To study the dynamic response of a saturated sand-underground structure system subjected to earthquakes, a series of shaking table tests with a geometric scale ratio of 1/30 were conducted. Based on the experimental acceleration records of testing soil deposits, the relationship between dynamic shear stress and horizontal soil displacement was analyzed by the 1D shear beam inverse calculation method. Meanwhile, the development law of the equivalent dynamic horizontal subgrade reaction coefficient and the dynamic strain of the sidewall in the underground structure has also been discussed. The testing results indicate that the dynamic shear stress of the soil deposit under the bottom plate of the underground structure is larger than that of the soils surrounding the sidewall and above the roof plate; in addition, the soil displacement tends to decrease with the buried depth. The dynamic shear stress–displacement hysteretic loop of the soil deposits tends to be plump as the input amplitude increases. The spectral characteristics of ground motions obviously influence both the dynamic shear stress–displacement hysteretic curve and the excess pore water pressure ratio of saturated sand soil, especially under medium and strong excitations. The equivalent dynamic horizontal subgrade reaction coefficient decreases with the increase of soil depth, and the difference between the coefficient above and underneath the underground structure model can reach 7.589 MN/m3. On the contrary, the equivalent dynamic horizontal subgrade reaction coefficient decreases with the increase of the input amplitude of ground motions, and the maximum reduction ratios of the coefficient are 74.4%, 66.7%, and 47.3%, corresponding to the El-Centro, Kobe, and Wolong ground motions, respectively. The soil liquefaction has a certain effect on the equivalent dynamic horizontal subgrade reaction coefficient. In general, the dynamic strain at the top of the sidewall in the underground structure is higher than that at the bottom of the sidewall, which illustrates that the deformation of underground structures is in good agreement with the seismic deformation mode of soil deposits.

Shear keys are usually installed as crucial shear-resistant members of an immersion joint; thus, the mechanical behavior of the shear keys, especially under earthquake loading, deserves more attention. This paper presents a novel arc-shaped energy absorption device developed for shear keys. In order to verify the seismic performance of shear keys strengthened by the arc-shaped energy absorption devices, a series of pseudo-static tests were conducted, in which different axial pressures (300 kN, 400 kN) were also taken into consideration. The testing results indicated that failure mode of the shear key enhanced by the energy absorption devices was a synthesis of the oblique shear failure of the rubber blankets, the buckling of the energy absorption devices, and the concrete fracture of the shear key. In view of load-displacement hysteretic curves of testing specimens, loops of the reinforced shear keys were plumper than those from a traditional shear key. In addition, the load-bearing capacity (cracking load, yield load, peak load, and failing load) differences of the shear keys with and without energy absorption devices reinforcement under the same axial pressure were 33.0%, 36.7%, 26.0%, and 23.6%, respectively. The maximum equivalent viscous coefficient values of the shear keys with and without energy absorption devices reinforcement were 0.37, 0.38, and 0.32, respectively. The arc-shaped energy absorption devices can contribute to the hysteretic behavior of the shear keys. However, the axial pressure had a positive influence on the load bearing capacity, accumulated energy absorption capacity, and initial stiffness of the shear keys. In contrast to that, the axial pressure had negative influence on ductility ratio of the reinforced shear keys (equivalent viscous coefficient values of two enhanced shear keys were roughly equal). A reasonable stiffness scheme of an energy absorption device should be given attention during the anti-seismic design of an immersion joint. The study can provide scientific support for further study on the seismic responses of immersion joints and promote the application of earthquake control technology in immersed tunnels.