Research On Cracking Of Concrete Slabs Based On Extended Finite Element Method

Concrete faced rockfill dam has the advantages of adaptability to different ground conditions,rapid construction,safety of dam-type structure and low cost,and is widely used by the dam industry.When cracks occur in the concrete panel that is the main impervious body of the dam,the cracks expand under the effect of water pressure and uneven settlement of the rockfill body until it penetrates.The reservoir water penetrates through the concrete faceplate and continuously penetrates into the rockfill,resulting in a pile Stones were taken away by the currents and they were taken out of the air,which in turn threatened the overall safety of the dam.Therefore,the analysis of the stress characteristics of cracked concrete slabs helps to understand the causes of the panel damages from the mechanism and has great significance in preventing and controlling cracks in concrete slabs.In the past decade,more and more scholars have begun to study the failure mechanism of concrete face slab rockfill dam.However,due to many factors that affect the cracking of concrete face slabs,the cracking mechanism is complex and the cracks are too many to trace its path Most of the research was conducted in conjunction with experiments.This paper selects Gongboxia Water Control Project as the research object,establishes a three-dimensional finite element analysis model of concrete faced rockfill dam,and simulates the construction sequence and storage conditions of the construction of the concrete faced rockfill dam to analyze the stress and strain of the dam during the completion period and impoundment period.The equivalent displacement load on the panel subjected to the storage period is applied to the panel.The XFEM is used to simulate the entire process of the maximum deformation of the concrete panel from stress concentration to crack initiation and crack propagation.Secondly,the concrete slab is used as the research object.Based on the theory of linear elastic fracture mechanics,the influence of different calculation methods,crack depth and mesh density on the KI value of the panel cracks was analyzed,a reasonable grid density and calculation method were determined.The comparison between the numerical solution and the numerical solution confirms its accuracy and provides a reference for the study of concrete panel cracking.Considering the actual situation,the stress distribution changes of the front and rear panels of the steel panel are compared after the single-layer bidirectional steel reinforcement is arranged on the concrete panel.Finally,considering the effect of water pressure,XFEM was used to simulate cracking and mutual interference process of cracks on two-dimensional concrete slabs under different angles.The stress changes of cracks under water pressure and the redistribution of stress caused by cracks cracking were analyzed.The fracture widths and pore pressures of the elements where the initial points of a and b cracks are plotted along with the curve of the analysis time history,and the data are explained in detail.The cohesive element was used to simulate the intersection of cracks and horizontal cracks in the thickness direction of concrete slabs.Extract the fracture line graphs of the two types of fractures at different time intervals,combine the equivalent stress cloud diagrams of the cracking process,find the relationship between the joint width,stress value and pore pressure value.It provides a reference for the simulation of the interaction between cracks in concrete panels under water pressure.Based on the ABAQUS platform and the XFEM simulation of the cracking process of concrete slab cracks,this paper realizes simultaneous cracking of multiple cracks under equivalent load of concrete slabs,discusses the variation law of stress intensity factor at the crack tip,and simulates the cracks under water pressure.The expansion process provides new ideas and references for the follow-up study of concrete panel cracking.