Integrated Numerical Assessment of Canal Embankment Stability and Buried Gas Pipeline Integrity

Buried gas pipelines crossing irrigation canals are critical infrastructure that may be affected by canal rehabilitation, embankment instability, ground deformation, and fluctuating hydraulic conditions. This study presents a sequential numerical assessment framework integrating slope stability, ground deformation, soil–pipeline interaction, and hydraulic erosion analysis for an existing buried gas pipeline beneath the Rapeephat Canal in Thailand, which was recently widened to increase irrigation capacity. Two- and three-dimensional finite element analyses were conducted under three hydraulic conditions: maximum water level, minimum water level, and rapid drawdown. The existing embankment exhibited inadequate stability, with factors of safety ranging from 0.51 to 1.42. Following stabilization with a concrete face slab, the factors of safety increased to between 1.50 and 1.73, exceeding the adopted criterion of 1.50 under the investigated conditions. The maximum calculated ground settlement was 13.58 mm, while the maximum pipeline displacement under the normal operating pressure of 4.52 MPa was 10.10 mm. The maximum PLAXIS-derived bending stress was 0.088 MPa, whereas a supplementary hoop-plus-bending stress check indicated an equivalent combined stress range of approximately 116–145 MPa under the normal operating pressure, remaining below the adopted stress criterion based on 90% of the specified minimum yield strength. The maximum calculated boundary shear stress was 6.41 N/m2, below the adopted permissible value of approximately 12 N/m2 for stiff clay. The results demonstrate the influence of canal modification and hydraulic conditions on embankment stability, ground deformation, and pipeline response. The framework provides a practical approach for assessing existing pipeline–canal crossings, while the results should be interpreted within the adopted modeling assumptions and the limitations of the available field data and sequential coupling approach.