Experimental Study On Fracture Of Axial Tension Of RCC Layer Surface

In recent years, the RCC dams have been developed greatly not only in height but also in quantity with the construction of the RCC dam. Obviously, there are two questions of bedding plane and stabilization of dam in consideration of the structural characteristics of the layer-lifted construction of RCC dams. Therefore, it is necessary that the fracture mechanism of RCC dam along layer surface is studied. In this paper the fracture characteristics of axial tension of RCC layer surface are studied experimentally by servo hydraulic closed-loop testing machine in laboratory. The experimental data are analyzed by the theory of fracture mechanics (double-K fracture model). The following work is carried on in this paper.1 The properties of RCC layer surface (4 hours interval and no treating) are acquired bythe analysis on experimental datas. Properties concluded are tensile strength, modulus of elasticity, and the effect of layer surface on tensile strength.2 A practical analytical method is proposed for determining the precritical crack propagation length △a. The iterative compute process is avoided by the simplified method. The simplified methods have successfully simplified the compute process of double-K fracture parameters, with very high precision.3 Properties of fracture of axial tensile specimen is analyzed by theory of fracture mechanics (double-K fracture model) ,and the double-K fracture parameters is determined. Moreover size effect of fracture parameters and the effect of layer surface upon double-K fracture parameters are studied.4 Using the standard three-point bending beam specimens and wedge splitting specimens (method of construction is same with axial tensile specimens), the complete P - CMOD curves for RCC specimens is achieved, and fracture energy is computed. The relation between fracture energy of layer surface and fracture energy of RCC is analyzed.5 The ultimate tensile strain of pairing joint in RCC layers is computed by the theory of double-K (initiation toughness" Kini lc' "corresponding initiation load" Pini ", initiation load"Pini "corresponding the ultimate tensile strain "ε "in load-strain of crack tip curves).The ultimate tensile strain "ε " is achieved by the computation of double-K fracture parameters, and the result is compared with international empirical formula. The correlation between the ultimate tensile strain of pairing joint in RCC layers and the ultimate tensile strain of RCC have been obtained.6 Under the same condition the relation between fracture toughness of layer surface of RCC and fracture toughness of RCC is studied. The fracture toughness of RCC layer surface (two notches in specimen) is computed by linear elasticity, and the fracture toughness without size effect is achieved by the formula that is proposed by Professor Shilang Xu.7 The relation of equivalent strength and weakened variant is studied, and the fitting formula is also suggested. The condition of cracking is analyzed in RCC layer surface.In this paper the reliable reference data is provided for analyzing the designs, construction and safety of the roller compacted concrete dam.