Microseismic Signal Characterization and Numerical Simulation of Concrete Beam Subjected to Three-Point Bending Fracture

Nuwen Xu,Feng Dai,Yingcheng Lei,Biao Li,Chun Sha

doi:10.1155/2015/987232

Abstract

To study the generation mechanism and failure mode of cracks in mass concrete, microseismic monitoring is conducted on the fracture processes of the three-point bending roller compacted concrete (RCC) beam of Guanyinyan hydropower station. The spectrum characteristics of microseismic signals in different deformation and failure stages of the concrete beam are analyzed, and the identification method of the fracture stages and crack propagation precursors of concrete beam is established. Meanwhile, the Realistic Failure Process Analysis code (RFPA) is adopted to simulate and analyze the entire failure processes of concrete beam from its cracks initiation, development, propagation, and coalescence, until macroscopic fractures formation subjected to three-point bending test. The relation curve of the load, loaded displacement, and acoustic emission (AE) of concrete beam in the three-point bending test is also obtained. It is found that the failure characteristics of concrete beam obtained from numerical experiments agree well with the field physical test results. The heterogeneity of concrete is the major cause of zigzag propagation paths of beam cracks subjected to three-point bending tests. The results lay foundation for further exploring the formation mechanism of dam concrete cracks of Guanyinyan hydropower station.

Highlights

In recent years, hosts of ultra-large hydropower projects are being constructed or to be completed and put into operation in the southwest of China
In RFPD3D numerical simulation, the element failure is accompanied by acoustic emission (AE), and the number of AEs is that of failed elements
It can be seen that numerical simulation used by RFPA3D reproduces the entire processes of the concrete beam from its microfractures initiation, development, propagation, and coalescence, until macroscopic fracture band formation in the three-point bending tests

Summary

Introduction

Hosts of ultra-large hydropower projects are being constructed or to be completed and put into operation in the southwest of China. One is to analyze hypocenter parameters of the microfracture, including the size, intensity, energy, magnitude, apparent stress, and stress drop, qualitatively deducing the development trend of the crack and macroscopic fracture, and forecast the evolution rules of dam body concrete local failure or cracks. This kind of method has been successfully applied to engineering fields including the mine and hydropower projects [10, 19, 20]. This study attempts to analyze the spectrum characteristics of microseismic signals during the fracture processes of the concrete beam subjected to three-point bending test. The entire fracture processes of concrete beam subjected to three-point bending tests using 3D numerical simulation are reproduced, which lays foundation for studying the formation mechanism and evolution rules of cracks in mass concrete

The Time-Frequency Analysis Principle of S Transform

Comparative Analysis of Field Test and Numerical Simulation Results

Conclusions