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Study of the Dynamic Deformation Properties of Loess Under a Dynamic Load in the Lanzhou Metro
(1 Key Laboratory of Loess Earthquake Engineering, Lanzhou Institute of Seismology, CEA, Lanzhou 730000; 2 Schools of Civil Engineering and Mechanics, Lanzhou University, Lanzhou 730000; 3 Geotechnical Disaster Prevention Engineering Technology Research Center, Lanzhou 730000)
Abstract Dynamic triaxial tests of loess samples from the Lanzhou Subway Line 1 were performed under subwayincluded dynamic loadings with different dominant frequencies and a constant cyclic dynamic loading with the fre? quency of 1 Hz. With the comparison of test results, we analyze the dynamic stress-strain relation, dynamic shear modulus ratio and damping ratio characteristics of the loess under the effects of dynamic load and also study the accumulated deformation properties of loess under cyclic loading. The results show that vibration frequency has an obvious influence on the dynamic behaviors and cumulative plastic deformation of the loess—with an increasing vibration frequency, the dynamic stress required for achieving a certain stage of deformation increases significantly. With a smaller vibration frequency, the dynamic shear modulus ratio decreases more rapidly with an increase of the dynamic strain; with the same dynamic shear strain, the Gd/Gdmax is smallest while at a vibration frequency of 2.5 Hz,and it reaches maximum dynamic stress and Gd/Gdmax under the same dynamic strains. Moreover, the cumulative plastic deformation of the loess under dynamic loadings with different vibration frequencies could be split into three stages, which are: the rapidly-deforming stage, the slowly-deforming stage, and the fundamentally-stable stage. However, in the slowly-deforming stage and the fundamentally-stable stage, vibration times required to achieve a certain deformation will increase with the increase of the vibration frequency. Dynamic loadings from a subway with a vibration frequency between 0.4 Hz and 0.6 Hz have the most serious influence on the deformation of loess in Lanzhou.
Abstract：
Dynamic triaxial tests of loess samples from the Lanzhou Subway Line 1 were performed under subwayincluded dynamic loadings with different dominant frequencies and a constant cyclic dynamic loading with the fre? quency of 1 Hz. With the comparison of test results, we analyze the dynamic stress-strain relation, dynamic shear modulus ratio and damping ratio characteristics of the loess under the effects of dynamic load and also study the accumulated deformation properties of loess under cyclic loading. The results show that vibration frequency has an obvious influence on the dynamic behaviors and cumulative plastic deformation of the loess—with an increasing vibration frequency, the dynamic stress required for achieving a certain stage of deformation increases significantly. With a smaller vibration frequency, the dynamic shear modulus ratio decreases more rapidly with an increase of the dynamic strain; with the same dynamic shear strain, the Gd/Gdmax is smallest while at a vibration frequency of 2.5 Hz,and it reaches maximum dynamic stress and Gd/Gdmax under the same dynamic strains. Moreover, the cumulative plastic deformation of the loess under dynamic loadings with different vibration frequencies could be split into three stages, which are: the rapidly-deforming stage, the slowly-deforming stage, and the fundamentally-stable stage. However, in the slowly-deforming stage and the fundamentally-stable stage, vibration times required to achieve a certain deformation will increase with the increase of the vibration frequency. Dynamic loadings from a subway with a vibration frequency between 0.4 Hz and 0.6 Hz have the most serious influence on the deformation of loess in Lanzhou.
WANG Qian- 1,
2,
3 Zhong-Xiu-Mei- 1 etc
.Study of the Dynamic Deformation Properties of Loess Under a Dynamic Load in the Lanzhou Metro[J] MODERN TUNNELLING TECHNOLOGY, 2016,V53(6): 137-142
2016, Vol. 53 