Study On Mechanical Properties Of The Accumulation Layer Landslide Micropile Reinforcement Under Pile Toprigid Connections

In recent years,micropiles have been widely used in the field of landslide control and have achieved effective results.However,in some mountainous areas with heavy rainfall all the year round,many small and medium-sized accumulation layer landslides occur every year.Roads are washed away and farmland is buried by the landslide mass due to the narrow and uneven mountainous areas.For small-scale landslides,the use of traditional supporting structures have the disadvantages of high cost,large occupied area,complex construction and so on,while the emergence of micropiles have undoubtedly solved these tricky problems.In some landslide-affected areas,the post-disaster road projects need to be renovated.Due to the limited construction sites available,many roads must pass through the landslide mass,with some projects have to be built on the potential landslide mass,which has created many difficulties for the construction organizations.Therefore,some construction organizations choose to use micropiles to treat landslide first,and then take the micropiles as pile foundations to further build production and construction roads at the top of the pile to bear the loads from the vertical direction(pile load,vehicle load,etc.).This has undoubtedly extended the function of micropiles,making "one pile for multiple purposes" possible.In this way,we have not only treated the landslide,but also made use of the combined action of piles and soil to form "pile foundation" to bear the vertical loads from the production roads built above.However,in the aspect of "one pile for multiple purposes",the construction organization often conduct the construction according to previous experiences without corresponding theoretical research and specifications,which poses certain potential risks to the project and construction personnel.By researching the documents both at home and abroad,the author found that most of the documents are single-purpose researches on the treatment of landslide by micropiles,but there are very few documents on the study of using micropiles to treat landslide while building production and construction roads on the top of the micropiles simultaneously.Based on the similarity theory,the production road built at the pile top is simulated as a rigid plate,and its mechanical properties of the accumulation layer landslide micropile top under rigid connections are studied through indoor physical simulation experiments.It has certain reference value for the application of micropile theory in practical landslide engineering,and has certain theoretical guidance for the building of production roads on top of micropile while controlling landslide.This thesis mainly focuses on the following aspects:The conclusions of the research obtained through this paper are:1)The development characteristics and influencing factors of the landslide are analyzed.The mechanism of the reinforced landslide of the micro-pile under the rigid connection and the connection form of the rigid plate and the pile are studied.2)Through physical simulation experiments,each group of experiments under the same landslide thrust,the displacement of the top of the slope is greater than the displacement of the top of the pile,and the displacement of the top of the pile is greater than the displacement of the foot.Under the action of the maximum landslide thrust,the rigid pile connection,the rigid connection of the micro-pile and the 4kPa load applied on the pile top and the displacement of the top of the rigid pile with the 8kPa load on the top of the micro-pile are reduced by 18.05%.36.58%and 47.61%,the displacement at the top of the pile is reduced by 6.24%,39.72%and 43.49%,and the displacement at the foot of the slope is reduced by 19.12%,38%and 42%,respectively.The sliding body slides down.3)Under the action of maximum landslide thrust,the micro-pile rigid connection,the 4kPa load applied to the top of the rigid pile of the micro-pile and the 8kPa load applied to the top of the rigid pile of the micro-pile,the maximum bending moment of the first row of piles above the slip surface is compared with the independent miniature The piles were reduced by 4.57%,21.95%and 37.77%in turn;the second row piles were reduced by 12.43%,25.08%and 34.04%respectively compared with the independent micropiles;the third row piles were reduced by 1.94%and 19.74 respectively compared with the independent piles.%and 23%,by applying a load on the top of the pile,the maximum bending moment value of the pile body can be effectively reduced,and the bending moment distribution of the pile body is more uniform.4)The earth pressure in front of the pile gradually increases with the depth of the pile,reaching the maximum near the sliding surface.The soil pressure behind the pile shows a decreasing trend with the depth of the pile,just opposite to the earth pressure before the pile.Basically,the earth pressure in the first row of piles is greater than that in the second row,and the earth pressure in the second row is greater than the third row.By applying a load on the top of the pile,it helps to improve the uneven distribution of earth pressure along the pile body,and can improve the stability of the entire micro-pile composite structure.5)The numerical simulation method is used to evaluate the effect of landslide control under the rigid connection of micro-pile.The relationship between the applied load at the top of the pile and the load on the top of the pile is further studied,and the load diagram of the top load and the pile top load are drawn.However,whether the pile top affects the landslide reinforcement under the dynamic load needs to be further explored.