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Study on Liquefaction Characteristics of Silty-Fine Sand and Liquefiable Ground Treated by Gravel Pile Composite Foundation

Author: YangJuMing
Tutor: CaoXinWen
School: Southwest Jiaotong University
Course: Road and Railway Engineering
Keywords: Fine sand Liquefaction Gravel Pile Composite Foundation Dynamic triaxial test Numerical Simulation
CLC: U213.1
Type: Master's thesis
Year: 2008
Downloads: 234
Quote: 4
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Abstract


New River railway from Kunming, Yunnan Province, Kunming Sino-Vietnamese border to the mouth of a total length of 380km, is the Chinese railway lines connecting Vietnam and Southeast Asia, on the formation of long-term railway network plan, to promote economic and social development of great significance. Kun River Railroad large area of ??fine sand along the distribution of liquefied soil, and the majority located in 8 degree earthquake zone. Under earthquake liquefaction are likely to occur. Liquefiable ground liquefaction, lateral flow and embankment damage caused by the Queensland River railway embankment settlement will cause serious damage. To this end, the foundation of saturated silty sand liquefaction mechanism to evaluate liquefaction impact of the railway foundation, establishing reasonable economic strengthening methods for liquefaction River Queensland railway construction has great significance. In this paper, the dynamic triaxial tests on Queensland Rail Pass Hai River basin were fine sand liquefaction tests. Experiment using two different dry density analog reinforcement before, reinforced foundation, three different confining pressure to simulate different depths stratigraphy, by testing the dynamic strain, pore water pressure and other data to study the fine sand layers at different depths before and after reinforcement liquefaction resistance, pore water pressure and the dynamic modulus of variation. The results showed that: fine sand liquefaction resistance increases with the dry density; with drainage condition varies. Undrained conditions, the pore water pressure during the test reached the maximum confining pressure of 90%. Partially drained conditions, can only reach about 70% of the confining pressure. Partially drained fine sand liquefaction under undrained condition improved strength than 22.8 percent. Dynamic shear modulus dynamic strain was attenuated growth trend, with the confining pressure increases. Establish a software dynamic triaxial tests FLAC numerical model under different experimental conditions dynamic triaxial tests were carried out dynamic numerical simulation. The numerical results obtained with the dynamic triaxial test dynamic pore pressure trends are basically the same, consistent with the initial liquefaction time, indicating that in accordance with the dynamic triaxial test parameter extraction method is reliable, using the parameters in line with the actual situation, but confirmed the model in FLAC Finn analysis of the applicability of liquefaction and the reasonableness of the selected parameter. In Queensland River Railroad DK23 work site for the prototype, the establishment of undisturbed ground and gravel pile composite foundation finite difference model to El Centro earthquake wave as the input wave to study undisturbed ground and gravel pile composite foundation of pore water pressure, ground deformation Ji Luji With the seismic loads and other dynamic changes in response to the gravel pile composite foundation liquefaction resistance were evaluated. Studies show that: In the case of the earthquake of 7 degrees, the status quo does not meet seismic design requirements foundation shall be reinforced. Gravel pile composite foundation and inhibition can be effectively dissipate excess pore water pressure rises and the pile of soil liquefaction, improved foundation liquefaction resistance, and can effectively reduce the foundation, roadbed under seismic loads in the settlement, improve the level of ground deformation resistance ability to meet the requirements of seismic design of 8 degrees.

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CLC: > Transportation > Rail transport > Railway Line Project > Line constructed > Subgrade
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