北京某深基坑桩锚支护结构监测与分析

Monitoring and Analysis of the Pile-anchor Retaining Structure of a Deep Foundation Excavation in Beijing

以北京某深基坑桩锚支护结构监测数据为依据,结合理论计算分析,探讨预应力锚杆实际受力与理论计算结果出入大的问题。实测结果表明:锚杆张拉锁定时的预应力损失为10%~30%,在基坑开挖过程中锚杆轴力增加不明显,增加量<5%;基坑开挖至设计标高后的长期监测数据显示,锚杆轴力减少5%~10%。锚杆轴力监测值仅为设计值的1/2~2/3,实际作用于支护结构上的土压力远小于理论值,基坑最大水平位移为14.5mm,基坑周边建筑的最大沉降量为2.6mm,支护桩的深层水平位移最大值为7.34mm,各项监测数据偏低,该基坑支护设计相对保守。

Based on the monitoring data of the pile-anchor supporting structure of a deep foundation excavation in Beijing,the problem that the actual stress of prestressed bolt differs greatly from the result of the theoretical calculation is discussed.The measured results show that the prestress loss of anchor bolt when tensioning and pulling is 10%~30%and the increase of anchor bolt axial force is less than 5%in the process of foundation excavation.The long-term monitoring data from the foundation excavation to the design elevation shows that the reduction of anchor bolt axial force is 5%~10%.Bolt axial force monitoring value is only 1/2~2/3,design value of the actual effect on the earth pressure on retaining structure is far less than the theoretical value,the maximum horizontal displacement of foundation excavation is 14.50 mm,surrounding the foundation excavation construction the maximum settlement is 2.6 mm,the deep horizontal displacement of supporting pile a maximum of 7.34 mm,the monitoring data on the low side,the design of foundation excavation supporting is relatively conservative.