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Abstract Microscopic analysis of soil mesostructure and direct shear test for Q2 loess with different water contents under different freezing speeds are conducted. The results show as follows：(1) When the water content of loess sample is low，with the increase of freezing speed，the statistical frequency of low-density area increase a little，while the statistical frequency of middle-density area scarcely changes and that of high-density area decreases a little. So the freezing speed has little effect on each density area of Q2 loess. When the water content of loess sample is higher，the freezing speed has great impact on high-density and has little impact on low-density area. The greater the water content is，the greater the impact is. (2) When the freezing speed is slow，the effect of water frost function on the behavior of loess is not obvious. When the freezing speed is faster，the water in loess freezes before it migrates to the loess sample? freezing front；and the water frost heaves in loess. When the volume of ice is larger than its expansion in the loess free space，the volume of loess increases a little；and the density and cohesion decrease because the water in loess frost heaves. The greater the water content is，the greater the volume increase，and the greater the decreasing degree of loess sample?s density and cohesion are. The frost heave force makes the proportion of large pore in loess decrease and the contact points between particles of soil increase，which make the internal friction angle of loess increase. The faster the freezing speed is and the larger the water content is，the greater the increment of internal friction angle is.
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Received: 04 March 2011
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2011, Vol. 30 
