During the tunnel construction under the road, the shallower the tunnel depth, the greater the effect of the surface settlement. Thus, to analyze the ground settlement caused by tunnel construction under ultrasmall distance, the research is based on a tunnel in Ningqiang County and uses numerical simulation and measurement to analyze the ground settlement and the effect of reinforcement measures. The research draws the following conclusions. For the ultrasmall distance tunnel under road construction, the combination of pipe shed and advanced small pipe grouting reinforcement measures inhibits the surface settlement. After the advanced small pipe is reinforced, the surface settlement value is reduced by about 25%, and the reinforcement effect is more obvious after the increase of the large pipe shed. The surface settlement value is reduced by about 60%. The surface settlement caused by the excavation of the circular soil accounts for about 50%–60% of the total settlement value, which is for the whole construction. The key processes, which involve the combination of reinforcement measures, focused on the suppression of surface settlement caused by the excavation of the circular soil. After the reinforcement measures, the variation of the settlement groove width was not obvious but the curvature and peak value of the settlement groove is reduced significantly.

中文翻译：

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超小距离下软岩隧道地基沉降规律研究

在路下隧道施工过程中，隧道深度越浅，地表沉降的影响越大。因此，为分析超小距离下隧道施工引起的地面沉降，以宁强县某隧道为研究对象，通过数值模拟与实测，对地面沉降及加固措施效果进行分析。研究得出以下结论。对于道路施工中的超小距离隧道，管棚与先进的小管灌浆加固措施相结合，抑制了地表沉降。先进小管加固后，表面沉降值降低25%左右，大管棚增加后加固效果更明显。表面沉降值降低约60%。圆形土开挖引起的地表沉降约占整个施工总沉降值的50%～60%。关键工序涉及加固措施的组合，重点是抑制圆形土开挖引起的地表沉降。加固措施后，沉降槽宽度变化不明显，但沉降槽曲率和峰值明显减小。重点是抑制圆形土开挖引起的地表沉降。加固措施后，沉降槽宽度变化不明显，但沉降槽曲率和峰值明显减小。重点是抑制圆形土开挖引起的地表沉降。加固措施后，沉降槽宽度变化不明显，但沉降槽曲率和峰值明显减小。