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  Features

Hyson Cells with concrete


Comparison with other geocells

Conventional geocells were primarily developed for containing soils on embankments. The thin-walled Hyson Cell has particular advantage for use with concrete.

(1) Geocells made from thick plastic sheeting

Cells made from thick plastic sheeting will tend to be considerably more expensive because of the cost of using more raw materials and expensive joining techniques.

The rigidity of the walls may seem to be an asset but it is actually a liability for use with concrete fill.

  • The rigid walls will not easily deformed to give the interlock. These cells may have textured walls to increase friction to prevent blocks "punching through" but this effect is not of the same order as the keyed jointing produced by the non-planar wall of Hyson Cells.
  • Stiff walls will tend to bridge concave depressions leading to uncontrolled cracking of the slab formed by pooling beneath the cell mat.
  • The stiff cell mat may not be easily feathered into a terminating "tuck-in" beam. The consequence is a higher risk of edge damage due to undermining and subsequent unravelling.

(2) Geocells made from fabrics

Geocells made from fabrics are both floppy and porous with the following disadvantages :

  • Floppy cells have a high danger of collapse on filling with concrete. Filling must therefore be done slowly and carefully leading to very slow production. Faulty areas have to be cleared and completely re-laid. Overlooked collapsed and buried cells will almost certainly lead to subsequent failure of the job due to uncontrolled cracking.
  • Geofabrics are so permeable that they have a major use for dewatering on the mines. The cement paste may permeate and saturate the fabric. While it may at first sight seem to be an advantage to "stick" each cast block to its neighbour this is actually far from the case.
    • If the blocks are bonded together the whole advantage of having a flexible slab is lost. The concrete will crack at it's weakest point and the cracks may well be millimetres. Such cracks may propagate through the slab and lead to loss of fines from beneath the slab and ingress of water.
    • Bonded cell walls will not "breathe" and will not vent trapped water and air.

 

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Comparative tables

(1)Geocells made from thick plastic sheeting

Feature

Hyson - Cells

Geocells made from thick plastic sheeting

Factors affecting price of geocell

Raw material

Made from thin 200 plastic film.

Least expensive raw material per sq. m of wall area.

Heavy duty 500 to 2000 micron sheet.

Between twice to five times the cost of Hyson Cells raw material.

Production

Heat sealing technology. High capacity. Inexpensive to set up plant.

Ultra sonic welding. Low volumes, expensive plant

Factors affecting cost of installation

Ease of rigging large areas

Standard module is 200 m

-max practical size for handling with labour. Larger 500 m modules can be manufactured for installation with plant. Can be easily cut and joined on site. Supplied with integral laced rigging ex factory.

15 m > 2 packs. Needs special frame to hold the pack open

Ease of filling

High speed filling with high slump, self levelling concrete.

High speed filling also possible, but areas smaller as small packs entail much joining.

Speed of installation with one team

1000 to 2000 m per day

200 to 500 m per day

Weight (freight and on site handling)

40 kg (expands to 200 m)

30 kg ( expands to 15 m)

Packed volume (freight and on site handling )

0.15 m (expands to 200 m x 0.1 m)

Range of cell sizes and cell depths

Cell cavity sizes

50 mm x 50 mm to 800mm x 800mm

203mm x244 mm to 488mm x406mm

Depth of cells

50 mm to 4,000 mm (special 10,000mm)

152 to 203 mm

Opened length of 1 cell mat

1 metre to 100 metres

2.4 metre to 6.1 metres

Opened width of 1 cell mat

1 metre to 30 metres (standard 7.x 30 )

2.4 metres to 6.1 metres

Standard mat sizes

100 to 500 m (depending on application)

15 m

TECHNICAL

Load bearing

Mechanical interlock

Deformation in vertical plane is 5 mm. Blocks cannot "punch through" and limiting factor for load bearing is therefore shear strength of the concrete .

 

Impermeable walls

The walls are impermeable. The cell slab is a matrix of perfectly interlocking discrete blocks. Loads are therefore distributed across the network of mechanical joints.

Friction

A plane textured vertical cell wall has improved friction but the limiting factor for load bearing is the shear strength of the plastic . If this is exceeded the blocks can "punch through".

 

Impermeable walls

Although the walls are impermeable this is no advantage to load bearing as the plane faces give no vertical interlock.

 

Waterproofing

The concrete does not adhere to the walls. Unrestrained concrete will not crack on drying and the shrinkage will result in minute gaps between the cast block and the cell wall. In practice it has been observed that Hyson Cells canals are as waterproof as conventional concrete canals equipped with joints.

Although a textured surface encourages the cement to adhere to the walls waterproofing is likely to be similar to that of the Hyson Cell slab.

Release of hydrostatic pressure

The concrete does not adhere to the walls. Hydrostatic pressure may vent around entire perimeter of each cast block.

Similar to Hyson Cells but bonding of concrete with textured finish will lead to some degradation of the property..

Undesirable flow of concrete across cell boundaries underneath the cell mat to form an underlying slab. (The underlying slab can experience uncontrolled cracking some millimetres thick which then propagates through the cell slab)

Cells are anchored to the underlying material and drawn into intimate contact with it by means of the integral laced rigging. The cell walls are flexible and so some inaccuracy of levels can be tolerated.

Rigid cell walls will bridge any hollows thus allowing the concrete to flow underneath the cells.

Over filling of the cells to form an overlaying slab (which again leads to uncontrolled cracking which may propagate)

Hyson cells rigging supports the cells during filling and allows the cells to be struck off level with the top of the cell walls

The rigidity of the cells means that the top of the cell walls remains level during filling. These cells can also be struck off easy with the top of the cell walls

Edge termination

Cells are flexible and can be draped to follow a radius of 100 mm to 200 mm (depending on cell depth). This allows a "tuck-in"termination edge beam to combat potential undercutting edge damage.

Due to rigidity of the cells the edge termination methods are more limited, consume more material and are more costly.

Maximum incline of an embankment

70

50

(2) Geocells made from fabrics

Feature

Hyson - Cells

Geocells made from glued or stitched woven or non-woven fabric

Factors affecting price of geocell

Raw material

Made from thin 200 plastic film.

Least expensive raw material per sq m of wall area.

Between twice and three times the cost of Hyson Cells material.

Production

Heat sealing technology. High capacity. Inexpensive to set up plant.

Glueing is inexpensive but gives doubtful joining, especially in wet conditions. Stitching of a honeycomb cell matrix is labour based and slow.

Factors affecting cost of installation

Ease of rigging large areas

Standard module is 200 m

-max practical size for handling with labour. Larger 500 m modules can be manufactured for installation with plant. Can be easily cut and joined on site. Supplied with integral laced rigging ex factory.

Packs are 50 m to 100 m. They are not equiped with laced rigging and can not be easily rigged taut. enough so as not to collapse when filled with concrete. Should they collapse they are not redeemable and a costly halt in production results.

Ease of filling

High speed filling with high slump, self levelling concrete.

Liable to collapse if filled with concrete as cells are not rigid. Cells should be carefully filled individually

Speed of installation with one team

1000 to 2000 m per day

50 to 100 m per day

Weight (freight and on site handling)

40 kg (expands to 200 m)

50 kg (expands to 50m)

Packed volume (freight and on site handling )

0.15 m (expands to 200 m x 0.1 m)

Range of cell sizes and cell depths

Cell cavity sizes

50 mm x 50 mm to 800mm x 800mm

150 mm x 150 mm to 400mm x 400mm

Depth of cells

50 mm to 4,000 mm (special 10,000mm)

75 mm to 1000 mm

Opened length of 1 cell mat

1 metre to 100 metres

I metre to 10 metres

Opened width of 1 cell mat

1 metre to 30 metres (standard 7.x 30 )

1 metre to 10 metres.

Standard mat sizes

100 to 500 m (depending on application)

50 to 100 m

TECHNICAL

Load bearing

Mechanical interlock

Deformation in vertical plane is 5 mm. Blocks cannot "punch through" and limiting factor for load bearing is therefore shear strength of the concrete .

 

Impermeable walls

The walls are impermeable. The cell slab is a matrix of perfectly interlocking discrete blocks. Loads are therefore distributed across the network of mechanical joints.

Friction

A plane textured vertical cell wall has improved friction but the limiting factor for load bearing is the shear strength of the cement impregnated fabric . Blocks can "punch through"

 Permeable walls

The cement paste can penetrate and soak the fabric. Each block is therefore bonded to its neighbour. Initial load bearing will improve but the bonding will shear under increased loads.

Waterproofing

The concrete does not adhere to the walls. Unrestrained concrete will not crack on drying and the shrinkage will result in minute gaps between the cast block and the cell wall. In practice it has been observed that Hyson Cells canals are as waterproof as conventional concrete canals equiped with joints.

The walls are permeable and each block will be bonded to its neighbour. On drying the free shrinkage strain will exceed the tensile strain capacity and "uncontrolled cracks" of 1-2 mm can result. Such cracking is unacceptable for water containing structures and for road paving..

Release of hydrostatic pressure

The concrete does not adhere to the walls. Hydrostatic pressure may vent around entire perimeter of each cast block.

Saturation of the cell wall with cement paste will effectively prevent release of hydrostatic pressure until the bond is broken (whereupon failure can be expected to result due to pumping of fines through the large cracks)

Undesirable flow of concrete across cell boundaries underneath the cell mat to form an underlying slab. (The underlying slab can experience uncontrolled cracking some millimetres thick which then propagates through the cell slab)

Cells are anchored to the underlying material and drawn into intimate contact with it by means of the integral laced rigging. The cell walls are flexible and so some inaccuracy of levels can be tolerated.

The material is light weight and is not equiped with rigging. Unless very many securing anchor pegs are used the cell mat will "float"and allow concrete to flow underneath.

Over filling of the cells to form an overlaying slab (which again leads to uncontrolled cracking which may propagate)

Hyson cells rigging supports the cells during filling and allows the cells to be struck off level with the top of the cell walls

The cell walls are not supported by rigging and are liable to collapse during filling. Striking off is therefore difficult.

Edge termination

Cells are flexible and can be draped to follow a radius of 100 mm to 200 mm (depending on cell depth). This allows a "tuck-in"termination edge beam to combat potential undercutting edge damage.

Edge termination methods advised by manufacturer (if any) are not known to us

Maximum incline of an embankment

70

45

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