软土地区钢套管钻孔灌注桩施工对临近高铁路基变形影响研究

Influence of developed Benoto piling on deformation of adjacent high-speed railway subgrade in soft soil area

新建连镇铁路采用桩板结构形式接轨沪宁城际,受运营高铁触网高度限制,工程研发了新型超低净空成桩设备及配套工法施作紧邻运营高铁钢套管钻孔灌注桩。为探明钢套管钻孔灌注桩施工对周围地层及既有高铁路基的变形影响,采用现场实测结合数值分析的方法开展研究。首先,通过在现场试验中布设地层水平位移监测点,获取成桩施工中桩周地层变形演变规律。其后,建立钢套管桩−地层−高铁路基有限元模型,计算获得群桩施工引起的既有高铁路基变形,并围绕群桩施工顺序、施工安全距离及辅助变形控制措施等展开讨论。研究结果表明:钢套管钻孔灌注桩施工对桩周地层的影响总体呈现为横向挤压变形,成桩施工各工序中钢套管旋进过程对桩周地层扰动最为显著,钢套筒深度范围内地层会出现明显的水平向位移变形。通过现场试验与有限元模拟相结合的方法可得到本接轨工程中钢套管钻孔灌注桩施工安全距离,当群桩施工区与既有路基间距不能满足施工安全距离要求时,可布设钢板桩辅助控制路基变形,钢板桩的变形控制效果与钢板桩长度正相关,与钢板桩距施工桩的距离呈负相关。本研究可为更好地满足高铁变形控制要求提供思路及建议。

A new constructed high-speed railway line between Lianyungang and Zhenjiang with pile-plank supported subgrade will be emerged into the existing high-speed railway line between Shanghai and Nanjing.To meet the requirements of height limitation of the high-speed railway catenary,a new type of height-limited piling equipment and corresponding piling technologies for developed Benoto piles adjacent to high-speed railways were proposed in this project.To reveal the influence of Benoto piling on the deformation of surrounding strata and adjacent high-speed railway subgrade,this paper adopted field tests combined with numerical analysis.In the field tests,displacement monitoring devices were used to monitor the horizontal deformation of strata during piling.Then,Benoto pile-strata-subgrade finite element model was established for calculating the deformation of high-speed railway subgrade during group piles construction.The construction sequence of group piles,construction safety distance and auxiliary deformation control measures were discussed based on this numerical model.The results indicated that the developed Benoto piling generally leads to transverse extrusion deformation of surrounding strata.In each process of piling,the steel casing construction induces the most significant disturbance to surrounding strata.The strata,especially those within the length of steel casing,show obvious horizontal displacement.The construction safety distance of Benoto piling adjacent to high-speed railway can be determined by field tests and numerical simulations.When the distance between the piling region and the existing subgrade cannot meet the critical construction safety distance,the steel sheet piles can assist to control subgrade deformation.The deformation control effect of steel sheet piles on subgrade is positively related to the pile length and negatively related to the distance from the piling region.The results can provide suggestions for the deformation control of existing high-speed railway to ensure its safe operation.