摘要:
Real-time monitoring is an effective approach of early warning for landslide problems of mine slope. Analysis and evaluation were generally carried out from the aspects of soil moisture, groundwater level and slope deformation in the recent years. The volumetric water content under different rainfall intensities has always been the hot topic of geotechnical research. A large number of studies have shown that the occurrence of landslide often after reaching the overall saturation state. In current research, the seepage deformation of mine slope based on quasisaturated volumetric water content was studied by cylinder experiment and model test. The collapse time of the rainfall-induced landslide will also be forecasted to give early warning. In addition, different rainfall intensities and unsaturated permeability coefficient will also be summarized in this study. The initial quasi-saturated volumetric water content determined in this paper varies with rainfall intensity and physical characteristics of the sample. For these relations, it is necessary to understand the appearance of initial quasi-saturated volume water content as a permeability problem in unsaturated soils. The results shown that when considering soil deformation, the relationship between initial quasi-saturation and deformation is not always the same trend. The results of this research can provide a certain reference for the seepage of unsaturated soil.
作者机构:
[Wang, Peng; Li, Yongmei; Liu, Zhenzhong; Tan, Kaixuan; Tian, Yunting; Li, Chunguang] Univ South China, Sch Resource Environm & Safety Engn, Hengyang 421001, Peoples R China.;[Tan, Wanyu] Hunan City Univ, Sch Civil Engn, Yiyang 413000, Peoples R China.;[Huang, Wuyang] Cent South Explorat & Fdn Engn Co Ltd, Wuhan 430081, Peoples R China.
通讯机构:
[Kaixuan Tan] S;School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, China
关键词:
pitchblende;pyrite;acid leaching mining;shrinking particle model
摘要:
Abstract: In the process of acid in situ leaching of sandstone uranium ore, pyrite, which is a common associated mineral of pitchblende, would inevitably participate in the reaction. Therefore, it is important to study the influence of pyrite on the leaching kinetics of pitchblende. In this study, we compared the difference leaching rates of pitchblende in the systems of sulfuric acid–hydrogen peroxide, sulfuric acid–hydrogen peroxide–pyrite and sulfuric acid–pyrite and studied the influence of temperature and pyrite quantity on the leaching rate of pitchblende. The results show that the leaching process of pitchblende follows the shrinking particle model controlled by a chemical reaction, and the apparent activation energy Ea of the leaching reaction is (3.74 ± 0.40) × 10 kJ/mol. Pyrite itself cannot promote the dissolution of pitchblende; however, it can promote the leaching of pitchblende in the presence of an oxidizer. Increasing the quantity of pyrite in a certain range can increase the leaching rate of pitchblende, and the reaction order of pyrite is 0.36. Keywords: pitchblende; pyrite; acid leaching mining; shrinking particle model
摘要:
The main goal of this study is to investigate the effect of local corrosion at the mid-span region on the flexural behavior of HPS (high-performance steel) beams. Four Q550E HPS beams were designed and subjected to electrochemically accelerated corrosion. The 3D scanning technology was used to analyze the geometric characteristics of corrosion regions. After the four-point flexural test, the relationship between the degradation of flexural behavior and the corrosion ratio or corroded location (right side of pure bending section and lower half of pure bending section) was studied in details. The FE (finite element) model of corroded HPS beams was established and strictly verified by comparing with the tested results. Additionally, different heights and thicknesses of the corroded parts were considered in the FE models. Failure modes and bearing capacity degradation of the HPS beams caused by local corrosion were studied by analyzing above parameters. The results shows that the corrosion at the compressive flange of bending section has a greater influence on the ultimate bearing capacity than tension flange and web. The HPS beam corroded in right side of pure bending section has the most significant compressive flange buckling compared. The failure mode of HPS beams with corrosion in lower half of pure bending section changes from obviously compressive flange buckling and local web yielded to all web yielded with the increase of corrosion ratio. The influence of bottom flange corrosion on remaining critical buckling load of beam is slightly more significant than the ultimate load, but the influence degree of top flange corrosion on above two loads are basically the same.
期刊:
Journal of Materials Research and Technology,2022年19:1740-1758 ISSN:2238-7854
作者机构:
[Zhang, Genbao] Hunan City Univ, Coll Civil Engn, Yiyang 413000, Hunan, Peoples R China.;[Sun, Junbo] Chongqing Univ, Inst Smart City Chongqing Univ Liyang, Liyang 213300, Jiangsu, Peoples R China.;[Wang, Jiaqing] Nanjing Forestry Univ, Coll Civil Engn, Nanjing 210037, Jiangsu, Peoples R China.;[Zhang, Genbao] Hunan Engn Res Ctr Struct Safety & Disaster Preve, Yiyang 413000, Hunan, Peoples R China.;[Peng, Cheng; Jiang, Zhiwei] Nanjing Inst Technol, Sch Architectural Engn, Nanjing 211167, Peoples R China.
关键词:
Ecological jute fibers;Waste mineral powders;Sustainable materials;Self-compacting concrete;Microstructures
摘要:
Self-compacting concrete (SCC) mixtures requires a large amount of Portland cement and thus resulting in high CO2 emissions, expanding its application has been in question to environment sustainability. Accordingly, environmental-friendly alternatives to Portland cement in SCC mixtures are deemed necessary for the progress of SCC in construction. In this investigation, treated jute fibers and mineral powders were used to replace cement in SCC mixtures. The effects of fibers and powder contents, fiber treatment, and mineral powder types on the workability and mechanical properties of SCC mixtures were investigated through slump-flow, compressive, and flexural tests. A microstructure was conducted through scanning electron microscopy. It was concluded that mineral powders and jute fibers could significantly improve the workability and mechanical properties of SCC. The microstructure observations demonstrated that the proposed methods are capable of enhancing the mechanical properties of SCC with an optimum fiber content. Specifically, a combination of 0.1% jute fibers and 75 mu m zeolite powders were found to achieve the best mechanical properties. The relevant results supply fundamental reference and background for artificial intelligence and multi-function development for future infrastructure. (C) 2022 The Authors. Published by Elsevier B.V.
关键词:
Aging structure;Reliability;Resistance;Stochastic degradation;Random field;Gamma process
摘要:
Reasonable assessment of structural resistance degradation and reliability is the premise of formulating targeted maintenance strategy of aging structures. In this paper, a Gamma-based stochastic resistance degradation model is developed by incorporating the spatial degradation into a non-stationary degradation process. Then, based on the hazard-function-based reliability analysis method, a novel reliability assessment approach of aging structures is proposed considering stochastic degradation process of resistance. In addition, a simple case analysis of concrete bridge is used to illustrate the application of the proposed method. The case analysis results show that the resistance degradation presents great discontinuities in time and large spatial variability in the middle and later service period of structures. After 50 years of service, the resistance degradation coefficient considering the effect of spatial degradation process is 13.8% lower than that without consideration in this case. Parametric analyses show that an increase of the shape and scale parameters of mean resistance degradation model will significantly increase the cumulative failure probability of structures. This conclusion is also applicable to the non-stationary vehicle load effect model of case bridge. Additionally, ignoring the spatial variability of resistance degradation and the non-stationary nature of the vehicle load effect will overestimate the reliability of aging structures.
期刊:
Magazine of Concrete Research,2022年75(4):163-175 ISSN:0024-9831
通讯作者:
Yiming Yang
作者机构:
[Tang, Huang; Wang, Xinzhong; Yang, Yiming] Hunan City Univ, Sch Civil Engn, Yiyang, Hunan, Peoples R China.;[Yang, Yiming] Minist Educ, Key Lab Safety Control Bridge Engn, Changsha, Hunan, Peoples R China.;[Yang, Yiming] Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preve, Yiyang, Hunan, Peoples R China.
通讯机构:
[Yiming Yang ] S;School of Civil Engineering, Hunan City University, Yiyang, Hunan, China<&wdkj&>Key Laboratory of Safety Control of Bridge Engineering, Ministry of Education, Changsha, Hunan, China<&wdkj&>Hunan Engineering Research Center of Structural Safety and Disaster Prevention for Urban Underground Infrastructure, Hunan City University, Yiyang, Hunan, China
关键词:
corroded concrete structures;failure probability;scale of fluctuation;spatial variability;stochastic resistance deterioration
摘要:
A reasonable assessment of the probability of structural failure is essential to ensure the safe performance of corroded reinforced concrete (RC) structures. In this paper, a novel cross-sectional area loss model of corroded steel bars is proposed and the scale of fluctuation of some key parameters is estimated using the semi-variogram function method. A stochastic resistance deterioration model considering the effect of unbalanced corrosion and spatial variability and a time-dependent reliability assessment method of corroded concrete structures (CCSs) are then presented. A simple case analysis of a CCS is used to illustrate the application of the proposed method. The case analysis results show that the cumulative failure probability (CFP) is overestimated using the popular pit area model, while it is underestimated without considering the spatial variability of calculation parameters. Random field parameter analysis shows that an appropriate choice of the element size is very important for the safety evaluation of RC structures. Additionally, compared with a marine atmospheric environment, the CFP of a case study structure in tidal and splash environments was found to be increased by 20.15% and 70.40%, respectively, due to the gradual increase of corrosion current density. Of the three service environments, the splash environment thus has the greatest impact on structural failure probability.
通讯机构:
[Changbo Jiang] S;School of Hydraulic Engineering, Changsha University of Science & Technology, Changsha 410114, China<&wdkj&>Key Laboratory of Dongting Lake Aquatic Eco-Environmental Control and Restoration of Hunan Province, Changsha 410114, China
关键词:
GPM constellation satellites;IMERG V06;the Dongting Lake basin;satellite precipitation estimates;precision
摘要:
Abstract: Precipitation data from ground-based observatories in the Dongting Lake basin are often missing, resulting in large errors in surface precipitation data obtained by interpolation, which affects the accuracy of hydro-meteorological studies. Integrated Multisatellite Retrievals for Global Precipitation Measurement (IMERG) is the main high-resolution precipitation product, which is available to supplement measured missing data. To evaluate the applicability of this product in the Dongting Lake basin at multiple spatial and temporal scales, this paper analyzes daily, monthly, seasonal, annual, and extreme precipitation events of the three latest IMERG precipitation products (IPPs) (IMERG-F, IMERG-E, and IMERG-L) using eight statistical evaluation metrics. We find that the spatial and temporal performance of IMERG precipitation products varies over different time scales and topographic conditions. However, all three metrics (CC, RMSE, and RB) of the IMERG-F precipitation products outperform the IMERG-E and IMERG-L precipitation products for the same period. In the comparison of IMERG and TRMM (Tropical Rainfall Measuring Mission) precipitation products on monthly and seasonal scales, IMERG-F performed the best. IPPs can capture precipitation more accurately on seasonal scales and perform better in winter, indicating good detection of trace precipitation. Both high and low altitudes are not favorable for the satellite detection of extreme precipitation in both general and extreme precipitation events. Overall, the accuracy of IMERG-F with correction delay is slightly better than that of IMERG-E and IMERG-L without correction under near-real-time conditions, which is applicable in the Dongting Lake basin. However, the correction process also exacerbates overestimation of the precipitation extent. Keywords: GPM constellation satellites; IMERG V06; the Dongting Lake basin; satellite precipitation estimates; precision
作者机构:
[Yang, Rihua; Wang, Xinzhong; Yang, Yiming] Hunan City Univ, Sch Civil Engn, Yiyang 413000, Peoples R China.;[Yang, Rihua] Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preve, Yiyang 413000, Peoples R China.;[Zhang, Xuhui] Xiangtan Univ, Sch Civil Engn & Mech, Xiangtan 411105, Peoples R China.
通讯机构:
[Yiming Yang; Xuhui Zhang] S;School of Civil Engineering, Hunan City University, Yiyang 413000, China<&wdkj&>School of Civil Engineering and Mechanics, Xiangtan University, Xiangtan 411105, China
关键词:
bond slip;constructive model;experimental study;prestressed concrete beam;steel strands
摘要:
Abstract: In order to study the bond-slip constitutive model between prestressed tendons and concrete, the pull-out tests of single-strand and multi-strands specimens are carried out. The effect of the number of prestressed tendons on the failure mode, slip characteristics and concrete strain of the pull-out specimens are analyzed, and the constitutive models of bond-slip between for single- strand and multi-strand tendons are also proposed. The results show that the bond mechanism between steel strand and concrete is basically similar to that of deformed steel bar, but the slip process of steel strand along the axis direction is accompanied by rotation phenomenon because it is twisted. Moreover, compared with the single-strand prestressed tendon, the average ultimate bond stress of each tendon of the three-strand prestressed tendons decreases by 13.2%. In addition, the calculated result of the pull-out limit load for the single-strand prestressed tendon is only 2% higher than the experimental value, while the corresponding value of three-strand prestressed tendon is only 3.74% lower than the experimental value. This means that the proposed bond-slip models for single- strand and multi-strand tendons have high reliability. Keywords: prestressed concrete beam; steel strands; bond slip; experimental study; constructive model