Study Of Shrinkage Cracking Characteristic Of Cement Stabilized Macadam With Variety Of Admixtures Based On Extended Finite Element Model

Shrinkage cracking is an important factor affecting damage to the service level and structural capacity of Semi-rigid base.Because of the importance and complexity of shrinkage cracking,it has always been a great concern to researchers.Traditionally,the research of shrinkage performance is to study the crack and development regularity of basic-level cracks by indoor and field tests respectively.They both have certain limitations because of the environment limitation of indoor test and the time-consuming of field test.However,the application of Extended Finite Element Method has brought a great improvement to research in this field.In this paper,the method of fiber Bragg grating used to measure the shrinkage coefficient and temperature shrinkage coefficient of cement stabilized crushed stone to study the effect of additive on shrinkage cracking property in laboratory.Meanwhile,based on the extended finite element method,a cement stabilized macadam base model is established,and the influence of the mixture thickness and the base thickness on the shrinkage crack spacing of cement stabilized macadam base is analyzed.The main research contents of this paper are listed as follows.First of all,a laboratory study is used to research the crack resistance of cement stabilized macadam base materials.Namely lime,desulfurized gypsum and polypropylene fiber are selected to reduce the dry shrinkage property and the temperature shrinkage property of cement stabilized crushed stone materials by looking up reference material.The orthogonal uniform design is used to determine the mixture ratio of the three additives,and the fiber Bragg grating is used to measure the shrinkage coefficient and the temperature shrinkage coefficient.Secondly,the development law of cracks in cement stabilized macadam base is studied through field monitoring,including the time and spacing between cracks,etc.Thirdly,finite element analysis combined with extended finite element method is used to establish shrinkage crack analysis model of cement stabilized macadam base.The density,elastic modulus,Poisson's ratio,dry shrinkage coefficient and temperature shrinkage coefficient of each structure layer are determined.Then compared with the field monitoring results,the reliability of numerical simulation is verified.Finally,Based on the established finite element model,the influence of the dry,temperature shrinkage coefficient and the thickness of the base on the cracking performance of the base is further analyzed.The research results show that adding material can improve the cracking resistance of cement stabilized macadam.In the numerical simulation analysis,it can be seen that the suitable shrinkage coefficient and the temperature shrinkage coefficient can make the crack spacing of the cement stabilized macadam base increase,improve crack resistance of base and delay the time of crack.Also,increasing base can increase the thickness of the base crack spacing.