Shopping mall roof garden drainage system

Laying geocomposite drainage sheets at the roof garden of a shopping mall construction. Special attention should be given to to direction of overlap considereng the backfill direction.

Traditional drainage layers

To compare with the geocomposite drainage products let's remember the traditional drainage layers :)

Traditional drainage layers are made of graded granular material

• the granular filter prevents penetration of fines into the drain (Filtration)
• the granular core transports the water in the plain of the filter (Drainage)

Composite drainage for lost shuttering

Some geocomposite drainage products may be used as lost shuttering also.
The drainage composites which have a cement milk-proof layer on one side, made of PVC layer (nonwoven coated with a PP film) could be used for lost shuttering.

Application
1 side PVC geocomposite drains can be used as lost shuttering when installed against the foundation wall of the adjacent building, a bored pile wall, a vertical excavation face or a rock face, permitting to cast the fresh concrete immediately against the drain.

Reasons for drainage

Reduce and eliminate hydraulic pressure against structures:

• increase stability of geotechnical structure in case of a retaining wall
• reduce the weight on the structure in case of flat roofs
• increase stability of cover layer in case of capping of a landfill
• accelerate consolidation of soils in case of Prefabricated Vertical Drains (PVD’s)
  

Prevent leakage through a subsoil wall

• cellar walls
• underground structures

Basement drainage of a congress hall building construction

Geocomposite drainage sheets can also be used in higher depths. Photographs here shows some applications of drainage composites. They are ready to backfill. The backfill around the composites should be made very carefully because of the height. Direct flow of gravel and backfil materials may tear or damage the drainage materials.

This drainage composite was placed on the waterproofing layer.

For house basement drainage please check other drainage posts.

Roof garden tips

Now it is spring and you may want to prepare a green roof. You know roof garden does not mean a garden on the roof only. It may be top of an underground garage or top of a underground structure.

An important thing is not to forget the drainage core of the drainage sheets or layers with a nonwoven (may be woven but non woven is cheaper) filter fabric.

The ready made drainage products already have filter on them. But you have to wrap filter on the drainage core. Otherwise the soil, gravel or etc may go inside the drainage layer and block the drainage or at least decrease the amount of water to be drained.

Drainage sheets are used to remove excess water.

On the drainage layers you may use a water retention layer depending on where you live.

For more information on green roof solutions check our roof garden section for all posts of this subject.

Capping system for waste areas

Instead of using traditional (mineral) products if we use geosynthetics materials for the capping of waste disposal areas we may have extra storage. So, to use geosynthetics has economic advantages against the traditional products. Also it is more easy to use geosynthetics (geotextiles, geomembranes, geogrids, geocomposites, geomats).

On the picture above you can see a simple comparison of “traditional” mineral- and “geosynthetic” capping of landfills.

As seen the mineral seal and drainage section have much thickness than the geosynthetics drainage and geomembrane seals.

Geocomposite drainage materials are used both for gas and water drainage.

Tunnel drainage with geocomposites

In TAG motorway project a geocomposite drainage product was used. The project was a cut and cover tunnel.

To protect the waterproofing and also for drainage Enkadrain drainage sheets were used. All the tunnel covered carefully. The backfill around done carefully.

composite geosynthetics are also used inside the bored tunnels.

Drainage sheets on basement walls

On the basement walls of a big business area with many buildings an elastic special drainage product was used. Drainage sheet called Enkadrain was elastic with 2 filter fabrics on both sides and has a drainage core between them.

It was easy to cut and put it on the waterproofing. Liquid bitumen type waterproofing was used. So also the overlaps were glued with that waterproofing product.

After the job they backfilled carefully.

Using geocomposite drains ar much easier than filling the area with gravel.

Drainage- retaining wall-geocomposite sheet drain

To prevent the water pressure behind the retaining walls a drainage layer is generally needed. The convetional method is to use gravel behind the wall and leave some holes on he wall. The water leakage from these holes causes bad view . And sometimes the gravel may be expensive with the transportation costs.



One of the easiest methods is to use geocomposite drainage sheets.



In this project seen on the pictures a geocomposite drainage sheet have been used. The drainage material was made of a 3 dimensional drainage core which lets water go to any direction and a special filter which is resistant to clogging.



The drainage layers were installed vertically by simple methods. They nailed.



The most important thing is you should pay attention to the overlap direction. Because if you start backfilling with the help of a heavy machine like an excavator the overlaps should look to the opposite side of backfilling.



If you backfill from the front (directly on the drain) there is no problem.

What is drainage?

Drainage is the removal of excess water from land by means of surface or subsurface conduits, pipes or other systems.

Horizontal usage of wickdrains (prefabricated vertical drains-PVD)

I think the first project that the wickdrains have been used was in Belgium, in the Brussels Metropolitan Transport system. The second may be the Eskisehir light rail tram system.

Actually the main application of PVD's are in soil consolidation. But in this tram project it was used to collect the leakage water to prevent not to pass the lower section to cause rusting. So, if it is a good drainage material and if it works also horizontally why not we use horizontally.

Colbondrain (a Dutch made PVD from Colbond geosynthetics bv.) was laid horizontally, and to collect more water they made some loops upwards.

Lost shuttering - drainage

Some geocomposite drainage sheet materials can be used as lost shuttering in many applications. An elastic drainage material should be chosen to be used on the piles with a lot of curved areas. Enkadrain CK maybe one of these drainage materials.

Enkadrain CK has a cement milk-proof layer on one side, made of brown or black-colour PVC (there are also other types)
Enkadrain CK can be used as lost shuttering when installed against the foundation wall of the adjacent building, a bored pile wall, a vertical excavation face or a rock face, permitting to cast the fresh concrete immediately against the drain.

Waste disposal area

This pictures shows layers of a typical waste disposal area.

• Clay base
• Drain pipes
• drainage layer
• sump pump
• membrane (geomembrane) liner
• leachate collection
• waste
• levelling layer
• filter layers
• gas vent
• seepage drain
• membrane liners (top)
• drainage layer (top)

Some detailled information about waste capping will be sent in next posts.

Findrains to stabilise water saturated river banks

Geocomposite prefabricated findrains can be used to stabilise the water-saturated banks of various drainage ditches.

The 1 meter high drainage screens can be installed at 1.25 m from the crests of the banks to intercept the groundwater flows.

Hydrostatic pressure causes horizontal displacement of the entire bank.

The geocomposite findrain contains an 80 mm perforated collector drain.








The prefabricated findrain can be installed in the 0.40 m wide trenches easily.

Roof garden system

In the design of roof gardens designers should choose the design system depending on the local weather and plant conditions. Because the climate and the plants are different in al the world. Especially the drainage layer is important for the plants.

Below another roof garden design is shown.

On the concrete substrate there is a waterproofing membrane and a root barrier on it. But in some designs it is possible to lay a nonwoven geotextile to protect the waterproofing layer and a protection concrete could be casted. So, the root barrier may not be used depending on the type of plants.

For the drain layer a geocomposite drainage layer can be used. Because it is made of light materials. Otherwise you should use gravel for drainage and it will cause a load of about 150 kg/m2 on the building. So, it is much better to use a composite drainage layer.

The drainage layer should have a good filter layer to prevent clogging.

On the drainage layer landscaping architects may use a water retention layer.

You can use a prevegetated mat and soil as growth medium on the top.

This system may be used as a good drainage system.

Parking deck- drainage

Dealing with the ever increasing number of cars requires both a creative and practical solution to growing parking problems. The construction of parking areas on the roofs of buildings proves to be an efficient option. This system should cover the primary objectives: prevent infiltration of rain water, protect the waterproof layer and provide a sufficient stability allowing vehicles to drive and park. Also aspects of aesthetics, maintenance and repair costs need to be considered. Securing a well designed drainage system is a major function that can be fulfilled by geocomposites. Due to the expected traffic loads, high compression resistance is one of the main factors to be taken into account in the choice of a suitable product.

Drainage mats, which have all proven themselves in the past and provide outstanding performance in many parking deck projects worldwide. As the number of applications has grown, so has the number of criteria for selecting drainage mats. From a combination of pressure resistance, water discharge capacity, slope, filter stability and other factors, can effect to choose the right product for each specific project. For more information on drainage mats like Enkadrain and their applications.
Typical roof construction
1. Concrete roof
2. Protection layer
3. Impermeable layer
4. drainage material (mat)
5. Sand/gravel 2-7 mm, 6-15 cm
6. Pavement layer, 6-12 cm
7. Interlock improvement by sand

What is drainage? Why do we drain?

What is drainage?

Drainage is the removal of excess water from land by means of surface or subsurface conduits, pipes or other systems

Why do we drain?

Drainage is needed to prevent the build up of hydrostatic pressure against or on top of buildings or civil engineering structures, causing structural overloading, humidity and leakage problems.

long planters-drainage

If you have long planters, or some green areas in your balcony or terraces you may need a drainage layer in your planter to drain or to direct the water to drainage pipes. For this purposes you may use some prefabricated drains made of a drainage layer and filtre covered around it.

Even you may use the prefabricated vertical drains like colbonddrain horizontally.

Road edge drainage-findrain

Water in road construction weakens the substructure and can have disastrous effects on the structure as a whole. Dynamic loads from road traffic generate a pumping effect, drawing water from the subsoil up into the road structure. Varying water table levels undermine the stability of the base course material and can cause cracking right up to the road surface. This is a case for geosynthetic drain screens which intercept water and drain it off safely into collector pipes. The ideal is a system that is quick to install over both long and short distances. For this purpose, prefabricated findrains were developed. This drain screen can be used with a wide range of different drainpipes, draining off water quickly to the main collector, thereby securing the stability of the entire structure. Prefabricated Findrain can be dug into the sub-soil or be laid in narrow trenches.