Retaining Specialists

Retaining Specialists is a company based in Sydney that designs, supplies and constructs all facets of soil and rock stabilization throughout NSW. The company stabilizes, underpins, and puts anchors into ground to retain and solve numerous types of construction issues.
The services provided are in these construction areas: * Retaining Walls  * Underpinning  * Slope stabilisation. The clients are from these market segments: *  Domestic  * Local Government  * State Government.
Specialist construction services are focused on three Core Areas: Retaining Walls, Underpinning, Slope Stabilisation.

1. Retaining Walls: → Block work Retaining Walls: →  Concrete Crib Retaining Walls: →  Concrete Sleeper Retaining Walls: →  Gabion Retaining Walls: →  Re-enforced Earth Segmental Block Retaining Walls:

2. Underpinning: The use of advanced geotechnical ground stabilisation including micro fine cement, grout compaction, and conventional 1-3 2- 4 techniques are used in underpinning. Is worth noting that Retaining Specialists do lump sum budgeting for underpinning - taking on the risk of the work they undertake.

3. Slope stabilisation: The most common stabilisation issues involve the prevention or remediation of land slips or collapsed excavations (on either man-made slopes or natural slopes). The process of remediating landslips involves shotcrete and anchors with drainage. Abatements and cut excavation are mostly stabilised using piles, shotcrete and anchors.

Skilled Services and Processes used in construction projects:

Shotcrete: A process where concrete is conveyed through a hose and pneumatically projected at high velocity onto a surface, as a construction technique. Shotcrete undergoes placement and compaction at the same time due to the force with which it is projected from the nozzle. It can be impacted onto any type or shape of surface, including vertical or overhead areas.

Rock Bolting: the installation of a threaded bar or a tendon drilled into a whole into rock to bolt a loose piece rock onto stable substrate.

Soil Nailing:  the reinforcement of the soil by drilling holes and installing a tendon commonly a threaded bar or a cable and then fastened onto the these sure surface and the tension soil surface under tension

Micro-piling: Micro piles can typically be installed using small scale piling rigs able to work in limited access or for low headroom piling. It can be used for foundation upgrades, refurbishment works, temporary and permanent piling applications for both tension and compression loading and are well suited to a wide variety of ground conditions. They can be installed with small piling rigs and can be raked or angled

Micro-fine Cement Injection: Cement grouts suitable for pressurised soil permeation injection. There are many different types of permeation cement grouts and manufacturers. Some are designed for varying types of void filling; others are designed for differing degrees of soil permeation

Grout Compaction: Compaction grouting uses low mobility grouts to rapidly improve discrete zones of soft or loose soils. The method provides a low cost, low risk solution for underpinning, liquefaction mitigation and re-levelling 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.

Anchors and Anchoring:
•    Earth & Rock Anchors; 
•    Plate Anchors;  
•    Platypus, 
•    Manta, 
•    Tighter Anchors.

Other specialist skills: Tight access excavation: Railway sidings work.

Council received a report from a resident regarding failure of rock face in Clontarf. Staff inspected the site and engaged a geotechnical consultant to investigate the stability of the rock face and provide remedial measures to repair the failed section of the rock face.

Council recommended the remedial messages be undertaken at the location to improve the rock face by protecting the face of a cutting from erosion by the application of shotcrete, mesh and rock bolts and engaged Retaining Specialist for this job. Traffic management was essential on these narrow busy roads and work was completed in four days causing a minimal disruption to residents.

Shotcrete 850m2 @130mm thick = 110cubic meters of concrete.

Dowels 12mm black deformed barBetween 3 & 4 dowels per lineal meter, 1m long for a distance of 260lineals, comprising black N12 bar (approx. 800-900 dowels).

Mesh SL 82  Approx. 70-75 black SL82 sheets of mesh allowing for overlap.

Major Landslip: Approximately 77km west of Grafton, in the Gibraltar Ranges over a hairpin bend where the road switches back above its-self, the Highway was closed, due to major landslips after heavy rains (estimated at 300 mm to 450mm-more than1 foot), post cyclone Oswald (several landslides occurred in the mountain range at that time).
NSW Roads and Maritime Services (RMS) cleaned the landslip debris off the road, opening one lane of the highway, and, a team of engineers comprising Davies Geotechnical & Coffey Geotechnical investigated the stability of the mountain in several areas. Geotechnical drilling encountered construction fill over angular colluvium in stiff clayey-sandy Silt. Rock was highly fractured variably weathered low to high strength Meta siltstones, Meta sandstones and Quartzite. A number of voids/cavities were encountered. An irregular bouldery layer was encountered overlying the highly irregular bedrock surface. This layer was thought to be a potential conduit for ground water and conceivably a shear plane/weak zone for a landslip.

Tension cracking was observed on the shoulder adjacent to the edge of the top road above the scarp zone. Strong flows of ground water were encountered at two locations in the scarp zone where large outlet holes were encountered. During subsequent heavy rainfalls, flows of 150litres per minute were observed gushing from these holes. The bottom road was covered by debris and suffered deep erosional scouring of the bottom road fill embankment. The landslip comprised a combination of rotational and translational slide with in the mountain slope colluvium deposited over thousands of years. A debris channel 150m long and up to 45m wide cut a swathe through the forest linking the upper and lower sections of the road switch back, and there is a risk that debris from the landslip could remobilise during future peak rainfall events and cover the lower road again. The RMS completed temporary work to stabilise the lower road section of the landslide by clearing dirt and make the upper section safe for one lane to operate.

Engineering and Construction Approach: Retaining Specialists Pty Ltd was contracted by the RMS to commence repair work on the major landslip, in January 2014 and by July 2014 the permanent stabilisation works had been completed. The upper road downslope embankment had tension cracks and most of its support removed by the landslip. The scarp face needed to be engineered to restore support to the upper road. An in depth geotechnical investigation was undertaken for the design, which included a very high level of geotechnical oversight during construction.

Two main solutions were considered: -piling and anchored shotcrete.  Due to the inherent instability of the slope and the weight of piling equipment, the piling option was rejected. 

Due to the low inherent slope stability of the failed slope, a 7KPa load limit (platform surcharge) was placed on the working face; to increase the load bearing capacity (ground pressure), the first row of anchors were constructed with high tensile strength threaded bar. 

To minimise adverse impacts on the existing slope during the rock nail installation Retaining Specialists had to consider the weight of plant and methods of distributing the load on the working surface and construction benches.

To whom it may concern: Retaining Specialists
We had the pleasure of working with Neal and his team on a retaining wall at our property in Hornsby. 

For our project, time was certainly of the essence.  The retaining wall had to be built so we could complete other works in our backyard, in anticipation of the sale of our property.  Neal and his team certainly delivered on that score - they delivered the project well within schedule. Neal is very accessible.  He was always very open to discuss the project, and to answer our many and varied questions.
Neal provided guidance and assistance with the DA process.  He worked well with the certifier.  As a registered engineer, Neal was also able to provide a certificate to finalise the certification process.  This was absolutely vital to us.

A specific issue for us was site access.  Quite late into the project, we realised that we would face very steep traffic management costs, because of the need for trucks to be parked on street.  Neal and his team managed to find a solution to the issue, which greatly reduced the financial impact for us.

Neal was also very mindful of the final finish.  He provided sound advice on colour treatment, and also final finish.  Neal clearly understood the wider importance of the retaining wall to our property sale.  We had some initial fear that the retaining wall would be an eyesore. 
Instead, it turned out to be a feature of our backyard.  It was in actual fact a selling point within our marketing campaign.
I have no hesitation in recommending Neal and his team.

Yours sincerely
Nicholas Vesic