Abstract：The collapse of hugely-thick conglomerate stratum (HTCS) over longwall top coal caving (LTCC) affects its safe production. Taking the coal face extremely-thick coal seam and its overlying HTCS in Gengcun coal mine as the engineering background, the whole process of deformation movement of HTCS over the coal face was studied with similar simulation test. The results showed that: (1) With the coal mining, the whole process of deformation movement and collapse of HTCS was divided into ones in the lower and in the upper conglomerate stratum based on the characteristics of the fractured field of HTCS. There was trapezoidal caving body when the lower conglomerate stratum was firstly fractured, while the surface deformation was controlled by the upper conglomerate stratum fractured. (2) When the coal face advancement was stopped, there was obvious time effect on the evolution of the fractures in HTCS. (3) The parameters of deformation movement of HTCS were obtained. The first caving interval of the lower conglomerate stratum was 650. 0 m, the periodic caving interval was 175. 0 m, and the first caving interval of the upper conglomerate stratum was 825. 0 m. The surface subsidence coefficient was 0. 267. The conclusions provided a technical support for LTCC under HTCS in Gengcun coal mine.

Keyword：extremely-thick coal seam;longwall top coal caving;hugely-thick conglomerate stratum;deformation movement;fractured field;first weighting;