## 5 Conclusions  
Monotonic triaxial tests were carried out on frozen clay soils under three confining pressures \(\sigma_{3}\) (\(\sigma_{3}=200\) kPa, 700 kPa and 1200 kPa). The effect of remolding water content \(w\) was investigated with three typical \(w\) values (optimum water content \(w_{\rm opt}=27.5\%\) as well as its dry side \(w_{d}=19\%\) and wet side \(w_{w}=35\%\)). In addition, the microstructures of the tested samples were examined through MIP and SEM tests. The results allowed the following conclusions to be drawn.  
The mechanical behavior of frozen clay soils exhibited distinct remolding water content \(w\)-dependent characteristic governed by microstructural evolution. The shear strength \(q_{\rm max}\), resilient modulus \(E_{0}\) and cohesion \(c\) increased as \(w\) increased, which was driven by the progressive increase in ice cementation within the shear plane. Notably, a threshold  
Figure 15: Comparison of the current testing results with the previous studies [16; 17; 37].  
\(w\) value was identified at \(w_{\rm opt}\) = 27.5%, which marked a structural transition and divided the variation of \(q_{\rm max}\), \(E_{0}\) and \(c\) into two zones. When \(w\leq\) 27.5%, clay aggregate dominated the soil fabric and ice cementation was limited within the clay aggregate, resulting in subdued growth of \(q_{\rm max}\), \(E_{0}\) and \(c\). As \(w\) increased beyond 27.5%, the soil fabric transitioned into a homogeneous matrix of dispersed clay particles, where increased \(w\) facilitated the interconnected ice cementation network, thereby accelerating the enhancements of \(q_{\rm max}\), \(E_{0}\) and \(c\).  
Regarding friction angle \(\varphi\), it decreased with \(w\) increasing due to lubrication effect exerted by the growing ice. In addition, since this lubrication effect was enhanced at clay particle-dominated fabric (\(w>\) 27.5%), the decreasing rate of \(\varphi\) was larger at \(w>\) 27.5%. As for volumetric parameters (Poisson's ratio \(v\) and dilation angle \(\psi\)), both exhibited an increasing trend as \(w\) increased. This can be attributed to the more involvement of solid ice into the soil structure, which enhanced the horizontal deformation and volumetric expansion.  
Conceptualization, S.Q.; methodology, S.Q. and J.L.; validation, J.L., W.M. and J.W.; formal analysis, S.Q., J.L. and W.M.; investigation, S.Q., J.L. and J.W.; data curation, J.L. and J.W.; writing--original draft preparation, S.Q., J.L. and W.M.; writing--review and editing, H.B. and S.W.; supervision, S.Q.; project administration, S.Q., J.L. and W.M.; funding acquisition, S.Q. All authors have read and agreed to the published version of the manuscript.  
This work was financially supported by the National Natural Science Foundation Youth Fund of China (52108295), Young Teacher Training Program of Beijing University of Civil Engineering and Architecture (Grant X24023), and Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture (Grant JDYC20220811).  
Not applicable.  
The data presented in this study are available from the corresponding author upon request.  
Author [PERSON] was employed by the company Ningxia Road & Bridge Construction Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.