近距离开挖卸荷条件下运营地铁高架桥墩响应研究

上海地铁12号线龙漕路车站基坑下穿运营3号线高架，施工条件受限，需要对位于基坑中间的高架桥墩进行保护以确保3号线运营安全。依托该工程，采用精细化三维数值分析、室内试验和现场实测等方法，对近距离开挖卸荷引起的高架桥墩响应进行研究。监测结果表明：软土地层高架桥墩在近距离开挖卸荷影响下均产生上抬，与数值分析结果吻合；桥墩水平位移总体上朝向卸荷一侧，但发展过程中震荡明显且位移较大，位移终值基本符合数值分析的预估值；近距离卸荷导致桥墩基础桩极限承载力有轻微的损失，但基本不会威胁高架桥的安全；长期沉降表现为半周卸荷条件下上抬可略有恢复，全周卸荷下则不会恢复。

A study on the response of the piers of operating metro viaducts under the excavation-induced unloading condition

The foundation pit of Longcao Road Station of Shanghai Metro Line 12 passes through beneath the viaduct of operating Metro Line 3, so that the pier located in the middle of foundation pit needs protection to ensure the safety of Metro Line 3. Based on the project above, the piers response of viaducts due to unloading is analyzed with combination of 3D numerical method, laboratory test and field test. It is shown that the piers in soft soil rises due to unloading, which agrees well with numerical estimation. The horizontal displacement of piers develops toward the unloading side with significant fluctuations during the process, and the final deformation is consistent with numerical simulation. Unloading leads to a slight loss of ultimate bearing capacity of piles, but it does not threaten the safety of viaduct. Upheaval of piers recovers partly under semi-surrounding unloading condition, and it does not recover under surrounding unloading condition.