Resistance reduction by grouting to large diameter and long distance steel pipe jacking:A case study of pipe jacking project in the upstream water source area of Huangpu River

C3 section in the connecting pipe jacking project in the upstream water source area of Huangpu River is constructed by DN4000 steel pipe jacking with the length of 969.94m in a single jacking. As the reduction of resistance is the key aspect of the project, this paper studies the preparation and the use of slurry in order to reduce the resistance to decrease jacking force. Besides, based on the change of jacking force under the geological conditions of JB06-JB05 and JB07-JB06, the paper analyses the variation rule of resistance. The results show: ①The reduction effect is obvious with proper arrangement of grouting holes, the preparation and use of slurry. ②Jacking force is approximately linear with jacking distance but the character of geological condition may lead to sudden change of jacking force. ③The slurry which has been injected for some time performs better than freshly injected slurry. ④Friction can be effectively reduced by increasing the grouting volume properly. ⑤Polymer bentonite mud is more expensive but the grouting volume of it is less. Considering various kinds of factors, polymer bentonite mud is more favorable than bentonite mud.