Numerical Modeling of the Annular Failure Pressure during HDD in Noncohesive Soils

Abstract

One of the critical issues that engineers, contractors, and owners encounter during horizontal directional drilling (HDD) is inadvertent return of drilling fluid (frac-out or hydraulic fracture) to the ground surface when the annular pressure in the borehole exceeds the yield shear or tensile strength of the soil. In this study, numerical modeling using ABAQUS software (version 6.13) was employed to estimate the failure pressure in several case studies following the limit pressure solution. In the next step, a large-strain cavity expansion solution was used to estimate the failure pressure, which was then compared to the estimations based on numerical modeling following the limit pressure solution. A parametric study using numerical modeling was conducted to examine the influence of the geotechnical parameters of the soil medium on the limit pressure. The parametric study showed that overburden depth, friction angle, and elastic modulus of the soil have a significant impact on the limit pressure. The ratio of limit pressure according to analytical and numerical solution resulted in coefficients of limit pressure in different geotechnical conditions and can be used to estimate the failure pressure in noncohesive soils using the large-strain cavity expansion solution.