Calculations and Analysis of Pullback Force in Horizontal Directional Drilling

When using horizontal directional drilling (HDD) technology in a pipeline crossing project, the required pullback force is an important factor in the selection of the pipe strength and drilling equipment, as well as the construction technique. There are presently several methods used to calculate this force. However, because of the complexity of the field conditions, it is difficult to construct a mathematical model that exactly matches the actual operation. It is therefore recognized that the pullback force cannot be precisely calculated, but may only be estimated. The present study considers several methods used to calculate the pullback force and compares the values. Based on these results, a modified procedure is recommended, which is verified to provide reasonable estimates of the pullback force reflecting the load due to the product pipe as well as that due to the reamer and drill string.