New performance-based seismic design thought and stability evaluation of underground engineering
Jichang Zhao1,2, Yuanxue Liu1,2, Yu Zhang1,2, Yizhong Tan1,2
COMPUTER MODELLING & NEW TECHNOLOGIES 2014 18(12D) 60-68
1School of Logistic Engineering University of PLA, Chongqing,401311,China
2Chongqing key Laboratory of Geomechanics & Geoenvironmental Protection, Logistical Engineering University, Chongqing, 401311, China
With the rapid development of the national economy and the urban modernization, the traditional intensity-based (or displacement-based)seismic design method can longer meet the demand of the seismic design of modern buildings in recent years, which is much more obviousespecially for the seismic design of underground engineering. In this paper,aimed at the prominent problems for seismic safety of underground engineering at present, the prospectiveperformance level and fortification objective based on specific structural forms, surrounding rock classifications, support types and other factors of underground engineering are determined, to ensure to fully play its functional performance and to minimize the overall lossunder seismic effect that may occur inthe whole life period; Based on the dynamic and static combined cycling loading method and the design strategy of the structure performance, this paper adopts the combination method of similarity physical model experiment and the numerical analog calculation to conduct dynamic damaging mechanism and performance standard design research of underground off-wall tunnel.The research results show that the dynamic and static combined cycling loading method can better reflect the generation and expansion progress of the inner micro cracks of rocks and concrete materials, thus it is an effective method to research into the damaging rules and stability of the underground off-wall tunnel; the plasticity displacement, strain and pressure stress changes of the monitoring point can better describe the damaging status of the underground projects; the increase of load magnitude can obviously result in the displacement of the monitoring point vault, which may cause the first transcending damage of the tunnel, and the cycling loading will show accumulated damage with the load magnitude positively related to the degree of accumulated damage; the strain of the monitoring point will undergo sudden changes when reaching the ultimate pressure value, while the crack width parallel to the tunnel diameter is the reference to the damaging status of the underground tunnel; the experimental and numerical simulated results coincide with each other, and can well represent the performance standard of the underground tunnel, thus providing the reference for the earthquake and explosion effect, as well as the protection a design of the underground tunnel.