Quantitative stability evaluation of multi-tunnel structure is an important issue related to the safety assessment and stable construction of geotechnical underground tunnels. In this work, the overall failure process of twin tunnels were exhibited by a physical simulation based on the 3D printing (3DP) sandstone analogues model, and a safety factor method was also presented for evaluating the general safety of multi-tunnel structure. For checking the 3DP material performance of physical model, uniaxial and triaxial compressions for the 3DP cylinder specimens were first tested and showed that their mechanical properties and failure characteristics were similar to natural rock in general. Then, the overloading tests for twin-tunnel model were carried out and have exposed the critical position of overall failure of twin-tunnel structure through visual observation and automatic measurement. Testing results and corresponding numerical back analysis indicated that the connectivity of plastic strain between tunnels can be deemed as the conservative instability criterion (i.e. yielding of material) and the inflection point of tunnels’ displacement can be deemed as overall failure criterion (i.e. structure failure) for twin-tunnel structure. The safety analysis for underground hydraulic caverns indicated that this method can provide a reference for quantitative and reasonable evaluation of the general safety of multi-tunnels or caverns and the local instability zone of surrounding rock.

中文翻译：

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3DP物理双隧道模型的失效性能及相应的安全系数评估

多隧道结构的定量稳定性评价是关系到地下岩土隧道安全评价和稳定施工的重要问题。在这项工作中，通过基于 3D 打印 (3DP) 砂岩类似物模型的物理模拟展示了双隧道的整体破坏过程，并提出了一种用于评估多隧道结构总体安全性的安全系数方法。为了检查物理模型的 3DP 材料性能，首先测试了 3DP 圆柱体试样的单轴和三轴压缩，结果表明它们的力学性能和破坏特征与一般的天然岩石相似。然后，开展了双隧道模型的超载试验，通过目视观察和自动测量，揭示了双隧道结构整体失效的关键部位。试验结果和相应的数值反分析表明，隧道之间塑性应变的连通性可以看作是保守的失稳准则（即材料屈服），隧道位移的拐点可以看作是整体破坏准则（即结构破坏）为双隧道结构。地下水力洞室安全分析表明，该方法可为多隧道或洞室整体安全性及围岩局部失稳带的定量合理评价提供参考。试验结果和相应的数值反分析表明，隧道之间塑性应变的连通性可以看作是保守的失稳准则（即材料屈服），隧道位移的拐点可以看作是整体破坏准则（即结构破坏）为双隧道结构。地下水力洞室安全分析表明，该方法可为多隧道或洞室整体安全性及围岩局部失稳带的定量合理评价提供参考。试验结果和相应的数值反分析表明，隧道之间塑性应变的连通性可以看作是保守的失稳准则（即材料屈服），隧道位移的拐点可以看作是整体破坏准则（即结构破坏）为双隧道结构。地下水力洞室安全分析表明，该方法可为多隧道或洞室整体安全性及围岩局部失稳带的定量合理评价提供参考。材料的屈服）和隧道位移的拐点可以作为双隧道结构的整体破坏准则（即结构破坏）。地下水力洞室安全分析表明，该方法可为多隧道或洞室整体安全性及围岩局部失稳带的定量合理评价提供参考。材料的屈服）和隧道位移的拐点可以作为双隧道结构的整体破坏准则（即结构破坏）。地下水力洞室安全分析表明，该方法可为多隧道或洞室整体安全性及围岩局部失稳带的定量合理评价提供参考。