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Shi Y.-C.,Lanzhou Institute of Seismology | Shi Y.-C.,Open Laboratory of Loess Earthquake Engineering | Qiu G.-R.,Lanzhou Institute of Seismology
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

Loess is a typical structural soil, and its seismic subsidence is mainly due to the internal microstructure and external load. Seismic subsidence of loess is a congregated macroscopical phenomenon of microstructure with the external load in different time and space. The distribution of loess particles and pores is obtained through electron microscope scanning experiments. The structural damage model is established by means of the statistical microscopic damage mechanics and structural mechanics. It explains the inherent damage mechanism of seismic subsidence, and the complete constitutive relation is obtained. The results indicate that the seismic subsidence of loess results from the damage of particular trellis pores and particles falling into trellis pores. It appears that there's a great relation between the seismic subsidence of loess and the dynamic stress and the distribution of particles and pores.

Zhong X.,China Earthquake Administration | Zhong X.,Open Laboratory of Loess Earthquake Engineering | Qiu R.,China Academy of Building Research | Chen Y.,China Earthquake Administration | And 3 more authors.
World Information on Earthquake Engineering | Year: 2011

This paper develops a 3-D finite element model of Yungang Grottoes and conducts nonlinear time history analysis considering the combination of horizontal and vertical earthquake motions. Distribution of stress and displacement of the Crottos rockmass was calculated. The results show that larger displacement appears in the pillar and entrance of grottoes, tension, shear and compression stresses concentrate in the grottoes, especially around thinwalled position. Then, comparing the input of vertical and horizontal seismic loads, the influence of vertical seismic load on tensile stress is more significant, the compression stress from vertical seismic load is substantially smaller than that from horizontal seismic load, but the horizontal seismic load is more likely to cause shear stress concentration and more easier to cause destruction the of grottoes.

Wang A.-G.,Lanzhou Institute of Seismology | Ma W.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Wu Z.-J.,Lanzhou Institute of Seismology | Wu Z.-J.,Open Laboratory of Loess Earthquake Engineering
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

By analyzing the simulated temperature field of frozen-soil foundation with embankment in different structures, the embankment cooling effect and some important factors and their relationship are studied. The factors include embankment structure, temperature in block-stone layer, convection Rayleigh number (Ra) and the critical Rayleigh number (Rac) of different convection patterns. The research results show that the air convection pattern of block-stone in winter is the most important key factors influencing the cooling effect of embankment, and the block-stone embankment structure in which the air convection patterns are mainly (1, 1) and (2, 1) in winter has the strongest cooling effect on frozen soil foundation.

Wang P.,China Earthquake Administration | Wang P.,Open Laboratory of Loess Earthquake Engineering | Wang Q.,China Earthquake Administration | Wang Q.,Open Laboratory of Loess Earthquake Engineering | And 5 more authors.
World Information on Earthquake Engineering | Year: 2011

Loess liquefaction is one of the typical earthquake damages in the loess region, which is the most advanced subjects of loess dynamics in recent years. Up to now, the dynamic triaxial lest is still the main method to study loess liquefaction, and the saturated degree is the main influence factors of the test. In this paper, the difference between sand liquefaction and loess liquefaction was compared based on the analysis of the soil characteristics and saturated indexes, and the study situation of saturated methods was summarized based on discusses of the main saturated methods. Meanwhile, the applicability of the methods for loess sample saturated was commented by involving the big pore and weakly cemented properties of the loess. Finally, the prospect of the application of back pressure method in loess sample saturated test was discussed based on the application actualities of the method in the loess saturated test.

Sheng Z.-Q.,China Earthquake Administration | Shi Y.-C.,China Earthquake Administration | Shi Y.-C.,Open Laboratory of Loess Earthquake Engineering | Sun J.-J.,China Earthquake Administration | And 7 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

By means of the finite element software named ABAQUS, the settlement and deformation of the pile-soil system under vertical load are analyzed. The foundations with pile groups can be divided into three categories: different pile spacings, different pile lengths, and different pile numbers. For numberical analysis, the Mohr-Coulomb criterion is adopted. Based on some large scale mode tests on pile groups, it is found that the results of 3D FEM analysis using ABAQUS software are convincing. The results show that the settlement of pile group foundation decreases if the pile spacing or length increases. Compared with the settlement and deformation of pile group foundation with different pile numbers, the settlement increases with the number of piles, nevertheless, the settlement value is stable when piles are larger than number 25×25. In other words, the change of the settlement of the pile foundation is not obvious with the increase of the pile number if it exceeds a certain level. Many researches should be done to show whether or not the foundation settlement of smaller number (25×25) of piles can be calculated, and the settlement of the foundation with larger number of piles meets the need of engineering design.

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