## 3 Conclusions  
This study employed a combination of indoor confined compression tests, scanning electron microscopy (SEM) imaging, and PCAS software ([[http://matdem.com/index.asp?](http://matdem.com/index.asp?)]([http://matdem.com/index.asp?](http://matdem.com/index.asp?)) lg=cn) to analyze the microstructure of the loess samples before and after collapse. The investigation revealed the following key insights into the microstructure and collapsibility mechanisms of Malan loess in different regions of western Henan Province:  
1. Loess collapsibility in western Henan manifests a decreasing trend from west to east. Shanzhou loess possesses the highest collapsibility among the four regions, with a collapsibility coefficient of approximately 0.15, classifying it as a strongly collapsible loess. Conversely, Xingyang and Gongyi loess demonstrate weaker collapsibility, with a coefficient of around 0.05, indicative of medium collapsibility.
2. The initial water content of soil samples significantly affects loess collapsibility. A negative correlation is observed between the initial water content and the collapsibility coefficient across the four regions. This implies that the collapsibility gradually diminishes with increasing initial water content, and saturated loess does not exhibit collapse behavior. Even when the initial water content is consistent across the four sampling sites, variations in loess collapsibility persist, and the observed trends remain largely consistent with those under natural water content conditions.
3. The intensity of collapsibility of Malan loess in different regions is affected by the interaction of microstructure and internal and external factors. The differences of the pore size, the arrangement of particles, the contact form between particles and the arrangement of pores in the Malan loess are the fundamental reasons for the difference in loess collapsibility in different regions. When there are large pores, overhead pores, point particle contact forms and unstable pore arrangement in Malan loess, the collapsibility will be higher than in other Malan loess.  
In this paper, the mechanism of collapsibility and microstructure change of undisturbed Malan loess in western Henan is studied by means of indoor immersion-compression tests and electron microscope scanning. It is of great significance to improve the construction safety and geological disaster prevention in the loess area of western Henan. However, due to the limitation of time and distance, the sampling area of Malan loess is reduced. In future research, we will sample and analyze the Malan loess in more areas. At the same time, the accuracy and professionalism of the characterization technology will be further improved.  
Y.W.: Conceptualization, Methodology, Software, Investigation, Formal Analysis, Writing--Original Draft; Z.H.: Supervision, Visualization, Writing--Review & Editing. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the Key research and development Project of Henan province (Nos. 221111321500).  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare no conflict of interest.