Hydraulic Concrete Fracture Analysis And Applied Research Based On The Linear Displacement Distribution Of The Fracture Process Zone

Along with the development of water conservancy projects,step up to the requirement of concrete performance of hydraulic structure,the concrete crack problems has become the focus of attention in the industry,the studies on the fracture process is more important with the needs of engineering practice.This paper mainly analysis the displacement and strain of specimen in three point bending experiment by using digital image correlation method which is a better advanced technology.And based on the theory of fracture mechanics and some classical fracture model,the linear distribution of the fracture process zone is analyzed with MATLAB software programming by simplifying the softening curve model,several main work of this paper are as follows:(1)Through the observational data of the change of the displacement and strain in three point bending experiments with digital image correlation method,comparing the measurement of extensometer,verify the accuracy of the digital image correlation method.From the perspective of the whole strain,it found that the full strain will appear the phenomenon of strain concentration with the increase of load,and it mainly occurs in the area around the crack development process.In addition,through the analysis of the displacement of different heights parallel lines of crack tip tangent,the mutation region can also judge the fracture cracks zone and where the fissure moves toward.(2)To study the fracture process of hydraulic structures,it takes three point bending experiment on saturated and unsaturated concrete specimens.Comparing with the performance of both law,it founds that both show the same change trend,that is,the process of fracture development should have the same rule,so some of the findings of the unsaturated in the fracture process of concrete can be apply to saturated concrete.(3)For the study of the development of the fracture process zone,the relationship between the fracture process zone and the concrete specimen is analyzed.It is found that the fracture process area starts to occur after the load reaches a certain value.Along with the whole loading process,by the influence of the boundary conditions,the late arrival of a certain critical value,the length of the fracture process area will decline.(4)According to the correlation analysis of the strain around the crack tip,it founds that the change rule of strain in different areas around the crack tip is hardly relative to the length of the analysis line segment,but it will affect the magnitude of the peak.And the distance between the center of the analysis line segment and crack will affect the changing law of strain.(5)Based on previous fracture theory model,assuming that opening displacement actives linear distribution,a new softening curve model is established,so as to get a more simple and quick way to gain softening curve parameters.According to the softening curve model of this article,fitting it with the different strength,moisture content,aggregate,sand ratio,aggregate maximum particle size and different content of coarse aggregate related,it can get the corresponding influence relations.