The evolutionary model of construction land serves as a fundamental pillar in national spatial development and planning research. However, previous studies have overlooked the "climbing" mode of construction land on three-dimensional terrains. To address this issue, utilizing elevation data and land use data from 2010 to 2020, this study employs slope analysis, intensity analysis, spatio-temporal transformation, and PLUS model to elucidate the spatial expansion process and driving forces of urban construction land in Chongqing from both two-dimensional and three-dimensional perspectives. The findings indicate that: (1) From a three-dimensional topographical standpoint, between 2010 and 2012, construction land gradually expanded towards low-slope areas, whereas between 2012 and 2020, it progressively extended into high-slope regions. (2) Regarding land type conversion patterns, the shift from arable land to construction land demonstrates a systematic inclination, while other transformations exhibit absolute or relative tendencies. Conversely, the conversion from construction land to arable land also displays a systematic pattern. (3) Since 2010, the growth process of construction land has transitioned from slow-equilibrium to rapid-disequilibrium with an expanding spatial disparity. (4) Most areas maintain relatively stable spatial conditions without significant jumps or transitions observed. (5) The expansion of construction land in Chongqing is primarily influenced by terrain, river, tunnel, rail transit, and other factors. The outcomes of this study can provide scientific foundations and decision-making references for rational planning in similar cities characterized by mountainous landscapes intersected by rivers.

To clarify the transformation patterns and driving mechanisms of the explicit and implicit morphology of rural settlements in peri-urban areas of large mountainous cities in Southwest China, this study examines the central urban area of Chongqing. Using land-use, point-of-interest (POI), socio-economic and digital elevation model (DEM) data from 2008 to 2024, we constructed an evaluation system for explicit and implicit rural settlement morphology. Kernel density estimation, the Mann–Kendall test and the moving t-test were used to identify morphological evolution, while the coupling coordination degree model and structural equation modeling (SEM) were applied to examine coordination relationships and driving mechanisms. The results show that: (1) during the study period, explicit morphology showed continuous contraction, whereas implicit morphology exhibited fluctuating improvement and polarized differentiation, indicating an overall gradual transformation; (2) no statistically significant abrupt changes were detected in either morphology, while temporal changes in coupling coordination divided the process into three stages—stable coordination, intensified imbalance and weak recovery—reflecting structural adjustment; (3) the coupling coordination degree declined overall, shifting from primary coordination towards near imbalance and indicating an uncoordinated transformation characterized by advanced contraction of explicit morphology and lagged improvement of implicit morphology; and (4) SEM results indicate that transportation infrastructure is the core driver of morphological transformation, with a significant positive effect on explicit morphology and a significant negative effect on implicit morphology. Natural factors positively support both morphologies, socio-economic factors exert negative or weak effects, and public services and real estate negatively affect explicit morphology but significantly promote implicit morphology. These findings provide a scientific basis for optimizing the layout and improving the functions of rural settlements in mountainous cities.