Dong-Ah Geological Engineering Company Ltd. (KRX: 028100) specializes in civil engineering, primarily providing underground construction and ground improvement services. The company offers mechanical tunnel construction using shield, semi-shield, and tunnel boring machine (TBM) methods; ground improvement via deep cement-soil mixing (DCM), jet grouting, and soil nailing; general civil works including roads, subways, bored piles, diaphragm walls, earthworks, and pipe jacking; engineering services such as design, research, and measurement; and environmental solutions like water treatment and wastewater reclamation systems. Founded in 1971 and headquartered in Busan, South Korea, it operates internationally with projects in Hong Kong, the Philippines, Qatar, UAE, Kuwait, Vietnam, Singapore, Cambodia, and domestically in major infrastructure such as Incheon Airport Terminal 2 railway, Seoul Subway Line 9, and Busan New Port.
Recent developments include the successful indigenous manufacturing of a tunnel boring machine in 2024; securing major contracts such as a 61.6 billion won order in August 2025 and a 48.4 billion won order in April 2025; receiving 20 billion won in funding from Dover Holdings Limited and Rivendell Investments; and ongoing execution of the Hong Kong International Airport third runway expansion using marine and land DCM methods, alongside the North-South Commuter Railway in the Philippines.