The Model Test Of Niujiaogou Landslide And Research On The Evolutional Mechanism

Due to the vulnerable geological environment,geological hazards occur frequently in Huyi.Loess landslides are particularly widely distributed,which greatly threatens people's lives and property and the development of economy.For most of those landslides,slope excavation and continuous rainfall are the dominant factors.In this paper,we conducted a semi-similar model test on the Niujiaogou landslide(which is one of the typical landslides)and studied the formation and the evolution of it,from which we obtained valuable results shown as below:(1)The lithology of the landslide is loess,the lithology of the sliding zone is red clay,and the lithology of the sliding bed is mica quartz schist.(2)The uniform design method was used to prepare similar material that is suitable for the landslide.We selected clay,sand,barite powder,talc powder and calcium carbonate powder as the similar material ingredients,and then conducted the proportioning experiment for the sliding body and sliding zone.From which we elected the ratio(clay,sand,barite powder: water = 6:3:1:1.41)as the similar material proportion of the sliding body and the ratio(clay: sand: water = 2:8:1.35)as the similar material proportion of the sliding zone.(3)On the basis of the similarity theory,the similarity criterion is derived by the dimensional analysis method.Under the premise of similarity ratio 1:150,we built up the Niujiaogou landslide model under rainfall condition,and obtained the corresponding information of pore water pressure,earth pressure,displacements and deformation of the model,after which we analyzed the characteristics of the changes of those factors.(4)By comprehensive analysis of the characteristics of the changes of pore water pressure,soil pressure,displacements and deformation of the model,we obtained the evolutionary mechanism,which is: The landslide model--Rainfall--Continuous expansion of the range of saturated soil(the soil of the slope front saturates first)--Rainwater gathering in the slope front--The further decrease of the soil strength and the destruction of the structure – Partial collapse of the slope front – The enlargement of the slope surface – The shortening of the seepage path and the enlargement of the seepage--The development of tensioning crack in the trailing edge--The frequent change of the porewater pressure – The fracture formation in weak zone--Rainwater infiltration – The development and penetration of the crack--Multi-stage secondary small landslide--The destruction of the whole slope.(5)The Niujiao Gou landslide is a loess retrogressive landslide,which provides the basis for the analysis of the evolution of similar landslides and the reasonable prevention and control.