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| Model tests on settlement of buried pipeline based on fiber optic monitoring |
| LI Haojie，ZHU Honghu，ZHU Bao，WU Haiying，LIU Zhengyuan，SHI bin |
| (School of Earth Sciences and Engineering，Nanjing University，Nanjing，Jiangsu 210023，China) |
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Abstract Based on distributed fiber optic sensing technology，this paper proposes a refined scheme for the deformation and stress monitoring of buried pipelines. The spatial and temporal distribution characteristics of axial forces，shear forces and bending moments of buried pipelines，evolution of earth pressure and shear stress on the soil-pipe interface were experimentally studied. In this paper，a simplified model for calculating pipeline settlements based on the strain measurements of optical fibers was established. An ellipticity function was introduced to quantitatively evaluate the circumferential deformation of pipeline cross sections. The results show that：(1) The spatial distribution of the settlement of the pipeline conforms to the modified Gaussian curve. Maximum errors in settlement calculation based on the quadratic integration method and the conjugate beam method are 13.1% and 4.2%，respectively. (2) The maximum deformation along circumferential direction of the pipeline occurs in its middle. Compared with bending deformation，the magnitude of circumferential deformation is relatively low，with a maximum ovality value of 1%. (3) When settlement occurs，earth pressures at the pipe bottom dissipates rapidly. Whereas，earth pressures at crown first increase rapidly and then gradually stabilize. Earth pressures on pipe sides continue to increase during settling. (4) The shear stress distribution curve on the soil-pipe interface is center-symmetric. The pipe-soil interaction is classified into two classes：strong-shearing type and weak-shearing type based on the characteristics of the shear stress.
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2020, Vol. 39 
