Abstract Face bolting and umbrella arch techniques are widely adopted to increase the stability of tunnels in conventional tunnelling. Nevertheless, owing to incomplete theoretical analysis models, their design mainly depends on the judgment and experience of engineers. Therefore, a safety factor analysis model and a concise design flow for a reinforced tunnel face are established based on the limit equilibrium method and the strength reduction technique, in which the failure modes of a tunnel face and an unsupported span as well as the effects of face bolts and an umbrella arch are considered. In this method, the role of the face bolts is to improve the tunnel face stability by generating supporting pressure, which is stimulated by the cable model. The role of the umbrella arch is to improve the stability of both the tunnel face and the unsupported span by the load transfer effect, which is simulated by the Winkler beam model. To validate the accuracy of this method, the calculation results are contrasted with those obtained by other typical theoretical models and numerical software, which show good agreement. The stability of the Yenikapi-Unkapani tunnel is analyzed, and the practicability of the proposed model is determined. Finally, parametric analyses are conducted to discuss the effects of face bolts and an umbrella arch on the stability of a tunnel face and an unsupported span.

中文翻译：

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粘性-摩擦土中锚杆和伞拱加固隧道掌子面稳定性分析模型

摘要 传统隧道掘进中广泛采用端面锚杆和伞拱技术来提高隧道的稳定性。然而，由于理论分析模型不完整，其设计主要依赖于工程师的判断和经验。因此，基于极限平衡法和强度折减技术，建立了加筋掌子面的安全系数分析模型和简明设计流程，其中掌子面和无支护跨的破坏模式以及考虑面螺栓和伞拱。在这种方法中，掌子面螺栓的作用是通过产生支撑压力来提高隧道掌子面的稳定性，这是由索模型激发的。伞拱的作用是通过荷载传递效应提高掌子面和无支护跨度的稳定性，通过Winkler梁模型进行模拟。为验证该方法的准确性，将计算结果与其他典型理论模型和数值软件的计算结果进行对比，结果吻合良好。对Yenikapi-Unkapani隧道的稳定性进行了分析，确定了该模型的实用性。最后，通过参数分析讨论了掌子面螺栓和伞拱对掌子面稳定性和无支撑跨度的影响。计算结果与其他典型理论模型和数值软件得到的结果进行对比，显示出较好的一致性。对Yenikapi-Unkapani隧道的稳定性进行了分析，确定了该模型的实用性。最后，通过参数分析讨论了掌子面螺栓和伞拱对掌子面稳定性和无支撑跨度的影响。计算结果与其他典型理论模型和数值软件得到的结果进行对比，显示出较好的一致性。对Yenikapi-Unkapani隧道的稳定性进行了分析，确定了该模型的实用性。最后，通过参数分析讨论了掌子面螺栓和伞拱对掌子面稳定性和无支撑跨度的影响。