Regionalization of land subsidence and collapse degree

According to the estimated results of ground deformation, the severity of ground subsidence and collapse in No.3 Mine can be divided into four grades (Figure 3. 14):

Fig. 3. 14 1 Second zoning map of surface deformation degree after goaf

1) The maximum subsidence value of the first-class ground is more than 8m, which belongs to the extremely severe subsidence area. This grade is distributed in three areas, one in Mopanshan area (Ⅰ1), the second in Caojiawa area (Ⅰ 2) and the third in Yuezhai area (Ⅰ 3), with a total area of about 0.8 1 1km2. Among them, the maximum subsidence value of I1area center can reach 16m, and the maximum subsidence value of I 2 area center can reach 14m. Such a large surface deformation is mainly related to the mining thickness. According to the drilling data, the second floor of 1 15 hole 1 coal thickness is 19.9m, and caving zone with larger vertical height will be generated after long arm caving, which is estimated according to the following empirical formula (Zou Youfeng et al., 2003):

Study on comprehensive management of geological environment problems in coal mines

Where: H 1 is the maximum height of caving zone; H2 is the maximum height of fault zone (including caving zone); M is the thickness of coal seam or the vertical height of roadway; α is the dip angle of coal seam (α is10); K is the rock expansion coefficient (soft clay shale 1.3 ~ 1.35, sandstone 1.5 ~ 1.6).

2) The level II ground subsidence value is 5 ~ 8m, which belongs to the serious subsidence area. This level is distributed in the periphery of the first-level area. For example, 2 # 1 coal is located in mining area II1,Yuezhai Ⅱ 2 and Jingzhigou Ⅱ 3, with a total area of 2.322km2 According to the data of 1 12, 1509 and 1707, The heights of caving zone are 14.24 ~ 200.24 respectively, and the heights of fault zones are 42.72 ~ 85.32 m, 60 ~ 120 m and 32.04 ~ 64.0 m respectively, all of which are less than the mining depth, indicating that there are bending zones in these areas, which belong to the fully mining type with incomplete caving of overlying strata.

3) The maximum subsidence value of Grade III ground is 3 ~ 5m, which belongs to the middle area of subsidence and collapse. It is mainly distributed in Nangou, Lvjiashan, Shuiquangou and 1704 near the north of Zhengzhou Mining Bureau, with a total area of about 5.875km2, and the thickness of coal seam in this area is relatively small, which is 5.7m According to No.504, No.505, No.204, 1704,15/.

4) The maximum ground subsidence of Grade IV is less than 3m, which belongs to a slight subsidence area. It is mainly distributed near the southern edge of the mine field, Bajiamiao and No.202 hole in Lvjiashan, with a total area of about 5.080km2 The thickness of coal seam in this area is between 1.6 ~ 3.3m, and the buried depth is relatively large. According to statistics No.202,113, 1309, 13 14, the average thickness of overburden is 252.7 meters.