Characteristics of displacements and stress in surrounding rock and back analysis of displacement of underground powerhouse at Xilongchi storage power station

The strata in the powerhouse area of Xilongchi pumped storage power station are composed of argillaceous oolitic limestone, lamellate striped limestone and lamellate quartz siltite, under an almost horizontal occurrence condition. The axis of the powerhouse intersects the main faults and fissures with large angles. Characteristics of displacements and anchor bar stress in the surrounding rock present significant anisotropy. The surrounding rock displacement at sidewall (average 3.0 mm) and the anchor bar stress (average 45 MPa) are both less, which all be treated as displacements and anchor bar stress characteristics in surrounding rock of underground powerhouse within an inter bedding mass of almost horizontal lamellate limestone and siltite limestone. It shall be necessary to check out the reasons which cause such displacements and anchor bar stress. Horizontal stress, vertical stress and deformation modulus have been obtained by back analysis. Deformation modulus from back analysis is in agreement with that from field testing of deformation modulus. Characteristics of displacements and anchor bar tress in surrounding rock can be explained by result of back analysis. Rational parameters can be provided for construction in lamellar rock by using back analysis of displacement combined with field testing of deformation modulus.