Abstract: The bond strength between shotcrete and surrounding rock is a most crucial performance indicator of shotcrete, and also an important content of inspection in the construction of underground caverns. With Fengning Pumped Storage Power Station's underground powerhouse as a background project, field experimental study on the bonding characteristics of shotcrete and surrounding rocks in underground caverns was carried out by using drilling core sampling and reprocessing. The causes of the frequent breakage of core samples during drilling were analyzed. The single step of directly preparing samples from the drill core was adjusted into two steps: on-site sampling and indoor processing; subsequently the samples were repaired to meet test requirements. Test results show that the bond strength between shotcrete and surrounding rock in the main transformer room of Fengning Pumped Storage Power Station is slightly higher than that of the main building. The results demonstrated that the drilled core specimens undergone indoor processing and restoration can be used for the test of bonding strength between shotcrete and surrounding rock. The test results are reliable and reflect the actual bonding strength between shotcrete and surrounding rock.

Key words: underground cavern, shotcrete, bond strength, field test, sampling by core drilling