Tod Response · OPW16/0021

CASE STUDY PCA ._._ CASE STUDY Aer

WT GROUND ENGINEERING HT A LLL)

EARTH RETENTION | PILING | GROUTING | ENGINEERING GROUND IMPROVEMENT | CIVIL CONSTRUCTION EARTH RETENTION | PILING | GROUTING | ENGINEERING GROUND IMPROVEMENT | CIVIL CONSTRUCTION

 

PROJECT TYPE: Shoring Wall for Basement Excavation

  
   
 
 
 

CLIENT: Alan Marks
MAIN CONTRACTORS: PCA
PROJECT ENGINEERS: AB Consulting Engineers

Two drill rigs were used. One was used to install the grout columns while the
other installed the 6m long universal beams

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PROJECT DESCRIPTION AND CHALLENGES

Sovereign Island has been reclaimed using dredge spoil from the Coomera River and Gold Coast Broadwater. The typical

geotechnical profile for residential house lots includes several metres of loose sand overlying layers of loose and dense sand to a
significant depth. Houses are also built using the largest footprint possible which generally see them constructed to within 1.5m
or so of the boundary. This close proximity to the boundary makes excavating a basement very tricky and usually requires some
form of temporary or permanent shoring. High pressure grouting was used to increase pile diameters to 400mm.

The project in Hampton Court at Sovereign Island had the added difficulty of a concrete fence which was installed on shallow
foundations on the property boundary which required an excavation to within 500mm. Sheet piles or any other method that -
involved vibration were ruled out due to potential damage to the neighbouring fence and house. ( (

adjusted to determine the change in pile diameter

The challenge was to design and construct a temporary shoring wall that could retain a 2.5m excavation using equipment and aes - med ‘ = =
techniques that did not harm the adjacent property. | | | E | aC , A A | IV A N 1 AG E

The low vibration and high pressure grouting techniques utilised by PCA are perfectly suited to tight sites and boundary wall construction
where there are concerns over potential damage to adjacent structures.

With a cost that was equivalent to installing sheet piles, the Hampton Court shoring wall project on Sovereign Island was a robust solution

T H E S O L U T | O N with a small footprint that enabled the outer basement to be waterproofed prior to backfilling.
A contiguous wall made up of a series of overlapping grout columns was installed using high pressure drilling and grouting Having access to multiple drill rigs with state of the art grouting equipment enabled this project to be delivered on time and within budget
techniques. The sandy soil allowed for the use of a small diameter drill string (62mm) with a high pressure drill bit that created a with no variation claims or damage to the two adjoining properties.

sand/grout mixed series of 400mm diameter piles to a depth of up to 6m.

The computer controlled mobile grout plant was able to pump grout at pressures up to 100 bar and 55L/min to cut and mix the
sand and grout together to create a continuous diaphragm for the full length of the wall. Universal beams were installed at
between 900mm and 1200mm centres to resist the overturning forces of the structure with N16 bars plunged down the
intermediate grout columns to provide some additional shear strength.

 

 

PO Box 1605 Runaway Bay QLD 4216 * Phone: 07 5500 5898
Fax: 07 3041 6068
Email: [email protected] www.pcacontracting.com.au

PO Box 1605 Runaway Bay QLD 4216 « Phone: 07 5500 5898
Fax: 07 3041 6068
Email: [email protected] www.pcacontracting.com.au