The influence of rock mechanical properties on the electromagnetic radiation(EMR)mechanism of rock fracturing is an important research topic in solid mechanics and earthquake prediction.In this study,an EMR model of rock fracturing considering the fracture factor,elastic modulus,Poisson’s ratio,radiation distance and crack length is derived based on the Hertz oscillator array assumption.An experimental system,including an electromagnetic shielding module,an EMR signal induction and transmission module,a signal recording module and a loading module,is developed to understand the EMR characteristics of four different rocks.The validity of the EMR theoretical model is verified and the relationships between the rock cracking morphology and the EMR waveform,amplitude and frequency are revealed.It is found that rock mechanical properties have obvious influences on the EMR waveform,amplitude and frequency during rock fracturing.This study provides a better understanding on the EMR mechanism of rock fracturing and can help to improve the accuracy of rock disaster prediction based on EMR.
Peng LinPengcheng WeiCheng WangShengzu KangXin Wang
Underground construction in China is featured by large scale, high speed, long construction period,complex operation and frustrating situations regarding project safety. Various accidents have been reported from time to time, resulting in serious social impact and huge economic loss. This paper presents the main progress in the safety risk management of underground engineering in China over the last decade, i.e.(1) establishment of laws and regulations for safety risk management of underground engineering,(2) implementation of the safety risk management plan,(3) establishment of decision support system for risk management and early-warning based on information technology, and(4) strengthening the study on safety risk management, prediction and prevention. Based on the analysis of the typical accidents in China in the last decade, the new challenges in the safety risk management for underground engineering are identified as follows:(1) control of unsafe human behaviors;(2) technological innovation in safety risk management; and(3) design of safety risk management regulations. Finally, the strategies for safety risk management of underground engineering in China are proposed in six aspects, i.e. the safety risk management system and policy, law, administration, economy, education and technology.
