Maccaferri’s Hybrid MSE structures including Terramesh and Paralink were selected by the Indonesian Ministry of Public Works to suite as soil retaining structures in the Toraja airport project.
The Tana Toraja Regency is located in the South Sulawesi province of Indonesia. Yearly the Tana Toraja Regency hosts thousands of tourists coming to admire the breathtaking landscapes, the biodiversity of the region as well as the rituals of the Toraja ethnic group. The Indonesian government has chosen to pursue the goal of developing the touristic activities in the area.
Until now, the only way for travelers to approach Tana Toraja was via a dangerous 8-10 hour journey, starting from the city of Makassar. For this reason, it has been planned to build a touristic airport in Tana Toraja with a multi-year project starting in 2014 and coming to end in 2017.
The new airport runway is 2 km long and approximately 210 m wide, suitable for ATR type aircraft. The presence of hills and spurs clashing with the runway area determined the necessity of massive cut and fill heart works in order to obtain the required runway level.
Thus, the filling soil has to be retained with technically suitable and economically feasible structures. It is worth to note that the maximum embankment height to be retained is almost 40 m. The main technical constraints have been: the high seismicity of the area, the rain encountered every year and the presence of clay shale foundation soils.
Clay shales are originally dry and hard showing high shear strength, but when they absorb water during the unloading process, they can rapidly turn to soft clay with extremely low shear strength. For this reason, excavation and construction operations required exceptional care and adequate planning to minimize the exposure of the foundation soils to weathering agents. The evaluation criteria for choosing the suitable retaining structure have been: permeability, flexibility, construction schedule, and overall cost.
Eventually Maccaferri’s hybrid MSE structures—Terramesh+Paralink— have been evaluated to be the most suitable solution for the runway construction. In October 2015, the construction of the first Paramesh retaining structure using Maccaferri products started. It has a maximum retained height equal to 25 m, distributed in 5m- high berms. The berms are realized using both Terramesh System and Green Terramesh elements (60 degrees). The primary reinforcements are Paralink geogrids with an ultimate tensile strength equal to 300 kN/m. The design was carried out using Maccaferri’s internal Limit Equilibrium Method software Macstars W, then with the commercial FEM software PLAXIS.
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For further technical information, download the Case History present on the Indonesian website.