Study On The Design And Mechanism Of Polyurea Composite Impervious System

The leakage of dam,tunnel,culvert,and aqueduct will not only cause water loss,but also affect the safety of hydraulic engineering.So the leakage of hydraulic structure contraction joint needs to be valued and solved.Aiming at the tunnel across Yellow River on mid-dle route of the South-north Water Transfer Project and the culvert at the Tianjin main line,Professor LI Bingqi proposed polyurea-composite impervious system(EP_DTEW),which adapts to humid environment,binds well with concrete,transforms well with contraction joint,environmental and non-poisonous.In this paper,Cohesive Zone Model(CZM)which belongs to damage-fracture mechanics is modelled,which is used to simulate the function mechanism of the impervious system and analyze the crack and contraction joint of hydraulic structure under various working conditions.Meanwhile,design guide and method to material and structure of impervious system is proposed.And it’s the first in domestic that CZM applied to simulate impervious system.The main contents are as follows:(1)The indoor pump-in test to polyurea-coat and joint sealing material of poly-urea-composite impervious system was conducted,and the curve between normal displace-ment of polyurea-coat and water pressure,and the curve between surface strain of joint seal-ing material and water pressure were obtained.The data provide a basis for determine the pa-rameters of model.The CZM could reveal the damage mechanism of composite impervious system through comparing the results from simulation with the data from test.(2)Modelling polyurea-coat impervious system of crack and contraction joint,which adapt to flexible anti-seepage coating of concrete surface,such as crack propagation result from concrete surface,construction joint and low-pressure contraction joint.The debonding failure model is simulated based on bilinear CZM and obtain the curve between pressure and normal displacement,which compare to the data from indoor pump-in test to receive the rea-sonable CZM parameters.In the further study,the relationship between surface coating thick-ness and water pressure is studied.Meanwhile,the influence of surface coating thickness,elasticity modulus and shear bond strength on debonding length are discussed under compo-site condition of water pressure and joint deformation.In terms of joint deformation condition,the influence of elasticity modulus on critical deformation is discussed.The conclusions pro-vide theoretical basis and method for the material and structural design to the flexible poly-urea-coat impervious system of concrete surface.(3)Modelling joint sealing material system of contraction joint,which adapt to high wa-ter pressure.The debonding failure model is simulated based on exponential CZM and obtain the curve between pressure and strain,which compare to the data from indoor pump-in test to receive the reasonable CZM parameters.In the further study,the influence of elasticity mod-ulus and Poisson’s ration on water pressure is studied,as well as the relationship between depth of joint sealing material and water pressure.Under the condition that joint deformation after water pressure,the critical deformation is discussed through the change of sealing mate-rial depth and contraction joint width.Under the condition that water pressure after joint de-formation,the relationship between water pressure and sealing material depth,mechanical properties are discussed.The conclusions provide theoretical basis and method for the materi-al and structural design to the joint sealing material system.In this paper,providing technical support for choosing reasonable parameters of interfa-cial CZM,and also supporting for predicting the water pressure and joint deformation of pol-yurea-composite impervious system when the interface is damaged in the failure process.The conclusions provide theory support and practical guidance for the impervious system.