# Model Test Study on a Shield Tunnel Adjacent to Pile in the Sub-Clay of a Coastal Area
## 1 Introduction  
The geological conditions of silty clay in coastal areas are complex. The geological characteristics of coastal silty clay vary between cohesive soil and sandy soil. The deformation mechanism is more complex under the disturbance of shield construction. In addition, the permeability and the stability of the formation are poor, and the disturbance degree of the surrounding rock is significant. Under these geological conditions, retaining the effect of pile is important and its mechanical properties deserve attention. At the same time, the effect of grouting on the soil with the pile foundation is also a cause for concern.  
Through model tests and theoretical analysis, scholars have carried out a significant amount of research on the interaction between the surrounding rock-pile caused by shield construction, providing some beneficial insights. The scale model test was carried out on the \(\Phi\)800 mm earth pressure balance shield test system to study the influence of shield on sand pebbles and sand strata [1]. [PERSON] [2] applied the centrifugal model test to determine the influence of tunnel excavation on the end bearing of the pile; the pile was greatly affected by the spacing of the pile-tunnel, which was less than 0.25\(D\) (\(D\) is the diameter of the tunnel). An increase in soil loss will cause an increase in the vertical amount of pile settlement if the spacing of the pile-tunnel is in the 0.25\(D\)-1\(D\) range. This influence will be relatively small if the spacing of the pile-tunnel is greater than 2\(D\). Using the indoor model test of tunnel excavation migration and adjacent pile caused by the variation inthe bearing capacity of pile, [PERSON] [3] concluded that the maximum bending moment of pile tunnel spacing is \(1.5D\), which increases with an increase in soil loss.  
According to an analysis of the line selection of the English Channel and the relationship between the settlement of the pile and the settlement of the surface, [PERSON] [4] partitioned the surrounding rocks of the tunnel as shown in Figure 1, with \(R\) as the ratio of pile settlement to surface subsidence. The settlement of the layer is larger than that of the pile in zone A, and zone B is close to it, while zone C shows that the settlement of the pile is less than the soil settlement.  
The present study is focused on the soft surrounding rock of shielding and the settlement of sandy pebble strata. Studies on the weak strata temperature and the earth pressure of silty clay are limited, therefore the influence of temperature on soil properties were considered [5; 6]. There are a few cases in which the model test method has been used to study the shield effect on the displacement of pile, the earth pressure and the displacement of pile and the internal force response [7]. These studies are of great significance for the design and construction of tunnel and underground engineering in coastal areas in order to determine the law of strata disturbance and the response of pile.  
The soil pressure distribution, deformation and failure law, in addition to different positions of pile internal force and the displacement of the response caused by shielded pile, are studied for the silty clay strata (according to the surrounding rock classification V and VI of railway tunnels [8]). This study provides a preliminary reference for understanding the soil deformation and pressure distribution of shield tunneling in silty-clay layers and the formation of the shield-pile system within the initial area of the layers. An analysis of the key digging factors is given.