Influence of different excavation modes on mechanical properties of surrounding rock in underground powerhouse caverns group

The aim of thesis is to obtain the unloading mechanical properties of surrounding rock in the large underground powerhouse caverns group excavated by different ways.With the case of the caverns of a hydropower station on Jinsha River,the influence of unloading mechanical properties of surrounding rock to caverns by different excavation ways is researched based on the theory of unloading rock mass mechanics and the 3D finite difference method.The results show that the unloading extent of surrounding rock by different excavations is relatively little;the unloading extent of surrounding rock in the main powerhouse and on the top of tailwater room is far less than that of the side wall after the excavation of caverns;the unloading change of main-transformed cavern is in the top arch but with a shallow depth due to the excavating influence of adjacent cavern room;because the mechanical parameters of surrounding rock on the top of tailwater room is better than the top arch of the main powerhouse,the unloading extent is slightly less than that of the main powerhouse;the unloading extent of high sidewall in the tailwater room is greater than that of the powerhouse.