# Natural Para Rubber in Road Embarnment Stabilization
## 4 Numerical Simulation
### Model Geometry and Materials Properties
#### 4.2.2 Subsoil and Road Embankment Properties in FEM Model  
The model parameter was assigned based on the soil profile of AY.5034 (Figure 4). The soft soil model (SSM) under undrained conditions was assigned to the uppermost 7.5 m in depth with an overconsolidation ratio (OCR) = 1.2, which included the topsoil, medium clay, and soft clay layers. The strength parameters of the topsoil were cohesion \(c^{\prime}\) = 14 kPa and friction angle \(\varnothing^{\prime}\) = 25\({}^{\circ}\). Additional values for analysis were as follows: modified compression index \(\lambda^{\star}\) = 0.17 and modified swelling index \(\kappa^{\star}\) = 0.020. The medium clay (1.5 m to 3.0 m in depth) with \(c^{\prime}\) = 15 kPa, \(\varnothing^{\prime}\) = 25\({}^{\circ}\), \(\lambda^{\star}\) = 0.12, and \(\kappa^{\star}\) = 0.020 [44].  
The soft soil layer (3.0 m to 7.5 m in depth) could be divided into three sublayers, namely, very soft to soft clay 1 (3.0 m to 4.5 m in depth), very soft to soft clay 2 (4.5 m to 6.0 m in depth) and very soft to soft clay 3 (6.0 m to 7.5 m in depth). The strength parameters were determined based on the testing data at AY.5304 by using strength parameters \(c^{\prime}\) between 10 and 14 kPa and \(\varnothing^{\prime}\) = 25\({}^{\circ}\). The additional values for analysis were as follows: \(\lambda^{\star}\) = 0.10 for very soft to soft clay 1 and 0.03 for very soft to soft clay 2 and 3, and \(\kappa^{\star}\) = 0.009 for the soft soil layer [44].  
The elastic perfectly plastic Mohr-Coulomb model (MCM) was assigned for the model of underlying stiff clay to hard sandy clay, which was located from 7.5 m to 19 m in depth. The stiff clay was located between 7.5 m and 9.0 m in depth. The strength parameters with the undrained condition were obtained from the validation site with \(c^{\prime}\) = 95 kPa, the Poisson's ratio \(v^{\prime}\) = 0.25, and elasticity \(E^{\prime}\) = 19,000 kPa. The strength parameters with the undrained condition of stiff sandy clay layer (9.0 m to 10.5 m depths) were \(c^{\prime}\) = 105 kPa, \(\varnothing^{\prime}\) = 10\({}^{\circ}\), \(v^{\prime}\) = 0.25, and \(E^{\prime}\) = 21,000 kPa. The very dense silty sand (10.5 m to 12.0 m depths) and medium dense to dense silty sand (12.0 m to 15.0 m in depth) with the drained  
Figure 5: FEM model.  
condition were assigned to the FEM model with constant values for \(c^{\prime}\) = 5 kPa, \(v^{\prime}\) = 0.30, and \(E^{\prime}\) = 53,000 kPa, while the value of \(\varnothing^{\prime}\) = 40\({}^{\circ}\) and 35\({}^{\circ}\) for very dense silty sand and medium dense to dense silty sand, respectively.  
The FEM input parameters of hard clay with sand (15.0 m to 16.5 m in depth) in the analysis were as follows: \(c^{\prime}\) = 150 kPa, \(\varnothing^{\prime}\) = 10\({}^{\circ}\), \(E^{\prime}\) = 30,000 kPa, and \(v^{\prime}\) = 0.25. Hard sandy clay was the final layer that was located from 15 m to 60 m in depth. The model parameters used for the FEM analysis were as follows: \(E^{\prime}\) = 54,000 kPa, \(v^{\prime}\) = 0.25, \(c^{\prime}\) = 270 kPa, and \(\varnothing^{\prime}\) = 10\({}^{\circ}\). The modulus of elasticity and strength parameters for the subsoil layers, which were generated as a foundation, are presented in Table 3.  
Moreover, the material properties of the road embankment for the FEM analysis were established from a previous study by [PERSON] and [PERSON] [45], which analyzed a geotextile reinforced road embankment using PLAXIS 2D. The MCM with drained behavior was used for the model of a road embankment. The strength parameters were \(c^{\prime}\) = 1 kPa, \(\varnothing^{\prime}\) = 33\({}^{\circ}\), and the dilatancy angle \(\psi\) = 3\({}^{\circ}\). The additional material parameters for FEM analyzes were \(E^{\prime}\) = 50,000 kPa and \(v^{\prime}\) = 0.3. The interface coefficient \(R_{in}\) = 0.8 [46]. The material properties of the road embankment model for the FEM simulations are tabulated in Table 3.