Disastrous Slope Failure Reconstruction project, Taoyuan, Taiwan

In the mountainous section, a landslide was happened at the slope near Kou-Bao Temple located in Luzhu District, Taoyuan City after heavy rainfall in year 2011. A slope construction with slurry trench was built up to fix the slope failure with function of draining water out; however, a more threatening landside was caused after torrential rain lashed this area for days in early 2012. The soil along the slope became so loosen that the access road was forced to be suspended.

This indicated area was near Dagu Shan Trail at the border of the town in Luzhu District, Taoyuan City. This trail which was temporarily close out played a major role to link with Linkou District, New Taipei City. Thus, it was mandatory to resume the connection with the most efficient way while the environmental friendly factors were necessarily taken into consideration.

A wrap-around reinforced earth structure (RES) was chosen to restore the slope. The RES was constructed in 4 sequential tiers up to a final height of 20m. Considering the misfunctioning of drainage, transverse drainage facilities were designed accordingly. Except the drainage in the reconstructed slope structure itself, layers of crushed stones and drainage boards were installed in order to precipitate the overflow into draining trench efficiently. At the toe of the slope, a trench was set up to transport seepage water into the drainage system. During the reinforcement construction, anti-erosion bags, permeable geotextile and backfill materials from the jobsite were auxiliary elements to build up the reinforced structure, apart from the geogrid.

Once the construction was completed, seeds grouting could be executed on the surface of the reinforced structure. Greenish landscape could be easily developed.

Issue of landslide failure was eliminated entirely after the reinforced structure with drainage system was built. Natural vegetation was an added value granted unsurprisingly by this construction.

Using the on-site soil as backfill material reduced the costs to construct and the demands to cement. Less artificial means were used without decreasing the achievement of the design and the structure.

Furthermore, the contribution in terms of low CO2 emission would be a strong point to support this 20M reinforced earth structure while compared with 20M tieback retaining wall and 12M semi-gravity retaining wall. The required construction materials for build up a traditional retaining wall generated quite high CO2 emission, 2.06~2.71 times greater than materials for a reinforced earth structure did (refer to Carbon Emission chart). As reinforced earth structure usually comes with a facing good for vegetation, the vegetation on the surface appears quite helpful to the carbon sequestration rate and makes the earth and the environment even beneficial in the meantime.