Gonzalez A.,University for Development |
Cubrinovski M.,University of Canterbury |
Alabaster D.,New Zealand Transport Agency |
Thenoux G.,University of Chile
Road Materials and Pavement Design | Year: 2012
A large research project on foamed bitumen (FB) stabilisation was conducted in New Zealand. The project consisted of an extensive laboratory and full-scale testing of FB pavements. The objective of this paper is to interpret the performance of FB pavements by using finite-element (FE) modelling. The mechanical properties of the materials were calculated using testing data and used as material inputs in the FE modelling. The Mohr-Coulomb and Drucker-Prager material models were adopted to calculate plastic deformation, which is related to pavement rutting. Results of the modelling indicate that increasing the FB content increases the tensile strength and modulus of the pavements, reducing the plastic deformations in the subgrade and the stabilised layer. In addition, adding FB reduces sensitivity to rutting when pavement is overloaded or the asphalt surface layer is cracked. © 2012 Taylor & Francis.
Van Blerk G.,New Zealand Transport Agency |
Fahey C.,Transfield Services
Airfield and Highway Pavement 2013: Sustainable and Efficient Pavements - Proceedings of the 2013 Airfield and Highway Pavement Conference | Year: 2013
Increased global financial constraints resulted in a continuing need to improve pavement performance at reduced input cost. This paper deals with a design and construction technique implemented by the New Zealand Transport Agency (NZTA) to deliver an increased «value for money» alternative to more costly options. The purpose of the construction technique is to optimize the inherent aggregate strength in crushed stone base layer properties by maximizing the stone packing, thus forcing a «full» stone-on-stone interlock obtained from a low fines and large crushed stone fraction aggregate grading. However, workability of the product becomes a challenge; this is improved by the addition of small amounts of cement (3%) during the mixing and compaction processes, thus forming a paste while in the hydraulic phase. The paper will look at various case studies were this technique has been used successfully as an alternative to structural asphalt and bitumen modified base layers for high traffic loading and high stress pavements. The methodology originated as a rehabilitation option implemented over the last four years for a performance specified maintenance contract (PSMC). In essence the system attempts to mechanise the Macadam construction methodology consisting of a high quality crushed stone skeleton. To achieve a stone interlocked layer through the use of modern stabilizer equipment cement is added to trap the limited fines within the grading. The case studies will show how the historical success of a stone interlocked pavement layer is captured in this design and construction technique, promising cost savings without compromising performance. © 2013 American Society of Civil Engineers.
McCarten P.S.,Opus International Consultants Ltd. |
Lloyd N.,New Zealand Transport Agency
Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management | Year: 2012
Barriers form the primary and most critical element for re-directing errant vehicles on bridges. Historically New Zealand bridges relied on concrete kerbs to provide the vehicle re-direction. The New Zealand Transport Agency has adopted NCHRP 350 to define collision performance and assesses the older bridge barriers are commonly only Test Level 2. Risk studies have shown that TL2 barrier performance is inadequate for current traffic volumes, vehicle weights and vehicle travel speeds on state highway bridges and hence barrier upgrades can often be justified. The risk studies have also shown new bridges require barrier collision performance at least equal to TL3. This paper introduces the New Zealand Transport Agency guideline document prepared to ensure consistency in evaluation of existing bridges and consistency in barrier retrofit design in order to optimise the structure asset management outcome. The paper also presents case studies for TL4 and higher collision performance bridge barrier retrofits. © 2012 Taylor & Francis Group.
Palermo A.,University of Canterbury |
Wotherspoon L.,University of Auckland |
Wood J.,University of Canterbury |
Chapman H.,New Zealand Transport Agency |
And 7 more authors.
Bulletin of the New Zealand Society for Earthquake Engineering | Year: 2011
On 22 February 2011 the M w6.2 Christchurch earthquake occurred with an epicentre less than 10 km from the Christchurch Central Business District (CBD) on an unknown buried fault at the edge of the city. The majority of damage was a result of lateral spreading along the Avon and Heathcote Rivers, with few bridges damaged due to ground shaking only. The most significant damage was to bridges along the Avon River, coinciding with the areas of the most severe liquefaction, with less severe liquefaction damage developing along the Heathcote River. Most affected were bridge approaches, abutments and piers, with a range of damage levels identified across the bridge stock. In the days following the earthquake, teams from various organizations performed inspections on over 800 bridges throughout the affected Canterbury region. This paper details the preliminary findings based on visual inspections and some preliminary analyses of highway and road bridges. The paper comprises information supplied by consulting engineering firms which were also directly involved in the inspections soon after the earthquake.
Gonzalez A.,Australian Road Research Board |
Cubrinovski M.,University of Canterbury |
Pidwerbesky B.,Fulton Hogan Ltd. |
Alabaster D.,New Zealand Transport Agency
Journal of Transportation Engineering | Year: 2010
The effects of foamed bitumen contents on the strength and deformational behavior of foamed bitumen mixes used for road pavements is very complex and not fully understood yet. While some writers report an increase in strength using one type of laboratory test, other writers report either only a small increase or even a decrease in strength using other types of tests, thus detracting foamed bitumen from being implemented as a cold-recycling technique for road pavement rehabilitation. This paper presents a laboratory study carried out on a specific granular material from New Zealand containing 1% cement and different foamed bitumen contents using indirect tensile strength (ITS), monotonic load triaxial (MLT), and repeat load triaxial (RLT) tests. The curing procedure, loading regime, and moisture contents were selected to simulate construction practice and suboptimal conditions normally found in New Zealand pavements. The results from these tests showed that an increase in foamed bitumen content up to an "optimum" content, increases the ITS but, at the same time, decreases both the permanent deformation resistance measured in RLT tests and the peak strength in MLT tests. In order to systematically examine the results from these tests, a general stress analysis was conducted, in which the stress paths applied in laboratory tests were plotted in I1-J2 1/2 stress diagrams. The stress analysis showed that adding foamed bitumen results in a reduction of the compressive strength of the mixes and a simultaneous increase in the tensile strength, which explains the apparently "contradictory" effects of foamed bitumen reported in the literature depending on the type of test used. © 2011 ASCE.