Abstract: When a hard rock pipe jacking machine bored in an extra-long tunnel, phenomena of abnormal loss of thixotropic slurry, accumulation of debris, backflow of debris, and main thrust force dispersion-caused insufficient jacking force occurred. A case study is conducted on the #3 tunnel of Qianping water supply project in Ruyang, China, and a mechanized trenchless equipment, a hard rock pipe jacking machine, is designed and developed. Key technologies of coordinated linkage booster system, slurry-sealing device, debris collection system, and mud-water circulation system are analyzed. By analyzing the test data, a real jacking force model is established. The results show that: (1) Under a maximum load of no more than 16 000 kN, the rock-breaking capacity of the equipment meets the requirement of uniaxial compressive strength R_c> 195.93 MPa. (2) The coordinated linkage device and the #2 and #3 relay chambers of the equipment are activated in a 1 535 m-long tunnel, reaching required jacking force for tunnel jacking construction.

Key words: extra-long distance tunnel, hard rock pipe jacking machine, synergistic linkage booster, slurry-sealing device, debris collection system, mud-water circulation system