## 2 Sampling and Methodology
### Characteristics of Loess Collapsibility
#### 2.5.2 Characteristics of the Loess Collapsible Curve under Different Initial Moisture Content  
Four sets of undisturbed soil samples sourced from Shanzhou, Mianchi, Gongyi, and Xingyang were prepared according to the methodology outlined in Section 2.3 to achieve varying water contents. Subsequently, indoor water-immersed compression tests were carried out to examine the characteristics of the collapsibility curve under different initial water contents. The results are summarized as follows:  
A critical external factor influencing loess collapsibility is the initial water content of the soil samples. Figure 5 illustrates the relationship curve between the collapsibility coefficient and the overburden pressure across various regions and initial water content levels. A comprehensive analysis across different regions reveals a negative correlation between the initial moisture content and the collapsibility coefficient. Specifically, as the initial moisture content increases, the collapsibility coefficient decreases, and saturated loess remains stable without collapsing. Conversely, increased initial water content compromises the stable structure of the loess soil under its own weight or external loads, resulting in a weakened or nonexistent collapsibility. The loess wetting curve clearly consists of two parts: a sharp growth part and a gradual stabilization part, corresponding to the above concept of initial water content and external load affecting loess collapsibility. The maximum value of the wet subsidence coefficient is 0.142 in Shanzhou Mianchi, 0.135 in Gongyi, and 0.103 in Xingyang. The wetting coefficient of Xingyang loess specimens increases relatively slowly with the overlying pressure.  
Figure 5: The curve of the collapsibility coefficient versus pressure under different initial water content (**(a)** Shanzhou, **(b)** Mianchi, **(c)** Gongyi, **(d)** Xingyang).  
2.5.3. Characteristics of the Loess Collapsibility Curve under the Same Initial Water Content  
To investigate the collapsibility of loess across four regions under uniform initial water content conditions, the loess samples with an initial water content of 6.79%--representing the highest collapsible deformation--are selected for comparative analysis.  
Upon analysis of Figure 6, it is evident that under uniform initial moisture content and overburden pressure conditions, the collapsibility coefficient of the loess is most pronounced in the Shanzhou area and least pronounced in Xingyang. As discussed in the previous paragraph, initial water content exerts a significant influence on loess collapsibility. However, even with consistent initial water content, disparate levels of collapsibility persist among the regions. The change curves of loess moisture subsidence in different regions are basically consistent with the change curves under natural water content. It should be noted that there is still a trend of slow growth of loess wetting coefficients in the four regions after the 300-400 kPa stage, which is different from the above change curves. The wetting coefficients of Shanzhou, Mianchi, Gongyi and Xingyang were 0.158, 0.127, 0.094 and 0.072, respectively. The initial collapse pressure of Malan loess in the four regions is lower than that under natural water content. The initial pressure of loess collapsibility in Xingyang is 85 kPa, and the initial pressure of loess collapsibility in the three areas of Mianchi, Gongyi, Shaanxi is less than 50 kPa. In summary, the initial water content of the soil sample has a significant effect on the collapsibility of the loess, which is basically consistent with the collapsibility of the loess plateau studied by [PERSON] (2016); [PERSON] (2017); [PERSON] (2018).  
To better comprehend the fundamental reasons for the divergence in loess collapsibility between the four regions of western Henan, further analysis of loess microstructure using techniques such as micro-electronic scanning mirrors is warranted.