IN-SITU MONITORING AND ANALYSIS OF THAW SLUMPING AND DEFORMATION IN GENTLE SLOPING GROUND OF PERMAFROST SOILS ON QINGHAI-TIBETAN PLATEAU

To study the deformation characteristics of the thaw slumping body at the alignment of K3035 in permafrost area of Qinghai-Tibet Platean,two deformation monitoring boreholes were instrumented with Geokon-603 clinometers,and one borehole lay in the non-sliding soil body while the other lay in the front part of the slumping soil body.Monitoring results of nearly one year show that the thaw slumping body developed in the slope of small dip angle has obvious deformation and its displacement mainly occurs in shallow soil area and decreases with depth.The monitoring results were verified by numerical simulations.The monitoring data comparisons between the thaw slumping body at the alignment of K3035(southern slope) and that at the alignment of K3057(northern slope) were carried out.With reference to both the leading edge and the rear edge of the thaw slumping body,the deformation of the former thaw slumping body is always greater than that of the latter.While in the slope with no thaw slumping(at the alignment of DK1139 of Qinghai-Tibet railway) the deformation is very limited.The difference indicates that on the one hand excavation is the direct factor causing thaw slumping,and on the other hand,because of thaw slumping,the soil body at the rear edge of the slope which is relatively stable originally will experience relatively large creep.