Abstract: 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 longterm 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 horseshoeshaped 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) Multilayer 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 twobench method is recommended for installing multilayer 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, fullring 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.

Key words: salt rock tunnel, expansion pressure, structure optimization, numerical simulation, onsite monitoring