NPA geocell for a railway line repair in a permafrost region Type D geocell, and layers below were reinforced with Type C geocell. Both NPA geocells were perforated, 6-inches (150-mm) high and had 13 inches (330 mm) between seams. The properties of the geocells used are given in Table 1. The nonwoven geotextiles had a grab As the access was limited, the work needed to be completed with a limited amount of construction equipment-whatever could be transported to the site by available means. Even the daily commute for the construction crew from the nearest camp in Gillam on road-rail vehicle was six hours round-trip. tensile strength of 205 pounds-force (911 N) and 299 pounds-force (1,330 N) with 50% elongation on grab. The woven geotextile had a grab tensile strength of 200 pounds-force (890 N). Nonwoven geotextiles were used on top of subgrade. Construction methods Photographs and videos of the damaged area were made available but not the survey of other engineering data available for the design. An aerial survey was conducted to assess the extent of the damage and required repair work at the washout locations to resume rail traffic. It was assessed that the project would be a linear construction, and access to the next location would be available only after completing work at the preceding location. The designers reached the first damaged site by rail and walked to the next locations to access the damage and check the suitability of the design and construction methods. As the access was limited, Properties Material Wide-width strength at yield Cell height of geocell Distance between weld seams Coefficient of soil-cell friction efficiency Coefficient of thermal expansion Brittle temperature Long-term plastic deformation at 65°C (load 6.6 kN/m) Dynamic (elastic stiffness) modulus at 30°C TABLE 1 Properties of NPA geocell used in the design 18 Geosynthetics | June July 2021 Type C geocell Polymeric nano composite alloy 19 kN/m 150 mm 330 mm 0.95 <135 ppm/°C <-70°C 3.00% >775 MPa 22 kN/m 150 mm 330 mm 0.95 <135 ppm/°C <-70°C 3.00% >800 MPa the work needed to be completed with a limited amount of construction equipment-whatever could be transported to the site by available means. Even the daily commute for the construction crew from the nearest camp in Gillam on road-rail vehicle was six hours round-trip. There was limited space to work in the repair locations, as the construction team was told to work within the railway rightof-way. Transporting heavy equipment that could be accommodated within the width of the railway line was out of the question. The construction team followed the geosynthetic installation procedures per the manufacturer's installation guide, and experience-based compaction methodology was applied for compacting the granular fill at the subballast and layers below. The lower layer of the granular fill was compacted to the possible extent to protect the permafrost layer. As there was no facility to do compaction testing, ruts developed by the 4-ton (3.6-tonne) compactor were used as an indicator of the required degree of compaction. A maximum rut of 0.5 inch (12.5 mm) under the roller wheel was considered as equivalent to 95% compaction for upper layers. Twelve passes of the compactor were made to meet the minimum compaction criteria at each location. Figures 4-8 Type D Geocell