Planning for the Future – Ground Improvement Trials at The Port of 19

PETER BOYLE, JAY AMERATUNGA, CYNTHIA DE BOK AND BILL TRANBERG

PLANNING FOR THE FUTURE – GROUND IMPROVEMENT TRIALS AT THE PORT OF BRISBANE

ABSTRACT there is a critical need to accelerate the about their works during the design and consolidation of the reclaimed land as installation phases. This paper was first The Port of Brisbane is located at the traditional surcharging used at the Port in the presented at the Coasts & Ports 2007 mouth of the at Fisherman past will not meet the future development Conference, Melbourne, Australia in July 2007 Islands in Brisbane. In recent years, Port land timelines. In order to optimise various and is published here in an adapted version has seen rapid development as a result of ground improvement techniques and assess with permission. increased trade growth. This growth in the their suitability for the local conditions, South East region is expected the Port of Brisbane Corporation invited to continue for the next 25 years and expressions of interest from specialist INTRODUCTION beyond. The expansion and development ground improvement contractors for the of future Port land will see the reclamation design, supply and installation of ground The Port of Brisbane is located at the mouth of about 235 ha of existing tidal flats improvement techniques to carry out full of the Brisbane River at Fisherman Islands. bounded by the FPE (Future Port Expansion) scale trials in the existing reclaimed land. In recent years, the modern purpose-built Seawall which was constructed to contain Based on this process three internationally Port has seen rapid development as a result the reclamation. The reclamation will be known contractors were appointed to of increased trade growth. This growth in carried out using channel maintenance conduct trials using wick drains and vacuum the South East Queensland region is expected dredging materials consisting of river muds consolidation. Relevant performance criteria to continue for the next 25 years and capped with , as has been the past were established to assess performance beyond. The expansion and development practice. The seabed conditions, however, throughout the design and installation of future Port land is critical to ensure that are significantly different in the seawall area phases to enable a successful Trialist and the Port’s facilities can expand at a rate to because of the high water table, in-situ system or systems to be selected next year to meet this growth. In 1999 the Port compressible clays over 30 metres deep and start the broad-scale roll-out programme. embarked on plans to investigate the the increased thickness of up to 7 to 9 metres expansion of a 235 ha area immediately of river muds to be deposited into the Port of Brisbane Corporation and Coffey to the east of the existing reclaimed area. reclamation. Geotechnics wish to acknowledge the professional and cooperative manner in which In 2002, an Alliance Contract was formed Whilst historically it has taken about 10 years the three Trialists, namely, Van Oord, Boskalis between Port of Brisbane Corporation (PBC), for reclaimed land to be available for Australia and Austress Menard have gone geotechnical consultants Coffey Geotechnics commercial use, it is currently anticipated (CG), coastal engineers WBM Oceanics, that this timeline will have to reduce to less Above, Aerial view of the Port of Brisbane showing civil consultants Parsons Brinckerhoff and than 5 years to meet demand. Therefore the reclamation areas including the trial areas. constructor Leighton Contractors, to deliver 20 Terra et Aqua | Number 108 | September 2007

Figure 1. Site layout.

the Future Port Expansion (FPE) Seawall, of up to 7 m to 9 m of river muds to be dredged annually and must be disposed of a 4.6 km long perimeter rockwall which deposited into the reclamation. Generally in an environmentally friendly manner encloses the future expansion area. consolidation timings for these undeveloped within the Port’s reclamation areas. The Seawall construction, being the first stage areas are predicted to be in excess of in the expansion process, was completed in 50 years if surcharging is the only treatment Substantial research and investigation by PBC early 2005 (Ameratunga et al. 2003 and employed, as has been past practice. and CG into local and overseas practices of Andrews et al. 2005). PBC has since Settlements in the range of 2.5 m to 4 m treatment of soft found that two main engaged CG as their geotechnical advisor are also forecast. Given the pressures of groupings of techniques are available to for development of the reclamation areas. creating additional usable Port land in time treat and improve the reclamation sediment frames approximately half of those achieved and in-situ . in the past, a decision was taken that new CREATION OF NEW PORT LANDS techniques to speed up the consolidation Groupings of available ground process need to be employed to meet the treatments The Seawall allows for the containment of timings. Apart from conventional surcharging, the progressive reclamation of about 235 ha techniques to improve the ground can be of existing sub-tidal flats. The reclamation will grouped into two main areas, namely: be carried out using channel maintenance and TREATMENTS TO SPEED UP LAND 1. Consolidation of the soft highly berth dredging materials consisting of several CREATION compressible soils by installing vertical metres of river mud capped off with sand. drains or using vacuum consolidation At the existing reclamation area (Figure 1) Clearly, filling the reclamation areas with with surcharging or; approximately 60 ha remains to be sand sourced from the 2. Improve, reinforce or stabilise the soils developed (in 2006-2007), but is at a more channels instead of dredged mud would to reduce settlements and improve shear advanced state of filling and capping than reduce the total thickness of soft and strength and stiffness. the FPE area. The subsurface conditions in therefore minimise the impacts of filling the the seawall area and the existing reclama- reclamation areas. The suite of techniques falling under group 1 tion area are significantly different from the comprises the installation of vertical drains, developed areas (Figure 1), because of the However, as PBC must maintain navigable including sand drains or prefabricated vertical high water table, in-situ compressible clays depths in its river channels and berths, drains (PVDs), in a square or triangular over 30 m thick and the increased thickness some 500.000 m3 of mud on average is pattern, generally spaced at 1 m to 2 m. Planning for the Future – Ground Improvement Trials at The Port of Brisbane 21

PETER BOYLE Vacuum consolidation is a process whereby available under group 2 are considered to holds a Queensland University of a vacuum pressure is applied to an area have merit in special situations such as Technology (QUT) civil engineering degree already installed with pvd’s to potentially edge treatments for berths or surcharge and is a Fellow of the Institution of increase their effectiveness. Generally all stability. The mixing of techniques from Engineers, Australia. He has over 25 years techniques here require the application of a both groups, however, poses difficulties at of experience in the public and private surcharge loading to squeeze water out of transition zones which would need to be sectors covering all facets of port the soft clay soils. Such loading must be carefully considered. development. He was the Alliance Design equal to or in excess of the service loading Manager for the construction of the the developed land will be subjected to. Port of Brisbane’s FPE Seawall Project. In vacuum consolidation, the vacuum pressure EXISTING GROUND CONDITIONS AND He currently has the lead technical role in applied contributes to the surcharge loading, DESIGN PARAMETERS the reclamation and development of some and therefore actual surcharge heights are 300 hectares of future Port Lands. reduced. An additional important advantage Target service loading and settlement of the vacuum is the isotropic nature of criteria the vacuum pressure and the correlated Historically, ground treatment for the Port’s JAY AMERATUNGA improvement of the stability under preloading, developed existing reclamation area was obtained his BSc degree from the reducing considerably the risk of slope designed for an in-service settlement University of Sri Lanka, MEng from AIT, failure resulting from the surcharge. criterion after construction of 150 mm in Bangkok and PhD from Monash University 20 years. This criterion was associated with in Australia. He has over 30 years Methods falling under group 2 include nominated design service loadings applied experience and is currently a Senior stone columns, piling the ground, mass to the adopted finished design pavement Principal at Coffey Geotechnics Pty Ltd, mixing the soils, or local mixing of the soils levels as follows: Queensland. His expertise is in the areas over some form of grid by soil mixing. • 36 kPa at marine terminal areas of soft soils, construction and numerical Where a grid of columns, piles, or in-situ • 15 kPa at warehousing areas and analysis, and he works predominantly on mixed columns is used, a bridging mattress corridors. infrastructure and marginal lands projects. may be required across the site to transfer the surface loadings into the discrete soil In planning for the future, however, PBC is supports. Significantly less or no surcharging considering increasing the design service CYNTHIA DE BOK is required with these techniques, and they loading of the marine terminals for future received her BSc and MSc in engineering generally provide a significant time saving. berths up to 50-60 kPa. Further, new land , from the Delft University of However, these treatments are typically zoning of integrated logistics has been Technology (TU Delft), the Netherlands. more costly. In certain parts of the world, created, sandwiched between the marine She joined Coffey Geotechnics Pty Ltd, freezing of the ground can even be terminals and warehousing zones, with an Queensland in 2004 and initially worked considered as a viable solution. applicable design service loading of 36 kPa. on the Wivenhoe Dam project before This new zone covers areas previously taking on the challenge of the Selection of Preferred Treatment gazetted as warehousing and subjected to geotechnical design and coordination Solutions a design service load of only 15 kPa. The activities for the Port of Brisbane’s Consideration was given to the most likely increased service loadings, if adopted pose Ground Improvement Trials. treatment technique applicable for use in a further challenges to the land development broad scale application. The conclusion was process in the new areas. Current thinking that the techniques available under group 1 is that PBC may need to adopt two BILL TRANBERG would most likely be best suited for broad acceptance target service criteria in future holds a civil engineering degree and a scale treatment. In addition they would as follows: PhD in engineering from the University pose no boundary differences with present • Where the total thickness of of Queensland and is a Fellow of the sites, where land consolidation techniques compressible clays and mud is less than Institution of Engineers, Australia. using surcharging alone have occurred. a nominated thickness, say 10 m to He has been involved with port With relevance to the Port of Brisbane 15 m, retain 150 mm residual settlement planning, design and construction reclamation area, group 1 techniques i.e. in 20 years of service; activities at the port for over 25 years. PVDs, shaped as the preferred treatment • Where the total thickness exceeds the A recent highlight was the 4.6 km long over vacuum for mass application, primarily nominated thickness adopt an increased FPE Seawall project, enclosing a because of the necessity of a 15 m deep target of 250 mm in 20 years of service. reclamation area of 235 hectares. -off wall to mitigate the local site Bill currently has technical oversight conditions (i.e. the occurrence of sandy Currently it is considered that a target of of all engineering development works layers) at the paddocks. Conversely, the 150 mm of residual settlement may not be for the Port of Brisbane Corporation. vacuum consolidation process and solutions feasible when using group 1 techniques, 22 Terra et Aqua | Number 108 | September 2007

Figure 2. Basal surface of Holocene layer (in m RL, with RL 0m equal to Low Water Port Datum).

particularly where soft compressible clay Table I. Geological Units thicknesses including mud can total in excess of 30 metres. In such cases the Unit Description creep settlement contribution from the Recent Dredged mud, marine and dune with layers of and clay. deeper layers, which may be only slightly This material may include fill, including dredged fill. over-consolidated with respect to the design service loading, may be significant Holocene Normally consolidated marine clay, silt and sand. and may not be easily built out. Pleistocene Generally over-consolidated clay, sand and . Tertiary Weathered basalt of the Petrie Formation. Geological Units In the existing reclamation and FPE areas, four distinct geological units have been coarse grained sand with interbedded Pleistocene sediments recognised and they are listed from the layers of silt and clay. Shell layers may also The Pleistocene layer is an older alluvial top down in Table 1 and are described below. be present. Material dredged from the river deposit below the Holocene deposit and channels are deposited in the paddocks comprises mainly over consolidated, very The most compressible units at the site are: from a single point discharge, generating stiff to hard clays and medium dense to • Recent unit (dredged mud layer) variable profiles in deposited materials. dense sands and gravel immediately • Holocene unit (clay layers) overlying the bedrock. The compressibility Holocene sediments of these materials is relatively low In Figure 2 the basal surface of the Previous investigations have subdivided the compared to the soft/firm clays of the Holocene unit underlying the study areas is Holocene sediments into an Upper and Holocene deposit. shown in relative levels. The final design Lower layer of low strength silty clay with surface elevations of the paddocks vary shell bands (“marine clay”) separated by a Tertiary basalt from 6m to 9m RL. discontinuous layer of sand. The Upper The weathered basalt bedrock of the Petrie Holocene layer generally consists of sand Formation underlies the site and is described Recent sediments layers interspersed with layers of soft clays as grey-green clay (extremely weathered These materials generally consist of modern and . Sand layers or lenses are relatively basalt) downwards into dark grey dune and beach deposits and dredged fill. few or absent within the Lower Holocene to black, moderately to slightly weathered The soil types consist of silt, clay and fine to layer. basalt. Planning for the Future – Ground Improvement Trials at The Port of Brisbane 23

Preliminary Geotechnical Parameters resulting in cost effective and optimum than further reducing the number of trials Based on initial ground investigations of the treatment solutions. Whilst the EOI and trialists from 3 to 2 or even to 1. study areas an average set of geotechnical document permitted any and all solutions, Also, plans to develop future Berths 11 material parameters for the dredged mud it did indicate that vertical drains including and 12 and associated backup lands further and the Holocene clay was chosen. It also PVDs and sand drains were likely solutions. advanced as the EOI process progressed. enabled the creation of basic soil models at Sand drains were included on account of Accordingly PBC decided to expand the the various study sites. These details were the ready availability of sand at the Port trials scheme previously proposed to include included in the documentation package sourced from the bay shipping channels. three trialists and trial PVDs over 3 sites to be issued to the various prospective of 3 ha each with a further special edge Contractors to enable them to undertake To enable the actual performance and area of 2.5 ha set aside for a vacuum system selection and preliminary designs cost of any proposed ground treatment consolidation trial. The successful trialists and provide associated pricing applicable to solution put forward by Contractors to included three international companies: their systems and solutions. Creating such be evaluated, the EOI document proposed Van Oord, Boskalis Australia and Austress details would enable CG and PBC to make that one or two suitably qualified short Menard (Menard). Contracts were fair comparisons between any proposals listed Contractors would be selected and subsequently successfully negotiated with received for ground improvement works. allowed to trial their systems on a four (4) each Trialist. hectare site. The documentation sought These investigations also indicated low values that Contractors provide preliminary costed In addition, a scheme of assessment for the for the coefficient of consolidation (ch), designs and forecasts within their proposals Trials during the design and construction compared to previous results for the dredged for their systems of ground improvement phase was established and agreed with all mud layer and the Lower Holocene layer. based on the initial geotechnical para- three trialists. These criteria are largely

The ch relates to the dissipation rate of meters and basic soil models provided by based on expanding upon the criteria water from the clay and therefore together CG and PBC and other relevant information contained in Table II. It is further proposed with the clay thickness and presence of contained in the EOI documentation. to place a control or reference surcharge sand layers determines the consolidation , fully instrumented but time. Settlement information from other Assessment of proposals received without PVDs, for performance comparison older reclamation paddocks tends to indicate At the closing of EOI submissions, eight purposes. higher rates of dissipation, likely to be due proposals were received. Proposals were to greater distribution of sand lenses within received from both local and overseas the dredged mud layer. Contractors. Overseas Contractors from TRIALS PROGRAMME The Netherlands, Germany, France and SE Asia were keen to offer their respective A 3 ha site was provided to each Trialist for METHODOLOGY FOR SELECTION OF expertise. The submissions received PVD installation. Each Trialist was given the OPTIMAL GROUND IMPROVEMENT generally supported the use of PVDs as opportunity to propose a trial scheme SYSTEM the preferred solution for the Port sites. which would generally enable maximum learnings for each. The design proposals After due consideration of all known The EOI document contained six selection put forward by the companies have shown a available ground treatment techniques, criteria that Contractors were advised large degree of thought and individualism. PBC decided to invite Expressions of would have their proposals assessed The trials utilise several different PVDs, Interest (EOI) from specialist ground against. These criteria are listed in Table II. varying both in core and filter type and a improvement Contractors, either local or range of different spacings. from overseas, interested in providing PBC and CG assessed all Proposals received services for the design, supply, installation by scoring them against the selection Boskalis is also trialling its BeauDrain-S and monitoring of suitable specialist criteria. This resulted in the short-listing vacuum consolidation system, which is an ground improvement systems to the of three preferred proposals. These three Australian first. Menard is trialling their existing reclamation areas at the Port of submissions could not be substantially proprietary vacuum consolidation system Brisbane. separated in terms of the selection criteria, along a special edge site. The system with all three offering PVD solutions. proposed includes a cut-off wall around the Expressions of interest Two of the three Contractors offered perimeter of the site to cut off the effects The EOI document indicated that such systems vacuum consolidation systems as possible of sand lenses in the upper Holocene layer. should enable the reclaimed areas to be solutions in addition to PVDs. This is the first such application in Australia. developed by the Port in a considerably A Menard vacuum system, without a shorter time frame than that achieved by Trials scheme adopted cut-off wall, is currently installed in the surcharging alone, providing acceptable PBC decided that there was considerable Ballina By-Pass Project, located in New in-service settlements and at the same time merit in trialling all three Contractors rather South Wales, Australia. 24 Terra et Aqua | Number 108 | September 2007

Table II. EOI assessment criteria Criteria Issues

Overall Price One of the key factors in the assessment will be the all-up price for the ground improvement treatment system, i.e. including all surcharging costs, monitoring, etc. Past experience as designer & installer of A Proponent who has a demonstrated history as a proven ground improvement specialist ground improvement systems with sound results in projects similar to that to be undertaken at the Port of Brisbane will be ranked highly against this criterion. This will also include expertise of personnel nominated to work on the project(s). Ability to meet or exceed design criteria Proponents who can deliver the works to PBC’s preferred timelines whilst meeting the set and timings nominated criteria for the project will be ranked highly against this criterion. Ability to identify all risks and provide acceptable contingency measures will also rank highly. Proponent’s Financial capacity Proponents will need to demonstrate an adequate financial capacity to undertake the project to be ranked highly against this criterion. Warranties or Performance Guarantees Proponents who submit warranties or performance guarantees to deliver the areas within the residual settlement criteria nominated under the nominated loadings and design criteria will be highly ranked.

QA, Environmental, and Loss Control systems PBC is strongly committed to ensuring all its activities are carried out to the highest possible standards, including those relating to health, safety and the environment. Proponents who can demonstrate a similarly high commitment to these standards shall be ranked highly under this criterion.

Figure 3. The Boskalis/Cofra rig installing wick drains in the Terminal 11 Trial area. Rig is an 80t machine with 45 metre mast. The dredge pipe is in the foreground. A Car Carrier vessel departing the Brisbane River is visible in the background.

Figure 4. Close up of the Boskalis/Cofra rig during installation of BeauDrain-S. Planning for the Future – Ground Improvement Trials at The Port of Brisbane 25

Figure 5. Van Oord is also a trialist in the Terminal 11 Area. Stitching Rig is being filled with new reel of wick drain. Note wick anchor plates used to mark location of each wick prior to installation.

Field trials progress The aerial photo (Figure 7) taken in June Given the expanded area of the trials and As at June 2007, Boskalis Australia had 2007 shows the Austress Menard site increased loading parameters, some 1.5 million completed installation of all wick drains and located in the S3A Trial area adjacent the cubic metres of surcharge is required to be the BeauDrain-S system (Figures 3 and 4). Port’s Bird Roost with the Moreton Bay placed following the contractors’ installation Van Oord had also completed all PVD Marine Park in the foreground, and the Port works. Installation of an extensive number installation works (Figure 5). After rather in the background. The black L is the and type of monitoring instruments extensive preparatory works, including vacuum trial area with (black) membrane, including , extensometers, deep constructing the 15 metre deep perimeter pipework and pumps installed. Behind this settlement plates, load cells and inclino- vacuum cutoff wall, Austress Menard is the white sand drainage layer placed over meters is now complete. Surface settlement completed wick drain installation to all trial the wick drain trial areas which extend up markers on a 25 m grid are also in place. areas in May. The vacuum consolidation to the future road alignment. Surcharge system installation including membrane, placement across both the wick drain and The common view of the trialists is that pipework and pumps was completed and vacuum trial areas is currently underway. meaningful interpretations of the measured the system commissioned in June 2007 The 15 m deep cutoff wall was installed performances of each trial area will be able (Figure 6). around the perimeter of the L. to be made 6 months after the surcharge is

Figure 6. The 80t excavator from Austress Menard excavating the cutoff wall with the PVD installation rig working in the background. 26 Terra et Aqua | Number 108 | September 2007

placed to full load. PBC plans to have the results reviewed by CG experts, including Prof Harry Poulos, and externally by an appropriate expert. PBC is currently sourcing a suitable data capture and presentation software system for use during the Trials.

Trialists have submitted samples of all PVD types being used in the Trials to enable relevant laboratory testing of the PVDs to be undertaken, including horizontal and vertical flow capacities in unkinked and kinked states. Kinking of PVDs is a possible outcome with certain PVD cores subjected to large settlements.

Anticipated outcomes PBC and CG expect to achieve the following outcomes from the trials: 1. Identify the effectiveness of PVDs for local site conditions, including thickness and depth of dredged mud and soft clays plus natural drainage conditions Figure 7. An aerial photo taken in June 2007 shows the Austress Menard site located in the S3A Trial area adjacent 2. Identify the performance of PVDs for the Port’s Bird Roost with the Moreton Bay Marine Park in the foreground, and the Port in the background. different spacings in relation to local conditions 3. Identify differences in PVD performance locally and overseas and subsequently PBC is aware and currently addressing the and cost implications engaging three world-class contractors to logistical issues in instrumenting numerous 4. Verify consolidation times, and required undertake an extensive suite of trials, large trial sites, data capture, processing surcharge loadings using PVDs and using PBC believes it will arrive at an optimum and presentation and the placement of vacuum consolidation solution or series of working solutions. 1.5 million cubic metres of surcharge in 5. Identify performance of Contractors in These solutions will be able to be utilized an obstacle intense area. relation to design and construction. to develop large tracks of reclaimed land suitable for Port industries and meet a The Trials have already generated significant As regards comparison of design and range of future time demands. interest from industry, both Client and construction capabilities of three world-class Contractor. contractors, as the size of the trials has Whilst undertaking trials over an area of expanded, the 6 months results are not 11.5 ha looks excessive, it needs to be expected to be available before the middle realized that this only equates to less than REFERENCES of 2008. 4% of the land areas to be developed (see Figure 1). It is considered that the Ameratunga, J., Shaw, P. and Boyle, P. (2003). additional costs associated in undertaking Challenging Geotechnical Conditions at the CONCLUSIONS the trials, such as extra field and laboratory Seawall Project in Brisbane, Coasts and Ports testing and intense performance monitoring, Conference (PIANC) 2003, Auckland, NZ. PBC identified that no single optimum solution will be recovered in the first couple of years existed to accelerate the consolidation of of optimized broad scale treatment rollout. Andrews, M., Boyle, P., Ameratunga, J. and soils and dredged sediment to develop land Further, it will provide for a significant Jordan, K. (2005) Sophisticated and Interactive within the future Port reclamation areas. degree of confidence in land availability Design Process Delivers Success for Brisbane’s Indeed several techniques are available and timelines going forward that can be taken Seawall Project, Coasts and Ports Conference all have their advantages and disadvantages with confidence to the market place. 2005, Adelaide, Australia. in relation to time, cost and performance. Implementing results of the Trials will allow By calling and receiving expressions of quality land parcelling for development that interest from specialist contractors both can be released in a staged, timely manner.