Abstract: During the layer mining process of the thick coal seam，the roof at the lower layer generally are the caving gangues of the upper layer working face and the crushed coal falling from the upper roof affected by the upper mining disturbance，so it is unsuitable to use the combined support of bolt and cable.In most cases，the shed support with the combined single hydraulic prop is adopted to maintain the roadway stability.Especially，the open-off cut supporting with large section becomes one of the difficulties in the lower layer design.With a large section open-off cut support in Xinjiang under China Coal Energy as a case，the load concentration of artificial support structure is calculated out，according to the pressure arch theory.On this basis，the reasonable array distance of the I-steel shed beam support is determined when the I-steel shed beam reaches the standard yield strength.These provide a reference for field design and construction of the shed.

Key words: Layer mining, Large section open-off cut, The pressure arch theory, Joist steel shed, Array distance