Abstract:

In the shield construction, the shield attitude is controlled by continuously adjusting the zone pressure. However, if the gap between the pressure parameters of each zone is too large, the shield attitude deviation will be aggravated. Combined the case of the settlement in saturated soft soil when a city metro under passing the river section, it shows that when the settlement deviation of the shield itself occurs, the adjustment of the regional pressure parameters is unreasonable, resulting in uneven thrust of the shield and accelerated the sinking of the shield. Through comparative analysis of the regional pressure parameter settings of the shield propulsion, the continuous sinking process of the shield attitude is described in detail, and the reasons for the adverse effect of overadjustment of the regional pressure on the attitude of the shield are analyzed. According to the reactive force of the shield propulsion pressure on the segment, from the standpoint of mechanics, the adjustment of the shield attitude is the adjustment principle of the shield zone pressure setting. The forced state formed by the shield attitude presents the result of the reverse deviation, which caused by the shield deflection and the unevenness of tunnel segments. The deflection amount of the two is reversed and the adjustment of zone pressure causes that the deflection of the forming tunnel is larger than the deflection of the shield itself, and the shield attitude will be more deviated and the zone pressure is excessively adjusted. The conclusion points out the misunderstanding of attitude adjustment during the shield construction, and provides insights into the rationality of the setting of propulsion parameters for shield construction.

Key words: zone pressure setting, shield attitude, parameter setting, force, partition pressure