Technology On The Detection Of Advance Stress Peak Position In The Roadway Driving Face

As China’s coal mines gradually enter the deep mining times, the stress distribution of coal and rock mass in underground space is more and more complex, and the phenomenon of coal and rock dynamic disasters caused by mining operation is becoming more and more serious. Due to the dynamic change of stress in the process of mining operations, it is difficult to continuouslydetect the ground stress.Stress cannot be regarded as the outburst prediction index for a long time, resulting in the defects of conventional prediction technique.In this paper, a method of elastic wave is proposed to detect the leading stress peak position of roadway. Based on the comprehensive analysis of the domestic and foreign elastic wave velocity prediction of coal and rock dynamic disaster engineering practice and technical achievements, this paper mainly studies the generation and propagation mechanism of elastic wave in coal and rock mass, laboratory experiment on the relationship between stress and wave velocity under uniaxial loading and elastic wavefield test. The following results are obtained:(1)Through the study, the generation of elastic wave in coal and rock mass is closely related to the formation, expansion and fracture of coal and rock body.(2)The experimental results show that the variation trends of longitudinal wave velocity and stress are consistent in the same direction. Therefore, the influence of stress-strain and crack on the wave velocity is consistent, and the longitudinal wave velocity is directly affected by the number of fissures and the development of expansion, which is reflected in the change of stress- strain and velocity.(3)A mathematical model for the distribution characteristic of the borehole velocity in the tunneling face is constructed. Characteristic of velocity distribution reflects the stress distribution of the tunneling face. In the field test, the wave velocity is the largest in advance 5-7.5m, which shows that the stress concentration area can be determined before 5-7.5m in the face of tunneling work. After comparing the test results with the traditional methods, the two methods have a high degree of consistency, which indicates that the peak position detection of the driving working face with elastic wave velocity is feasible and accurate.(4)A criterion of footage driving cycle, 1/2 guideline, which suggests that the length of a footage should be less than half of the distance to the position of stress concentration, or a stress relief zone of which the length is more than 3 m should be retained, is proposed.It is very important to effectively detect the peak position of the leading stress in the mining face. In this paper, a method of elastic wave is proposed to detect the leading stress peak position of roadway in order to provide support for the prevention of coal and rock dynamic disaster.