum hydrocarbon pollutants in a fractured aquifer system. The model incorporates the processes such as microbial convection, diffusion, adsorption, chemotaxis, growth, death, and microbial metabolic reactions. Simulation results demonstrate that considering microbial transport significantly affects the prediction of contaminant degradation, particularly with regard to the transport of electron acceptors. The growth rate of bacteria has an evident effect on the efficiency of contaminant remediation, and microbial chemotaxis can significantly enhance the degradation efficiency. The proposed mathematical model serves as a valuable tool for assessing the effectiveness of bioaugmentation strategies and can aid in the design and optimization of remediation efforts for contaminated and fractured aquifers.
Effect of fracture distribution on extraction efficiency in low-permeability NAPL-contaminated formations
Authors: Niu Jiuge , Feng Shijin , Zheng Qiteng , Yang Chunbaixue
Published: May 2024

Hydraulic fracturing offers an effective solution to the challenge of remediating low-permeability contaminated formations by improving substance transport rates. In this study, COMSOL Multiphysics, a large-scale multi-physics coupled simulation software, was employed to simulate enhanced extraction and remediation of low permeability non-aqueous phase liquid (NAPL)-contaminated formations using hydraulic fractures. The results obtained indicate that fracturing and enhanced extraction can effectively improve the NAPL removal rate. The NAPL removal rate increased with increasing depth of the extraction well screens, fracture length, and fracture spacing. Through a coupling analysis of multiple factors and working conditions, the extraction well screens are suggested to be buried within the lower one-third of the low-permeability contaminated formation, and the length of a single fracture should be within 50%–80% of the extraction radius. When the distance between the two fractures was greater than 1.75 m, the enhancement effect of the fracture length was further promoted. Consequently, a reasonable configuration of fracture length, quantity, and spacing can effectively broaden the influence radius of extraction wells.
Physical and chemical properties of aluminum tailings mud modified by metal ions
Authors: Deng X , Ma B , Du B
Published: May 2024

Aluminum tailings mud, a type of waste generated by bauxite washing during alumina production, is harmful. Owing to the isomorphism substitution of iron-aluminum symbiotic minerals, a large number of metal ions inevitably exist in the slurry, which causes the suspension to maintain dispersion and hinders the drainage of aluminum tailings mud. This study examined the effects of the pH and commonly associated metal ions, such as K+ and Fe3+, on the sedimentation characteristics of aluminum tailings mud. Zeta potential analyzer, X-ray fluorescence spectrum analysis, and electron scanning microscopy were used to study the effects of common metal ions in the tailings slurry on the sedimentation characteristics of aluminum tailings mud. The results showed that the sedimentation effect of the tailings slurry was superior after adding Fe3+ compared with K+. The mechanism analysis shows that at a certain pH range, the addition of metal ions can compress the thickness of the electric double layer on the surface. The high-valence ions (Fe3+) will have more electric double layer compression than monovalent ions (Na+), which is more conducive to the agglomeration of aluminum tailing mud particles. This conclusion provides guidance for efficient drainage of aluminum tailings mud.
Hydro-mechanical analysis of slope stability using anisotropic constitutive model
Authors: Song Fei , Duan Guanghui , Wang Huaning , Rodriguez-Dono Alfonso , Wei Yimiao
Published: May 2024

This study introduces a novel and robust numerical approach to analyzing rainfall-induced landslide hazards, incorporating coupled hydro-mechanical behavior, anisotropic properties of unsaturated geomaterials, and soil–atmosphere interaction. The advanced hyperbolic Mohr-Coulomb model with anisotropy is adopted for mechanical responses, while generalized Darcy’s law is employed for hydraulic behaviors. This approach allows for anisotropic specification of hydromechanical properties like stiffness, strength, and intrinsic permeability. Atmospheric boundary conditions enable analysis of soil–atmosphere interactions, encompassing infiltration and runoff during extreme rainfall. Parametric analyses were conducted to evaluate slope safety factors under various anisotropic angles.
Numerical analysis of stress and deformation characteristics of compressed air energy storage chambers developed from a modified coal mine tunnel
Authors: Chen Yanxi , Zhao Cheng , Qian Yuan , Sun Zeyuan , Xing Jinquan , Zhang Boyi
Published: May 2024

The use of abandoned coal mine tunnels as underground compressed air energy storage (CAES) facilities has garnered significant attention given that it effectively repurposes unused underground space and enhances the efficiency of renewable energy utilization. However, existing coal mine tunnels, without optimization and retrofitting, may not meet the stability requirements of compressed air energy storage repositories. Sectional transformation is a retrofitting method with excellent optimization effects. In this study, numerical simulation based on Midas software was employed to create a three-dimensional model of straight-wall arched mine tunnels. The stress and displacement deformation of the tunnel sections were simulated under internal pressure of 10 MPa, and scenarios with no modification and circular-section backfilling were compared. The outcomes of the study are (1) For deeply buried soft rock mines, the existing structure without modification may not meet the stability requirements of compressed air storage facility due to low rock strength. (2) In the unmodified scenario, stress concentration effects and excessive floor tensile stress occur near the tunnel closure. (3) Backfilling straight-wall arched tunnels into circular shapes effectively reduces stress and displacement along the tunnel walls, preventing stress concentration near the tunnel closure. This study provides a retrofitting approach for repurposing abandoned mines into compressed air energy storage facilities, providing guidance for future projects facing complex geological conditions.
Numerical modelling for optimizing shoring wall performance in deep urban excavations
Authors: Yasrebi Shahab , Zolqadr Emad
Published: May 2024

Soil nailing and anchoring are effective methods for reinforcing the soil in situ, providing internal support that enables the earth to sustain itself during and after excavation. To ensure optimal performance, it is essential to monitor the behavior of the soil nail walls throughout the excavation and after completion, so that the SOE system design can be improved. This study presents a comprehensive survey of the design and performance of soil nail walls in deep urban excavations at depths ranging from 19.5 to 29.3 m. After construction, the lateral deformations of the soil nail walls varied significantly from 69% to 222% of the initial deformations observed immediately after completion. Numerical analyses were used in the design process to accurately predict the wall performance and determine the design characteristics to identify appropriate design parameters and predict the wall behavior. Several numerical models using different modelling approaches are examined, and the results demonstrated that post-construction deformation rates can vary between walls based on factors such as the soil nail and anchor system design and geotechnical conditions at the excavation site. A thorough understanding of these variables is crucial for optimizing the performance of SOE systems in deep urban excavations.
Mechanical mechanism of soft soil foundation improved by geosynthetic-reinforced pile-supported technology based on field experiment
Authors: Liu H Y , Qian J S , Ling J M , Wang J H , Lin H Y
Published: May 2024

Geosynthetic-reinforced pile-supported (GRPS) technology is an effective method for improving soft soil foundations. Conducting field tests is crucial for accurately assessing the mechanical behavior of GRPS technology. Based on the fourth expansion project at Pudong Airport, field tests were conducted to investigate the effects of GRPS technology on soft-foundation treatment. Specifically, the tests examined the changes in the pile and soil settlement, pore water pressure, and pile and soil stress. The results showed that the settlement of the GRPS foundation mainly occurred during the loading period, accounting for approximately 65% of the total foundation settlement. Increasing the pile modulus and reducing the pile spacing decreased the total foundation settlement. The filling load was mainly transferred to the piles through the soil arching effect, resulting in a large excess pore water pressure in the soil layer near the pile tip. In addition, when the filling height was low, the load transfer relied predominantly on the tensile membrane effect of the geogrid, which was more pronounced near the piles. However, as the filling height increased, the soil arching effect surpassed the tensile membrane effect and played a key role in load transfer.
Performance of incineration bottom ash amended marine soft clay stabilized by cement in seawater
Authors: Sun Xinlei , Zhi Yeon Ting Matthew , Yi Yaolin
Published: May 2024

Incineration serves as an effective waste management method driven by its ability to reduce mass and volume of municipal solid waste. However, this process generates incineration bottom ash (IBA), which is commonly disposed of in landfills in many countries, especially when dealing with fine IBA. To address this issue, recycling fine IBA for soft marine clay (MC) stabilization is a sustainable option compared to landfilling. Previous studies revealed that aggregate-like and weak hydration properties of fine IBA may increase the strength and decrease compressibility of MC. Nevertheless, when using IBA-MC in land reclamation or coastal protection, the performance may deteriorate, particularly in the presence of seawater. Therefore, this study employed chemical stabilization method combined with ordinary Portland cement (OPC), to solidify/stabilize IBA-MC (OPC-IBA-MC). The aim was to improve the performance of IBA-MC in seawater. The appearance, water content, strength, mineralogy, and microstructure of IBA-MC and OPC-IBA-MC soaked in seawater were investigated. The results showed that the strength of OPC-IBA-MC (4075 kPa) cured in air for three months was significantly higher than that of IBA-MC (983 kPa). Nevertheless, after soaking in seawater, OPC-IBA-MC was dismantled, rendering its strength untestable. The mineralogy and microstructure of OPC-IBA-MC revealed that the formation and growth of ettringite caused instability in OPC-IBA-MC in seawater.
Model tests on red clay foundation reinforced by coir geotextiles
Authors: Li Liang-yong , Chen Jia-cheng , Yang Lin , Zhang Qing-song , Cao Wei-qiang , Cheng Yan-wen
Published: May 2024

Geosynthetics slowly degrade in soil, which may cause environmental problems in the future. Natural coir fibers are green, environmental-friendly, renewable, and have broad application prospects. Coir geotextiles were used to reinforce red clay foundations. The effects of the reinforcement length and depth, first-layer reinforcement depth, and reinforcement-layer spacing on the deformation and bearing capacity of the foundations were studied via load tests. The distribution law of the earth pressure along the depth was also analyzed. The results showed that when the reinforcement length was 1B, the anchorage length of the reinforcement was insufficient, and the reinforcement effect was unclear. As the reinforcement length increased, the anchoring length of the reinforcement increased, and bearing capacity of the foundation significantly increased. However, when the reinforcement length exceeded 3B, the force of the anchorage segment was fully exerted, slightly increasing the bearing capacity of the foundation. The optimal reinforcement length was determined as 3B. The bearing capacity of the foundation increased as the reinforcement depth increased and the buried depth of the first reinforcement layer and spacing of the reinforcement decreased. The optimal reinforcement depth, buried depth of the first reinforcement layer, and reinforcement spacing were 2B, 0.25B, and 0.25B, respectively.
Basic Mechanical Properties of Unit Cell-based Stiffened Deep Mixed Column
Authors: Zhang Yusen , Xu Yan , Li Guangyao , Ye Guanbao , Zhang Zhen
Published: May 2024

As a composite column, stiffened deep mixed (SDM) column is formed by inserting a precast concrete core pile into the center of a deep mixed (DM) column. When SDM columns are used to support embankments over soft soil, they would be failed by shearing, compression, tension, and bending. This study conducted a series of laboratory tests to investigate the basic mechanical properties of a unit cell of SDM column, including uniaxial compression, direct shear and tension tests. The results reveal that the impact on improvement was minimal at a core ratio of 9.8%, subsequently followed by a substantial rise. In addition, the radial compression strength reached the maximum at a core ratio of 25%, and the shear strength approached to a constant value when the core element ratio exceeded 25%. Increasing the area ratio resulted in the change of failure modes of core element. Finally, a relationship among the different strength was discussed.
Soil-cement columns for high-rise buildings: design–testing–construction–monitoring: A case study of green solution in Vietnam
Authors: Dao D H , Ngoc P V , Nam H P , Puppalla A , Han J
Published: May 2024

Soil cement columns (SCCs) are commonly used to reinforce soft ground to support roads and railway embankments, or to withstand horizontal pressure for deep excavations. This study presents another application of SCCs as load-bearing foundations for high-rise building projects. SCCs with a diameter of 800 mm, length of 10 m, cement content of 350 kg/m3, and an unconfined compressive strength (UCS) of 3.6 MPa were applied. In this study, five single columns and one group constituting two columns were constructed, and core drilling and axial static load tests were conducted. The test results indicated that the SCC could achieve a load of 1,650 kN for a single pile and 3,300 kN for the group constituting two columns. In total, 1,123 columns were designed and constructed for this project. Compared with conventional reinforced concrete pile methods, a project using SCC could save 30 construction days and 20% of the total cost. Moreover, SCC can be considered a green and environmentally friendly foundation solution because it does not use concrete or steel materials and does not produce waste soil.
Building responses to soil removal, dewatering, and artificial recharge during deep excavation in water-rich sandy strata
Authors: Liu J C , Hu S L , Tan Y , Chao H
Published: May 2024

In water-rich sandy strata, deep excavations necessitate dewatering within the excavation site, leading to significant groundwater drawdowns and surface subsidence behind walls, which can result in severe damage to adjacent buildings. Nonetheless, the individual impacts of soil removal and dewatering in such permeable sandy formations on building responses remain ambiguous,with scant reported protective experience in literature. This study introduces a validated three-dimensional fluid-solid coupling finite-element model to simulate the construction of an 18-19.8 m deep subway station in Nantong, China. Artificial recharge was applied to mitigate adverse effects on nearby buildings caused by drainage. The investigation explores the separate effects of soil removal, dewatering, and water recharging on the settlements of buildings with three different foundations (natural, raft, and piled footings). Additionally, the influence of post-recharging groundwater levels on building responses was scrutinized. The present findings indicate that discharging confined aquifers significantly contributes to building settlements, while artificial recharge can substantially reverse the deformations in buildings, especially those with natural and raft foundations. As excavation depth and the bearing capacity of the building foundation increase, the relative impact of soil removal on building settlements grows, whereas the influence of dewatering diminishes. Compared to enhancing foundation-bearing capacity, artificial recharge emerges as a more cost-effective strategy to safeguard pre-existing buildings near deep excavations in water-rich sandy strata, provided the post-recharging groundwater levels achieve a certain threshold.
A case study of the response of support structure and stratum deformation caused by deep foundation pit excavation in soft area
Authors: Zhu Q X , Qin H L , Song B W , Wang L , Lü X L
Published: May 2024

Investigating the spatial distribution and evolution patterns of deformations during foundation pit excavation is crucial for safeguarding the surrounding environment. This study focuses on a deep excavation case in Nanjing and discusses the strata deformation and the response of the retaining structure through the excavation phase, informed by on-site monitoring data. A three-dimensional finite element model of the excavation was developed, with comparisons between predicted values and on-site deformation monitoring data underscoring the accuracy of the numerical simulation results. This analysis delved into the deformation spatial distribution within the retaining structure and ground surface settlement throughout the excavation. Moreover, the three-dimensional deformation patterns of the diaphragm wall at various excavation depths were scrutinized, mapping the evolution pattern and spatial distribution of ground surface settlement around the foundation pit across different excavation stages. The findings reveal a pronounced spatial effect in both the diaphragm wall deformation and ground movements behind the wall, with the greatest deformation manifesting near the symmetric plane of the excavation center and markedly less deformation near the excavation corners. Furthermore, the deformation scope broadens with increasing excavation depth. These research outcomes aim to furnish a substantive reference for practical engineering implementations.
Geomechanical impact on subway tunnels beneath open-cut tunnel excavation pits under long-distance overlapping conditions
Authors: Zhou B , Zhao C
Published: May 2024

In urban locales characterized by high population density, tunneling activities frequently entail extensive spatial overlap with pre-existing subway infrastructure. Thus, the geomechanical impact of open-cut excavation pits on subjacent subway tunnels is highly significant. Drawing upon the empirical data from the Tunnel Project of Erqi Square in Zhengzhou City, China, a suite of three-dimensional numerical models was formulated to scrutinize the interplay of three salient variables—excavation depth, excavation width, and vertical clearance between subway tunnels and excavation pit floors—on subway tunnel deformation. The findings elucidate that: (1) the predominant deformation mode of subway tunnels is vertical uplift, with the maximum vertical displacement exhibiting an almost linear correlation with both excavation depth and vertical clearance, yet diminishing in rate with incremental excavation width; (2) among the variables, excavation depth exerts the most pronounced impact on vertical deformation, followed by vertical clearance, whereas excavation width plays a comparatively marginal role; (3) Predictive model for estimating maximum vertical displacement in the silty clay strata of Zhengzhou City was derived through multiple linear regression analysis, and its efficacy was corroborated through juxtaposition with extant measured data, thereby validating its applicability for preliminary prediction of the maximum vertical displacement of subway tunnels in long-distance excavation above the subway tunnels.
Prediction of the undrained base heave and post uplift in braced excavation of a typical subway station in thick soft clay
Authors: Gao Y B , Li Y J
Published: May 2024

Construction of a typical subway station usually involves a narrow long excavation with a width of approximately 20 m. An undrained base heave is a common problem in deep excavation areas with soft clay, which may induce considerable post uplift and damage the safety of the retaining system. Post uplift involves complex interactions between soil, pile post foundation, and supported struts, and an accurate prediction of post uplift is challenging. This paper aimed to establish a practical method for predicting the base heave and post uplift in the construction of typical subway stations in areas with thick soft clay. Series soil–water coupled finite element method (FEM) analysis was conducted to investigate the characteristics of the base heave with different soil properties and wall stiffnesses. The results showed that the calculated base heave can be fitted by a normalized function, regardless of large variations in soil properties and wall design parameters. The normalized function was then applied to a soil–post–strut interaction analysis model to predict the post uplift at different excavation depths. The application of the proposed method to a real subway station project showed that the predicted results were in good agreement with the field observations.
Study on new micro-pile structure for reinforcement of shallow foundation
Authors: ma Yibao , Li Zixi , Zhang Ga , Wang Gang
Published: May 2024

Micropiles are widely adopted for reinforcing shallow foundations. A new type of topping micropile structure was proposed in this study. A certain length of the expansion section was added to the upper part of the micropile, which not only retained the cylindrical section of the micropile but also enhanced the limiting effect on the lateral displacement of the soil near the shallow foundation. A comparative centrifugal model test of the new micropile and an ordinary micropile was conducted by applying a vertical load on the foundation. Under the test conditions in this study, the bearing capacity of the new micropile reinforcement foundation increased by approximately 50% compared to that of an ordinary micropile.The new miniature piles significantly reduced the settlement of the foundation. The reinforcement effect of the new micropiles on a shallow foundation was more pronounced than that of an ordinary pile given that the new micropiles possessed numerous limitations on the lateral deformation of the soil base under the shallow foundation.
Performance of unequal piled raft under vertical loading in cohesionless medium
Authors: Kumar Malviya Dinesh , Samanta Manojit
Published: May 2024

The performance of piled rafts with unequal pile lengths in cohesionless soil under vertical loading was investigated in the present study through experimental and numerical analysis. A pattern function is used to define the pile length arrangement. The motivation for considering such a function is to ensure that the varying pile lengths follow a suitable geometric pattern, and it does not obstruct the construction practice in field applications. The piles at different locations within the raft were equipped with strain gauges to observe the strain distribution along their lengths during the static load test. Load sharing was evaluated by placing an earth pressure cell beneath the raft. A three-dimensional finite element analysis was used to simulate the experimental results aimed at assessing the load settlement and load-sharing responses. A comparison was conducted to verify the reliability of the tests. Subsequently, a detailed parametric study was conducted in accordance with different pattern functions, pile spacing, and pile locations in the piled rafts. The load settlement, load sharing, and bending moment of the raft were evaluated. An understanding of the pile behavior at different locations within the group will be helpful in selecting the suitable pile geometry during actual construction in the field. A foundation designed by considering the optimized pile length will be helpful in developing a more economical and resilient foundation system.
Numerical simulation of the uplift bearing behavior of pile foundations for transmission towers in expansive soil area
Authors: Zhong Yishun , Lü Xilin
Published: May 2024

Piles are commonly used as foundations for power transmission towers located in expansive soil areas. The strength of expansive soil is highly sensitive to the changing water content, which complicates the pile–soil interaction. In this study, a 3D elastoplastic finite element analysis of a typical pile foundation for a transmission tower in an expansive soil area was conducted to understand the effect of water content in expansive soil on the uplift bearing capacity of the pile foundation. The results that the failure mode of the pile foundation is almost unaffected by the water content. Shear failure was observed at the pile–soil interface, and, when the pile was pulled out, it lost its uplift bearing capacity. With the increasing water content of the soil, the ultimate uplift bearing capacity of the pile foundation exhibited a significant decreasing trend, whereas the displacement of soil around the pile became remarkable. The distribution of pile axial force and lateral frictional resistance during the uplift process was also evaluated. The pile axial force decreased gradually and at a higher rate with increasing depth. Once the pile reached the ultimate uplift bearing state, the pile lateral friction increased almost linearly with depth.
Bearing characteristics of a model piled raft foundation in unsaturated soil subjected to variations in the groundwater level
Authors: Xiong X. , Matsumoto T.
Published: May 2024

The bearing characteristics of a piled raft foundation (PRF) in saturated or dry soil ground have been investigated in previous studies. However, soils near the ground surface are generally in an unsaturated state. Matric suction occurs in unsaturated soils and influences the mechanical properties of soil. For more reasonable designs of PRFs, it is undoubtedly necessary to study the bearing characteristics of PRFs in unsaturated soil. In this study, model tests were conducted to investigate the bearing characteristics of a PRF in unsaturated soil subjected to variations in the groundwater level. The experimental results showed that, when the groundwater level was increased and the suction decreased, the load carried by the raft increased under dead load, leading to a significant settlement of the model PRF.
CPTU-based permeability evaluation of clays
Authors: Feng Hualei , Cai Guojun , Ouyang Zhongkun , He Huan , Mayne Paul W.
Published: May 2024

The piezocone penetration test (CPTU) is an efficient in-situ testing method for delineating subsurface stratigraphy and interpreting geoparameters continuously with depth. However, owing to the regional sensitivity and geological diversity, the applicability of CPTU-based geotechnical parameter evaluation methods is limited when applied to specific sites. This requires further scrutiny considering the different geological histories and local soil conditions. In this study, a database that included a collection of CPTU test sites in Jiangsu Province, China, was compiled containing high-quality sampling and laboratory testing performed to characterize the permeability of clay soils. Several published CPTU correlations for determining soil permeability were summarized and compared with laboratory-measured soil permeability as a benchmark reference. The evaluation results indicated that the I
c-based correlations can provide a reasonably good determination of the permeability for the investigated soils with root mean squared error of 0.89 and mean absolute error of 0.77. Finally, a modified approach was presented to evaluate the permeability coefficient of Jiangsu clay soils, which was calibrated using two additional case studies.
Field testing performance of prebored precast piles with enlarged base in soft ground
Authors: Wang WeiDong , Yang Yu , Wu Jiangbin , Qian Jiangu
Published: May 2024

Prebored precast piles with an enlarged base (PPEB piles) are constructed using an innovative and environmentally sustainable method, which notably reduces noise, soil squeezing, and mud discharge. Although PPEB piles have been widely applied in many cities in China, their bearing performance, including side friction and end resistances, on soft ground remains relatively unelucidated. This paper focuses on case studies of vertical-bearing PPEB piles based on a group of vertical static load field tests in Shanghai. The following conclusions are drawn: (1) Compared with traditional hammered-driven piles, PPEB piles exhibit better construction quality and load-bearing performance, as well as a relatively slow increment of settlement even under ultimate loading. (2) The resistance of the enlarged base section of the PPEB pile was approximately 16.3% of the total resistance under ultimate loading. (3) Compared with the values proposed in the Shanghai Foundation Design Code, the side friction resistance of the PPEB pile in deep silty sand (34.5–39 m) exhibited a considerable increase of approximately 156%. Additionally, the side friction in the soft ground was close to the values proposed in code. The case studies provide practical guidelines for the application of PPEB piles in soft ground.
A Comprehensive Review of the Evaluation and Application of Engineering Properties of Expansive Soil Based on Piezocone Penetration Test (CPTU)
Authors: Cai G J , Song D H , Liu L L , Liu X Y , Tian H L
Published: May 2024

Expansive soil presents several challenges in civil and geotechnical engineering because of its distinctive physical and mechanical properties, including considerable volumetric fluctuations, non-linear stress–strain behaviour, and high permeability. Owing to soil disturbances and sample size limitations during sampling, important parameters such as the expansive soil expansion force, compressive strength, and shear strength obtained through indoor experiments often cannot accurately reflect the values in situ. In this regard, in situ piezocone penetration testing has the advantages of small disturbances and high efficiency and has been widely used in subways, bridges, highways, and other engineering projects. This paper comprehensively summarizes the research progress of in situ testing technology in the evaluation and application of engineering properties of expansive soils in China and internationally. First, a detailed analysis of the basic theories and physical mechanisms of various in situ testing methods is provided, focusing on their applicability and accuracy in expansive soils. Second, examples of the application of in situ testing technology in expansive soil engineering are summarized. Finally, predictive models and methods based on in situ testing data, especially those that introduce cutting-edge models such as machine learning and advanced data analysis techniques, are discussed.
Prediction of the axial strain development curve of soft clay under dynamic triaxial conditions based on LSTM
Authors: Xiao Siqi , Wu Hao , Zhou Jie
Published: May 2024

The dynamic triaxial test results of soft clay show that a long-term cyclic traffic load lead to significant deformation of soft clay. Considering that the dynamic triaxial test data of soft clay under cyclic loading have apparent time series characteristics, the long short-term memory (LSTM) model can be used to predict the deformation law of soft clay. Through a dynamic triaxial test of Shanghai soft clay, time series data, such as axial stress, pore water pressure, and axial strain were obtained to establish the sample data of the LSTM model. The LSTM model is then used to predict the axial strain development curve. The results showed that the LSTM model had a good fitting precision for the sample data under different dynamic stresses and frequencies, and its accuracy was above 97% in all conditions. The prediction results can reproduce the fluctuation law of the axial strain under cyclic loads and can be used to study elastic and plastic strains. The research results can provide technical support for disaster prevention and control in soft clay.
Physics-informed machine learning of multi-source monitoring data sparsely measured within a 2D vertical cross-section
Authors: Tian Hua-Ming , Wang Yu
Published: May 2024

Conventional machine learning (ML) methods suffer from several limitations, e.g., overreliance on large training datasets and poor performance in extrapolating beyond observations. Geotechnical monitoring data at specific sites are multi-sourced (e.g., settlement and horizontal displacement data). Moreover, each source of monitoring data may vary temporally and be sparsely measured, e.g., within a two-dimensional (2D) geological cross-section. Thus, effectively learning multi-source and limited monitoring data is difficult using existing ML methods. To address this challenge, this study proposes a physics-informed ML method combining geotechnical numerical models (e.g., the finite element model (FEM)) with sparse dictionary learning (SDL) methods. It uses a range of probable numerical model results corresponding to multiple, temporally varying responses in a 2D spatial range to construct a “dictionary” in SDL and employs multi-source and limited monitoring data to identify a few “atoms” from the constructed dictionary to improve model predictions. An engineering project for embankment construction is used to illustrate the proposed approach. Our results indicate that the proposed approach effectively integrates FEM results with multi-source and sparsely measured monitoring data and improves the predictions of multiple spatio-temporally varying geotechnical responses significantly, particularly those at subsequent time steps and unmonitored spatial locations within a 2D vertical cross-section.
Semantic segmentation of large-scale segmental lining point clouds using 3D deep learning
Authors: Lin Wei , Sheil Brian , Xie Xiongyao , Zhang Yangbin , Cao Yuyang
Published: May 2024

It is highly challenging to comprehensively measure the deformations of large-scale tunnel structures because of the numerous individual segments of tunnel linings. Laser scanning and 3D deep learning (DL) can provide abundant geometric data and the ability to interpret such data automatically. To fill the gap in applying 3D DL to the segment-wise segmentation of large-scale tunnel point clouds, a new 3D dataset and an optimized DL network are presented in this paper. The point cloud dataset was manually annotated by labeling every individual segment and element. Subsequently, a 3D DL network capable of handling large-scale point clouds (approximately 106 points) was developed to perform the data experiments. The influences of network parameters, namely, the number of neighbor points, layer number, down-sampling ratio, and channel number, were investigated in the data experiments. The results indicate that the number of neighboring points and channel number have a notable influence on the segmentation performance, with the best mean interaction over union reaching 85.5%. This study provides preliminary insights into the 3D DL network design for large-scale tunnel point clouds.
A method to construct a main hole structural plane model based on advanced parallel adit geological body
Authors: Zhang Shuainan , Wu Wei , Zhang Min , Huang Yong , Fu Wei
Published: May 2024

The advanced parallel adit of tunnel refers to the adit parallel to the direction of the main hole. Generally it is spaced tens of meters from the axis of the positive hole. During the tunnel construction, the parallel adit is driven before the main hole. Main function of it is to provide geological reference for the subsequent excavation of the main hole. At the same time, it can also help improve the long-term construction and operation and maintenance efficiency of the main tunnel. In terms of providing geological prediction information for the main tunnel, the surrounding rock information disclosed in the advanced parallel adit excavation is mainly used for surrounding rock classification and geological sketch, so as to qualitative analysis the possible geological conditions when the positive tunnel is excavated near the distance where the advanced parallel adit is located. However, the above methods cannot accurately and quantitatively analysis the geological conditions that the main tunnel will face. The lack of research on the correlation between the main tunnel and the advanced parallel adit geological conditions results in the waste of the key factor of the horizontal geological information.In this paper, the improved DBSCAN clustering algorithm is used to group the dominant structural planes according to the attitude of rock and other information. Some non-primary structural planes are screened out. The average distance between the same group of structural planes is calculated according to the average attitude of the dominant structural plane. The structural planes that are close enough are fused. Then, the axial and radial projection was carried out to form a larger range of surrounding rock fracture models. When the main tunnel is excavated to the relevant area, the situation of the surrounding rock in front can be predicted according to the model, so that the countermeasures can be made in advance. The method in this paper is applied to a tunnel project with bidirectional single line and advanced parallel adit. The prediction results after tunnel excavated show that the method in this paper is reasonable and effective.