盾构隧道开挖面支护压力控制不当将诱发地层位移,进而威胁邻近地下管线正常运营和安全。既有研究重点讨论了隧道施工引起的土体小变形对上覆管线影响,开挖面失稳时地下管线变形特性研究甚少。开展物理模型试验,研究了隧道埋深比(C/D)和管线-开挖面水平净距(H/D)对地下管线变形特性影响。结果表明:管线与开挖面水平距离为0.1D(隧道直径)时,开挖面失稳引起的管线沉降最大;管线-开挖面水平净距(H/D)从0.1增至0.5,管线最大沉降和最大弯曲应变降幅分别高达64.8%和51.6%;隧道埋深比(C/D)从1.0增至1.5,管线沉降和弯曲应变最大降幅分别为14.9%和7.3%,表明管线-开挖面水平净距是控制地下管线变形的关键参数。基于系统的有限元数值模拟,提出了管线沉降比和管线-土体相对刚度无量纲组,建立了开挖面主动失稳下地下管线最大沉降预测方法,并利用试验数据验证了预测方法的合理性。
Improper control of supporting face pressure of shield tunnel may induce excessive ground movements, which may threaten the serviceably and safety of adjacent underground pipelines. Currently, extensive studies have been conducted to investigate pipeline responses due to tunnelling under various volume loss, effects of active face instability on deformation characteristics of existing pipelines are rarely explored. Physical model tests are conducted to investigate the effects of tunnel cover to diameter ratio (C/D) and normalized horizontal distance (H/D) between tunnel face and existing pipeline on three-dimensional pipeline deformation mechanisms. The results show that: When the pipeline is located 0.1D away from the tunnel face (i.e., H/D = 0.1), active face instability induced pipeline settlement reaches the maximum value. By increasing H/D ratio from 0.1 to 0.5, the maximum settlement and bending strain of pipelines are reduced by up to 64.8% and 51.6%, respectively, while the respective maximum reductions in the pipeline settlement and bending strain are only 14.9% and 7.3% as the C/D ratio from 1.0 to 1.5. It is indicated that H/D ratio is the key parameter to control pipeline settlement. Based on systematic numerical parametric analyses, calculation charts for estimating pipeline settlements due to tunnel active face instability are established by using two dimensionless groups of pipeline settlement ratio and relative pipeline-soil stiffness. The validity of the proposed calculation charts is verified by the physical test results, and the calculation charts can provide a rapid evaluation of pipeline safety and adjustment of supporting face pressure during tunnel construction.
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