Living Protection and Integrated Use of Cultural Sites from the Perspective of Functional Synergy: The Case of the Duogongcheng Site in Chongqing

Mountainous military heritage represents a distinct form of cultural landscape facing compounding threats from environmental degradation and anthropogenic pressures. Conventional conservation models often adopt fragmented approaches, leading to limited long-term sustainability. This study proposes and empirically validates a novel Tri-Dimensional Symbiosis (TDS) framework integrating historical authenticity, ecological resilience, and community vitality to support more holistic heritage conservation. Employing a mixed-methods design—including GIS-based spatial analysis, multi-criteria assessment, Terrestrial Laser Scanning (TLS), and field surveys across twelve Southern Song Dynasty defense sites in Chongqing, China—the study generates three key findings: (1) Approximately 73% of sites face significant pressure from incompatible development (p < 0.01). (2) At the Duogongcheng pilot site, micro-interventions reduced structural deformation by 41% (from 8.3 mm to 4.9 mm, p < 0.001). (3) Community-cooperative tourism increased local household income by 28.5% (p < 0.01) within one year. The study introduces the Symbiotic Interface Index (SII), a robust quantitative tool (CR = 0.07 < 0.1), to assess and optimize synergies between preservation, ecology, and social participation. This framework bridges disciplinary divides, offering a scalable model to transform military heritage from passive relics into active catalysts for sustainable regional development. These findings contribute actionable, policy-relevant strategies for reconciling heritage conservation with socio-ecological resilience in rapidly urbanizing mountainous regions globally.