Which Method Should We Use for Estimating the Pmax in HDD? Let’s Figure This Out Together Once and for All!

Abstract

River crossing projects using the horizontal directional drilling (HDD) method often require drilling underneath embankment dams and levees, which are crucial infrastructures for flood control. In recent years, the U.S. Army Corps of Engineers (USACE) updated their Engineer Manual/Engineer Regulation related to drilling in dams and levees; particularly significant changes to the clauses about evaluating hydraulic fracture risk. The updated clauses could lead to overly conservative estimates of maximum allowable annular pressure in HDD (Pmax), which brings significant challenges in bore path design while maintaining the minimum factor of safety required by USACE. Although numerous studies searched for an adequate method for estimating Pmax with some field/laboratory results reported, the overall volume of data and level of detail of information currently available in the literature sources are not sufficient to conduct a rigorous evaluation of analytical models of Pmax. To solve this problem, the authors propose a research project that requires a collaborative effort from the International Society for Technology (ISTT) and the North American Society for Trenchless Technology (NASTT). Recognizing that ISTT and NASTT are world-class trenchless research hubs with many members who are pioneers of this topic, ISTT and NASTT are considered the most appropriate domains to solve this problem with. Throughout this paper, the current problems related to estimating Pmax are stated, and the necessity of collecting data from the records of hydraulic fracture in HDD projects is emphasized. This paper also describes the details of the research project: (1) the merit of this project, (2) the type of data/information required, (3) the anticipated research outcome, and others.