摘要：
Characteristic of ground pressure in surrounding rock is generally considered as the theoretical basis of parameter optimization for stope structure and technology. To explore the feasibility of efficient method for the second-step downward route backfill stopes in Shanjin gold mine, various numerical simulation methods were used to investigate the effect of slab-wall backfill structure on stability of surrounding rock in downward route mining system. The maximum principal stress, artificial false roof stress, and displacement were analyzed to evaluate the level of ground pressure in different mining areas. These results indicate the optimized structural parameters for backfill stopes, which may also provide a low-cost way to achieve a high safety for downward route mining system.
摘要：
This paper presents a theoretical solution for bond-slip behavior of SRC interface based on experiment, numerical simulation, and theoretical derivation. Push-out tests of five specimens were firstly carried out, based on which, the simplified bond-slip model was proposed. The specimen was fabricated using the Q345H-shape steel (400 mm × 200 mm×13 mm × 8 mm) and C50 concrete (350 mm × 600 mm) with a bonding length of 500 mm. A FE model was established based on the bond-slip model to analyze the nonlinear bonding stress that are difficult to obtain from the experiment. The research shows that although the bonding stress in the elastic stage is not uniformly distributed, it is basically uniformly distributed when the ultimate bearing capacity is reached. It proves that assuming the average interfacial bonding stress under ultimate load to replace the maximum bonding stress is reasonable, which is crucial for designer to estimate interface bearing capacity and maximum bonding stress. Moreover, five different stages were obtained by the FE model analysis and the theoretical equations of bonding stress nonlinear distribution were obtained based on the boundary condition of each stage. The theoretical solution clearly showed the relationship between interface nonlinear stress distribution and influencing parameters including the bond area, elasticity modulus of material, section area of specimen, bond-slip constitutive model, and the external load. Based on the theoretical model, the influences of different parameters can be directly obtained without conducting further experiments and establishing different FE models.
摘要：
Evaporative cooling (EC) technology can effectively improve the energy efficiency of the mechanical vapor compression (MVC) system by enhancing the heat exchange capacity of its condenser. However, the current evaporative-cooling condenser system is usually only equipped with a single-stage evaporative cooler as the precooling unit, and these designs are mainly suitable for hot-dry conditions. In this study, three hybrid air-conditioning systems with different two-stage evaporative-cooling condenser configurations were proposed, one is single-condenser type and the other two are dual-condenser type, which are used to improve the exergy performance and adaptability of the evaporative condenser system under hot-humid climates. Then, the all systems were modeled via the distributed parametric method and analyzed comparatively based on the exergy method. A suitable exergy reference temperature at air saturation was discussed. Finally, the effect of four key parameters (ambient temperature and relative humidity, outdoor airflow rate and room heat load) was studied. The results showed that under the high temperature, relative humidity or room heat load conditions, the hybrid systems have a low exergy efficiency ratio (EXR) and high exergy efficiency (eta x,OEC). x , OEC ). Among them, the newly countercurrent dual-condenser configuration (MVC-TSEC(C)) exhibits the best exergy performance under most hot-humid conditions. Compared to the conventional MVC system, the EXR and eta x , OEC of MVC-TSEC(C) increased by at most 35.0 % and 78.2 %, respectively. Moreover, its components like compressor, condenser and expansion valve have the maximum reduction rates of exergy destruction of 43.5 %, 17.2 % and 55.3 %, respectively.
期刊：
Journal of Central South University .,2024年31(9):3168-3186 ISSN：2095-2899
通讯作者：
Dai, Gong-lian;Ge, H
作者机构：
[Wang, Fen] Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.;[Ge, Hao; Dai, Gong-lian; He, Chang-lin; Dai, GL] Cent South Univ, Sch Civil Engn, Changsha 410074, Peoples R China.;[Rao, Hui-ming] Southeast Coastal Railway Fujian Co Ltd, Fuzhou 350013, Peoples R China.
通讯机构：
[Ge, H ; Dai, GL] C;Cent South Univ, Sch Civil Engn, Changsha 410074, Peoples R China.
关键词：
cable-stayed bridges;representative temperature;gradient boosted regression trees (GBRT) method;field test;limited measured data
摘要：
Cable-stayed bridges have been widely used in high-speed railway infrastructure. The accurate determination of cable's representative temperatures is vital during the intricate processes of design, construction, and maintenance of cable-stayed bridges. However, the representative temperatures of stayed cables are not specified in the existing design codes. To address this issue, this study investigates the distribution of the cable temperature and determinates its representative temperature. First, an experimental investigation, spanning over a period of one year, was carried out near the bridge site to obtain the temperature data. According to the statistical analysis of the measured data, it reveals that the temperature distribution is generally uniform along the cable cross-section without significant temperature gradient. Then, based on the limited data, the Monte Carlo, the gradient boosted regression trees (GBRT), and univariate linear regression (ULR) methods are employed to predict the cable's representative temperature throughout the service life. These methods effectively overcome the limitations of insufficient monitoring data and accurately predict the representative temperature of the cables. However, each method has its own advantages and limitations in terms of applicability and accuracy. A comprehensive evaluation of the performance of these methods is conducted, and practical recommendations are provided for their application. The proposed methods and representative temperatures provide a good basis for the operation and maintenance of in-service long-span cable-stayed bridges.
摘要：
In this study, waste shrimp shell and phosphorous-containing wastewater were used to synthesize calciumdecorated biochar modified with phosphorus (Ca -BC -P) and utilized to remove uranium from aqueous solutions. The results from static adsorption experiment demonstrated that Ca -BC -P exhibited good U(VI) adsorption performance in acidic environments, with a maximum theoretical adsorption capacity of 1074.29 mg g -1 . The adsorption behavior perfectly fit Langmuir isotherm and the pseudo -second -order kinetic models, which revealed the nature of monolayer chemical adsorption by Ca -BC -P. Thermodynamic analysis showed that this process was spontaneous and endothermic. Ca -BC -P also displayed excellent selectivity and could be reused for several times while keeping a high U(VI) removal efficiency. When treating simulated acidic uranium mine wastewater, the removal efficiency of uranium reached 99.9 % with Ca -BC -P. The U(VI) removal mechanism was attributed to the precipitation of Ca(UO 2 ) 2 (PO 4 ) 2 & sdot; 6H 2 O and surface complexation, nHAP on the surface of Ca -BC -P played a pivotal role during the adsorption process. Therefore, Ca -BC -P could be prepared economically and showed great potential for efficiently remove uranium from mining wastewater.
期刊：
Environmental Science and Pollution Research,2024年:1-14 ISSN：0944-1344
通讯作者：
Lu, Yue
作者机构：
[Liangqin Wang; Haichao Sha; Taotao Zeng; Haidu Nong] Hunan Province Key Laboratory of Pollution Control and Resources Reuse Technology, University of South China, Hengyang, 421001, Hunan, China;[Lin Tang; Taotao Zeng; Qingqing Xie] College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China;[Lin Tang; Taotao Zeng; Qingqing Xie] Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, Hunan, China;[Yue Lu] College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China. yuelu@hnu.edu.cn;[Yue Lu] Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, Hunan, China. yuelu@hnu.edu.cn
通讯机构：
[Lu, Yue] C;College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China.;Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, Hunan, China.
关键词：
Heavy metal;Lead–zinc mining;Microbial community;Microbial interaction;Mine soil
摘要：
Understanding the microbial community structure in soil contaminated with heavy metals (HMs) is a precondition to conduct bioremediation in mine soil. Samples were collected from a typical lead-zinc (Pb-Zn) mine to assess the microbial community structure of the HMs concentrated in the soil. The goal was to analyze the bacterial and fungal community structures and their interactions using the 16S rRNA genes and internal transcribed spacer high-throughput sequencing. Analyses at different sampling sites showed that contamination with HMs significantly reduced the bacterial richness and diversity but increased that of the fungi. The predominant bacteria genera of Acidobacteriales, Gaiellales, Anaerolineaceae, Sulfurifustis, and Gemmatimonadaceae, and predominant fungal genera of Sordariomycetes, Talaromyces, and Mortierella were assumed as HM resistant genera in Pb-Zn mining area. The pH effect on the bacterial and fungal communities was opposite to those of Cd, Pb, and Zn. This study offers comprehensive outlooks for bacterial and fungal community structures upon multiple HM stresses in the soil around a typical Pb-Zn mine area.
期刊：
Geotechnical and Geological Engineering,2024年42(7):5651-5669 ISSN：0960-3182
通讯作者：
Xiqi Liu
作者机构：
[Wenzhao Chen; Chunming Qi] School of Civil Engineering, University of South China, Hengyang, China;[Xiqi Liu; Yan Chang; Heng Deng] Pearl River Water Resources Research Institute, Guangzhou, China;[Gang Wang] School of Civil Engineering, Shaoxing University, Shaoxing, China;[Bingwen Gong] China Seventh Bureau of Water Conservancy and Hydro Power Engineering, Chengdu, China;[Rong Hu] School of Civil Engineering, University of South China, Hengyang, China<&wdkj&>Pearl River Water Resources Research Institute, Guangzhou, China
通讯机构：
[Xiqi Liu] P;Pearl River Water Resources Research Institute, Guangzhou, China
关键词：
High temperature;Uniaxial compression;Basalt;Damage evolution;AE energy evolution
摘要：
To study the damage and acoustic emission (AE) energy evolution of basalt under high temperature, a series of tests under uniaxial stress are carried out on basalt heated at 25 °C, 200 °C, 400 °C, 600 °C, 800 °C and 1000 °C. Through the comprehensive analysis of AE parameters such as absolute energy and amplitude, the AE characteristics and damage evolution laws of basalt were explored. The results show that high temperature has a significant effect on the characteristics of rock stress–strain curve. With the increase of temperature, the compaction stage of the curve becomes longer, the plasticity increases, and the peak strength of basalt decreases. The higher the heat treatment temperature, the faster the strength decreases, and the strength decreases by 63.91% at 1000 °C. The AE localization points converge from the dispersed state to the aggregated state. With the increase of temperature, the period of convergent nucleation of the AE localization sites is advanced, high amplitude AE signals shifted from a concentrated distribution near the peak stress to a discrete distribution throughout the entire process. The heat treatment of the rock has an additive effect on the burstiness. 600–800 °C can be used as the threshold temperature of basalt to transform from brittle failure to plastic failure. The high temperature effect is responsible for the transition of the AE cumulative absolute energy at 400–600 °C. The influence of high temperature on damage evolution is discussed. The initial damage increases exponentially after 800 °C. With the increase of temperature, the evolution rate of damage variable becomes faster and gradually changes from linear to nonlinear.
摘要：
本文以废玻璃粉和偏高岭土为原料，通过碱激发制备地质聚合物胶砂，研究了不同水玻璃模数碱激发剂和液固比对废玻璃粉-偏高岭土地质聚合物胶砂流动度和力学性能的影响，并通过X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、热重-差示扫描热(TG-DSC)、压汞法(MIP)及扫描电子显微镜(SEM)分析了地质聚合物胶砂的晶体结构、热化学性质、孔隙结构及微观形貌等。结果表明，水玻璃模数和液固比对地质聚合物胶砂流动度和力学性能有较明显的影响。随着水玻璃模数的增大，地质聚合物胶砂的流动度和强度先增加后减少，水玻璃模数为1.25时激发剂对材料的激发效果最佳，提高了地质聚合物的反应程度，生成了更多水化产物，优化了基体的孔隙结构，28 d抗压强度达到43.0 MPa；液固比的增大改善了地质聚合物胶砂的流动度，但降低了抗压强度，对孔隙结构产生了负面作用；XRD、FTIR及TG-DSC结果显示地质聚合物中废玻璃参与了水化反应，提供了Ca2+，促进了水化硅酸钙(C-S-H)和水化硅铝酸钙(C-A-S-H)凝胶的生成。 您的浏览器不支持 audio 元素。AI语音播报 Waste glass powder and metakaolin were used to prepare geopolymer mortar. The effects of alkali activator with different sodium silicate modulus and liquid-solid ratios on the fluidity and mechanical properties of the waste glass powder-metakaolin geopolymer mortar were investigated, and the crystal structure, thermochemistry, pore structure, and micromorphology of the geopolymer mortar were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric-differential scanning thermal (TG-DSC), mercury in piezoelectricity (MIP), and scanning electron microscopy (SEM). The results show that the sodium silicate modulus and liquid-solid ratio have more obvious effects on the fluidity and mechanical properties of the geopolymer mortar. With the increase of sodium silicate modulus, the fluidity and strength of geopolymer mortar increase first and then decrease. When the sodium silicate modulus is 1.25, the alkali activator has the best excitation effect on the material, which increases the degree of reaction of the geopolymer, generates more hydration products, optimizes the pore structure of the matrix, and the compressive strength of 28 d reaches 43.0 MPa. The increase of liquid-solid ratio improves the fluidity of the geopolymer mortar, but decreases the compressive strength and has a negative effect on the pore structure. Moreover, the XRD, FTIR and TG-DSC results show that the waste glass in the geopolymer participates in the hydration reaction, provides Ca2+, and promotes the generation of C-S-H and C-A-S-H gels.
摘要：
Four severe nuclear accident scenarios have been identified for operating nuclear power plants (ONPPs). However, there is a research gap in predicting the mid-long-term radiation doses for these scenarios. This study aims to address this gap by proposing a novel approach for predicting the mid-long-term radiation dose in the case of a hypothetical short-term station blackout (STSBO) scenario, one of the aforementioned scenarios. Firstly, the Weather Research and Forecasting (WRF) model was coupled with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) (WRF-HYSPLIT) model to establish an atmospheric transport and diffusion model for airborne radionuclides, and the regularity of the atmospheric transport and diffusion for the airborne radionuclides was determined. Subsequently, the Residual Radioactive Material Guidelines (RESRAD) OFFSITE (RESRAD-OFFSITE) code was utilized to establish a radiation dose model for predicting the mid-long-term radiation dose resulting from the airborne radionuclides, and the evolution of the mid-long-term radiation dose was analyzed. Finally, the proposed approach was applied to an ONPP, and the results were used to predict the mid-long-term public radiation dose. The results indicated that the total radiation dose would be lower than the dose limit recommended by the International Commission on Radiological Protection (1 mSv/yr) from the second month to the 100th year after the hypothetical STSBO nuclear accident, and the total radiation dose would decrease slowly over time. Recommendations are made for offsite emergency response measures. These research findings can assist ONPPs in analyzing their environmental impacts in the event of an STSBO scenario.
