Abstract: The shear bands C2 and C4 aggravate the risk of deformation and failure of the surrounding rock of Baihetan main powerhouses. As a result, corresponding control measures must be developed. According to field failure phenomena and monitoring data, the response characteristics and failure mechanism of surrounding rock under the conditions of C2 exposing at the sidewall of the left plant and C4 exposing at the roof arch of the right plant are investigated using theoretical analysis and numerical feedback methods. Some control measures for the adverse impact of the shear band are proposed, and corresponding evaluations of the effectiveness of measures taken are conducted. The research results show the following: (1) The combination measures of main shear resistance tunnel and branch tunnel combined with cross lock can effectively control the aggravating effect of shear deformation along with C2 on the relaxation deformation of the sidewall of the main powerhouse at the left bank. (2) The superposition of abnormal stress locally induced by C4 during tectonic movement and excavation secondary stress increases the risk of stressinduced damage to the roof arch layer of the right bank′s main powerhouse. (3) Surface support and deep reinforcement measures combined can provide "maintenance" and "reinforcement" to the shallow and deep surrounding rock affected by C4. The results show that shear band system support and control measures can ensure the overall stability of the main powerhouse.

Key words: Baihetan hydropower station, underground powerhouse, shear band, surrounding rock stability, support design