为解决扬州瘦西湖隧道泥水盾构在膨胀性黏土地层停机时开挖面失稳和地面塌陷的问题，采用膨胀试验和崩解试验，研究下蜀黏土的膨胀特性和崩解特性。利用现场实测资料和数值模拟结果分析和论证膨胀性黏土地层停机时地表塌陷的原因： 泥浆持续渗透引起开挖面前方土体膨胀、崩解和剥落是导致开挖面失稳的原因； 开挖面的失稳过程可以分为4个阶段，分别是泥浆渗透阶段、开挖面前方土体膨胀崩解阶段和开挖面上方土体塌落阶段、塌落发展到地表形成地表塌陷阶段。提出控制盾构掘进参数、多次短停、适当提高泥水支护压力和适当增加泥浆密度、黏度等防止泥水盾构在膨胀性黏土地层停机时开挖面破坏的措施，并指导现场施工，取得较好的应用效果。

Excavation face failure and ground surface subsidence occurred at shield stopping section in expansive soil during the construction of Slender West Lake Tunnel. As a result, the expansion test and disintegration test are carried out. The main cause of the excavation face failure and ground surface subsidence, continuous permeation of slurry, is analyzed by site monitoring data and numerical simulation results. The excavation face failure can be divided into 4 phases, i. e. slurry permeating, soil expanding and disintegrating in front of excavation face, soil collapse above excavation face and ground surface subsidence. A series of countermeasures, such as shield boring parameter control, shield stop frequently and transiently, slurry support pressure increasing and slurry improving, are proposed and used. The good effect is achieved.