穿越施工中管线与土层共同变形规律分析

研究目的:为了解穿越工程中管线与土层的共同变形规律,建立管-土相互作用三维有限元模型,分析土体及管线刚度、新建隧道直径、管线与隧道净距对管线沉降和内力的影响。研究管线沉降和弯矩随管土刚度系数K的变化规律,提出柔性管线、弹性管线和刚性管线的管土刚度系数K判定值,给出管线最大弯矩和最大沉降的简便计算公式。进行室内离心模型试验及现场实测,将管线监测数据与数值模拟进行对比研究。研究结论:(1)管线沉降和弯矩均随管土刚度系数K的增大而减小;(2)当K<0.1时,管线为柔性管线,管线与土层能够协同变形不产生脱空,此情况下可把土层沉降当作管线沉降来计算管线内力;(3)当K>100时,管线为刚性管线,管线很容易与土层产生脱空,可采用土层反力作为荷载来计算管线内力;(4)当0.1≤K≤100时,管线为弹性管线,可能与土层产生脱空,宜通过考虑管土分离的有限元模型进行其受力分析;(5)本研究成果可为隧道施工中既有管线的安全评价提供理论依据。

Analysis of Co-deformation Law between Pipelines and Soil due to Traversing Construction

Research purposes:In order to understand the co-deformation law between pipeline and soil,a three-dimensional finite element model considering pipe-soil interaction was established.Influences of rigidity of soil and pipeline,diameter of the newly built tunnel,vertical net distance of tunnel and pipeline on displacement and internal forces of the pipeline were analyzed.Variation laws of settlement and bending moment of the pipeline with respect to the relative pipe-soil rigidity factor(K)were studied.It is recognized that the pipeline can be categorized as flexible pipeline,elastic pipeline and rigid pipeline according to the factor K.Simple formulae to compute the maximum bending moment and the maximum settlement of pipelines were given.Centrifugal model test and in-situ measurement were conducted,results from which were compared with that by numerical simulation.Research conclusions:(1)Settlement and bending moment of the pipeline decrease with the increase of the factor K.(2)A pipeline with K<0.1 is a flexible one which deforms as much as what the soil settles with no detachment occurring between them.The settlement of the soil can be taken as that of the pipeline and the internal forces of the pipeline can be calculated.(3)A pipeline with K>100 is a rigid one which refuses to deform with the soil with detachment easily occurring between them.Resistance of the soil on the pipeline can be found out and used to compute the internal forces of the pipeline.(4)A pipeline with 0.1≤K≤100 is an elastic one which obviously interact with the soil with detachment possibly occurring between them.The proposed numerical model in this paper,which takes into account the detachment between the pipeline and the soil,is suitable to be employed for the computation of the mechanical behavior of the pipeline.(5)The research results can provide theoretical guidance for safety evaluation of the existing pipelines during traversing construction.