Experimental And Numerical Investigation Into Mode ? Fracture Behavior Of Rock-SCC Interface In Rock-fill Concrete

As an environment-friendly damming material,rock-fill concrete(RFC)has been widely used in recent years.However,due to the fact that the particle size of rocks in RFC is much larger than that of the fourth-grade aggregate,which can reach 500-1000 mm or more,it is impossible to experiment on its real-scale mechanical properties through largescale tests.This is the key technical bottleneck restricting the application of RFC in high dams and high-level structures at present.From the viewpoint of meso-mechanics,RFC can be regarded as a composite model composed of rock-interface-SCC three phases.By obtaining the mechanical parameters of each phase,a numerical model of rock-fill concrete can be constructed,which can provide an effective numerical tool for predicting the mechanical properties of RFC and studying its damage mechanism.In this study,experiments and numerical analysis are carried out on the interface mechanical behavior which is seldom studied at present.The main research contents are as follows:1.Wedge splitting tensile test of rock-interface-SCC three-phase composite specimen was carried out to study the influence of SCC grade,rock surface roughness and stone powder defects on the interface mode I fracture performance.According to the three-dimensional scanning results of rock surface,the roughness is distinguished and characterized,and the correlation and discrimination between different roughness characterization indexes and test results are analyzed.2.The J-integral method is improved to make it suitable for wedge splitting tensile test,and the characterization functions of tensile strength and tensile softening constitutive relation at the rock-SCC interface are derived.The influence of various test factors on the interfacial tensile behavior is analyzed.Parameterized characterization of bilinear model and exponential model for typical softening curve lays a foundation for numerical calculation and subsequent research.3.Build the finite element numerical model of the three-phase composite specimen of rock-interface-SCC,the cohesive elements are used to simulate the interface,and conduct numerical simulation research based on the derived softening curve parameters;The influence of factors such as softening curve type,SCC grade and surface roughness of the rock on the fracture performance of the rock-SCC interface is simulated,and the fracture mode of the meso-level interface unit in wedge splitting tensile test is discussed.4.The C15 series equivalent mode I softening constitutive model is applied to the numerical simulation of the three-point bending beam test of rockfill concrete.According to the characteristics of the fracture surface in the test,bending beam samples with different rock layout are constructed,and the influence of the presence or absence of interface elements and the bonding performance of interface elements on the crack propagation mode and macro load-displacement response of the bending beam is analyzed.