Study On Permeability Of Cracked Concrete Under Underwater Tunnel

The durability and service life of tunnel concrete in underwater environment are seriously challenged.The seepage of the tunnel structure due to cracking has become the first factor to affect the durability of underwater tunnel.This article relies on the Zhejiang Natural Science Foundation Project(LY17E08004),starting from the performance of underwater tunnel concrete materials,the seepage characteristics of unsaturated concrete are studied.Through the experiment,the quantitative control of the underwater tunnel under pressure and the width,length and depth of concrete cracks is carried out to establish the underwater tunnel cracking Concrete in the material transport model,the theoretical analysis of the material tansport process in cracking concrete,numerical simulation analysis,verification and study of underwater cracking concrete water seepage basic law.The research work of this paper and the conclusions are as follows:1.Based on the basic theory of concrete seepage,the water movement of cement in intact and cracked concrete under water pressure is analyzed.Considering the factors influencing the water infiltration in the concrete and cracking concrete,the saturation is used as the variable,study on water transport model in unsaturated state.2.Based on the mixing ratio of concrete in Shenjiamen tunnel,combined with the theoretical formula,the design of permeability coefficient test scheme.The experimental results show that the permeability coefficient of intact concrete and cracked concrete is independent of the size of the pressure,only related to its nature,but the permeability coefficient of the cracked concrete is also related to the crack width,crack length,crack depth and other factors,and verify the measured cracking of concrete The permeability coefficient conforms to the law of cube.3.According to the theoretical formula,design a reasonable test program and device.The results show that the depth of penetration of concrete is related to water pressure,saturation and water-cement ratio,but the depth of cracking of concrete is related to the width of cracks,the length of cracks and the depth of cracks.The water pressure is large,The deeper the depth of penetration,the greater the saturation,the better the concrete and the higher the depth of penetration,the deeper the penetration depth,the faster the water and the concrete,the faster the depth of penetration The higher the crack length,the slower the water movement of the cracked concrete and the smaller the penetration depth.In the same condition,the higher the crack width is,the more the crack depth is under the same conditions,the greater the depth of cracks,the faster the concrete movement of cracked concrete,the greater the depth of penetration.4.The paper analyzes the water pressure,the initial saturation of concrete,the width of crack,the length of crack,the depth of crack and other factors on the underwater integrity and cracking of concrete cracks,which is based on the advanced porous media simulation software PetraSim.The impact of moisture transmission The results of the saturation output and the data of the output data are compared with the experimental data,which verifies the accuracy,rationality and authenticity of the model.At the same time,the service life of Shenjiamen subsea tunnel is predicted by the experimental data of Chapter 3,and the service life of underwater tunnel and the service life of crack tunnel are obtained.