Cobble strata have an extremely negative impact on shield tunnelling because of their loose structure, poor cementation, interparticle point-to-point force transmission, high sensitivity and large deformation. In order to explore the deformation law of a shield tunnel passing through a cobble stratum, and based on the lot 3 project of Beijing metro line 9—which is the first shield tunnel to pass through a waterless large-particle cobble stratum for a full section—the finite difference software FLAC3D was used to carry out a numerical simulation analysis. A comparative analysis indicates that the deformation induced by shield tunnelling in a large-particle cobble stratum is greater than that in an average stratum, including the maximum ground settlement, settlement trough width, pre-deformation range and settlement value and the deformation at the tunnel face. The conventional construction method is not suitable for a large-particle cobble stratum, and some special measures are therefore taken to control the ground deformation, including soil conditioning, enlarging the opening ratio of the shield cutterhead, increasing the jack thrust force and dynamic control during construction. Monitoring data indicates that these measures could effectively reduce deformation of the stratum and ensure safe construction.%卵石地层结构松散、胶结程度差、颗粒之间点对点传力、地层灵敏性高，开挖过程极易造成地层大变形，对于盾构隧道的施工极为不利。为了探明盾构隧道穿越这种地层的变形规律，文章以首例盾构全断面全程穿越无水大粒径卵石地层工程———北京地铁9号线03标段为背景，采用有限差分软件FLAC3D进行数值模型分析。通过与普通地层对比分析可知，盾构隧道在大粒径卵石地层中掘进引起的地表最大沉降值、沉降槽宽度、超前变形范围及沉降量、掌子面变形均较大。常规的施工措施无法满足大粒径卵石地层的需求，需要采取土体改良、增大盾构刀盘开口率、提高千斤顶推力、施工过程动态控制等特殊措施对地层变形进行控制。实际监测数据表明所采取的工程措施能有效降低地层变形量，确保施工安全。
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