深埋不同水头条件下TBM管片结构力学特性与结构设计

摘要

通过使用ANSYS梁-弹簧模型,结合某大直径深埋TBM公路隧道管片设计,对不同高度水头下管片结构力学特性进行分析.得到随着水头高度的增加,管片结构的力学特性主要分为4个阶段.第一阶段为拱顶受拉控制.水头高度为0～1D,安全系数逐渐减小;第二阶段仍然为拱顶受拉控制.水头高度为1D～2D,安全系数逐渐增加;第三个阶段为拱顶受拉转变为拱脚受压控制.水头高度为2D～4D,安全系数逐渐减小;第四阶段属于管片环拱腰位置受压控制.水头高度大于4D,安全系数继续减小直到管片破坏.通过研究管片厚度、混凝土强度等级、配筋量3个设计因素对管片水头承载能力的影响,提出不同水头高度条件下的分段设计方法:管片处于第一和第二阶段时,增加管片配筋量和管片厚度能显著提高结构安全性;管片处于第三和第四阶段时,提高管片厚度和混凝土强度等级能显著提高管片安全系数和最终的水头承载能力.%By using ANSYS beam-spring model and with reference to a large-diameter deep TBM highway tunnel segments design,the mechanical properties of the segment under different water pressure are analyzed.With the increase of water pressure,the mechanical properties of segments are divided into four stages.The first stage is the dome tension control,the water pressure height is 0 ～ 1D and the safety factor is gradually reduced.The second stage is still the dome tension control,the height of water pressure is 1D ～2D and the safety factor is gradually increased.The third stage is the transition from arched vault to arch foot pressure control,the height of water pressure is 2D ～ 4D and the safety factor is gradually reduced.The fourth stage is the compression of the arch position,the height of the water pressure is greater than 4D and the safety factor continues to decrease until the segment is damaged.Through the study of the influence of the thickness of the segment,the concrete strength grade and the reinforcement amount on the hydraulic bearing capacity of the segment,segmentation design method under different water pressure is proposed.Increasing the reinforcement quantity and the thickness of the segment in the first and second stages can significantly improve structural safety;increasing segment thickness and concrete strength in the third and fourth stages can significantly improve segment safety and final water head bearing capacity.