膨胀地层层状膨胀对盾构隧道结构荷载影响

Influence of Stratiform Expansion of Expensive Strata on Structure Load of Shield Tunnel

研究目的:层状地层中地下水位的均匀降升将引起膨胀岩土发生层状均匀膨胀,从而影响盾构隧道衬砌结构所受的荷载。本文从理论上推导岩土层状膨胀引起的地层应力计算公式,并对隧道上方、下方及两侧地层发生层状膨胀时衬砌结构的外侧压力进行数值计算。研究结论:(1)由于土体物性参数发生改变,岩土层状膨胀将引起隧道结构外侧压力发生改变,产生附加荷载,该荷载与岩土膨胀力大小、自由膨胀率等因素有关;(2)当层状膨胀产生于隧道上方或下方时,该膨胀荷载量值较小,且受岩土膨胀力、层厚、与隧道间距的影响也较小;(3)当层状膨胀产生于隧道两侧时,岩土膨胀引起的隧道结构外侧荷载增量较大,且其值随岩土膨胀力的增大而显著增加,一定膨胀范围及膨胀力对隧道结构所受的荷载是有利的;(4)该研究结果可用于指导盾构隧道结构设计中膨胀荷载的取值。

Research purposes： In stratiform strata, the uniform falling and rising of underground water level will cause the stratiform expansion of expansive rock and soil strata to affect the load on shield tunnel lining structure. The equation for the stress formation caused by stratiform expansion was deduced and numerical calculations were carried out for the outside pressure on the lining structure when the stratiform below the tunnel and on both sides of tunnel. expansion happened to the expansive soils mass above and Research conclusions： （ 1 ） As the soil physical parameters change, the stratiform expansion of soil mass will bring about the change of the outside pressure on the structure and generate the additional load. This expansive load is related to the expansion force and the free expansivity of the expansive soil. （2） When the stratiform expansion of expansive soil mass appears above or below the tunnel, the expansive load is small, and is less affected by the expansion force, thickness of expansive soil and distance between tunnel and expansive soil mass. （3） When the stratiform expansion of expansive soil happens on both sides of tunnel, the outside pressure on the tunnel structure increases largely, and the load increases with the increase of expansion force of the expansive soil. However, a certain expansion scope and expansion force are beneficial to the load on tunnel structure. （4） The research results can be used for guiding the sampling values of expansive load in design of shield tunnel structure.