临近混凝土管桩基础建筑物盾构掘进地层损失控制

Ground Loss Control During Shield Tunnelling Adjacent to Buildings Supported by Concrete Pipe Piles

以福州地铁2号线盾构近距离侧穿管桩基础建筑物为工程依托,采用三维有限元并结合现场变形监测数据,分析了30cm盾尾间隙条件下双线盾构掘进引起的地表变形、建筑物倾斜及不同位置基桩内力的变化。结果表明,当盾构掘进引起的地层损失率达到1. 5%时,地表沉降>30mm控制值,而此时建筑物的沉降和倾斜均远小于控制标准,但基桩最大累计弯矩达到抗裂弯矩检验值的63. 5%,较施工前增大11. 8%。本次综合地表变形和基桩附加弯矩变化,建议地层损失率控制在1%。最后,推导了同步注浆量上下限计算方法,并基于现场同步注浆参数及地表沉降监测数据,得出同步注浆浆液在全断面砂层、砂-淤泥质土互层、全断面淤泥质土中的扩散系数。

During the construction of Fuzhou Subway line 2,the shield machine is tunnelling adjacent to pipe piles subjected to different kinds of buildings.On basis of the tunnelling practice,3 D finite element method combined with the data of the deformation measured in field is used to analyze the variation of surface deformation,building inclination and internal force of the foundation piles caused by double line shield tunnelling with 30 cm shield tail clearance.The results show that when ground loss ratio reaches1.5%,ground subsidence is larger than the subsidence control value 30 mm;nevertheless the settlement and incline of the buildings are much smaller than the control thresholds.However,the maximum calculative moment of the pile reaches to 63.5%of the test values of crack moment,which is 11.8%larger than the moment before construction.The ground loss ratio 1%is set as the control limit by considering the maximum additional moment and ground subsidence.Finally,the method of calculating the lower and upper limits of the volume of synchronous grouting slurry is derived,and the permeability coefficients of the synchronous grouting slurry in the full section of sand layer,the sand-silty soil interlayer and the full section of silty soil are obtained based on the parameters of synchronous grouting and the measured ground subsidence.