Study On The Mechanism Of Loess Landslide Induced By Side Pressure Under Collapsing

Heifangtai,Yongjing County,Gansu Province,is known as "the natural laboratory for landslide ",the predecessors do a lot of fruitful research around the mechanism of loess revealing the slippery mechanism of the irrigation,the freezing and thawing,the soluble salt and other effects.The area has caused serious collapsing due to the irrigation,and if the process of collapsing produces the side pressure and the pressure has a effect on the landslide,there is few studies on that.In this paper,the loess landslide in Heifangtai is studied by means of data collection,field investigation,laboratory test and numerical simulation.The characteristics of the pressure and it's mechanism are studied.The main results achieved are as follows:(1)Through the laboratory test,it's confirmed that the side pressure in the process of loess collapsing exists,and the characteristics of the lateral pressure of loess collapsible type and its variation are summarized.The indoor collapsing test is carried out by the K0 consolidation instrument different under different conditions to verify the objective existence of lateral pressure and the law of change.The results show that the lateral pressure increases linearly with the increase of the depth.With the increase of the water content,the lateral pressure increases after the consolidation stability and the side pressure after the collapse tends to a stable value.(2)The sliding effect of the side pressure of loess collapsing is simulated and analyzed.The FLAC3 D simulation software was used to establish the numerical model to simulate the displacement,stress and lateral pressure coefficient under different water content.The slope stability analysis was carried out under the different conditions.The simulation results show that the maximum displacement is 1/3 of the slope.It is obvious that the effect of the lateral pressure on the slope stability.By simulating the distance of the irrigated area from the slope,the safety distance of the irrigation is discussed.when the distance is more than 63.5m.The effect of the lateral pressure on the stability is small.(3)Revealing the slip mechanism of the lateral pressure.On the basis of experiment and numerical simulation,The induced mechanism of the lateral pressure on the loess landslide is analyzed,and the tensile stress is generated in the upper part of the soil,resulting in the formation of the collapsing cracks,which is easy to form the posterior wall of the landslide.The compressive stress is generated in the lower part of the soil stress,resulting the extrusion of the soil,increasing the sliding force,and promoting the formation of landslides.