Study On Clogging And Drainage Effect Of The Soft Permeable Pipe Used For Slope In Intermittent Seepage

As an important part of the slope engineering,horizontal drain system is crucial to ensure the stability of slope.Soft permeable pipe is a common part of underground drainage systems in recent years.At present,the researches on the soft permeable pipe in slope mainly focus on the drainage effect under the condition of the constant head,while the study on the effect of clogging and drainage under the intermittent condition is rarely involved.The climate in the southeast coast of China is warm and rainy,and the water level in the slope changes frequently.Therefore,the research on the effect of clogging and draining of soft permeable pipes under intermittent drainage is becoming a key scientific issue to be solved urgently,which can provide a reference for the actual slope engineering reinforcement.This master dissertation,aimed at a typical slope constituted by granite residual soil in Fujian Province,via the indoor slope physical model test,analyzed the value of soft permeable pipe flow and pore pressure of the slope under intermittent trailing edge recharge sufficient circumstances,utilized advanced Digital microscope equipment to observe and analyse the clogging area on the surface geotextiles of soft permeable pipe,studies on the clogging and drainage effects of soft permeable pipe.Based on the indoor model test,and united PLAXIS 3D numerical simulation,the drainage effect of soft permeable pipe and the variation law of the seepage field under the effect of clogging is simulated.The follows are the main achievements:(1)By analyzing the flow value of the permeable pipe and the pore water pressure in the slope soil under three different conditions include of two rows,one row and two pipes,the effect of fixed location and installation quantity of soft permeable pipes on slope stability is obtained.The experimental results show that the higher the installation position of the permeable pipe is,the weaker its drainage capacity is,the higher the groundwater level in the slope soil is,the worse the slope stability is.The less the installation quantity of the permeable pipe is,the smaller the amount of the drainage groundwater in the slope soil is,the higher the groundwater level and the poorer the slope stability is.(2)Observing and estimating the clogging area of the geotextile on the surface of the soft permeable pipe in different installation locations,different water-passing periods and different soil quality by digital microscope,the influencing factors of the clogging of the soft aqueduct are obtained.The experimental results show that the larger the flow rate of soft permeable pipe is,the smaller the degree of clogging is.The higher the content of fine particles in slope soil is,the larger the degree of clogging of soft permeable pipe is.The shorter the period of trailing edge of the water level changes,the greater the degree of blockage.(3)PLAXIS 3D modeling was established to simulate three conditions of the indoor slope model.The results of the indoor test were used to test the finite element analysis results.The-results show that the finite element analysis can simulate the indoor model experiment well when'modeling the constitutive model of the soil with Mohr-coulomb,and by comparing the results of finite element analysis under three operating conditions,The effect is most pronounced installing a row of soft permeable pipes at a deeper level below the groundwater,and the highest slope stability.(4)Based on the results of indoor slope model established by PLAXIS 3D,a practical engineering model on the slope with soft permeable pipes was established,and the slope stability under different layout modes,installation numbers and installation pitches in the actual project was studied.Finite element analysis shows that soft permeable pipe:installed in a row of with a spacing of I meter at the deeper position below the groundwater can retain the highest slope stability.