Further development of the western area of China involves massive construction of highway, high speed railway, hydraulic and hydropower engineering. Within these projects, underground rock engineering is key components. At the same time, because of the complex geological environment in the western part of China, these major rock underground engineering are under the threat of high-risk strong earthquakes. Thus, the seismic safety of underground engineering is a major scientific issue urgently needed to be resolved and is major guarantees of national security and economic development.
With the support of the National Basic Research Program of China (Project 973, grant no. 2015CB057905) entitled ‘Seismic Analysis of Major Underground Rock Engineering’, research campaign was launched by a research team led by IRSM's Prof. SHENG Qian. With the research team’s continuous efforts, phased progresses were made.
Rock mass structure not only plays a decisive role in the excavation stability of underground rock engineering, but will also dominate the failure mechanism under earthquake. Thus, seismic stability study of the underground rock engineering requires a methodology that takes full account of rock mass structure. In this research project, dynamic properties of joints and faults are firstly obtained via cycle shear test. Followed by development of pre-processors for existing 3D discontinuous numerical software. In this manner seismic analysis procedure with the capability to simulate sophisticated rock structure is set up. Entire process of seismic failure was simulated with this technique, on which seismic failure modes were categorized for various rock mass structure type. Meanwhile, dynamic couple mechanism between spectral characteristics of ground vibration and rock mass structure is further studied. Subsequently, selection of seismic performance measure is specified based on the state of the art concept of Performance Based Earthquake Engineering. The stability criterion corresponding to various seismic failure model is then established. Ultimately, aseismic strategies are proposed with thorough understanding of the mechanism for each reinforcement measure.
Prof. SHENG’s research team has cooperated with Changjiang Institute of Survey, Planning, Design and Research (CISPDR) and PowerChina Huadong Engineering Corporation Limited (PowerChina Huadong) for the two major Chinese underground rock engineering located in western China. One is the underground powerhouse of Baihetan hydropower plant, which is currently the world’s largest underground cavern that under construction and is affected by the potential earthquake threat of a 219-gal design peak ground acceleration. The other is the Xianlushan water dispersion tunnel that planned to across the active Longpan-Qiaohou fault, which suffered the active fault’s strong threat brought upon by the combined fault rupture deformation and subsequent seismic excitation. Members of Prof. SHENG’s team, A.P. LENG Xianlun and A.P. CUI Zhen, conducted the consultation work on seismic fortification issues for the two projects, respectively.
The above research is also financially supported by the National Natural Science Foundation of China, (nos. 41672319, 51779253), and the National Key R&D Program of China (no. 2016YFC0401803). Further research work is under way and relative papers has published at Rock Mech Rock Eng and Bull Eng Geol Environ.