客运专线机场路隧道下穿高架桥近接桩基施工位移控制技术

Adjacent Pile Foundation Construction Displacement Control Technology of Passenger Dedicated Line Jichang Road Tunnel Crossing under Viaducts

以成都—绵阳—乐山客运专线机场路隧道下穿成都市蓝天立交桥工程中近接12根高架桥桩基为例,研究近接桩基施工位移控制技术。根据相关规范及相似工程研究成果,制定机场路隧道近接桩基沉降控制标准和水平位移控制标准。建立机场路隧道下穿高架桥段的仿真模型,依据工程地质情况和设计支护参数,确定计算模型物理力学参数,对近接桩基隧道施工进行开挖模拟计算。计算结果表明:12根近接桩基的沉降值和差异沉降值均小于预警值,但是水平位移值均大于允许值,必须采取加固措施才能进行施工。提出在机场路隧道两侧设置隔离桩的加固方案,并计算采取加固措施后的近接桩基沉降及水平位移值。结果表明:12根近接桩基沉降值和差异沉降值均有较大的减少,水平位移值亦大为减小且均小于预警值,机场路隧道可以正常施工。

Twelve viaduct pile foundations are located in the vicinity of Jichang road tunnel of Chengdu-Mi- anyang-Leshan passenger dedicated line across Lantian viaduct in Chengdu. With the example, the con- struction displacement control technology of adjacent pile foundations was studied. Firstly, according to the relevant specifications and research results of similar engineering, the settlement and horizontal dis- placement control standards of adjacent pile foundation of passenger dedicated line Jichang road tunnel were established. Secondly, aiming at the section of Jichang road tunnel across Lantian viaduct, the simulation calculation model was established. In accordance with the geological condition and the designed support pa- rameters, the physical and mechanical parameters of calculation model were determined. Lastly, the process of adjacent pile foundation tunnel excavation computational results show that the settlement and was simulated by employing numerical method. The differential settlement values of twelve adjacent pile foundations are less than early-warning values, but the horizontal displacement values of twelve adjacent pile foundations are greater than the allowable values. Therefore, only adopting reinforcement measures can Jichang road tunnel carry on the construction. Thus, the reinforcement measure of installing isolation pile foundations at either side of the Jichang road tunnel is presented. The settlement and horizontal dis- placement values of twelve adjacent pile foundations are calculated after adopting pile foundation reinforce- ment measures. The results show that the settlement and differential settlement values of twelve adjacent pile foundations have decreased greatly. The horizontal displacement values of twelve adjacent pile founda- tions have also reduced extraordinarily and are less than early-warning values. So, Jichang road tunnel can carry on the construction smoothly.