Where structural requirements dictate higher bearing loads, increased pile diameters greater than 1200mm can be provided through the use of higher torque (power) rotary bored piling rigs.
Challenging ground conditions such as heavy boulders and rock may also require such techniques to penetrate to design levels. Support to the surrounding ground in the temporary condition, prior to concreting, can be achieved by the use of steel casing installed either segmentally or in single lengths, depending upon the underlying ground. Present day high torque rotary rigs that are utilised in rotary bored piling, are capable of installing their own segmental casing, screwing it into the ground ahead of spoil excavation. Single lengths where used, are generally installed using an attendant crane and driven by a vibratory piling hammer.
Once the designed pile bore excavation has been achieved; prefabricated steel reinforcement cages are placed either on the bore base or suspended at the required depth within the pile. Concreting of the bore then proceeds down a centrally positioned tremie tube from the pile base in order to ensure no mix segregation and adequate final compaction.
Rotary bored piling techniques have the advantage over CFA bored piles, in that they can be used in more variable and cemented rocks and soils and a number of different coring or digging tools may be used to overcome such obstructions.
VolkerGround Engineering has the capability of drilling piles to 3000mm diameter, and depths of 66m, which are able to carry significant loads and overcome a variety of difficult ground conditions.
Where ground conditions or environmental constraints mean that driven steel sheet piles cannot be used to provide a retaining wall solution, VolkerGround Engineering is able to design and construct concrete bored pile walls utilising either rotary bored or CFA piling plant depending upon structural requirements and ground conditions.
Different forms of wall construction technique are available depending on specific project requirements:
In order to ensure the high verticality tolerances and maximum water tightness; we recommend that secant walls be constructed through concrete guide walls cast ahead of piling works. This is not required with contiguous walls, where water tightness considerations are not relevant.
A hard/firm secant wall cannot be considered as a permanent water tight structure therefore any basement will require a drained cavity to be provided between it and an internal wall.
Where the retaining wall is to be incorporated within the permanent basement then consideration should be given to either a hard/hard secant (both piles contain reinforcement) or diaphragm wall.
Whatever your requirement, our team can advise on the best solution – steel driven, concrete bored, or a combination of both. Our design solutions are not driven by our plant holding; but rather the cost effectiveness for our clients.