In marine structures where piles are constantly subject to significant lateral and uplift forces induced by berthing operation and wave action, it is necessary to drive the piles to much greater depth. To avoid premature refusal so that insufficient soil cover may develop which is incapable of providing the required lateral and uplift resistance, tubular piles are normally driven open-ended so that they are driving to greater depths than piles with closed ends.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

In the design of marine piles of steel tubular piles with concrete infill, loads from pier deck are taken up by steel tubular piles before the occurrence of corrosion of steel piles above seabed. In fact, it is assumed that steel piles above seabed level will all be corroded after a certain year. The load transfer mechanism after complete corrosion of steel pile above seabed is as follows: loads from pier deck are taken up by concrete infill above the seabed level. Below the seabed level, loads would be transferred to steel piles through frictional forces between concrete infill and steel casings.

However, substantial radial shrinkage and contraction occurs after concreting of concrete infill and this will hinder the load transfer from the concrete infill to steel piles because the bond may be ruptured by radial shrinkage. It is in doubt if frictional forces can be properly developed in this situation. To solve this problem, shear keys could be installed at regular spacing inside steel piles to ensure their rigid connection with concrete infill. Alternatively, expanding agents may be adopted in concrete mixes to ensure that there is no shrinkage after the concreting process.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

The purpose of minimum toe level is two-fold:

(i) In detailed design stage, ground investigation should be conducted and the approximate level of rockhead is known. Therefore, to avoid the marine piles to be founded prematurely on boulders, minimum toe levels of marine driven piles are specified in contract.

(ii) It provides sufficient length of soils for lateral and uplift resistance.

Note: Minimum toe level refers to the minimum level that a marine driven pile should be driven into seabed.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

For marine piles, there are several options available for selection, namely H-piles, circular pipes and box piles.

However, only circular piles and box piles are suitable for marine application because of the following two reasons suggested by G. M. Cornfield (1968):

(i) Circular piles and box piles possess high column buckling strength. For marine structures like jetties, piles are well above seabed level and therefore the column buckling effect is significant when compared with other structures. Therefore, it is essential to use pile sections which have relatively high buckling strength in piers.

(ii) Circular piles and box piles display high energy absorbing capability. For marine structures like dolphins and fenders, which require substantial amount of berthing energy to be absorbed, these piles sections are inevitably good choices.

In marine structures, it appears that circular sections prevail over the box sections. The main reason is that the range of section available for selection of circular piles is more than that of box piles.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Slip joints are joints which are formed through a complete vertical plane from the cope level to the toe level of seawalls. These joints are designed in blockwork seawalls to cater for possible differential settlements between adjacent panels of seawalls. The aggregates inside the half-round channels in slip joints allow for the vertical movements induced by differential settlement and at the same time providing aggregate interlocking forces among adjacent panels of seawalls to link the panels in one unit against the lateral earth pressure exerted on seawall.

Besides, slip joints provide a path for the relief of water pressure developed and allow the lateral movement (e.g. contraction) due to seasonal variations.

Note: For details of slip joints, reference is made to CEDD Standard Drawing No. C3008C.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.