bluuebunny/crossref_metadata_2025 huggingface dataset:
Farming system archetypes help explain the uptake of agri-environment practices in Europe
Authors: Václavík Tomáš , Beckmann Michael , Bednář Marek , Brdar Sanja , Breckenridge George , Cord Anna F , Domingo-Marimon Cristina , Gosal Arjan , Langerwisch Fanny , Paulus Anne , Roilo Stephanie , Šarapatka Bořivoj , Ziv Guy , Čejka Tomáš
Published: May 2024

The adoption of agri-environment practices (AEPs) is crucial for safeguarding the long-term sustainability of ecosystem services within European agricultural landscapes. However, the tailoring of agri-environment policies to the unique characteristics of farming systems is a challenging task, often neglecting local farm parameters or requiring extensive farm survey data. Here, we develop a simplified typology of farming system archetypes (FSAs), using field-level data on farms’ economic size and specialisation derived from the Integrated Administration and Control System in three case studies in Germany, Czechia and the United Kingdom. Our typology identifies groups of farms that are assumed to react similarly to agricultural policy measures, bridging the gap between efforts to understand individual farm behaviour and broad agri-environmental typologies. We assess the usefulness of our approach by quantifying the spatial association of identified archetypes of farming systems with ecologically relevant AEPs (cover crops, fallow, organic farming, grassland maintenance, vegetation buffers, conversion of cropland to grassland and forest) to understand the rates of AEP adoption by different types of farms. Our results show that of the 20 archetypes, economically large farms specialised in general cropping dominate the agricultural land in all case studies, covering 56% to 85% of the total agricultural area. Despite regional differences, we found consistent trends in AEP adoption across diverse contexts. Economically large farms and those specialising in grazing livestock were more likely to adopt AEPs, with economically larger farms demonstrating a proclivity for a wider range of measures. In contrast, economically smaller farms usually focused on a narrower spectrum of AEPs and, together with farms with an economic value <2 000 EUR, accounted for 70% of all farms with no AEP uptake. These insights indicate the potential of the FSA typology as a framework to infer key patterns of AEP adoption, thus providing relevant information to policy-makers for more direct identification of policy target groups and ultimately for developing more tailored agri-environment policies.
An improved hypoplastic model incorporating intergranular strain for overconsolidated clay
Authors: Zhou Yong , Shi Zhenhao , Qian Jiangu
Published: May 2024

Hypoplastic constitutive models are able to describe overconsolidated behaviors of clay with a single nonlinear tensor function using a set of parameters. For instance, an advanced hypoplastic model by Wang and Wu (2020) has successfully reproduced overconsolidated history by incorporating a structure tensor. To simulate the recent stress history effects and the stiffness variations at small strains of clay, the intergranular strain tensor is introduced by Niemunis and Herle (1997) to reproduce stress-path dependent stiffness of clay. The improved hypoplastic model is examined against experiments on overconsolidated Chicago clay. It is evidently concluded that the improved model is capable of replicating stress-path dependency on the small-strain behavior of overconsolidated clay.
A novel CFD-DEM coupling method with moving boundary for simulating one-dimensional consolidation test
Authors: He J H , Li M G , Chen J J , Xiao X
Published: May 2024

The conventional CFD-DEM coupling method fails to dynamically modify the position of the drainage boundary during the simulation of one-dimensional consolidation tests (1d CT), resulting in inaccuracies in the numerical results. In this study, a novel CFD-DEM coupling method with moving boundaries is proposed to simulate 1d CT where the fluid boundary adaption and internal mesh reconstruction are implemented with reference to the real-time morphology of the consolidation specimen. Additionally, the convective terms in Navier-Stokes equations are modified to account for the moving drainage boundary and the equation of state (EOS) is introduced to consider fluid compressibility. A series of 1d CTs based on the traditional fixed boundary and the moving boundary are subsequently conducted for comparison. Moreover, the influence of fluid compressibility and mesh coarseness on the consolidation characteristics is briefly discussed. The proposed method is verified to serve well in revealing the underlying microscopic mechanism of the Mandel-Cryer effect and complementing the traditional consolidation theories.
Statistical correlation between HSS model parameters and the method of parameter valuation
Authors: Zhang Liqin , Zhou Xiaowen , Zhu Jianfeng
Published: May 2024

Small-strain hardened soil model is suitable for fine numerical simulation because it considers the compression and shear hardening of soil. However, setting the parameters of the model is difficult. Based on the analysis of the physical meaning of each parameter and the statistical analysis of parameter values of the small strain model reported by researchers, the empirical relationship between several parameters is obtained in this study. Accordingly, valuation methods of parameters are discussed.
Experimental study on the influence of principal stress axes rotation on sand mechanical behavior and non-coaxiality effects
Authors: Zhu Wenxuan , Ye Guanlin , Lin Nan
Published: May 2024

The soil around the foundations of offshore engineering experienced the principal stress axes rotation caused by the wave loadings. To investigate the influence of the principal stress axes rotation on the soil stress-strain relationship, a series of pure principal stress axes rotation tests under drained/undrained conditions were carried out with a hollow cylinder apparatus. The undrained test results show that the deviatoric stress, relative density, and starting point of rotation affect the mechanical properties of sand. Through the analysis of pore water pressure accumulation in the 1st cycle, it was observed that more pore pressure accumulates in Quadrants II and III, while relatively less accumulates in Quadrants I and IV. Under drained and undrained conditions, the non-coaxial behavior of the soil differs. The non-coaxiality can be significantly observed in the drained test, and the direction of strain increment tends to the stress increment direction when the cycle number increases.
Deformation and strength degradation mechanism of weathered mudstone soil during dry-wet process based on a developed DEM approach
Authors: Zhang H , Zhao E P , Che D L
Published: May 2024

The soils suffer dry-wet cycles in nature and engineering due to the change of temperature, rainfall and the fluctuation of the groundwater level. The shrinkage-swelling deformation and mechanical properties evolve with the variations of moisture content during a dry-wet process was investigated by laboratory dry-wet cycle tests of a weathered mudstone soil. A DEM approach was developed for simulating the mechanical behaviors during the dry-wet process of the studied soil, considering the shrinkage-swelling deformation by adjusting the shrinkage or swelling ratio of the clay aggregate particles. The irreversible shrinkage-swelling deformation mechanism and the strength degradation mechanism were revealed. The results showed the developed DEM simulations can represent the deformation and the mechanical properties of soils during the dry-wet process. The shrinkage rate of soil decreases with the moisture content from saturation value to 5%, due to the reduction of the shrinkage potence of the clay aggregates. The irreversible shrinkage deformation of soils during a dry-wet process is because the limit swell potence of clay aggregate particles during the wetting process, leading to the swell during the wetting less than the shrinkage during the drying process. The strength degradation was divided into reversible portion mainly affect by the moisture content, and the irreversible portion affected by the meso-crack evolution during the dry-wet process. The large increase of meso-crack number during the drying leads to the rapid reduction of irreversible soil strength, while the decrease of porosity leads the increase of particle contacts and healing of the irreversible soil strength.
Micromechanics of multiphase geomaterials based on micro-CT image analysis: unsaturated soil, vegetated soil, and bio-cementation
Authors: Wang Jipeng , Luan Jiyuan , Li Mengchen , Sha Junfeng , Qi Meng , Dadda Abdelali , Viggiani Gioacchino
Published: May 2024

Under the influence of climate change, extreme weather events such as rainstorms may induce fluctuations in soil water content above the groundwater level, thereby causing geological disasters (e.g., landslides). To mitigate these hazards, green and low-carbon engineering measures such as vegetation reinforcement and bio-cementation are proposed. This study investigates the micromechanical properties of multiphase geomaterials—unsaturated soil, vegetation-reinforced sand, and bio-cemented sand—utilizing high-resolution computed tomography (CT) scanning technology and associated image analysis techniques. The findings are presented as follows: (1) a 4D examination of the macroscopic and microscopic behaviors of unsaturated granular materials under triaxial loading conditions was conducted using self-designed in situ CT scanning equipment. (2) Triaxial loading alters the distribution of phase interfacial surfaces in unsaturated soil, affecting its overall strength. This loading also increases the anisotropy of the solid skeleton and suction stress. (3) The global saturation of the root–soil complex diminishes with root growth, with pore distribution significantly influencing local saturation. (4) In the unsaturated MICP process, low-saturation conditions are preferable for effective cementation, although the saturation levels should be restricted to 20%. After calcification, the particle contact coordination number increases, maintaining the isotropy in the contact between the soil particles.
Research on the density of underwater sand and gravel fillings based on geotechnical centrifugal tests
Authors: Li Bo , Wei Songtao , Shen Liqun , Chen Lei
Published: May 2024

The density of underwater dumping materials plays a major role in cofferdam engineering designs. However, it is difficult to accurately measure the density of underwater dumping materials. This study investigated the influence of particle size distribution of granular materials on the density of underwater filling materials. Considering the underwater dumping project of a hydropower station dam in the Han River as the prototype condition, several underwater dumping density centrifugal tests were conducted on sand gravel and sand mixtures. Based on the CKY200 large-scale geotechnical centrifuge, a single-embankment vertical-blockage underwater filling test device in a centrifuge field was developed. The results demonstrated the relationship between the compactness of the dumping body and the grading of loose particles, depth of dumping, and height of the upper loading. This indicates that the underwater filling material has a higher compactness and can reach a dense state. When the grading is poor, the compactness decreases. The greater the depth of filling, the greater the compactness. When vertical compression was applied to the upper part of the backfill, the compactness of the backfill, particularly in shallow areas, was significantly improved. These results provide insights for the design and construction of underwater dumping water conservation systems.
Numerical study of borehole instability of large diameter monopile during the window period between drilling and pile driving
Authors: Zhang Q , Chai Y H , Zhu W X , Ye G L
Published: May 2024

Large-diameter monopiles are among the most widely used offshore wind turbine foundations. Implementing drive-drill-drive construction techniques in a decomposed granite seabed may lead to borehole instability during the window period between drilling and pile driving. In this study, the borehole stability of a large-diameter monopile in a weathered granite seabed was investigated using the discrete element method. A linear parallel bond model was employed to simulate the bonding effect among weathered granite particles, and the influence of pore water was considered. The results indicated that soil shear failure caused by excavation unloading was the primary cause of borehole instability. The exposed height of the unsupported borehole significantly influenced the occurrence of borehole instability. The greater the exposed height of the unsupported borehole, the larger the soil arch required to maintain the stability of the borehole, and the less stable the soil arch becomes. Moreover, the susceptibility to borehole instability and collapse also increased.
In situ monitoring of the impacts of Melaleuca styphelioides transpiration on soil water dynamics in an urban environment
Authors: Sun Xi , Li Jie , Ren Gang
Published: May 2024

Expansive soils are susceptible to substantial cyclical moisture variations under the prevailing climate, experiencing considerable shrinkage during drought and swelling when water availability increases. These dynamic volumetric changes jeopardize the functionality of lightweight infrastructures with shallow foundations. The presence of trees may amplify seasonal soil movements, as extensive water uptake by root networks in the summer months can induce soil moisture depletion and the resulting desiccation-driven settlement around the trees. This study assessed the drying effect of mature Melaleuca styphelioides on soil movement and water dynamics at an urban experimental site in Melbourne, Australia, instrumented for in situ monitoring over 12 months. Sap flow instrumentation was used to quantify seasonal variations in tree transpiration. The monitoring results revealed that the drying influence of the tree has extended to a depth of 2.2 m. Tree root-induced soil desiccation occurred 4.0 m away from the tree, as evidenced by the seasonal soil movement profiles. Linear regression analysis showed that the soil water content explained 60% of the variability in tree transpiration. In contrast, the soil water content and suction exhibited a robust negative correlation (R2=0.96) within the active root zone.
Simple method to determine coefficient of permeability of unsaturated soil
Authors: Nguyen T B , Zhu Y L
Published: May 2024

This study introduces a novel transient method for determining the unsaturated coefficient of soil permeability, requiring the measurement of volumetric water content and corresponding pore-water pressures at three distinct points. This distinctive advantage of the method lies in eliminating the need to measure or control the flux at any point within the soil profile. The proposed method was validated through numerical simulations that performed one-dimensional seepage analysis, followed by a comparison of the calculated unsaturated coefficients of permeability with the input data. The strong agreement between the compared results validates the feasibility of the proposed method for determining the unsaturated coefficient of soil permeability. Moreover, a spatial interval of less than 5 cm is recommended to ensure accurate results for the unsaturated coefficient of permeability when employing this method.
Physical model test on rainfall-induced instability of silty slope
Authors: Bai M H , Gao X G , Wang J P
Published: May 2024

In the context of ecological conservation and high-quality development in the Yellow River Basin, extensive silty slopes have emerged in the downstream alluvial plain regions owing to engineering construction. These slopes are susceptible to rainfall infiltration-induced instability, resulting in geological hazards, such as landslides and mudslides. This study explored the hydrodynamic characteristics and spatiotemporal evolution patterns of silty slopes under rainfall conditions, focusing on the alluvial silty slopes of the Yellow River. Experiments were performed to monitor variations in soil water content, soil water potential, and pore water pressure at various locations on the slope. Slope instability and failure under rainfall were monitored using high-frequency photography technology. The results indicated the development of layered vertical collapses along the surface of the slope, starting from the base and accumulating below the failure point. With increasing rainfall intensity, soil water content, soil water potential, and pore water pressure increased earlier at various points on the slope. These findings provide crucial experimental data and a theoretical foundation for exploring the instability mechanisms within silty slopes in the lower Yellow River’s alluvial and siltation plain areas during rainfall events. Moreover, they are significant for formulating more effective strategies for geological disaster warning and prevention.
Macro-meso properties and damage constitutive model of sandstone under chemical and freeze-thaw environments
Authors: Liang Y , Huo R , Song S , Zhang Y , Wang B , Jie J
Published: May 2024

The coupled effect of chemical corrosion and freeze-thaw cycle degrades the physical and mechanical properties of rock, affecting the safety and durability of underground rock mass engineering. This study investigated the deterioration laws of sandstone under pH = 1 and 3 chemical and freeze-thaw cycle action for different time considering macro and meso scales. The stress-strain curve of sandstone under uniaxial compression can be divided into compaction, elastic deformation, yield, and post-peak stages. The compaction of sandstone after chemical and freeze-thaw cycle action became apparent, elastic stage was relatively shortened, elastic modulus and peak strength decreased, and peak strain increased. The density and homogeneity of sandstone declined as per the CT scan and image processing technologies. The deterioration was prominent with longer action time and smaller pH value of the solution. After 120 days of pH = 1 and 3 chemical and freeze-thaw cycle action, the peak stress of samples decreased by 22.10% and 15.16%, the elastic modulus declined by 89.57% and 85.09%, the peak strain increased by 96% and 62%, and the damage variables reached 3.27% and 1.83%. The damage constitutive model of sandstone was established using statistical damage theories. The theoretical stress-strain curves were consistent with experimental ones. The insights of this research have implications for the theoretical foundation of safety assessments and disaster prevention in practical engineering scenarios under chemical and freeze-thaw environments.
A discrete approach for modelling the permeability evolution of granite under triaxial and true-triaxial stress conditions
Authors: He Chen , Yao Chi , Shao Yulong , Jiang Qinghui , Zhou Chuangbing
Published: May 2024

In deep underground engineering, modelling the seepage characteristics of rock masses under complex stress conditions is crucial for the safe construction and stable operation of a project. The permeability of the rock mass is not only controlled by its internal pore structure but is also closely related to the deformation and fracturing of the rock. Although discrete methods offer advantages in describing the formation and development of fractures, these methods still face challenges due to the difficulties in establishing microscopic seepage models. This paper introduces a new hydro-mechanical coupled numerical model. In this model, a simple method is proposed to couple the Rigid-Body-Spring Method (RBSM) for rock deformation and fracturing simulation and the Equivalent Matrix-Fracture Network (EMFN) for seepage simulation. Subsequently, the model is employed to simulate the permeability of granite under three-dimensional stress conditions. The simulation results show that under hydrostatic stress conditions, the model accurately captures the decrease in permeability due to pore compression and collapse. Additionally, under deviatoric stress conditions, it reveals the stage-wise increase in permeability caused by granite fracturing. Finally, the model is applied to study the permeability evolution behaviour of rocks under true triaxial stress conditions. The results unveiled the significant impact of the intermediate principal stress on permeability evolution and revealing the microscopic mechanisms underpinning these effects. This paper paves a way for enhancing the application of discrete methods in forecasting the permeability evolution behaviour of intricate rock masses.
Method for identifying the position of crack tip by displacement distribution based on digital image correlation
Authors: Zhao Cheng , Fu Jiao , Xing Jinquan , Xiang Fubin , Qian Yuan
Published: May 2024

Determining the position of crack tip is crucial for rock fracture characteristic analysis. This study aims to establish a quantitative standard for determining crack tip positions in crystalline rocks based on digital image correlation (DIC). Semi-circular bending (SCB) tests were conducted on four types of rocks under three-point bending. Optical microscopy and DIC were used to investigate characteristics of the horizontal displacement fields around the crack tips. A significant disparity in the displacement gradient was observed across the crack tips, with the internal gradient being approximately 3–5.1 times higher than the external gradient. A critical value ranging from 0.41%–0.64% was determined for the high internal displacement gradient (∂u/∂x) at a 20 pixel resolution equivalent to 1 mm. Furthermore, a novel DIC-based method was proposed that used three patterns of opening displacement gradients to classify SCB specimens into non-cohesive, cohesive, and elastic zones, providing a quantitative determination of Type I crack tip positions. This study offers valuable insights and a crack tip determination method based on DIC gradients, applicable for assessing parameters such as the crack extension length and fracture process zone length.
Meso-mechanical behavior of crystalline rocks: An image-based discrete element method
Authors: Pan Haoyu , Zhao Cheng , Chen Huiguan , Yang Hongwei , Xing Jinquan
Published: May 2024

This research examines the meso-mechanical behavior of rock materials under various loading conditions, with a focus on the influence of mesoscale heterogeneity in crystalline rock specimens. Traditional approaches often rely on a limited set of statistical parameters for constructing numerical models, failing to capture the complex mesoscale heterogeneities integral to rock mechanics. To overcome this limitation, the study utilizes an advanced image-processing technique to accurately identify mineralogical features within rock microstructures. The extracted mineralogical data were then integrated into a discrete element method (DEM) model to explore the mesoscale mechanical responses of crystalline rocks. The results of the simulations indicated that mesoscale heterogeneities play a critical role in stress concentration localization, which in turn dictates the direction of fracture propagation and leads to a sophisticated interaction among various fracture pathways.
Sustainable development of pavement base stabilization using future road base material (FROBM)
Authors: Bualuang T , Jitsangiam P , Chusai N
Published: May 2024

Sustainable road construction has emerged as a critical issue in assessing natural resources and urban development. With the rapid expansion of pavement networks to meet growing traffic demands, road base construction relies heavily on the consumption of natural aggregates and Ordinary Portland Cement (OPC) through the cement-treated base (CTB) technique. This practice contributes to the global warming and greenhouse gas (GHG) emissions associated with road construction. This study investigated a novel road base material, Future Road Base Material (FROBM), which emphasizes both eco-friendliness and economic advantages. Fine crushed rock (FCR) served as the parent aggregate and was modified with a chemical binder comprising 4% of the FCR weight. The proposed sustainable cementitious material, functioning as a non-OPC binder, incorporated fly ash and hydrated limestone as pozzolanic materials, along with sodium hydroxide (NaOH) as an alkali additive. An asphalt emulsion (AE) was employed as a special additive to enhance crucial pavement engineering properties. Through life cycle analysis (LCA), the construction activities and material acquisition of each stabilized base technique were evaluated in terms of project costs and carbon footprints. The non-OPC binder offered sufficient compressive strength for a stabilized base course. Furthermore, the addition of AE improved the elastic modulus and modulus of rupture of the non-OPC binder-stabilized mixture. Utilizing a non-OPC binder and AE in the base layer provides advantages in terms of construction cost and environmental impact. Although the costs increased slightly, the GHG emissions were reduced by approximately 30% compared to conventional base materials, with equivalent functionality and service life for road construction. The proposed stabilizing agent reduced the operational processes and demand for natural aggregates compared with the unbound FCR base course. Road-base stabilization using a non-OPC binder and AE represents an innovative approach to mitigate waste in coal mining and power plant industries by transitioning to a cleaner product. The concept of the FROBM serves as a valuable guideline for the development of future sustainable pavement materials.
Simulation of soil-structure interaction of integral abutment bridges using advanced constitutive relations
Authors: Hassan M S K , Liyanapathirana D S , Fuentes W , Leo C J , Hu P
Published: May 2024

Integral bridges have been proposed as an attractive design concept that negate the requirements for expansion joints. However, owing to structural continuity, seasonal and diurnal thermal fluctuations have subjected the abutments to long-term cyclic interaction with approach backfills. This resulted in two notable geotechnical complications: ratcheting of lateral stresses and progressive soil deformation. To understand these phenomena, considerable research has been conducted using numerical methods. Here, either Winkler springs or simple constitutive relations, such as the Mohr-Coulomb model, are predominantly utilized. However, the former is based on monotonic displacement-dependent stiffness theories, and the latter is constrained by the limitations of the traditional yield surface plasticity. Hence, neither possesses the capability to simulate the hysteretic response, which is a characteristic of integral bridge approaches. Therefore, this study aims to present the advantages of using advanced constitutive relations to predict the long-term behavior of integral bridge approach backfills. First, using a lateral cyclic triaxial simulation, the significance of soil densification was highlighted by comparing the performance of the Mohr-Coulomb model with that of the bounding surface Dafalias-Manzari-2004 model. Subsequently, further comparisons were performed with the centrifuge model data of the integral abutment. At both the element and boundary value levels, the Mohr-Coulomb model could not capture the gradual accumulation of the lateral stresses. Conversely, the Dafalias-Manzari-2004 model can estimate the long-term passive pressure accumulation along the height of the abutment.
Pore structure characteristics of coral reef limestone: a combined polarizing microscope and CT scanning study
Authors: Xu J , Huang X , Zhang Z , Jin G
Published: May 2024

Coral reef limestone is a special class of geological medium formed through long-term deposition following the death of reef-building coral groups. Because it retains the skeletal structure of marine organisms during its formation, its pore structure is hyper-developed and complex. Deciphering the pore structure of the coral reef limestone is important because it is closely related to its macroscopic physical and mechanical properties. This study conducted a comprehensive analysis of the pore structure features of two types of coral reef limestone collected from the construction site of a nuclear power station located in the South China Sea using a combination of polarizing microscopy and CT scanning technologies. The fractal dimension of the pore structure of the treated reef limestone image was calculated, and the pore structure characteristics were statistically analyzed by considering several parameters including porosity, pore size, pore equivalent radius, shape factor, etc. In addition, the directional feature of the pore structure was explored. The results show that the improved watershed segmentation algorithm can accurately segment the pore structure of reef limestone images; both coral reef limestone specimens are loose of high porosity; the fractal dimension of pore structure lay between 1.58∼1.75, indicative of a high self-similarity; the pore size of the two coral reef limestone specimens is quite different, and the distribution of equivalent pore radius conforms to the normal distribution law; the pore structure of the two samples had obvious directionality, which can be quantified using a directional tensor. This study sheds light on future investigations linking the microscopic structure and macroscopic properties of coral reef limestones.
Holding capacity of a novel hybrid helical-skirted foundation of offshore wind turbines
Authors: Norouzi Behnam , Wanga Yifa , Ye Guanlin , Li Zeliang , Tian Yinghui
Published: May 2024

A novel hybrid foundation consisting of a helical pile and a peripheral skirt was introduced in this study. This hybrid foundation exploits both the helical pile and the skirted foundation. This study focused on evaluating the undrained vertical holding capacity of this hybrid foundation in clay using three-dimensional finite element analysis. Their capacities and failure mechanisms were examined and compared. The analysis results showed that a significant increase in the vertical holding capacity was achieved compared to that of an individual component, which is attributed to the enhanced soil mobilization mechanism.
Study on the properties of nano-Fe3O4 modified asphalt materials based on molecular dynamics
Authors: Chen Xueqin , Zhang Yuhui , Liu Kailiang , Dong Qiao
Published: May 2024

Asphalt possesses the inherent ability to self-heal microcracks, with enhanced healing observed under active heating conditions. Nanomaterials have the capacity to alter the microstructure of asphalt blends, offering certain advantages in terms of asphalt performance. In this study, models of nano-Fe3O4 clusters and nano-Fe3O4/asphalt blending systems with varying particle sizes were established. Molecular dynamics simulations were employed to investigate the physical properties of nano-Fe3O4 and asphalt molecules at different temperatures, simulating the microwave heating process within a temperature range of 303 K to 373 K. The findings revealed that the diffusion coefficient of Fe3O4 clusters decreased with increasing particle size. Nonbonding interaction energy predominantly governed the binding between Fe3O4 clusters and asphalt molecules. The incorporation of nano-Fe3O4 was found to enhance the physical properties of asphalt. Peak values of the radius of gyration for asphaltene and aromatics indicated increased density, while asphaltene, colloids, and aromatics exhibited greater extensibility with the addition of nano-Fe3O4.
Dynamic characteristics and microstructure of clay reinforced by the splitting grouting method under subway dynamic loading
Authors: Zhou J , Zhou H , Tang Y
Published: May 2024

The splitting grouting reinforcement method is typically used to improve the stability of surrounding rock when constructing subways in water-rich and weak strata. However, in contrast to normal soil, the dynamic characteristics and microstructure of reinforced soil under cyclic loading of a subway necessitates further clarification to obtain a technical basis for controlling the deformation and settlement of the reinforced soil during later stages. Based on field-reinforced soft clay samples, this study analyzed the dynamic characteristics and microstructure of reinforced soft clay under cyclic loading through stress-controlled undrained cyclic triaxial and scanning electron microscope tests. The results showed that the lower the frequency or the larger the cyclic dynamic stress amplitude, the faster the residual strain development of the reinforced soft clay. There were three cyclic creep characteristic curves of reinforced soft clay: peak, base, and valley creep curves, and the development of base creep represented the overall trend of cyclic creep in reinforced soft clay. In addition, calcium silicate hydrate and ettringite were produced in the reinforced soft clay, which improved the connectivity between the soil particles.
Interpretation method for laser-scanning point clouds of segmental tunnel linings based on hybrid analysis
Authors: Zhang Y , Liu X , Karlovšek J
Published: May 2024

Owing to its convenience and precision, laser scanning has been applied in inspecting segmental tunnel linings. The point clouds generated by laser scanning provide valuable geometric information regarding the lining profile. Numerous studies have identified defects including cracks, leaks, and concrete spalling from these point clouds. However, they primarily relied on computer vision and neglected the mechanical information inherent in point clouds. This paper proposes a method for interpreting laser-scanning point clouds related to segmental tunnel linings based on analytical back analysis, known as hybrid analysis. The objective involves interpreting the mechanical behavior of segmental tunnel linings derived from point clouds. Through hybrid analysis, the deformation of the segmental tunnel linings was broken down into deflection and rigid-body motion. This process revealed the contribution of joints to the overall deformation of the linings. The strain of the segmental tunnel linings can be further quantified using the elastic theory of an arch slender. To validate the hybrid analysis, results were compared with experimental monitoring results. Further, potential application scenarios for the proposed method were explored. This method holds promise in engineering practice because it requires limited knowledge of the external loads, rendering it suitable for in-operation tunnels buried in uncertain strata.
Study on the shear characteristics of the cemented soil-concrete interface after artificial freeze-thaw under vibration loading
Authors: Zhou J , Ban C , Liu C , Zhou H
Published: May 2024

Underground construction has reduced underground space. Consequently, engineering construction is being done near existing structures. The artificial ground freezing (AGF) method is effective in such projects, and cement is often used to reduce frost heave and thaw settlement. A cemented soil-concrete interface is formed around underground structures. The interface serves as the primary medium for interaction between the two materials. Therefore, the shear characteristics of the cemented soil–concrete interface after artificial freeze–thaw cycles under the influence of the surrounding vibration load in underground engineering must be understood. This study conducted large-scale interface shear tests of a cemented soil–concrete interface with vibration loading. The effects of curing time and artificial freeze–thaw cycles on interface shear characteristics were studied. Furthermore, unconfined compressive tests of the cemented soil under artificial freeze–thaw conditions were conducted. The shear strength of the interface increased with curing time. The shear strength of the interface and the unconfined compressive strength of the cemented soil increased rapidly in the early stage of curing and gradually slowed after seven days. Artificial freeze–thaw reduced the shear strength of the interface with vibration loading. The results enrich ongoing research on the shear characteristics of cemented soil-concrete interfaces.
Forward solution of shield tunneling pose based on the Newton–Raphson method
Authors: Han Yuzhen , Wang Xuyang , Nie Xiaofan , He Jizhong , Zhang Lianwei
Published: May 2024

To achieve precise control of the shield tunneling pose, obtaining a real-time shield pose state during the excavation process is necessary to achieve closed-loop feedback control of the shield pose. This study proposes a forward solution method to address the high cost and low efficiency of direct measurement methods, such as using lasers and gyroscopes, for measuring shield pose. This method relies on the real-time measurement of the strokes of hydraulic thrust cylinders during shield tunneling. Based on the inverse kinematics of the shield machine, the Newton–Raphson method was used to calculate the shield tunneling pose. Accordingly, a forward solution algorithm for shield pose was developed using MATLAB, and the effectiveness of the proposed method was verified through an example analysis. The results demonstrated the high computational efficiency of the method, proving its potential application in real-time control systems for shield tunneling poses.
Prediction of ground surface settlements by analytical and finite element methods
Authors: Wang Y H , Lam C C , Lok M H
Published: May 2024

The soil surrounding the excavation of shallow tunnels may experience destructive deformation near the tunnels. Particularly in densely populated areas where land resources are scarce, ground subsidence caused by tunnel excavation, which in turn affects surrounding structures, deserves more attention. Over the past few decades, various research methods for predicting the maximum vertical ground surface settlement have been proposed. In this study, an empirical estimation method, an analytical technique for evaluating ground movements, and a numerical simulation method using Plaxis 2D, a finite element model software, were selected as prediction approaches for ground surface settlements. Subsidence measurements were obtained from a metro tunnel excavated using an earth pressure balance shield tunnel boring machine and constructed in a dense sandy gravel layer. Comparison of the monitored deformations with the estimation results calculated by different prediction approaches showed that the maximum vertical settlement of the ground surface evaluated by the analytical technique and finite element model agreed well with the actual measured values. This suggests that these two prediction methods have the potential for conserving nearby structures during the construction of underground infrastructures.
Complex variable solution for ground deformation responses considering the grouting pressure of shallow shield
Authors: Huang Siyuan , Zhong Xiaochun
Published: May 2024

During shield tunneling in shallow strata, ground deformation is highly sensitive to grouting pressure response. Excessive grouting pressure can cause ground uplift, and an excessively low grouting pressure can cause excessive ground settlement, affecting the surrounding environment. Current studies seldom analyze the influence of shield excavation on ground deformation when the grouting pressure is considered. To ensure micro-disturbance of the surrounding environment during shield tunneling, this study presents a complex variable analysis method for analyzing the influence of grouting pressure on surface settlement. This solution maps the semi-infinite strata outside the segment into circular domains by introducing a complex function conformal mapping method. The nonuniform convergence deformation pattern BC-4 was introduced as the boundary condition for the displacement around the tunnel. The Laurent series expansion of the analytical function considering the grouting pressure in the circular domain was substituted into each boundary condition to solve the analytical function. Subsequently, the accuracy of the analytical method was verified by combining it with a finite element numerical method. Finally, the influence of grouting pressure on ground deformation under different working conditions was analyzed through parameterization. This analytical method can provide a theoretical basis for controlling grouting pressure parameters in shield tunnels.
Study on the escaping condition of backfill grouting based on two-phases flow for shield tunnelling during whole section rock
Authors: Zhu C , Ji B H , Li F D , Zhong X C , Jian Y Z , Gao W , Wu R H
Published: May 2024

During the process of full section surrounding rock shield tunneling, the occurrence of synchronous grout escaping can seriously affect the assembly quality of the detached shield tail segment ring. The segment is prone to quality accidents such as floating, misalignment of the tunnel pipes, and even cracking, and even a large number of rock fractures in the shield tail gap mix with water flow towards the excavation face and pressure chamber, leading to frequent fissure water gushing out of the screw conveyor. Taking the shield tunnelling section of Nanjing Metro Line 6 as the engineering background, this paper uses the finite element software Ansys Fluent to establish the two-phases flow shield tail escaping grout model, and analyzes the influence laws of the grout properties, grouting pressure difference, grouting escaping thickness and other factors in the process of grout escaping behind the shield tail wall based on Bingham fluid. The results show that the amount of synchronized grout escaping increases linearly with the increase of grouting pressure difference and grouting escaping thickness, and decreases with the increase of grout shear yield stress. The paper also discusses the three-dimensional curved surface of grout escaping volume, grouting pressure difference and grouting fluid properties behind shield tunnel tail in a full section surrounding rock shield project of Nanjing Line 6, and gives the measures to prevent grout escaping when the allowable grout escaping volume is not more than 1m3: when the grouting escaping thickness is 20mm, the grouting pressure difference should be controlled within 0.20∼0.25MPa, and the shear yield stress of the grouting fluid should be controlled within 300∼350Pa.
Optimization of blasting construction and vibration control technology of multi arch tunnels without central partition walls
Authors: Zhou Y , Xu J , Li P
Published: May 2024

The construction technology for multi arch tunnels without central partition walls is a new design method for multi arch tunnels. The construction technology of multi arch tunnels without central guide tunnels eliminates side and central guide tunnels, which not only accelerates construction progress but also ensures construction quality and safety. The excavation and support of the rear tunnel of a double-arch tunnel without a central partition are crucial to ensuring the overall stability of the tunnel structure. A combination of manual mechanical excavation and blasting excavation in some areas was used in the excavation and construction of the rear tunnel of the Chenjiachong Tunnel on the Chuyao Expressway in Yunnan in addition to damping materials and measures in the lining of the front tunnel, ensuring the safe excavation of the rear tunnel and the prevention of the lining of the front tunnel from cracking because of earthquakes, The on-site vibration monitoring results of the tunnel indicate that this technology has achieved good results. Overall, the optimized construction technology without a central partition greatly shortens the construction period and improves economic benefits. The construction method is simple and feasible and can be flexibly selected according to the surrounding rock conditions. This study can provide a reference for the construction of other highway tunnels in mountainous areas.
Analysis of tunnel collapse disasters during operation and exploration of disaster damage mechanisms
Authors: Lei B , Ding W , Huang X , Zhang Q
Published: May 2024

Highway tunnel collapse during the operation period is a serious threat to the stability of tunnel operation. Thus, it is important to investigate the disaster-causing mechanism to prevent the occurrence of disasters. In this paper, based on 155 cases of domestic and foreign highway tunnel collapses during operation, we statistically analyze the causes of the collapses and the year of occurrence, and we explore the disaster-causing mechanism of tunnel collapses through numerical simulation. Tunnel collapses in operation period are affected by geological factors, lining factors, and accidental factors. The primary causes of tunnel collapses are determined to be the post-lining cavity, lining crack expansion, and fire. A single factor cannot lead to tunnel collapse, and the probability of collapse increases under the coupling of multiple factors. Through a numerical simulation method, the evolution mechanism of tunnel collapse caused by the post-lining cavity is analyzed, which lays the foundation for establishing the tunnel collapse prediction model and qualitative risk assessment system of highway tunnel collapse.
Application of super large and deep diameter assembly shafts in soft soil layers
Authors: Long Y , Zhibing X , Xian L , Juntao N , Sebastian R
Published: May 2024

Considering the background of the Shanghai Jing’an Smart Garage Project, first, we introduced the world’s largest vertical shaft boring machine, which was suitable for vertical shaft excavation of diameter 12∼23 m. Then, we expounded the design points and key technologies of super large and deep diameter assembly shafts in soft soil layers. Finally, we verified the applicability of the vertical shaft boring technology in soft soil layers in Shanghai through on-site measurement results. It was observed that this technology had a minimal impact on the surrounding environment, indicating its potential for widespread applications in the coming years.
Calculation model of depth under quantification of surface morphology of dry shrinkage cracks in red clay
Authors: Ren Jiazhan , Yao Ying-jie , Dong Hui , Jing Ye
Published: May 2024

Cracks commonly form in clay owing to water loss, negatively affecting strength and hydraulic properties of soil, leading to rock and soil damage including landslides and dam instability. Understanding the changing patterns of the shrinkage crack depth is crucial for exploring slope infiltration patterns and determining key factors for slope stability. This study suggests a relationship between the surface and depth variations during cracking, and investigates the influence of the surface roughness on shrinkage cracks in saturated red clay. Regression analysis and machine learning algorithms were used to establish a depth prediction model. (1) Based on the surface morphology of shrinkage cracks, they are categorized into three types: linear, curved, and inflectional (linear and curved are the main types). (2) The surface roughness and development rate of surface cracks were positively correlated. (3) Based on the geometric parameters of the crack surface, a prediction model (error within 15%) for crack depth was established using multivariate nonlinear regression, providing a reference for the initial assessment of crack depth. These results provide a better understanding of the development patterns of shrinkage cracks, whose influence on slope stability is critical for mitigating the risks associated with slope instability and other soil failures.