新建地铁与既有线交叠区域地基处理加固分析

Analysis of Foundation Treatment and Reinforcement for Overlapping Areas of New Subway and Existing Subway Lines

沈阳地铁10号线盾构区间超小净距上穿既有地铁2号线区间人防段,为研究地铁施工对既有结构产生的影响,探讨交叠区域采取注浆加固措施后的效果,确保盾构区间顺利完成穿越。利用ABAQUS有限元软件建立交叠区域地基一定范围内土体深孔注浆预加固三维模型,研究新建隧道盾壳与既有暗挖结构点接触对既有结构及管片结构内力的影响。研究结果表明:新建地铁若与既有2号线区间发生点接触,接触点位置会出现集中荷载,对既有结构受力不利;交叠区域地基进行注浆预加固后,既有结构拱顶所受弯矩较未注浆加固时减小约5/6,地基处理效果明显,这是由于盾壳与周围土体刚度差异减小,周围土体可承担更多竖向荷载;新建地铁管片弯矩值降低为未注浆加固时1/5左右,裂缝宽度由0.08 mm降低为0.05 mm,注浆加固一定程度上具有改善管片环向受力状态的作用。分析结果证明了加固方案的合理性。

In order to study influences of subway constructed over the existing subway structure and effects of grouting reinforcement measures for overlapping areas,the shield section of Shenyang Metro Line 10 crosses over the existing civil air defense section with ultra-small clear distance is analyzed. ABAQUS finite element software is used to establish a 3D model of soil deep-hole grouting pre-reinforcement within a certain range of the overlapping area. Influences of the contact point between the newly built tunnel shield and the existing excavated structure on the internal force of the existing structure are discussed. The results show that if point contact appears when the new subway line crosses over the section of the existing line 2,concentrated load will appear at the point of contact which is unfavorable to the existing structure. After grouting pre-reinforcement in the overlapping area,the bending moment of arch roof of the existing structure is about 5/6 less than that of the non-grouting reinforcement,and the foundation treatment effect is significant. The reason is the stiffness difference between the shield and the surrounding soil is reduced which increases the vertical load carrying capacity for soil. When the bending moment value of newly-built subway shield segment is reduced to about 1/5 without grouting reinforcement, the crack width is reduced from 0. 08 mm to 0. 05 mm. Grouting reinforcement can improve the annular force state of the shield segment to some extent. The analysis results prove the rationality of the reinforcement scheme.