| At present,with the gradual improvement of China’s economic development level,the rapid development of cities,the construction of urban rail transit is increasing,and the cross-line transfer of subways is also increasing,which will inevitably lead to overlapping tunnels and even overlapping of multiple tunnels.Under the complicated environment and tight schedule of newly-built overlapping tunnels,the construction sequence of first-in,second-in,down-and-down is worth considering.A series of comparative analysis can not be ignored.This paper relies on the intersection of Shenzhen Urban Rail Transit Line 9 and the South Extension of Line 6 as the research background.Under the unfavorable factors such as relatively tight construction period and complicated geological conditions,from the comparison of construction sequence and spatial position,After studying the mechanical effects of different spatial positional relationships,the numerical simulations were carried out for each construction stage of the five characteristic sections of the overlapping tunnels.It was determined that displacement of the bottom arch of the section 3 was the largest and the part needed to be strengthened.Because the vehicle load of the upper shield construction will affect the underground mine tunnel,the internal force of the stratum is simulated by simulation,and the auxiliary engineering measures such as pre-reinforcement and pre-support are combined with the mining method to increase the support of the lower hole.Considering the factors of the construction site,the numerical simulation was carried out to determine the necessity of pre-reinforcing and pre-supporting the surrounding surrounding rock,and the economic optimization was carried out to determine the pre-reinforcement range and the pre-support spacing.Finally,the monitoring and measurement of the upper and lower tunnels is carried out.It is concluded that the measured data of the settlement is consistent with the overall trend of the simulation predictions.The theoretical model,physical parameters and calculation process used in numerical simulation are correct,and the results can be used to select construction.Figure[93]table[19]reference[58]... |
