关键词: 分选环, 天山, 冻胀

Abstract: Field investigations have been carried out in the.empty cirque a the head of Urumqi River, Tian Shan,for the 1988-1991 period,in order to study features of sorted circles in different developmental stages and diversith of sorted circles in the same developemental stage.The features of the sorted circles have been analysed with the form of the sorted in the same devlopmental stage.The features of the sorted circle,grain size, water content,frost heave stone sorting,fabric and reference to wooden stakes inserted vertically into the ground.The results show that the sorting degree becomes much better; the influenced of frostheave decreases gradually; and the centre of sorted circles was covered by vegetation increasingly from the upper to lower sorted circles (from infant stage to old stage).Moreover, the general tendency of the frostheave is central frostheave>internal gutter frostheave>gutter frostheave in a sorted circle.The infant sorted circles developed near the material source region and the mature sorted circles were formed far from the source region in the same place.

Key words: sorted circle, Tian Shan, forst heave