Wednesday, February 24, 2016

Cast insitu Bored Pile Construction

In bored pile construction , there are few widely spread methods in stabilizing the bored hole. This post discusses these methods in summary.

The most common and economical solution is to use bentonite and the main idea behind using bentonite is to stabilize the bored hole. Owing to the high density, it prevents water inflow to the hole. However, if it is a floating pile or depend significantly on skin friction to resist load then the use of bentonite is controversial.

If bentonite is not the solution then the next economical solution is to use temporary  casing. Steel casings are widely used in the industry. However extraction of the casing during the construction is challenging explicitly in deeper depths.

Inserting a temporary steel casing- checking for versatility of the steel casing using the buble

In that case you can decide for permanent casing and it has to be ensure that  you have considered the cost allocation for that. This can be decided with the specialized pile contractor.
The mix design of the  concrete using  for  piles also play a pivotal role and there are many specification on this subject. BS 6235,ACI 357,Dnv are few of them…

Generally cement water ratio is  around 0.4  for the submerged and minimum cement content would be 360 kN/m3. Minimum 28 days characteristic strength would be 35 N/mm2. Of course these are general specification and designer has the authority to adopt tailor made solution. The Portland cement is preferable and  low content of  tri calcium aluminate is preferable to reduce the risk of sulfates attacks, if it is offshore construction explicitly.
RF cages for insertion