SUN L, LIU R Y, LIU Z Y, et al. Experimental study on the mechanical properties of foam filling materials for the roof of ultra-high gob-side entry in thick coal seams[J].Journal of Henan Polytechnic University(Natural Science) ,2026,45(2):140-147.

doi:10.16186/j.cnki.1673-9787.2025080030

Received:2025/08/19

Revised:2025/11/11

Published:2026/01/28

Experimental study on the mechanical properties of foam filling materials for the roof of ultra-high gob-side entry in thick coal seams

Sun Long1, Liu Ruyuan2, Liu Zhongyi1, Liang Bo1, Wei Jinping2, Wei Sijiang2

1.Xin’an County Yunding Coal Industry Company， Yimei Group， Luoyang  471800， Henan， China；2.School of Energy Science and Engineering， Henan Polytechnic University， Jiaozuo  454003， Henan， China

Abstract: Objectives To improve resource recovery rates and alleviate the tension in mining succession， the experimental study on the mechanical properties of foam filling materials for the roof of ultra-high gob-side entry in thick coal seams was conducted. Methods To verify the adaptability of the foam material， experimental methods were employed to study the influence of factors such as height-to-width ratio and loading rate on its mechanical characteristics. Results The results indicate that， under a constant loading rate， the bearing capacity of the foam material gradually decreases as the height-to-width ratio increases. Conversely， with a constant height-to-width ratio， the bearing capacity gradually increases with the loading rate. Based on the complete stress-strain curve， the loading process of the foam material can be divided into three stages： In the initial loading stage， the working resistance of the specimen increases sharply， representing a brief linear-elastic stage. As loading continues， stress increases slowly with strain， entering the plastic platform stage where the curve shows a clear linear characteristic. Stage III is the densification stage， where specimens with larger height-to-width ratios exhibit a significant reduction in bearing capacity， displaying characteristics of softening and structural failure. Graphite polystyrene foam material exhibits notable elastic aftereffect. After the initial loading， it rebounds by 50% to 80%， demonstrating strong deformation-yielding capacity and rebound-bearing performance. Conclusions Combining the engineering geological conditions of the ultra-high roadway in Yunding Coal Mine and based on the porous foam model and the theory of effective extension of anchor cables， it is concluded that foam material with a height-to-width ratio of 0.5 to 1.0 possesses strong bearing capacity and high compression modulus. It exhibits characteristics of strong initial deformation resistance and structural stability， enabling it to adapt to large deformations of the roadway roof and sides and meet the need to eliminate gas accumulation space. It is thus the preferred material for filling the roof of ultra-high roadways.

Key words: ultra-high roadway; graphite polystyrene foam; height-to-width ratio; mechanical properties; flexible backfilling