## 1 Introduction  
Currently, countries around the world generally regard sustainable development as a strategic goal, aiming to coordinate resource utilization, environmental protection, and climate change mitigation [1]. The rapid expansion of high-speed railways (HSRs), defined by speeds exceeding 200 km/h, has become a key infrastructure development project in many countries [2]. However, the construction of HSRs inevitably generates large amounts of waste, and the accumulation of this waste not only occupies significant land resources but also poses potential pollution and environmental damage [3], presenting a severe challenge to the sustainable development of HSRs. The circular economy, as an emerging paradigm for promoting sustainable development, has gained widespread attention in recent years. The core concept of the circular economy is to create an \"industrial system designed and systematically restored or regenerated\" based on the principles of \"reduce, reuse, and recycle\" [4], aiming to minimize resource waste and environmental burdens [5]. In HSRs, the application of circular economy can improve resource utilization efficiency and reduce the environmental impact by procuring sustainable materials, maximizing material recycling, and minimizing waste generation. Additionally, the circular economy emphasizes avoiding the generation of unnecessary waste and preventing waste from being disposed of in landfills. However, the overall utilization rate of construction spoil in HSRs is still low [6,7], which necessitates the establishment of large-scale spoil disposal areas (SDAs) to store the large amounts of spoil generated, thereby supporting material recycling and reuse. Meanwhile, the large volumes of spoil stored in SDAs are typically loose and fragmented, and long-term accumulation may lead to soil erosion, water loss, and further environmental degradation, including potential landslides and debris flows. Therefore, effective monitoring and management of SDAs are crucial for mitigating these environmental impacts and achieving the goals of the circular economy. For waste monitoring, the importance of integrating 3S techniques, including geographic information systems (GIS), remote sensing (RS), and global positioning systems (GPS), is increasingly recognized. Researchers have explored their potential in monitoring areas such as olive oil mill SDAs [8], municipal open SDAs [9], mine SDAs [10], and hazardous SDAs [11]. Existing studies typically use individual 3S techniques or combinations of different techniques for various monitoring purposes, including settlement monitoring, deformation monitoring, temperature monitoring, and concentration monitoring. However, there is currently a lack of research integrating 3S techniques for monitoring SDAs in HSR projects. On the one hand, SDAs in HSRs have their own specific characteristics. These areas are primarily used for the large-scale storage of spoil generated by excavation activities during the construction stage. Environmental protection requirements are particularly high, especially when passing through ecologically sensitive regions. Close attention needs to be paid to the stability of the spoil and its impact on the soil and water environment to prevent landslides, debris flows, and soil erosion. Therefore, directly applying 3S techniques from other monitoring fields (such as municipal and mine SDAs) is not sufficient for effectively monitoring SDAs in HSRs. On the other hand, current applications of 3S techniques in SDA monitoring typically use individual techniques for monitoring aspects such as settlement, temperature, and concentration, with a lack of systematic research on the integration of 3S techniques for comprehensive monitoring. To address the research gap mentioned above, this study proposes an innovative integrated 3S framework for the comprehensive monitoring of key scenarios in SDAs during the construction stage of HSRs.