Study on site measurement of surface movement law under shallow depth coal and vertically repeated mining

In order to study the diference between the surace movement law under repeated mining and the surface movement law of the conventional coal mining face,with the site measurements of the surface movement law of No.N1200 cal mining face in Shenmu Ningtiaota Mine ofShaanxi Coal ndustry Group,the paper compared the differences of the surface movement parameters for the overburden strata with no goaf andgoaf above the coal mining face.The related strata movement theory was applied to explain the causes of the diferences existed in the surface movement law under repeated mining.The results showed that the surface subsidence coficient of coal mining face under repeated mining was 0.877,the advance influence angle was 49.4 ,he comprehensive movement angle was 60' and the ofiset distance at a turning point was 12.5 m.incomparison with the conventional coal mining face under the similar conditon,the surface subsidence coeficient under repeated mining infuences was higher.T'he advance influence angle,movement angle and ofiset distance at a turning point were low and the horzontal movement c.eficents were same basically.