Study on orthogonal test on the influence factors of frost depth and frost heave deformation of moraine soil in Chada Gully,Xizang
The presence of large amounts of moraine soil in the Chada Gully of Xizang,China,with the devel-opment of the western regions,there will be numerous infrastructure projects built on moraine frozen soil founda-tions.To investigate the influence factors of frost depth and frost heave deformation of moraine soil in this area,carry out multi-factor and multi-level unidirectional freezing tests under the open system indoors through orthogo-nal design,having investigated the effects and magnitude of the significance of different factors on frost depth and frost deformation of moraine soils under unidirectional freezing conditions in an open system,at the same time,analyzed the redistribution of moisture in the moraine soil at different heights after freezing,and estab-lished the multivariate linear regression equations of multi-factors with the frost depth and frost heave deforma-tion.The study shows that the most significant factors affecting frost depth and frost heave deformation are freez-ing side temperature and initial volumetric water content,respectively.The significant influence of each factor on frost depth is as follows:freezing side temperature>freezing time>freezing side cooling rate>initial volumet-ric water content>compaction,of which the freezing side temperature(negative temperature)and freezing time are positively correlated with the frost depth,and the other three factors have a small influence on it.The influ-ence on frost heave deformation is as follows:initial volumetric water content>freezing side temperature>com-paction>freezing time>freezing side cooling rate,and initial water content is positively correlated with the freez-ing side temperature and the frost heave deformation,compaction is negatively correlated with it,and the cool-ing rate and freezing time have less influence on it.Due to the large pores of the solid particles of the moraine soil,the freezing process moisture continues to migrate to the cold end,and free water and gaseous water form a poly-ice layer at the cold end.When the temperature of the cold end is low and the freezing time is long,there exists a freezing edge 3～8 cm above the freezing front,the soils here are saturated,with large amounts of free ice and free water,which is the key area for water migration and water-ice phase transition,when the bottom of the soil body is recharged,this area acts as a water storage zone further exacerbating the frost heave of the soil body.According to the orthogonal test results,a multiple linear regression equation was established to effective-ly predict the frost depth and frost heave deformation of the moraine soil in this area under the influence of multi-ple factors,and this equation can be utilized in the engineering field to quickly classify the freezing grade of the soil body.The results of the study have certain reference values for the safety evaluation and anti-freezing design of moraine soil projects in the relevant area.
open systemunidirectional freezingfrost depthfrost heave deformationorthogonal test
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