摘要
软土地区CFG桩施工,桩顶以上部分空桩孔不及时回填会造成群孔效应。通过单孔和群孔效应数值模拟,并加以工程实测分析,初步得到了群孔效应引发周边土体变形机理。土体变形由空桩孔孔壁内缩引起,并在竖向和水平向应力拱的作用下达到稳定状态。单孔孔壁变形最大值和最大值位置主要受孔深影响。多孔共存孔心距较小时,周边土体水平和竖向应力拱相互影响削弱导致每个空孔的内缩变形均大于单孔时的变形值,这是群孔效应引发周边土体变形严重的主要原因。随孔数增多,周边土体的竖向和水平向变形均增大,最大变形值位置与地表间距离减小。孔数超过400后,最大值位置位于地表。孔底标高以上且距群孔边界2倍孔深以内的区域为群孔效应的主要影响区。
The hollow boreholes above pile head,which are usually left unbackfilled in the soil strata during the construction of CFG piles,could lead to the borehole group effect in soft soil area.The mechanism for the borehole group effect causing the deformation of surrounding soil is investigated through a series of simulations of single hole or group holes and the analysis of an engineering case.The soil deformation is caused by the shrinkage of the borehole wall and reaches a steady state under the action of the horizontal and vertical stress arching.For the single borehole,the maximum deformation value and the distance between the maximum value position and ground surface are mainly influenced by the hole depth.For the borehole group,the shrinkage of each hollow borehole becomes greater than that of the single hole because the horizontal and vertical stress arching surrounding each hole will influence and destroy each other when the hole center distance is relatively small.This should be the important mechanism for the borehole group effect.As the hole number increases,the maximum settlement and horizontal displacement in the soil increases,but the distance between the maximum value position and the ground surface decreases.The maximum value position moves to the ground surface when the hole number is greater than 400.The zone above the elevation of the hole bottom as well as within the horizontal distance of twice the hole depth is the main influence zone of the borehole group effect.
出处
《石家庄铁道大学学报（自然科学版）》
2018年第1期39-46,54,共9页
Journal of Shijiazhuang Tiedao University(Natural Science Edition)
基金
国家自然科学基金(51508382
41630641)
中国博士后科学基金(2014M561186)
关键词
CFG桩
群孔
软土
土体变形
CFG Piles
borehole group
soft soil
soil deformation
