Abstract: Tetraena mongolice maxin plays an irreplaceable role in ecological system stability and environment protection as the constructive species in desert areas. By investigating and analyzing on the growth characteristics of Tetraena mongolice maxin roots, this paper puts forwards that Tetraena mongolice maxin fibrous root is prone to be broken for the surface deformations and cracks induced by underground caving mining. And mining changes the water retention property of the soil in the region of root system, which affects the growth and reproduction of Tetraena mongolice maxin. In this paper, the calculating formulas of surface tensile strain are deduced and the characteristics of surface cracks are analyzed based on mining subsidence theory. Then the corresponding relationship between mining thickness and surface tensile strain are concluded. Based on the equivalent height theory of backfilling mining, the corresponding relationship between equivalent mining thickness with surface fracture development and broken roots of Tetraena mongolice maxin is established. Namely, roots growth of Tetraena mongolice maxin remains unaffected when the surface tensile strain was less than the average ultimate tensile strain of roots. Therefore, goaf backfilling is an effective mining method to protect the Tetraena mongolice maxin.

Key words: Tetraena mongolice maxin, backfilling mining, surface cracks, equivalent mining height；strain