Sheet piles are sections of sheet materials with interlocking edges that are driven into the ground to provide earth retention and excavation support. Sheet piles are most commonly made of steel, but can also be formed of timber or reinforced concrete.

Sheet piles are commonly used for retaining walls, land reclamation, underground structures such as car parks and basements, in marine locations for riverbank protection, seawalls, cofferdams, and so on.

The selection of sheet piling is dependent on factors, such as:

• Whether it is permanent or temporary.
• Site conditions.
• The required depth of piles.
• The bending moments involved.
• The nature of the structure.
• The type of protection required.

Next Spaces is experienced in designing and building hard/soft, hard/firm and hard/hard secant walls using continuous flight auger techniques or segmental casings for applications of 750mm pile diameters upwards.

The development of powerful high torque drilling equipment has led to an increase in the range of ground conditions and obstructions that can be penetrated and the wall thicknesses that can be constructed. We are therefore able to install secant walls in the most challenging urban environment.

Where soils are saturated and water tightness is a requirement, secant walls using either bentonite cement materials (soft) or weaker concrete (firm) are used in combination with reinforced concrete (hard) piles. These alternatives are generally used where temporary works are required.

Permanent retention can be provided with all reinforced piles (hard/hard), which can be incorporated within the final structure.

Piles in a secant wall are spaced at 0.8 to 0.9 pile diameters. Primary piles are secant by secondary piles, thus providing a closed structure to act as a barrier in water bearing soils, and to prevent the ingress of soil between the piles.

Secant piling offers minimal vibration, low noise levels and the flexibility to fit complex site boundaries to maximise land use. Secant piling also has the ability to go through underground obstructions such as steel, heavily reinforced concrete, granite and masonry, while at the same time, avoiding any risk of construction induced settlements to neighbouring structures.

This process of blending soil with selected materials can produce a modified or re‐engineered soil that has strength, non‐permeability and/or elasticity. The process is achieved by installing specialised jetting equipment down conventionally drilled small diameter holes of no more than 150mm. There is great flexibility in the choice of borehole entry points which allows the formation below ground to consist of complex geometrical shapes of treatment by combination of overlapping individual treatment zones. This can be particularly useful in the built up urban environment where both surface and underground obstructions may occur and where other conventional construction methods and excavations can’t be utilised.

The process of forming jet grout columns can be used in a number of applications such as underpinning existing buildings, forming watertight cut offs, basements, tunnel and shaft construction, foundations and deep slabs.

Diaphragm walls provide rigid, cost effective solutions for permanent retaining walls and shafts, with less construction joints than bored pile walls. They are particularly suitable for large, more open sites where structures greater than 25m deep are required. The underground diaphragm wall technique offers improved verticality tolerances to CFA and rotary bored piling, up to 1:400 for hydrofraise, and delivers a smoother finish. Water tightness is normally delivered using a CWS water bar between the diaphragm wall panels.

Diaphragm walls are constructed as permanent walls, which reduces the width of construction and working space required when compared to a solution that has both a temporary ground support and permanent works within. Walls can be made extremely stiff and therefore better resistant to deflection. It is also possible to use effective internal propping with a diaphragm wall rather than the normal ground anchors. Temporary cut‐offs can also be created using this technique.

CFA (Continuous Flight Auger) piles are quick to install and offer an efficient, rapid solution for predominantly more lightly loaded structures.

Favorable Geotechnical Conditions:

• Medium to very stiff clay soils.
• Cemented sands or weak limestone.
• Medium dense to dense silty sands and well‐graded sands.
• Rock overlain by stiff or cemented deposits.

We define piles larger than 600mm diameter to be a large diameter.

L.D.A. Hydraulic Rotary Rig machines tend to be higher in power (torque) than CFA Rig Machines and are more able to overcome underground obstructions. Rotary piles have the ability to: quickly change coring or digging tools and auger type; have plunge columns installed into them; be under‐reamed to facilitate higher base capacity. Bored rotary piles also have the advantage of having the reinforcement cage installed into the open bore, and so can accommodate full length reinforcement. We have the capabilities to produce piles up to 2800mm in diameter and to depths up to 66m.

We have extensive experience in the design and construction of structural retaining walls for all temporary and permanent requirements. Bored pile walls (contiguous or secant) can be the ideal solution for more restricted sites when the wall is constructed using continuous flight auger techniques or with temporary casings.

We have designed and built a number of hybrid retaining walls in appropriate ground conditions as cost effective alternatives to sheet piling. Bored piles can be constructed through bentonite cement slurry with lateral loading on the wall carried by “arching” between the bearing piles. This can provide a very reliable temporary works solution.

In dry stable soils, contiguous bored pile walls can be constructed. This type of wall is a series of piles with intervening gaps which provide an effective retention solution. Individual piles are spaced at 1.1 to 2 piles diameters apart in a phased sequence.

We have developed a patented TMD system for soil anchors. TMD is a type of ground anchor that delivers increased capacity over conventional techniques by repeated post grouting.

It is a permanent anchorage formed using a single corrosion protected anchor, grouted within a Tube a Manchette (TaM) pipe, which is then grouted into the soil. The TaM pipe acts as the second layer of corrosion protection whilst also facilitating the injection of grout into the surrounding soil. The grout permeates into and consolidates the soil, permitting a greater bond strength between the soil and the TaM pipe that could not be otherwise achieved between the soil and the anchor alone. The system provides a high level of corrosion resistance coupled with a high load pull out capacity.

Deep cement mixing (DCM) is a civil engineering deep foundation technique where a binder material, typically cement, is injected into the ground for ground stabilization and land reclamation. In ground stabilization applications it is typically used to obtain a better load bearing capability of the existing soil, e.g. in order to bear buildings and other structures. In land reclamation applications it is typically used when cheaper techniques such as dredging or draining cannot be applied because of environmental concerns due to contaminated soil that these two techniques would release.