根据砂卵石地层力学特性,结合北京地铁4个标段工程,分析土压平衡盾构刀盘扭矩各组成部分所占的比例,提出简化的刀盘扭矩计算公式.分析计算结果表明:刀盘开口率与刀盘扭矩成反比,开口率每增加10％,刀盘扭矩降低8％～10％；土体的流塑性对刀盘扭矩影响较大;土体的摩擦系数每降低0.1,刀盘扭矩相应降低约35％～40％.在北京地铁10号线二期工程现场进行盾构掘进试验,分别通过刀盘改造(开口率增大至40％)及土体改良,使刀盘扭矩保持在2 500～3 500 kN·m,盾构推进速度明显得到改善.试验结果进一步验证了增大开口率及土体改良是在砂卵石地层降低刀盘扭矩的2项非常有效的措施；也验证了刀盘扭矩计算公式是合理的、可靠的,满足工程实际需求.%According to the mechanical properties of sand gravel strata,and combined with four bid sections engineering of Beijing Metro,the proportions of cutterhead torque in each composition part of earth pressure balance shield were found out,and the simplified formula of cutterhead torque was obtained.Analysis results show that cutterhead opening ratio is inversely proportional to cutterhead torque.Cutterhead torque decreases about 8％ to 10％ for every increase of 10％ in cutterhead opening ratio.Soil fluid plasticity has a great impact on cutterhead torque.For every decrease of 0.1 in soil friction coefficient,cutterhead torque decreases about 35 ％ to 40 ％ correspondingly.Shield tunneling tests were carried out in the second phase engineering of Beijing Metro Line 10.By means of cutterhead improving (cutterhead opening ratio is increased to 40％) and soil conditioning respectively,cutterhead torque can be controlled between 2 500 and 3 500 kN · m,and shield advance speed is improved significantly.Test results have further verified that increasing opening ratio and soil conditioning are two very effective measures for reducing cutterhead torque in sand gravel strata.It is also proved that the theoretical formula of cutterhead torque is reasonable and reliable,which can meet the demands for engineering practice.
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