Study of analytical method of adjacent pipeline deformation considering the deformation of deep foundation pit supporting structure

Deep foundation pit excavation significantly impacts the horizontal deformation of adjacent underground pipelines. First, considering the effect of lateral displacement of the flexible support structure on the slack stress distribution of the pit sidewall unloading, the existing sidewall unloading mechanical calculation model was improved, and the additional horizontal stress of the adjacent pipeline caused by the pit excavation unloading was calculated using the Mindlin solution. On this basis, the horizontal deformation equation of the pipeline was established based on the Pasternak foundation model, the influence of the lateral unloading stress path on the value of the Pasternak model parameters was analyzed, the analytical solution of the horizontal deformation of the pipeline was obtained, and the calculated results were compared with the actual engineering monitoring data. Finally, the influence of three parameters, the distance between the foundation pit and the pipeline, the buried depth of the pipeline and the lateral unloading modulus of the soil, on the horizontal deformation of the pipeline was analyzed in detail. The results show that the calculated results are consistent with the monitoring data. The horizontal deformation curve of the pipeline is an inflection point near 2H from the edge of the pit, and the horizontal deformation decreases rapidly. Almost no horizontal deformation when the pipeline is longitudinally beyond the excavation range 2H of the foundation pit. The horizontal deformation of the pipeline near the corner of the pit is 0.5-0.6 times the maximum horizontal deformation. The distance between the pit and the pipeline significantly influences the pipeline's maximum horizontal deformation value, and the pipeline's maximum horizontal deformation value shows a non-linear decrease with the increase of the distance of "first sharp then slow". In the range of 0.5-1 for the ratio of the distance from the enclosure structure to the depth of the pit, the maximum horizontal deformation of the pipeline gradually decreases with the increase of the burial depth of the pipeline and the lateral unloading modulus of the soil body. © 2023, Editorial Board of Journal of CUMT. All right reserved.