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Ground Anchors is the generic term applied to systems which mechanically fix structures to the ground to resist load. They are an essential part of modern foundation, abutment and excavation designs, as they can deliver hold-down forces of over 2000 tonnes each within a very compact package.
The design and installation of ground anchoring systems requires a high level of diligence if premature failure is to be avoided. Equally vital is testing and monitoring of any anchor system both before and after it enters service. We have the resources to design and test installed ground anchors of any size for compliance with Australian standards, even in the most difficult locations.
We provide design and installation services for ground anchors for all situations, including:
- Dam walls
- Retaining structures
- Cable-stay anchor-blocks
- Bridge abutments
- Slope stability
- Wind or seismic resistance
- Hydrostatic uplift
Geopractika offers a range of CFA piling techniques such as
- Contiguous Piling
- Secant Piling
- Foundation/plunge piling
- Cased CFA piling
Grouting is a technique that transforms granular soils into sandstone-like masses. The soils best suited for this technique are sands with low fines content. Grout is injected under pressure through predrilled holes. The grout permeates the soil and solidifies it into a sandstone-like mass. The grouted soil has increased strength and reduced permeability. Grouting has been used to underpin existing foundations, create excavation support walls and stabilise soils for tunnels.
For underpinning applications, chemical grouting offers the advantages of being easily performed where access and space is limited, and of not requiring a structural connection to the foundation being underpinned. A common application of chemical grouting is to provide both excavation support and underpinning when an excavation is planned immediately adjacent to an existing structure. Usually, chemical grouting can be accomplished without disrupting normal facility operations.
Chemical grouting equipment is well-suited for tunneling applications in urban environments, whether for stabilizing soil around break-ins or break-outs, or for mitigating settlement of overlying structures within the influence of the tunnel alignment
Geopractika offers a range of piling solutions such as
- Screw Piles
- Soldier Piles
Soil nailing is an earth retention technique that uses grouted tension-resisting steel elements (nails) that can be designed for permanent or temporary support. The walls are generally constructed from the top down. Soil nailing treats unstable natural soil slopes. This technique involves the insertion of slender reinforcing elements into the slope, rebar (reinforcing bars) are installed into a pre-drilled hole and then grouted into place. Some form of secondary support usually in the form of a lightly reinforced shotcrete skin, is required. Bearing plates are incorporated into the shotcrete and fixed to the heads of the soil nails. The soil at the base of this first stage is then removed and the installation process is repeated until the desired wall depth is reached.
Finished soil nails produce a zone of reinforced ground. Soil nailing has been used to stabilise slopes and landslides, provide earth retention for excavations for buildings, basement constructions, tunnels, deep cuts, and to repair existing retaining walls.
Permanent and Temporary
Anchors can be used for both temporary or permanent applications. Permanent anchors are expected to function for long periods of time and thus corrosion protection is applied. Temporary anchors inserted below ground and used to stabilise earth, sand or rock adjacent to excavation work. These anchors are installed for short periods of time and maybe safely de-stressed or removed upon completion of the works.
Rock bolts are a long anchor bolt. Rock bolting is a very effective technique for stabilising excavations and retaining structures, tension and rotations.
In this technique initially a hole with a predetermined length is drilled into the ground or surface and a high tensile steel tendon is placed in it. The bond length is grouted and will provide the system’s necessary resistance. The anchor can be post tensioned as required.
Anchor transfers load from the unstable exterior, to the confined (and much stronger) interior of the rock mass.
Cased CFA Piling
Cased CFA combines the benefits of a rotary and a CFA solution proving particularly benefical and effective when installing larger contiguous and secant piled retaining walls. The single flight auger allows a much faster continuous drilling whilst the casing helps to keep the pile vertical, within tolerance and watertight. The rotary drive units for the casing and the augers are connected but rotate in opposite directions, simultaneously drilling them into the ground.
Contiguous piling is a technique used in construction to create a deep concrete foundation or when the piles are side by side and not linked together they form a retaining wall for excavations. The drilling process is suitable for penetrating dense layers and is unaffected by ground water or collapsing soil conditions. The contiguous method for piled walls is mostly suited on sites where the geotechnical conditions are generally soft as found in a silty or sandy soil section. Within built up areas there may be need for deep excavation works to be undertaken along a site boundary or adjacent to existing buildings, structures and older buildings where there are low tolerances to vibration sensitivity.
The pile is formed by first drilling into the ground with a continuous flight auger. Upon completion of drilling, concrete or cement grout is injected under pressure through the hollow stem of the auger. On completion of this operation, a steel reinforcing cage is inserted into the fluid column of concrete or grout.
To ensure pile quality and integrity, all of our rigs are fitted with the latest instrumentation which monitor penetration rate, torque, extraction rate, concrete pressure and oversupply in real time.
Foundation/plunge piles transfers building loads to bearing soils or bedrock. A plunge pile is a structural steel section embedded in a freshly poured concrete pile, eliminating the need for baseplates and holding down bolts. Plunge piles areare primarly used in top down construction method. Benefits of using top-down construction techniques is there is dramatic savings in construction time, decreased carbon foot print.
Secant pile walls are formed by constructing intersecting reinforced concrete piles. Primary (soft) piles are installed first with the secondary (Hard) piles constructed in between primary piles to the full design depth, cutting into the secondary piles and reinforced in the usual manner. This form of construction ensures that water entry into the excavation is greatly reduced
Within built up areas there may be a need for deep excavation works these maybe undertaken along a site boundary or adjacent to existing buildings, structures and older buildings where there are low tolerances to vibration sensitivity and relatively high ground water levels.
A secant pile wall when completed is a cost effective solution alternative to a diaphragm wall construction.
Compaction grouting, also known as low mobility grouting. It is a grouting technique that displaces and densifies loose granular soils, reinforces fine grained soils and stabilises subsurface voids or sinkholes, by the staged injection of low-slump, low mobility aggregate grout. Typically, an injection pipe is first advanced to the maximum treatment depth. The low mobility grout is then injected as the pipe is slowly extracted in lifts, creating a column of overlapping grout bulbs. The expansion of the low mobility grout bulbs displaces surrounding soils. When performed in granular soil, compaction grouting increases the surrounding soils density, friction angle and stiffness. In all soils, the high modulus grout column reinforces the soils within the treatment zone. By sequencing the compaction grouting work from primary to secondary to tertiary locations, the densification process can be performed to achieve significant improvement. Compaction grouting has been used to increase bearing capacity, and decrease settlement and liquefaction potential for planned and existing structures. In karst geologies, compaction grouting has been used to treat existing sinkholes or to reduce the sinkhole potential in sinkhole prone areas.
Compaction grouting offers an economic advantage over conventional approaches such as removal and replacement, or piling, and can be accomplished where access is difficult and space is limited. Compaction grouting for treatment beneath existing structures is often selected because the low mobility grout columns do not require structural connection to the foundations.
Jet Grouting is method of ground improvement that departs from the classical forms of grouting in that it does not penetrate the soil, rather it uses high energy in the form of a high velocity jet of grout to destroy the soil structure and simultaneously mix cement grout into the in-situ soil.
Jet Grouting is a very effective grouting technique for minimizing ground settlements and stabilising excavations. In this technique, after drilling to the required depth, the drill rods are rotated and raised to the ground surface while cement grout is injected at a high pressure. The high pressure grout erodes the soil matrix and thus forms a grout column. Depending on the application and soils to be treated, one of three variations is used: the single fluid system (slurry grout jet), the double fluid system (slurry grout jet surrounded by an air jet) and the triple fluid system (water jet surrounded by an air jet, with a lower grout jet). Jet grouting constructs columns with designed strength and permeability.
Jet grouting has been used to underpin existing foundations, construct excavation support walls, and construct slabs to seal the bottom of planned excavations. The essential qualities of Jet Grouting are to increase strength and decrease permeability in soils.
Microfine Cement Injection
Microfine injection (Permeation) grouting is a ground treatment method in which grout is injected into a porous medium without disturbing its original structure. Permeation grouting is the process of filling the voids in a soil or rock deposit to change its geotechnical properties. Specially designed grout mixture is used without displacing the soil particles or widening the fissures of the rock. This technique uses low pressure as to not cause destabilisation and segregation. There are distinct limits on the grout mix used for specific types of soil or rock. Applications are for enhanced foundation bearing value, improvement of excavation character in sands and reduction of liquefaction potential.
Filling a void behind a liner or pipe with grout under pressure sufficient to ensure void is properly filled but without overstressing temporary or permanent ground support, or causing ground heave to occur.
Micropiles also known as mini piles are a system of soil inclusions using steel bar reinforcement and cement grout combinations with or without steel casing that are mainly used as friction piles to take tensile or compressive loads.
A micropile is a drilled and grouted replacement pile that is typically reinforced. It is constructed by drilling a borehole, placing reinforcement, and grouting the hole. Micropiles are high performance, high capacity, and small diameter (50mm to 300mm). Micropiles are drilled and grouted in place they are designed with a centrally placed steel reinforcing member consisting of single (or multiple bars), used to take compression and tension loading, crafted to withstand relatively significant axial and moderate lateral loads. Micro piles are commonly used in older buildings and historical sites.
Screw piles are constructed using varying sizes of tubular hollow sections with helical steel plates welded to the pile shaft in accordance with the intended ground conditions. Screw piles are installed by screwing them into the ground using the rotary hydraulics attached to an excavator. Special drive attachments connect the screw pile to the machine. Screw piles are suitable for both tensile and compression loads. Main benefits of using screw piles is shorter project times, ease of installation, ease of access, reduction of the carbon footprint and cost effective.
Soldier Piles are constructed of wide flange steel H sections spaced up to 3m apart and are installed/driven prior to excavation. As the excavation proceeds, precast concrete panels/ timber sheeting are inserted behind the H pile flanges. Soldier piles are suitable in conditions where well constructed walls will not result in subsidence such as over-consolidated clays, soils above the water table if they have some cohesion.
Soil nailing is an earth retention technique that uses grouted tension-resisting steel elements (nails) that can be designed for permanent or temporary support. The walls are generally constructed from the top down. Soil nailing treats unstable natural soil slopes. This technique involves the insertion of slender reinforcing elements into the slope, rebar (reinforcing bars) are installed into a pre-drilled hole and then grouted into place. Some form of secondary support usually in the form of a lightly reinforced shotcrete skin, is required. Bearing plates are incorporated into the shotcrete and fixed to the heads of the soil nails. The soil at the base of this first stage is then removed and the installation process is repeated until the desired wall depth is reached.Finished soil nails produce a zone of reinforced ground. Soil nailing has been used to stabilise slopes and landslides, provide earth retention for excavations for buildings, basement constructions, tunnels, deep cuts, and to repair existing retaining walls.