In order to find out the deformation and the distribution and change of internal force of the structure of a soft rock tunnel near a very broken area in different steps to distance case, and seek its reasonable excavation, Dujiashan tunnel of actual construction process near the "5. 12" earthquake seismogenic faults, the Longmen fault zone, is examined according to the three steps-reserving core soil methods for the tunnel. Based on the situ three-stage excavation, deformation of the tunnel under different working conditions and analysis of the structure stress are carried out. The results show that Fl and F2 conditions are the optimal footage for the very broken soft rock tunnel area. On the basis of 1, 1.5, 2, 2. 5, 3, 3. 5 m excavation, the numerical simulation method is used in the field test for supplement verification. The tunnel deformation after excavation, supporting force and the monitoring values are analyzed. The structure stability of the tunnel construction under different working conditions is evaluated. The results of numerical simulation for comprehensive analyses show that for the soft rock tunnel, the circulation footage should be in the range of 1 ~ 2. Successful application of the scheme in field test proves that the scheme is reasonable and effective. The research results provide references for similar project construction.%为探明极破碎区域软岩隧道在采取不同台阶间距情形下,隧道变形及结构内力的分布及变化规律,寻求其合理开挖进尺,本文结合“5.12”特大地震发震断裂——龙门山断裂带附近杜家山隧道的实际施工过程,根据隧道采取的三台阶+预留核心土方法,以现场试验段采取的3种开挖进尺为依托,对不同工况下隧道变形及结构受力进行对比分析,初步认为:F1及F2工况为极破碎区域软岩隧道的最优进尺.在此基础上对l、1.5、2、2.5、3、3.5m开挖进尺,采用数值模拟手段对现场试验进行补充验证,通过对开挖后隧道变形、支护受力与现场监测值的对比分析,进而对不同工况下隧道施工后结构的稳定进行评价,综合分析表明,对于软岩隧道,循环进尺应在l～2m间合理选择.现场试验段的成功运用也论证了这一方案的合理、有效性,其成果可供类似工程施工参考.
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