Abstract: To understand the ground behavior is essential for surrounding rock control and dynamic disaster prevention，the evolution law and causes of strong ground behavior in wester Ordos Coalfield are researched through in-situ investigation in Hongqingliang Coal Mine. Then，the overlying strata structure of“soft main roof + conglomerate key strata”is established as well as the corresponding analytical calculation model. Based on the theory of gangue compression and deformation in goaf，the supporting load parameters of the lower collapsed rock mass to the conglomerate layer are determined and the expression of the fracture step distance of the conglomerate layer is derived. The results show that under impact by the movement of the overlying hard and thick gravel layer，the stoping range from 300 m to 340 m experiences the strong ground behavior in the mining face. Large area drainage of support and large area of coal wall spalling are the main forms of strong mine pressure，with the maximum spalling depth up to 1.5 m. The caved rock also supports the conglomerate strata，affecting the bending and sagging process. The evolution process of the conglomerate strata can be divided into three stages，i.e. untouching gangue stage，continuous deformation stage and conglomerate breaking stage. The theoretically calculated caving span of conglomerate strata is 306.9 m，and the field investigation is 320 m. The results can provide a reference for advanced support design and ground pressure control under weakly cemented strata condition.

Key words: Strong ground pressure, Roof bedding, Gangue compression, Weakly cemented strata, Strata movement