Pipe Haunching Study Using Non-Linear Finite Element Analysis Including the Use of Soilcrete

摘要

Placing material in the hard to reach places underneath a pipeline called the haunches, is very difficult to do and very labor-intensive. This is one of the most important tasks when installing a pipeline. The main objective of pipe haunching is to provide firm uniform support to the pipe that will not change over time due to consolidation, moisture ingress, collapse etc. This is the main reason for specifying the use of a well-graded free-draining sand-gravel type of material in the pipe haunches. The purpose of this paper is to evaluate the effect of different haunching techniques (i.e., placement and compaction of material underneath the pipe in the haunches) on the predicted structural responses and performance of buried pipes using a non-linear finite element analysis program. Results are presented for the following typical installation conditions: 1. No haunching (i.e., loose/dumped support such as 50% Standard Proctor density), 2. Haunching (i.e., firmer support such as 85% Standard Proctor density), 3. Placing silty sand (i.e., AASHTO A-2-4) material in the haunches, 4. Placing well-graded sand-gravel material (i.e., AASHTO A-1-a, A-1-b) material in the haunches, and 5. Using flowable low-strength soilcrete (i.e., 700 kPa compressive strength) in the haunches. Results reported herein include predicted pipe structural responses for a DN1200 steel pipeline such as deflection, wall thrust, normal pressure and bending moment. Lastly, the importance of proper pipe haunching and the beneficial use of soilcrete are clearly demonstrated from the results of the parametric study.