既有桩基对盾构施工参数的影响研究
Effects of existing pile foundation on parameters of shield tunneling
-
摘要: 盾构隧道施工邻近桥梁桩基已成为目前研究的热点问题。针对盾构施工参数取值在工程中的应用价值,利用三维弹塑性有限元分析了桩基引起地层的竖向附加应力,反推出了Geedes式中的桩端阻力、桩侧阻力分担桩顶荷载的比例系数与桩长的数学表达式,并将Geedes竖向附加应力影响范围与Randolph提出的影响半径对比分析后,给出了桩基影响区域和非影响区域的界定半径;基于支护压力、注浆压力的理论取值范围及单位长度上土体损失量等于沉降槽面积的条件,利用三维弹塑性有限元进行计算分析,给出了支护压力、注浆压力在桩基非影响区域内的建议取值和土体损失的计算表达式;基于桩基非影响区域内盾构施工参数的建议取值及桩基对地层产生的附加应力,给出了桩基影响区域内盾构施工参数建议取值的数学表达式。研究结果表明:工作面的土压力阻力选取工作面静止土压力合力,注浆压力选取1.1倍的隧道埋深处水土压力时,对地层的扰动较小。Abstract: The shield tunneling adjacent to bridge pile foundation has become a hot issue at present. In view of the application value of parameters of shield tunneling in projects, the vertical additional stress of the pile foundation is analyzed by using a three-dimensional elastic-plastic finite element method. The mathematical expressions for pile length and proportional coefficient are derived. The radii of impact area and non-impact area of piles are defined by comparing the influence area of additional stress generated by piles with the influence radius put forward by Randolph. The optimal values of tunnel face pressure and grouting pressure in the non-impact area of piles are obtained through three-dimensional elastic-plastic finite element analysis based on the theoretical values of tunnel face pressure and grouting pressure. The expression for calculating the ground loss is introduced under the condition that the soil loss per unit length equals the area of settlement trough. By combining the optimal values of the parameters of shield tunneling in the non-impact area and the additional stress generated by piles, the mathematical expressions for the parameters of shield tunneling in the impact area are achieved. The results show that when the soil pressure resistance of tunnel face equals the static soil pressure of tunnel face and the grouting pressure equals 1.1 times the soil and water pressure on the top surface of tunnel, the disturbance of the soil strata is relatively slight.