Study On Impermeability And Drying Shrinkage Performance Of Tunnel Secondary Lining Concrete

Our country has the largest number of tunnels and underground works,the largest structure and the most complex geological conditions,the construction technology of the fastest growing countries.However,there are many problem s in the operation of the tunnel.The tunnel seepage water is the most serious harm to the project.Secondary lining waterproof concrete is the key to its prevention,it is not only to provide a safety margin for the structure,but also to meet a certain intensity in the premise,to maximize its impermeability.Impermeability of concrete lining of the lower main reasons: concrete is not enough,concrete penetration of water channels,mainly cement and cement itself at the contact interface with the gravel o f various shapes and capillary gap caused.Or poor quality of construction of various shapes caused by the gap holes.Tunnel secondary lining concrete design strength grade is generally C25~C35,impermeability grade is great,its main technical characteris tics are low intensity and high impermeability,but there is mutual contradiction between these conflicting technical indicators.In preparation low strength concrete,generally using large water-cement ratio,In the preparation of the impermeability of concrete,generally using low water-cement ratio,increasing the amount of cement,concrete strength so easily lead to excessive,not economic,but also the flow state is not good.So how to balance the relationship between the three indicators is the biggest difficulty for the preparation of the tunnel secondary lining concrete.In this paper,by incorporating mineral admixtures and basalt fiber in concrete,study the effects of the incorporation of its content and the way the secondary lining concrete cracking impermeability properties.According mineral admixture on concrete performance improvement role and fiber reinforced concrete characteristics of the tunnel secondary lining concrete is formulated to provide data support for actual projects.Through ext ensive testing research that,fly ash and slag can significantly increase the impermeability of concrete,total added content is 30%,Permeability effect is best by 1:2 mixed fly ash with slag.Incorporation of fibers in concrete can not only improve their strength,and impermeability to further improve,when basalt fiber volume content was 0.10%,the electric flux of concrete specimens is minimum,impermeability is the best and strength can meet the requirements.With the improvement of basalt fiber volume content,the shrinkage deformation of concrete is decrease and then increase.When basalt fiber volume content is 0.10%,it has the smallest shrinkage deformation.