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Gao Z.-Y.,Shenzhen University | Zhao P.,Central and Southem China Municipal Engineering Design & Research Institute Co. | Qi M.-Z.,China Merchants Shekou Industrial Zone Co. | Li J.-H.,Harbin Institute of Technology | Su D.,Shenzhen University
Yantu Lixue/Rock and Soil Mechanics | Year: 2015

Model tests have been conducted on a single pile and pile group in sand under both compressive and tensile loadings. Axial forces, loads and displacements at the pile head, and pile tip resistance were measured. Experimental results show that the compressive group pile effect coefficient η is greater than 1. The optimal pile spacing is 4D(D is pile diameter), at which η is about 1.2. The pile tip resistance coefficient ηB is greater than the lateral friction coefficient ηs. The pile tip resistance coefficient reaches maximum at the spacing of 5D with a value of about 1.3. The lateral friction coefficient is about 1.2 at pile spacing of 3D, but it decreases with the increasing of pile spacing. Different from the results revealed by previous theoretical analysis, the test results show that the pullout group effect coefficient is greater than 1, due to sand densification during pile driving. The optimal pile spacing is between 4D-5D, with a maximum coefficient of about 1.2. The group coefficient is close to 1 when the pile spacing is greater than 7D and the group pile effect can be ignored. ©, 2015, Academia Sinica. All right reserved.

Li J.H.,University of Western Australia | Li J.H.,Harbin Institute of Technology | Zhang L.M.,Hong Kong University of Science and Technology | Zhao Y.,China Merchants Shekou Industrial Zone Co.
Geotechnical Safety and Risk IV - Proceedings of the 4th International Symposium on Geotechnical Safety and Risk, ISGSR 2013 | Year: 2014

Cracks in soils are three-dimensional (3D) and provide important preferential pathways for rainfall infiltration. The geometrical properties of 3D cracks are crucial parameters for analysis of seepage in discontinuous soils or rocks. However 3D crack planes in soils are still largely unknown because the cracks in soils are prone to disturbance and sensitive to moisture content. This paper presents a method to characterize 3D crack planes in soils by employing a nondestructive Computer Tomography (CT) test. The traces of cracks are first obtained from sections along three directions in the CT test. Then three criteria are proposed to determine a crack plane based on these crack traces. Finally the random crack network in the soil is established by assembling the planes. The probability distribution and statistical parameters can be obtained based on the obtained crack planes. © 2014 Taylor & Francis Group, London.

Wang B.-Q.,China Academy of Railway Sciences | Gong L.,China Merchants Shekou Industrial Zone Co. | Liu G.-N.,China Academy of Railway Sciences
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

The pattern of double-layered super-soft underconsolidated ground composed of hydraulic fill and marine mud is the most common situation in land reclamation projects. The settlement of this ground is different from the original marine deposit mud layer, showing greater discreteness. The settlement of the combination ground is analyzed by statistical methods. Through the statistical analysis of the actual settlement data, the optimum probability distribution model for the settlement data is confirmed by the K-S finite contrast method. The results of probability prediction by using the distribution model are consistent with the actual statistics, and the rationality of probability analysis is validated.

Zhang M.,China Academy of Railway Sciences | Zhao Y.,China Academy of Railway Sciences | Gong L.,China Merchants Shekou Industrial Zone Co. | Hu R.,China Academy of Railway Sciences
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2010

Automatic pressure consolidometer is introduced to conduct numerous consolidation tests of hydraulic ultra-soft soil filling in Shenzhen Bay, and results are analyzed statistically and compared with coefficient of consolidation of original mud. The obtained results verify that: (1) In actual engineering, coefficient of consolidation is introduced to estimate the deformation and rate of consolidation of hydraulic mud filling approximately in special zone, which is confined within a statistical sample average curve in stress range(less than 100 kPa) and a logarithm function-width in stress range(more than 100 kPa). (2) Consolidation coefficient of hydraulic mud filling is less than original mud in a same zone, with an increase in consolidation pressure, the difference becomes small. It shows that hydraulic mud filling can be achieved a same drainage consolidation rate with original mud after it experiences surcharge preloading.

Ding Z.,Zhejiang University City College | Zhang T.,China Merchants Shekou Industrial Zone Co. | Wei X.-J.,Zhejiang University City College | Zhang M.-Y.,Zhejiang University City College
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

The underlying soil, which is disturbed by subway tunneling, will show a different degree of consolidation which is associated with the strain of soil, and thus cause uneven settlement. Hangzhou saturated soft clay is studied using a dynamic triaxial test system to find the effects of drainage conditions, degrees of consolidation and cyclic times on dynamic pore pressure and strain. A new strain-degradation model considering degrees of initial consolidation, cyclic stress ratios and drainage conditions is proposed on the basis of the experiments and the existing research findings. The results show that the higher the degree of consolidation, the slower the increase of the pore pressure. Furthermore, the pore pressure will be stabilized at a lower level with the increment of cyclic times, and the law of pore pressure under drainage conditions may be obtained from undrained tests. The dynamic strain increases with the increase of the cyclic times and decreases with the decrease of the degrees of consolidation. The proposed strain model considers the drainage of the soil during the loading cycles, and it can well simulate dynamic strain changes under different degrees of consolidation. ©, 2015, Chinese Society of Civil Engineering. All right reserved.

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