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utilized CAESAR II software to investigate the stress on underground oil pipelines in steep and high slope regions. However, this study was not extended to stress analysis of deeply buried HDD pipelines. It was concluded that reducing the bend angle could minimize the stress and displacement of underground pipelines during an earthquake. Hence, critical sections and maximum stress region were identified visibly. to undertake dynamic earthquake analysis on oil pipelines using CAESAR II stress analysis software. Spectrum technique with 1D beam units was used by Wu et al. Its application ranges from the study of aircraft or automobile structural framework, complicated thermal system (nuclear power plant), to the analysis of a fluid flowing through a duct, over a weir, or through the earth developed a 3D FE program using MATLAB to examine the performance of buried pipeline subjected to large ground motion crossing active fault. The results more reasonably reflect the actual situation, providing an improved design procedure to avoid pipe wear and breakage. In the analysis and design of underground structures, the finite element method (FEM) has been used extensively as an effective numerical technique. Finite Element Method (FEM) for Pipeline Stress Analysis These two factors should be considered together to ensure that the pipeline can be installed and operated without risk of damage. The borehole profile and pipe properties must be considered in selecting the suitable pipe materials for an HDD installation. Drilled path design and pipe specification may be governed by these installation loads, as they could be more severe than operational loads. HDD pipelines are subjected to a combination of tension, bending, and external pressure. The depth of embedment of pipe, type of backfill, the pipe thickness and surcharge loads are the prime factors that affect the behavior of buried pipes. Then, there is the additional force caused by ground loads which decreases with increase in depth of cover. Firstly, there is the soil pressure which increases with the depth of cover. Underground loads on a buried pipeline induced by the soil pressure can be divided into two parts. The loads acting on the pipe include its weight, the internal operating pressure and the external pressure due to the overhead soil load. The cross sectional area validation showed a percentage difference of 0.059%. The model stress validation performed by comparing results with theoretical solutions, both with respect to radius of curvature and internal pressure, showed percentage difference (errors) less than 10%. The maximum stress occurred at the curvature point with the highest entry angle (10 °), resulting in a maximum deflection at this point. The results showed that the maximum and minimum stresses induced on the HDD pipeline were at the top and bottom of the pipe, respectively while the stresses on the sides were uniform (≈888 kg/cm 2 ) all through the pipeline, irrespective of element number.
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A macro-file for ANSYS Version 18, mechanical APDL used to model the pipeline was developed. The pipeline used as the case study was a gas transmission pipeline installed in south-west Nigeria. This study analyses the stress induced on an HDD pipeline system using the ANSYS Version 18, mechanical APDL finite element (FE) software. In designing a horizontal directional drilling (HDD) pipeline project, designers face the challenge of determining the regions of maximum and minimum stresses on pipelines, ensuring the stability of the bore-hole from collapse and minimizing the stresses induced on the pipeline due to the bore-profile.