为解决膨胀性盐岩地层隧道修建时出现的大量衬砌裂缝、仰拱底鼓开裂等问题，同时为保证隧道后续快速安全施工及长期健康服役，采用现场调查、数值模拟和监控量测等方法，对膨胀性盐岩地层隧道结构及施工技术进行深入研究。研究结果表明： 1）含盐地下水对混凝土的侵蚀引起的膨胀压力是原马蹄形隧道衬砌开裂的根本原因。2）250 kPa的地层膨胀压力可大幅度增大围岩变形，但对隧道掌子面纵向挤压变形基本没有影响，可减小拱顶处的最大主应力，但会大幅度增大仰拱处最小主应力。3）多层支护可对洞周围岩变形起到积极的约束作用，也可明显减小掌子面纵向变形，对初期支护最大主应力基本无影响； 无膨胀压力时，会引起墙脚最小主应力集中；
有膨胀压力时，可减小其他部位的最小主应力。综合考虑围岩稳定性、支护受力以及施工成本控制等，膨胀性盐岩地层多层支护隧道施工宜采用二台阶法。现场实测证明采用3层衬砌、2层防水、全环注浆并施作隧底阻水榫后，围岩变形量小，衬砌未开裂。通过指数函数对围岩变形进行拟合，证明数值计算结果基本可靠。
When constructing a tunnel in expansive salt rock
strata, problems such as extensive lining cracking and inverted arch cracking
will be encountered. To ensure rapid construction and longterm
effective service of such a tunnel, the field investigation, numerical
simulation, and field measurement of the tunnel structure and construction
technology in an expansive salt rock stratum are analyzed. The following
results are obtained. (1) The expansion pressure caused by erosion of the
concrete by saline groundwater is the root cause of the original lining
cracking in the horseshoeshaped tunnel. (2) An
expansion pressure of 250 kPa significantly increases the deformation of the
surrounding rock but has a negligible effect on the longitudinal deformation of
the tunnel face. This reduces the maximum principal stress at the crown but
significantly increases the minimum principal stress at the inverted arch. (3)
Multilayer supports can play a positive role in restraining
the deformation of the surrounding rock and can significantly reduce the
longitudinal deformation of the tunnel face. However, it has no effect on the
maximum principal stress of the primary support. The absence of expansion
pressure causes the minimum principal stress to concentrate at the wall foot,
whereas the presence of this pressure reduces the minimum principal stress in
other parts. Considering the stability of the surrounding rock, supporting
force, and construction cost, a twobench method is
recommended for installing multilayer supports in
tunnels constructed in expansive salt rock strata. The field measurement shows
that the deformation degree of the surrounding rock is small and that the
lining is not cracked after installing three layers of concrete, two layers of
waterproof material, fullring grout, and water
blocking tenons in the bottom of the tunnel. Fitting the deformation of the
surrounding rock with the exponential function proves the accuracy of the
numerical calculation.
