Dynamic Response And Stability Analysis Of The Embankment On Slopes In Permafrost Regions

Complicated geological conditions in permafrost regions, in particular, permafrost and seasonal frozen soil are the key issues to construction and stability of engineering. The completion and operation of the Qinghai-Tibet Railway has a major political and economic significance. However, the highest intensity of seismic activity in Qinghai-Tibet Plateau must be considered. Dynamic response and stability analysis of the embankment along the slope section of Qinghai-Tibet Railway are researched in this paper. The main conclusions are as follows:On-site soil samples are mainly consisted of silty clay and gravel. The frozen soil strength increases linearly with the decreasing of the temperature. The frozen soil strength decreases with increasing water content. And with the water content increasing, the decreased intensity of strength gradually reduces. Under the conditions of confining pressure<2Mpa, the frozen soil strength changes in a small range.Dynamic elastic modulus of the frozen soil increases with the decreasing temperature. And the temperature is more important as influencing factor than confining pressure. Under the higher water content conditions, dynamic elastic modulus decreases with increasing water content. However, dynamic elastic modulus increases with increasing water content under the lower water content conditions.Triaxial shear tests and saturated soil triaxial compression tests show that the shear strength of saturated soil decreased significantly.Under dynamic loading, laboratory model test of embankment on slopes in permafrost region is carried out. The studies show that the water of embankment and slope infiltrates along with the gradual deepening of freeze-thaw interface by the action of gravity. And the water is enriched at the toe along the freezing interface. The strength of the soil reduces because of high water content of freeze-thaw interface. Under dynamic load conditions, the destruction form of roadbed and slope is mainly longitudinal cracks along the slope and embankment. Another mainly form is dislocation slip along the potential sliding surface. And the potential sliding surfaces are mainly distributed in freeze-thaw interface, the interface of soil and the toe. For the stability of embankment on slopes in thawing period, the main influencing factors are the slope gradient, dynamic stress on embankment surface and the distribution of water.The numerical simulation is carried out to analyse stability of embankment on slopes in permafrost regions under earthquake loading. As for the deformation, shear strain and displacement of the whole model, the velocity and acceleration of the key points, high-frequency seismic wave impacts more significantly than low-frequency wave. That is to say, high-frequency seismic wave is more dangerous to the stability of embankment on slopes in permafrost regions. And subgrade cross section type is also an important factor to the stability of embankment. The maximum lateral displacement arises at the surface of roadbed, and the maximum shear strain arises at the freeze-thaw interface.The simulation results of stability of embankment on slopes in permafrost regions under train load show that the main impactive depth of vertical displacement increases with increasing slpoe gradient. The most obvious deformation and the maximum shear strain arise at the saturated silty clay. In a word, the saturated silty caly and the slope gradient are the key factors to the stability of embankment.The stability of embankment on slopes is considered as a special form of embankment stability in permafrost regions. And the AHP-Fuzzy synthetic evaluation method is adopted in the thesis. In the analysis of stability of roadbed in permafrost regions by AHP-Fuzzy synthetic evaluation model on the basis of reliability, the relationships of each influencing factor are completely considered. And the stability of roadbed is not only evaluated qualitatively but also given the accurate evaluation score. This method is effective to evaluate the stability of roadbed in permafrost regions.