Stability Analysis Of Slope Protected By Soil Nailing Under Seasonal Freezing And Thawing

Currently, research on soil-nailed slope is relatively mature, and has been applied widely in slope and foundation pit engineering. However, in the seasonal freeze-thaw area with complicated geological conditions and obvious temperature difference between the four seasons distinct, slope and structures often occur freezing and thawing as the seasonal temperature changes, and the slope damages under the action of freeze-thaw cycles, which brings various degrees of damages to the slope engineering and causes huge economic losses. Therefore, it is very necessary to study on the safety stability calculation method of supporting structure under the action of freeze-thaw. This thesis studied the safety stability method of soil-nailed slope under the influence of freezing and thawing, and the formula of safety cofficient for slope is derived. Its practicality is also verified combined with engineering application. Main contents and achievements of the research are as follows:(1)Soil-nailed slope failure under the action of freezing and thawing is a more complicated problem. Through elaborating the mechanism of freezing and thawing action,the influence on mechanical properties that the freezing and thawing applied on soil-nailed slope is analyzed, and the reasons caused by frost heaving damage and melting damage of soil-nailed slope is derived also, putting forward corresponding prevention and control measures of two failure modes, using double steel mesh method set the sparse dry drains, surface slope replacement method, soil nail wall reinforcement method, compartment temperature method, high ductility of soil nailing method and ecological protection measures.(2)Combined with the stability theory of soil-nailed slope and the theory of limit equilibrium method, the slope safety coefficient calculation formula of soil-nailed slope in the phase of melting stage and freezing is derived, the most dangerous slip surface position under the action of freeze-thaw of soil nailing structure is conformed. Soil-nailed slope role in the stability of freeze-thaw cycles season is predicted. Combined with the engineering examples, and the results of the melting stage safety factor formula and finite element calculation software Geostudio are also compared,some valuable conclusions are obtained. Analysis results show that: the safety factors calculated by formula are smaller than finite element software results, and the results tend to be conservative, the formula can be more accuracy on the soil nailing slope design and stability analysis.(3)Based on the theory of seasonal frozen soil, the slope of the moisture and temperature field differential equation are solved by the finitedifference method, and provide a foundation for the establishment of the finite element model of the freezing thawing process.(4)Combined with the professional geotechnical engineering numerical analysis software Geo-Studio and ADINA, a seasonal freezing and thawing of soil-nailed slope finite element model is established. The results show that: in the melting phase of soil-nailed slope freeze layer, with the increase of water content, the safety factor is getting smaller and smaller, indicating that the increase in water content after freezing and thawing of soil nailing is main reason to cause slope instability.The examples demonstrate that: the calculation method that considering the action of freeze-thaw effect is relatively reasonable, and the calculation method accords with the engineering practice, this method can provide a beneficial reference for the future construction, design and optimize of the slope protected by soil nailing.