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Lightening the load for civil engineering and geotechnical applications

Rail

Highways

Coastal

BRIDGES

Waterways

LANDSCAPE

DRAINAGE

Civil Engineering | Leca Geotechnical Fill 速

CONSTRUCTION

Introduction Leca® LWA is a ceramic lightweight aggregate produced by expanding selected clays; glacial clays tend to contain most of the essential properties allowing expansion when heated to their optimum. Once treated, the excavated clay is passed through a rotary kiln and fired to a temperature of approximately 1150°C. This process expands the material 4 to 5 times its original volume creating ceramic pellets with a cellular inner structure. Leca® LWA was first produced in Scandinavia in the 1930s for the production of lightweight blocks, it was soon discovered that the insulating properties of the material could be of benefit to failing highways and railways throughout Scandinavia and in 1958 following many years of testing Leca® LWA was accepted as a proprietary fill material in the Scandinavian countries. The raw material selection and production of Leca® LWA is strictly controlled to ensure a uniform, high quality product that is structurally strong, stable, durable and inert in addition to being lightweight and insulating. Today Leca® LWA is used in many applications such as Geotechnical Fill, Masonry Blocks, Horticultural Blends, Filtration and Bio-filtration.

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Geotechnical

Grading

Thermal Conductivity

Leca® LWA is produced in the form of round ceramic granules with a porous cellular

The practical thermal conductivity may vary from 0.10 to 0.15W/mK depending

inner structure. The grading for most Geotechnical applications is 10-20mm.

on grading, compaction, humidity level and type of technical application.

Density

Durability

Leca® LWA 10-20mm dry density ranges between 220kg/m3 – 325kg/m3.

Leca® LWA is totally inert; it contains no harmful substances or gases and is completely neutral. Leca® LWA’s resistance to chemical attack is comparable to

Resistance

that of glazed tile, glass or other ceramic material.

Unlike other granular loose material Leca® LWA offers a frictional resistance without any cohesion. The 10-20mmR grade has an internal angle of friction of typically 37° (standard shear box tested) and a design strength of 100kN/m² due to the rigidity of the rounded pellet.

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4 The main benefits of Leca® LWA in Geotechnical applications are:

• 85%* less bulk density • 75%* reduction of horizontal earth pressure to retaining structures • Reduced settlement periods and increased stability • Superb insulating and free drainage properties • Resistant to extreme temperatures, moisture and chemical attack • 100% inert and contains no harmful substances or gases • Reduced delivery vehicles – up to 100m³ per load • Speed of site installation – up to 16 times faster production* * on average when compared to traditional fills

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5 Leca® LWA - lightweight fill for a variety of civil engineering applications:

• Lightening the loads on bridge abutments • Reducing Earth Settlement • Providing Efficient Drainage • Protecting and insulating service pipework • Alleviating pressure above natural voids or culverts • Stabilising Slopes • Lessening the load behind retaining walls • Void infill

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Applications Since 1958 Leca速 LWA has proven to be a viable solution for: -

Rail

Highways

Coastal

BRIDGES

Waterways

LANDSCAPE

DRAINAGE

CONSTRUCTION

Plus: Filtration & Bio-filtration, Horticulture, Hydro-culture and Motor test track Safety Stops

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General Fill

Embankment Construction When used in most embankment designs Leca速 LWA will provide immediate cost advantages however, Leca速 LWA within embankments over weak and compressible soil deposits or underground voids will make those savings considerable when compared with traditional methods generally used.

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General Fill

Reducing Settlement The ability to reduce settlement of an embankment when incorporating Leca速 LWA can offer huge benefits; reducing timescales from years to a few months and even, in some instances, eliminate settlement periods altogether. Construction of embankments over weak and compressible soil deposits, where the loading of the embankment causes soil consolidation and settlement, is common.

Depending on the height of the embankment, the depth of the weak soil deposit and the consolidation properties of the soil strata, total settlements can be very deep and problematic in terms of road evenness, function and durability of the road construction. In the most difficult cases, various combinations of soil strengthening techniques are available, for example, preloading, vertical drainage and deep stabilisation with piles all of which are time consuming and costly to install. By lightening the embankment with Leca速 LWA, subsoil strengthening and lengthy settlement can be reduced or even avoided altogether.

Figures A and B give example of bunded and un-bunded Leca速 LWA filled earth embankment constructed above weak and compressible subsoil with marginal settlement expected. By lightening the embankment with Leca速 LWA, subsoil strengthening and lengthy settlement can be reduced or even avoided altogether.

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West coast mainline embankment widening, Shap Next

General Fill Reducing Settlement

9 (Continued)

Using Leca速 LWA on large scale cut and fill operations and construction on soft soils or bad ground can overcome stability problems, reducing the risk of landslide and deformation. Used in road embankments, Leca速 LWA exerts much lower horizontal earth pressures compared with other backfill materials, helps improve stability and reduce the need for counterfill. When widening existing carriageway or rail embankment, the weight of the newly constructed fills can often result in the new surface settling lower than the original surface and could pull the existing surface out of level.

Leca速 LWA has an installed bulk density of approximately 20% of that of general fill materials and will considerably reduce settlement of the road or rail carriageway, both immediately and in the long term. Widening and replacing existing carriageways is also simplified by using Leca速 LWA with no specialist techniques necessary.

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General Fill Load Compensation In areas prone to mining subsidence or where ground conditions contain natural

By extracting a volume of existing soil from beneath the new construction, the

sub-formation voids, drainage, culvert or tunnels and there is a danger of collapse,

equivalent volume of Leca® LWA replacing that soil will reduce the load on the sub-

expensive techniques such as load transfer are often considered. However, using

formation by four times. By using Leca® LWA extraction can be kept to a minimum

Leca® LWA can eliminate these costs and considerably lighten the load to provide

in order to achieve nil settlement.

similar benefits to those when used in weak soil areas.

Figures C and D give example of minimized and equalized load embankments

When constructing over weak underground voids or soils with low bearing capacity,

constructed with Leca® LWA using the load compensation method.

the load compensation method may be considered using Leca® LWA.

P=P1+P2

P1 P P2

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General Fill

Slope Stability Leca® LWA is a lightweight material with open voids even when compacted. This characteristic provides high drainage capacity and together with a very low density will greatly assist in reducing the risk of bearing capacity failure and increase the stability of the side slopes.

Leca® LWA is extremely lightweight making it very cost effective to transport

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Efficient Drainage Efficient drainage of the structural layers of the road build up can prevent loss of load bearing properties caused by water and ensure a good load bearing capacity throughout the road life. Using free draining Leca 速 LWA as a structural material within the road build up will intercept the percolating water and water rising by capillary action from the sub-formations and direct the rising water away from the upper construction layers to improve the load bearing capacity.

Carriageways in cuts that extend below the natural level of the groundwater, frost

Maintaining levels within any foul or surface water drainage system can be difficult

damage and loss of load bearing capacity can also be reduced by forming drain

when the drain runs across a soft soil site. Leca速 LWA can be used as a light weight

trenches filled with Leca速 LWA at both sides of the road, along which the water

pipe surround to reduce the pressure to the underlying soils and minimize the

is led away. Used within the carriageway drainage, Leca LWA will help filter and

likelihood of irregular settlement.

速

increase microbiological breakdown of pollutant run off from fields and highways.

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Structural Fill

When used against retaining walls, Leca® LWA will reduce the weight acting on the rear of the structure by at least 75%, in comparison to traditional fill materials. In figure 1 the ‘comparing pressure distribution diagram’ indicates that backfilling with Leca® LWA (A) rather than conventional sand or gravel (B) reduces the earth pressure on a 5m high wall by 75%.

CONC

RETE

This reduction in weight can avoid potential sliding, overturning, slip and tilting or bearing failures and enables savings by increasing spacing between buttressing walls and reducing structural dimensions. The bulk weight of the wall can also be reduced and more cost efficient, attractive materials can be used in place of costly, unattractive structural concrete. Using Leca® LWA will minimise the differential settlement between piled bridge abutments and the embankment fill. As it is a free draining material, Leca® LWA has the added advantage of eliminating the need for rear wall block drainage.

WALL

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Dickens Heath Apartments and underground car park, Solihull

Stoke Road Footbridge, Milton Keynes

Structural Fill

(Continued)

The ‘pull out’ resistance of Leca® LWA makes it an ideal solution for reinforced

Leca® LWA is used extensively to reduce vertical loading. Structures such as

soil retaining walls. Particularly when constructed over weak sub-soils or voids,

underground parking, tunnels or roof garden benefit greatly from the reduction

this method has been proven to cut overall construction costs considerably.

in pressure and avoid additional costs of strengthening. Being light weight and round in nature, Leca® LWA can be transported and placed more easily than that of traditional fill in these difficult to access areas.

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Protecting Services

Surrounding utilities and drainage carried within bridge beams with Leca速 LWA is a lightweight, simple to install alternative to that of sand traditionally used to support and insulate these services. The added benefit of using the lightweight round granules of Leca速 LWA as a pipe surround is that there is little danger of any damage to pipelines during backfilling and the likelihood of damage from settlement or over-loading is reduced.

There is little danger of any damage to pipelines during backfilling

Westwood access road and highway improvement, Wigan BACK

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Quay Construction and Maintenance When constructing quays, soft ground conditions often call for the use of lighter fills to guard against slide or deformation which can damage structures. A number of solid berth structures have been successfully built over recent years using Leca速 LWA. It can be used to an advantage in many quay designs such as sheet pile, sheet pile cell and caisson structures and is also used as fill replacement in solid berth structures when quayside waters are dredged to greater depths. The stresses and strain of a fluctuating tide to a retaining structure can also be reduced with 10-20mm Leca速 LWA limiting horizontal pressures from the material being retained.

With deep compaction layers and speed of installation when using Leca速 LWA de-watering is kept to a minimum and the void filled in a fraction of the time compared to using traditional fills. By depositing the aggregate directly into place from a boat equipped with its own offloading gear, exceptionally fast progress can be made with 250-300 cubic metres per hour quite achievable. The additional advantage in this location is one of an environmental nature. Leca速 LWA is a completely natural product, is an inert and stable material with no risk of leachate seepage in to the surrounding waterway.

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Other Uses

Sports Field Drainage Over compacted soils can inhibit healthy root development. Mixing Leca® LWA with soil will not only ensure over compaction does not take place, it will also assist with the balance of air and water to soil required to promote healthy vegetation on:

Leca® LWA can be used as a structural soil by increasing the Leca® LWA to soils mix for overspill car parking or grassed emergency vehicle access.

• Lawns • Golf Courses • Sports Pitches • Tennis Courts • City Parks & Landscaping

Football fields with artificial turf can be used throughout the year providing all weather training facilities and because of better durability artificial grass can be used more frequently than natural grass fields. In these instances Leca® LWA is used for both efficient drainage and frost insulation and can reduce excavations and minimise both transport and installation costs.

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Walking Floor Trailer Typical capacity 70m³ - 100m³

Articulated Tipper Trailer Typical capacity 40m³ - 60m³

Transportation Loose Bulk Leca® UK

The table below compares the transportation of Leca® LWA to traditional

Light weight makes Leca® LWA more economical to transport, typically needing a fraction of the number of loads required by traditional quarried materials. This has obvious advantages in reduced transport costs, site management and timescale costs plus the environmental benefit of less haulage on the road.

UK highway weight restrictions.

quarried aggregates in order to demonstrate the size of load available considering

Max trailer capacity (m3) Walking Floor Trailers Articulated Tippers 6 -8 Wheeled Rigid Tipper

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Vehicles per 1000m3

Leca® LWA

100

Traditional quarried aggregate

Over waterway Grand Union Canal, Milton Keynes

Under track Whiteside footbridge, Bathgate

Transportation Pneumatic Discharge Rounded in shape and light weight make it possible to blow Leca速 LWA into position. Using a trailer with auger discharge Leca速 LWA can be blown distances of >35 metres by hose into difficult to access areas. Benefits include no storage or double handling, reduced plant, labour and timescales.

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Bagged Leca® LWA Available in 50ltr bags, 1.2m³ and 2.2m³ bulk bags, Leca® LWA can be lifted in to position where regular loose bulk deliveries are not possible. At <20Kg, the 50ltr bag is within HSE manual handling requirements for a one man lift.

Social housing upgrade, Dudley Council

Available in 50ltr bags, 1.2m³ and 2.2m³ bulk bags

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Installation

Economical and versatile to place Leca® LWA is typically tipped into position, spread with a tracked excavator and compacted by 4 passes of the same vehicle or, it can be pneumatically blown into position, which offers specific benefits for some applications especially where site access is difficult. Leca® LWA can be installed using machinery already in use on site for the placement of other earthworks applications – unlike other lightweight products that require costly, specialist equipment and installation techniques.

1 metre depth of fill

Leca® LWA

Quarried Aggregate

Compaction Layers

Passes to compact

The pellets of Leca® LWA are round and find their position within bulk fill very quickly when pressure is exerted. For this reason the layers to achieve adequate compaction can be as deep as 1 metre, six times the depth of layer for traditional fill material and with compaction more than ten times quicker to install. Once compacted, the modulus of elasticity is 15-20MN/m2 and the maximum level of effective stress to avoid crushing of grains is 100kN/m2. Increased loading can be achieved by introducing a capping Layer such as subbase material or concrete. Surplus can easily be disposed of - for example, if an embankment is for temporary use, Leca® LWA can easily be reclaimed and re-used in a number of other locations, unlike other man made materials destined for landfill and expensive landfill charges. Full guidance is shown in the Leca® LWA Construction Control Document.

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QUALITY & ENVIRONMENTAL CONTROLS Leca® LWA is produced in Denmark by Saint-Gobain Weber Leca® A/S. Leca® LWA is produce in accordance with DS/EN ISO 9001 quality control system and DS/EN ISO14001environmental control system. RIGHTS Leca® LWA is manufactured according to identical principles in Algeria, Argentina, Austria, Belgium, China, Denmark, Egypt, Estonia, Finland, Germany, Iran, Italy, Norway, Portugal and Sweden. The Leca® trademark is registered in 65 countries throughout the world and is also registered as a European trademark. The rights to the use the trademark Leca® is owned by Leca Trading & Concession in Denmark. Leca® Trading & Concession is part of the Saint-Gobain Group of Companies.

Leca® UK Regus House, Herons Way Chester Business Park Chester CH4 9QR T: +44 (0)8443 351770 F: +44 (0)1244 893323 E: sales@leca.co.uk

Civil Engineering | Leca Geotechnical Fill ®