Physical Model Test Of Anti-slip Micro-pile

Micro-piles are gradually used in landslide management projects because of their small diameter,flexible pile laying form and good adaptability to various soil layers and easy construction.However,since micro-piles were mainly used in building foundation projects,domestic and foreign research on them mainly care about of the vertical capacity of micro-piles,but the research on horizontal bearing performance of micro-piles was lacking.In the landslide management project,mini-pile mainly plays its horizontal bearing capacity.At present,in the process of landslide control,there is a lack of research on the deformation and damage mode of pile body and the calculation of force in pile body,which leads to the application of micropile practical engineering.Through physical model test and theoretical analysis,this paper studies the deformation and damage mode of micro-piles under landslide thrust,the change of soil pressure around piles and the distribution of force within piles.In the physical model test,a physical model test box for reinforced slope with micro-piles was designed and processed,and two sets of model tests were conducted: single-row miniature pile model test and double-row micro group pile model test.The model micro-piles used for reinforcement in both sets of tests were made of c20 reinforced concrete,with a total length of 180 cm and a diameter of 5 cm,and the landslide models used for reinforcement were identical in size and filling materials.By analyzing the two sets of test results,we found that the deformation and damage patterns of single-row micro-pile structure and double-row micro group pile structure under the action of landslide thrust are basically the same.The final deformation of the pile body is "S" shaped,the pile body bending deformation is mainly concentrated in the vicinity of the slip surface.The single-row micro-pile structure pile bending deformation area is about 1/4 of the total length of the pile,and the bending deformation area of double-row micro group pile structure is more about 3/10 of the total length of the pile.The pile body as a whole will also produce certain rotational deformation,and the rotational deformation of the pile body is basically the same in the two groups of tests.With the center of rotation located at 1/3 of the pile length of the anchored section at the bottom of the pile,and the rotation angle is around 3°.Secondly,due to the influence of pile bending and rotational deformation,two debonding areas were formed before and after the pile body near the slip surface.Under the horizontal load,the soil pressure variation pattern and soil pressure distribution at each measurement point around the pile body of the two groups of test micro-piles are also basically similar.The soil pressure behind the pile in the loaded section of the micro-pile is triangularly distributed,and the soil pressure in front of the pile in the anchored section is inverted triangularly distributed.In addition,the distribution of shear stress and bending moment of the micro-pile body under both conditions is symmetrical,and the shear stress and bending moment of the pile body at the location of the slippery surface is the largest,which is consistent with the actual deformation of the pile body.Comparing the two sets of test results,we found that the double-row micro-piles structure can withstand more landslide thrust and has a better reinforcement effect on the landslide body.Secondly,in the process of resisting the landslide thrust,the impact on the soil around the pile is wider and the damage caused is more serious.Therefore,in the actual landslide management project,the corresponding slope top and slope surface protection measures should be used.In addition,under the action of landslide thrust,the front and rear rows of piles are deformed at the same time,and the ratio of landslide thrust shared by the front and rear rows of piles is about1:2,and the rear row of piles near the direction of landslide thrust bears more landslide thrust.