The Effect Of Freezing And Thawing On The Stability Of Rock Pile Slope In Cold Area

With the promotion of one belt and one road policy, foundation engineering of infra-structure projects in alpine and large temperature difference region starts in recent year, as well as the low-temperature geotechnical of mechanical problem shall be well emphasized. Considering the specialty of talus slope in the cold region, the difficulty of design and construction, and long period of treatment, there is plenty of theoretical and practical significance to research the stability of freezing-thawing effect by talus slope.Based on the research of characteristic and disposition technology of talus of Da Qian Shi Ling Talus slope in Tian Huan Railway Project. The stability of talus slope is researched by theoretical calculation formula, on-site topography exploration, on-site freezing-thawing laboratory test and PFC2D numerical simulation etc.The research contents and conclusion are as bellow:(1) Deduce the calculation formula for the residual thrust method of frost-heaving force and seepage force and calculation the stability under different working conditions of the actual talus slope.The safety factor of implicit solution of talus under natural state is Fs=1.27. The internal friction (p add 1°, safty factor Fs will add 0.045. Cohesion force c add 1kPa, the safety factor Fs will add 0.007. The safety factor Fs shall be 1,2/3,1/2,1/3,with increasing sequences, which is also anhydrous naturally. Under the effect of frost heaving, the safety factor of talus shall be decided by value of 6v,? after the freezing of the slop slip surface comprehen-sively.(2) Based on the on-site topography exploration, and establish large-scale laboratory, analog the stability of talus slope under freezing-thawing effect. The stability of talus slope shows trend of "stable?unstable?new stable?new unstable". After excavation, in the process of preliminary freezing-thawing, it's mainly tumble or slip of the slope surface. In the process of repeatedly freezing-thawing, talus is in state of stability generally, but there will be abrupt large-scale collapse if the slope is very steep.Rock fracture are in elasticity state of "frost heaving and thaw shrinking" in 20 times tests.(3) Calculate stability of talus slope in labatory test by discrete element PFC2D software.When expansive force is deep inside, the bigger of the slope angle, X,Y axial translation will be more serious and Y axial translation will be more serious than X axial. In the middle or late period, frost heaving force released centralized, with cyclic process of "grow?release-grow" and continuous growth. In the front of the talus slope, the frost heaving force released in time with fluctuation phenomenon while the growth range is very small.The frost heaving force comes from the deeper embedded position firstly. During the process of frost heaving, the force is transmitted downward and upward simultaneously along with the dip angle in the frost heaving stratum. The force of middle stratum is largest, while the forces of two sides are decreased gradually. The force will be Zero when the frost heaving stratum comes out the surface of the talus slope.In the conclusion, analyzing the stability of talus slope with frost heaving effect by methods of general calculation, external test phenomenon, and inside frost heaving force etc., provides reliable basis of design and construction of talus slope in cold region and reference for similar future projects.