Group Effect of Pipe Jacking in Silty Sand

Jacking force is one of the most important parameters in pipe jacking engineering, and also the key in pipe jacking design. A lot of research has been done on the prediction of jacking force of a single pipe. However, the research on jacking force of a row of steel pipes is relatively rare. A case of pipe jacking project is studied in this paper. In construction the test pipes were successfully jacked into the designed position, but the subsequent pipes were stuck because the jacking machine could not provide enough jacking force. Based on this phenomenon, the influence on the jacking force from the pipe spacing and the number of pipes have been jacked around the pipe being jacked is studied by field measurement and numerical simulation. The mechanism of the steel pipes stuck after the test pipes is analysed in detail. The results show that the jacking force decreases nonlinearly with the increase of the pipe spacing, and the influence range of pipe jacking is three times the pipe diameter; the jacking force increases with the increment of the number of pipes that have been jacked, but the increasing trend gradually slows down. Based on the above results, the pipe group effect of jacking force is proposed which is verified by the measured data. The results indicate that the amplification and superposition effect of the jacking force should be considered in the design stage to avoid pipes stuck in the jacking process.