Investigation of Stress-strain Response for Accessing Safe Operational Depth of Buried Pipeline Under Static and Dynamic Ground Overload
Arsalan Muhammad Ahmad, Muhammad Zeeshan Zahir*, Zuhaib Ali Khan, Naveed Ullah, Shaukat Ali Shah, Ashfaq Khan
Department of Mechanical Engineering, University of Engineering and Technology Peshawar, Peshawar 25120, Pakistan.
Corresponding Author Email: firstname.lastname@example.org
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Demand for underground trenchless pipeline installation in urbanized setting has dramatically increased over a past few years. Trenchless method for piping installation has numerous advantages including avoid road closures, loss of access to homes and business, noise reduction and avoid general disruptions. This study analyzes the stresses induces on the trenchless buried pipeline under the combined effect of dead load of the soil and external vehicular loading. Underground pipelines experience bending stresses due to the reaction forces of continuous traffic motions on the periphery of the soil. The stress variations due to these external loads depend on the engineering attributes of subsoil and on the burial depth of the gas pipeline. The traffic load over a gas pipeline applies a vertical pressure load on the pipe that induces the strain in the buried pipeline. Given dynamic loading, the dynamic stresses induced are critical, and if these stresses continue to act over a large period, the result can cause fatigue failure of the buried pipelines while static stresses can cause creep failure to the buried pipelines. In both scenarios, the pressurized natural gas will cause environmental damages and catastrophic failures. Thus, the objective of this paper is to find the effect of vehicular load on buried pipelines and resulting stress-strain response induced in these pipes under the application of static and dynamic loading under several depths. The analyses were conducted on standard X42 pipes with variable diameters under several burial depths. The strain measurement is done through strain gauge installed at the mean length of the pipes on the upward periphery. The tests were used to measure the strain induced in small diameter buried natural gas pipelines under the soil, and vehicle load and the influence of pipe diameter, soil type, burial depth, and vehicle load on the Pipeline strain was compared through the experimental setup. The Pipe stress variations under the dynamic vehicle load were used to analyze the fatigue life of the pipeline. Keeping into consideration the mentioned parameters, safe burial depth for these pipelines were recommended for better operation and integrity of fuel being transported. The results show that for a 2-in pipeline, the numerical value of strain damped to average 75% of the initial value at 3-ft depth and for 1-in and 0.75-in pipelines, strain damped to an average of 95% & and 98% for various vehicular loads. So according to no strain condition burial depth for a 2-in pipeline is 4-ft while for 1-in and 0.75-in it is 3-ft respectively.