Abstract: The water sump of a certain coal mine at -400 m level is located in a complicated geological structure zone with an extremely water-swellable floor.Under the functions of high tectonic stress, in-situ stress and expansion stress, the previous common support by bolt, mesh, shotcrete and cable can no longer keep the essential stability of wall rock of the sump.Based on the analysis of in-situ geological conditions and wall rock failure reasons, and in view of the deficiencies of the original support design, a full-face reinforced concrete arching method was adopted for the support of the sump's wall rock.The long distance concrete pumping technology was introduced for the first time in mine arching support, which covered the shortage of common manual arching and obtained good technical effects and economic benefits.The research results show that it is very hard to keep the stability of sump in a soft rock stratum with great expansivity only by the support with bolt, mesh, shotcrete and cable.A secondary grouting can effectively improve the wall rock's carrying capacity and the integrity of support structure while a full-face reinforced concrete arching can control the serious floor heave of roadway.

Key words: Water sump, Expansive floor heave, Concrete pumping, Arching