In order to solve the problem of support-strata worsening induced by improper supporting in top-coal caving working face,the role of equilibrium jack in adaptability of 2-leg shield support is studied.

By analyzing the questions showed in four-leg shock top-cave support,considering the better adaption of two-leg shield support for coal seam conditions,after a mount of demonstration,I design this two-leg low-position shield top-caving support,which is a new kind and further opens a new adaption situation for hydraulic support.

9 seam of Xingtai Mining Area,the paper analyzed the selection and application of the four-leg shock support hydraulic powered coal caving supports and hydraulic two-leg shield supports in each mine of Xingtai Mining Area base on the top coal caving technology in the recent years.

By calculating the load-carrying ability,the angle between the canopy and the shield,and the stroke of the stubilising ram,the peper makes a detailed study of influences of the connection position dimensions on performances of two-leg shield supports using computer simulation analysis, and lays the theoretical foundation for designing the rational connection position dimensions.

Balance ram is a key component of a two-leg shield support.

Taking a two-leg shield support as an example,this paper presents the theory of the shield supporting ability areas.

Analysis about base cracks of sublevel caving hydraulic supports;

It has spreading meaning of sublevel caving fully-m echanized coal winni ng technology This paper introduces the existing problem in the working process o f sublevel caving hydraulic support and the key technology about model selection again,experiment situation,the effect and benefi