Estimation of Maximum Annular Pressure during HDD in Noncohesive Soils

Abstract

This study investigated the effectiveness of estimating the maximum allowable annular pressure during horizontal directional drilling (HDD) in noncohesive soils by using two theoretical cavity-expansion solutions (small strain and large strain); several laboratory and field tests were used for verification. The results indicated that the measurements were overestimated when using the plastic radius equal to two-thirds of the overburden depth and underestimated when using the hoop strain equal to 2%. Although the calculated limit pressures based on the two cavity-expansion solutions were higher than the measured failure pressures, a high correlation (R2 = 0.96) existed between the measurements and the calculations based on the large-strain cavity-expansion solution. This correlation may be used to estimate the maximum allowable annular pressure during HDD in noncohesive soils, provided that further validation is conducted with more field data for deep depths rather than shallow depths.