• Geomechanics and Engineering
• /
• v.39 no.4
• /
• pp.369-383
• /
• 2024

The construction of the shield tunnel results in the deformation of the surrounding soil and the existing pipeline. It is important to analyze the deformation of the existing pipeline during the excavation of the tunnel. Based on the two-stage analysis method, the shear effect of pipeline due to the uneven settlement was considered and the deformation and internal force of existing pipeline due to the tunnel excavation were studied. The theoretical formulas were verified by the in-site monitoring. Compared with the theoretical calculation, the three-dimensional numerical simulation was established to simulate the deformation of the existing pipeline and the ground surface during the tunnelling. The effect of the Poisson's ratio, the tunnel diameter and the pipeline shading on the deformation of the existing pipeline were further investigated. The results show that the deformation curves of the pipeline and the ground surface conform to the Gaussian distribution, and the position above the axis of the tunnel experiences the maximum. When the excavation surface of tunnel crosses underneath the pipeline, the pipeline and the ground surface experience larger deformation and more subsidence, respectively. A certain amount of uplift is generated for the pipeline and the ground surface at ± 20 m away from the center line of the tunnel. The deformation of existing pipelines is affected by the tunnel excavation within its diameter range. The results can provide a reference for the design and construction of the shield tunnel underpass.

• Journal of the Korean Geotechnical Society
• /
• v.32 no.6
• /
• pp.17-26
• /
• 2016

Characteristic behaviors of geo-structure during freezing and thawing process have to be understood based on fundamental knowledge on phase change in porous soil and interaction between soil and structure. Inversion analysis using published one-dimensional soil freezing tests was conducted to suggest a mechanical model to consider an effect of the ice saturation on Young's modulus. Silty soil was more sensitive to temperature than weathered granite soil and sand, and weathered granite soil was more affected by initial water saturation in stiffness decrease than silty soil. Numerical simulations on chilled gas pipeline showed that shielding effect from surrounding frozen zone around the pipe decreases impact from external load onto the pipe. And a pipe installed in sand backfill showed more heaving due to relatively low stiffness of sand during freezing than that of surrounding in-situ weather granite soil. However, it had more stable stress condition due to effective stress redistribution from external load.