The influence of excavation of vertically parallel twin tunnels on the deformation of nearby pile groups
In order to investigate the general principles governing the deformation of nearby pile groups induced by the construction of vertically parallel shield tunnels in sandy soil layers,this study utilizes centrifuge model tests and establishes a three-dimensional numerical model using PLAXIS3D for the excavation of vertically parallel twin circular tunnels adjacent to existing pile groups.By comparing the numerical model with the measured results from centrifuge model tests,the model's validity is confirmed,and the influence of soil parameters,tunnel dimensions,and pile foundation dimensions on pile settlement and tilt is investigated.The research findings indicate that the settlement and tilt of pile groups induced by tunnel excavation increase with the increase of soil modulus,ground loss rate,and tunnel diameter,while decreasing with the increase of pile length.Furthermore,when the lower tunnel is situated directly beneath the pile group,pile settlement is significantly influenced by soil modulus,ground loss rate,tunnel diameter,and pile length.When the lower tunnel is located at the level of the pile group toe,pile tilt is primarily affected by soil modulus,ground loss rate,and pile length.Pile settlement ceases to increase when the soil modulus exceeds 35 MPa,and pile tilt slows down noticeably when the soil modulus exceeds 20 MPa.Pile settlement remains relatively stable when both tunnels are located on one side of the pile group and the pile length exceeds 35 m.Moreover,when the second tunnel is positioned directly beneath the pile group,the change in pile settlement and tilt decreases significantly when the pile length exceeds 45 m.
numerical simulationinfluence factor analysisvertically parallel twin circular tunnelspile groups
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