To further investigate the overburden strata movement and deformation law of coal backfill mining

a concept of"continuous curved beam" of coal backfill mining was defined based on the overburden strata movement and deformation characteristics of coal backfill mining. On the basis of analyzing relationship between overburden strata deformation and curvature

a model was established for overburden strata curvature of coal backfill mining. The curvature was proposed to evaluate the deformation characteristics of rock strata. A formula of calculating the curvature K of overburden strata was deduced to reveal the relationship between compression ratio and overburden strata curvature. Compression ratio

thickness and key strata were found to be key factors influencing overburden strata curvature according to the curvature model

meanwhile

the support length also had some effect on overburden strata curvature. Thus

the curvature theoretical model was adopted to evaluate the effect of backfill mining.According to curvature variation features of overburden strata at different layer heights

the limit curvature was proposed as the criterion to judge the fracture location of strata under different compression ratios. The critical compression ratios of immediate roof and main roof without breaking were calculated

and were basically consistent with borehole measurement.