群桩施工引起邻近场地扰动变形的试验研究

在邻近既有线的新建线地基上进行大面积群桩施工可能对既有线带来不利影响。依托鲁南高速铁路并轨段路基工程,开展不同桩型群桩成桩现场试验,研究大面积群桩成桩对邻近场地变形的影响,并将试验成果应用于新建线地基加固方案中。群桩施工扰动引起的邻近场地水平位移与竖向位移随成桩排数的增多呈现先增大后逐渐稳定的趋势,位移发展经历快速、慢速和逐渐稳定3个阶段;引孔深度15 m及20 m成桩工艺对静压管桩挤土变形的防控效果显著;以1. 5 mm为变形特征值时,管桩群桩引起地表隆起变形范围在0. 4倍桩长以内、横向变形范围在2倍桩长以内,微型桩及灌注桩引起邻近土体变形范围都在5 m以内;采用灌注桩群桩对鲁南高速铁路并轨段路基进行地基加固,既有路基坡脚测点向外位移最大值在1. 0 mm以内,表明既有路基基本不受施工扰动影响。

Experimental Study on Disturbing Deformation of Adjacent Sites by Group Pile Construction

Large-area group pile construction on the adjacent new line foundation may have an adverse impact on the existing line.Based on the connecting subgrade section of Lunan high speed railway,the pile group tests with different pile types were carried out to study the inf luence of large-area piles on disturbing deformation of adjacent sites,and the reseaches results were applied to the new line foundation reinforcement scheme.The horizontal and vertical displacements of the adjacent sites caused by the pile group construction disturbance increase f irstly and then gradually stabilize.The displacement development experience three stages of rapid,slow and gradual stability.The pile-forming process with a depth of 15 and 20 m is effective in preventing and controlling the deformation of static pressure pipe piles.When the deformation characteristic value is 1.5 mm,the deformation of the surface uplift caused by the piles of the piles is within 0.4 times of the pile length,and the lateral deformation range is 2 times,and the micro-pile and the pouring pile cause the deformation range of the adjacent soil to be within 5 m.The pile foundation piles were used to strengthen the foundation of the Lunan high speed railway subgrade section.The maximum outward displacement of the foot monitoring points of the subgrade is within 1.0 mm,which indicates that the existing subgrade is basically not affected by construction disturbance.