Failure modes and mechanisms for rock masses with staggered zones of Baihetan underground caverns under high geostress
DUAN Shuqian;FENG Xiating;JIANG Quan;LIU Guofeng;XU Dingping;YAO Zhibin;FAN Yilin;WANG Pengfei;State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences;Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines,Northeastern University;China Three Gorges Corporation;
The underground powerhouse caverns at Baihetan under construction are quite huge and have the characteristics of high side wall,large span,high geostress and complicated geological conditions. In the process of excavation unloading under high geostress,the caverns have been affected by several large staggered zones with poor ductility and mechanical properties. As a result,the rock masses with staggered zones have encountered various kinds of deformation and failure problems. On the basis of the collected data from the geological,construction,monitoring,testing and numerical analysis,the engineering properties of staggered zones are described in detail in terms of occurrence,causes and characteristics. The instances of distortion failure or destruction of engineering rock mass structure induced by the staggered zones are summarized. From the point of view of the structure controlling,the failure modes of rock masses with staggered zones are categorized into the plastic squeezing-out tensile failure,the structural stress-induced collapse/block-fall and the contact shear slip failure. The characteristics of three failure modes are studied and analyzed regarding the spatial and temporal development,the morphology,the scale of destruction and so on. The corresponding mechanisms of three kinds of failures are revealed initially. A typical example of structural stress induced collapse is presented to further explain the analysis and prediction of failure mode and supporting measures.