## 5 Conclusions  
This study aims to explore potential foundational issues that may lead to the accelerated damage of urban cement concrete pavements in seasonal frost regions. To achieve the objectives, a total of six test sites designed by CRCP and JPCP methods were selected for field evaluations. Field visual inspections, GPR surveys, DCP tests, and CHP tests were performed to assess the support and drainage conditions of pavement foundation materials. The key findings of this field study are listed below:  
1. In urban residential areas where the subgrade bearing capacity is insufficient, cement concrete pavements often suffer premature failure. Foundations with a higher content of coarse particles exhibit a higher CBR value, which can extend the service life of the pavement. Urban roads contain sewer pipelines under the pavement, which lead to less compaction of foundation materials. The less compacted foundation will result in non-uniform bearing capacity and support conditions.
2. The permeability of the foundation material with relatively fewer fine particles yields good drainage performance, which leads to a longer service life of the PCC pavement surface structure. For subgrades with poor drainage, water tends to accumulate near curbs or in low-lying areas, significantly reducing the bearing capacity of the foundation, and thereby accelerating pavement deterioration. The cracks allow water to more easily penetrate the foundation and potentially wash away foundation materials, resulting in non-uniform support conditions and accelerating the formation of cracks.
3. For the pavement design type of CRCP, the poor bearing capacity and drainage conditions of the foundation lead to cavities between the surface layer and foundation material thus yielding stress concentrations on the pavement surface, which cause the formation of pavement surface cracks.  
Methodology, C.L. and X.W.; experiment, C.L. and W.X.; supervision, S.Q. and Q.B.; validation, Y.W. and S.B.; writing--original draft, W.W.; writing--review and editing, C.L. and W.W.; funding acquisition, C.L. and S.B. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the National Science Foundation of Shaanxi Province (2022)Q-743), the National Natural Science Foundation Project (52178185), the fellowship of China Postdoctoral Science Foundation, (Grant No. 2021 MD703885), and the Fundamental Research Funds for the Central Universities, CHD (No. 300102212208).  
Not applicable.  
Figure 13: **(a)** Schematic of crack locations, reinforced bars, and cores, (B2, B3, and B4 are the labels for the core sampling locations) **(b)** location of the cracks, and **(c)** a large gravel particle in core hole B3 at site CRCP-23-B.5.  
Data Availability Statement: The data presented in this study are available on request from the corresponding author. Some data are related to research projects, and are not provided for the time being.  
The authors would like to acknowledge the guidance and support provided by [PERSON] and [PERSON] at Iowa State University. The assistance of the City of Clive, Iowa is also appreciated. The authors are also very grateful to the editor and anonymous reviewers for their valuable comments and suggestions on this paper.  
Authors [PERSON] and [PERSON] were employed by the Ningbo Communications Engineering Construction Group Co, Ltd. Author [PERSON] was employed by the Gansu Road & Bridge Construction Group Shanjian Technology Company. 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.