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A new method of studying collapsibility of loess

Yuanqing ZHU , Zhenghan CHEN ,

《结构与土木工程前沿(英文)》 2009年 第3卷 第3期   页码 305-311 doi: 10.1007/s11709-009-0040-3

摘要: A new triaxial testing system that could control suction in wetting-induced collapsible tests was successfully developed to study the suction effects on wetting-induced collapsible deformation. The pedestal of the triaxial cell was made up of two parts, and the equipment not only could control suction but also could make water accessible to soil. A pressure/volume-controlled equipment was combined with the triaxial system to measure the water volume absorbed by samples accurately and to add pressure on water to filtrate into the sample. The apparatus could measure volume change precisely and keep the deviator stress unvaried, as well as measure the volume of water filtrating into the samples exactly. A triaxial collapsible testing procedure was described using the new apparatus for undisturbed collapsible loess with controlled suction. Furthermore, a series of double triaxial collapsible tests were conducted under different suctions and the same net cell pressure, and tests under different net cell pressures and the same suction were also done. It was indicated that the collapsible deformation increased with the increasing suction, and the effect of the net cell pressure on collapsible deformation was remarkable. The new triaxial apparatus was a useful facility to study the collapsible behavior of loess.

关键词: triaxial apparatus for collapsible soils     controlled suction     pressure/volume controlled equipment     double triaxial collapsible test     single triaxial collapsible test    

Crushed rocks stabilized with organosilane and lignosulfonate in pavement unbound layers: Repeated load triaxial

Diego Maria BARBIERI, Inge HOFF, Chun-Hsing HO

《结构与土木工程前沿(英文)》 2021年 第15卷 第2期   页码 412-424 doi: 10.1007/s11709-021-0700-5

摘要: The creation of the new “Ferry-Free Coastal Highway Route E39” in southwest Norway entails the production of a remarkable quantity of crushed rocks. These resources could be beneficially employed as aggregates in the unbound courses of the highway itself or other road pavements present nearby. Two innovative stabilizing agents, organosilane and lignosulfonate, can significantly enhance the key properties, namely, resilient modulus and resistance against permanent deformation, of the aggregates that are excessively weak in their natural state. The beneficial effect offered by the additives was thoroughly evaluated by performing repeated load triaxial tests. The study adopted the most common numerical models to describe these two key mechanical properties. The increase in the resilient modulus and reduction in the accumulated vertical permanent deformation show the beneficial impact of the additives. Furthermore, a finite element model was created to simulate the repeated load triaxial test by implementing nonlinear elastic and plastic constitutive relationships.

关键词: organosilane     lignosulfonate     crushed rocks     pavement unbound layers     repeated load triaxial test     finite element analysis    

A miniature triaxial apparatus for investigating the micromechanics of granular soils with

Zhuang CHENG, Jianfeng WANG, Matthew Richard COOP, Guanlin YE

《结构与土木工程前沿(英文)》 2020年 第14卷 第2期   页码 357-373 doi: 10.1007/s11709-019-0599-2

摘要: The development of a miniature triaxial apparatus is presented. In conjunction with an X-ray micro-tomography (termed as X-ray μCT hereafter) facility and advanced image processing techniques, this apparatus can be used for investigation of the micro-scale mechanical behavior of granular soils under shear. The apparatus allows for triaxial testing of a miniature dry sample with a size of (diameter height). triaxial testing of a 0.4–0.8 mm Leighton Buzzard sand (LBS) under a constant confining pressure of 500 kPa is presented. The evolutions of local porosities (i.e., the porosities of regions associated with individual particles), particle kinematics (i.e., particle translation and particle rotation) of the sample during the shear are quantitatively studied using image processing and analysis techniques. Meanwhile, a novel method is presented to quantify the volumetric strain distribution of the sample based on the results of local porosities and particle tracking. It is found that the sample, with nearly homogenous initial local porosities, starts to exhibit obvious inhomogeneity of local porosities and localization of particle kinematics and volumetric strain around the peak of deviatoric stress. In the post-peak shear stage, large local porosities and volumetric dilation mainly occur in a localized band. The developed triaxial apparatus, in its combined use of X-ray μCT imaging techniques, is a powerful tool to investigate the micro-scale mechanical behavior of granular soils.

关键词: triaxial apparatus     X-ray μCT     in situ test     micro-scale mechanical behavior     granular soils    

Hydraulic fracturing pressure of concentric double-layered cylinder in cohesive soil

《结构与土木工程前沿(英文)》 2021年 第15卷 第4期   页码 937-947 doi: 10.1007/s11709-021-0754-4

摘要: This study aims to investigate hydrofracturing in double-layered soil through theoretical and experimental analysis, as multilayered soils where the difference in mechanical properties exists are generally encountered in practical engineering. First, an analytical solution for fracturing pressure in two different concentric regions of soil was presented based on the cavity expansion theory. Then, several triaxial hydraulic fracturing tests were carried out to validate the analytical solution. The comparison between the experimental and analytical results indicates the remarkable accuracy of the derived formula, and the following conclusions were also obtained. First, there is a linear relationship between the fracturing pressure and confining pressure in concentric double-layered cohesive soil. Second, when the internal-layer soil is softer than the external-layer soil, the presence of internal soil on the fracturing pressure approximately brings the weakening effect, and the greater strength distinction between the two layers, the greater the weakening effect. Third, when the internal-layer soil is harder than the external-layer soil, the existence of the internal-layer soil has a strengthening effect on the fracturing pressure regardless of the proportion of internal-layer soil. Moreover, the influence of strength distinction between the two layers on the fracturing pressure is significant when the proportion of internal-layer soil is less than half, while it’s limited when the proportion is more than half. The proposed solution is potentially useful for geotechnical problems involving aspects of cohesive soil layering in a composite formation.

关键词: hydraulic fracturing pressure     layered     cavity expansion theory     triaxial fracturing test     cohesive soil    

Identify the contribution of vehicle non-exhaust emissions: a single particle aerosol mass spectrometertest case at typical road environment

《环境科学与工程前沿(英文)》 2023年 第17卷 第5期 doi: 10.1007/s11783-023-1662-8

摘要:

● A single particle observation was conducted in a high traffic flow road environment.

关键词: Non-exhaust emissions     SPAMS     PMF     Roadside environment    

Effects of natural zeolite and sulfate ions on the mechanical properties and microstructure of plastic concrete

《结构与土木工程前沿(英文)》 2022年 第16卷 第1期   页码 86-98 doi: 10.1007/s11709-021-0793-x

摘要: One of the strategic materials used in earth-fill embankment dams and in modifying and preventing groundwater flow is plastic concrete (PlC). PlC is comprised of aggregates, water, cement, and bentonite. Natural zeolite (NZ) is a relatively abundant mineral resource and in this research, the microstructure, unconfined strength, triaxial behavior, and permeability of PlC made with 0%, 10%, 15%, 20%, and 25% replacement of cement by NZ were studied. Specimens of PIC-NZ were subjected to confined conditions and three different confining pressures of 200, 350, and 500 kPa were used to investigate their mechanical behavior and permeability. To study the effect of sulfate ions on the properties of PlC-NZ specimens, the specimens were cured in one of two different environments: normal condition and in the presence of sulfate ions. Results showed that increasing the zeolite content decreases the unconfined strength, elastic modulus, and peak strength of PlC-NZ specimens at the early ages of curing. However, at the later ages, increasing the zeolite content increases unconfined strength as well as the peak strength and elastic modulus. Specimens cured in the presence of sulfate ions indicated lower permeability, higher unconfined strength, elastic modulus, and peak strength due to having lower porosity.

关键词: plastic concrete     sulfate resistance     natural zeolite     triaxial compression test     SEM     permeability    

Effect of loading rate on shear strength parameters of mechanically and biologically treated waste

《环境科学与工程前沿(英文)》 2022年 第16卷 第12期 doi: 10.1007/s11783-022-1595-7

摘要:

● Mechanical behavior of MBT waste affected by loading rate was investigated.

关键词: Mechanically and biologically treated waste     Landfill     Triaxial test     Loading rate     Axial strain     Shear strength parameter    

Numerical analysis of bearing behaviors of single batter piles under horizontal loads in various directions

《结构与土木工程前沿(英文)》 2023年 第17卷 第2期   页码 224-237 doi: 10.1007/s11709-022-0914-1

摘要: The horizontal bearing behavior of a single batter pile (SBP) is vital to its application in practical engineering; however, the horizontal responses of SBPs change with the directions of horizontal loads, and this phenomenon is rarely investigated. Therefore, the directional differences in the horizontal bearing behaviors of SBPs are investigated in this study. Four model tests are conducted to preliminarily examine the effects of the skew angle of horizontal loads on the horizontal bearing capacities and distributions of the bending moments of the SBPs. Subsequently, the differences in the responses of the SBPs under horizontal loads in various directions at full scale are analyzed comprehensively via finite-element (FE) analysis. The effects of the skew angle on SBP-soil interaction are discussed. Moreover, an empirical design method is proposed based on the FE analysis results to predict the bearing ratios of SBPs in medium-dense and dense sand while considering the effects of the skew angle, batter angle, and pile diameter. The method is confirmed to be effective, as confirmed by the close agreement between the predicting results with the model test (reported in this study) and centrifuge model test results (reported in the literature).

关键词: single batter pile     skew horizontal load     model test     finite-element analysis     empirical design method    

Evaluation of regenerative braking based on single-pedal control for electric vehicles

Wei LIU, Xintian LIU, Yansong WANG, Hongzhong QI

《机械工程前沿(英文)》 2020年 第15卷 第1期   页码 166-179 doi: 10.1007/s11465-019-0546-x

摘要: More than 25% of vehicle kinetic energy can be recycled under urban driving cycles. A single-pedal control strategy for regenerative braking is proposed to further enhance energy efficiency. Acceleration and deceleration are controlled by a single pedal, which alleviates driving intensity and prompts energy recovery. Regenerative braking is theoretically analyzed based on the construction of the single-pedal system, vehicle braking dynamics, and energy conservation law. The single-pedal control strategy is developed by considering daily driving conditions, and a single-pedal simulation model is established. Typical driving cycles are simulated to verify the effectiveness of the single-pedal control strategy. A dynamometer test is conducted to confirm the validity of the simulation model. Results show that using the single-pedal control strategy for electric vehicles can effectively improve the energy recovery rate and extend the driving range under the premise of ensuring safety while braking. The study lays a technical foundation for the optimization of regenerative braking systems and development of single-pedal control systems, which are conducive to the promotion and popularization of electric vehicles.

关键词: electric vehicle     single-pedal control     regenerative braking     co-simulation     dynamometer test    

Review of the crushing response of collapsible tubular structures

Vivek PATEL, Gaurav TIWARI, Ravikumar DUMPALA

《机械工程前沿(英文)》 2020年 第15卷 第3期   页码 438-474 doi: 10.1007/s11465-019-0579-1

摘要: Studies on determining and analyzing the crushing response of tubular structures are of significant interest, primarily due to their relation to safety. Several aspects of tubular structures, such as geometry, material, configuration, and hybrid structure, have been used as criteria for evaluation. In this review, a comprehensive analysis of the important findings of extensive research on understanding the crushing response of thin-walled tubular structures is presented. Advancements in thin-walled structures, including multi-cell tube, honeycomb and foam-filled, multi wall, and functionally graded thickness tubes, are also discussed, focusing on their energy absorption ability. An extensive review of experimentation and numerical analysis used to extract the deformation behavior of materials, such as aluminum and steel, against static and dynamic loadings are also provided. Several tube shapes, such as tubes of uniform and nonuniform (tapered) cross sections of circular, square, and rectangular shapes, have been used in different studies to identify their efficacy. Apart from geometric and loading parameters, the effects of fabrication process, heat treatment, and triggering mechanism on initiating plastic deformation, such as cutouts and grooves, on the surface of tubular structures are discussed.

关键词: monolithic structure     crashworthiness     energy absorber     static and dynamic loadings     multicellular tube structure     filled tube    

Behavior of dam concrete under biaxial compression-tension and triaxial compression-compression-tension

WANG Huailiang, SONG Yupu

《结构与土木工程前沿(英文)》 2008年 第2卷 第4期   页码 323-328 doi: 10.1007/s11709-008-0043-5

摘要: In order to meet the requirement for nonlinear analysis and design of mass concrete structures, the deformation behavior and strength of three-graded concrete specimens 250 mm × 250 mm × 400 mm with a maximum aggregate size of 80 mm and the corresponding wet-screened concrete specimens 150 mm × 150 mm × 300 mm with a maximum aggregate size of 40 mm were studied experimentally. Specimens subjected to biaxial compression-tension (C-T) and triaxial compression-compression-tension (C-C-T) stress states. Test data indicate that both the deformation and strength of the mass concrete specimens are lower than those of the corresponding wet-screened concrete small specimens, but the initial tangent modulus of the stress-strain curve of the former is greater than that of the latter. Test results show that the wet-screened effect and size effect of the specimens under complex stress states are obvious such that these should be considered in the design of mass concrete structures. In addition, respective failure criteria for mass concrete in principal stress space and octahedron stress space are proposed.

关键词: requirement     wet-screened concrete     compression-tension     maximum aggregate     principal    

Release of elements from municipal solid waste incineration fly ash

Wei WANG, Lei ZHENG, Feng WANG, Xiao WAN, Keqing YIN, Xingbao GAO

《环境科学与工程前沿(英文)》 2010年 第4卷 第4期   页码 482-489 doi: 10.1007/s11783-010-0245-7

摘要: The element-release behavior of municipal solid waste incineration fly ash was explored through leaching test with continuous set-point pH (pH test) and serial single reaction cell (SSRC) tests. First, the relationship between element release and acid neutralizing capacity (ANC) consumption was examined with a pH test. Four types of release behaviors were identified which are characteristic for different elements: (1) release curves that were almost linear with ANC consumption (Ca, Zn, and Cd); (2) release that was significantly faster than ANC (Na, K, and Cl); (3) curves that featured a strong increase with ANC consumption, after a transient release, followed by an almost equal decrease (Si and S); and (4) release that is strongly retarded compared with ANC consumption (Cr, Cu, and Pb). In the SSRC system, it the existence of a pH front and a wash-out phenomenon is demonstrated. Combining the results from the SSRC test with the kinetic analysis of the ANC system in the pH test, it was inferred that less than one-third of the ANC measured from a batch pH titration plays a neutralization role in a field situation. The methodologies described may provide a powerful set of tools for systematic evaluation of element release from solid wastes.

关键词: pHstat test     Serial single reaction cell test (SSRC)     leaching     heavy metal    

Temperature and structural responses of a single-section utility tunnel throughout fire exposure

Yanmin YANG; Ying XIONG; Yongqing LI; Xiangkun MENG; Peng WANG; Tianyuan CAI

《结构与土木工程前沿(英文)》 2022年 第16卷 第10期   页码 1351-1364 doi: 10.1007/s11709-022-0857-6

摘要: In this study, fire tests of four single-section scaled-down utility tunnels were conducted. By analyzing temperature and structural responses of the utility tunnel throughout the fire exposure, the effects on the fire behavior of two different construction methods, cast-in-situ and prefabricated, and of two different materials, ordinary concrete and full lightweight concrete, were explored. The results of the study showed that the shear failure of the cast-in-situ utility tunnel occurred at the end of the top or bottom plate, and the failure of the prefabricated utility tunnel occurred at the junction of the prefabricated member and post-cast concrete. As the temperature increased, the temperature gradient along the thickness direction of the tunnel became apparent. The maximum temperature difference between the inner and outer wall surfaces was 531.7 °C. The highest temperature occurred in the cooling stage after stopping the heating, which provided a reference for the fire protection design and rescue of the utility tunnel. The displacement of the top plate of the prefabricated utility tunnel was 16.8 mm, which was 41.8% larger than that of the cast-in-situ utility tunnel. The bearing capacities of the ordinary concrete utility tunnel and full lightweight concrete utility tunnel after the fire loss were 27% and 16.8%, respectively. The full lightweight concrete utility tunnel exhibited good ductility and fire resistance and high collapse resistance.

关键词: full lightweight concrete     construction methods     temperature response     structural response     fire test    

Effect of cavity defect on the triaxial mechanical properties of high-performance concrete

Yanbin ZHANG; Zhe WANG; Mingyu FENG

《结构与土木工程前沿(英文)》 2022年 第16卷 第5期   页码 600-614 doi: 10.1007/s11709-022-0821-5

摘要: The stress concentration of pipe structure or cavity defect has a great effect on the mechanical properties of the high-performance concrete (HPC) members in deep underground locations. However, the behaviour of HPC with cavities under triaxial compression is not understood, especially when pressurized liquid flows into the fractures from the cavity. This study aims to investigate the effect of the cavity and the confining pressure on the failure mechanisms, strengths, and deformation properties of HPC with a new experimental scheme. In this experiment, the pressurized liquid can only contact the surface of the sample in the cavity, while the other surfaces are isolated from the pressurized liquid. To further explore the effect of the cavity, the same experiments are also conducted on sealed and unsealed intact samples without a cavity. The failure modes and stress-strain curves of all types of the samples are presented. Under various confining pressures, all the samples with a cavity suffer shear failure, and there are always secondary tensile fractures initiating from the cavity sidewall. Additionally, it can be determined from the failure modes and the stress-strain curves that the shear fractures result from the sidewall failure. Based on the different effects of the cavity on the lateral deformations in different directions, the initiation of the sidewall fracture is well predicted. The experimental results show that both the increase of the confining pressure and the decrease of the cavity size are conducive to the initiation of sidewall fracture. Moreover, the cavity weakens the strength of the sample, and this study gives a modified Power-law criterion in which the cavity size is added as an impact factor to predict the strength of the sample.

关键词: high-performance concrete     cavity     conventional triaxial compression     pressurized liquid     modified power-law criterion    

三向应力状态下混凝土强度和变形特性研究

闫东明,林皋

《中国工程科学》 2007年 第9卷 第6期   页码 64-70

摘要:

对设计强度为10MPa的混凝土立方体试件进行三轴压缩试验,系统研究了等围压条件下混凝土的强 度和变形特性,围压分别为0,4,8,12,16MPa5个量级;同时研究了不等围压条件下混凝土强度变化特性, 试验表明,随着围压增加,混凝土的极限抗压强度有明显增强的趋势;随着小主应力的增加,中主应力的影响 有减弱的趋势;峰值应力处应变随围压增加幅度显著。得出了在不同恒定围压下混凝土的应力应变全过程曲线; 通过与当前文献资料的对比分析,指出了在混凝土结构计算中适用的强度及变形表达式,为工程实践提供了 依据。

关键词: 三向受力状态     不等围压     极限强度     变形     混凝土    

标题 作者 时间 类型 操作

A new method of studying collapsibility of loess

Yuanqing ZHU , Zhenghan CHEN ,

期刊论文

Crushed rocks stabilized with organosilane and lignosulfonate in pavement unbound layers: Repeated load triaxial

Diego Maria BARBIERI, Inge HOFF, Chun-Hsing HO

期刊论文

A miniature triaxial apparatus for investigating the micromechanics of granular soils with

Zhuang CHENG, Jianfeng WANG, Matthew Richard COOP, Guanlin YE

期刊论文

Hydraulic fracturing pressure of concentric double-layered cylinder in cohesive soil

期刊论文

Identify the contribution of vehicle non-exhaust emissions: a single particle aerosol mass spectrometertest case at typical road environment

期刊论文

Effects of natural zeolite and sulfate ions on the mechanical properties and microstructure of plastic concrete

期刊论文

Effect of loading rate on shear strength parameters of mechanically and biologically treated waste

期刊论文

Numerical analysis of bearing behaviors of single batter piles under horizontal loads in various directions

期刊论文

Evaluation of regenerative braking based on single-pedal control for electric vehicles

Wei LIU, Xintian LIU, Yansong WANG, Hongzhong QI

期刊论文

Review of the crushing response of collapsible tubular structures

Vivek PATEL, Gaurav TIWARI, Ravikumar DUMPALA

期刊论文

Behavior of dam concrete under biaxial compression-tension and triaxial compression-compression-tension

WANG Huailiang, SONG Yupu

期刊论文

Release of elements from municipal solid waste incineration fly ash

Wei WANG, Lei ZHENG, Feng WANG, Xiao WAN, Keqing YIN, Xingbao GAO

期刊论文

Temperature and structural responses of a single-section utility tunnel throughout fire exposure

Yanmin YANG; Ying XIONG; Yongqing LI; Xiangkun MENG; Peng WANG; Tianyuan CAI

期刊论文

Effect of cavity defect on the triaxial mechanical properties of high-performance concrete

Yanbin ZHANG; Zhe WANG; Mingyu FENG

期刊论文

三向应力状态下混凝土强度和变形特性研究

闫东明,林皋

期刊论文