Driven cast in-situ (DCIS) piles are constructed by driving a closed-ended thick-walled steel casing into the ground and then filling it with concrete.
Bulk filling generally uses a cement/pulverised fuel ash (PFA) mix to suit site conditions with compressive strengths in the order of 1.0 N/mm2. The mixes may include sand and bentonite etc as required. Gravel is introduced to fill major voids and/or to form containment barriers.
Driven precast piles are installed using impact or vibration hammers to a design depth or resistance.
Helical piles, also known as screw piles, are constructed using steel shafts with helical flights of various sizes to suit the site specific ground conditions.
A secant pile wall consists of overlapping (secant) piles to form structural or cutoff walls and achieve the required water tightness. The design can incorporate steel bar or beams for reinforcement and anchors can provide additional lateral support, if needed.
Our sister company, Phi Group, offers a range of retaining wall and reinforced soil systems including the Permacrib gravity system; the Andacrib modular precast concrete crib system; and Gabions that use steel mesh cages filled with a large angular stone…
Contiguous pile walls consist of piles arranged in a line typically with a 150mm gap between the piles. Where required the soil between the piles can be stabilised using grouting techniques if necessary, either before or after pile installation.
Slurry walls are constructed using a cement-bentonite slurry to produce a below ground low permeability barrier.
Dynamic compaction involves the controlled impact of a crane hoisted weight, of around 10-12 tonnes, falling in a pre-determined grid pattern to improve loose, granular and mixed soils and fills.
This technique involves construction of concrete columns with a bottom-feed depth vibrator to transfer loads through weak strata to a firm underlying stratum.
Vibro compaction is a ground improvement technique that densifies clean, cohesionless granular soils with a downhole vibrator. It’s a technique first developed by Keller in the 1930s that we’ve used on thousands of projects since.
Dry soil mixing is a ground improvement technique that improves soft, high moisture clays, peats, and other weak soils, by mechanically mixing them with dry cementitious binder.
Wet soil mixing, also known as the deep mixing method, improves the characteristics of weak soils by mechanically mixing them with cementitious binder slurry.
Compaction grouting involves the injection of a low slump, mortar grout to densify loose, granular soils and stabilise subsurface voids or sinkholes.
Compensation or fracture grouting is the injection of a cement slurry grout into the soil creating and filling fractures that then lift the overlying soil and structures.
Permeation grouting, also known as cement grouting or pressure grouting, fills cracks or voids in soil and rock and permeates coarse, granular soils with flowable particulate grouts to create a cemented mass.
Ground anchors transfer tensile loads and consist of an anchor head, a free length and a bond length. Anchors can offer an advantage for basements and large excavations by minimising horizontal deflections.
Soil nailing uses grouted steel nails to reinforce in situ soils and create a gravity retaining wall for permanent or temporary excavation support.
Rock grouting is normally done in fissured rock to reduce the flow of water along the joints and discontinuities in the rock.