Sustainable Slope Works

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Sustainable Slope Works
Ir K P YimGU/NP, SEB, Arch S D
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Eyesores
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Hong Kongs Slope Works

• One of the major construction activities
• Consumes energy and natural resources during
  construction and maintenance
• Publics urge for a sustainable future
• - alleviate environmental impacts
• - enhance slope appearance

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Common definition of SD

• Development that meets the needs of the present
  without compromising the ability of future
  generations to meet their own needs
• (After Brundtlands 1987 World Commission on
  Environment and Development)

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Sustainable Construction

• Construction activities whose negative impacts
  are minimized and positive impacts maximized so
  as to achieve a balance in terms of
  environmental, economic and social performance
• (After Report of the CIRC)

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Sustainable Slope Works

• Blending works with surroundings
• Minimization of disturbance to natural terrain
• Energy efficient design
• Reduction utilization of waste materials
• Protection of wild habitats
• Increase rate of return

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1. Blending Works with Surroundings General
Principles

• Ultimate goal is to achieve visual harmony
  of the man-made landforms with the existing
  surroundings by
• - maintaining a natural appearance (which is
  green most of the time) by means of long-term
  landscape measures
• - creating an architecturally appealing
  appearance that compliments with the surroundings
  by means of short-term aesthetic measures

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Minimized and Recessed Soil Nails in Soil Cut
Slopes
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Aesthetic Treatments for Fill Slopes

• Reinforced fill technology allow steeper fill
  slopes to be constructed.
• The establishment of vegetation will be affected
  by the effectiveness of erosion control mat to
  retain the seedlings and soil.
• For steep slopes, non-biodegradable erosion
  control mat with good 3-D structural integrity to
  retain the soils are preferred.

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Greening of reinforced fill slopes
Wrap-around Polymeric GeogridSlope Facing for a
60 Reinfoced Fill Slope
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Long-term Aesthetic Treatments for Rock Slopes

• Application of shotcrete with mesh reinforcement
  to rock slopes with highly fractured surface are
  necessary to provide an effective means of slope
  surface protection.
• To enhance the long-term appearance of these rock
  slopes and other existing slopes with shotcrete
  surface, creepers with successful trial records
  in Hong Kong, including Parthenocissus himalyana
  (???) and Fiscus pumila (??) can be grown.

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Instant Greening of Rock or Shotcreted Slopes

• Recently, fiber-reinforced soil treatment method
  (Geofiber) has been tried successfully in some
  pilot projects.
• Geofiber employs spraying of a mixture of sandy
  soil and continuous polymeric fibers with grass
  seedlings, forming a composite soil that is
  self-supportive.
• Geofiber has a comprehensive network of internal
  drainage and has been demonstrated to be applied
  to steep slopes successfully.

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Aesthetic Treatments for Reinforced Fill
Retaining Walls

• Precast concrete wall panels allow the
  possibility of different architectural patterns
  to give the wall a visually appealing, short-term
  appearance.
• Long-term appearance can be enhanced by planting
  either trees or suitable species of creepers at
  the base of the retaining wall to give the wall a
  green appearance.

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Long-term Appearance of a RF Wall at HKUST
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2. Minimization of disturbance to the land

• Omission of intermediate berms on high rock cut
  slopes can drastically reduce land take and
  excavation, hence, minimizing disturbance to the
  natural terrain.
• Natural terrain hazard mitigation measures (i.e.
  protective barriers against debris flows and
  boulder falls) facilitate long-term maintenance
  works and minimize the disturbance to the natural
  terrain.

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Tsing Yi North Coastal Road Cut Slope
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YAM O TUK SERVICE RESERVOIR ACCESS ROAD
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3. Minimization of energy consumption in
construction future maintenance

• Adoption of reinforced fill technique reduces the
  energy used in construction of retaining
  structures, hence, conserving raw materials
  minimizing the environmental problems created by
  pollution.
• Provision of sloping-berms along man-made slopes
  allows the drainage channels to be
  self-cleansing, hence minimize long-term
  maintenance

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TSING YI NORTH COASTAL ROAD (TYNCR) RETAINING WALL
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Embodied Energy (EE) of Construction Materials
Definition Energy used to extract and transport
raw materials, refine and manufacture them,
package, deliver and install them on site.
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Energy used by RF wall and RC wall
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Example of sloping-berm design
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4. Reduction and Utilization of waste materials

• Using excavated materials from site formation
  works for the construction of embankments
  natural terrain hazard mitigation works reduces
  the construction waste to be taken off site.
• Scrapped rubber tires can be processed for the
  construction of embankments on soft ground. With
  unit weight half of the soils, these material
  allow a very quick rate of construction without
  the need of extensive ground treatments. Using
  scrapped rubber tires also help minimizing the
  disposal of these materials into our limited
  landfill sites.

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Natural Terrain Landslide Hazard
BORED PILE
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Using excavated materials for embankment as a
natural terrain hazard mitigation measure
BORED PILE
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5. Minimization of disturbance to wildlife
habitats

• To minimize the disturbance of the natural
  terrain and the wildlife habitats along natural
  stream courses, terraced buffer zones instead of
  large concrete barriers or check dams are
  preferred.
• To restore the natural environment of the stream
  courses, the terraced buffer zones will be lined
  with stone mattress comprising cobbles and
  boulders recovered from the stream bed
  modification works.
• Create wildlife habitat (e.g. falcon net) in
  rehabilitated quarry

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Terraced buffer zones lined with cobbles and
boulders
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Rehabilitation of Quarry
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6. Increasing rate of return

• After 2 decades of intensive slope treatment, we
  are now dealing with less risky slopes.
• Under todays economic situation, increase rate
  of return of any works, be it tangible or
  intangible.
• Innovation ideas to turn slopes into asset, in
  addition to maintaining safety of slope.
• (i) generate revenue
• (ii) create recreational values
• (iii)improve environment
• (iv)promote technology
• (v) boost tourism.

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Economical Benefits

• Slope Advertisement
• Solar energy
• Wind Power

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Recreational Use

• Grass-skiiing field
• Ecological Trails

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Concluding Remarks

• Based on the concept of sustainability, a set of
  considerations was identified and had been
  adopted in some of the projects in Hong Kong.
• Visual harmony can be achieved through short-term
  and long-term aesthetics treatment.
• Ecological enhancement will often benefit both
  the economics and the environment.
• Slope works designed on the sustainability basis
  have less impact to the environment, and are more
  cost effective, and higher rate of return.

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Our Dream

• ??? More Clear Water

• ??? More Blue Sky

• ??? More Green Hills

• ?????? More Wildlife

• ???? More Healthy People

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REFERENCES

• 1.   Yim, K P, Lau, A S T, Kwok, D W Lam, A Y T
  (2002). Thoughts on Turning Slopes into Asset.
  Proceedings of the International Conference on
  Innovation and Sustainable Development of Civil
  Engineering in the 21st Century. 1-3 August 2002,
  Beijing, pp 221-224.
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• 2. Yim, K P, Lam, A Y T (2002). Hong
  Kongs Slopes Towards Sustainability. Proceedings
  of the International Conference on Innovation and
  Sustainable Development of Civil Engineering in
  the 21st Century. 1-3 August 2002, Beijing, pp
  37-40.