# Impact of Mining Disturbance on Highway Sustainability:
## 3 A Case Study  
### Overview of the Investigation Region  
The Aleksinac coal and oil shale deposit occupies the central part of a basin between the South Morava and Moravica rivers. The basin spans approximately 30 km in length along its main axis and 10 km in width. The northern part of Aleksinac town and the settlement of the Aleksinac mine are located in the southernmost part of the deposit, with Highway E75 (A1) Belgrade-Nis (Serbia) passing over the southwestern section. Underground coal mining in the Aleksinac mine has a long history, dating back to early 1878. According to the depth of the coal seam, the deposit belongs to the group of mines with a greater exploitation depth, ranging from 300 to 750 m. The primary coal seam trends in the N-NW and SE-SE directions within the eastern part of the Aleksinac syncline. Its thickness increases from south to north, ranging from 2 to 6 m, with variable dip angles between 30 and 50\({}^{\circ}\). The coal seam's roof consists of shale, while the floor is composed of sandstone. The bituminous shales accompanying the main coal seam hold significant reserves and are crucial raw materials in the Aleksinac basin, with a thickness ranging from 40 to 60 m (Figure 4). The main reserves of coal and oil shale lie within the Aleksinac Syncline. The displacement of the deposit increases with depth. Some unique mining blocks with continuous coal seams are located at higher horizons, while in the deeper parts of the deposit, they are displaced and fragmented by scissor faults into several smaller blocks, which are treated as separate excavation fields. The pronounced tectonics of the deposit has significantly influenced the manifestation of underground pressures and the stability of mining chambers. The physicochemical properties of the working environment are relatively unfavorable, as areas with significantly lower roof strata and floor strata strength compared to coal prevail, which greatly limits the application of mechanized mining systems. The roof rock massif consists of impermeable rocks (marl, oil shale, clay, and clayey sandstone), so apart from tectonic fault zones, there was no water inflow into the mines. Figure 3: Curves of horizontal displacements and deformations: 1—horizontal displacements for critical subsidence trough; 2—dilatation for critical subsidence trough; 3—dilatation for subcritical subsidence trough. In the formerly active coal deposits in the Aleksinac mine, the dominant geological features are layered tilted structures, with pronounced tectonic deformations, resulting in irregular shapes of limited exploitation areas and potentially short mining field and block lengths with frequent changes in the direction of the strike and dip angle of the layers. These phenomena are a result of complex post-orogenic tectonics in the deposits. During the operational period of the Aleksinac mines, six pit plants were active, with the most significant being Logoriste, Dubrava, and Morava, all interconnected. These plants were situated northwest of the Aleksinac town, approximately 3 km away [85]. All mines were classified as methane mines and categorized into I-III degrees of methane hazard. The average sulfur content bound in the coal was 4%, which contributed to its high self-ignition tendency. The Morava Pit, based on its distinct morphological and tectonic characteristics, was divided into the Northern District and the Southern District. In the Morava Pit, three mining horizons were developed, with an elevation difference of 120 m, from which coal was extracted: Horizon I (k-210 m), Horizon II (k-330 m), and Horizon III (k-445 m). The main shaft was located approximately in the middle of the Morava Pit and extended to the level of Horizon II (k-330.5 m) with accompanying infrastructure. In the Southern District, three primary horizons were developed: Horizon I (k-210 m), Horizon II (k-330 m), and Horizon III (k-280 m). The mining and geological conditions in the Morava Pit were highly complex.