盾构隧道开挖对邻近桩基三维影响试验研究

Experimental Study on Three-dimensional Effects of Shield Tunnel Excavation on Adjacent Pile

参考清华园隧道盾构段全线近距离侧穿北京地铁13号线桩基的工程背景建立试验模型,开展卵石地层中盾构施工对邻近桩基三维扰动特征研究。试验模型中共布置5根模型桩(1#~5#桩)。以1#桩为例分析了盾构掘进过程对桩基的三维影响特征,发现附加弯矩主要产生在刀盘距桩基-0.5D至0D阶段,横向弯矩最大值是纵向弯矩最大值的2倍;附加轴力主要产生在-0.5D至1.5D阶段,桩顶附加沉降主要产生在-1D至1D阶段,桩端附加承载力在-0.5D至2D阶段持续增长。对比1#、2#和3#桩研究了桩-隧不同水平间距对桩基扰动规律的影响,发现桩基的附加沉降、附加弯矩和附加轴力均随与隧道水平距离的增大而减小,弯矩最大值的位置随着距离的增大而逐渐上移。对比1#、4#和5#桩分析了桩端相对竖向位置对桩基扰动规律的影响,得出桩端位于隧道拱顶的桩基的附加弯矩明显小于桩端位于中心线及拱底处桩基的附加弯矩。

Taking the Qinghuayuan tunnel passing the piles of Beijing Metro Line 13 in a short distance as the engineering background,the three-dimensional disturbance characteristics of shield tunnel excavation in the pebble stratum to the adjacent piles is conducted by a model test. Five model piles(piles 1#~5#)were arranged in the test model. Taking pile 1# as an example,the influence of the excavation distance D on the three-dimensional disturbance law of the pile is studied. The test results indicate that the additional bending moment mainly occurs in the range of-0.5D to 0.0D;the maximum additional transverse bending moment is twice the maximum additional longitudinal bending moment;the additional axial force mainly occurs in the stage of-0.5D to 1.5D;the additional settlement on the pile top mainly occurs in the stage of-1D to 1D;and the additional load at the pile bottom continuously increases in the range of-0.5D to 2.0D. Test results of piles 1#,2# and 3# show the influence of the horizontal distance between the pile and the tunnel on the disturbance of the pile. It can be found that the additional settlement,additional bending moment and additional axial force of the pile decrease as the horizontal distance between the pile and the tunnel increases,but the position of maximum bending moment moves up. Test results of piles 1#,4# and 5# present the impact of the position of the pile bottom on the disturbance rule of the pile. Comparing the bending moments of piles1#,4# and 5#,it can be seen that the additional bending moment of the pile whose bottom is located at the tunnel crown with the same depth is the smallest.