UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Design parameters for using controlled low-strength material backfill to manage axial soil loads on buried pipelines Zulkoski, Caroline Annette


Buried pipeline systems form a key component of the oil and gas transportation infrastructure, and the performance of these systems located in areas subject to potential ground movements is a critical consideration in engineering design. In mitigating against future or on-going ground displacement hazards, there are instances where the axial soil restraint (soil anchoring capacity) needs to be increased to avoid transferring loads to adjacent potentially vulnerable components in the pipeline system. One method to increase axial soil restraint is to increase the effective diameter of the pipeline. This can be done by encasing the pipeline in controlled, low-strength material (CLSM). The use of CLSM to increase axial soil restraint on buried pipelines requires that the axial load to produce pipe-CLSM interface bond failure be greater than that required for failure at the CLSM-soil interface. To advance the state of knowledge of the axial failure mechanisms of the soil-CLSM-pipe composite, a systematic full-scale testing program was undertaken using the Advanced Soil Pipe Interaction Research (ASPIReTM) modeling chamber at the University of British Columbia. First, twenty-two pipe-CLSM axial pullout tests were completed to assess the bond strength at the interface between CLSM and NPS 8 steel pipe specimens with various coatings. The research findings are presented, and the bond strength is assessed as a percentage of compressional strength to compare to observations from other researchers. Next, five full-scale axial pullout tests on pipes encased in CLSM, and in turn, buried in a soil backfill were conducted, using the results from the pipe-CLSM bond strength testing as well as two initial calibration tests. The work involved special modifications to the existing testing system. The test results are compared to those predicted using the PRCI (2009) guidelines. The ultimate loads measured are in good agreement with the predictions confirming the suitability of current guidelines employed to estimate the anchoring forces generated by encasing pipelines in CLSM backfill.

Item Citations and Data


Attribution-NonCommercial-NoDerivatives 4.0 International