The Experimental Study And Numerical Simulation On Strength And Fracture Of Induced Crack In Roller Compacted Concrete

As we all know, temperature cracks do some great harm to RCC (Roller Compacted Concrete) dams. In order to avoid the non-order temperature cracks in RCC dams, induced cracks are adopted in most of RCC dams home and abroad. The right understanding of the equivalent strength and fracture property of induced crack, and the optimal design of its size and location in section of arch dam are the precondition of analysis of stress filed of RCC arch dam. However, the experimental and academic studies on its fracture mechanism are so little that it can't meet the great need of practical applies. The researches on the shape of induced crack, its location, the size of embedded cracks, as well as the center-to-center distance of two adjacent cracks etc., haven't come to the same conclusion until now. Aim to the facts that the equivalent strength is high in induced crack section of arch dam, the design level of induced crack needs improving further for equivalent strength can be decreased properly. It is urgent to solve these problems to satisfy the necessity of practical engineering. With the support of National Natural Science Foundation of China-Study on equivalent strength of induced crack in RCC arch dam (50179002), this paper focuses on experimental study, fracture analysis and finite element simulation of induced crack, as well as calculation model of its equivalent strength. The detailed researches are performed as following:1 The experimental study of induced crack in RCCThe influences of different shapes, different weakened degrees, and different sizes of induced crack on its equivalent strength are analyzed on the base of experimental study ofcuboid specimens. The main work and conclusions are summarized as follows:1) Experimental data about the equivalent strength and fracture toughness of induced crack are obtained from direct tensile experiments of cuboid specimens. The strain developing laws around induced crack with different weakened degrees are studied. Furthermore, the equivalent strength altering laws with different shapes and weakened degrees are analyzed, too. The calculational expressions about equivalent strength are gained. The analysis of the influence of stress concentration on equivalent strength indicates that the equivalent strength is a concave line when a ranging from 0 to 1. So there is a optimal weakened degrees which makes the maximal difference between equivalent strength and (1 - a)ft.2) The equivalent strength values of one, two and four penetrating induced cracks in RCC specimens are discussed. The experimental evidences reveal that the setting of two induced cracks is more helpful to reduce the equivalent strength than one, which has the same weakened degrees as the former. At the same time, the interval distance between two edges of induced cracks has a great influence on the value of equivalent strength. The calculational expressions about equivalent strength with different interval distance are gained. The resultsof the experiment indicate that reasonable setting of induced cracks in arch dam is more effective to decrease the equivalent strength than only increase the weakened degrees.3) Notched induced cracks are placed in RCC-cuboids specimens to study the influence of notch on arch dam's upstream and downstream faces on the split of induced cracks. Experimental data about the equivalent strength of the notched induced cracks are obtained from direct tensile experiments of cuboid specimens. The experimental results about equivalent strength of notched induced crack indicate that the notches on upstream and downstream faces have some effects on cracking direction of induced cracks.4) The equivalent strength values of non-penetrating induced cracks in RCC specimens are discussed. The elliptic simplified calculation errors of rectangular induced cracks are validated. Then the simplified modificatory coefficients are given.2 The fracture analysis of induced crackFirst of all, the cohesive force distribution on the fictitious crack of induced crack tip is ascertained on the base of softenin...