# Analysis of Mining Waste Dump Site Stability Based on Multiple Remote Sensing Technologies
## 2 Study Area and Dataset  
### Study Area  
The Anqian iron mine is a large open pit mine, operated by the Ansteel Group Cooperation, with an annual total stripping capacity of 31.4 million tons, 13 million tons of iron ore and 8 million tons of ore processing. It is located in Anshan city, in the Liaoning province of China, which is marked with a red star in Figure 1a. There are three dump sites around this open pit, including Xudonggou, Yabaling and Xidabei. The mining waste is transported to the dump sites and piled up by trucks. Our study area, Xudonggou, located to the east of the open pit, is the oldest and most unstable dump site amongst them. As shown in Figure 1b, the dashed cyan line indicates the ridge line of the local topography and the mining wastes are generally piled up on the northern slope of the hill. Therefore, the structure of the Xudonggou waste dump can be categorized as having a side-hill fill structure. At dumps with this kind of structure, the instability is generally located on the north-facing slope, including the northeast and northwest. Therefore, the north slope of the Xudonggou dump site is generally an area of interest and where continuous monitoring is conducted. Since the waste rock of the Anqian open pit mine has been dumped in Xudonggou for decades, the lack of stability of the north slope has become a threat to the safety of the mine as the dumping volume increases. It was closed due to the significant volume of dumping. The Xudonggou dump site reached a height of about 164 meters. In 2009, a landslide occurred at the dump. After the landslide event, two platforms were established along the slope, as depicted in Figure 0(b). Platform 1 is on the lower part of the slope and has a width of approximately 25 meters. Platform 2 is on the upper part of the slope and has a width of about 10 meters. The dump's slope gradient is approximately 32 degrees. Since two mining tailings transport pipelines and some local residents are located below the dump, landslides or debris flow in this area could be disastrous. Therefore, continuous monitoring of the Xudonggou waste dump is of great importance for the safety of local residents and their properties. Figure 1: Detailed information of the Xudonggou dump site. (**a**) Shows the location of Xudonggou (highlighted with a red star), which is in Anshan city in the Liaoning province of China. (**b**) A Google Earth image of the Xudonggou dump site, in which the red lines indicate mining tailings transport pipelines, the orange lines represent the two platforms along the slope, and thirteen ground measurement points are marked with yellow triangles. The dump site is mainly composed of a mixture of fragmented rock and loose top soil, see Figure 2. The rock comprises old metamorphic and mixed granites from the Archaea to the early Proterozoic period. Hard rock mass (e.g., low-grade magnetite quartzite, amphibolite, granulite and mixed granite) and soft rock mass (e.g., chlorite schist, quartz schist and phyllite) are both piled up in the dump. The hard rock bodies can withstand large shear forces without deformation, landslides rarely occur here. On the contrary, the soft rock bodies are generally plastic, which have low shear strength and deform easily. In addition to the rock mass, fine-grained sand and silt are also found in this dump. According to their particle size, the sediments can be categorized into gravel (>2 mm) and sand (0.0625-2 mm). The sand can be further categorized into very coarse sand (1-2 mm), coarse sand (0.5-1 mm), medium sand (0.25-0.5 mm), fine sand (0.125-0.25 mm), and very fine sand (0.0625-0.125 mm). The materials with a particle size smaller than 0.0625 mm can be categorized as silt or mud [41]. Among these materials, the water permeability of silt and fine grained sand is relatively poor due to the small particle size. Therefore, water remains in these small particles after rainfall, resulting in aquifer layers in the dump site.