Analysis Of Model Test Of CFG Group Piles In Permafrost Areas

Permafrost is widely distributed in northeast and northwest part of China. Because of thermodynamic instability of frozen soil, it has bad influence on the stability of the construction in permafrost regions, and causes serious harms to traffic and transport safety. It has very important practical significance to apply the CFG pile composite foundation in permafrost regions, for the CFG pile composite foundation has the project characteristics such as wide applicability, big improvement of bearing capacity, simple construction, short time limit, and low cost and so on. So it is the most important to research the temperature field distribution and mechanical properties of CFG pile composite foundation in the permafrost regions.This paper first introduces the research status and prospect of CFG pile, the permafrost and soil-pile interaction, making clear the research content and methods. Combined with the special properties of the permafrost, it is mainly to solve the problems in two aspects; one is the temperature field changes of CFG pile shaft and the permafrost around the piles, the other is the bearing capacity of the CFG pile composite foundation in the permafrost regions. Based on above, this paper does the following work:1, Summarize thermal and mechanical properties of permafrost; conclude basic theories of CFG pile composite foundation, heat transfer theory, interaction between pile foundation and permafrost, which lay the foundation for indoor model test and theoretical analysis.2, Understand indoor model test theory, make preparation for model test, build indoor temperature test model and bearing test model, meanwhile make temperature observation and bearing test; organize and analyze measured data, then the author came to the conclusion of the influence of CFG pile groups concrete's hydration heat on pile foundation and permafrost temperature field; the author also sums up situations of axial force of CFG pile groups, skin friction, pile group settlement and proportion of loads carried by the piles and the soil.3, Use ABAQUS software to establish the temperature and bearing test models on the basis of indoor model test actual size and soil horizon conditions. Compare the numerical calculation results with measured value in order to verify the applicability of ABAQUS. Then use ABAQUS to analyze problems such as pile group temperature field's influence scope, the influence on the temperature field of CFG pile composite foundation based on different mould temperature of the concrete, the effects on pile group P-S curve based on different concrete elastic modulus and different permafrost elastic modulus.