Engineering Geological Study On Caverns Of The Underground Powerhouse At Ma'erdang Hydropower Station

Most of the hydropower resources are in rugged mountainous and valleys area with steep riverbank, narrow and big flow valleys. It is ususally needed to construct underground cavern to install water power generators in this area. But the underground caverns position are in relation to the success or failure of underground engineering, once the position selection undeserved, it would cost huge. So it is necessary to carry on underground powerhouse schemes comparison choice.With big span and high sidewall, underground powerhouse system will inevitably meet complicated geological conditions and a lot of engineering geological problems, among which the biggest concern is the stability of surrounding rock.So taking the underground powerhouse of Ma'erdang hydropower station on yellow River as an example, some problems closely related to the site election of underground caverns were analyzed in detail from the engineering geologic points of view. Based on the regional environment and engineering geological conditions of the dam area, according to perform detailed investigation and tests, the relevant materials widely collected, and a large amount of numerical test researches, from the angle of basic geology condition, rock quality, caverns stability and geological disasters produced in the excavation, three underground powerhouse caverns schemes of the power station were compared and elected the best one.For Ma'erdang hydropower station underground caverns engineering geology, the main research contents are:(1) geological environment of this region and project area; (2) stress field characteristics, including regional tectonic stress field principal compressive direction, and project area spatial stress distribution characteristics, principal stress direction and stress values, etc; (3) the developmental characteristics and distribution of occurrence, developed degree, surface morphology, filling material and so on of structural plane in powerhouse area, the rock mass structure comprehensive classification and mechanics parameter value selection of structural plane; (4) Rock quality evaluation with the various methods of surrounding rock mass classification BQ, RMR, Q-system and Hydropower norm method, etc, and powerhouse area rock quality spatial distribution characteristics and surrounding rock mechanics parameter value selection problem; (5) underground cavity stability analysis which was used to evaluate powerhouse construction and operation safety, including global stability analysis and local stability analysis; (6) caverns axle direction election attempt, based on analysis of stability of powerhouse caverns; (7) preliminary analysis and exploration on water infow and rockburst forecast problems of powerhouse area.