Time Cumulative Effect Of Loess Slope Stability

Northwest china are covered by vast loess and surface of typical areas are gullies. This place is the cradle of Chinese culture. In the tide of our economic construction, a lot of infrastructures are keep building, such as roads, bridges, tall buildings, but something was changing. More and more engineering geological problems appear there. At the same time we solve them with geological technology which take us plenty of money. The engineering experiences help us know mechanism of slope stability. Stress unbalance can’t make slope instability at once. But it would make the slope instability creep when parts of shear stress were disappearing. The other part of slope would get in next creep step and be unstable.The essay summarized the factors about time accumulate affection of loess slope. These factors include the loess itself own characteristics, and also include rainfall, surface runoff, groundwater, earthquake, vegetation, freezing and thawing, agricultural irrigation, housing construction, mines and other external factors.First, generate large imbalance of shear stress in the slope by changing the slope stress field or the physical and mechanical properties of rock and soil mass, and let the slope soil goes into the creep stage. Creep could redistribute the shear stress and dissipate eventually, it may also lead creep stiffness, sliding resistance increases and make the slope back into stress equilibrium phase eventually. The slope will be instability and destroyed when the creep goes into the stable and accelerated sliding stage.The secondly, with time passed by, the probability of slope was affected by some factors would rise. For example, times of freeze and thawing may be make the slope be limit equilibrium. If there is nothing unfavorable, the slope would be stable forever. With time pass by, the possibility of a earthquake happened would be rise. Earthquake can increase sliding force suddenly, and get the slope unstable.FLAC3D Software is used in geotechnical engineering. we chose mohr and cvisc from the 25 models to complete these numerical simulation. This helps us discuss the time cumulative effect of different shapes and different mechanic properties of the slopes.