中文摘要：

为阐明土压平衡盾构挤土与排土掘进状态对周围土体的扰动机理,采用离散元方法建立土仓不排土与排土两组盾构掘进二维数值模型,比较分析了两种工况下盾构掘进时掌子面及周围地层的细观力学变化特征.研究表明：不排土工况下,盾构对周围土层有明显挤密,土体竖向位移呈椭圆形、水平位移呈圆形向前方扩散变小;排土工况下,刀盘周围土体无明显挤密,水平位移很小,竖向位移呈不规则漏斗状向地表延伸变大.不排土对周围土体应力影响大,掌子面水平应力分布均匀;排土工况下盾构前方土体应力与初始地层接近,土仓的排土,使掌子面水平应力的分布变化较大.

英文摘要：

In order to clarify the disturbance mechanism of the soil around the earth pressure balance（EPB）shield affected by the squeezed and exhausted soil situation of tunneling,discrete element method（DEM） was adopted to establish two groups of two-dimensional numerical models of EPB shield tunneling. The comparisons were carried out to analyze the mesomechanical characteristics of soil at the tunnel face and its surrounding strata during the shield tunneling. This research shows that the shield squeezed the surrounding strata obviously when the soil in the chamber was not exhausted. The vertical displacement developed ovally,while the horizontal displacement developed circularly,all of which decreased with an increase in distance along the horizontal direction. When the soil in the chamber was exhausted,the soil ahead of the cutterhead was not densified obviously,the horizontal displacement was low,and the vertical displacement developed to be irregularly funnel-shaped and higher. When the soil in chamber was not exhausted,the influence of shield tunneling on soil stress ahead of the tunnel face was significant,and the distribution of the average horizontal stress at the tunnel face was uniform. However,with the soil being exhausted,the stress of soil ahead of tunnel face was similar to the initial soil condition,and the distribution of the average horizontal stress at the tunnel face varied greatly due to the soil exhausting.