Category Archives: Foundations

Polystyrene foundation

Polystyrene Foundation

Polystyrene can be used as part of a concrete slab foundation system. Usually the polystyrene comes in the form of expanded interlocking pods which fit into each other. The polystyrene adds to the thermal performance of the building and helps improve SAP performance which is vital to achieve in accordance with part L of the building regulations. The insulab system (BBA certified) only requires 450mm overall structural depth of combined beam and slab do there’s less concrete, less tonnage of steel, less site traffic and reduced carbon emissions. These polystyrene pods can be used with modular construction design as well as traditional methods of building. It can be used with piles & re -bar or engineered ground fill and unstable ground conditions. It can be used as a replacement to independent beam and block floor slabs found on deep trench fill foundations.

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Poor setting out can be dangerous and expensive

Setting out of  a building

A building is set out in order to clearly define the outer line of the excavation and the centre line of the wall. This can done manually or using  EDM equipment. Continue reading Poor setting out can be dangerous and expensive

Pile Integrity test – break down

Pile Details – Diameter (350mm), Type (Open Rotary Auger Bored), Material (Concrete filled), Number of piles tested (10).

Introduction – This will explain why the pile testers were asked to do the integrity test and state what type of testing will be required. For example ( Sonic Integrity testing). Sonic Integrity testing is extremely common, due to it being a fast and inexpensive method of checking for any defects that can occur within the material of pile shafts during or after installation process.

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Piling and Integrity tests

turedPiling foundation

Foundations provide support for structures by transferring loads to soil or rock that have sufficient bearing capacity. Speaking broadly,  foundations can be categorised as either shallow or deep. Deep foundations are necessary where the bearing capacity of the surface soils is insufficient to support loads so the loads are transferred to deeper layers. Pile foundations are deep foundations, and are formed by long, slender, columnar elements, typically made from steel or reinforced concrete. A foundation is described as ‘piled’ when its depth is more than three times its breadth.

Pile caps

Piles can be used individually to support loads or grouped with a reinforced cap. The pile cap should overhang the outer piles, typically by a distance of 100-150mm on all sides. Pile caps can be linked together using a reinforced concrete ground beam. Capping beams are suitable for distributing the weight of the load-bearing wall. The capping beam should be kept clear of the ground where the purpose of the piles is to overcome the problem of the subsoil swell and shrinkage. This can be done by casting the capping beam on polystyrene or other compressive material, thereby allowing upward ground movement without damage to the beam.

Pile integrity testing

The majority of cast-in-situ piles fail because of defective pile shaft necking, intrusion of foreign matters, improper toe formation due to contamination of concrete base with soil particles, leaching of concrete, discontinuity of concrete, improper construction method or poor quality control. The pile integrity test is conducted before completion of pile caps, and ensures the proper functioning of pile foundations without failure. You can use sonic echo testing to test pile integrity after installation.

The integrity test enables a number of piles to be tested in a day. The information gathered is about the continuity, crack defects, necking, soil incursions, changes in cross section and approximate pile lengths. To carry out the test, a small but hard hammer is used to produce a light tap on the top of the pile. The shock travels down the length of the pile and is reflected back from the toe of the pile and recorded through a suitable transducer/accelerometer. The primary shock wave is reflected from the toe by change in density between the concrete and the sub strata. However if the pile has any defects within its length these will set up secondary reflections which will be added to the return signal. Normally more than one recording of signals is done until repeatability of signals is achieved.