## 4 Long-Term Settlement Prediction Analysis  
To explore the long-term settlement patterns of high-embankment roadbeds, this section focuses on the construction of a high-embankment roadbed in the context of the Chu Yao Expressway in Yunnan, specifically the section from K67+380 to K69+183.967. As shown in Figure 6, a typical cross-section located at K68+948.243 is selected for analysis. Numerical simulations of long-term post-construction settlement are conducted using ABAQUS 2016 finite element analysis software. ABAQUS is a powerful general-purpose finite element software with a rich set of built-in constitutive models suitable for geotechnical materials. These include models such as the Mohr-Coulomb model, extended Drucker-Prager model, and others. ABAQUS can  
Figure 5: Curve of data variation for different layer thicknesses. Figure 6: A schematic diagram of a typical cross-section ABAQUS analysis model. automatically generate self-weight stress fields, perform seepage-stress coupled analysis, and conduct saturated and unsaturated flow analyses. In this segment, the highest point of the embankment exceeds 50 m in height, with a total length of 1803.967 m. The roadbed fill material consists of crushed or weathered red bed soft rock, and the construction process follows the procedures described in Section 2, resulting in a soil-rock mixed fill of red bed soft rock after compaction. To ensure the quality of the roadbed construction, adjustments are made to the moisture content of the fill material during the construction process. Trials are conducted to determine the optimal moisture content to guarantee compaction quality, and strict control measures are in place to manage post-construction settlement. The underlying red bed soft rock foundation has a relatively minor impact on roadbed settlement and is assumed to be uniform. Given that the Mohr-Coulomb nonlinear elastic model is widely used in geotechnical calculations, this model is an incremental elastoplastic model that determines the failure envelope by employing shear yield functions and tensile yield functions, ensuring that the tensile stress flow rule is associated while not being correlated with shear flow. Based on the on-site testing by the construction unit and preliminary geological investigation by our research team, the Mohr-Coulomb model parameters are as shown in Table 3.  
In the ABAQUS finite element analysis software, considering that the creep time scale of the red bed soft rock is on the same order of magnitude as the loading rate, it is necessary to simulate the coupling of creep and plasticity. For this purpose, the ABAQUS 2016 software includes a built-in time hardening and Drucker-Prager coupled creep model. Referring to the formula principles provided in the ABAQUS user manual [21], the introduction is as follow. When the applied stress on a material remains essentially constant and considering the time-hardening characteristics, the equivalent creep strain rate can be calculated using Equation (1). \[\overline{\epsilon}^{\sigma}=A(\sigma^{cr})^{n}t^{m} \tag{1}\]  
where \(\overline{\epsilon}^{\sigma}\) is the equivalent creep strain rate, \(\sigma^{cr}\) is the equivalent shear creep stress, and \(A\), \(n\), and \(m\) are material parameters used to describe the material's creep behavior. The equation can be integrated over time to yield Equation (2). \[\overline{\epsilon}^{cr}=\frac{A}{m+1}(\sigma^{cr})^{n}t^{m+1} \tag{2}\]  
According to the definition of time hardening, to ensure the stress invariance characteristic during the creep process, it is necessary to divide the time history into several stages and assume that the stress remains constant within each stage, then solve it segment by segment. Therefore, when considering the influence of previous creep on subsequent creep, \(\overline{\epsilon}^{\sigma}\) can undergo sudden changes while \(t\) remains constant. The plastic yield surface uses a linear Drucker-Prager yield surface with a meridian (sublinear) function as given in Equations (3) and (4). \[F=t-ptan\beta-d=0 \tag{3}\]