Seismic stressed state of underground hydraulic structures at the Rogun hydroelectric station

Abstract

An investigation of the seismic stressed state of underground hydraulic structures, as is known, can be carried out as with above-ground structures within the framework of various theories of seismic stability (static, linear-spectral, calculation for a given accelerogram), but their application to underground structures has substantial special features. First of all, the stressed state of an underground structure (e.g., a tunnel lining) is determined not only by the inertial loads from the weight of the structure itself but also by the seismic stressed state of the surrounding rock mass ("noninertial rock pressure"). The inertial loads are found by equations of the linear-spectral theory, whereupon owing to the difficulties related to a determination of the frequency and modes of natural oscillations of underground structures the static theory is usually used. In design practice a special quasistatic method which permits taking into account certain basic characteristics of the action and object is used for determining the seismic stressed state of underground structures and earth masses from noninertial loads (stress waves) [1-3]. The seismic stresses during passage of plane harmonic longitudinal waves (schematization of the action) are determined as