Based on Resolution No. 411 of the Government of Mongolia, which aims to improve the quality and standards of public transportation and enhance accessibility, it was decided to construct a high-capacity public transport system “Metro” in Ulaanbaatar, the capital city of Mongolia, between 2024 and 2028. The system is intended to meet international standards and requirements while reflecting national characteristics and aligning with the fundamental interests of the citizens. Within this framework, the Capital City Governor’s Office selected “DOHWA ENGINEERING” LLC to provide services for the development of the feasibility study, design and detailed planning, as well as international project management and consultancy services.

“Buur Khurs” LLC, under a subcontract agreement dated September 15, 2024, with “DOHWA ENGINEERING” LLC, carried out geotechnical field investigations along a 17.7 km metro alignment as part of the feasibility study stage. The investigation works were conducted between September 15 and December 18, 2024.

The planned metro alignment extends for 17.7 km across Ulaanbaatar, starting from Tolgoit Railway Station located in the 20th khoroo of Songinokhairkhan District in the western part of the city, and continuing eastward along the main road to Amgalan Market in the 10th khoroo of Bayanzurkh District.

Field investigations were carried out using 10 drilling rigs (UGB-50M, UGB-50M-1VS, URB-2A-2, and SPT-LC), under the supervision of Consulting Engineer J. Battsetseg. A total of 10 field teams were deployed, each consisting of a geotechnical engineer, drilling master, assistant driller, and welder. The works were performed in accordance with the Mongolian standard BNbD 11-03-21. Dry casing drilling methods were applied in loose soils, while fluid-assisted drilling methods were used in rock formations. In accordance with the technical requirements provided by “DOHWA ENGINEERING” LLC, 40 boreholes with depths ranging from 13.5 m to 30.0 m were drilled along the alignment, along with an additional 2 boreholes at the depot site, totaling 1,180 linear meters of drilling.

During drilling, Standard Penetration Tests (SPT – ASTM D1586) were conducted at 1.5 m intervals in the boreholes using a 63.5 kg hammer. Pressuremeter tests were also performed at 15 locations.

To determine the physical and mechanical properties of the soil, a total of 362 samples were collected during drilling. Additionally, 15 bulk samples were taken to conduct CBR and Proctor tests to determine bearing capacity, maximum dry density, and optimum moisture content. Laboratory testing was carried out at accredited soil laboratories (MNS/ISO 17025), including the central laboratory of “Buur Khurs” LLC and supporting laboratories of “Buur Khurs” LLC and “Ecohydrogeo” LLC, as well as at “Ecotech Project” LLC. The following standards were applied:

Natural moisture content – ASTM D2216

Soil density – MNS 2143:2000

Grain size distribution – ASTM D422

Hydrometer analysis – ASTM D422

Specific gravity of soil solids – ASTM D854

Atterberg limits – ASTM D4318

Proctor compaction test – MNS ASTM D1557:2002

CBR test – MNS ASTM D1883:2002

Shear strength – MNS 2435

Consolidation test – ASTM 2487

In addition, 21 groundwater samples were analyzed at the chemical laboratory of “Engineering Geodesy” LLC, and soil chemical analyses were conducted on 20 samples at the laboratory of “Nart Shuun Consulting” LLC. The results of these analyses were incorporated into the study