考虑土拱效应作用程度的管片总上浮量计算研究

Research on the Calculation of the Total Floating Amount of Segment Considering the Degree of Soil Arching Effect

针对泥水盾构施工过程常遇到的管片上浮问题,基于南昌地铁4号线(安丰站-东新站)区间泥水盾构过江隧道工程,对管片上浮量进行理论计算。将管片上浮分为浆液初凝前与浆液初凝后两个阶段,首先分析浆液初凝前管片受力组成,其中在计算上覆土作用力时,采用考虑土拱效应作用程度的改进Terzaghi松动土压力计算式,进而推导浆液初凝前管片上浮理论解,并在此基础上提出浆液初凝前上浮影响系数;其次分析浆液初凝后管片受力情况,采用地基沉降的弹性力学公式计算上覆土层压缩量,得到浆液初凝后管片上浮计算表达式;最后依据现场实测数据验证理论解的吻合度。结果表明:(1)分阶段累计计算得到的管片上浮量与现场实测值吻合较好,管片发生上浮会经历两个阶段,其中浆液初凝前出现的管片上浮量占据主导地位;(2)浆液初凝前上浮影响系数Γ可以较好地反映土拱效应作用程度对浆液初凝前管片上浮计算的影响情况,当考虑土拱效应作用程度时计算值会更接近实测值。

Aiming at the segment floating problem often encountered in the construction of slurry shield,based on the slurry shield river crossing tunnel project of Nanchang Metro Line 4(Anfeng Station to Dongxin Station),the segment floating is theoretically calculated.The segment floating is divided into two stages before and after the initial setting of slurry.Firstly,the stress composition of segment before the initial setting of slurry is analyzed,in which when calculating the force of overlying soil,the improved Terzaghi loose earth pressure calculation formula considering the action degree of soil arching effect is adopted,and then the theoretical solution of segment floating before the slurry reaches the initial setting is established.On this basis,the influence coefficient of slurry floating before the initial setting is proposed.Then,the stress of the segment after the initial setting of the slurry is analyzed,and the compression of the overlying soil layer is calculated by using the elastic mechanics formula of foundation settlement,and the calculation expression of segment floating after the initial setting of the slurry is obtained.Finally,the coincidence degree of the theoretical solution is verified according to the field measured data.The results show that:(1)the segment floating amount calculated by stages is in good agreement with the field measured value.The segment floating will go through two stages,in which the segment floating amount before the initial setting of slurry is dominant;(2)the influence coefficientΓof slurry floating before initial setting can better reflect the influence of the action degree of soil arching effect on the calculation of segment floating before the initial setting of slurry.When the action degree of soil arching effect is considered,the calculated value will be closer to the measured value.