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Model test and discrete element method simulation of shield tunneling face stability in transparent clay

Huayang LEI, Yajie ZHANG, Yao HU, Yingnan LIU

《结构与土木工程前沿（英文）》 2021年第15卷第1期页码 147-166 doi: 10.1007/s11709-020-0704-6

摘要： The stability of the shield tunneling face is an extremely important factor affecting the safety of tunnel construction. In this study, a transparent clay with properties similar to those of Tianjin clay is prepared and a new transparent clay model test apparatus is developed to overcome the “black box” problem in the traditional model test. The stability of the shield tunneling face (failure mode, influence range, support force, and surface settlement) is investigated in transparent clay under active failure. A series of transparent clay model tests is performed to investigate the active failure mode, influence range, and support force of the shield tunneling face under different burial depth conditions, whereas particle flow code three-dimensional numerical simulations are conducted to verify the failure mode of the shield tunneling face and surface settlement along the transverse section under different burial depth conditions. The results show that the engineering characteristics of transparent clay are similar to those of soft clay in Binhai, Tianjin and satisfy visibility requirements. Two types of failure modes are obtained: the overall failure mode (cover/diameter: / ≤1.0) and local failure mode ( / ≥2.0). The influence range of the transverse section is wider than that of the longitudinal section when / ≥2.0. Additionally, the normalized thresholds of the relative displacement and support force ratio are 3%–6% and 0.2–0.4, respectively. Owing to the cushioning effect of the clay layer, the surface settlement is significantly reduced as the tunnel burial depth increases.

关键词： shield tunneling face stability transparent clay model test numerical simulation

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Bearing and uplift capacities of under-reamed piles in soft clay underlaid by stiff clay using lower-bound

Mantu MAJUMDER, Debarghya CHAKRABORTY

《结构与土木工程前沿（英文）》 2021年第15卷第2期页码 537-551 doi: 10.1007/s11709-021-0708-x

摘要： Ensuring a safe foundation design in soft clay is always a challenging task to engineers. In the present study, the effectiveness of under-reamed piles in soft clay underlaid by stiff clay is numerically studied using the lower-bound finite element limit analysis (LB FELA). The bearing and uplift capacities of under-reamed piles are estimated through non-dimensional factors and , respectively. These factors increased remarkably and marginally compared to and of the piles without bulbs when the bulb is placed in stiff and soft clay, respectively. For a given ratio of undrained cohesion of stiff to soft clay ( / ), the factors and moderately increased with the increase in the length-to-shaft-diameter ratio ( / ) and adhesion factors in soft clay ( ) and stiff clay ( ). The variation of radial stress along the pile–soil interface, distribution of axial force in the under-reamed piles, and state of plastic shear failure in the soil are also studied under axial compression and tension. The results of this study are expected to be useful for the estimation of the bearing and uplift capacities of under-reamed piles in uniform clay and soft clay underlaid by stiff clay.

关键词： bearing capacity uplift capacity under-reamed pile clay limit analysis

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Model testing of tripod caisson foundations in silty clay subjected to eccentric lateral loads

《结构与土木工程前沿（英文）》 2023年第17卷第3期页码 467-476 doi: 10.1007/s11709-023-0933-6

摘要： In this study, model tests were conducted to investigate the bearing capacities of tripod caisson foundations subjected to eccentric lateral loads in silty clay. Lateral load–rotation curves of five eccentric-shaped tripod suction foundations were plotted to analyze the bearing capacities at different loading angles. It was observed that the loading angle significantly influenced the bearing capacity of the foundations, particularly for eccentric tripod caisson foundations. Compared with eccentric tripod caisson foundations, the traditional tripod foundation has a relatively high ultimate lateral capacity at the omnidirectional loading angle. By analyzing the displacement of the caissons, a formula for the rotational center of the tripod caisson foundation subjected to an eccentric lateral load was derived. The depth of the rotation center was 0.68–0.92 times the height of the caisson when the bearing capacity reached the limit. Under the undrained condition, suction was generated under the lid of the “up-lift” caisson, which helps resist lateral forces from the wind and waves.

关键词： tripod caisson foundation silty clay eccentric lateral capacity model tests

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Behavior of compacted clay-concrete interface

R. R .SHAKIR, Jungao ZHU

《结构与土木工程前沿（英文）》 2009年第3卷第1期页码 85-92 doi: 10.1007/s11709-009-0013-6

摘要： Tests of interface between compacted clay and concrete were conducted systematically using interface simple shear test apparatus. The samples, having same dry density with different water content ratio, were prepared. Two types of concrete with different surface roughness, i.e., relatively smooth and relatively rough surface roughness, were also prepared. The main objectives of this paper are to show the effect of water content, normal stress and rough surface on the shear stress-shear displacement relationship of clay-concrete interface. The following were concluded in this study: 1) the interface shear sliding dominates the interface shear displacement behavior for both cases of relatively rough and smooth concrete surface except when the clay water content is greater than 16% for the case of rough concrete surface where the shear failure occurs in the body of the clay sample; 2) the results of interface shear strength obtained by direct shear test were different from that of simple shear test for the case of rough concrete surface; 3) two types of interface failure mechanism may change each other with different water content ratio; 4) the interface shear strength increases with increasing water content ratio especially for the case of clay-rough concrete surface interface.

关键词： soil structure interaction simple shear test interface friction compacted clay interface modeling

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Preparation of transparent BaSO

Le Fang, Qian Sun, Yong-Hong Duan, Jing Zhai, Dan Wang, Jie-Xin Wang

《化学科学与工程前沿（英文）》 2021年第15卷第4期页码 902-912 doi: 10.1007/s11705-020-1985-y

摘要： BaSO nanoparticles as important functional materials have attracted considerable research interests, due to their X-rays barrier and absorption properties. However, most of BaSO nanoparticles prepared by traditional technology are nanopowders with broad size distribution and poor dispersibility, which may greatly limit their applications. To the best of our knowledge, the synthesis of transparent BaSO nanodispersions was rarely reported. Here, we firstly present a novel and efficient method to prepare transparent and stable BaSO nanodispersions with a relatively small particle size around 10 to 17 nm using a precipitation method in a rotating packed bed (RPB), followed by a modification treatment using stearic acid. Compared with the BaSO prepared in a traditional stirred tank, the product prepared using an RPB has much smaller particle size and narrower size distribution. More importantly, by using RPB, the reaction time can be significantly decreased from 20 min to 18 s. Furthermore, the transparent BaSO -polyvinyl butyral nanocomposite films with good X-ray shielding performance can be easily fabricated. We believe that the stable BaSO nanodispersions may have a wide range of applications for transparent composite materials and coatings with X-ray shielding performance for future research.

关键词： BaSO₄ nanoparticles rotating packed bed transparent nanodispersions BaSO₄-PVB films X-ray shielding

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Analysis of cement-treated clay behavior by micromechanical approach

Dong-Mei ZHANG, Zhen-Yu YIN, Pierre-Yves HICHER, Hong-Wei HUANG

《结构与土木工程前沿（英文）》 2013年第7卷第2期页码 137-153 doi: 10.1007/s11709-013-0204-z

摘要： Experimental results show the significant influence of cement content on the mechanical properties of cement-treated clays. Cementation is produced by mixing a certain amount of cement with the saturated clay. The purpose of this paper is to model the cementation effect on the mechanical behavior of cement-treated clay. A micromechanical stress-strain model is developed considering explicitly the cementation at inter-cluster contacts. The inter-cluster bonding and debonding during mechanical loading are introduced in two ways: an additional cohesion in the shear sliding and a higher yield stress in normal compression. The model is used to simulate isotropic compression and undrained triaxial tests under various confining stresses on cement-treated Ariake clay and Singapore clay with various cement contents. The applicability of the present model is evaluated through comparisons between numerical and experimental results. The evolution of local stresses and local strains in inter-cluster planes are discussed in order to explain the induced anisotropy due to debonding at contact level under the applied loads. The numerical simulations demonstrate that the proposed micromechanical approach is well adapted for taking into account the main physical properties of cement-treated clay, including damage and induced anisotropy under mechanical loading.

关键词： microstructure cementation clay micromechanics anisotropy debonding

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ImgFS: a transparent cryptography for stored images using a filesystem in userspace

Osama A. KHASHAN,Abdullah M. ZIN,Elankovan A. SUNDARARAJAN

《信息与电子工程前沿（英文）》 2015年第16卷第1期页码 28-42 doi: 10.1631/FITEE.1400133

摘要： Real-time encryption and decryption of digital images stored on end-user devices is a challenging task due to the inherent features of the images. Traditional software encryption applications generally suffered from the expense of user convenience, performance efficiency, and the level of security provided. To overcome these limitations, the concept of transparent encryption has been proposed. This type of encryption mechanism can be implemented most efficiently with kernel file systems. However, this approach has some disadvantages since developing a new file system and attaching it in the kernel level requires a deep understanding of the kernel internal data structure. A filesystem in userspace (FUSE) can be used to bridge the gap. Nevertheless, current implementations of cryptographic FUSE-based file systems suffered from several weaknesses that make them less than ideal for deployment. This paper describes the design and implementation of ImgFS, a fully transparent cryptographic file system that resides on user space. ImgFS can provide a sophisticated way to access, manage, and monitor all encryption and key management operations for image files stored on the local disk without any interaction from the user. The development of ImgFS has managed to solve weaknesses that have been identified on cryptographic FUSE-based implementations. Experiments were carried out to measure the performance of ImgFS over image files’ read and write against the cryptographic service, and the results indicated that while ImgFS has managed to provide higher level of security and transparency, its performance was competitive with other established cryptographic FUSE-based schemes of high performance.

关键词： Storage image security Cryptographic file system Filesystem in userspace (FUSE) Transparent encryption

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Utilizing transparent and conductive SnO

Jing Gu, Hongtao Yu, Xie Quan, Shuo Chen, Junfeng Niu

《环境科学与工程前沿（英文）》 2020年第14卷第4期 doi: 10.1007/s11783-020-1251-z

摘要： Abstract • A novel Z-scheme Si-SnO2-TiOx with SnO2 as electron mediator is first constructed. • Transparent and conductive SnO2 can pass light through and promote charge transport. • VO from SnO2 and TiOx improve photoelectrochemical performances. • Efficient photocatalytic degradations originate from the Z scheme construction. Z-scheme photocatalysts, with strong redox ability, have a great potential for pollutants degradation. However, it is challenging to construct efficient Z-scheme photocatalysts because of their poor interfacial charge separation. Herein, by employing transparent and conductive SnO2 as electron mediator to pass light through and promote interfacial charge transportation, a novel Z-scheme photocatalyst Si-SnO2-TiOx (1

关键词： Z-scheme photocatalyst Tin oxide Electron mediator Organic pollutant

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Experimental investigation of the influence on static and cyclic deformation of structural soft clay

CHEN Yunmin, CHEN Yingping, HUANG Bo

《结构与土木工程前沿（英文）》 2007年第1卷第4期页码 422-429 doi: 10.1007/s11709-007-0057-4

摘要： This paper presents the experimental results performed to study the static and cyclic deformation behavior of undisturbed and remolded soft clays sampling from Xiaoshan. The consolidation tests indicated that the vertical strains of

关键词： consolidation deformation experimental undisturbed

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Synthesis, characterization and assessment thermal properties of clay based nanopigments

Mohammad Banimahd KIEVANI, Milad EDRAKI

《化学科学与工程前沿（英文）》 2015年第9卷第1期页码 40-45 doi: 10.1007/s11705-015-1505-7

摘要： Nano-clay based pigments (NCP) are new type of pigments composed of organic dyes and layered silicate-clay nano-particles, and have already been used in polymeric coatings to improve mechanical thermal and stability properties. In this paper, the basic blue 41(BB41) was intercalated into Na - montmorillonite in an aqueous medium. The dye-intercalated montmorillonite was centrifuged, dried, and milled to prepare the nanopigment particles. X-ray diffraction showed an increase in the basal spacing, thus confirming intercalation of the BB41 molecules within the nanostructures of the interlayer spaces. Fourier transform infrared spectroscopy was used for identifying the functional groups and chemical bounding of Na -montmorillonite, BB41 and montmorillonite-BB41. The morphology of NCP was also studied by transmission electron microscopy. Finally, thermo-gravimetric analysis and differential thermograms suggested the thermal stability of the intercalated dye was improved.

关键词： nanopigment layered silicate cationic dye thermal properties

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Ultimate bearing capacity of strip footing resting on clay soil mixed with tire-derived aggregates

《结构与土木工程前沿（英文）》 2021年第15卷第4期页码 1016-1024 doi: 10.1007/s11709-021-0751-7

摘要： This study investigated the use of recycled tire-derived aggregate (TDA) mixed with kaolin as a method of increasing the ultimate bearing capacity ( UBC) of a strip footing. Thirteen 1g physical modeling tests were prepared in a rigid box of 0.6 m × 0.9 m in plan and 0.6 m in height. During sample preparation, 0%, 20%, 40%, or 60% (by weight) of powdery, shredded, small-sized granular (G 1–4 mm) or large-sized granular (G 5–8 mm) TDA was mixed with the kaolin. A strip footing was then placed on the stabilized kaolin and was caused to fail under stress-controlled conditions to determine the UBC. A rigorous 3D finite element analysis was developed in Optum G-3 to determine the UBC values based on the experimental test results. The experimental results showed that, except for the 20% powdery TDA, the TDA showed an increase in the UBC of the strip footing. When kaolin mixed with 20% G (5–8 mm), the UBC showed a threefold increase over that for the unreinforced case. The test with 20% G (1–4 mm) recorded the highest subgrade modulus. It was observed that the UBC calculated using finite element modeling overestimated the experimental UBC by an average of 9%.

关键词： kaolin physical modeling tests stabilization numerical modeling

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Optimized porous clay heterostructure for removal of acetaldehyde and toluene from indoor air

Pu ZHAO,Lizhong ZHU

《环境科学与工程前沿（英文）》 2016年第10卷第2期页码 219-228 doi: 10.1007/s11783-014-0760-z

摘要： Adsorption is the most widely used technology for the removal of indoor volatile organic compounds (VOCs). However, existing adsorbent-based technologies are inadequate to meet the regulatory requirement, due to their limited adsorption capacity and efficiency, especially under high relative humidity (RH) conditions. In this study, a series of new porous clay heterostructure (PCH) adsorbents with various ratios of micropores to mesopores were synthesized, characterized and tested for the adsorption of acetaldehyde and toluene. Two of them, PCH25 and PCH50, exhibited markedly improved adsorption capability, especially for hydrophilic acetaldehyde. The improved adsorption was attributed to their large micropore areas and high micropore-to-mesopore volume ratios. The amount of acetaldehyde adsorbed onto PCH25 at equilibrium reached 62.7 mg·g , eight times as much as the amount adsorbed onto conventional activated carbon (AC). Even at a high RH of 80%, PCH25 removed seven and four times more of the acetaldehyde than AC and the unmodified raw PCHs did, respectively. This new PCH optimized for their high adsorption and resistance to humidity has promising applications as a cost-effective adsorbent for indoor air purification.

关键词： porous clay heterostructure volatile organic compounds adsorption adsorbent indoor air

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从资源共享到服务共享：透明计算的机遇与挑战

张尧学,周悦芝

《中国工程科学》 2009年第11卷第8期页码 10-17

摘要：

随着计算机和网络技术以及应用的不断快速发展，计算模式从最初的以主机计算为主，发展到以桌面(PC)计算为主，再发展到现在的以网络计算为主，乃至普适计算。然而，迄今为止的计算模式还是遵循以单机或单机联合为基础的单机思维模式，因此，目前的计算模式还是一种以“资源共享”为主要特征的计算。在网络和普适计算的新时代，用户关心的主要是服务和服务共享，计算机也将从以“资源共享”为特征的计算过渡到以“服务共享”为特征的计算。笔者提出一种适应于“服务共享”的计算模式——透明计算，并对其概念、体系结构及相关关键技术进行介绍。此外，还对透明计算的未来发展及影响进行展望。

关键词：普适计算资源共享服务共享透明计算

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纤维膜在机械压力下由不透明到透明的转变 Article

王超, 赵景, 刘柳, 张鹏, 王先锋, 俞建勇, 丁彬

《工程（英文）》 2022年第19卷第12期页码 84-92 doi: 10.1016/j.eng.2021.02.018

摘要：

智能可穿戴设备、电子皮肤、空气过滤和组织工程等领域，对透明薄膜材料或基材的需求很大。传统透明材料，如玻璃、塑料等，由于缺乏相互连通的孔道、不理想的孔隙率和柔性，不能满足这些新兴领域的要求。静电纺丝纤维膜因其具有小孔径、高孔隙率和良好的柔性等优点可以弥补传统材料的不足，因此，开发透明的静电纺丝纤维膜具有重大的价值。本文报道了一种简单有效的方法，在不使用任何其他添加剂的情况下，通过机械压力，直接将静电纺丝纤维膜制备成柔性的、有孔的透明纤维膜材料。同时，首次总结了压制后聚合物的透明度性能与分子结构之间的关系。经过机械压力处理后，纤维膜仍可以保持纤维形态、微米级孔道和一定的孔隙率。以聚苯乙烯静电纺丝纤维膜为例，所制备的透明聚苯乙烯纤维膜具有优异的光学性能和机械性能。透明纤维膜可实现高透光率（≈89%，可见光波长在550 nm处）、大孔隙率（10%~30%）和强的机械拉伸强度（≈148 MPa），该拉伸强度约为初始静电纺丝纤维膜的78倍。此外，本文基于透明纤维膜，利用真空辅助抽滤银纳米线和机械压力作用，制备出透明的导电纤维膜材料。与氧化铟锡导电薄膜相比，我们所制备的透明导电纤维膜展示出良好的导电性（9 Ω·sq^-1，78%的透光率）和优异的机械性能（可承受大量的弯曲应力）。

关键词：透明静电纺丝纤维膜孔道结构机械压力导电