# Durability-Aimed Design Criteria of Cement-Stabilized Loess Subgrade for Railway
## 1 Introduction
investigate dynamic compressive stress characteristics and related influencing factors in the permafrost site along Qinghai-Tibet Railway [13]. [PERSON] et al. presented a full vehicle-track-ground coupling model to evaluate the dynamic response of subgrade due to high-speed trains [14]. [PERSON] et al. compared the dynamic responses of the earth structures constructed using stabilized cinders and traditional geomaterials [15]. [PERSON] et al. conducted the dynamic triaxial tests on cement- and lime-improved loess specimens to study the cyclic shear strain threshold and critical dynamic stress [16]. [PERSON] et al. established a new track-multilayer ground model to investigate railway subgrade dynamic responses induced by moving train load [17]. Moreover, dynamic responses of high-speed railway and heavy-haul railway were studied by some scholars [18; 19; 20; 21; 22; 23; 24]. In China, [PERSON] et al. studied the subgrade design indices of improved soil and found that the cumulative deformation rate of stabilized soil was less than 0.5% when the strength of improved soil was 5 times the critical dynamic strength of filling [25]. Based on theoretical calculation \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**The Grade of Railway**} & \multirow{2}{*}{**Design Speed (km/h)**} & \multicolumn{2}{c}{**7-Day Unconfined Compressive Strength**} \\  & & **Saturated with Water (kPa)** \\ \cline{3-4}  & & **Subgrade Bottom** & **Embankment below the Subgrade** \\ \hline Passenger and freight railway, & Ballast track & 120, 160 & \(\geq\)350 (550) & \(\geq\)200 \\ Inter-city railway & Ballastless track & 200 & \(\geq\)350 (550) & \(\geq\)250 \\ \hline High-speed railway, & Ballastless track & - & \(\geq\)350 (550) & \(\geq\)250 \\ Heavy-haul railway & - & \(\geq\)350 (550) & \(\geq\)250 \\ \hline \hline \end{tabular} Note: The contents in brackets refer to the strength value of stabilized soil considering freeze–thaw cycling.  
\end{table} 
Table 1: The strength requirement of stabilized soil in China. and field measurement data, the strength design criteria of filling can be 250 kPa of the top surface of the subgrade bottom and 125 kPa of embankment below the subgrade bottom when the design values of dynamic stress are 50 kPa and 25 kPa, respectively, and the actual design criteria are 416 kPa and 208 kPa because of the differences between field and laboratory, which is basically consistent with Table 1[26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36]. As for train loads, [PERSON] et al. studied the fatigue stability of cement-stabilized soil under a cyclic load of the train [37]. [PERSON] et al. pointed that the selection and design of filling are closely related to fatigue performance, which can avoid empirical errors [38]. [PERSON] et al. studied the fatigue performance of fiber-cement-stabilized soil and found that the fatigue performance of cement-stabilized soil-doped fiber was improved [39]. As for environmental factors, the effects of wet-dry cycling and freeze-thaw cycling on loess and stabilized loess were studied [40; 41; 42; 43; 44; 45; 46]. [PERSON] et al. investigated the characteristics of unconfined compression strength and void distribution of lime-flyash loess by means of a series of experiments under freeze-thaw cycling or wet-dry cycling [47]. Besides, [PERSON] et al. studied the reduction law of the antierosion ability parameters of PP fiber-reinforced loess under wet-dry cycling and freeze-thaw cycling [48]. [PERSON] et al. established a compacted loess reduction model that comprehensively considers the influencing factors [49]. [PERSON] et al. studied the influence of cement dosage and water content on the compressive strength of cement-stabilized soil under wet-dry cycling and found that cement dosage is the decisive factor to affect the durability of wet-dry resistance of cement-stabilized soil [50]. [PERSON] et al. studied the mass change of cement-stabilized soil under wet-dry cycling [51]. [PERSON] et al.