## 1 Introduction  
With the acceleration of urbanization and the development of underground municipal infrastructure, pipe jacking construction technology is increasingly used for large cross-section power electric tunnels to reduce the underground engineering construction influence on the urban environment. Moreover, the urban underground construction is becoming space constrained, and some pipe jacking tunnels are arranged in a vertical double-layer layout [1, 2]. Jinan city is located on the north side of the extension of Mount Tai. The southern urban area belongs to the slope deposit stratum. The landform changes from mountain area to plain in space, and the corresponding geology will also have a gradual transition from rock layer to soil layer. The places with high terrain are mainly exposed rock mass or covered with thin layer of Quaternary strata, whereas the low-lying areas have a thicker Quaternary strata, forming the formation of soil-rock composite strata. The cross section of the shallow buried pipe jacking tunnel is in the soil layer and the underlying bedrock at the same time. Jinan is located in the North China Earthquake Region, which is the most powerful earthquake region in the eastern mainland of China. Jinanhas had moderate and strong earthquakes and has also been affected by the surrounding earthquakes, which have caused great damage. In previous studies, the seismic damage in the soil and hard rock sections of existing tunnels shows that serious seismic damage such as lining cracking, lining staggering, concrete peeling and block falling easily occurred due to the combined action of seismic inertia force and forced displacement [3; 4; 5]. The soil-rock combination stratum is distributed in domestic cities with subway construction, such as Qingdao, Jinan, Shenzhen, Guangzhou, Chengdu, etc. Due to the large difference in soil layer and rock layer stiffness, the pipe jacking structure is located in soil-rock combination strata, which brings certain difficulties to the structure construction. More importantly, China is an earthquake-prone country. At present, the understanding of earthquake failure mechanisms and the earthquake resistance of underground structures is still insufficient. In soil-rock combination stratum, especially due to the embedded constraint of rock and the influence of ground motion propagation speed, there are more uncertainties and challenges to the ground motion response mechanism of underground structures such as pipe jacking. In recent years, a series of numerical analyses and shaking table tests have been carried out on the seismic responses of shield tunnels and mountain tunnels. [PERSON] et al. [6; 7] studied the horizontal nonlinear seismic response characteristics of the double-layer shield tunnel under near-field and far-field earthquake action and strong ground motion near the fault. [PERSON] [8] studied the influence of two parallel tunnels in the horizontal direction and vertical direction on the tunnel dynamic response and ground peak acceleration at different intervals. However, the above study only analyzed tunnels in homogeneous soil stratum. [PERSON] [9] and [PERSON] [10] reported that tunnels located in the homogeneous soil layer are relatively safe even if they are affected by a strong earthquake. However, under complex geological conditions, the stratum displacement and strain response of the tunnel caused by the earthquake is different from that of homogeneous stratum. [PERSON] et al. [11] analyzed the failure mechanism and relevant seismic measures of the Qingdao subsea tunnel structure at the soft-hard junction. [PERSON] [12], [PERSON] [13], [PERSON] [14] and [PERSON] [15] carried out shaking table tests, obtained that the shield tunnel obtained the maximum internal force at the sudden change of soft and hard strata and pointed out the weak position of the longitudinal seismic resistance of the shield tunnel structure, respectively.