Soil test and stump option

[mullfitz]

If your soil test said this

(in brief)

5.0 CONSTRUCTION RECOMMENDATIONS
(a)
Due to the presence of bedrock at relatively shallow depths on this site it is likely that significant to extreme difficulty may be encountered when undertaking excavations into this rock. It should also be noted that it is possible that rock breaking equipment and/or blasting may be required if excavations into the bedrock are proposed at this site.
Note that where naturally occurring rock makes it difficult to excavate the footing/slab beam trenches to the full depth required, the footing/slab beam may be replaced by a leveling pad of mortar or concrete in accordance with clause 3.1.8 of AS 2870 1996.

Which stumping system would you use

http://www.mega-anchor.com.au/ or http://www.bluescopesteel.com.au/go/product/lysaght-uni-pier

would like your thoughts
cheers

[brynk]

gday
the mega-anchor's are a driven pile which would be interfered with by encountering rock if they did not achieve some minimum depth (say, 400). with regards to uni-pier you still need to anchor them to the rock somehow.

if you can drill the rock then you could set bolts with a chemical anchor. get your bolts level & square then you can bolt a base-plate for a column. or if you are a welder you can bolt a plate directly to the rock then cut & weld the column to this plate. obviously both these methods are labour-intensive.

if you can't drill the rock then you can clean the rock face thoroughly of dust & cast a pad-footing to it with concrete. pour a good amount of pva glue onto the rock-face just before you pour your concrete for extra bonding strength. you can cast bolts into the concrete itself or drill bolts into the footings once the concrete has been curing for 7 days or so. you can then attach the uni-piers to these, or for that matter any of the standard or cyclone stirrups could be cast onto these footings or bolted to the pad itself.

if you strike the shallow rock you encounter with the crow-bar you'll feel the vibrations under your feet if the rock is of size. this will give you an indication of how big it is. consider it sufficient if it is roughly the size (or larger) of your required pad-footing bearing area ...

r's brynk