THE DYNAMIC CAUSTICS TEST ON THE GROWTH LAW OF FRACTURES IN TUNNEL SURROUNDING UNDER EXPLOSIVE LOAD
Liu Kang, Guo Dongming, Zhang Jun, Kang Xinchao
China University of Mining & Technology, Beijing, China
Keywords: Explosive load, adjacent tunnel, original fracture, growth law, dynamic caustics
Abstract
The damage to the surrounding rock under the adjacent explosive load generally manifests as fracture growth. In order to in-depth understand the fracture growth law and mechanism, fracture growth process in the surrounding rock with a nearby adjacent tunnel under the explosive load is studied using the dynamic caustics method. Test results indicate that the original fracture growth process can be divided into two stages, demarcated when the main fracture penetrates the original fracture. The original fracture grows in the vertical direction due to the free surface of the tunnel in the first stage. The main fracture from the explosive source plays a dominant role in the growth direction of the original fracture in the second stage, and the original fracture deflects and grows parallel to the main fracture. Based on kinematic and energy analysis, the penetration process is companied by energy transfer and superposition. The neglected back-facing side also contains fracture on the lower side. The fracture growth direction changes after the original fracture penetrates the free surface of tunnel under the combined effect of the original fracture and unloading wave.
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