# Analysis of Bridge Tests on Sandy Overburden Site with Fault Dislocating
## 5 Conclusions  
Through the self-developed \"bridge foundation-foundation-superstructure damage\" physical modeling large-scale fault bedrock dislocation simulation test device, we conducted four tests on bedrock dislocation in sandy soil cover sites, yielding the following conclusions: \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Bedrock Displacement Mode** & **Site Type** & **Bedrock Dislocation Amount** & **The Width of the Main Rupture Zone** & **Width of Soil Profile Fractor** & **Height Difference on Both sides of** & **Avoidance Distance** & **Maximum Surface Deformation** & **Maximum** **Inclination** \\ \hline Low dip reverse fault bridge & Free field Bridge site & 2.8 m & 30 m & 50 m & 70 m & 0.92 m & 2.1\({}^{\circ}\) \\ \hline High dip normal fault & Free field Bridge site & 2.8 m & 16 m & 36 m & 5.2 m & 48 m & 1.4 m & 6.6\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Parameter table for actual site foundation cover layer soil breakthrough and rupture. 1. When a low-dip reverse fault is dislocated, an extruded shear rupture zone forms within the soil body. The presence of the bridge causes the surface rupture zone to shift to the passive disk, reducing the length and width of the rupture zone. With increasing bedrock dislocation, the range of surface deformation in the free site becomes wider, approximately 1.5 times that of the bridge site. However, the surface deformation and inclination within the bridge site are greater, about three times that in the free site. Earth pressure changes are evident only at the bottom of the soil cover in the free site, while in the bridge site, the influence of earth pressure extends more widely. The acceleration change of the soil body on the bridge site is more pronounced, especially on the top surface, where the acceleration is about four times larger than that in the center and at the bottom. 2. Under the high dip angle positive fault sandy soil cover site, a tensile shear rupture zone forms within the soil body. Due to significant changes in soil pressure at the bridge site in the middle and lower depths of the soil cover, the rupture zone at the bridge site deviates through the bridge pile foundation along the dip angle direction of the fault relative to the free site. The bridge deck plate exhibits bending deformation, and the connection with the bridge abutment shows significant damage. The acceleration of the soil layer on the upper disk is about four times more than that of the lower disk, with a more noticeable effect on the upper disk. 3. Based on the observed test phenomena and similarity ratios reflecting actual bridge project sites, we propose that, within the surface rupture zone and avoidance distance range, a simply supported beam can be used for \"fuse\" design and connected with both sides of the bridge for structural \"disconnection\". Design parameters such as surface rupture zone and maximum deformation of the bridge site can be inferred from its free site. For example, irrespective of whether it is a low-dip reverse fault or a high-dip positive fault dislocation, the width of the bridge site is smaller than its corresponding free site, approximately half of the free site. 4. During the construction of bridges across or near faults on sand-covered sites, although the presence of bridges reduces the avoidance distance and maximum surface deformation to a certain extent, it is essential to implement reinforcement measures for the soils at the bridge-bearing platforms and piles within the main rupture zones at the surface. Simultaneously, specialized structural treatments should be applied to the pile-pedestal and bridge deck-pier joints to enhance fracture resistance in the presence of fault dislocations. 5. As the construction of bridges across faults and existing bridges facing the risk of surface rupture from strong earthquakes rises, the shift from \"avoidance\" to \"rupture resistance\" is increasingly urgent.