Environment monitoring in coal mines is an important application of wireless sensor networks (WSNs) that has commercial potential. We discuss the design of a Structure-Aware Self-Adaptive WSN system, SASA. By regulating the mesh sensor network deployment and formulating a collaborative mechanism based on a regular beacon strategy, SASA is able to rapidly detect structure variations caused by underground collapses. A prototype is deployed with 27 Mica2 motes. We present our implementation experiences as well as the experimental results. To better evaluate the scalability and reliability of SASA, we also conduct a largescale trace-driven simulation based on real data collected from the experiments. Categories and Subject Descriptors C.2.1 [Computer Communication Networks]: Network Architecture and Design – Distributed networks; Wireless communication. General Terms: Algorithms, Design, Measurement Keywords Wireless Sensor Networks, Structure Monitoring, Underground, Coal Mine