A bounding surface plasticity model for unsaturated soil at small strains          下载免费PDF全文

C. Zhou  C.W.W. Ng  R. Chen 《国际地质力学数值与分析法杂志》2015,39(11):1141-1164

Most existing hydromechanical models for unsaturated soils are not able to fully capture the nonlinearity of stress–strain curves at small strains (less than 1%). They cannot therefore, for example, accurately predict ground movements and the performance of many earth structures under working conditions. To tackle this problem, a state‐dependent bounding surface plasticity model has been newly developed. Particularly, the degradation of shear modulus with strain at small strains ranging from 0.001% to 1% is focused. The proposed model is formulated in terms of mean average skeleton stress, deviator stress, suction, specific volume and degree of saturation. Void ratio‐dependent hydraulic hysteresis is coupled with the stress–strain behaviour. Different from other elastoplastic models for unsaturated soils, plastic strains are allowed inside bounding surfaces. In this paper, details of model formulations and calibration procedures of model parameters are presented. To evaluate the capability of the new model, it is applied to simulate a series of triaxial compression tests on compacted unsaturated silt at various suctions. Effects of suction, drying and wetting as well as net stress on unsaturated soil behaviour are well captured. The model shows good predictions of the degradation of shear modulus with strain over a wide range of strains from 0.001% to 1%. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

花岗岩风化程度的化学指标及微观特征对比——以香港九龙地区为例   总被引：18，自引：1，他引：18  

尚彦军  吴宏伟  曲永新 《地质科学》2001,36(3):279-294

据香港九龙3个不同工程场地取得的149件不同级别的风化花岗岩样品的化学分析结果,用统计学方法,从反映岩石风化程度的18项化学指标中选取9项进行了分析计算.对其结果及其与风化程度分级的关系的研究表明有4种指标比较理想.通过对样品微观特征的观察研究和矿物成分、微孔隙率以及综合显微岩石指标(I_p)进行了描述和定量分析,发现其中一些指标有一定相关性.这些化学指标和微观特征相关的统计值在一定程度上可定量表征花岗岩的风化程度,即:随风化作用进行,碱、碱土金属组分逐渐淋失,脱硅、富铝铁化作用逐渐加强;相应地,先是钠长石风化成高岭石,其次为云母和钾长石的风化.粘土矿物所占体积百分比随风化程度增高而变大,至残积土(Ⅵ级)时已达50%左右;I_p指标值下降,微孔隙率增高.文章综合出各个风化级别的指标变化范围及平均值供花岗岩分布区花岗岩风化野外调查和研究工作参考.  相似文献   

The SIJORI Cross‐Border Region: Transnational Politics,Economics and Culture Francis E. Hutchinson and Terence Chong. ISEAS Publishing,Singapore, 2016, pp. xxiii + 462 (ISBN 978‐981‐4695‐58‐9) (pbk) (ISBN 978‐981‐4695‐59‐6) (ebk).          下载免费PDF全文

Keng Khoon Ng 《Singapore journal of tropical geography》2017,38(3):430-432

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Anomalous particle-production thresholds through systematic and non-systematic quantum-gravity effects     

Giovanni Amelino-Camelia  Y. Jack Ng  Hendrik van Dam 《Astroparticle Physics》2003,19(6):729-738

A growing number of studies is being devoted to the identification of plausible quantum properties of spacetime which might give rise to observably large effects. The literature on this subject is now relatively large, including studies in string theory, loop quantum gravity and non-commutative geometry. It is useful to divide the various proposals into proposals involving a systematic quantum-gravity effect (an effect that would shift the main/average prediction for a given observable quantity) and proposals involving a non-systematic quantum-gravity effect (an effect that would introduce new fundamental uncertanties in some observable quantity). The case of quantum-gravity-induced particle-production-threshold anomalies, a much studied example of potentially observable quantum-gravity effect, is here used as an example to illustrate the differences to be expected between systematic and non-systematic effects.  相似文献   

A sandwiched denitrifying biocathode in a microbial fuel cell for electricity generation and waste minimization     

A. Al-Mamun  O. Lefebvre  M. S. Baawain  H. Y. Ng 《International Journal of Environmental Science and Technology》2016,13(4):1055-1064

A denitrifying biocathode in a microbial fuel cell was developed to investigate the replacement of the costly Pt-coated abiotic cathodes for electricity generation. The denitrifying biocathode was sandwiched between the dual-anode systems. The study investigated the performance for simultaneous treatment of wastewater on the anode, biological denitrification on the cathode and the potential recovery of electrical energy. Autotrophic biofilms performed denitrification on the cathode using supplied electrons by the biodegradation of organics on the anode. Graphite granules were used as electrodes for biofilm attachment, and nafion membranes were used as separators between electrodes. The system achieved a volumetric power of 7 ± 0.4 W m^?3 net cathodic compartment (NCC) with the simultaneous removal of 229.5 ± 18 mg L^?1 COD on anode and 88.9 g m^?3 NCC day^?1 nitrogen on cathode, respectively. The columbic efficiency for cathodic and anodic reactions was 98.9 ± 0.57 and 23.54 ± 0.87 %, respectively. This is a combined study for domestic wastewater treatment and biological denitrification in a compact MFC reactor. Further optimization of the system is desired to improve its performance and applicability.  相似文献   

Urban heat islands in Hong Kong: statistical modeling and trend detection     

Weiwen Wang  Wen Zhou  Edward Yan Yung Ng  Yong Xu 《Natural Hazards》2016,83(2):885-907

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Influence of discontinuities on the stability of cut slopes in weathered meta-sedimentary rocks     

J.I. Nkpadobi  J.K. Raj  T.F. Ng 《Geomechanics and Geoengineering》2015,10(4):290-302

The meta-sedimentary rocks along Pos Selim Highway in Perak State, Malaysia showed a gradational weathering profile based on differences particularly in textures, hardness, lateral changes in colour and consistency of material extension. Both large and small scale discontinuities observed in the investigated rocks reduce the physical and mechanical properties of the rocks, and provide slip surfaces for failures. Rock and soil samples were tested using established standards to determine their characteristics and responses under a wide variety of disturbances. Kinematic analyses were also carried out to determine the modes and likely modes of failures.

Petrographic analyses revealed associated micro-structures, and the implications of these micro-structures showed shearing components along planes of weakness. From the determined index properties of the tested soil samples, the weathered quartz mica schist is not suitable for structural support. Further study involving unconsolidated undrained direct shear box tests carried out under total stress, revealed a non-uniform response of the rocks to shearing disturbance along discontinuity planes, and the rate and depth of deformation. The shear strength components of the investigated rocks were thereby prescribed in terms of cohesion and friction angle. From the kinematic analyses across this extended cut slope, there are possibilities of wedge and planar failures.  相似文献   

Rainfall Variability Index (RVI) analysis of dry spells in Malaysia     

Huang  Yuk Feng  Ahmed  Ali Najah  Ng  Jing Lin  Tan  Kok Weng  Kumar  Pavitra  El-Shafie  Ahmed 《Natural Hazards》2022,112(2):1423-1475

Natural Hazards - The lower number of rainfall events resulting in drier environment over the years is a crucial phenomenon attracting the concern of all around the world. The impact of rainfall...  相似文献   

An evaluation of various data pre-processing techniques with machine learning models for water level prediction     

Tiu  Ervin Shan Khai  Huang  Yuk Feng  Ng  Jing Lin  AlDahoul  Nouar  Ahmed  Ali Najah  Elshafie  Ahmed 《Natural Hazards》2022,110(1):121-153

Natural Hazards - Floods are the most frequent type of natural disaster. It destroys wildlife habitat, damages bridges, railways, roads, properties, and puts millions of people at risk. As such,...  相似文献   

Erratum to: Physical modeling of baffles influence on landslide debris mobility     

C. W. W. Ng  C. E. Choi  D. Song  J. S. H. Kwan  R. C. H. Koo  H. Y. K. Shiu  K. K. S. Ho 《Landslides》2015,12(3):627-627

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