Design and research of prestressed rock bolt crane girder under adverse geological conditions

Abstract

The code NB/T 35079—2016 does not provide clear guidance on the design of crane girders for underground power plants under adverse geological conditions. Due to the difficulty in accurately estimating the release of rock mass stress under adverse geological conditions, the non-prestressed rock dowels have a large scatter in their tensile force, which makes it difficult to fully guarantee the safe and stable operation of the crane girder. A design scheme of re-tensionable prestressed rock bolt crane girder was proposed. The prestressed rock bolt penetrates into the stable rock mass, and is less affected by the release of rock mass stress. During construction and operation, if the prestressed rock bolt is overloaded, it can be relaxed and re-tensioned to ensure long-term safe and stable operation. Numerical calculations show that the prestressed rock bolt crane girder can closely contact the rock mass, with more reliable overall stability compared to the non-presstressed rock dowel crane girder, which is beneficial for reducing the gap between the rock mass and the structure, and ensure the effective exertion of cohesion and friction between the structure and the rock mass, thus improving the overall stability of the crane girder. Finally, the prestressed rock bolt crane girder of the Kokhav Hayarden pumped storage underground power plant in Israel is used as a case study, which verifies that the prestressed rock bolt crane girder has a large safety margin and the design is reasonable and feasible.

Keywords

adverse geological conditions / stress release / re-tensioning / prestressed rock bolt / crane girder / attached prestressed concrete wall