SLOPE PROTECTION WORKS AT SUBIC-CLARK-TARLAC EXPRESSWAY (SCTEX)

PROJECT BACKGROUND

Subic-Clark-Tarlac Expressway (SCTEX) is a four-lane, 93.77km expressway in the north built by the Bases Conversion and Development Authority (BCDA). SCTEX is the longest tollway in the Philippines that connects Subic, Clark, and Tarlac provinces. The expressway is linked to the North Luzon Expressway (NLEX) through the Mabalacat Interchange, and its northern terminus is at Tarlac–Pangasinan–La Union Expressway (TPLEX) in Barangay Amucao, Tarlac City.

The entirety of SCTEX is mostly laid out on embankment with some sections using cuts to traverse hilly areas. Road slopes are composed of combined cut and fill sections variably formed along the entire pavement length. Cutting hilly areas required massive earthworks to create high yet stable bench slopes along road easements. Likewise, large quantities of filling materials were used to complete embankment along low-lying areas selected as pavement path. 

Slope protection of finished grade surfaces was required along cut and fill sections to prevent erosion. Conventionally, slopes are protected using rigid concrete structure such as riprap and shotcrete. But this kind of construction is very expensive and, in some cases, may not be environmentally compatible. The client decided to use bioengineering as they believe on its effectivity against erosion while maintaining cheaper cost. 

Coconet and grass were used to stabilize the slopes. Coconet minimizes erosion by absorbing and conveying rainwater safely towards the slope bottom. It thus prevents water penetration and scouring on the surface of the slopes. Vegetation of various species was grown on the surface to provide grass cover. This bioengineering technology provides and maintain surface stability in contrast to conventional concrete protection which fails and cracks. 

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