Research On Basalt Fiber Concrete Cracking Based On Extended Finite Element And Smeared Crack Method

Concrete is a leading building material,widely used in construction,hydraulic,transportation and other fields,as a brittle material,easy to produce cracks.In practical engineering applications,the cracks of various concrete structures will gradually expand under the influence of their own and external effects,resulting in the final failure of the structure.In particular,the concrete hydraulic structure is easy to form a crack-seepage-freezing mutual feed failure mechanism in seasonal freezing area due to its crack susceptibility and water sensitivity,which reduces the service life of the structure.In order to solve this problem,considering that the concrete structure mixed with basalt fiber has superior cracking resistance,this paper,based on the mechanical property test of concrete materials,observed the microstructure of basalt fiber concrete by scanning electron microscopy test,and revealed the internal relationship between its macro property and microstructure.The cracking analysis of the basalt fiber concrete structure is carried out by the extended finite element method and the smeared crack method,and the crack propagation characteristics and rules of the concrete structure under different methods are studied.The beam model(standard structure)and U-shaped channel model(irregular structure)are verified by the fracture performance test of the basalt fiber concrete beam and the fracture observation test results of the U-shaped channel lining.Through numerical simulation,the influence of basalt fiber content and freezethaw cycles on failure characteristics and frost heaving resistance of U-shaped lined channels was further explored.The main conclusions are as follows:(1)The addition of basalt fiber can improve the compressive strength of concrete.With the increase of freeze-thaw cycles,the compressive strength of concrete still increases with the increase of basalt fiber content,but gradually tends to be consistent.The basalt fiber content of 0.300%can increase the tensile strength of concrete by 16.19%.With the increase of freeze-thaw cycles,the freeze-resistance of basalt fiber concrete with volume content of 0.325%is better.(2)The fracture trajectory of the smeared crack method presents as banded damage units,which is more significant for the prediction of the whole fracture,but has certain limitations for determining the specific location and propagation direction of the fracture compared with the extended finite element.With the advantage of rapid calculation,the location of fracture zone can be determined according to various structures,which can provide reference for the fracture layout of extended finite element.Through the combination of the two methods,the crack location of the model is determined by the dispersion crack and the fracture propagation calculation by the extended finite element can provide better prediction results.(3)Through the numerical simulation of U-shaped lining channels under different test conditions,it is concluded that the U-shaped channel with 0.300%basalt fiber content has the highest crack resistance and frost heave resistance.Cracks are more likely to occur in U-shaped channels under the action of freeze-thaw cycle.(4)The extended finite element method and the smeared crack method have different calculation methods and results in terms of describing crack propagation,principal stress,displacement and deformation,etc.Through reasonable combined application,the failure deformation and failure mechanism of different materials under different working conditions can be more accurately and effectively reflected.