# Long-Term Creep Mechanical and Acoustic Emission Characteristics of Water-Immersed Coal Pillar Dam
## 4 Conclusions  
Based on the Daliuta CMUR engineering project, this study collected coal samples from the reservoir area and conducted long-term creep mechanical behavior tests for about 180 days per specimen under both natural and water-immersed conditions. We analyzed differences in creep behavior, mechanical strength parameters, and microfracture evolution between natural and saturated coal-rock specimens, providing fundamental mechanical parameters and analytical foundations for long-term stability assessments of CMURs. Further validation, including in situ stress field monitoring and simulation, depth-dependent mechanical, seepage, and AE signature across diverse coal mining regions in Xinjiang and Shanxi, is suggested. Additionally, the generalized coal creep model considering the long-term water immersion effect is one of our further future research targets. The key conclusions are summarized below:  
1. Physical-chemical water effects significantly alter early-stage deformation mechanisms. During the initial phase (0-40 days) for immersed specimens, negative creep occurred with strain rates as low as \(-\)0.00086%/d. This phenomenon correlates with non-uniform pore compaction and elastic rebound. Water infiltration promoted the continuous low-stress compaction of partially unclosed pores, triggering localized stress release and skeletal elastic recovery, thereby causing anomalous strain retraction, which is a behavior unobserved in natural condition specimens.
2. Water immersion exerts continuous deterioration effects on coal-rock throughout long-term creep. Although steady-state creep rates under both natural and saturated conditions were similar (\(\approx\)3.0 \(\times\) 10\({}^{-6}\)/d), instantaneous unloading tests revealed a 11.4% reduction in loading modulus for saturated specimens (2037 MPa) compared to natural samples (2300 MPa). This discrepancy stems from water molecules softening mineral particles. Concurrently, due to water filling and saturation effects, the daily  
Figure 8: Creep acoustic emission characteristics of natural coal–rock specimens.  
AE event rate under immersion condition (127 events/day) was significantly lower than under natural conditions (500 events/day), indicating that water immersion suppresses AE generation and alters damage accumulation patterns.
* For Daliuta CMUR, it is recommended that actual dam loads be controlled below 9 MPa to prevent accelerated creep. Although negative creep in water-saturated coal pillars temporarily mitigates deformation, continuous elastic modulus degradation necessitates higher safety redundancy in design. Microseismic monitoring should supplement real-time stability observations, and sudden energy surges or sustained event rate increases should be treated as accelerated creep precursors, which requires emergency engineering measures.  
Conceptualization, E.Z. and M.C.; methodology, E.Z.; validation, E.Z. and Y.Z.; formal analysis, E.Z. and B.W.; data curation, Z.C. and J.H.; writing--original draft preparation, E.Z.; writing--review and editing, M.C.; visualization, Z.C. and B.W.; supervision, M.C. and Z.C.; funding acquisition, E.Z. and M.C. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project (No. 2024 ZD1004505), Beijing Natural Science Foundation (No. 8254049), the National Natural Science Foundation of China (No. 52374139), and the Fundamental Research Funds for China Academy of Safety Science and Technology (No. 2024 JBKY07 and No. 2025 JBKY05).  
Not applicable.  
The original contributions of the study are included in the article, and further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.