Drawing mechanisms for top coal in longwall top coal caving (LTCC): A review of two decades of literature

Abstract This review details the state of art in research on top coal drawing mechanisms Longwall t op c oal aving (LTCC) by examining relevant literature over last two decades. It starts with an introduction brief history and basic procedures LTCC. The framework mechanism, concepts, some theoretical models LTCC are detailed sect. mechanism. authors note that T d rawbody (TCD), b oundary (TCB) r ecovery atio (TCRR) key factors B ody– oundary– (BBR) system has been classic for 20 years. modified Bergmark–Roos model, which considers effects supporting rear canopy, flowing velocity coal, its shape factor, is optimal characterizing TCD. A 3D model to describe TCB thicknesses seam roof strata reviewed. In physical testing numerical simulation, tests simulations classified ease bibliographical review, conclusions regarding mechanism presented discussed elaborate illustrations descriptions. deflection TCD noted, caused canopy. inclined always induces a larger TCD, also observed it. sequence interval TCRR reviewed, where long found lead significant loss coal. Its behavior distribution presented. Sect. practical applications mines 4 summarizes 10 cases improved due guidance final section provides summary work here open questions. Prospective investigations highlighted give researchers promising issues future