Techniques

Both Keller Ground Engineering and Keller Foundations provide complete end-to-end design and construct http://vhealthportal.com/product-category/anti-acidity/ services for industrial, commercial, environmental, mining and infrastructure projects.

If you are looking for a highly experienced and skilled team of engineers, designers and consultants, contact Keller today.

Ground Improvement & Grouting

Keller employs a number of techniques when solving our clients’ ground improvement, specialty engineering and piling challenges. Many of these were developed by the company itself and are now widely adopted in the international construction industry.

As well as working with engineering consultants to deliver their design solutions, we also offer a full design and construct service to our clients for varying ground improvement techniques.

We continually invest in our large fleet of plant and equipment, working closely with manufacturers to develop and hone our systems to ensure we are at the forefront of ground engineering technology.

Compaction Grouting

Compaction Grouting uses low mobility grout to rapidly improve discrete zones of weak or loose soils.  The method provides a low cost, low risk solution for underpinning, liquefaction mitigation and re-leveling of buildings back to their original elevation.  It can be used on large projects using high capacity plant as well as with hand tools, allowing improvement to be carried out in the most restricted locations.

Drill casing is installed to the base depth. The low mobility grout is then injected as the casing is slowly extracted in lifts, creating a column of overlapping grout bulbs. The expansion of the low mobility grout bulbs displaces and densifies the surrounding soils.

Compaction Grouting
Compaction Grouting

 

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Controlled Stiffness Columns

CSC
Controlled Stiffness Columns

Controlled Stiffness Columns (CSCs) can be installed through compressible soils to reduce settlement and increase bearing capacity. Loads are transferred through the high modulus concrete columns to a firm underlying layer.

This technique is generally used at the approach for bridges or culverts and under warehouse slabs, in the latter allowing the use of shallow foundations. Keller Ground Engineering offers CSCs using the displacement auger or vibrated tube methods, either as part of a design and build package or as construct only to others’ design.

Rigid Inclusions CSC / CMC
Rigid Inclusions CSC / CMC

 

 

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Deep Soil Mixing

Deep Soil Mixing is the mechanical mixing of in situ soil with a cement grout slurry using either a hollow stem paddle type mixer or the Cutter Soil Mixing (CSM) tool. This creates soil-cement (Soilcrete) columns or panels, improving the engineering properties of the ground, namely compressive strength, shear strength and permeability.

Typical applications include improvement of bearing capacity in soft or loose soils for light industrial structures or embankments and retaining walls. The method can also be used to form groundwater barriers; to environmentally immobilise or stabilise contaminants; or as part of a chemical treatment system.

Deep Wet Soil Mixing
Deep Wet Soil Mixing
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Dynamic Compaction and Dynamic Replacement

DC
Dynamic Compaction

Dynamic Compaction is a ground treatment method involving dropping a heavy weight, typically 10t to 25t, from a height of between 10m and 25m onto the ground to pre-consolidate subsurface materials.  The principle is to subject the ground to a load higher than that of any proposed structure, effectively over-consolidating the soil and minimising post-construction settlement. This method is particularly effective for treating granular soils, as well as on landfills or where subsurface voids may be present.

Clays, silts or stratified soils can be treated by Dynamic Replacement, an extension of the dynamic compaction process. Stone (or granular fill) is driven and compacted into the ground using high energy pounders to form large diameter columns.

Dynamic Compaction and Dynamic Replacement are typically used to control settlement of embankments and bridge abutments; to create foundations for large structures such as reservoirs, warehouses and one to three storey buildings; and for industrial facilities including mineral stockpiles.

Dynamic Compaction
Dynamic Compaction
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Mass Soil Mixing

Soil Mixing
Mass Soil Mixing- Tiger Brennan Drive

Mass Soil Mixing is a specialised Keller technique that is a cost-effective method of improving soft fine-grained soils and mud deposits, including dredged material. By mechanically blending a dry or wet cement binder with the soil, Mass Soil Mixing can also be used to neutralise and contain contaminated soils by the addition of a chemical powder or reactive agent.

The method improves the stability of soils. It can be used over water or on land and produces virtually no spoil. Mass Soil Mixing is used to stabilise and control settlement of soft soils beneath road and rail embankments, residential developments and warehouses and to create working platforms. Mass Soil Mixing can also be used to strengthen soils before excavation and to stabilise excavation bases.  Keller offers a variety of soil mixing products, depending on treatment depth and engineering requirements.

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Micro Piles

Micro Piles or Mini Piles are typically less than 400mm diameter, installed using flushed or augered drilling systems. They can be designed to support loads of more than 1,000kN in favourable ground conditions.

Micro Pile
Micro Pile Drill Rig

Micro-piles are often used on restricted access sites or where ground conditions, such as buried obstructions, preclude the use of conventional piles.

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Permeation Grouting

Permeation Grouting is a low pressure injection system used to improve the strength and reduce the permeability of granular soils. It is typically used for dam grouting applications and for groundwater control on tunneling projects. The method uses cement or chemical-based grouts and has the advantage that it produces no spoil.

Microfine cement grouting is an extension of permeation grouting, using finer grout capable of penetrating small voids in fissured rock and fine sands.  The GIN method (grouting intensity number) is commonly used for Dam Grout Curtains to prevent underseepage below the dam alignment.

Chemical Grouting
Chemical Grouting

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Rock Anchoring and Soil Nailing

Rock Anchors and Soil Nails offer an economical solution to temporary or permanent support and can also be used to resolve stability problems.

These structural members are designed to withstand lateral and uplift forces and are typically used with temporary and permanent excavation support systems. They are also effective for permanent retaining walls, dam stabilisation, or to resist wind-produced uplift forces.

Anchors can be installed at any angle from vertical to horizontal points, and they may be pre-tensioned or passive, depending on requirements.

Keller Ground Engineering offers a design and construct service for the supply and installation of soil nails, providing an efficient and safe way to retain embankments, cuttings and excavations.

Soil Nailing
Soil Nailing

Slurry Wall

Slurry Walls/Cut-Off Walls are non-structural and are typically installed to temporarily limit groundwater flow to enable excavation or, in permanent cases, to provide containment of buried waste or contaminated materials. They can be excavated under a self-setting cement-bentonite slurry or in a two-phase approach, with excavation under bentonite and subsequent backfilling using a soil-bentonite slurry.

Keller Ground Engineering designs and constructs:

  • Cement Bentonite Walls,
  • Soil Bentonite Walls,
  • Bio-Degradable Polymer Trenches,
  • HDPE Cut Off Barriers, and
  • Soil Mix Walls.
Slurry Wall
Slurry Wall

Soilcrete Jet Grouting

Soilcrete Jet Grouting
Soilcrete Jet Grouting

Soilcrete Jet Grouting is an erosive high pressure ground improvement system used to create cemented soils to depths of 40m or more in situ, without the need to treat up to the ground surface. Keller’s Soilcrete jet grouting system can be used for mass treatment, for example to form gravity structures or retaining systems, or for improving discrete soft or permeable soil horizons.

Jet grout columns can be installed at angles from vertical to 45°, which means the method is suitable for underpinning historic or heritage buildings. It can also be used to form blocks of improved loose or permeable soils at depth for tunnel projects. The SuperJet system can create up to 5m diameter Soilcrete columns.

The Soilcrete jet grouting is used for a range of applications:

  • Underpinning,
  • Panel walls to cut off groundwater,
  • Historic foundation restoration,
  • Improving foundation bearing capacity,
  • Joint sealing between piles and other underground structures,
  • Shaft construction and to create excavation base sealing.
Soilcrete Jet Grouting
Soilcrete Jet Grouting Process
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Soilfrac Compensation Grouting

Keller’s Soilfrac Compensation Grouting technique uses the propagation of grout-filled fractures in the soil fabric to consolidate the ground.

Sequential injections of low volumes of cement grout develop 10mm to 20mm thick grout-filled fractures in the soil fabric. Repeated injection and fracturing consolidates the soil.

The method allows buildings, structures and services to be protected from shallow tunnelling or nearby excavations, as well as lifting structures affected by settlement back to original levels. It can be carried out in real-time, for example during tunnel boring.

Fracture Grouting
Fracture Grouting
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Stone Columns

Stone Columns are a common form of ground improvement. Using similar plant and equipment to vibro-compaction, the method is used to treat clays, silts and mixed stratified soils.

Stone is introduced either down the side or from the tip of a vibro-probe and is compacted bottom-up in controlled stages. The stone columns reinforce soft soil and also accelerate drainage.

Typical applications for stone columns include settlement and stability improvement below embankments and stockpiles; foundations for low rise warehousing, sheds and other light industrial buildings; and for seismic mitigation on dam sites.

Vertical Wick Drains

Prefabricated Vertical Wick Drains, offer a cost-effective method of pre-consolidating soft, saturated and low permeability soils to allow construction of earth structures such as road or rail embankments. By incorporating a drainage layer and a superimposed surcharge load, such as earthworks fill, the consolidation of the soft soils is accelerated, through the preferential drainage paths introduced by the wick drains.

Vibro Compaction

Vibro Compaction uses probe-type vibrators hung from cranes or mounted on piling equipment to densify granular soils up to 40m deep.

The vibratory action of the probe as it drives into the ground rearranges the soil particles and densifies the soil. Granular fill is introduced into the annulus around the vibrator to maintain working platform level and to assist densification.

Vibro Compaction reduces settlement, increases bearing capacity and mitigates liquefaction potential in seismic areas.

Vibro Compaction
Vibro Compaction
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Piling & Diaphragm Walls

Keller Foundations provide design and construct services for a range of specific engineered solutions. The advanced capabilities of the in house engineering and construction teams ensure we optimse and provide cost effective, fit for purpose safe piling and deep foundation award winning solutions. Keller Foundations provide a comprehensive range of in ground foundation and ground engineering techniques.

Atlas Piles

Atlas Piles are unique screw shaped reinforced concrete piles designed to take maximum advantage of all the available soil capacity by displacing the soil rather than replacing it.

atlas-piles

The Atlas Pile is a concrete cast in situ and is not to be confused with the steel screw pile which has much lower load carrying capacity. The piles can be installed with a conventional purpose built ‘Atlas’ rig or the new generation high torque hydraulic piling piles allowing piles up to 30m to be installed in a single pass. As these piles are genuine displacement piles with the auger being thrust into the ground with a minimum of 40 tonne metre torque negligible spoil is produced for subsequent removal, very important consideration when piling in contaminated or aggressive soils.

Bored Piling

Bored Piling is a non-displacement form of foundation that is cast insitu and provides economical load bearing and walling solutions suited to a wide range of ground conditions and applications.

bored-piling

Key advantages include:

  • Able to carry very high load / shear / moment capacity
  • Low noise and vibration
  • Ground is “seen” during construction allowing validation of design assumptions
  • Can overcome adverse ground including natural or manmade obstructions
  • Can drill into hard rock
  • Can be constructed to tight tolerances

Bored Piles can be constructed using crane mounted or track mounted hydraulic drill rigs. The excavation for bored piles can be supported using casing installed by vibrators or oscillators and by drilling muds. Keller Foundations offer the following advantages for construction of Bored Piles:

  • Wide range of drill rigs available (rotary, crane-mount, excavator mount, low headroom)
  • Reliability of personnel, plant and equipment to provide a quality product
  • A proven track record of experience and knowledge across all areas of Australia gained during more than 25 years of constructing bored piles
  • Economical and productive methods of drilling in all ground conditions, from soft soils to very high strength rock
  • Extensive range of drill tools, casings and other auxiliary equipment suited to different drilling conditions that may be encountered
  • Localised plant and equipment support in capital cities around Australia

Bored Piling with Drilling Fluids

Bored Piling with Drilling Fluids are required when drilling through weak soils (such as fill materials, sands and soft clays) as drill holes require temporary support that can be provided by use of a drill fluid.

bored-piling-with-drilling-fluids

We have the experience and equipment to mix and place bentonite or synthetic slurry for the temporary support of the drill hole. Our specialist mud technicians continuously monitor the quality of the support fluid to ensure high quality finished pile concrete results.

Through our extensive experience in both bored piles and diaphragm walls we have built up a large fleet of equipment for mixing, storing, cleaning and placement of slurry and have the ability to operate several high volume batch plants on one or more projects simultaneously.

Bulk Sampling

Keller Foundations’ drilling equipment is suited to Bulk Sampling of soil for mineral exploration.  A hydraulic rotary drill is used to probe the soils to obtain bulk samples for laboratory analysis when searching for mineral deposits. Where appropriate temporary casings or water can be used to stabilise the bore during sampling.

bulk-sampling

Using a telescopic kelly bar and auger for soil excavation it is possible to drill up to 70m depth to obtain these samples.  A drilling bucket is typically used at the sampling depth to recover a relatively undisturbed sample of soil. The bucket is emptied over a hopper that contains a sample bag to secure then soil sample for laboratory analysis.

Continuous Flight Auger

Continuous Flight Auger (CFA) Piling is the quietest form of piling and is a fast and economical technique. It is a cast in-situ process, very suited to soft ground where deep casings or use of drilling support fluids might otherwise be needed. CFA piling is a non-displacement piling system; hence the soil excavated from the pile is brought to the surface. CFA piles can be an attractive alternative to conventional bored piles where applicable with an improved rate of installation and a reduction in noise and vibration.

CFA piles can be used for load transfer beneath structural elements and also for contiguous and secant (interlocking) piled retaining walls.

cfa-continuous-flight-auger

The construction sequence can be seen in the animation accessed from the image at the foot of this page, and consists of:

  1. Drilling a full length auger with a hollow stem (temporarily plugged) into the soil using a constant penetration rate.
  2. After reaching the design toe level, concrete is pumped through the hollow stem of the auger while the auger is extracted. It is important that the auger always remains embedded into the concrete.
  3. Positive concrete pressure is maintained throughout the placement of concrete. CFA piles have to be poured to platform level to facilitate reinforcement installation and avoid pile necking.
  4. After completion of the concrete placement process the reinforcement cage is plunged into the fluid concrete.

Keller Foundations offers a CFA range with the following advantages:

  • Diameters from 450 to 1200mm
  • Depths up to 32m
  • Able to carry high load/ shear/ moment capacity
  • Low noise and vibration
  • Speed of installation
  • Can overcome interbedded clays and sands
  • Can deal with water bearing sands and gravels and penetrate weak rocks

It is important to select an experienced company for your CFA piling application as the effect of the construction technique on different ground conditions has to be fully understood.  Concrete mix requirements have to be carefully designed to maintain workability yet avoid segregation and bleeding during placement. Under powered piling rigs can lead to uncontrolled soil transport, causing settlement to adjacent structures.

CFA piles are suitable a foundation piles, for secant pile walls, contiguous pile walls and soldier pile walls. Keller Foundations undertakes both design and construct or construct only projects using CFA piles.

Please click to see a time lapse of CFA piling.

Diaphragm Walls

Diaphragm Walls are constructed using a narrow trench excavated in ground and supported by an engineered fluid (typically a bentonite mud) until the mud is replaced by the permanent material. Generally diaphragm walls are made from reinforced concrete, though unreinforced walls can also be used. Walls generally range in thickness from 500-1500mm and can be excavated to depths of 50m or more.

diaphragm-walls

Diaphragm Walls are often used in congested areas or where the excavation depth is very deep which would otherwise require excavation of much greater soil volumes to provide stable battered slopes. They are well suited for deep basements, underground rail stations, rail car unloaders, tunnel approaches, pumping stations and such like.

Diaphragm Walls can be installed close to existing structures and in restricted headroom. They are often used in “top down” construction methods.

The excavation is typically undertaken using cable or hydraulic operated grabs except where penetration into hard rock is required when a hydraulically operated rotating cutter or hydromill is used.

Keller Foundations is the most experienced Australian Contractor offering this technique, having constructed diaphragm walls for several desalination projects, road tunnels and urban basements over the last 8 years.  We have a large range of specialist equipment for diaphragm wall construction.

Driven Sheet Piles

Driven Sheet Piles are thin interlocking steel sheets used to construct a continuous barrier in the ground. Interlock is typically achieved by clutching the edge of one pile into the previous pile.

driven-sheet-piles

A wide range of sheet pile sections and profiles are available from many steel manufacturers. Cold-rolled sections have a weaker interlock than hot-rolled sections. In hard driving conditions this interlock might “unzip” or cause alignment problems which would require replacement of the sheet piles. Cold-rolled sections also are usually thinner than hot rolled and thus may be more prone to overstressing during driving.

Sheet piled retaining walls are often restrained by use of internal propping, bracing, anchors or deadmen. It is often possible to extract and reuse sheet piles making this an economically attractive retaining wall system.

One of the main applications for sheet piles is for temporary retaining walls or cofferdams used to allow permanent in ground construction to be undertaken. The durability of sheet piles can be extended with protective coatings.

Driven Sheet Piles are often installed by vibrating hammers operated off leaders mounted on tracked base machines or suspended from crawler cranes. Diesel impact hammers and hydraulic press in machines can also be used to drive or push the piles into place. Sometimes water jetting or preboring is used to assist penetration through stiff or hard layers.

Keller Foundations installs Driven Sheet Piles up to 25m in length with individual pile weight up to 5 tonnes. We carry out this work using a range of piling rigs, including purpose built RG16, RG19 and LRB255 piling rigs.

The RG16 and RG19 piling rigs have telescopic leaders and allow the piling rig to pitch and vibrate piles up to 16m and 19m long to refusal. These rigs have been used extensively throughout Australia including at Finnucane Island Car Dumper No 4 (WA), Perth desalination plant (WA), Adelaide Superway (SA), Tugun Bypass (NSW) and at Fremantle Port Upgrade (WA).

Free driving of sheet piles is also common, we use ICE 44-50 vibrators for smaller pile sections and PTC 120D vibrators for larger piles.

Driven Steel Piles

Driven Steel Piles utilise a range of steel sections that are used for piles. The most common are tubes, universal columns (or H piles) and rectangular hollow sections. Driving piles, as opposed to drilling bores, can be advantageous because the soil displaced by driving the piles compresses the surrounding soil, resulting in greater friction against the sides of the piles, thus increasing their load-bearing capacity. In addition, as driving a pile displaces the soil rather than removes it, there is no cost of spoil disposal incurred. This can be particularly beneficial if the soil is contaminated.

driven-steel-piling

A wide range of sizes of steel tube (or pipe) is commonly available and Keller Foundations have experience in driving tubes from 350-1500mm diameter with wall thicknesses from 7-25mm.

Tubular piles can be driven with either an open bottom end or closed end. When driven open end, soil is allowed to enter the bottom of the tube. If an empty pipe is required, an auger can be used to remove the soil inside following driving. If the soil is suitable internal cleaning could also be carried out by water jetting.

Closed end pipe piles have the bottom of the pile sealed with a steel plate or cast steel shoe. When driving through hard strata pile toes may be reinforced with a secondary driving shoe to assist penetration and minimise pile damage.

The structural capacity of tubular piles is primarily calculated based on steel strength and concrete strength (if filled). Corrosion can be dealt with by application of protective coatings, by allowing a sacrificial thickness of steel or by adopting a higher grade of steel than otherwise needed.

Steel tube piles can either be new steel manufactured specifically for the piling industry or reclaimed steel tubular casing previously used for other purposes such as oil and gas exploration. Most steel tube piles can readily be spliced to provide greater depth capability than a driving rig can accommodate.

H-Piles and Universal Columns (UC’s) are structural beams that are driven in the ground for deep foundation application. They can be easily cut off or joined by cutting and welding. If a steel pile is driven into a low pH soils or where water flows readily then there is a risk of corrosion, coal-tar epoxy or cathodic protection can be applied to slow or eliminate the corrosion process.

Sometimes a combination of steel tubes and steel piles are used to make a “combi wall” this benefits from the strength properties of tubular piles but at reduced materials cost.

Keller Foundations installs driven steel piles up to 1500mm diameter, up to 50m in single lengths and at rakes of up to 1 in 3.

The processes consist of pitching and driving in a fixed land based leader or free driving piles with rope suspended hammers. Use of fixed leaders allows greater control of position and verticality.

When working over water the same installation processes are used or piles can be driven through our rotating marine leader which can traverse in all directions on and grid arrangement and rotate 360 degrees to pick up any pile on rakes up to 1 in 3 within a defined grid arrangement.

driven-steel-piling-2

Enlarged Base Piles

Enlarged Base Piles are generally installed by bottom driving, highly special techniques such as open-ended coring, rock socketing, and composite shaft construction. These piling techniques are used in particular situations to overcome unique site problems. It can safely withstand very high compressive and tensile forces and substantial horizontal loads.

enlarged-base-2

The installation process of each Keller Foundations pile takes account of the soil conditions at each pile location. Quality control checks on the driving and basing resistance of every pile result in optimum pile performance.

The pile is always sealed during construction. Ground water or collapsing ground present no problems. Noise and vibration levels are minimised as a result of Keller Foundations’ unique bottom driving technique.

Because the impact occurs at the bottom of the tube, the Keller Foundations pile is the quietest of the driven cast-in-place systems and is suitable where high noise levels would cause environmental problems. Vibration levels are monitored regularly and in most ground conditions can be kept below the strictest international standards.

These features have helped make the Keller Foundations pile the most popular castin-place pile in Australia for more than 50 years.

Hard Rock Drilling

Over many years of experience and through extensive Research and Development, Keller Foundations have accumulated a range of high strength drilling equipment for Hard Rock Drilling. These including rock augers, rock roller bits, core barrels and cluster hammers to give a productive solution to drilling in rock from 5 MPa to over 300 MPa as shown in the diagram.

hard-rock-drilling

With the support of a large fleet of rotary drill rigs we can take on small or large projects for any diameter of drilling in high strength rock.

Cluster drills have been used to drill rock sockets up to 8m long in very high strength basalt including at a project for the upgrade of the Pacific Highway at Banora Point on the New South Wales / Queensland border.

Low Headroom Piling

Low Headroom Piling is for projects that require foundation construction in areas where headroom is restricted by existing structures, overhead utilities of other constraints.

low-headroom-working

Keller Foundations has specially modified drilling and piling equipment that is able to drive and drill in either CFA (6.9m headroom) or rotary mode (6.2m headroom).  Piling rigs can construct piles from 500mm to 1200mm diameter, to depths up to 20m.  Applications include underpinning works, renovations to existing structures such as shops, railway stations, bridge work extensions in awkward locations.

low-headroom-working-2

Marine and Falsework

Keller Foundations can undertake Marine and Falsework on bridge infrastructure projects where difficult ground conditions are present in bridge structures. We can provide temporary false work structures for both the installation of piled foundations and for subsequent use by the main contractor for ongoing superstructure works up to and including placing of bridge deck units.

marine-and-false-work

Keller Foundations have developed a range of false work systems to more effectively meet client’s specific project requirements. Our range of false work has been designed to accommodate typical loadings, including drill rigs, crawler cranes, mobile cranes, excavators, dump trucks, concrete boom pumps, Super T beam delivery vehicles etc.

Significant projects undertaken requiring false work, where both substructure and superstructure works have been carried out from our false work include:

  • North South Bypass Tunnel
  • Hale Street Bridge
  • Townsville Port Access Road
  • St. Lawrence Rail Bridge
  • Karara

Our range of false work available is as follows:

  • 100t Capacity: 25 x 13.5m Spans – 335 Lineal Metres
  • 150t Capacity: 15 x 12m Spans – 180 Lineal Metres
  • 300t Capacity: 16 x 8.8m spans – 140 Lineal Metres

In addition to piling from false work, we are experienced at working from barges in river or near shore. We have installed bored piles, prestressed concrete piles, driven steel tubes and driven steel sheets from barges and from false work.

Precast Concrete Piles

Precast Concrete Piles are a high strength high capacity precast concrete pile which incorporates mechanical and compression joints, allowing piles to be spliced quickly and then driven to any required depth. Precast piles offer the geotechnical efficiency of a driven pile with the economies of a mass produced product. A rigorous quality assurance program throughout the casting, driving and testing process ensures a consistently reliable product with high strength and durability. Precast piles are most suited to ground conditions where soft upper strata overlie a hard bearing layer and in areas with clay or silt deposits.

precast-concrete-piles-2

Keller Foundations maintains its own casting facilities which enables it to cater for varying site conditions with a range of stock pile lengths and sizes. Keller Foundations maintains in house casting capacity sufficient to customise pile lengths for individual sites and to cater for site variability without the need for long casting periods prior to job commencement.

Pretressed Concrete Piles

Pretressed Concrete Piles are displacement piles where no (or minimal) spoil arises at the surface from their installation. Prestressed Concrete Piles offer several benefits compared to other driven pile systems. Tensile stresses, which can arise in a pile during driving, can be better resisted due to the prestressing forces, and the pile is less likely to be damaged during handling. Bending stresses during driving are also less likely to produce cracking than in conventional precast concrete piles.

prestressed-concrete-piles

Prestressed Concrete Piles are made from high-strength concrete, typically 50 MPa or more. As they are factory cast curing conditions can be strictly regulated. Special manufacturing processes such steam curing can be adopted to produce higher strength concrete.

This type of pile is generally less permeable than cast in situ reinforced concrete piles and hence offers superior performance in a marine environment.

Pointed Concrete or steel driving “shoes” can be used at the toe of jointed piles for protection when penetrating soils containing boulders, or in weak rock. When used in aggressive environments, piles can have improved durability by coating with epoxy bitumen. Slip layers can also be applied to remove the potential effects of negative skin friction.

Lateral forces can be resisted by installing piles on a rake.

Prestressed Concrete Piles are installed using driven track mounted rigs with modern efficient hydraulic hammers. Piles are typically supplied in lengths varying from 8-24m. Longer piles are installed using a jointing system.  Piling Contractors has developed a new form of joint for this pile.

Pile load capacity can be determined during driving using rig instrumentation, dynamic analysis and established methods of measuring the pile “set” per fixed number of hammer blows.

Keller Foundations has many years experience in installation of 550mm octagonal prestressed concrete piles on land and over water and our equipment allows us to pitch longer pile lengths than many others. Key advantages of the process are:

  • Practically unlimited depth
  • Not affected by Groundwater
  • Factory Manufacture
  • Self proving
  • Immediate follow on construction
  • Clean site / no spoil

In special circumstances a composite pile can be used made up of a lower section of steel column or H pile joined to an upper prestressed or precast concrete pile. This is particularly useful when the overall weight of the pile needs to be reduced (due to transport or handling constraints. For marine structures a composite concrete / steel pile provides a concrete section in the area where fluctuating sea water levels cause corrosion but also a cheaper steel section below this zone. The pile can be driven deep to provide uplift resistance. Composite piles are also suitable where hard layers of strata need to be driven into or through.

Retaining Walls

Embedded Retaining Walls are used in a wide variety of civil engineering applications including embankment stabilisation, construction of basement walls, underpasses or tunnel approaches, in ground tanks and other buried structures. The most appropriate system depends upon a number of factors including soil and groundwater conditions, retained height, acceptable deflections and propping options, desired wall geometry and design life. The cost of retaining wall construction varies considerably depending on the process and the conditions in which it is used.

retaining-walls

Use of in ground retaining walls can minimise the bulk excavation needed to achieve desired ground profiles. Walls can be used in temporary or permanent conditions.

Keller Foundations offers many types of retaining wall including:

  • Soldier Pile Walls (cast in situ concrete bored, CFA or driven steel) – piles are installed at wide spacing’s (can be up to 5 – 8 pile diameters depending on soil conditions). The soil between piles is retained typically by timber lagging or by shotcrete applied to the exposed earth face during excavation. This wall type is not suitable where high water pressures or flows exist in the soil to be retained. This is usually the simplest, fastest and cheapest type of embedded retaining wall often used for temporary works.
  • Contiguous Pile Walls (cast in situ bored or CFA) – this wall method is often used in permanent applications. Structural piles are installed at close spacing’s typically with a 100mm gap between piles. The soil is therefore exposed during excavation but will often self support temporarily due to “arching”. This method is suitable in a variety of soils where groundwater lies below the maximum excavation depth.
  • Secant Pile Walls (hard / soft, hard / firm or hard / hard, cast in situ bored or CFA). A guide wall is required for this method of construction to ensure that piles are accurately located to achieve an interlock (or secant) cut into the adjacent pile. A secant pile wall uses interlocking male and female cast in situ piles to produce a retaining structure. Construction is carried out sequentially with primary (female) piles installed first then secondary (male) piles cut into the primary piles forming a continuous wall.

A hard / soft wall uses a weak concrete or grout for the female pile, which is usually unreinforced. This wall type provides some degree of water retention but is not watertight. Hard / Firm and Hard / Hard secant walls use the same construction process  however the primary pile is cast from either weak mix concrete (typically 5 – 15 MPa, Hard / Firm wall ) or full strength concrete (hard / hard wall). The primary pile may also be reinforced. The construction sequence becomes particularly critical when needing to cut segments of 40 MPa concrete piles to allow installation of the secondary pile. High torque drill rigs and specially designed cutting tools are required.

Please click to see a time lapse of secant pile wall construction.

Secant pile walls can be used without additional construction in front of the excavated face. At exposed heights greater than 9 – 12m it often becomes uneconomic to achieve continuous pile overlap and hence a diaphragm wall generally is more suitable.

Keller Foundations has many years of experience in retaining wall construction and our in house design teams are skilled at producing economic designs for such structures, backed by an extensive library of monitoring from previous projects.

Rigid Inclusions

Rigid Inclusions are used as Displacement Columns for structural load transfer or as Controlled Stiffness Columns (CSC’s) for ground improvement. They are a quiet, vibration free and economical foundation or ground improvement element that produces virtually no spoil arising. The process is ideally suited to soft soils overlying stiff bearing strata and for contaminated sites where handling excavated spoil is environmentally unacceptable.

rigid-inclusions

CSC’s are sometimes known as Concrete Injected Columns (CIC) or Controlled Modulus Columns (CMC). CSC’s are often used as an economical alternative to Screw piles, or Timber Piles. When combined with appropriate ground slab design, very economical solutions can be provided for warehouses and other moderately loaded building structures. CSC’s are also used in ground improvement on road and rail infrastructure projects (typically between piled bridge abutments and untreated road pavements).

When fully reinforced they can transfer structural loads. When appropriately designed they can improve the bearing capacity of a wider soil block and are typically used in this manner beneath road or railway embankments.

CSCs are not intended to directly support the loads imposed by a structure, but to improve the global response of the soil in order to control settlement. The dimensions, spacing, and composition of the CSCs are based upon the development of an optimal combination of support from the columns and the surrounding soil to limit settlements for the project within the allowable range, and to obtain the required value for the equivalent composite deformation modulus of the improved soil.

Two different techniques can be used to construct Rigid Inclusions’, either a Full Displacement Auger or a Vibrated Steel Tube. The full displacement auger construction principal is similar to CFA piles however a specially designed displacement auger is used in conjunction with a high torque drill rig to displace the soil and facilitate placement of concrete through the drill head stem to construct columns in the ground.

A typical displacement auger is shown in the photo adjacent.

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During the drilling process the ground is loosened by the auger teeth and transported through the auger flights until it reaches the widest point of the displacement body. Here, the soil is pushed in the adjacent ground, compacting the surrounding soil and, usually, improving the skin friction of the pile.

Concrete placement and reinforcement cage installation are carried out in the same manner as for CFA piles. Typical diameters for this pile type are 360mm, 450mm and 520mm. Pile lengths can be up to 30m.

Piling Contractors offers design and construct or construct only solutions and will carry out in-house on site verification through appropriate load tests.

Secant Piles

Secant Piles are hard / soft, hard / firm or hard / hard walls, cast in situ bored or CFA. A guide wall is required for this method of construction to ensure that piles are accurately located to achieve an interlock (or secant) cut into the adjacent pile. A secant pile wall uses interlocking male and female cast in situ piles to produce a retaining structure. Construction is carried out sequentially with primary (female) piles installed first then secondary (male) piles cut into the primary piles forming a continuous wall.

A hard / soft wall uses a weak concrete or grout for the female pile, which is usually not reinforced. This wall type provides some degree of water retention but is not watertight. Hard / Firm and Hard / Hard secant walls use the same construction process  however the primary pile is cast from either weak mix concrete (typically 5 – 15 MPa, Hard / Firm wall ) or full strength concrete (hard / hard wall). The primary pile may also be reinforced. The construction sequence becomes particularly critical when needing to cut segments of 40 MPa concrete piles to allow installation of the secondary pile. High torque drill rigs and specially designed cutting tools are required.

Secant pile walls can be used without additional construction in front of the excavated face. At exposed heights greater than 9–12m it often becomes uneconomic to achieve continuous pile overlap and hence a diaphragm wall generally is more suitable.

Keller Foundations have many years of experience in retaining wall construction and our in house design teams are skilled at producing economic designs for such structures, backed by an extensive library of monitoring from previous projects.

Please click to see a time lapse of secant pile wall construction.

Shafts

Keller Foundations has many years experience in constructing large diameter shafts for ventilation, access or pumping purposes. Our equipment allows up to 6m diameter shaft construction (reamed out from smaller diameter starter holes in suitable soils, and we have developed means of lining the shaft with shotcrete / insitu concrete where the use of temporary casing is unsuitable.

shafts

Temporary and Permanent Casing

Temporary and Permanent Casing is required when excavating through soft, weak or unstable ground as a means of temporary stabilisation of the soils. Keller Foundations has wide experience in the use of temporary and permanent steel casings for bore hole support. Such casings can be installed using casing drivers, vibrators, oscillators or driving hammers and dollies. Where substantial lengths of casing are needed, or where the depth requiring casing varies significantly in any one area, the use of double walled temporary segmental casings provides an economic solution.

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We hold substantial stock of segmental casing in various sizes along with cutting heads, casing drivers and extractors to suit. Our fleet of high torque rotary drill rigs gives us the ability to install segmental casing to depths up to 40m (dependent on ground conditions) to overcome any soft ground conditions encountered.