盾构始发负环管片和反力架拆除时机的影响因素分析

采用FLAC3D软件,分别对北京地铁大兴线01标盾构始发工程和一般地铁盾构始发工程进行模拟,分析负环管片水平位移与拼装管片环数之间的关系,研究负环管片和反力架的拆除时机及其影响因素.结果表明:随着拼装管片环数的增加,负环管片水平位移的增加经历了初始增长、快速增长、缓慢增长和稳定4个阶段.在负环管片水平位移进入第4阶段时,负环管片和反力架不再承担盾构推力,此时是拆除负环管片和反力架的最佳时机；摩擦系数、隧道埋深和管片外径3个因素对负环管片水平位移的影响显著；随着摩擦系数、隧道埋深的增加,水平位移均逐渐减小,且影响程度逐渐减弱；随着管片外径的增加,水平位移逐渐减少,但影响程度逐渐增强.

Analysis on the Influence Factors of the Demolition Timing for Negative Ring Segments and Reaction Frame during Shield Originating

The software FLAC3D was used to simulate shield originating engineering of 01 bid section of Daxing Line Beijing Metro and that of general metro respectively.The relationship between the horizontal displacement of negative ring segments and the number of assembling segments was analyzed.The demolition timing for negative ring segments and reaction frame as well as their influence factors were then investigated.It is found that the horizontal displacement of negative ring segments goes through four stages,namely,initial growth stage,rapid growth stage,slow growth stage and stability stage,along with the number of assembling segments increasing.The negative ring segments and reaction frame on longer bear shield thrust when the horizontal displacement is in the stability stage,and it is the best timing for the demolition of negative ring segments and reaction frame.The factors such as friction coefficient,buried depth of tunnel and the outer diameter of negative ring segment affect the horizontal displacement of negative ring segments significantly.With the increase of friction coefficient or buried depth of tunnel,the horizontal displacement decreases gradually,and the degree of influence is faded down.The horizontal displacement decreases gradually with the outer diameter of segment increasing,but the degree of influence is enhanced gradually.