Seismic Fortification Analysis of the Guoduo Gravity Dam in Tibet, China

Table 2

Rock mass classification for the Guoduo dam foundation.

Class	Rock mass structure	Rock mass description	Weathering	Uniaxial compression strength (MPa)
III1A; III2A	Thick layered structure surface, steep dip structural plane in abutment	Hard rock, intact and massive, high strength, antislip deformation resistance controlled by the structural planes. Weak rock mass is affected by weathering and unloading; local rock mass is poor	Fresh to slightly; Weak	Rb > 60 MPa
IV1B; IV2B	Interbedded or lamellar structure; some structures may cause dam foundation and abutment instability	Rock masses are relatively poor intact, antislip deformation resistance controlled by the structural planes and rock mass of chimeric ability. The rock mass cannot be directly used as dam foundation and must be effectively reinforced before used locally	Fresh to slightly; Weak	Rb = 30–60 Mpa
IVC	Interbedded or lamellar structure; some structures obviously cause dam foundation and abutment instability	Soft rock, rock intact, low strength, antislip, and deformation resistance performance are poor. The rock mass cannot be used as dam foundation and is excavated	Fresh to slightly	Rb < 30 MPa