土压平衡矩形顶管正面附加推力对地表隆起变形影响研究

Study on the effect of positive additional thrust on the surface uplift deformation by the construction of the rectangular pipe jacking with earth pressure balance

以全国最长的大截面矩形顶管综合管廊工程为背景,基于弹性力学Mindlin解和随机介质理论,分析顶管施工对地表隆起变形的影响.研究发现:地表隆起过程可分为四个阶段,分别为缓慢隆起阶段、快速隆起阶段、沉降阶段和稳定阶段,并得到地表隆起超限主要集中在快速隆起阶段,该阶段地表快速隆起变形的主要诱因是正面附加推力,其次为顶管机摩擦力和后续管节摩擦力;刀盘挤土压力对正面附加推力影响很大,基于弹性力学Kelvin解,并引入刀盘转速比,得到大、小刀盘转速比在0~0.2范围内时对刀盘挤土压力影响很大;基于进出土平衡理论,并引入螺旋机转速比,得到它对刀盘开口处土压力影响很小,但顶进速度对刀盘开口处土压力影响很大;综合各因素得知,在矩形顶管施工参数中,刀盘转速比和顶进速度对正面附加推力影响很大,是造成地表隆起变形的主要原因.

This paper study the influence of top pipe construction on ground surface uplift deformation,which is based upon Elastic mechanics Mindlin solution and stochastic medium theory,and the nation's longest large-section rectangular pipe jacking utility project.The process of surface uplift deformation can be divided for four stages,including slow uplift stage,rapid uplift stage,subsidence stage and stabilization stage.The transfinite surface uplift deformation mainly focus on the rapid uplift stage that main inducement is the positive additional thrust,and second inducement is the pipe jacking friction and following pipe joint friction.It is a large influence element for the pressure on the cutter to squeeze the soil to the proportion of big and small cutter rotate speed when it's range from 0 to 0.2,based on elastic mechanics Kelvin solution.Based on the theory of in and out soil balance,we bring in the proportion of screw machine rotate speed,it is a small influence element for the earth pressure at cutter opening,but speed of pipe jacking machine is a large influence element for it.To conclusion,the proportion of cutter rotate speed and speed of pipe jacking are a large influence element for the positive additional thrust,and then for the surface uplift deformation.