An Improved Model to Calculate Pullback Force of Trenchless Horizontal Directional Drilling Pipeline

Table 1

Comparison of pullback forces in three cases.

Calculation method	Engineering
	AA	BB	CC
Unloading arch earth pressure method (kN)	2261	1221	923
Winch calculation method (kN)	718	693	997
Actual pullback force (kN)	810	997	681