Study On The Failure Of Silty Sand Slope Under Different Seepage Boundary Conditions And Fiber Reinforced Control By Model Tests

Among all kinds of slope structures,silty sand slope has the characteristics of large void ratio,strong permeability and obvious collapse.Under the action of seepage,silty sand slope is easily destroyed,with serious consequences.Because silty sand is prone to saturated static liquefaction under the state of loose and low confining pressure,the main landslide prevention methods such as retaining wall,anchor bolt,concrete lattice beam and grouting are not effective for silty sand slope and they can affect the ecological environment.Therefore,it is of great academic value and practical significance to explore the instability characteristics and reinforcement mechanism of silty sand slope under seepage.Based on this,the preliminary study is carried out through the indoor model test of slope and unit test.The main research contents and results are as follows:(1)An indoor slope model test system is developed,which can effectively simulate different seepage boundary conditions.(2)Stability tests of silty sand slope are carried out under different seepage conditions.The results show that the damage caused by rainfall infiltration at the top of the slope is local shallow failure,and the damage range is concentrated in the middle and lower part of the slope.The damage caused by rainfall infiltration at the top and the surface of slope is a composite failure of block sliding and flow sliding.The damage caused by lateral seepage of high water level is multi-stage retrogressive failure,and the degree of damage is relatively serious.The damage caused by bottom water infiltration is surface sliding failure.(3)Triaxial drainage and undrained shear tests were carried out on silty sand reinforced with small amount of polypropylene staple fiber.It is found that the shear strength of fiber reinforced soil is significantly higher than that of bare soil.With the increase of fiber length and content,the stress-strain relationship of soils tends to change from weak softening to weak hardening and then to complete hardening,and the failure mode of soil changes from flow-slip failure to bulging failure under undrained condition.(4)Based on the validity of fiber reinforced,fiber reinforced silty slopes are established and their instability characteristics under lateral seepage are studied.The results show that the fiber reinforced slope can obviously reduce the damage degree of bare soil slope under the influence of lateral seepage.The main manifestations are that the cracks at the toe of the slope expand slowly and do not extend,the velocity of the collapsed sliding body slows down,and the volume also decreases.With the increase of fiber length and content in reinforced area of slope,the failure of slope changes from large area to local failure and then to no obvious structural failure.The feasibility of fiber reinforcedment in slope reinforcement is demonstrated.