Investigation into Factors Affecting Penetration Rate and Favorable Ground Types of Pipe Jacking

Improper assessment of the penetration rate (PR) of pipe jacking (PJ) may lead to serious schedule delays and cost overruns. In the current practice, PR is estimated on the basis of the experience of practitioners. This has resulted in predicted PR values that are not consistent with the actual ones. A guideline that can be used to reliably predict PR and account for the effects of the significantly controlling factors is not available. This negatively affects the estimated project time and cost. The problems stem from the many factors that affect PR such as the ground conditions, installation depth, machine type, operator experience, and pipe diameter. Little research has been made in this regard. So this research will focus on two main objectives; the first is to identify, categorize and rank the factors that affect PR, and the second is to investigate the common types of ground and PJ machines in Egypt and the Middle East to determine the favorable ground types for PJ machines.

To determine the factors that affect the PR of PJ and their relative importance, interviews were made with 17 PJ experts in Egypt. Then, a questionnaire was sent to 149 PJ experts in Egypt and the Middle East. The obtained responses were analyzed and the relative importance of all factors was determined. Based on the interviews with experts and the questionnaire survey, the favorability of ground types for the slurry and auger machines was determined.

The responses and analysis results of the interviews and questionnaire are weighted using the relative importance method and then ranked. The analysis reveals that 20 factors significantly affect PR. The top 5 factors that affect PR are 'ground type', 'ground condition', 'geotechnical investigation', 'crew/operator experience', and 'pipe lubrication'.

Among the ten new factors which are introduced in this study, the four factors 'ground type', 'ground settlement', 'bentonite water ratio', and 'feed flow rate' are assessed as significant and ranked as the 1st, 7th, 16th, and 20th most important, respectively. It is also concluded that sand and silty sand are very highly favorable for the slurry machines, while silty clay is very highly favorable for the auger machines.