Estimating the Required Jacking Force

The process of estimating the required jacking force to jack a pipe through the ground was, and still is, an art requiring much experience and good judgement. Many factors and risks affect the determination of the jacking force. This paper is an attempt to use civil engineering techniques to rationalize and compare methods for estimating the required jacking force. Four of these methods are summarized and used to estimate the jacking loads on a job completed in Staten Island, New York. The actual and predicted results are compared. The frictional resistance values estimated based on Terzaghi 1 s silo theory with the parameter values selected based on guidance given in the German AWPC manual 11 ATVA 161 11 and in the Kubota are five to seven times higher than the average actual jacking forces. On the other hand, the frictional resistance force calculated by Marston 1 s formula and Terzaghi 1 s coefficient are about twice the average actual jacking force. Therefore, based on this comparison only, multiplying the force calculated by these latter two formulas by an adequate factor of safety would be more appropriate. Terzaghi Is theory with the parameter set of the ATV A 161 and Kubota method are conservative but not the most economical solution. The penetration or tip resistance values estimated using the shear strength resistance method are much lower than those calculated using the passive earth pressure method, which represents the most conservative method