MECHANISM AND PREVENTION OF DEFORMATION CRACKS OF EMBANKMENTS IN THE PERMAFROST REGION ALONG QINGHAI-XIZANG RAILWAY
Zhang Luxin Yuan Sicheng Yang Yongping(Civil and Architecture Engineering College,Beijing Jiaotong University, Beijing 100044; Qinghai-Xizang Railway Construction Management Center, Golmud 816000)
In the first two frost-thaw cycles after construction of embankments in the permafrost region along Qinghai-Xizang railway, part of testing embankments and part of the construction′s embankments show different degrees of secondary engineering diseases (deformation cracks on the slope and top of embankments ) caused by cryogenic process of permafrost. For investigating deformations and cracks derived from deformations of permafrost embankments, we study and analyze the temperature sub-area of permafrost, the ice content in frozen soils and shape of embankments′ structures. We find that the deformation of embankments actually is composed of compress deformation of soil under embankments and the embankments itself, deformation of thaw settlement during frost-thaw cycles and deformation of frost heaving. Thaw settlement, frost heaving deformation of embankments and the surface change caused by these deformations, as deformation cracks, are results of cryogenic process or cryogenic phenomenon of permafrost from essence of engineering geocryology. There are two kinds of deformation of railway embankments, transverse cracks and longitudinal cracks. Geometry asymmetry and difference of slope direction cause the difference of temperature, shape asymmetry of permafrost table and variation of thaw-frost pace under railway embankment. This is the direct reason of deformation cracks on railway embankments. Therefore, we put ripped-stone and gravel protection slope structures in order to reduce heat passing into ground. At the same time, using the different effect of diverting heat and hiving cold to different size of ripped-stones and gravels, we correct asymmetry of temperature fields and variation of thaw-frost pace so as to control the development of the cracks. These engineering measurments have been widely used in the design and construction of the embankment in the permafrost area along the Qinghai-Xizang railway.
【CateGory Index】： U216.417