Retaining walls hold back soil, generally in sloping conditions and must support the lateral load or pressure of the earth fill behind it and any applied loads, for example, vehicles or civil structures. Retaining walls incorporate a drainage medium to prevent water build up behind or beneath the wall. Groundwater can increase pressure and reduce the wall’s load bearing capacity and its ability to resist sliding.
Ground Structures offers extensive knowledge and experience for a broad range of residential, commercial and infrastructure retaining wall solutions including palisade timber or concrete retaining walls, soldier pile, timber pole and rail, steel UC pile and timber waler, reinforced concrete pile walls with shotcrete arch/panel, gravity walls, masonry block, precast panel and temporary retaining walls. Irrespective of the retaining wall solution required, we offer a single source solution which may include piling, tie backs and anchoring to piles, foundations, slip repairs and stabilisation, site works and civil structures.
We offer the capability to work in difficult access areas, in a range of geotechnical environments and challenging site conditions. All materials to complete necessary works are provided as required.
Palisade Timber or Concrete Pile Retaining Walls
Palisade timber or concrete retaining walls are used in the construction of highly effective permanent retaining wall solutions. Typically for heavy duty applications supporting substantial loads, palisade retaining walls are also known as inground or barrier pile retaining walls. They are often constructed with a concrete capping beam and are an effective measure to preserve or remediate cliff erosion and arrest the effects of ground subsidence.
Soldier Pile Retaining Walls
Soldier piles, or barrier pile retaining walls utilise either encased timber or reinforced concrete piles, are closely spaced and penetrate into more competent subsoils, thereby retaining the more unstable upper layers. Often a capping beam is used to link the piles, or used in conjunction with house piles to ensure stable ground support.
Timber Pole and Rail Retaining Walls
Compared to steel, timber pole and rail retaining walls generally provide a cost effective option and result in a natural look using renewable materials.
Construction usually involves battering back the area, drilling to depth and concreting in the timber poles. Timber rail is installed after the concrete is set, then drainage medium is placed behind the wall to decrease the groundwater pressure and provide effective drainage. This type of construction can be completed quickly and is particularly useful in temporary works or slip repair and stabilisation situations.
Steel UC Pile and Timber Waler Retaining Walls
These retaining walls are constructed using steel UC or UB columns, which are typically galvanized or epoxy coated, and in-filled with round timber waler poles.
They are useful for high retaining walls and can be constructed on boundary lines with minimal intrusion onto adjacent sites. They can also be constructed using a top-down construction method while the site is being excavated, ensuring safe site works.
Reinforced Concrete Pile Retaining Walls with Shotcrete Arch/Panel
These walls are typical on boundaries of construction sites where a top-down construction method is necessary. Concrete piles are formed prior to excavation, then as the excavation proceeds starter bars are drilled and epoxied into the piles, reinforcing mesh is tied to the starter bars between piles, and shotcrete is sprayed on to the excavated face to form a concrete panel. The excavation can be done in stages and the shotcrete can be applied as the excavation proceeds downwards. The advantage of this type of retaining wall is that neighbouring structures are protected from the effects of unstable excavations and the structure is permanent and can be incorporated as part of the new building.
Gravity Retaining Walls
Gravity walls rely on their mass to withstand the pressure of the soil behind. Generally, drainage is essential – water build up behind the retaining wall is one of the leading causes of retaining wall failure. The drainage system should consist of granular free draining gravel placed immediately behind the wall, and a perforated drainage pipe to collect and remove water.
Masonry Block Retaining Walls
Compared to reinforced concrete, reinforced concrete masonry walls eliminate shuttering and provide a uniform concrete surface texture.
There are two types of masonry block retaining walls – those where excavation is below the level of an adjacent site and need to be constructed as close as possible to the boundary. Alternatively, there are those which are constructed to fill against a neighbouring boundary. Specific site conditions will determine the type of masonry block retaining wall required.
Precast Panel Retaining Walls
Precast concrete manufacturers produce a wide range of engineered earth retaining systems designed to provide an efficient and cost-effective solution. Issues such as wall height, right-of-way, seismic activity, drainage and quality control may be overcome with a precast concrete earth retaining system. These walls are generally structurally efficient; however, foundation detailing can be complicated and attention to waterproofing is required at the base.
Tie Backs and Anchoring to Piles and Retaining Walls
A tieback is a horizontal wire or rod, used to reinforce retaining walls for stability. With one end of the tieback secured to the wall, the other end is anchored to a stable structure, such as a concrete deadman pile which has been installed into the ground or anchored into earth with sufficient resistance. This application reduces the loading on the main structure by transferring the load to the deadman pile which can be located on more competent ground, thereby resisting forces that would otherwise cause the wall to lean. Deadman piles are retrofitted to both existing walls, and used in new wall construction to transfer loads back to more competent ground away from the main structure. This can be an economical solution, rather than completely replacing an existing structure.
Temporary Retaining Walls
Temporary retaining walls are both safe and stable, and can be constructed quickly and efficiently. They can be used to support deep excavations, for basements, shafts, and slip repairs and stabilisation. Piles for temporary retaining walls may include timber, steel UC posts either driven or drilled and concreted. Timber walers can be installed to span between piles – other methods may include placement of large concrete blocks, or slopes and may be sprayed with shotcrete over mesh reinforcement.
Concrete Ground Beams and Capping Beams
Capping beams for retaining walls transfer loads from closely spaced piles into a row of piles to link the row of piles together – they perform the same functions as pile caps. Ground beams are structural elements to connect adjacent pile caps to improve the stability of foundations.