营运期地铁盾构隧道动力响应分析

采用三维动力有限差分法,考虑接缝、管片分块和软土地层等因素,对广州地铁四号线埋置于深厚软土地层之中的盾构隧道在地铁营运期间动力响应进行深入分析,并对考虑管片接缝与否2种计算模式进行比较分析。研究结果表明,地铁列车动载作用下,隧道动力响应自底部向顶部逐渐衰减,强烈区主要集中在下半部。管片环动力响应与接缝分布有关,临近接缝部位的动力响应值比远离接缝部位的动力响应值要大些。隧道基土动力响应强烈区主要分布于贴近管片环外围的一定范围内,越接近管片环、愈接近隧道底部,基土动力响应愈为强烈。地层动力响应由隧道壁往外快速衰减,受振区主要集中在距隧道中心约2倍隧道直径范围的近域地层内。当针对管片衬砌结构本身进行动力响应分析时,若把管片衬砌当整体考虑则会引起较大误差,故应考虑管片接缝;当针对地层进行动力响应分析时可不考虑接缝而把管片衬砌当成整体考虑,由此带来的误差在一般情况下可忽略不计。

ANALYSIS OF DYNAMIC RESPONSES OF SHIELD TUNNEL DURING METRO OPERATION

The impacts of metro operation against shield tunnel are analyzed.An elastoplastic three-dimensional dynamic finite difference modeling is employed.By considering the joints,the segments and the weak stratum,numerical simulations are performed for dynamic response of shield tunnel buried in thick soft soil under vibrating load induced by metro train.Comparative analysis has been done for joint-considered and non-joint-considered of segments lining.Results of numerical simulations show that metro operation induces significant dynamic response in shield tunnel.The dynamic response of shield tunnel is attenuated gradually from bottom to top of tunnel.The severe dynamic response zones are mainly distributed in the range of lower half of tunnel.The dynamic response of segments lining is affected by the arrangement of joint.In two horizontally symmetrical corresponding positions of segments lining,dynamic response of the one approaching to joint is severer than that of the one apart from joint.The severe dynamic response zones of tunnel foundation cling to around segment-ring.The nearer the zone is to segment,the severer the response is;and the nearer the zone is to the bottom of tunnel,the severer the response is.The dynamic response of stratum is damped quickly from tunnel wall to deep stratum.The obviously vibrated zones of stratum are mainly distributed in the range of about two times the tunnel scale from tunnel axis.The errors will be large for the exact analysis of dynamic response of segments lining structure itself if the segments lining is regarded as a whole tube body with non-joint-considered,so the joints should be considered for segments lining structure analysis.While the difference of results between joint-considered and non-joint-considered is small and it can be ignored somewhat for analysis of dynamic response of stratum.Therefore,the joints can be ignored,and the segments lining structure can be regarded as a whole tube body for stratum analysis to improve efficiency.