A Closer Look at Prevailing Civil Engineering Practice - European ...
A Closer Look at Prevailing Civil Engineering Practice - European ...
A Closer Look at Prevailing Civil Engineering Practice - European ...
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A <strong>Closer</strong> <strong>Look</strong> <strong>at</strong> <strong>Prevailing</strong> <strong>Civil</strong> <strong>Engineering</strong> <strong>Practice</strong>, Wh<strong>at</strong>, Why and How<br />
Vincent T. H. CHU<br />
For soils with low permeability such as clay, there is little w<strong>at</strong>er passage<br />
from slurry to excav<strong>at</strong>ed clay surface so th<strong>at</strong> filter cake would hardly be<br />
formed. As a result, slurry pressure simply applies on clay surface.<br />
14. Wh<strong>at</strong> is the function of introducing cement plug before pouring<br />
concrete in bored piles<br />
It is a common practice in the construction of bored piles by adding a<br />
cement plug before concreting of bored piles takes place. One of the<br />
possible explan<strong>at</strong>ions is th<strong>at</strong> the cement grout serves as a barrier and<br />
protects fresh concrete from being washed away by w<strong>at</strong>er inside pile bore.<br />
The cement grout helps to set aside w<strong>at</strong>er when the first b<strong>at</strong>ch of concrete<br />
is poured down from the tremie pipe. As such, the quality of fresh concrete<br />
is anticip<strong>at</strong>ed not to be seriously affected by w<strong>at</strong>er and this helps to<br />
improve toe imperfection problem.<br />
15. Wh<strong>at</strong> is the purpose of co<strong>at</strong>ing driven piles with bitumen<br />
Co<strong>at</strong>ing driven piles with bitumen serves the following purposes:<br />
(ii) It acts as friction reducer and could effective reduce the effect of<br />
downdrag.<br />
(iii) It offers protection of steel piles against acid <strong>at</strong>tack from soils.<br />
(iv) It helps to prevent pile corrosion.<br />
16. Wh<strong>at</strong> are the possible methods to reduce downdrag on piles<br />
(A) Co<strong>at</strong>ing piles with friction reducer such as bitumen.<br />
(B) Predrill a hole firstly, followed by putting in the pile and subsequent<br />
filling of annulus with bentonite slurry.<br />
(C) Drive the piles with an oversize shoe and fill the annulus with bentonite<br />
slurry.<br />
(D) Adopt double tube method in which the inner pile takes up the structural<br />
load and the outer pile carries the downdrag load.<br />
(E) Preload the soils to acceler<strong>at</strong>e settlement.<br />
(F) Use electro-osmosis to enhance w<strong>at</strong>er content around the piles and<br />
reduce the friction between pile and soils.<br />
(G) Increase the pile capacity by using larger diameter or longer length so<br />
th<strong>at</strong> the effect of downdrag is thereby reduced.<br />
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