Harm of ground collapse in goaf

1 The existing mined-out areas of coal are located in Jingzhigou, Mopanshan and Caojiawa, which are loess hilly areas. In this area, there are many terraces and valleys except some scattered villages. Although the ground subsidence in the mined-out area is serious, compared with the relative height difference of the terrain, the subsidence is not enough to affect the macro-landform, and a large area of collapse pits and waterlogged depressions have not been formed. The direct harm caused by ground deformation is mainly the damage to residents' houses and farmland. The survey shows that in recent years, ground fissures and uneven settlement are common in the mined-out areas such as Mopanshan and Caojiawa, and many terraces are dismembered and dislocated by cracks. Under the action of rain erosion, surface sinkholes and underground tunnels are constantly developing, resulting in serious soil erosion, declining soil fertility and even inability to cultivate (Figure 3.6), and a large number of farmland is abandoned, which has caused huge losses to local agricultural production and farmers' lives.

Table 3. 1 Statistics of Ground Fissure and Ground Collapse Investigation in Caojiawa Area of Dayugou

Table 3.2 Statistical Table of Ground Fissures and Collapse Investigation in Mopanshan Subsidence Area of Dayugou

Note: The statistical data of ground fissure zone only refers to the largest ground fissure.

Figure 3.6 Cracking of Farmland in Mopanshan Area

(2) Damage to buildings

Under the influence of ground subsidence and collapse, houses, roads and pipelines located in the existing mined-out area are damaged to varying degrees, ground fissures develop, houses collapse, walls are damaged, and even indoor ground cracks (Figure 3.7 and Figure 3.8), making them dangerous buildings. As a result, five administrative villages have moved out in recent years, with an average of 150 households per year, and 880 households with 4,726 people have to move out.

Figure 3.7 Damage of Houses in Mopanshan Area

Figure 3.8 Damaged ground of original houses in Mopanshan area.

(3) Impact on public facilities

The ground subsidence and collapse of mined-out areas have brought great hidden dangers to the safety and stability of pipelines and highways. At present, there are many highways crossing the mined-out area, among which the length of National Highway 3 10 is near 1km, and the maximum settlement value is 13m m, so the highway has been repaired and strengthened many times. In addition, during the active period of ground deformation, two expressways are located in the areas with the maximum settlement of 10m and 4.5m, and the daily settlement can reach several centimeters, which is easy to cause traffic accidents and should be highly valued.