Application of drag reduction technology of large section rectangular pipe jacking:A case study of rectangular jacking of Suzhou comprehensive pipe rack

Based on the rectangular pipe jacking project of people′s section of Chengbei Road in Suzhou, we analyzed the key factors affecting the jacking force of rectangular pipe jacking, and proposed comprehensive drag reduction methods about pipe weight, wax and grouting to reduce the wall friction resistance. Weights were placed inside the pipe to balance the buoyancy of the mud around the pipe. The surface of the pipe was painted with much wax, thus reducing the friction coefficient between the wall and surrounding medium. Also, we chose suitable materials and proportion to prepare the mud appropriate for the ground, and adjusted the grouting amount and pressure so as to form a good "mud jacket" around the pipe. Finally, by comparing the measured jacking force with the theoretical calculation value, we found that the friction resistance per unit area of the pipe wall was reduced by about 40%, solving the problem of excessive jacking force of rectangular pipe jacking in people′s section.