Study on Seismic Responses and Vibration-absorption Measures for Extra-long Tunnel of the Shallow Section in High Intensity Earthquake Zone
|School||Beijing Jiaotong University|
|Keywords||mountain tunnel seismic damage analysis field dynamic characteristics earth pulsation dynamic response buffer layer aseismatic joint section optimization|
The implement of national significant construction project in West Region requires long and colossal tunnels which character themselves with large section and long length as well as pass through complex and disordered geological zone, approach or span fracture zone of seismic activity. Thus for the mountain tunnel located in the high seismic intensity area, the research on dynamic responses and measures of seismic resistance undoubtedly possesses great realistic significance. This paper conducted dynamic response analysis and study on measures of seismic resistance of shallowly buried tunnel in high intensity earthquake zone based on quake-proof and disaster-alleviation research topic of ChengLan railroad. The main content of this thesis includes:1. Some laws on mountain ridge tunnel’s mode of failure under seismic dynamic effect as well as influencing factor and mechanism of fracture of seismic damage are summarized via the investigation and analysis on tunnel and underground structures after Wenchuan earthquake.2. Some brief researches on mountain ridge tunnel’s dynamic properties and introduction, spectrum analysis about field monitoring of earth pulsation can be done so as to get some related field kinetic parameter and underlie the later dynamic analysis.3. Through the three-dimensional numerical analog computation about shallowly buried tunnel and comparative analyses on acceleration time-histories, velocity time-histories, displacement time-histories and stress time-histories abstracted from key positions of tunnel liner structures, some laws on dynamic responses are obtained.4. The results from the research of setting buffer layers show:buffer layer can effectively ameliorate the stress state of tunnel liner structure to some extent and have better capacity of shock absorption. Then some laws on shallowly buried tunnel trunk’s dynamic responses based on the property of materials used in buffer layers and condition of surrounding rock can be summarized by means of the analyses on analog computation of different material property (stiffness and thickness) and condition of surrounding rocks. Finally, based on the hypotheses of this text, some measures for shock-absorption and seismic-resistance applied in different conditions of surrounding rocks and designed values of the thickness of buffer layer are obtained.5. The results from the research on aseismatic joint’s effectiveness on shock absorption show:frist, the setup of aseismatic joint has distinct improvement on stress state of tunnel structure. Then, a reasonable designed value of aseismatic joint’s interval is obtained through the analyses on analog computation about different aseismatic joints’intervals.6. Some methods of enhancing the capacity of seismic-resistance considering the various section shapes underlying different surrounding rocks are obtained by means of section optimization of effectiveness on tunnel’s shock absorption.