Study On Drainage Effect Of Soft Pervious Pipes On Condition Of Rear Supply

The effectiveness of drainage system is an important factor to ensure the durability of slope engineering.Deep soft pipes is an important form of underground drainage system.It is widely used in many sorts of slope engineering of underground drainage measures.However,for some soil slopes,after a certain period of service,the drainage effect of the deep soft drainage pipe is obviously weakened or even does not drain,which may be a great threat to the stability of the slope.The study on existing slope engineering problems has not given sufficient consideration to the development and evolution of the drainage structure and the possible invalid process.So that there is a huge hidden risk on the slope safety and durability of the project.Therefore,Carrying out study on drainage effect of soft pervious pipes on condition of rear supply is of great theoretical and practical value to scientifically evaluate the effectiveness of the drainage system and guide related projects.In this thesis,the homogeneous soil slope of granite residual cohesive soil in Fujian is studied,basing on the basic theory of saturated-unsaturated seepage theory,applying the similarity principle,constructing physical model experiment of slope seepage in indoor.The effect of soft water pipe on seepage field in slope is studied.And the finite element software PLAXIS3D was used to build the model to further realize the three-dimensional seepage analysis.In terms of physical model experiment,under three conditions of giving constant head and stepwise variable water head and periodic stepwise variable head to the trailing edge of slope,the pore water pressure of the slope model and the seepage velocity of the soft water pipe are measured and recorded continuously and regularly.As the head of the slope's posterior margin increases,every monitoring point's pore water pressure value increases as approximately linear.The infiltration surface of groundwater is the shape feature of irregular surface.When the head of the slope's posterior margin is always kept constant,the seepage velocity changes in turn as follows:stationary period,rapid growth period,slow down period and stationary period.In the process of the head of the slope's posterior margin increases by period,the variation tendency of the seepage velocity of the soft permeable pipe can be divided into three stages which are stationary period,growth period and stationary period.In the process of the head of the slope's posterior margin changes both by period and in cycle,the original larger flow rate area eventually maintains a much larger flow rate of drainage,While the c original smaller flow rate zone will drain at a much smaller flow rate in the role of early head changes.Under the same conditions,the difference of the flow velocity of different permeable pipes is very big,so that part of the permeable pipes show reduced or no drainage effect of drainage.That is due to different initial structure of soil in different locations,the development and evolution process is different by the continuous role of seepage.In terms of numerical simulation,on the basis of physical model test of indoor slope,the finite element software PLAXIS3D was used to establish the model.The soft permeable pipe is modeled with large permeability soil column.The permeability coefficient inversion of the soft permeable pipe is carried out.And the great difference of the seepage velocity among different permeable pipes in the physical experiment is further simulated,verified and explained,the deformation of slope in different groundwater infiltration surface position is simulated as comparative study.It is concluded that there are big differences in slope deformation under different infiltration surface position,which can provide reference for rational selection of groundwater level in slope design.