Mechanism Of Silting In Drainage Holes Of Subgrade Slope And Development Of New Drainage Structure

Water is one of the important factors causing slope instability.The economic and effective drainage method in engineering is to drill drainage holes along the slope direction.However,with the increase of operation time,the clogging and failure of drainage holes are inevitable.Therefore,the research on the clogging mechanism of drainage holes and the development of new drainage structures have become the key to solve this problem.Based on the mechanism of drainage hole clogging,aiming at the characteristics of two types of drainage structures,the inclined drainage pipe and siphon drainage pipe,the structure is improved,and the easy maintenance drainage structure and siphon drainage self-starting structure are developed.The full-scale experimental model of subgrade slope drainage structure is established.Through the simulation of rainfall-drainage,the full-scale experimental study of subgrade drainage is carried out,and the feasibility of relevant technologies and equipment is verified.The development process of physical clogging of drainage holes is revealed.The filter effect and long-term drainage rate change trend of inclined drainage hole screen and geotextile are studied,and the siphon self-starting threshold is determined.The main results and conclusions of this thesis are as follows :(1)Through theoretical analysis and field experiments,the silting mechanism of drainage holes is revealed.Fine particles are deposited on the surface of geotextile to flocculate and consolidate.With the increase of time,the outer wall of drainage pipe forms an insoluble material structure.The fine particles in the soil are the main reason for the physical siltation of the inclined drainage hole.Moderately increasing the equivalent aperture of the geotextile on the outer wall of the drainage pipe is conducive to improving its anti siltation and drainage capacity.(2)Based on the silting mechanism and the structural characteristics of drainage pipe,the influencing factors of the long-term drainage capacity decline of drainage hole are analyzed,the pervious and inverted filtration methods of inverted drainage pipe are systematically studied,the traditional drainage pipe structure is improved,and the easy maintenance drainage structure is developed;In view of the shortcomings of the traditional siphon drainage structure,which is easy to be silted and difficult to start,its structure is improved,and a siphon drainage self starting device based on rainfall is developed.(3)The full-scale experimental model of drainage structure is established,including the automatic control subsystem of simulated rainfall and the monitoring subsystem of subgrade experimental model.Through the full-scale experimental simulation of the influence of the long-term drainage efficiency of the drainage hole and the silting period on the stability of the subgrade slope under the condition of heavy rainfall,it is found that the groundwater infiltration line and surface formed by rainfall infiltration is an irregular curved surface,and the guidance and discharge of the infiltration rainwater by the drainage hole changes the infiltration path of the rainwater.Through the response rate of each sensor of periodic rainfall,it is verified that the easy maintenance drainage structure is convenient for maintenance,It integrates the advantages of drainage and reverse filtration.(4)Through constant head,variable head and siphon drainage model tests,the changes of groundwater level of outdoor subgrade slope under different rainfall conditions are simulated,the long-term drainage rate and inverted filtration effect under the combination of screen and geotextile of easy maintenance drainage structure are verified,the preliminary conditions for self starting of siphon drainage are determined,and then the structural form of siphon drainage structure layout is improved.