Showing posts with label design. Show all posts
Showing posts with label design. Show all posts

Design of green roofs (inverted roof)

Another typical cross section of a green roof design.
  • Vegetation
  • Substrate
  • Drainage-, filter- and protection- layer Enkadrain
  • Roof sealing layer
  • Separating fleece
  • Heat insulation
  • Vapour barrier
  • House top / fabric

Soil reinforcement:Materials and design questions

- Possible materials for soil reinforcement
Most used:


- Main design questions:
  • What are the soil-reinforcement interaction parameters ?
  • What is the long term design strength (TLTDS)of the reinforcement ?

Extra volume in waste containment

In the construction of waste containments there is an economic advantage of using geosynthetics products.
As seen in the first picture if you use traditional clay and gravel layers in the landfill you can have about 5000 m3 of volume.

But as seen in the second picture if geosynthetics materials are used in the waste disposal area a gain of extra volume will be about 300 m3 with an increase of about 6% in the same area.

Typical roof garden sections

Below 2 typical roof garden sections. These are only to give an idea. Of course the designs change depending on the needs in the project.
The upper with conventional design. For drainage 2 nonwoven geotextile (filter fabric) layer and gravel in between were used on top of the waterproofing layer. (mineral drainage layer) Heavy and cost more to take the gravel to the roof. Bigger load on the concrete.
The below is with a geocomposite drainage layer, lightweight and easy to use. The drainage layer is only between 0.5- 1 kg depending on the material. ıt is factory made and tested material. The access water from the vegetation and soil comes to drainage layer and carried to channels.

Calculation of PVD's 3 - Kjellman formula

t = consolidation period (years)
D = diameter of drained soil cylinder (m)
d = equivalent diameter of drain (m)
Ch = horizontal consolidation coefficient (m2/year)
Uh = average horizontal consolidation degree

Calculation of PVD's 2 - Equivalent PVD diameter

  • calculation assumes PVD cylindrical and draining effect dependent on periphery
  • PVD effective periphery is 2 x width x f, where f is a correction factor allowing for:
    less favorable inflow to possible disturbance & smear effect to soil during installation

d = equivalent diameter of PVD
b = width of PVD

Calculation of Prefabricated wick drains 1

An assessment of the effect of vertical drains on the consolidation process may be made using the method proposed by Kjellman.
This method is based on the assumption that the drains are placed in a regular pattern and that each drain serves a cylindrical soil column of exactly the same length as the drain (colbonddrain) . it is assumed that the increase in vertical load is evenly distributed over the consolidation area and that horizontal layers remain horizontal throughout the consolidation process. It is been assumed
that the permeability of the cohesive soil remains unchanged throughout the consolidation period and that the internal resistance of the drain is negligible. Practical experiments have shown that although these assumptions are not always applicable, in majority of cases their influence on the ultimate results is of little significance. The exception is where drains without a "high flow" core are used for thick highly compressible strata. In such cases the internal resistance of the drain can have a substantial effect on the consolidation period.
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