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Effects of synthetic site water on bentonite-concrete system for a potential nuclear waste repository

Journal of Rock Mechanics and geotechnical engineering 2024年第9期16卷 3786-3797页

作者： Zhao Sun Yong-Gui Chen Wei-Min Ye Qiong Wang Dong-Bei Wu Zhen-Yu Yin Key Laboratory of geotechnical and Underground engineering of Ministry of Education Department of Geotechnical EngineeringTongji UniversityShanghai200092China Department of Civil and environmental engineering The Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina School of Chemical Science and engineering Tongji UniversityShanghai200092China

In high-level nuclear waste(HLW)repositories,concrete and compacted bentonite are designed to be employed as buffer materials,which may raise a problem of interactions between concrete and *** interactions would lead to mineralogy transformation and buffer performance decay of bentonite under the near field environment conditions in a repository.A small-scale experimental setup was established to simulate the concrete-bentonite-site water interaction system from a potential nuclear waste repository in *** types of mortars were prepared to correspond to the concrete at different degradation *** results permit the determination of the following:(1)The macroproperties of Gaomiaozi(GMZ)bentonite(*** pressure,permeability,the final dry density,and water content of reacted samples);(2)The composition evolution of fluids from the synthetic site water-concrete-bentonite interaction systems;(3)The sample characterization including Fourier transform infrared spectroscopy(FTIR)and X-ray powder diffraction(XRD).Under the infiltration of the synthesis Beishan site water(BSW),the swelling pressure of bentonite decreases slowly with time after reaching its second swelling *** flux decreases with time during the infiltrations,and it tends to be stable after more than 120 *** to the cation exchange reactions in the BSW-concrete-bentonite systems,the divalent cations(Ca and Mg)were consumed,and the monovalent cations(Na and K)were *** dissolution of minerals in the bentonite such as albite causes Si increasing in the pore *** was concluded that the hydro-mechanical property degradation of bentonite takes place when it comes into contact with concrete mortar,even under low-pH groundwater *** soil dispersion,the uneven water content,and the uneven dry density in bentonite samples may partly contribute to the swelling decay of ***,the direct contact with concrete has an obvious effect on the performance

关键词： Mock-up device GMZ bentonite Site water-concrete-bentonite system Geochemistry Buffer performance

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A modified smoothed particle hydrodynamics method considering residual stress for simulating failure and its application in layered rock mass

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Journal of Mountain Science 2024年第6期21卷 2091-2112页

作者： XIA Chengzhi SHI Zhenming KOU Huanjia Department of geotechnical engineering College of Civil EngineeringTongji UniversityShanghai 200092China Key Laboratory of geotechnical and Underground engineering of Ministry of Education Tongji UniversityShanghai 200092China

Residual strength is an indispensable factor in evaluating rock fracture,yet the current Smoothed Particle Hydrodynamics(SPH)framework rarely considers its influence when simulating *** improved cracking strategy considering residual stress in the base bond SPH method was proposed to simulate failures in layered rocks and slopes and verified by experimental results and other simulation methods(i.e.,the discrete element method).Modified Mohr–Coulomb failure criterion was applied to distinguish the mixed failure of tensile and *** fracture markψwas introduced to improve the kernel function after tensile damage,and the calculation of residual stress after the damage was derived after shear *** simulations were carried out to evaluate its performance under different stress and scale conditions and to verify its effectiveness in realistically reproducing crack initiation and propagation and coalescence,even fracture and *** results indicate that the improved cracking strategy precisely captures the fracture and failure pattern in layered rocks and rock *** residual stress of brittle tock is correctly captured by the improved SPH *** improved SPH method that considers residual strength shows an approximately 13%improvement in accuracy for the safety factor of anti-dip layered slopes compared to the method that does not consider residual strength,as validated against analytical *** infer that the improved SPH method is effective and shows promise for applications to continuous and discontinuous rock masses.

关键词： Smoothed particle hydrodynamics Cracking strategy Residual stress Layered rock Crack propagation

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Development of gradient boosting-assisted machine learning data-driven model for free chlorine residual prediction

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Frontiers of environmental Science & engineering 2024年第2期18卷 35-46页

作者： Wiley Helm Shifa Zhong Elliot Reid Thomas Igou Yongsheng Chen School of Civil and environmental engineering Georgia Institute of TechnologyAtlantaGA 30332USA School of Ecological and environmental Sciences East China Normal UniversityShanghai 200241China

Chlorine-based disinfection is ubiquitous in conventional drinking water treatment (DWT) and serves to mitigate threats of acute microbial disease caused by pathogens that may be present in source water. An important index of disinfection efficiency is the free chlorine residual (FCR), a regulated disinfection parameter in the US that indirectly measures disinfectant power for prevention of microbial recontamination during DWT and distribution. This work demonstrates how machine learning (ML) can be implemented to improve FCR forecasting when supplied with water quality data from a real, full-scale chlorine disinfection system in Georgia, USA. More precisely, a gradient-boosting ML method (CatBoost) was developed from a full year of DWT plant-generated chlorine disinfection data, including water quality parameters (e.g., temperature, turbidity, pH) and operational process data (e.g., flowrates), to predict FCR. Four gradient-boosting models were implemented, with the highest performance achieving a coefficient of determination, R2, of 0.937. Values that provide explanations using Shapley’s additive method were used to interpret the model’s results, uncovering that standard DWT operating parameters, although non-intuitive and theoretically non-causal, vastly improved prediction performance. These results provide a base case for data-driven DWT disinfection supervision and suggest process monitoring methods to provide better information to plant operators for implementation of safe chlorine dosing to maintain optimum FCR.

关键词： Machine learning Data-driven modeling Drinking water treatment Disinfection Chlorination

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Fatigue properties and damage constitutive model of salt rock based on CT scanning

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International Journal of Mining Science and Technology 2024年第2期34卷 245-259页

作者： Junbao Wang Xiao Liu Qiang Zhang Xinrong Liu Zhanping Song Shijin Feng College of Civil engineering Xi’an University of Architecture and TechnologyXi’an 710055China Shaanxi Key Lab of geotechnical and Underground Space engineering Xi’an 710055China School of Civil engineering Chongqing UniversityChongqing 400045China Department of geotechnical engineering Tongji UniversityShanghai 200092China

To investigate the macroscopic fatigue properties and the mesoscopic pore evolution characteristics of salt rock under cyclic loading,fatigue tests under different upper-limit stresses were carried out on salt rock,and the mesoscopic pore structures of salt rock before and after fatigue tests and under different cycle numbers were measured using CT scanning *** on the test results,the effects of the cycle number and the upper-limit stress on the evolution of cracks,pore morphology,pore number,pore volume,pore size,plane porosity,and volume porosity of salt rock were *** failure path of salt rock specimens under cyclic loading was analyzed using the distribution law of plane *** damage variable of salt rock under cyclic loading was defined on basis of the variation of volume porosity with cycle *** order to describe the fatigue deformation behavior of salt rock under cyclic loading,the nonlinear Burgers damage constitutive model was further *** results show that the model established can better reflect the whole development process of fatigue deformation of salt rock under cyclic loading.

关键词： Salt rock Cyclic loading CT scanning Mesoscopic pore evolution Constitutive model

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Degradation of iopamidol in the permanganate/sulfite process:Evolution of iodine species and effect on the subsequent formation of disinfection by-products

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Journal of environmental Sciences 2024年第1期135卷 345-352页

作者： Yimin Lin Hongyu Dong Yating Zhu Gongming Zhou Junlian Qiao Xiaohong Guan State Key Laboratory of Pollution Control and Resources Reuse College of Environmental Science and EngineeringTongji UniversityShanghai 200092China Department of environmental Science School of Ecological and Environmental SciencesEast China Normal UniversityShanghai 200241China

Permanganate/sulfite(Mn(VII)/S(IV))process is a promising pre-oxidation technology for sequestering the emerging organic contaminants in drinking water treatment ***(IPM),a representative of iodinated X-ray contrast media,has been widely detected in water sources and has the risk of forming iodinated disinfection byproducts(I-DBPs)in water treatment *** this study,we investigated the evolution of iodine species during the IPM degradation by the Mn(VII)/S(IV)process and its effect on the subsequent formation of I-DBPs during chlorination at pH 7.0 and *** could be effectively degraded in the Mn(VII)/S(IV)process at environmentally relevant pH(pH 7.0 and 8.0).The results of quenching and competitive oxidation kinetic experiments revealed that SO^(·-)_(4)was the major reactive oxidizing species contributing to the degradation of IPM whereas the contributions of HO·and reactive manganese species were negligible in the Mn(VII)/S(IV)process.I–and IO–3were generated while no HOI was detected during the degradation of IPM in the Mn(VII)/S(IV)*** effects of IPM oxidation by Mn(VII)/S(IV)on the subsequent formation of chlorinated disinfection by-products(Cl-DBPs)during chlorination were related to the category of *** pre-oxidation of IPM by Mn(VII)/S(IV)resulted in the generation of I-DBPs during the disinfection process although no I-DBPs were detected if no pre-oxidation was *** finding of this study suggested that attention should be paid to the toxicity of DBPs when water containing iodinated organic contaminants is treated by Mn(VII)/S(IV)process or other pre-oxidation technologies.

关键词： Permanganate/sulfite Iopamidol Sulfate radical Iodinated disinfection byproducts Pre-oxidation

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Thermo-hydro-mechanical (THM) coupled simulation of the land subsidence due to aquifer thermal energy storage (ATES) system in soft soils

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Journal of Rock Mechanics and geotechnical engineering 2024年第6期16卷 1952-1966页

作者： Yang Wang Fengshou Zhang Fang Liu Department of geotechnical engineering College of Civil EngineeringTongji UniversityShanghai200092China Key Laboratory of geotechnical and Underground engineering of Ministry of Education Tongji UniversityShanghai200092China Shanghai engineering and Technology Research Center of Shallow Geothermal Energy Shanghai200072China

Aquifer thermal energy storage(ATES)system has received attention for heating or cooling ***,it is well known that land subsidence becomes a major environmental concern for ATES ***,the effect of temperature on land subsidence has received practically no attention in the *** paper presents a thermo-hydro-mechanical(THM)coupled numerical study on an ATES system in Shanghai,*** water wells were installed for seasonal heating and cooling of an agriculture *** target aquifer at a depth of 74e104.5 m consisted of alternating layers of sand and silty sand and was covered with *** level,temperature,and land subsidence data from 2015 to 2017 were collected using field monitoring *** by data,we constructed a field scale three-dimensional(3D)model using TOUGH(Transport of Unsaturated Groundwater and Heat)and FLAC3D(Fast Lagrangian Analysis of Continua)equipped with a thermo-elastoplastic constitutive *** effectiveness of the numerical model was validated by field *** model was used to reproduce groundwater flow,heat transfer,and mechanical responses in porous media over three years and capture the thermo-and pressure-induced land *** results show that the maximum thermoinduced land subsidence accounts for about 60%of the total *** thermo-induced subsidence is slightly greater in winter than that in summer,and more pronounced near the cold well area than the hot well *** study provides some valuable guidelines for controlling land subsidence caused by ATES systems installed in soft soils.

关键词： Aquifer thermal energy storage(ATES) Land subsidence TOUGH-FLAC3D Thermo-elastoplastic constitutive model

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Roof collapse mechanism of weak surrounding rock for deep-buried tunnels under high geostress conditions

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Journal of Mountain Science 2024年第7期21卷 2408-2426页

作者： ZHANG Qi GUO Xiaokang YAN Zhiguo LEI Zhongdai SHEN Yixin School of Civil engineering Southeast UniversityNanjing 211189China Department of geotechnical engineering Tongji UniversityShanghai 200092China

High geostress,a typical attribute of tunnels located at significant depths,is crucial in causing stress-induced failure and influencing the stability of the tunnel *** study developed an analytical method for the failure mechanism that occurs in deep-buried tunnel roofs,taking into account the influence of *** limit analysis theory was utilized for deriving analytical solutions about the geometry of the collapsing surface and the limit supporting *** collapsing surface obtained by the analytical solution was validated by the findings of the physical model test,which shows a high level of agreement with the actual *** extensive investigation was done to explore the effects of the lateral pressure coefficients,the tunnel buried depth,the geological conditions of the surrounding rock,the long-short axis ratio,and the size of the tunnel *** findings indicate that an increase in the lateral pressure coefficient from 0.5 to 1.5 results in a reduction in the height of the collapsing zone by 2.08 m and the width of the collapsing zone by 1.15 m,while simultaneously increases the limit supporting pressure by 18.9%.The proposed upper bound method accurately determines the limit supporting pressure and the geometry of the collapsing surface,which aligns well with the results acquired through numerical modelling and on-site monitoring in actual engineering *** proposed analytical method can serve as a reference for similar crown failure issues of deep-buried tunnels.

关键词： Geostress Deep-buried tunnels Collapse mechanism Pressure arch Limit analysis HoekBrown criterion

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Periodic signal extraction of GNSS height time series based on adaptive singular spectrum analysis

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Geodesy and Geodynamics 2024年第1期15卷 50-60页

作者： Chenfeng Li Peibing Yang Tengxu Zhang Jiachun Guo Three Gorges geotechnical engineering Co.Ltd.(Wuhan) Wuhan 430074China College of Resources and environmental Science and engineering Hubei University of Science and TechnologyXian©ning 437100China College of Civil engineering Anhui Jianzhu UniversityHefei 230601China

Singular spectrum analysis is widely used in geodetic time series ***,when extracting time-varying periodic signals from a large number of Global Navigation Satellite System(GNSS)time series,the selection of appropriate embedding window size and principal components makes this method cumbersome and *** improve the efficiency and accuracy of singular spectrum analysis,this paper proposes an adaptive singular spectrum analysis method by combining spectrum analysis with a new trace *** running time and correlation analysis indicate that the proposed method can adaptively set the embedding window size to extract the time-varying periodic signals from GNSS time series,and the extraction efficiency of a single time series is six times that of singular spectrum *** method is also accurate and more suitable for time-varying periodic signal analysis of global GNSS sites.

关键词： GNSS Time series Singular spectrum analysis Trace matrix Periodic signal

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Surrogate modeling for unsaturated infiltration via the physics and equality-constrained artificial neural networks

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Journal of Rock Mechanics and geotechnical engineering 2024年第6期16卷 2282-2295页

作者： Peng Lan Jingjing Su Sheng Zhang School of Civil engineering Central South UniversityChangsha410075China Discipline of Civil Surveying and Environmental EngineeringPriority Research Centre for Geotechnical Science and EngineeringThe University of NewcastleCallaghanNSW2308Australia Qinghai University Qinghai810016China

Machine learning(ML)provides a new surrogate method for investigating groundwater flow dynamics in unsaturated *** pure data-driven methods(*** neural network,DNN)can provide rapid predictions,but they do require sufficient on-site data for accurate training,and lack interpretability to the physical processes within the *** this paper,we provide a physics and equalityconstrained artificial neural network(PECANN),to derive unsaturated infiltration solutions with a small amount of initial and boundary *** takes the physics-informed neural network(PINN)as a foundation,encodes the unsaturated infiltration physical laws(*** equation,RE)into the loss function,and uses the augmented Lagrangian method to constrain the learning process of the solutions of RE by adding stronger penalty for the initial and boundary *** unsaturated infiltration cases are designed to test the training performance of PECANN,***-dimensional(1D)steady-state unsaturated infiltration,1D transient-state infiltration,two-dimensional(2D)transient-state infiltration,and 1D coupled unsaturated infiltration and *** predicted results of PECANN are compared with the finite difference solutions or analytical *** results indicate that PECANN can accurately capture the variations of pressure head during the unsaturated infiltration,and present higher precision and robustness than DNN and *** is also revealed that PECANN can achieve the same accuracy as the finite difference method with fewer initial and boundary training ***,we investigate the effect of the hyperparameters of PECANN on solving RE *** provides an effective tool for simulating unsaturated infiltration.

关键词： Richards equation(RE) Unsaturated infiltration Data-driven solutions Numerical modeling Machine learning(ML)

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Simultaneous Degradation, Dehalogenation, and Detoxification of Halogenated Antibiotics by Carbon Dioxide Radical Anions

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engineering 2024年第6期37卷 78-86页

作者： Yanzhou Ding Xia Yu Shuguang Lyu Huajun Zhen Wentao Zhao Cheng Peng Jiaxi Wang Yiwen Zhu Chengfei Zhu Lei Zhou Qian Sui State environmental Protection Key Laboratory of environmental Risk Assessment and Control on Chemical Process School of Resources and Environmental EngineeringEast China University of Science and TechnologyShanghai 200237China Shanghai Institute of Pollution Control and Ecological Security Shanghai 200092China State Key Laboratory of Pollution Control and Resource Reuse College of Environmental Science and EngineeringTongji UniversityShanghai 200092China Shanghai Academy of environmental Sciences Shanghai 200233China

Despite the extensive application of advanced oxidation processes(AOPs)in water treatment,the efficiency of AOPs in eliminating various emerging contaminants such as halogenated antibiotics is constrained by a number of *** moieties exhibit strong resistance to oxidative radicals,affecting the dehalogenation and detoxification *** address these limitations of AOPs,advanced reduction processes(ARPs)have been ***,a novel nucleophilic reductant—namely,the carbon dioxide radical anion(CO_(2)^(·-))—is introduced for the simultaneous degradation,dehalogenation,and detoxification of florfenicol(FF),a typical halogenated *** results demonstrate that FF is completely eliminated by CO_(2)^(·-),with approximately 100%of Cland 46%of Freleased after 120 min of *** detoxification is observed,which exhibits a linear response to the release of free inorganic halogen ions(R^(2)=0.97,p75%)in degrading a series of halogenated antibiotics,including chloramphenicol(CAP),thiamphenicol(THA),diclofenac(DLF),triclosan(TCS),and ciprofloxacin(CIP).The system shows high tolerance to the pH of the solution and the presence of natural water constituents,and demonstrates an excellent degradation performance in actual groundwater,indicating the strong application potential of CO_(2)^(·-)-based ARPs in real ***,this study elucidates the feasibility of CO_(2)^(·-)for the simultaneous degradation,dehalogenation,and detoxification of halog

关键词： Carbon dioxide radical anions Advanced reduction processes Halogenated antibiotics Dehalogenation Detoxification

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