Fracture Performance Of Xiluodu Dam Concrete

As full-graded concrete,dam concrete exhibits obvious difference in fracture performance from normal concrete and is susceptible to many factors including aggregate shape,aggregate size,water-to-binder ratio,which makes the fracture parameters obtained from one kind of dam concrete non-generic.The Xiluodu dam is a large-scale long-term complex project,which takes several years from start-up to completion.Therefore,the study on the fracture performance of the Xiluodu dam concrete under the long-term construction can better reflect the real fracture performance of the Xiluodu dam.Based on it,this paper carried out the following three aspects of work and reached the following conclusions:(1)Fracture tests were carried out on wedge splitting test specimens for concrete of Xiluodu Dam cast in situ with 5 years age,the maximum aggregate particle size are all 150 mm,and the initial seam height ratio are all 0.4.The test specimen size is divided into two types: 1500 mm × 1500 mm × 450 mm and 2250 mm × 2250 mm × 450 mm.The test was carried out with a vertical displacement loading rate of 0.2 mm/min.Initiation toughness,unstable toughness,fracture energy and P-CMOD curve were obtained,which expanded the fracture performance data of the Xiluodu dam concrete.Besides,the material parameters were measured by cutting a cube test piece with a side length of 450 mm from the wedge splitting test specimens.In addition,the test found that the initiation toughness obtained by the fracture test of wedge-splitting specimens with dimensions of 1.5 m and 2.25 m showed a certain size effect in the long-term,while the unstable toughness tends to be stable,which can be regarded as a material constant.(2)The digital imaging correlation(DIC)method was used to monitor the fracture test of the two 1.5m high wedge splitting test specimens.By analyzing the displacement field in the calculation area,crack propagation path and the crack width in crack area under different load levels were both obtained,which determine the applicability of DIC in observing the fracture process of full-scale large-volume dam concrete.Meanwhile,some scattered internal micro-cracks,aggregate bypass and crack bifurcation were observed during the monitoring process.Different from ordinary small aggregate concrete,the full-graded dam concrete does not show obvious linear relationship between crack width and expansion depth in the early stage of crack propagation,but after the peak load,with the crack fully expanded,the width and the depth of expansion gradually become linear.This phenomenon may be related to the larger particle size of the aggregate;in addition,there might be some relationship between the crack widths of multiple cracks at the same depth.(3)The ANSYS finite element program is used to calculate the whole process of crack propagation in the wedge splitting test based on a type I fracture propagation criterion.The numerical calculation agrees well with the experimental results,which verified the applicability of the criterion to the fracture propagation of the full-scale dam concrete.