Size Effect of Concrete Specimens on the Acoustic Emission Characteristics under Uniaxial Compression Conditions

Jianbo Wu,Mingwei Zhang,Xuekun Ren,Enyuan Wang

doi:10.1155/2017/7652313

Abstract

Acoustic emission (AE) experiments under uniaxial compression and cyclic loading-unloading compression conditions were performed using different sizes of cubic concrete specimens. The influences of the loading methods and the concrete sizes on the mechanical parameters and the concrete AE activities were analyzed. The loading method was found to have great impact on the deformation, failure, and energy dissipation of concrete materials. With the increase of the material size, the uniaxial compressive strength of the concrete specimens gradually decreased, while the corresponding strain of peak strength increased first and then decreased. The elasticity modulus fluctuated irregularly. Under the uniaxial compression conditions, five AE patterns corresponding to the deformation and failure of the concrete materials were observed. A significant nonlinear relationship was found between the AE and the stress level. The cumulative AE rings at the peak stress showed nonlinear growth with the increase of the concrete size. Based on an established relationship between the cumulative AE rings and the stress level, the necessary conditions for the existence of the quiet AE period were given. Under the uniaxial cyclic loading-unloading compression conditions, the Felicity ratio decreased first and then increased as the stress increased. The research results have some guiding significance to AE-based monitoring of internal stress evolution of coal, rock, and concrete materials and thereby enable assessment of their stability.

Highlights

During the deformation and failure evolution of coal and rock materials, internal strain energy will be transmitted and dissipated continuously
Acoustic emission (AE) event monitoring has become an important means for real-time monitoring of the failure evolution of materials [1]
Many research studies on the AE characteristics of coal, rock, and concrete materials during the deformation and failure process have been reported since the Kaiser effect was discovered [8]

Summary

Introduction

During the deformation and failure evolution of coal and rock materials, internal strain energy will be transmitted and dissipated continuously. Many research studies on the AE characteristics of coal, rock, and concrete materials during the deformation and failure process have been reported since the Kaiser effect was discovered [8]. Scholars have performed many studies on electromagnetic radiation, AE, surface potential change law, and other phenomena in the rupture failure process of coal and rock masses; these studies have achieved tremendous research results that have been applied in engineering practice for the monitoring and forecasting of dynamic disasters. As an artificial prefabricated rock material, concrete can reduce the physical differences of sample individuals to the maximum extent On this basis, AE responding laws of cubic concrete specimens with different sizes in the uniaxial loading failure process and the influences of size on the basic mechanical parameters were explored

Experimental Design and Scheme

Results and Discussion on the AE Activities of Concrete Specimens

Conclusions

Conflicts of Interest