主动区土体加固对深基坑变形及周边环境的影响

Effects of Reinforcement of Soil in Active Zone on Deformation and Surrounding Environment of Deep Foundation Pit

为减小基坑变形和保护周边环境,采用高压旋喷桩对基坑主动区加固,采用土体卸载条件下的修正摩尔库伦有限元模型,分析深基坑开挖过程中主动区加固体强度对深基坑变形及周边环境的影响。数值模拟结果表明,主动区土体加固能抑制基坑及周边环境的变形,支护结构水平位移、地表沉降、建筑物不均沉降随着加固强度的增大而减小;经加固后,桩体最大水平位移位置在桩顶,最终减小水平位移达87%;主动区加固会使坑后土体产生“上拱”现象,地表沉降曲线由加固前的“凹槽型”变为“上拱型”;不均匀沉降是评价建筑物安全的重要指标之一,增加加固体强度对初期开挖的建筑物不均匀沉降无显著影响,但能减小最后一步开挖工况下建筑不均匀沉降达90%。因此,主动区加固不仅可以和被动区加固一样抑制基坑变形,同时可以保护临近建筑物安全。

In order to reduce the deformation of the pit and protect the surrounding environment,the high-pressure rotary piles were used to reinforce the active zone of the pit,and the modified Moore-Coulomb finite element model under the soil unloading condition was adopted to analyze the influence of the reinforcement strength of the active zone on the deformation of the deep foundation pit and the surrounding environment during the excavation of the deep foundation pit.The numerical simulation results showed that:the active zone soil reinforcement was able to suppress the deformation of the pit and the surrounding environment;the horizontal displacement of the support structure,surface settlement and uneven settlement of the building decreased with the increase of reinforcement strength.After reinforcement,the maximum horizontal displacement of the pile body was at the top of the pile,and the horizontal displacement was finally reduced by 87%.The active zone reinforcement would cause the soil behind the pit to"arch up",and the surface settlement curve would change from"groove type"before reinforcement to"arch up".Uneven settlement is one of the important indicators to evaluate the safety of buildings,therefore,the active zone reinforcement can not only suppress the deformation of the foundation pit as the passive zone reinforcement,but also protect the safety of the adjacent buildings.