Abstract
Hollow grouted rock bolts are widely used in deep soft rock roadways. The density of grout has a significant influence on the anchorage quality. However, there is still a lack of effective methods to detect the grouting quality fast, accurately, and extensively. Based on the wave velocity and the law of stress wave transmission and reflection in the impedance mismatch, non-destructive experiment focused on the defect in the anchorage was conducted. The wavelet transform was used to analyze the test signals. The test results show that the free length of hollow grouted rock bolt could be accurately detected through the analysis of the stress wave signal by using the low-pass filter in the wavelet toolbox. The grouted length, defect length, and specific position of the anchorage section can be accurately detected through the analysis of the stress wave signal by using the high-pass filter in the wavelet toolbox. The research can provide experiment foundation for further study of grouting quality based on the non-destructive methods.
Highlights
With massive coal mines entering the stage of deep mining, many new issues come out and the reinforcement of soft surrounding rock mass of roadways is one of those problems
Hollow grouted rock bolts can be employed to improve the mechanical properties of the surrounding rock mass and provide anchorage in soft rock roadways due to their convenience and fast installation
2.1 Theory background 2.1.1 Stress wave propagation in hollow grouted rock bolt Conventional hollow grouted rock bolt has a diameter of 25–32 mm, and the length is ranged from 2 to 10 m
Summary
With massive coal mines entering the stage of deep mining, many new issues come out and the reinforcement of soft surrounding rock mass of roadways is one of those problems. The main issues of reinforcing deep soft rock roadways include high field stress, high temperature, and high water content [1,2,3,4], lead to a loose and broken surrounding rock. Hollow grouted rock bolts can be employed to improve the mechanical properties of the surrounding rock mass and provide anchorage in soft rock roadways due to their convenience and fast installation. Hollow grouted rock bolt has middle hollow tube design. The middle hollow tube of the rock bolt is used as the high-pressure blast channel and grouting channel.
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