Canadian Geotechnical Journal, Ahead of Print.
This study conducted both three-dimensional physical model tests and numerical back-analyses to examine the performance of a single pile subjected to twin tunnelling beneath the pile toe in dry sand. Moreover, numerical parametric analyses were carried out to assess the impact of working load level and tunnel volume loss on pile behaviour. The findings revealed that the first tunnelling induced a 1.9%dp (pile diameter) settlement in the pile when the pile toe was 0.5 D (tunnel diameter) above the twin tunnels, which had a 1.0% volume loss. The settlement was accompanied by an upward load transfer mechanism. The second tunnelling had a reduced impact and induced only 76% of the settlement caused by the first tunnelling. The study also showed that tunnelling-induced shearing behaviours weakened beneath the pile toe with a decrease in working load, resulting in reduced pile head settlement. Moreover, the computed pile settlement increased by 178% when the tunnel volume loss increased from 0.5% to 2%. The findings of this study offer valuable data for the validation and calibration of numerical models. In addition, the outcome from this study provides useful insights into the prediction of the pile-soil-tunnel interaction when subjected to twin tunnelling.

中文翻译：

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干砂中单桩双隧道诱发沉降和荷载传递机制评估

加拿大岩土工程杂志，印刷前。
本研究进行了三维物理模型试验和数值反分析，以检查在干沙中桩趾下方进行双隧道施工的单桩的性能。此外，还进行了数值参数分析，以评估工作荷载水平和隧道体积损失对桩性能的影响。研究结果显示，当桩趾距双隧道上方 0.5 D（隧道直径）时，第一次隧道开挖会引起桩内 1.9%dp（桩直径）的沉降，从而导致体积损失 1.0%。沉降伴随着向上的荷载转移机制。第二次隧道施工的影响较小，引起的沉降仅为第一次隧道施工的 76%。研究还表明，随着工作荷载的减少，隧道施工引起的桩端剪切行为减弱，导致桩头沉降减少。此外，当隧道体积损失从0.5%增加到2%时，计算的桩沉降增加了178%。这项研究的结果为数值模型的验证和校准提供了有价值的数据。此外，这项研究的结果为预测双隧道施工时桩-土-隧道相互作用提供了有用的见解。