Exploratory Data Analyses on CFRP Wrapped HDD Overbend Subjected to Combined Loading

Abstract

Horizontal directional drilling (HDD) is one of the popular pipeline trenchless construction techniques for sites where surface excavations and conventional trenching are not desirable. An integral part of the pipeline design and construction process is to perform stress analysis on the HDD overbends, which can be subjected to significant cross-sectional deformations due to stresses/strains imposed by thermal expansion and internal pressure. This paper proposes a novel approach to reduce the stress range in the HDD overbends using carbon fibre reinforced polymer (CFRP) wraps. Although this reinforcement technique is primarily used in the pipeline industry for repairing damaged pipes, there is a handful of recent studies that showed the promising effect of using CFRP reinforcement on undamaged pipe bends. A total of 259 finite element analyses are conducted with a different combination of pipe diameter to thickness ratio, CFRP length and thickness, fibre orientation, and internal pressure. An exploratory data analysis is then performed to demonstrate the impact of each variable on the maximum equivalent stresses imposed on the HDD overbend. The finite element results show that multi-directional fibre orientation leads to the highest reduction of peak equivalent stress on the HDD overbend. Besides, an increase in CFRP thickness results in a greater reduction of stresses on the HDD overbend. However, CFRP length does not have a noticeable effect on decreasing the stresses on the HDD overbend.