Mechanical Clogging Problem And Improvement Method Of Landslide Drilling Drainage System

Drilling drainage system is the most widely used drainage technology in landslide control.It can be divided into two types:up-dip drain hole and down-dip drain hole depending on the direction of drilling.The up-dip drain hole is also called horizontal drainage.However,the down-dip hole cannot use the gravity to drain,and it is common to use the siphon to realize the power-free water body crossing transportation,that is,the siphon drainage.The landslide drilling drainage system goes deep into the slope body.During long-term use,the clogging problem is widespread,which seriously affects its service life and effect.Among them,the problem of clogging of the up-dip drain hole is prominent,and mechanical clogging is the main form of clogging.Therefore,it is of great significance for landslide control to investigate the clogging mechanism of horizontal drainage and fundamentally solving the clogging problem of drilling drainage system.Based on physical model experiments and theoretical analysis,this paper not only reveals the mechanical clogging mechanism and the clogging development process of horizontal drainage near the underground water table,but also proposes using the"down-dip drain hole-siphon drainage" to fundamentally solving the clogging problem of drilling drainage system.Meanwhile,the ability of the 4mm siphon drain to resist the blocking of fine-grained clay is explored.According to the above researches,some major achievements and understandings have been obtained as follow:(1)The root cause of mechanical clogging of horizontal drain hole is directly related to its working principle and engineering characteristics.The small elevation angle is the principal reason of clogging.Furthermore,intermittent drain and re-seepage problems also aggravate the clogging.(2)The mechanical clogging mechanism of the inclined drain hole can be divided into the sedimentation of sediment in the water flow and the flocculation of fine sediment.The clogging development process is divided into two stages:in the first stage,due to the small elevation angle and re-seepage problems of horizontal drain hole,the water flow velocity is small,and a large amount of sediment particles are deposited in the hole;in the second stage,the intermittent characteristics of the slope drainage make the deposited soil particles flocculate and solidify to form a dense and hard-to-wash structure.(3)The down-dip siphon drainage hole is conducive to collecting water and the flow velocity is more fast,and the mechanical clogging in the hole does not occur.At the same time,the model test results show that the 4mm siphon tube will not clogging in the actual engineering application.Therefore,the siphon drainage hole is an improved method that can effectively solve the problem of drainage and drainage of the landslide borehole.