# The Application of Fine Sand in Subgrades: A Review
## 4 Application of Fine Sand Subgrade Engineering  
### Application of Windblowon Sand Subgrades  
There are relatively few examples of using aeolian sand for road construction abroad, and most of them were studied between the 1960s and the 1980s. Studies during this period primarily focused on material characteristics and road performance, as shown in Table 2. \begin{table}
\begin{tabular}{c c c} \hline
**Proposer** & **Treatment Methods** & **Main Results/Conclusions** \\ \hline [PERSON] [46] & Cement-modified fine sand & Cement-modified fine sand as filler on subgrade surface, with optimal cement-mixing ratio \\ [PERSON] [47] & P.P.T polymeric road-building agent & Agents improve soil cohesion, enhancing basic properties \\ [PERSON] [48] & Cement and lime-improved aeolian sand & Optimal properties and mix ratio for cement-lime-stabilized aeolian sand obtained \\ [PERSON] [49] & Cement-modified fine sand & Silty fine sand met 200 km/h railway subgrade filler specs \\ [PERSON] [50] & Cement improvement, quicklime & Combined chemical and physical improvement for suitable plan \\ [PERSON] [51] & 50\% fine sand mixed with 50\% round gravel & Solution meets K30 foundation coefficient, subgrade body porosity \\ \hline \end{tabular}
\end{table} 
Table 1: Studies on the improvement of fine sand subgrades. \begin{table}
\begin{tabular}{c c c} \hline
**Year** & **Author (Application)** & **Research Topics** \\ \hline
1963 & [PERSON] and Yoder [52] & (1) \\
1967 & [PERSON] and Riley [53] & (1)(2) \\
1967 & [PERSON] [54] & (3) \\ \hline \end{tabular}
\end{table} 
Table 2: Literature review on aeolian sand [6]. Desert areas in the western region of China are densely distributed, with aeolian sand being the most abundant and economically viable material in these regions. It is primarily used in the construction of desert roads. Domestic aeolian sand subgrade construction is mainly located in the Taklamakan Desert area of Xinjiang and the Mu Us Desert area in the energy-rich region of northern Shaanxi, dating back to the early 1990s. Construction in the eastern coastal regions commenced with the establishment of the Liaoxi section of the Beijing-Shenyang Expressway in 1999. Deserts in China are mainly distributed in the western provinces and in regions such as Xinjiang, Gansu, Inner Mongolia, Ningxia, and Qinghai [64, 65]. The natural dry density and moisture content of aeolian sand in various desert regions are shown in Table 3[66, 67]. Sieve analysis of aeolian sand from various desert regions indicates uniform sand particles and fine mechanical composition, representing a typical case of poor gradation and non-cohesiveness [68, 69, 70]. Compaction performance presents a challenge during construction processes [71]. [PERSON] [72] concluded from experiments that significant differences exist in the compaction process between aeolian sand and cohesive or sandy soils. A relatively high degree of compaction can be achieved with a moisture content of around 1%. Based on this, dry compaction can be applied to sand bases under vibratory compaction, which holds significant significance for regions with arid and low rainfall conditions, as well as for economic benefits. Factors such as impact energy, vibration frequency, ballast weight, and compaction speed are all important factors affecting compaction effectiveness. [PERSON] [73] suggested using heavy rollers with high frequency (45-50 Hz) and small amplitude (0.4-1.0 mm), with compaction speed controlled between 3 and 6 km/h, achieving a compaction degree of up to 97.7%. A summary of typical aeolian sand fill subgrades is presented in Table 4. Compared to coastal fine sand subgrades, the engineering environments for these two types of subgrades differ significantly. Aeolian sand subgrades are located in arid, low-rainfall, and