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Soil disturbance evaluation of soft clay based on stress-normalized smallstrain stiffness

Journal of Rock Mechanics and Geotechnical Engineering 2024年第3期16卷 990-999页

作者： Yanguo Zhou Yu Tian Junneng Ye Xuecheng Bian yunmin chen MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Institute of Geotechnical EngineeringCenter for Hypergravity Experiment and Interdisciplinary ResearchZhejiang UniversityHangzhou310058China Ningbo Rail Transit Group Co. Ltd.Ningbo315010China

Soil disturbance includes the change of stress state and the damage of soil structure.The field testing indices reflect the combined effect of both changes and it is difficult to identify the soil structure disturbance directly from these indices.In the present study,the small-strain shear modulus is used to characterize soil structure disturbance by normalizing the effective stress and void ratio based on Hardin equation.The procedure for evaluating soil sampling disturbance in the field and the further disturbance during the subsequent consolidation process in laboratory test is proposed,and then validated by a case study of soft clay ground.Downhole seismic testing in the field,portable piezoelectric bender elements for the drilled sample and bender elements in triaxial apparatus for the consolidated sample were used to monitor the shear wave velocity of the soil from intact to disturbed and even remolded states.It is found that soil sampling disturbance degree by conventional thin-wall sampler is about 30%according to the proposed procedure,which is slightly higher than that from the modified volume compression method proposed by Hong and Onitsuka(1998).And the additional soil disturbance induced by consolidation in laboratory could reach about 50%when the consolidation pressure is far beyond the structural yield stress,and it follows the plastic volumetric strain quite well.

关键词： Natural clay Soil sample disturbance Shear wave velocity Small-strain shear modulus Hardin equation

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Feasibility analysis of hypergravity experiment of density-driven convection of dissolved CO

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Journal of Earth Science 2024年

作者： Ruiqi chen Wenjie Xu Yingtao Hu yunmin chen Jinlong Li Duanyang Zhuang Center for Hypergravity Experimental and Interdisciplinary Research Zhejiang University MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Zhejiang University School of Engineering Hangzhou City University

Dissolution trapping is one of the most promising mechanisms for safe geological carbon storage. Density-driven convection substantially accelerates the conversion of free-phase CO2to the dissolved state， enhancing the sequestration safety. Since this process occurs on time scales of hundreds to thousands of years， reproducing it through conventional laboratory physical model tests is challenging. The hypergravity experiment reduces the model size and shortens the experimental time， enabling the modeling of gravity-driven flow processes at the field scale. However， it is uncertain whether the preferential flow effect caused by fractures can be reproduced in a hypergravity experiment. In this study， a three-dimensional discrete fracture-matrix model （3D-DFM） was used to evaluate the feasibility of hypergravity experiment of the transport of dissolved CO2in fractured reservoirs.Numerical hypergravity tests were performed to examine the feasibility of modeling density-driven convection in homogeneous and heterogeneous media at different centrifuge accelerations. The hypergravity experiment can be used to study density-driven convection of dissolved CO2at the field scale in homogeneous system. The numerical results show that the hypergravity experiment enables a faster breakthrough of plume and overestimates CO2migration in the matrix surrounding the fractures.

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Using cemented paste backfill to tackle the phosphogypsum stockpile in China:A down-to-earth technology with new vitalities in pollutant retention and CO_(2) abatement

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1480-1499页

作者： Yikai Liu yunmin Wang Qiusong chen School of Resources and Safety Engineering Central South UniversityChangsha 410083China Department of Geosciences and CIRCe Centre University of PaduaPadua 35129Italy Sinosteel Maanshan General Institute of Mining Research Co. Ltd.Ma'anshan 24300China

Phosphogypsum(PG),a hard-to-dissipate by-product of the phosphorus fertilizer production industry,places strain on the biogeochemical cycles and ecosystem functions of storage sites.This pervasive problem is already widespread worldwide and requires careful stewardship.In this study,we review the presence of potentially toxic elements(PTEs)in PG and describe their associations with soil properties,anthropogenic activities,and surrounding organisms.Then,we review different ex-/in-situ solutions for promoting the sustainable management of PG,with an emphasis on in-situ cemented paste backfill,which offers a cost-effective and highly scalable opportunity to advance the value-added recovery of PG.However,concerns related to the PTEs'retention capacity and long-term effectiveness limit the implementation of this strategy.Furthermore,given that the large-scale demand for ordinary Portland cement from this conventional option has resulted in significant CO_(2) emissions,the technology has recently undergone additional scrutiny to meet the climate mitigation ambition of the Paris Agreement and China's Carbon Neutrality Economy.Therefore,we discuss the ways by which we can integrate innovative strategies,including supplementary cementitious materials,alternative binder solutions,CO_(2) mineralization,CO_(2) curing,and optimization of the supply chain for the profitability and sustainability of PG remediation.However,to maximize the co-benefits in environmental,social,and economic,future research must bridge the gap between the feasibility of expanding these advanced pathways and the multidisciplinary needs.

关键词： cemented paste backfill phosphogypsum carbon dioxide mitigation potentially toxic elements solidification and stabilization

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Impact of extreme climate and train traffic loads on the performance of high-speed railway geotechnical infrastructures

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第3期24卷 189-205页

作者： Ying WU Haoran FU Xuecheng BIAN yunmin chen MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Zhejiang UniversityHangzhou 310058China Department of Civil Engineering Zhejiang UniversityHangzhou 310058China

High-speed railways are very important in global transportation.However,the railway subgrade is significantly affected by the environment due to its exposure to the atmosphere.At present,global warming is the primary trend in world climate change and seriously damages railway infrastructure.Owing to the coupling effect of extreme environmental and train loads,various subgrade problems tend to arise,such as settlement,ballast fouling,and mud pumping,thus inducing frequent railway accidents and reducing travel safety.Insights into the problems triggered by extreme climate and train loads are critical to the design and long-term operation of high-speed railway subgrades.This study therefore presents a detailed survey of recent advances in typical subgrade problems through analyzing the problem formation mechanisms and influences.Traditional and emerging detection/monitoring technologies in respect of subgrade problems are discussed in detail,as well as pre-accident and post-accident maintenance methods.Finally,according to the existing challenges in long-term subgrade shakedown assessment,an outlook on open opportunities is provided for future research.

关键词： High-speed railways Subgrade performance Train loads Extreme climate

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Mud pumping in high‑speed railway:in‑situ soil core test and full‑scale model testing

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Railway Engineering Science 2022年第3期30卷 289-303页

作者： Zhangbo Wan Xuecheng Bian yunmin chen Key Laboratory of Soft Soils and Geoenvironmental Engineering MOEDepartment of Civil EngineeringZhejiang UniversityHangzhou 310058People’s Republic of China Center for Hypergravity Experimental and Interdisciplinary Research Zhejiang UniversityHangzhou 310058People’s Republic of China

Mud pumping induced by moving train loads on rainwater-intruded roadbed causes intensive track vibrations and threatens safety of high-speed trains.In this paper,a vehicle–track–subgrade finite element model was established to analyze the dynamic responses of a ballastless track,and results showed that the concrete base and roadbed were detached because of the whipping effect arising from the rainwater intrusion channel.An in-situ soil core test showed that the intruded rainwater accumulated in roadbed to form standing water and saturated the roadbed.The flapping action of the concrete base caused by the whipping effect led to mud formation mixed with fine particles and rainwater,which migrated upward under the pore-water pressure(PWP)gradient.Mud pumping resulted from continuous particle migration in the saturated roadbed under moving train loads:under normal roadbed condition,coarse and fine particles were uniformly distributed in the roadbed;in early period of mud pumping,fine particles migrated downward to bottom of the roadbed because of the rainwater infiltration flow;in middle stage of mud pumping,fine particles migrated upward and gathered at the roadbed surface under PWP gradient;in later period of mud pumping,fine particles were entrained and removed with the dissipation of excess PWP.Moreover,a full-scale physical model was established to reproduce mud pumping,and polyurethane injection remediation against mud pumping was validated on this physical model.The remediation method was applied to an in-situ mud pumping.The deviation of the vertical track profile reduced remarkably and remained at a low level within half a year,showing a good long-term service performance of the polyurethane remediated roadbed.

关键词： Ballastless track Mud pumping Rainwater intrusion Particle migration Polyurethane injection

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Molecular force mechanism of hydrodynamics in clay nanopores

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浙江大学学报(英文版)A辑:应用物理与工程 2023年第9期24卷 817-827页

作者： Shengjie WEI Yuchao LI Peng SHEN yunmin chen MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering College of Civil Engineering and ArchitectureZhejiang UniversityHangzhou 310058China

Nanopores are prevalent within various clay morphologies,and water flow in clay nanopores is significant for various engineering applications.In this study,we performed non-equilibrium molecular dynamics(NEMD)simulations to reveal the molecular force mechanisms of water flow in clay nanopores.The water dynamic viscosity,slip length,and average flow velocity were obtained to verify the NEMD models.Since the water confined in the nanopores maintained a dynamic mechanical equilibrium state,each water lamina can be regarded as a simply supported beam.The applied driving force,the force from clay crystal layers,the force from compensating sodium ions,and the force from other water laminae were further calculated to investigate the force mechanisms.The van der Wals barrier above the surface and hydraulic gradient lead to distribution differences in water oxygen atoms,which contribute to a net van der Waals resistance component of the force from clay crystal layers.Meanwhile,the water molecules tend to rotate to generate the electrostatic resistance component of the force from clay crystal layers and balance the increasing hydraulic gradient.Due to the velocity difference,the water molecules in the slower lamina have a higher tendency to lag and generate a net electrostatic resistance force as well as a net van der Waals driving force on the water molecules in the faster lamina,which together make up the viscous force.

关键词： Molecular dynamics Hydrodynamics Clay Nanopore Molecular force Boundary effect Viscous force

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Numerical investigation of the effect of geosynthetic clay liner chemical incompatibility on flow and contaminant transport through a defective composite liner

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第7期24卷 557-568页

作者： Shiyuan YAO Yuchao LI Shan TONG Guannian chen yunmin chen MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Department of Civil EngineeringZhejiang UniversityHangzhou 310058 China School of Civil&Environmental Engineering and Geography Science Ningbo UniversityNingbo 315211China Ningbo ZCONE High-tech Co. Ltd.Ningbo 315000China

A composite liner consisting of a geomembrane(GMB)and a geosynthetic clay liner(GCL)can be compromised by inorganic contaminants because of a defective GMB.When the composite liner with defective GMB is exposed to aggressive leachate conditions,the neglect of the chemical incompatibility of the GCL can potentially result in an underestimation of the leakage rate and flux through the composite liner.This paper proposed a numerical investigation on the effect of chemical incompatibility of GCL on the barrier performance of the composite liner with hole defect.Four cases with leachate solutions having varied cation valencies and ionic strengths were analyzed,in which the hydraulic conductivity of GCL was concentrationdependent.Both the effect of the chemical incompatibility of GCL and the mechanisms were analyzed.The incompatibility of GCL resulted in significant increases in leakage rate and flux through the composite liner by factors of up to 4.9 and 5.0,respectively.The incompatibility-affected area in GCL is located within 0.1 m from the center of the hole in the GMB.The coupled increase in the hydraulic conductivity of GCL and pore water concentration impacts the flux and leakage in a short period of time.With GCL chemical incompatibility considered,advection may dominate the contaminant transport through GCL.

关键词： Geosvnthetic clay liner(GCL) Chemical incompatibility Leakage Contaminant transport Hvdraulic conductivity

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Classification and quantification of excavated soil and construction sludge:A case study in Wenzhou,China

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Frontiers of Structural and Civil Engineering 2022年第2期16卷 202-213页

作者： Qimeng GUO Liangtong ZHAN Yunyang SHEN Linbo WU yunmin chen MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Zhejiang UniversityHangzhou310058China College of Civil Engineering and Architecture Zhejiang Sci-Tech UniversityHangzhou310018China

With rapid urbanization in China,a large amount of excavated soil and construction sludge is being generated from geotechnical and underground engineering.For sustainable management of these construction wastes,it is essential to quantify their production first.The present study has attempted to classify the excavated soil and construction sludge according to their composition and geotechnical properties(particle size,water content,plasticity index).Based on these classifications,a new approach was proposed to quantify the production.The said approach was based on multi-source information,such as the urban topographic map,geological survey reports,urban master plan,and remote sensing images.A case study in Wenzhou city of China was also pursued to illustrate the validity of the newly developed approach.The research showed that in 2021–2025,the total excavated soils and construction sludge production in Wenzhou would reach 107.5×10^(6) and 81.7×10^(6) m^(3),respectively.Furthermore,the excavated soil was classified into the miscellaneous fill,crust clay,muddy clay and mud with silty sand.Likewise,the construction sludge was classified as liquid sludge and paste-like sludge.The classification and quantification can serve as guidance for disposal and recycling,thereby leading to high-level management of waste disposal.

关键词： excavated soil construction sludge geotechnical and underground engineering production classification

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Image-Aided Analysis of Ballast Particle Movement Along a High-Speed Railway

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Engineering 2023年第8期27卷 161-177页

作者： Xuecheng Bian Wenqing Cai Zheng Luo Chuang Zhao yunmin chen Key Laboratory of Soft Soils and Geoenvironmental Engineering Ministry of EducationDepartment of Civil EngineeringZhejiang UniversityHangzhou 310058China Center for Hypergravity Experimental and Interdisciplinary Research Zhejiang UniversityHangzhou 310058China

As a core infrastructure of high-speed railways,ballast layers constituted by graded crushed stones feature noteworthy particle movement compared with normal railways,which may cause excessive settlement and have detrimental effects on train operation.However,the movement behavior remains ambiguous due to a lack of effective measurement approaches and analytical methods.In this study,an image-aided technique was developed in a full-scale model test using digital cameras and a colorbased identification approach.A total of 1274 surface ballast particles were manually dyed by discernible colors to serve as tracers in the test.The movements of the surface ballast particles were tracked using the varied pixels displaying tracers in the photos that were intermittently taken during the test in the perpendicular direction.The movement behavior of ballast particles under different combinations of train speeds and axle loads was quantitatively evaluated.The obtained results indicated that the surface ballast particle movements were slight,mainly concentrated near sleepers under low-speed train loads and greatly amplified and extended to the whole surface when the train speed reached 360 km.h-1.Additionally,the development of ballast particle displacement statistically resembled its rotation.Track vibration contributed to the movements of ballast particles,which specifically were driven by vertical acceleration near the track center and horizontal acceleration at the track edge.Furthermore,the development trends of ballast particle movements and track settlement under long-term train loading were similar,and both stabilized at nearly the same time.The track performance,including the vibration characteristics,accumulated settlement,and sleeper support stiffness,was determined to be closely related to the direction and distribution of ballast particle flow,which partly deteriorated under high-speed train loads.

关键词： High-speed railway Full-scale model test Image-aided technique Ballast particle movement Track vibration Accumulated settlement

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Failure mechanisms in flexible electronics

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International Journal of Smart and Nano Materials 2023年第4期14卷 510-565页

作者： Zhehui Zhao Haoran Fu Ruitao Tang Bocheng Zhang yunmin chen Jianqun Jiang MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Zhejiang UniversityHangzhouChina Department of Civil Engineering Zhejiang UniversityHangzhouChina R&D department Wuxi Innosonics Medical Technology CoLtdWuxiChina R&D Department of devices and processes Jiashan Fudan InstituteJiaxingChina

The rapid evolution of flexible electronic devices promises to revolutionize numerous fields by expanding the applications of smart devices.Nevertheless,despite this vast potential,the reliability of these innovative devices currently falls short,especially in light of demanding operation environment and the intrinsic challenges associated with their fabrication techniques.The heterogeneity in these processes and environments gives rise to unique failure modes throughout the devices'lifespan.To significantly enhance the reliability of these devices and assure long-term performance,it is paramount to comprehend the underpinning failure mechanisms thoroughly,thereby,enabling,optimal design solutions.A myriad of investigative efforts have been dedicated to unravel these failure mechanisms,utilizing a spectrum of tools from analytical models,numerical methods,to advanced characterization methods.This review delves into the root causes of device failure,scrutinizing both the fabrication process and the operation environment.Next,We subsequently address the failure mechanisms across four commonly observed modes:strength failure,fatigue failure,interfacial failure,and electrical failure,followed by an overview of targeted characterization methods associated with each mechanism.Concluding with an outlook,we spotlight ongoing challenges and promising directions for future research in our pursuit of highly resilient flexible electronic devices.

关键词： Flexible electronic devices failure mechanisms characterization methods

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