Performance of Buried Concrete Pipe Under Different Environmental Conditions

Open Access
Author:
Ban, Hoki
Graduate Program:
Civil Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
January 29, 2008
Committee Members:
  • Mian C Wang, Committee Chair
  • Derek Elsworth, Committee Member
  • Andrew Scanlon, Committee Member
  • Sunil K Sinha, Committee Member
Keywords:
  • cracking behavior
  • concrete pipe
  • soil pressure
Abstract:
To provide the database needed for the development of a numerical model for predicting structural stability of buried concrete pipes, the performance of buried concrete pipes under different environmental conditions was investigated. The prediction model is an essential element in a holistic management program used to manage the vast network of existing pipeline infrastructure system. The research was conducted using the commercial finite element program, ABAQUS. In the program, the user subroutine, UMAT, was developed to take into consideration the material properties of pipe-soil system. The developed UMAT was validated using available database. The numerical analysis was performed for various environmental conditions including different backfill materials and native soils, groundwater table, loading types, and nonuniform support conditions due to presence of void around the pipes. Results of analysis provided soil pressure distributions along pipe periphery, hoop stress, thrust, and internal moment in the pipe wall, and cracking behavior under various environmental conditions. From these data, the performance of buried concrete pipe was evaluated. Based on the results of analysis, conclusions in terms of serviceability of buried concrete pipes are drawn. Among the more notable conclusions are (1) pipes embedded in silty clay trench material surrounded by a native sandy soil will last longer than pipes in other materials, while other influence factors being constant; (2) pipes under uniform surface loading will have shorter service life than under longitudinal and transverse loading of the same intensity; (3) submergence of pipes in groundwater will shorten service life; (4) presence of void around pipes will reduce service life; (5) voids at lower haunch area have greater effect on pipe service life than voids at invert. This finding emphasizes the importance of compaction at lower haunch area during pipe installation. Along with these conclusions, recommendations were made. An important recommendation is that field testing is essential for validating the developed prediction model.