中文摘要：

地下工程的施工过程是一个几何形状逐步变化的不完整结构在时间和空间上承受不断变化的施工荷载的受力过程。本文以新考塘隧道出口扩大段特大跨度隧道工程为背景,通过数值模拟方法,对第1次初期支护、临时支护、第2次初期支护的受力随施工过程的变化规律进行了研究。研究结果表明：支护受力体现施工过程相关性,并不一定终态是最不利状态,具体到本工程,④部作业相对最危险,⑤部作业反倒改善了支护结构受力;从拆撑以后的双层初期支护受力来看,第2次初期支护是有效的,拆撑风险是可控的;最小安全系数的量值分布呈现＂第2次初期支护〉第1次初期支护〉临时支护＂的规律。

英文摘要：

The construction process of underground engineering is a stress process of structure in time-space. The stress process of first primary support,second primary support and temporary support of extra-large span tunnel of enlarging section of Xinkaotang Tunnel Portal during construction is analyzed. The analytical results show that： 1） The support stress state shows the procedural dependency; and the final state is not always the worse. 2） The second primary support is effective; and the risk of support disassembling can be brought under control. 3） The safety factor of second primary support is the largest,followed by that of first primary support,and that of temporary support is the smallest.