The following publications are works either authored by our staff or, in some cases, co-authored with people from outside the company.This selection of conference papers and journal articles can be accessed by requesting individual items from our Tonkin + Taylor Ltd Library (firstname.lastname@example.org) or by clicking on the button beside the item. There is no charge for this service. However, please note that our Library follows Library Association (LIANZA) guidelines (link to their guidelines here) and reserves the right not to supply any item if these conditions are not met.
A correlation for the shrink swell index
Site classification to AS2870-2011 requires the soil shrinkage index, Ips. A common assessment method is to carry out a shrink swell laboratory test to calculate the shrink swell index (Iss), which is then used to develop the soil shrinkage index. To undertake a shrink swell index test, an intact thin wall tube sample of cohesive material is required. In hotter and drier areas of Australia, including northern Victoria, it can be difficult to recover intact cohesive samples. The geotechnical practitioner is often required to consider other methods to estimate Iss in order to provide the required site classification. This paper considers a variety of laboratory tests results including Atterberg Limit, Particle Size Distribution, Hydrometer and Iss results from clay samples within Victoria (including Melbourne) to provide an improved correlation to estimate Iss when thin wall tube sampling is not practicable. The data presented to support the correlation includes published test results by others and unpublished test results from projects the author has been involved in.
Geology and geotechnical characteristics of the Geelong CBD
This paper supplements the published geology of the Geelong CBD with previously unpublished
geotechnical borehole records. The additional data is used to adjust the published geological
boundaries and provide information on the geotechnical properties of the encountered units.
NES permitted activity for subdivision and land use change - what does "Highly unlikely" actually mean and how do you assess it? (2)
The Resource Management (National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health) Regulations, 2011 (the NES) is a national standard that applies throughout New Zealand to address human health effects from contaminated land. The regulations within the NES are relatively prescriptive, except for permitted activity Regulation 8(4). This regulation requires a Suitably Qualified and Experienced Practitioner (SQEP) to make a judgement on whether it is Highly Unlikely that there is a contamination risk to human health from an activity.
There is little guidance on how a SQEP should make an assessment of Highly Unlikely under Regulation 8(4). The purpose of this paper is to generate discussion of what Highly Unlikely means when assessing if the Regulation 8(4) conditions can be met for a particular activity on a site.
Smart solutions : potable water
Sparkling? Still? Or boiled? The government inquiry into the contamination of the Havelock North water supply could carry significant implications for how council-controlled water supplies are managed in the future. Patricia Moore asks water specialists what smart solutions could look like in 2018 and beyond.
The 2016 Meinong Taiwan Earthquake: learning from earthquakes report
The Mw 6.4 Meinong earthquake occurred on 6 February 2016 in the southern region of Taiwan. The
earthquake caused significant damage in and around Tainan city, with a number of collapsed and severely
damaged buildings and 117 deaths. A five-member Learning from Earthquakes (LFE) team visited Taiwan
approximately one month after the earthquake, with particular focus on learning from changes to design
practice and seismic mitigation efforts following the 1999 Chi-Chi earthquake in Taiwan. Land damage was
generally modest with liquefaction and slope-failures observed in a limited number of locations. Some
notable instances of liquefaction-related foundation settlement and tilting occurred in areas associated with
historical filling. Following the earthquake, the Taiwanese government publically released liquefaction
hazard maps that will have a significant impact on public awareness and land values. The observed structural
damage was characteristic of non-ductile and poorly configured buildings. The collapsed buildings all
contained irregularities and soft-storeys. The majority of older mixed-use buildings performed adequately,
but severe column failures were observed in several taller apartment buildings constructed in the 1990s. The
performance of schools and district offices provided valuable insight into the successful implementation of
seismic assessment and strengthening programmes. A comparison of existing and strengthened buildings
showed that efficient retrofit solutions can reduce the risk posed by critical structural weaknesses and improve
the safety and resilience of these buildings. A similar strategy could be implemented for common critical structural weaknesses in New Zealand buildings.
A review of shoreline response models to changes in sea-level
Assessment of current and future coastal hazards is now a legislative requirement in New Zealand
and most parts of Australia. Methods for assessment of erosion hazard are well established, and uncertainty
in the present hazard can be reasonably well estimated. However, uncertainty in defining future
climate-change associated erosion/recession hazard increases due to both the assumptions
surrounding sea-level rise (SLR) as well as limitations of the models used to evaluate the
associated shoreline response. The most widely used methods for defining the coastal erosion hazard
extent utilise a modular approach whereby various independent components are quantified and summed
to provide a final value (e.g. see ). The SLR response component is based on the well-accepted
concept that an elevation in sea level will result in recession of the coastline. This component is
often the largest contributor to erosion hazard zones, so understandably this term is often the
subject of intense debate, media scrutiny and a focus in litigation. With the trends of increasing
populations on the coast this controversy is only likely to escalate. A range of models for
estimating coastal response to changes in sea level have been developed over the past 50 years.
These methods range from the application of basic geometric principles to more complex
process-based assessment. While some methods are used more widely than others, none have been
proven to be categorically correct or adopted universally. While most attention has focussed on the
response of open coast beaches to SLR, other shoreline types including gravel beaches and low
energy coastlines such as lagoons and estuaries are also affected. This paper briefly reviews
existing shoreline response models including the process assumptions, limitations, development and
application history. While most models are based on similar underlying process assumptions,
variation in the definition of model parameters (e.g. closure depth) can produce significant
differences in predicted recession values. As such, robust and informed selection of model
parameters are required to derive defensible conclusions.
Centrifuge modelling of the seismic response of multi-storey buildings on raft foundations to the Christchurch Earthquake
There were a number of multi-storey buildings on shallow raft foundations in the central business district (CBD) of Christchurch that performed well in the 22 February 2011 Christchurch Earthquake. Structural assessments following the earthquake have concluded that some buildings performed significantly better than would have been expected given the intensity of the recorded ground motions in and around the central city. Nonlinear soil-foundation-structure interaction (SFSI) provides a possible explanation for the good performance of these buildings. Centrifuge experiments were undertaken at the University of Dundee, U.K., to examine the influence of SFSI in the seismic response of multi-storey buildings on raft foundations using a range of equivalent single degree of freedom (SDOF) building models resting on a layer of dense, dry sand. The models were subjected to representative records from the Christchurch Earthquake and it was found that significant energy was dissipated between the soil, foundation and structure. The large raft in conjunction with dense sand meant significant energy could be dissipated through SFSI without the detrimental effects of significant permanent soil deformation.
Engineering geology model of the Crater Lake outlet, Mt. Ruapehu, New Zealand, to inform rim breakout hazard
Havelock North water supply Campylobacter outbreak - source and ingress
In August 2016, the Havelock North public water supply suffered a significant
contamination event (Campylobacter), resulting in an outbreak of gastroenteritis in the
Havelock North community. Groundwater bores within the Brookvale Road bore field were
suspected by Hastings District Council (HDC) to be the source(s) of contamination of the
drinking water supply. Following the outbreak, HDC, Hawkes Bay Regional Council (HBRC),
the Ministry of Health and their supporting agencies launched full scale investigations to
understand what caused the contamination of the bore(s). Bores 1 and 2 were immediately
decommissioned following the outbreak, Bore 3 had already been shut down following an
earlier E. coli transgression. A Government Inquiry into Havelock North Drinking-Water
was subsequently convened to investigate the outbreak and its cause.
T+T was engaged by HDC to undertake investigations to evaluate the potential sources of
the Campylobacter contamination within the Brookvale bore field catchment, and, if
possible, determine the source of the Campylobacter that caused the outbreak and the
means by which the contamination entered the water supply bores.
Results of the T+T investigations are detailed in this paper. The scope of the investigations
was modified as new information came to hand, and an understanding was developed
regarding the source of the contamination, and the mechanism by which contamination of
the water supply occurred. Genotyping of the Campylobacter undertaken by ESR
determined an ovine (sheep) source and its location, and groundwater modelling and dye
tracer tests confirmed the contamination pathway was from a ponded area within the
nearby Mangateretere Stream via groundwater to the Bore 1 screens. Bore head and
defective casing ingress scenarios were largely discounted by the further investigations.
Very stringent technical standards were required by the Government Inquiry into the
Havelock North outbreak. The paper emphasises the very high level of technical
collaboration between HDC management, its consultants and legal advisors in order to
meet these requirements.
Geotechnical Monitoring and Management of TBM (EPB) Tunnelling Induced Settlement: The case of Waterview Connection Project Tunnel
This paper presents measurements of tunnelling induced settlements collected during the
construction of the Waterview Connection project. The NZ Transport Agency’s Waterview Connection
project involves the construction of 5 km of motorway to complete Auckland’s Western Ring Route.
Half of this new link includes twin 14.5 m diameter mainline tunnels constructed by Earth Pressure
Balance (EPB) Tunnel Boring Machine with 16 sequentially excavated cross-passages. Over most of
the tunnelled length the excavation is through extremely weak to weak interbedded sandstones and
siltstones of the East Coast Bays Formation (ECBF) overlain by weathered ECBF and alluvium.
However, tunnelling was also undertaken through stronger, volcanoclastic sandstone, and, through
alluvial soils at low cover. In the following paper the instrumentation methodology, monitoring regime
and analysed results are presented. The attention is given mainly to the monitoring data recorded
under free field conditions during and after the construction of the mainline tunnels. Settlement
readings are back-analysed using the classical Gaussian empirical predictions, in traverse arrays, and
at particular sections in longitudinal direction, providing a detailed description of the EPB tunnelling
performance under varied geotechnical conditions. The use of TBM calibration zones in selected
green field sites and how that data helped optimize TBM performance in relation to ground effects, is
discussed. Finally the influence of different parameters, such as tunnel depth, overlying geological
layers and tunnel face pressure, to the induced settlement, estimated ground loss and the shape of
settlement trough is investigated.
Fissure grouting and rock defect characterisation for the Waterview cross passage tunnels
The NZ Transport Agency’s Waterview Connection project in Auckland, New Zealand
involved the construction of a new 5km long, three lane motorway with twin, 2.4km long, three lane
tunnels up to 35m deep beneath urban Auckland. Pre-excavation fissure grouting was undertaken to
limit the inflow of groundwater into a number of the cross passage tunnel excavations. Investigation
and characterisation of rock mass defects at each cross passage ensured that fissure grouting was
only undertaken at cross passages to be excavated through highly permeable rock. This paper
outlines the geology of the tunnel alignment, the investigations carried out to characterise the rock
mass defects and the process followed to identify ‘at risk’ cross passages to be grouted. The grout mix
design and the grouting methodology are also discussed. Results and observations from the preexcavation
fissure grouting operation are presented and conclusions drawn as to the suitability of this
technique for the local ground conditions.
Liquefaction hazard mapping - liquefaction vulnerability mapping for a given return period versus return period mapping for a given severity of liquefaction vulnerability
Liquefaction hazard maps are typically developed by collating geotechnical investigation data and undertaking simplified liquefaction analyses. Liquefaction vulnerability parameters are commonly calculated using a simplified liquefaction triggering method, a given groundwater level and a given set of earthquake ground motions, corresponding to a particular return period of earthquake shaking. The results at each investigation location are then typically interpolated and subsequently, smoothing might be applied. A more robust methodology involves dividing a study area into smaller Similar Expected Ground Performance (SEGP) areas as a result of earthquake shaking. Liquefaction consequence parameter values for a wide range of earthquake scenarios are then calculated using the available geotechnical investigation data and grouped according to SEGP areas in which they are located. Each SEGP area then has its own unique liquefaction vulnerability distribution fitted to the data as a function of earthquake magnitude (Mw) and Peak Ground Acceleration (PGA). Using these functions, a variety of liquefaction hazard maps can be produced. A typical mapping approach is to present the median or mean liquefaction vulnerability for each SEGP area for a given level of earthquake shaking. A variant to this approach is to present the expected spatial variability of liquefaction. This approach provides greater insight into how a study area is expected to behave spatially, which is especially relevant for risk modelling. An alternative mapping approach is to determine the level of earthquake shaking required to attain a given level of liquefaction vulnerability. This approach identifies SEGP areas where more frequent, smaller levels of earthquake shaking are likely to result in liquefaction damage and other SEGP areas where less frequent, larger levels of earthquake shaking are required for liquefaction-related damage to occur. This alternative approach helps improve the communication of the liquefaction hazard to non-technical audiences and presents the results in a similar way to other natural hazards that are assessed for land-use planning and hazard management purposes.
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