Geotechnical Monitoring on a Ship: The Stability of Cargo in a Hold

Paul Burton, Chris Ransley

Geotechnics, New Zealand

Abstract:

The Taharoa Ironsand Mine is approximately 200km south of Auckland on the West coast

of New Zealand. The mine produces up to 1 million tonnes of ironsand concentrate per

year through its dredging and concentration plant. The titanomagnetite content sand is

primarily exported to Asian markets for steel production and refractory lining protection.

The MV Taharoa Express, a 269m 145,000 DWT bulk iron sands carrier, had been

experiencing some difficulties with its loading procedure. The sand is pumped 2.7km from

the shore through a slurry line, to a CALM single buoy mooring. The sand producer was

required to investigate the loading issues to understand potential hazards and to ensure

the ongoing uninterrupted supply chain.

Geotechnics was contracted to design, supply and install the geotechnical and structural

monitoring instrumentation within a tight schedule to meet our clients’ needs. All of the

installations were to be carried out off-shore with minimal or no disruption to the loading

programme. The installation required all instruments to be transportable by helicopter and

installed within a 16 hour period after the ship attached to the loading buoy. We

instrumented one hold of the nine, whilst loading continued. Our instruments included VW

piezometers, VW pressure cells, Leveloggers, tilt sensors and 3D motion sensors. All

sensors used automatic data acquisition systems; however old fashioned methods

including “ullaging” were applied when required. The instruments provided monitoring

throughout the slurry loading sequence and the subsequent voyage.

Further laboratory testing was carried out to ascertain the geotechnical characteristics:

being the density, settling and compaction characteristics of the iron sand.

The instrumentation and laboratory results provided valuable input to modelling programs,

creating a loading criteria model for the client’s use.

1. Introduction

Our client, New Zealand Steel, has developed the Tahaora Ironsand mine over the last 40

years on the East coast of the North Island of New Zealand. The facility mines and

concentrates black ironsand into a high-grade titanomagnetite product. This product is sold

to steel producers in Japan and China for high grade steel production and refractory lining

protection. NZ Steel has developed a loading system which includes the use of a slurry

line to an offshore buoy for loading onto the MV Taharoa Express, a 269m 145,000 DWT

bulk iron sands carrier (Fig. 1). The slurry line follows the sea bed for 2.7km from the shore

based concentration plant. The line then rises to a floating catenary anchor leg mooring

(CALM) buoy. Onboard slurry pumps direct the sand to the holds. The loading process

requires strict adherence to the order of hold filling and the direction of the loading nozzles

in the holds. The holds are then de-watered using filter banks in the base of the hold walls.

Once the sand reaches the prerequisite water content, the ship may weigh anchor and

travel to its destination.  

Figure 1 : MV Taharoa Express moored off the coast on New Zealand showing location of Hold #3.

The instrumentation project was focussed on the behaviours exhibited by the sand in the

holds, during the loading process and, to a lesser extent, the subsequent voyage. The

client’s concern was that the cargo could become unstable through the process of wave

and swell changes acting on the ship. This could cause the saturated sand to liquefy, shift

and lead in turn to ship instability. Our scope was to understand the loading process,

monitor its progress and record the relationships between external changes in the ship’s

dynamics and its cargo’s stability.

The project covered three of the voyages of the MV Taharoa Express between February

and May 2010. The first two of these involved significant instrumentation installation and

monitoring. The final voyage, not discussed in this paper, involved minor monitoring and

removal of our previous installations.

This paper will focus on the challenges surrounding the planning, procurement, logistics,

installation and monitoring of our geotechnical and structural instrumentation. We also

carried out some field investigative testing and laboratory testing of the sand to provide

further understanding for modelling.

Due to client confidentiality we are unable to provide or discuss any of the technical

findings or details of the analysis.

Our client has developed a successful business through their supply chain and they were

keen to ensure that they understood all the foreseeable risks of the loading process. The

results would be used to create a loading model for future voyages. Further to this, the

instrumentation results and experiences are being used to help develop an automated

loading process for a new vessel expected to commence service in the next 2 years.

All instruments used for this project are currently in use around the world for a variety of

project types. We believe that this project is unique in its use of geotechnical and structural

instrumentation to develop stability and loading models for a bulk carrier vessel.

2. Monitoring of Voyage 83 (V83) – 4 February 2010

Approximately 2 weeks of preparation time preceded the initial visit to the ship. The

following instruments were required to be installed in a 12 hour window between mooring

and the hold being loaded. All instruments were installed in Hold #3 commencing on 4

February 2010 in calm seas.

3 x Solinst Leveloggers

3 x Slope Indicator Vibrating Wire piezometers

2 x Penny+Giles STT tilt sensors

Further to this the following monitoring was carried out to provide data for future analysis.

Vibration Monitoring

Ullaging – measuring the depth to sand from access holes

Ship Orientation – plotted data from the bridge

Wave/Swell direction – visual and mooring buoy data

Visual Inspections – post de-watering surveys

Survey for future installations

2.1. Challenges of Voyage 83

2.1.1. Minimal Site Knowledge

Detailed information and plans for the layout of the ship were minimal as the vessel was

not owned or operated by our client. We were sent low resolution digital photos by satellite

phone and received some general drawings, but little detail (Fig. 2). As the ship was on a

continuous journey between New Zealand and China a pre-installation inspection was not

possible; our planning had to be flexible enough to allow for the lack of specific

dimensional information.

We also had minimal knowledge of the specification and quality of power supply aboard so

an external power supply was secured for our use. 

Figure 2: Sketch drawing showing typical ship’s hold dimensions. 

2.1.2. Lead Time and Limited Procurement

The decision to instrument and analyse the loading procedure was driven by our client’s

desire to ensure that the process was safe and their supply chain was secure. The ship’s

program, and project approval by management, meant our lead time was less than 3

weeks to evaluate, design, procure, prepare and deploy. Due to New Zealand’s remote

location in the South Pacific, the requirement to stock specialised monitoring equipment in

the country is minimal. For this reason our initial installation used equipment that we knew

we could source within a 2 week time period.

2.1.3. Durability of Equipment

The criteria for instrument selection was primarily based on hardware durability. The

loading process has the slurry pumped from a pipe at the roof of the hold, falling 22m to

the floor. The aggressive scouring nature of the iron ore slurry required the instruments to

be protected and fixed firmly to the hold. We were not allowed to perform any welding; all

of the fixing was carried out using mechanical methods. The fixings and protection also

could not interfere with the methods deployed and equipment used for the cargo removal.

The iron ore unloading process in China uses drop buckets and excavators that are

lowered into the hold. We were informed that we should not expect any instrumentation

installed into the hold to survive the unloading. Further to this, we were required to provide

details of the equipment to the company’s insurer, as the ship’s load would now also

include pipe work and instrumentation which could possibly damage the materials handling

equipment at the receiving port.

The data loggers were safely removed by the crew prior to docking in China and the

Leveloggers downloaded by crew at the same time to ensure security of voyage data.

2.1.4. Installation Time

On arrival of the ship at the loading buoy, we were expected to install the instrumentation

in a 12 hour period before the iron ore was due to be pumped to the designated hold. We

pre-prepared the instrumentation as much as possible prior to the visit and allocated the

various tasks and roles to ensure installation proceeded smoothly. The project plan

included contingency scenarios, as our installation site knowledge at this stage was

limited. Flexible fixings and conduit were chosen to suit the unknown physical environment

of the installation and staff were prepared for a very long shift.

The initial 12 hour install window was extended by 4 hours due to a pump failure.

Installation was completed in 15.5 hours, with a further 30 minutes used to check

instruments and practise downloads. We welcomed the extra time as it allowed us to

confidently complete and check our installation.

2.1.5. Transportation and Accessibility

All equipment to be installed or used in the installation procedure had to be transported

3km to the ship from shore by helicopter. We were able to get measurements of the

helicopter capacity prior to our arrival, to ensure the dimensions of our equipment could be

managed. We selected equipment and consumables that met all of our other criteria but

could also be broken down and reconstructed with ease due to the freight capacity limits.

As the ship was not considered to be docked in New Zealand, we were also subject to

Ministry of Agriculture and Fisheries, and Customs checks.

We were aware of the restrictive nature of the access to the hold prior to our visit; however

the exact layout of hatches and ladders was unknown. On first arrival at the ship we had

one staff member carry out reconnaissance and take measurements, to ensure our

installation methodology would be effective. Whilst this was in progress, the other staff

transferred the equipment and tools to the hold floor using ropes through the hold roof.

Access to the hold floor, 22m below the deck, was initially down a vertical access ladder

and then to a spiral staircase on the hold wall (Fig. 3). The remaining descent was via

three ladders fixed to the hold wall varying from 45⁰ to vertical. We used bags and buckets

with ropes to lower and raise the equipment which reduced the number of trips required.

Lighting for our work came from the ship’s portable lights along with personal head torches

and floodlights powered by a generator taken to the ship for this purpose.

Figure 3: Hold #3 access hatch and ladder.

2.1.6. Data Management and Complexity

The data captured from the Voyage 83 installation ranged in complexity from simple

handwritten notes through to pore pressure readings datalogged at 0.5 second intervals

for an 11 hour period. Over the whole monitoring period, which included 4 days on the

buoy and subsequent voyage, the Leveloggers alone produced close to 1 million data

points. The additional 10 second readings from the VW piezometers and 1 second

readings from the tilt sensors combined to create a wealth of data for our modelling work.

The visual inspection and manual measurements taken in the hold, although less complex,

provided us with not only data, but a good reason to observe and understand the loading

process as it progressed (Fig.4).

 

Figure 4: Observing the dewatering process in Hold #3. Sand beach forming below the loading nozzle.

2.1.7. Cost

Our client required budgetary advice prior to any purchase and installation, which in the

short lead time, was challenging in itself with so many unknowns. It was important to them

to get an initial understanding on Voyage 83 and progress the scope for the following

voyage. Significant cost implications were discussed and approved as we progressed, and

low cost solutions were encouraged. However the cheaper solutions were not always

viable given the criteria and limitations of the project.

2.2. Instrumentation and Installation Details of Voyage 83

2.2.1. Pore Pressure Measurements

We chose to install both Solinst Leveloggers and Slope Indicator VW piezometers to allow

for any instrument failure and to compare performance. For protection from scouring, the

instrument tips were installed in steel mesh filters. Pairs of instruments were attached at

2m, 6m and 9m heights above the hold floor using a galvanised pipe conduit framework

(Fig. 5). This structure was carefully raised into position on the ladder and spiral staircase,

using ropes.

 

Figure 5: Pairs of instruments attached at 2m, 6m and 9m heights above the hold floor.

Cabling above the final sand level was directed to our monitoring station just below the

deck. The VW piezometers were monitored using a Campbell Scientific AVW200 interface

module, 16 channel multiplexer and CR1000 data logger (Fig. 6). The Leveloggers were

downloaded using both a Leveloader data transfer unit and direct read to a laptop. Power

for the logger was provided by dry cell batteries which also provided backup for the laptop.

 

Figure 6: Left: Pore pressure Instruments installed in steel mesh filters for protection. Right: Instruments wired to a Campbell Scientific CR1000 logger at the monitoring station.

For the initial loading monitoring period of 11 hours the VW piezometers and Leveloggers

were set to record measurements at 10 second and 0.5 second intervals respectively. The

Leveloggers were reduced to monitoring at 2 second intervals for the de-watering process.

The instruments were adjusted again, prior to our departure from the ship, to record during

the voyage.

The VW piezometers were set to 2 minutes to record the 29 day voyage and the

Leveloggers to 10 seconds for the first 4 days.

2.2.2. Tilt Sensors

Owing to the short lead time, we could source only low resolution tilt sensors for the initial

voyage. We installed two Penny+Giles STT280 tilt sensors with a resolution of ±0.07Deg.

These were linked to a Campbell Scientific CR1000 datalogger and provided us with bi-

axial tilt readings. The tilt sensors were installed in the monitoring station area and

mounted on a bulkhead wall just below the deck, using a fast set epoxy. The power was

supplied by a dry cell battery.

2.2.3. Vibration Monitoring

To measure the accelerations imparted on the vessel through wave action 2 Nomis

seismographs were set up in an adjacent empty hold, #4. The units were set up oriented to

starboard, the direction of expected swell, and were set on bar graph mode.

2.2.4. Ullaging

During the loading cycle the ship’s crew took hourly measurements of the sand depth at 8

locations in each hold. This process involved lowering a weighted metal plate on a

graduated steel cable through an inspection hatch to measure the surface of the sand in

the hold. The results could then be used to direct the loading nozzle to balance the load

and ensure stability of the vessel.

Management of the loading procedure was handled by the Ship’s Officers and the Captain

from the bridge, using radios to communicate with the crew on the deck. The sheer size of

the ship and the high density of the cargo required a very complex loading schedule to

ensure the integrity of the ship’s structure and balance.

2.2.5. Ship Orientation

The heading of the ship was a function of the wave, wind and swell action on the ship’s

hull and superstructure. We were able to obtain orientation data from the bridge from a

simple plotter which allowed us to determine when any significant change occurred.

2.2.6. Wave and Swell Direction

The mooring buoy used by the ship for loading held monitoring equipment for measuring

wave and swell direction, primarily used for determining the suitability of conditions for

loading. This provided us with a log of data covering the loading process.

2.2.7. Visual Inspections

After loading was completed and de-watering had significantly progressed, visual

inspection in Hold #3 was carried out. This provided us with further understanding of the

sand deposition process in the hold. Simple profile measurements, photographs and

drawings were made to compare with monitoring data.

2.2.8. Survey for Future Installations

Voyage 83 provided us with a good understanding of the challenges associated with

installing monitoring instrumentation on an ocean-going vessel. We spent time taking

measurements, checking specifications, taking photographs and instigating and building

relationships with key personnel on the ship.

2.3. Results

All of the instrumentation had performed as anticipated. However as the records were

collected in calm conditions, the resulting information was not representative of loading

concerns. Rough conditions would put significantly more pressure on the loading process,

as sand slurry moved around the hold prior to de-watering. The results obtained clearly

showed the changes in pore pressures within the hold as loading progressed.

2.4. Conclusions

Our client and their consulting engineers decided further instrumentation monitoring should

be carried out for another loading cycle. All of the instrumentation had worked well, and it

was decided that additional instrumentation to measure the sand pressure on the hold

floor and the 3-dimensional orientation of the ship also be considered. When we received

details of equipment damaged during the unloading process, a review of instrumentation

requirements was carried out.

3. Monitoring of Voyage 84 (V84) – 27th March 2010

The review of the instrumentation requirements and subsequent project approval left us

with three weeks of preparation time for monitoring of Voyage 84. The following

instruments were prepared to be installed in an expected 16-hour window between the

ship mooring and the hold being loaded. However we were notified the day before

mobilizing that a marine inspection was to be carried out prior to the vessel mooring. This

provided an extra 8 hours to a total of 24 hours installation time.

The following instruments were installed in Hold #3 commencing on 27th March 2010 in

average sea conditions.

3 x Solinst Leveloggers ( 2 intact from V83)

2 x Slope Indicator Vibrating Wire piezometers ( 2 intact from V83)

2 x Penny+Giles STT tilt sensors (reinstated)

5 x Geokon Fatback pressure cells with 4 associated VW piezometers

1 x Xsens Mti - Attitude and Heading Reference System (AHRS)

Further to this instrumentation the following monitoring was carried out to provide data for

future analysis.

Vibration Monitoring

Ullaging – measuring the depth to sand from access holes

Wave/Swell direction – visual and mooring buoy data

Visual Inspections and Testing – post de-watering surveys

3.1. Challenges of Voyage 84

3.1.1. Lead Time and Limited Procurement

Although we were aware of potential developments in our scope of instrumentation for

V84, we were unable to confirm any details thereof, until post-processing had been

completed, analysed and the client had approved the next phase.

Apart from reinstating a new Levelogger at the lowest level due to unloading damage, we

also installed Xsens AHRS and Fatback pressure cells with associated VW piezometers

on V84. All of the previous instrumentation was used or reinstalled. The Xsens unit was

easily sourced and couriered within a week and our IT group created logging and backup

software for use with a laptop PC. This system was easily installed and managed.

A bigger procurement challenge was obtaining 5 Fatback pressure cells for the required

pressure range. The only supplier we could find to source all 5 cells in time was Geokon.

However they had only 3 true Fatback cells ready for export and 2 normal cells for the

pressure range we desired. We only had 3 weeks to have everything ready so we decided

to convert the normal cells to Fatback using a thick steel plate. The attached cables were

extended with resin splice kits and trials with the data loggers completed.

3.1.2. Durability of Equipment

Our experience on V83 provided us with a good understanding of the attrition that would

occur whilst loading. The unloading procedure had damaged the lower pore pressure

piezometer and mounting arm. With the measurements from our survey, we were able to

prefabricate a new Levelogger arm assembly and use flexible hose to conduit the cable.

Our biggest challenge was the installation of Fatback pressure cells and piezometers on

the floor of the hold. Our client required 5 cells to be fixed to the floor and a VW

piezometer to be located close to 4 of them. This would provide the total and effective

stress in each quadrant of the hold (Fig. 7).

Fixing the cells and piezometers to the floor without welding, and meeting the criteria for

the unloading, required some innovative alternatives to metal conduit. The floor was highly

corroded and also covered with a caked layer of iron ore sand. We trialled some different

methods of fixing conduit at our laboratory and decided on PVC conduit and modified

saddles glued to the floor with acrylic adhesive. To fix the instruments and the PVC

saddles to the floor we had to first clean small areas with a broom, then a wire brush on a

large angle grinder, and finally clean with acetone before gluing the units to the floor.

 

Figure 7: Layout of VW pressure cells and VW piezometers on floor of Hold #3.

This process was highly time-consuming, hot, dusty, and dark. The wire brush would

create small dust clouds so masks were necessary; this became uncomfortable over time

with the very humid and warm hold temperatures. To assist with bonding, large sample

bags were filled with the heavy iron ore sand to weigh down the units.

We were relieved to watch the loading process start and observe the expected instrument

readings. This indicated that none had dislodged during the initial critical phase of loading.

The unloading process removed all of the instruments installed on the floor of the hold.

We had 2 damaged pressure cells returned to us out of the total of 9 instruments. No

damage was reported from the material handling facility in China.

3.1.3. Installation Time

We initially expected to have a 16-hour installation window after boarding the vessel. The

design and choice of instruments and installation methods were based on this timeframe.

Subsequently we were informed that this would be extended as a maritime inspection prior

to mooring at the buoy would be carried out. We were allowed to be flown out to the ship

which would initially anchor 5kms from shore. This improved our level of confidence in

being able to complete our tasks in good time, and secure all the instrumentation to

survive the loading process intact.

On completion we found that the delay had given us more time to fasten the conduit from

the pressure cells with extra saddles, and allow us to more adequately route our flexible

hose to minimise damage.

3.1.4. Transportation and Accessibility

The purchase of an engine hoist, pulley and ropes allowed much easier movement of our

equipment to and from the hold floor. We had significantly larger quantities of equipment

on V84 including conduit (both PVC and fuel hose), floodlights, instruments and powered

equipment. The use of cages and nets under the helicopter proved an effective way to

transport the equipment with minimal delay for the helicopter. It also allowed the

equipment to be lowered beside Hold #3 directly rather than carried from the helipad

(Fig.8).

 

Figure 8: Airlifting equipment to the MV Taharoa Express using cargo cages to reduced handling.

3.1.5. Data Management and Complexity

Data capture frequencies were very similar to the V83. However the quantity of

instruments had increased. We also had the Xsens Mti AHRS unit logging at the minimum

setting, 10Hz, collecting large quantities of data to a laptop and backup hard drive.

All data was regularly downloaded from the CR1000 systems and backed up to separate

drives for data security. Data manipulation and plotting was carried out with Grapher 7

software due to the size of the data set.

3.1.6. Cost

Our client was keen to capitalise on the results obtained from V83, and improve their

understanding of the ship’s dynamics during loading by expanding the instrumentation

scope for V84. Although the quantity of instruments had doubled, we were able to save

money by using some of the existing instruments from the previous voyage, and through a

reduction in contingency allowance. Due to the increased amount of instrumentation and

monitoring required, extra manpower was needed. However, our client was keen to reduce

costs by providing the additional staff, who worked in collaboration with ourselves. The

collaborative nature of the relationship with our client meant savings and efficiencies were

identified and implemented according to their requirements. This approach ensured that

the staff and equipment requirements were met at a mutually agreed cost.

3.2. Instrumentation and Installation Details of Voyage 84

3.2.1. Pore Pressure Measurements

The original V83 piezometer setup was generally intact after the round trip to China

despite the potentially problematic unloading procedure. We were required to retrofit a new

Levelogger at the base of the pipe work to replace the lost instrument. This was carried out

using a prefabricated arm with a fixing mount. Better understanding of the loading process

had taught us that a small flexible hose would be sufficient to protect wiring from attrition

and enable a quick installation of the replacement instrument.

Ease of installation and performance on V83, and ability to log at a higher frequency gave

us the confidence to use the Levelogger system alone, to measure pore pressure in the

multi-level system for V84.

3.2.2. Tilt Sensors

The tilt sensors used for V83 were reinstated and used as a redundancy and contingency

measure for measuring the pitch and roll of the ship. If the Xsens Mti AHRS proved

successful then we would use this data for correlating.

3.2.3. Hold Floor Pressure Cells and VW Piezometers

Modelling of the cargo’s stability required an understanding of the movement of the bulk

cargo in the hold during the loading process. We chose Fatback VW pressure cells to

monitor the total stress in the centre and in each quadrant of the hold. The pressure cells

were all fixed to the hold floor using a fast set, acrylic adhesive 3M DP-810 (Fig. 9).

Wiring was ducted through PVC pipe attached to the floor with modified PVC saddles. The

cabling rose from the floor inside a heavy duty fuel hose, attached to the centre column of

the spiral staircase with stainless steel strapping (Fig.10, 11). Locating 4 VW piezometers

in close proximity to the pressure cells would also provide effective stress measurements

at each monitoring point.

 

Figure 9: Gluing VW Pressure Cells and VW Piezometers to floor using fast set acrylic adhesive.

 

Figure 10: Fuel hose, carrying cables to the monitoring station,

and replacement Levelogger arm.

Figure 11: Attaching PVC cable ducting to floor of Hold #3. Sandbags used to hold down saddles whilst adhesive cures.

All of these instruments were connected through to a CR1000 logger system and set at an

initial 30 second reading frequency during loading. The frequency was changed to 2

minutes for the voyage.

3.2.4. Xsens Mti AHRS

The Xsens instrumentation was used to provide pitch and roll data for V84 loading that

was previously provided on V83 by the tilt sensors. We could also record the ship’s yaw

(heading). This data combined with the pitch and roll readings allowed us to integrate the

results to calculate accelerations.

The Xsens unit was fixed to a mounting plate and glued to the hull close to the tilt sensor

location, with G-clamps employed whilst the adhesive cured (Fig.12).

Our laptop with backup hard drive was located close by and used a 40Ah battery and an

inverter for power supply.

The Xsens unit read at 10Hz to minimise data overload and continued to run until the ship

left the mooring buoy and our staff left the ship. The unit replaced the need for

seismographs and tilt sensors, and also accurately recorded the ship’s heading.

 

Figure 12: Xsens unit monitoring the ship’s pitch, roll and yaw. Laptop with backup hard drive collecting data.

3.2.5. Wave and Swell Direction

Wave and swell direction was again monitored by the mooring buoy equipment; this was

backed up with regular visual checks, especially when rogue waves caused the ship to

shudder. The significant resonance in the holds was sufficient to alert us to these events.

3.2.6. Visual Inspections and Testing

In a similar method to the V83 inspections, further topographical surveys were undertaken,

this time using a rangefinder and clinometers. This provided a much more accurate record

of the sand settlement after de-watering (Fig. 13).

 

Figure 13: Taking a topographical survey of the sand surface during de-watering.

Manual dynamic cone penetrometer (Scala) equipment was used in various locations to

measure the strength of the different sand layers deposited. Bulk samples were taken from

the hold for laboratory analysis to compare with pre-slurried material. The density results

were used together with nozzle direction, swell, and ship orientation data to model the

sedimentation process.

3.3. Results

The results from V84 were significantly more useful than V83. The integration of the

positioning and effective pressure data allowed the development of a model to understand

the loading procedure in more depth. This in turn enabled our client to confidently act on

their consulting engineers’ recommendations. The wave and swell, while not large,

provided realistic results that could be interpolated for rougher conditions. Our results also

indirectly highlighted some procedural improvements that would give improved confidence

to the loading process.

3.4. Conclusions

Installation for V84 was much improved thanks to experience derived from the installation

on V83. Our extensive survey provided us with excellent records when designing,

choosing and implementing the instrumentation for V84. The choice of instrumentation and

installation methods proved more than sufficient. However with more lead time, we would

have preferred to procure more specialized instruments, designed for the application.

The durability of our installation was proven adequate, both in strength of installation and

minimising damage to materials handling equipment. The installation process was made

easier due to loading delays, which allowed us extra time. It is difficult to determine, had

the delay not occurred, whether or not we would have had time to adequately secure all

the instrumentation to survive the loading process intact.

By V84 we had developed a more efficient transport and access system. This allowed us

to achieve more installations to a higher standard.

4. Project Summary and Conclusions

Although not likely to be a common request, geotechnical monitoring onboard the MV

Taharoa Express was a very informative experience because it forced us to think outside

the square. The detailed planning and the constraints placed upon us meant that we faced

continual challenges.

The value of basic and visual monitoring cannot be underestimated alongside the use of

new and common technology for any instrumentation project.

As with any project, familiarity with the site and client improves your ability to provide a

better service. However this should not be at the expense of anticipating the unforeseen

and planning to allow for flexibility and contingencies.

The nature of this project meant that we had to be well prepared, due to the location of the

site and our inability to adjust schedule once underway.

A unique problem required novel solutions. This experience has proved a useful lesson in

applying new thinking to everyday challenges, encouraging innovation and flexibility while

emphasising the importance of planning to successful outcomes.

Acknowledgements

Work carried out on this project would only have been possible with the collaborative

support of New Zealand Steel. We recognise their significant confidence in our abilities to

complete this project with all of the challenges that we have presented in this paper. Their

support throughout the process was essential and we were very fortunate to have the

close assistance in particular of Pat Rowe both in preparation and implementation. Our

sincere thanks go to New Zealand Steel and all of its employees involved with the Taharoa

operation. We would like to thank the officers and crew of the MV Taharoa Express for

their patience and assistance during the installation on their ship. The provision of

quarters, and food and drinks at all hours was greatly appreciated.

We also thank the staff of Geotechnics and Tonkin & Taylor Ltd for their extensive work on

this project, in particular Dr Sjoerd Van Ballegooy. His enthusiasm for the project and

contribution to our planning, along with physical and technical input through the installation

phase, ensured that we met the exacting and innovative requirements of this unique

challenge.

We gratefully recognise the efforts of Durham Geo Slope Indicator and Geokon for their

technical assistance, suggestions, support and extraordinary expediency with supply of

our required instruments.

Lastly the writers appreciate the valuable input of Amy MacKinnon throughout the review,

edit, design and production of this paper.

Authors

Paul Burton, DipHE pburton@geotechnics.co.nz

Chris Ransley, BSc (Hons), Env Sci. cransley@geotechnics.co.nz

Geotechnics

PO Box 9360, Newmarket

Auckland 1149, New Zealand www.geotechnics.co.nz