# Influence of Alternating Temperature on the Effectiveness of EICP in Consolidating Aeolian Sand
## 2 Materials and Methods  
### Materials and Sample Preparation  
The sand used for the experiments was natural wind-deposited sand from the Taklamakan Desert in Xinjiang Uyghur Autonomous Region, China (located next to the G217 highway, coordinates E 78.65, N 39.87), as shown in Figure 1. To reduce the contamination of aeolian sand components by human activities, all aeolian sand was harvested from an open area 1000 m away from the highway. The gradation curves obtained from the particle analysis experiments are shown in Figure 2. The results showed that 96% of the sand grains had particle sizes between 0.075 mm and 0.25 mm, the curvature coefficient (C\({}_{\rm c}\)) was 1.06, and the inhomogeneity coefficient (C\({}_{\rm u}\)) was 2.22 (less than 5). These values indicate that the aeolian sand was poorly graded. At the same time, the natural aeolian sand permeability coefficient was 2.37 \(\times\) 10\({}^{-3}\) cm\(\cdot\)s\({}^{-1}\). The cementing materials used for this experiment to consolidate the aeolian sand included anhydrous calcium chloride, urea, urease, and distilled water. Anhydrous calcium chloride and urea were purchased from Tianjin Hengxing Chemical Preparation Co., Ltd. (Tianjin, China), with the purity of CaCl\({}_{2}\) being more than 98.0% and that of CO(NH\({}_{2}\))being more than 99.0%, respectively. Urease, purchased from Kamaishu (Shanghai) Biotechnology Co., Ltd. (Shanghai, China), with a purity of more than 99.0%, was extracted from giant beans and exhibited a specific activity of 200 U/mg at room temperature. In addition, the urease needs to be maintained at \(-\)20 \({}^{\circ}\)C to ensure a dormant state, and the urease activity achieves its peak state at 45 \({}^{\circ}\)C. Under the temperature range of this experiment (20-40 \({}^{\circ}\)C), the urease activity showed an increasing trend with the temperature. The specific chemical composition of urease and anhydrous calcium chloride is shown in Table 1.  
Figure 1: Sampling location of aeolian sand, Taklamakan Desert, Xinjiang Uyghur, China. Figure 2: Particle size distribution of aeolian sand sampled from the Taklamakan Desert, Xinjiang Uyghur. Based on the orthogonal experimental design, the solidification effectiveness of different cementing material proportions was compared, and the material mass proportions with the highest final calcium carbonate content were obtained for use in the mixing method of EICP-reinforced aeolian sand [28]. The material mass proportions are quoted in this study, and the mass of each material added in this experiment is shown in Table 2.  
Five sand column samples were prepared for each alternating temperature group. Three temperature groups with a total of 15 sand column samples were used. The mold for holding the aeolian sand was cylindrical in shape and made of high-density polyethylene, with an inner diameter of 50 mm and a height of 100 mm (shown in Figure 3). The mixing method was used in this study, which refers to pouring the cementing material into the aeolian sand at one time point and mixing it well. This method can avoid the need for frequent removal of the samples from the chamber when using the multiple injection method, which has a poor influence on the control of the sample temperature. In addition, the influence of sand particle size on temperature needs to be considered, and in order to minimize the influence of this factor, the aeolian sand needs to be mixed as uniformly as possible before the sample preparation. The sample preparation steps were as follows: According to the results in Table 2, the corresponding mass of each material was weighed, mixed, and dissolved thoroughly