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Sun J.,Lanzhou Institute of Seismology | Wu Z.,Lanzhou Institute of Seismology | Liu K.,Key Laboratory of Loess Earthquake Engineering
6th Japan-China Geotechnical Symposium, SJGS 2015 | Year: 2015

Here we hoped to understand loess dynamic deformation through analyzing the physical process and mechanical mechanism. Therefore, we introduced a concept of stress ratio and proposed its mathematical formula to disclose the three-stage feature of loess dynamic strain hiding inside a series of laboratory data. By applied Mohr-Coulomb failure criterion, the stress ratio could consider three aspects of influence factors, i.e. structure strength of soil, consolidation pressure in actual field and seismic loading onto the soil. To a certain extent, the stress ratio could reveal the relative tolerability of loess soil under seismic loadings. Based on three-stage features of loess dynamic deformation, we obtained an empirical relation between stress ratio and compression value of void ratio. Then combined with a theoretical relation of dynamic residual strain, initial void ration and compression value of void ratio, we provided a semi-empirical model to estimate the dynamic residual strain of unsaturated loess. Source


Peng G.,Key Laboratory of Loess Earthquake Engineering | Peng G.,Lanzhou Institute of Seismology | Zhong-Xia Y.,Key Laboratory of Loess Earthquake Engineering | Zhong-Xia Y.,Lanzhou Institute of Seismology
WIT Transactions on Information and Communication Technologies | Year: 2014

With the development of information technology, we set up a large amount of seismic disaster prevention data in the field. Because of the heterogeneity of seismic disaster prevention data, it makes difficult for data to be exchanged and shared. To solve this problem, we use an optimization of heterogeneous data integration solution based on ETL technology. By using the ETL integrated optimization model, we realize the efficient integration of heterogeneous data. Experiment proved that quickly and effectively, the solution can eliminate the heterogeneity of the data and ensure consistency and accuracy of data. When integrating massive data, it performs better efficiency and has a good application value. © 2014 WIT Press. Source


Wu Z.,Key Laboratory of Loess Earthquake Engineering | Sun J.,Lanzhou Institute of Seismology | Chen Y.,Lanzhou Institute of Seismology | Wang Q.,Key Laboratory of Loess Earthquake Engineering | Zhao W.,Lanzhou Institute of Seismology
6th Japan-China Geotechnical Symposium, SJGS 2015 | Year: 2015

The Minxian-Zhangxian Ms6.6 earthquake induced a large number of loess landslides and collapses on July 22, 2013 in Dingxi city, Gansu province. In the center of the quake-hit area, it caused a banding area of landslides dense distribution with 8km wide and 30km long, and which long axis direction is in accordance with the trend of seismo-tectonics of the earthquake. Based on field test pit survey and surface wave investigation, the topography and soil distribution of the west loess landslide at Yongguang village in the landslides dense distribution area was identified. Moreover, the liquefaction probability of loess of the landslide was proven through dynamic triaxial liquefaction tests. The dynamic response characteristics of the landslide were analyzed by combining dynamic finite element method and strength reduction method as well. The results indicate that continuous heavy rain before the earthquake induced moisture content increasing and shear strength reducing in the surface loess layer of the slope. Coupling with the strong quake, tensile stress and liquefaction occurred in the surface soil layer, which caused the loess slope collapse instantaneously and a sliding distance of about 1000m long. Source


Xia K.,Lanzhou Institute of Seismology | Xia K.,Key Laboratory of Loess Earthquake Engineering | Pong L.,Lanzhou Institute of Seismology | Sun J.,Lanzhou Institute of Seismology | Sun J.,Key Laboratory of Loess Earthquake Engineering
Journal of Earthquake Engineering and Engineering Vibration | Year: 2012

The effect of site conditions on earthquake ground motion is remarkable,and the earthquake ground motion in loess region has its own characteristics. In view of the rising groundwater of Lanzhou, this paper selects a typical loess site on second terraces of Yellow River supposes groundwater will rise 1 m one time, and analyzes the effect of groundwater rise on peak ground acceleration and acceleration response spectrum by soil seismic response analysis. The following conclusions can be drawn: the higher the groundwater level, the less the peak ground acceleration and amplification factor will be. Groundwater rise can reduce the effect of ground motion to a certain extent. But the characteristic period becomes longer, the flat portion of response spectrum becomes wider, and die twopeak phenomena are more significant. Especially when the groundwater rises more(11m in fhis paper), the accelerations of the loess site amplify significantly under seldom occurring ground motions, the accelerations of the structures on the loess site,the natural periods of which are in the range of 0. 7 ∼ 1. 3 s.increase under frequently occurring ground motions and design ground motion. Attention should be paid to this. Source


Wang Q.,Key Laboratory of Loess Earthquake Engineering | Wang Q.,Lanzhou University | Wang Q.,Lanzhou Institute of Seismology | Wang P.,Key Laboratory of Loess Earthquake Engineering | And 8 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

Based on the SEM tests and dynamic triaxial tests on the loess with different microstructures from the Loess Plateau region and the liquefaction tests on undisturbed and disturbed Lanzhou loess with the same property state, the influence rules of structural properties of saturated loess on liquefaction strength are obtained. The relationship between microstructural types and the dynamic residual deformation behavior of saturated loess are qualitatively and quantitatively analyzed. Moreover, the development mechanisms of the dynamic residual deformation of the loess with different microstructures are obtained through analysis of the dynamic stress-dynamic residual strain of the loess in different regions. The results show that the liquefaction strength of saturated loess relates to the micro structure. The liquefaction strength of the soil decreases during the disturbed process because the particle reorganization and the cementation are weakened. The dynamic residual deformation of the saturated loess exponentially increases with the increase of vibration times, and the fitting parameters are mainly controlled by the density and plasticity index of the loess. The increase of dynamic residual deformation closely relates to the microstructural properties, the higher the structural strength, the slower growth the dynamic residual deformation of the loess. The development mechanisms of dynamic residual deformation are different for the loess with different microstructural properties. The dynamic residual deformation of weak cementation loess can be divided into visco-elastoplastic and plastic stages. However, the dynamic residual deformation of stronger cemented loess can be divided into visco-elastoplastic, visco-plasticity and plastic stages successively during liquefaction. ©, 2015, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved. Source

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