湿陷性黄土地层盾构隧道施工力学响应及局部湿陷性影响分析——以太原地铁一号线为例

    ANALYSIS OF THE MECHANICAL RESPONSE DURING SHIELD TUNNEL CONSTRUCTION IN COLLAPSIBLE LOESS STRATUM AND THE INFLUENCE OF LOCAL COLLAPSIBILITY: A CASE STUDY OF TAIYUAN METRO LINE 1

    • 摘要: 湿陷性黄土地层隧道盾构施工过程及局部湿陷性对土层及盾构管片影响的研究对保证隧道施工和后期运营安全至关重要。本文依托太原地铁一号线工程,利用有限元软件动态模拟盾构掘进施工过程,并与现场监测数据进行了对比分析,验证了本文建立数值模型的有效性。数值分析表明,盾构掘进过程中隧道周围土层内力大小及分布规律均未发生明显改变,只在隧道顶部及底部出现轻微应力集中。根据不同施工步隧道应力分布,应重点监测盾构施工中开挖面前后3.6 m范围内隧道顶部沉降、底部隆起及隧道正上方地表沉降。在黄土湿陷对隧道管片影响分析中采用了密模修正法,通过对土体发生湿陷变形后的密度和弹性模量进行修正,利用有限元属性转换模块实现湿陷性的表征。经动态数值模拟分析,盾构掘进导致隧道上方水平方向18 m范围内土体发生“U”形位移,地表最大沉降6.97 mm;局部湿陷变形(4.8 m×12.4 m)引起管片环向弯矩增幅最大为4.25%,影响范围局限于湿陷区前后2~3环管片,变形增量1.01 mm,表明湿陷性对管片受力及变形的影响较小。本文针对盾构掘进及局部湿陷对地层与管片的力学响应规律研究可为黄土地区盾构隧道设计、支护参数优化及风险监测提供参考。

       

      Abstract: The analysis of shield construction in collapsible loess strata and the impact of local collapsibility on surrounding soil and shield segments is vital for ensuring the safety of tunnel construction and metro operation. Based on the Taiyuan Metro Line 1 project, this paper dynamically simulated the shield tunneling construction process using finite element software, and the numerical model was validated through comparative analysis with on-site monitoring data. The numerical analysis showed that the internal forces of the soil around the tunnel did not change significantly during shield excavation, with only slight stress concentration appearing at the top and bottom of the tunnel. According to the stress distribution during tunnel excavation, top settlement, bottom uplift, and surface settlement directly above the tunnel should be monitored within a 3.6 m range before and after excavation during shield construction. In the analysis of the influence of loess collapsibility on tunnel segments, the dense modulus correction method was employed to modify the density and elastic modulus of the loess after collapsible deformation, with collapsibility characterized through finite element property conversion modules. Dynamic numerical simulation results revealed that shield excavation induced a "U"-shaped soil displacement within 18 m horizontally above the tunnel, with a maximum surface settlement of 6.97 mm. Local collapsible deformation (4.8 m×12.4 m) caused a maximum increase of 4.25% in the circumferential bending moment of shield segments, with the influence range limited to 2~3 adjacent rings and a deformation increment of 1.01 mm, indicating that collapsibility had relatively minor mechanical impacts on the shield segments. This research on the mechanical response mechanisms of shield tunneling and local collapsibility provides valuable references for shield tunnel design, support parameter optimization, and risk monitoring in loess regions.

       

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