Selection of jacking sequence and jacking parameter analysis of multi-row jacking pipes in water-rich sand

For the purpose of safe and efficient construction of multi-row pipe jacking in water-rich sand layer, a case study was carried out, taking the three-row pipe jacking project of the water-rich sand layer in Haikou city as an example. Firstly, based on the analysis of the disturbance mechanism of surrounding rock in multi-row pipe jacking construction, the principle that multi-row pipe jacking construction should give priority to excavate two pipe jacking tunnels which are far apart in turn was established. Secondly, taking the maximum ground settlement at the center of pipe jacking as the judgment index, the optimal scheme of the construction sequence of multi-row pipe jacking was determined. Finally, based on the field measured data, the relationship between the jacking force, the pressure of the palm surface, the average frictional resistance and the jacking process during the jacking process was analyzed, and summarized the experience of the site construction. The results show that: (1)it is better to give priority to construct two pipe jacking tunnels which are far apart in the construction order multi-row pipe jacking; (2)Based on the empirical method of surface subsidence, the maximum surface subsidence at the center of pipe jacking group can be used as the judgment index to determine the optimal jacking sequence; (3)Under the condition of "from the two sides to the middle", the surrounding rock around the middle jacking pipe is greatly disturbed by the construction of the first jacking pipe, its jacking rate should be reduced on the basis of the first building jacking pipe, and the cutting rate of the cutter and the grouting pressure should be increased, so as to realize the continuous jacking construction. The results of this paper are of great reference value to the determination of the jacking parameters of multi-row pipes in the future.