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.

Standards for prefabricated vertical drains (wickdrains)

ISO 12958:1999    Geotextiles and geotextile-related products -- Determination of water flow capacity in their plane
ISO 10319:1993   Geotextiles -- Wide-width tensile test
ISO 11058:1999   Geotextiles and geotextile-related products -- Determination of water permeability characteristics normal to the plane, without load
ISO 12956:1999 Geotextiles and geotextile-related products -- Determination of the characteristic opening size

Below there is a typical datasheet of a wickdrain (prefabricated vertical drain) for soil consolidation. The standards used are listed.

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.

Multifunctional geogrids

• grid embedded in nonwoven filter layers
• One-step easy installation
• Optimal interaction with the sub-grade
• High modulus, low strain (Enkagrid TRC)
• Geogrid and nonwoven geotextile together

Functions:
Stabilization+ Filtration+ Separation

What is a PVD ?

• Prefabricated Vertical Drain - PVD
• Also called as wickdrain.
• Used for soil consolidation, settlement instead of sand drains.
• Typically 95 -100 mm wide by 3 - 5 mm thick
• Synthetic core wrapped with geotextile
• The core may be produced from different polymers (PVC, PP, PE or mixtures ...)
• The geotextile jacket type can differ depending on the producer.
• There are also many core types in the market.

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.

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.

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.

Calculation of band drains (PVD) 4 - Drain spacing

1)triangular spacing standard

2)for a square grid :
D = 1.128 S

S : spacing of drains

D : diameter of the equivalent cylindrical column of soil, drained by each drain.

For more information about the calculation of prefabricated vertical drains (wickdrains) please also see other posts.

Calculation of Prefabricated wick drains 1

VERTICAL DRAINAGE DESIGNS
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.

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.

Erosion control with honeycomb structures

Honeycomb structured erosion control products has been specially designed for use on sub-bases which do not generally allow the growth of vegetation due to their geological properties. Slag heaps and rocky slopes are examples of this kind of sub-base, upon which a 10 cm thick layer of soil can be applied into the product to form the basis for the development of vegetation.
In such cases, the honeycomb structure allows the mat to be filled with topsoil, providing a lasting grip in the cascading geocells. A further major applications are slopes where the topsoil would erode, if no corresponding measures were taken to combat erosion.
These flexible geocell products are generally made of geotextile fabrics connected to each other reciprocally to form a hexagonal honeycomb structure. The resulting cells can be filled with fertile topsoil, sand, flint or gravel, depending on the specific application. The factors of rigidity and permeability are decisive criteria in the selection of the geotextile fabric used for the production. They are taken into account to ensure that the finished product can ideally fulfil the requirements of its specific application.
The number of anchoring pins of is determined by a great variety of parameters
In addition to its functional characteristics, one of the benefits is its high degree of flexibility. The geocells can follow the gradient of the slope without buckling or warping. Furthermore, the lightweight material allows quick and easy installation. The geocells are resistant to rotting and therefore stabilize the covered surfaces permanently, independent of the vegetation that has been chosen.

Reinforcement of silo foundation

The project contains the foundation of 4 silos with a diameter of 27 m each, to be used for the storage of grain. The soil had insufficient bearing capacity to prevent differential settlements under the circular loaded area.
The steel wall of the silo was placed upon a concrete foundation. The bottom of the silo consists of a circular concrete plate which is not connected to the surrounding foundation of the wall.
When the silo is filled, this could bring about some movement of the plate caused by the consolidation of the subgrade. A local designer made a design with four layers of Enkagrid TRC-20 geogrid to improve the bearing capacity of the foundation underneath the silos.
TRC-Grid reinforces the granular fill and prevents mixing of the particles of the subgrade and the granular fill during the design life.
Furthermore TRC-Grid acts as a filter around the drainage pipe. Differential settlements can occur due to consolidation or loss of bearing capacity of the underlying subsoil between the silo wall and the silo bottom plate. However, the support and the movement of the silo bottom plate should be uniform.

Retaining wall drainage with geocomposites

Behind the retaining walls we need drainage and filter layers to carry the water to the drainage holes or to the drainage pipes at the bottom.

In traditional methods we generally use gravel or sand as drainage layers.

Especially in residential areas the leakage water coming out off the holes of retaining wall doesn't wanted. It is not very good to see some muddy water and the stains of water.

Geocomposite drains are used behind the retaining walls to carry the water from the soil to the drainage pipe.

Geocomposite drainage products replaces the drainage and filter layers. So, it is better to transport to construction site a lightweight material and install it.

Geosynthetic drainage sheets should be manufactured by good quality filters to prevent clogging and also there should be a three dimensional drainage layer between the filters.

Composites for sport pitches

In artificial football pitches or other sport areas generally they need shock absorbtion layers.

There are composites especially designed as a shock absorption layer under artificial sport pitches, thereby combining a long term resilience layer with good shock absorption characteristics and drainage capacity. These products sometimes even being re-used under the renewed carpet / topping for a second life.

Geogrid with a filter layer

Kocaeli free zone project has a harbour inside the project. There is a heavy traffic of trucks. To prevent or reduce partial settlements on the roads due to the heavy truck traffic special geogrid was used.

This multifunctional geogrid delivers reinforcement, separation and filtration in one easy-install product for paved roads, parking areas, platforms and building/structure foundations. In the project it reduced the required subbase thickness.

Due to the special manufacturing method Enkagrid TRC has very low elongation properties.

It helps to reduce the partial settlements.

Beside the reinforcing Trc geogrid also provides a filter layer. So it works like a geogrid and a nonwoven .

This type of geogrids work as reinforcement, separation and filtration layers.

Basement, cellar drainage, waterproofing

In the basements of buildings generally we have moisture problems. Even we have waterproofing water may enter the building. A good waterproofing system should be supported by drainage materials.
Geocomposites can intercept incoming water and drain it away from the structure towards the collector pipe.
To use a geocomposite drain is much easier and generally cheaper than conventional drainage systems like mineral drains. Forexample you should carry a lot of gravel to the construction site or building. It is also difficult to use heavy gravel. It is also necessary to cover the drainage pipe with a nonwoven geotextile to prevent clogging.
But a composite drainage sheet with a filter bothsides and only about less than half a kilograms per square meter you can make a better drainage system. Also the inside core of the drainage sheet should be elastic and the core should have a structure to let water go easily to all directions.

A good composite drainage system:

• Keeps wet soil away from walls
• collects and removes groundwater
• Protects the waterproofing on walls
• Relieves hydrostatic pressure

Advantages of composite drains:

• Ventilates - Prevents wall sweating and fungal growth
• Light and flexible-Readily adaptable to irregular wall configurations
• Economical - No extra accessories needed (i.a. strips, special fastenings, etc.)
• Reliable and durable

The composite drains can be used as do it yourself type of applications also.