环端面不平整条件下衬砌管片抗剪承载特性研究

On the shearing capacity characteristics of lining segment with uneven ring surface condition

在衬砌管片拼装过程中难免出现环端面不平整(或环缝间垫片局部脱空)的情形,进而在顶推力作用下管片容易产生局部开裂破损,严重时甚至危及衬砌结构安全。鉴于此,以衬砌管片抗剪原型试验为基础,在ABAQUS数值分析平台上建立P2型标准块管片的精细化模型,管片上部设置千斤顶靴板,底部设置垫片并使右侧垫片脱空。在靴板上逐级施加均布荷载,以分析局部脱空情况下衬砌管片在逐级顶推力作用下的力学响应,探讨环端面不平整条件下衬砌管片的裂缝发展过程及抗剪承载特性。数值模拟结果表明:顶推力加载至850 kN,管片脱空端竖向位移达到2 mm,管片内弧面上部出现第1道裂缝,内置钢筋仍处于弹性阶段;加载至1120 kN,脱空端竖向位移达到6 mm,内弧面上出现2道新裂缝,同时第1道裂缝进一步扩展形成内外贯穿性裂缝,即管片裂缝发展过程大致为内弧面→上环端面→外弧面,且裂缝附近上层纵向钢筋达到屈服强度;考虑到内外贯穿裂缝给衬砌管片带来较大渗漏水隐患,认为P2型标准块管片的抗剪承载力(即屈服荷载)约为1120 kN。将数值模拟结果与原型试验结果进行对比,二者所得管片裂缝分布与扩展规律大致一致,抗剪承载力基本相符,验证了数值模拟结果的可靠性。研究成果可为盾构隧道的衬砌设计与掘进施工提供参考依据。

The unevenness of ring faces(or the local gaps due to gaskets)is inevitable during the assembling of lining segments,which could cause the cracking or damage of segments and might endanger the safety of lining structure in severe cases.Based on the shear resistance prototype test of lining segment,the refined numerical simulation for the P2-typed standard segment was established upon the ABAQUS numerical platform.The jacking plates were placed on the top of segment,the gaskets are placed at the bottom of segment,and the right gasket was left empty to form a local gap.The uniform load was gradually applied upon the top of segment through jacking plates.The mechanical responses of the segment with local void condition were analyzed under the gradual action of jacking force.The cracking process and the shearing capacity of segment with uneven ring face condition were well focused on.The simulation results show that the 1st crack appears on the upper part of segment inner surface with 2 mm under the jacking force of 850 kN.When the jacking force increases to 1120 kN,the vertical displacement of the segment bottom reaches 6 mm.Another two new cracks appear on the segment inner surface,and the 1st crack further expands to the outer surface and develops into the penetrating cracks.The cracking process of the segment is described sequentially as inner surface→upper ring surface→outer surface.Considering the potential risk of leakage of water caused by penetrating cracks,the shear capacity(yield load)of P2-typed standard segment was determined to be approximately 1120 kN.Comparing the numerical simulation results with the prototype test,the cracking expansion,the distribution pattern and the shearing capacity obtained from both two means were almost consistent,which implies the reliability of numerical simulation.These results can provide reference for the design and construction of shield tunnel.