沉管隧道大开挖回弹再压缩问题试验研究

Study on the Rebound-recompression of Large Excavation Immersed Tunnels

为准确计算沉管隧道大开挖引起的基础坑底回弹再压缩,对粉质黏土和粉砂两种土样开展室内试验研究。提出根据卸荷比大小分段考虑回弹模量参数取值,对再压缩模量取为定值,归一化处理后进行回弹和再压缩的变形量计算,并与已有回弹量实测值的工程实例对比分析,结果表明新方法计算结果与工程实测结果吻合较好。运用该方法分析港珠澳大桥海底沉管隧道工程,确定了隧道开挖卸荷最大影响深度为开挖深度的1.73倍,强回弹区回弹量约为总回弹量的60%,为准确控制海底沉管隧道的最终变形量提供理论依据。

To get more accurate value of rebound and reloading settlement of immersed tunnel during excavation,laboratory experiments on silty clay and silty sand are performed. A parameter selection method of resilience modulus considering unloading ratio by sections is proposed. After normalization process,the values of the resilience and recompression modulus are calculated with constant recompression modulus,which are compared with the in-situ measured values. The results show that the new calculation method gives good agreement with the measured values. Applied to the project of Hongkong-Zhuhai-Macao bridge,the maximum influence depth is found to be 1.73 times of the excavation depth,and the resilience of the main rebound area account for 60% of the total resilience. The results are useful for determining the final settlement of the immersed tunnel more accurately.