Abstract: To study the insitu trenchless technology of urban underground pipeline renewal and expansion, a mechanized trenchless pipeline renewal boring machine is designed. In addition, key technologies such as the pressure balance system of the excavation chamber, protected circulation system of the pipeline, and intensive design of the entire machine are studied and are successfully applied to the pipeline renewal test section project. An actual pushing force model is constructed through test data analysis to determine equipment configuration parameters, such as the cutterhead speed, thrust speed, and cutterhead cutting resistance. The actual excavation results show the following: (1) the trenchless pipeline renewal boring machine can effectively guarantee the largediameter steel concrete pipeline breaking and renewal, pipeline dredging, and maintenance; (2) the monthly footage of the equipment can reach 150 ~ 450 m, the protected flow rate is approximately 500 m3/h, the pressure of the excavation chamber is stable at 50~ 80 kPa, and the settlement is controlled within 4 mm, realizing simultaneous laying of new pipelines in one construction with insitu expansion of the steel concrete pipe, thereby improving the automation level of urban pipeline renewal construction.  The proposed machine provides a new construction method reference for mechanized trenchless pipeline renewal in old urban areas.

Key words: pipeline renewal boring machine, trenchless technology, intensive design, pressure balance, protected flow in pipeline, steel concrete pipe, finite element