Calculation Method Of Deformation Gutter In Large Length Underground Structures And The Feasibility Of Applying Engineered Cementitious Composite

To meet the demand of building function and waterproofing,no-expansion joints design of large length underground structures is becoming more and more popular.The deformation gutter is a component which is commonly used in the no-expansion joints large length underground structures.By reducing the horizontal constraint of the basement floor,the deformation gutter can release the basement floor's deformation under the temperature and shrinkage,so as to achieve the purpose of reducing the tensile stress in the floor.As the basement floor at both ends of the deformation gutter will have a big shrinkage and temperature deformation,there will be a big deformation and tensile stress in the deformation gutter.It is frequently to found cracks and leakage in the deformation gutter.In order to study this phenomenon,the main study of this paper is as follow:(1)The conventional calculation method of the deformation gutter does not consider the influence of the construction process,and the shrinkage and creep of the concrete is converted into temperature changes.In order to get the accurate calculation results of the deformation gutter,the simulation of construction process is necessary.In this paper,two calculation methods are compared.(2)The material of the deformation gutter needs high tensile ability and toughness.This paper analyzed the feasibility of applying Engineered Cementitious Composite(ECC),and calculated the accurate tensile demand of this material.(3)The maximum tensile strain and bending failure modes of ECC with different PVA fibers were obtained by the four-point bending test.The possibility of replacing the conventional imported PVA fiber with domestic PVA fiber in ECC was discussed.Through the finite element analysis and laboratory tests,the main conclusions are as follows:(1)In the conventional calculation method,the shrinkage and creep of the concrete is converted into temperature changes.Both the conversion temperature and the reduction factor are empirical parameter.It is difficult to determine the accurate parameter.At the same time,the internal force of the quasi-permanent combination value is smaller than the actual situation,it is negative for the cracks calculation.(2)After considering the stress concentration effect,the width of the crack in the ordinary concrete deformation gutter is over limit.And the ultimate tensile strain of ECC can reach more than 3%.ECC's crack dispersion ability under the tensile load,impermeability,durability,cost and other factors meet the application requirements of the deformation gutter.Taking into account the results of finite element analysis,construction conditions and other factors,the maximum tensile strain demand of ECC in the deformation gutter is 1%.(3)Through the four-point bending test,the traditional ECC show superior tensile strength and toughness.The ultimate tensile strain of ECC with a kind of domestic PVA fiber can reach 1% and show the same toughness and crack dispersion ability,meets the maximum tensile strain demand of concrete in the deformation gutter.