Experimental Study on Ultra-low Friction Effect of Granite Block Under Coupled Static and Dynamic Loads
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ORIGINAL PAPER
Experimental Study on Ultra-low Friction Effect of Granite Block Under Coupled Static and Dynamic Loads Dongqiao Liu . Youwen Lin . Yang Wang . Manchao He . Shudong Zhang
Received: 13 January 2020 / Accepted: 9 April 2020 Ó Springer Nature Switzerland AG 2020
Abstract Zonal disintegration widely exists in the excavation roadways and caverns in deep rock masses. Ultra-low friction can be generated in the deep fractured rock masses, which reduces or disappears under dynamic loading. In this paper, granite blocks were processed into cube specimens with a cylindrical hole in center. Static loads and sinusoidal disturbances were applied to study the sliding phenomenon between blocks. During the experiments, real-time images, and acoustic emissions were recorded. Results indicate blocks above the cylindrical hole slide during the second half of the sinusoidal disturbance, and block sliding is caused by a reduction of friction between the blocks. The existence of ultra-low friction can be inferred from this experiment. Keywords Fractured rock mass Sin-wave disturbance Ultra-low friction Image acquisition AE
D. Liu Y. Lin Y. Wang (&) M. He S. Zhang State Key Laboratory for Geomechanics and Deep Underground Engineering, Beijing 100083, China e-mail: [email protected] Y. Lin Y. Wang S. Zhang School of Mechanics and Civil Engineering, China University of Mining and Technology, Beijing 100083, China
1 Introduction With the increasing energy demand, China has entered deep resource exploitation. When excavating roadways and caverns in deep rock masses, zonal fracturing, including a large number of cracks, is common (Qian 2004a; Li et al. 2020; Wu et al. 2020). Deep rock masses are commonly located in complex mechanical environments (He 2004; He et al. 2005; Qin et al. 2019; Wang et al. 2019). Disturbance forces may cause an unrecognized phenomenon to emerge between these cracks, namely ultra-low friction (Qian 2004b). Russian scholars Kurlenya and Oparin (1999, 2000) introduced the concept of ultra-low friction when they studied the pendulum wave mechanism. When a dynamic impulse acts on rock mass, the relative compaction degree between rock blocks varies with time. When the rock mass is relatively loose, the friction between rock masses is significantly reduced, the existence of ultra-low friction has been verified using block model experiments (Kurlenya et al. 1992, 1997, 1998, 1999; Kurlenya and Oparin 1999, 2000; Oparin et al. 2001). At present, research on ultra-low friction is still in its infancy; however, ultra-low friction in rock masses is a key scientific problem in deep mining (Qian 2004c). Wang et al. (2005) explained the theoretical aspects of ultra-low friction by studying rock mass block dynamic models. Wang et al. (2007) obtained the same experimental conclusion as Russian scholars through theoretical analysis and numerical simulation
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of rock mass block dynamic models, which illustrated the authent
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