Overlying strata movement law in fully mechanized coal mining and backfilling longwall face by similar physical simulation

Fully mechanized coal mining and backfilling technology with gangue, fly ash and losses etc. changes the overlying strata movement characteristics and strata behavior law in the fully mechanized coal mining and backfilling longwall face (FMCMBLF). Based on the similar theory, a model of the overlying strata movement in FMCMBLF is established with sponge and plastic foam whose thickness ratio is 1:2 as the similar backfilling body. From the similar physical simulation, the following conclusions have been drawn: (i). The overlying strata movement develops from bottom to top as the mining progresses in the FMCMBLF and consequently, the subsidence curve of the strata assumes symmetrical bowl. (ii) No caving zone but only fissured and bended zones are found in the overlying strata herein. (iii) The subsidence velocity undergoes a changing process of “minimum, successive accretion, reduction, and stabilization,” and the overburden strata movement lasts for a long time. The test results would provide reference for further research of strata control as well as fully mechanized coal mining and solid backfilling technology.