## 3 Results
### Analysis of Structural Changes in Loss Soil Samples
#### 3.2.2 Relationship Between Moisture Content and Structural Parameter  
In loess engineering, moisture content is generally considered to be a broad force that weakens and dissolves the chemicals in the soil, weakening the structural properties of the loess as the moisture content increases. Loess is particularly sensitive to water. Once immersed or even moistened, there is a significant reduction in strength and a significant increase in deformability [38; 39].  
The shear strength values of undisturbed and reshaped saturated soil samples with different moisture contents and the structural parameter of soil samples with different moisture contents are shown in Table 4, and the change trend of the structural parameter with moisture content is shown in Figure 4.  
It can be seen from Figure 4 that under the condition of controlling variables, the influence law of moisture content on soil structural properties is basically similar to that of perimeter pressure on soil structural properties, i.e., the value of the structural parameter  
Figure 4: Variation curves of structural parameter with moisture contents.  
of loess gradually becomes smaller with the increase of moisture content. The structural parameter as a whole decreases with increasing moisture content, and the lower the moisture content, the higher the corresponding structural parameter at the same pressure. The magnitude of decrease in the structural parameter is greater at lower moisture content intervals, while the magnitude of change in the structural parameter decreases significantly as the moisture content increases to a saturated moisture content (36%). This suggests that for undisturbed loess, changes in moisture content have the most dramatic effect on loess structural properties at low moisture content intervals, and that a small increase in moisture content in this region can lead to a sudden decrease in loess structural properties. The structural nature of the undisturbed loess was effectively destroyed at higher moisture contents, when the sensitivity of the structural parameter to changes in moisture content and pressure was greatly reduced.  
As a result of long-term physicochemical action, loess has developed a structure of porous and vertical joints and the formation of carbonate-based cementing material between soil particles, which not only gives it strong structural properties but also makes it particularly sensitive to water. The underlying causes of the above phenomenon are as follows. 1 The cementing material in loess is dominated by soluble carbonates, and the water in loess causes some of the cementing material between particles to dissolve, weakening the cementing effect. This resulted in a reduction in the strength of the cementitious bonds between the soil particles, and this weakening effect continued to increase with increasing moisture content, with a significant reduction in the strength of the soil samples. 2 As the moisture content increases, the bonded water film between the particles thickens. At this time, the sample may change from strong bonded water association to weak bonded water association until free water appears, the bond strength is reduced, and the thickening of the bonded water film reduces the friction between particles, which ultimately leads to the weakening of the soil samples [40]. 3 An increase in the moisture content of the soil will result in a decrease in matrix suction, leading to a weakening of the mosaic between soil particles and a reduction in the strength of the soil sample. Based on the new definition of the structural parameter, it was discovered that the reduction in strength of the undisturbed soil samples resulted in a decrease in the structural parameter, which is consistent with the test results.