Key Laboratory of Loess Earthquake Engineering

Lanzhou, China

Key Laboratory of Loess Earthquake Engineering

Lanzhou, China

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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.


Xu S.-H.,Key Laboratory of Loess Earthquake Engineering | Xu S.-H.,Lanzhou Institute of Seismology | Sun J.-J.,Key Laboratory of Loess Earthquake Engineering | Sun J.-J.,Lanzhou Institute of Seismology | And 2 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

The seismic subsidence of loess is a main kind of earthquake disaster in a large loess region, and it cannot be avoided during project construction. It has been investigated for many years mainly by indoor experiment, while it is rare that it is found during actual earthquakes or investigated by field tests. The seismic subsidence of loess can be really seen by blast instead of actual ground motion in typical loess field. So distribution characteristics can be found and factors of the seismic subsidence of loess can be analyzed. The experimental results show that the strong ground motion can cause seismic subsidence of loess. The maximum of loess subsidence is 33 mm and the minimum is 13 mm in test field. It is discovered that the settlement distribution coincides well with the strength of ground motion and spectral characteristics (value of H/V) in the loess field and is partly controlled by terrain. The seismic subsidence of upper loess layers is less than that of the lower ones in the field tests due to the closer distance between the lower layers and explosion shots. © 2015, Chinese Society of Civil Engineering. All right reserved.


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.


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.


Xu S.,Lanzhou Institute of Seismology | Xu S.,Key Laboratory of Loess Earthquake Engineering | Wang L.,Lanzhou Institute of Seismology | Wang L.,Key Laboratory of Loess Earthquake Engineering | And 2 more authors.
Advanced Materials Research | Year: 2012

Seismic subsidence of loess is a kind of disaster induced by strong ground motion in loess area, while seldom example of this subsidence was found in long time study, usually instead of laboratory test. An explosion ground motion in a typical loess field was designed to verify seismic subsidence of loess with natural condition and laboratory test of loess seismic subsidence was conducted in China. The result proved seismic subsidence of loess could be induced by explosion ground motion, while the maxmuim settlement of 3.3cm in the case of experiment is much less than 53cm with a moderate or strong dynamic stress in laboratory due to an incomplete seismic subsidence of loess in this field. The seismic subsidence of toper loess layers is less than the below in the field test although it is opposite to in laboratory test due to closer distance between the below layers and explosion shots. © (2012) Trans Tech Publications, Switzerland.


Wang Q.,Key Laboratory of Loess Earthquake Engineering | Wang Q.,Lanzhou University | Wang Q.,Lanzhou Institute of Seismology | Wang J.,Key Laboratory of Loess Earthquake Engineering | And 9 more authors.
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2014

Taking Tianshui urban areas as an example, the results of dynamic triaxial liquefaction test on sand and undisturbed loess samples taken from the study area are analyzed. And the liquefaction characteristics of the soil in the valley cities located in the Loess Plateau are discussed. Moreover, liquefaction potential of the soil under the different equivalent intensity earthquakes are evaluated by using Seed-Idriss simplified discriminant method. In addition, the soil earthquake liquefaction disasters of the valley cities in the Loess Plateau are predicted in combination of topography and geological features. The results show that: the liquefaction characteristics of the saturated soil in loess plateau valley cities are different under seismic action. The liquefaction strength of it is quite lower because loess is a loose soil. So it can be liquefied when the seismic intensity rise up to VH degree. The liquefaction will not produce surface loess boiling, but it often leads to landslides and mudflow disaster. The liquefaction strength is mainly affected by the density and the plastic index of the loess. However, the sand will be liquefied when the seismic intensity is up to VIE degree. The liquefaction will produce surface sand boiling and lead to ground cracks, uneven settlement of foundation and instability or failure of buildings. Particle size is the main factor influencing sand liquefaction. The silt sand is more easily liquefied than the fine sand.


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.


Wang Q.,Key Laboratory of Loess Earthquake Engineering | Wang Q.,Lanzhou Institute of Seismology | Wang L.-M.,Key Laboratory of Loess Earthquake Engineering | Wang L.-M.,Lanzhou Institute of Seismology | And 3 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

Several compacted loess samples with different dry densities are prepared, which are the typical loess in Lanzhou City. The dynamic triaxial liquefaction tests are conducted by using the WF-12440 hollow cyclic apparatus. Through analysis of the experimental data, the relationship between liquefaction stress ratio and vibration times of the saturated compacted loess with different dry densities is proposed, the quantitative relationship of influence on liquefaction stress of saturated compacted loess by the initial void ratio is established, and the dynamic strain characteristics of saturated compacted loess with different dry densities are analyzed. Moreover, the critical liquefaction stress ratio and the critical dry density under different seismic intensities are calculated according to the Seed simplified procedure for liquefaction evaluation. The results are excepted to provide guidance for the anti-liquefaction treatment of the site in real projects.


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.


Ma W.,Lanzhou University | Ma W.,Ningxia University | Wang L.,Lanzhou University | Wang L.,Key Laboratory of Loess Earthquake Engineering | And 3 more authors.
Journal Wuhan University of Technology, Materials Science Edition | Year: 2016

The dynamic shear modulus G of soil was determined using a dynamic triaxial test system (DTTS) together with a fitting method. First, a novel linear relationship between G and damping ratio λ was proposed, which was used to select the appropriate G. Then, a hyperbolic model was constructed using the optimized parameters a and b representing the intercept and slope, respectively, from the linear regression of 1/G and dynamic shear strain γd. Finally, the differences between the tested and predicted results for G were analyzed for different soil types. The experimental results show that this linear relationship can overcome the shortcomings of the nonlinear relationship found in the large deformation stage and can predict λ in the hysteresis loop that is not closed case. In addition to Baoji loess, G was slightly larger (10%) than the experimental curve in the elasto-plastic stage; however, the experimental results show that the attenuation curve of G for Baoji loess is greater than the calculated value in the elasto-plastic stage. The test and analysis results will improve the knowledge of the dynamic properties of soils and also provide reliable values of G for further evaluation of seismic safety at engineering sites. © 2016, Wuhan University of Technology and Springer-Verlag Berlin Heidelberg.

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