Characterization of road materials and environmental conditions for the analysis and design of flexible pavements in Hong Kong
Abstract of thesis entitled
Characterization of Road Materials and Environmental Conditions for the Analysis and Design of Flexible Pavements in Hong Kong.
Frederick Thomas Teague, M.B.E.
for the degree of Doctor of Philosophy at the University of Hong Kong September 1999
Analytical systems for flexible pavement analysis and design require a number of quality inputs for the production of economic cost-effective pavements. Key areas investigated under this research project included; the prediction ofthe volume of commercial vehicles using the highway network, the loading characteristics of commercial vehicles and the influence of their axles loads on; the stiffness of bituminous materials, the properties of road construction materials and the overall affect on pavement performance. Also investigated were environmental factors. Enviromnental factors were considered because of their major influence on the physical and mechanical properties of flexible pavement materials. These factors included; air and pavement temperature, solar radiation, cloud cover, hours of sunshine and rainfall. These factors governed the temperature of the pavement's bituminous layers which in turn influenced the pavements structural performance. In order to rationalize the pavement analysis and design processes models were developed to characterize a range of key inputs. The models were devised for use with a range of pavement design systems including the current Hong Kong pavement design method covered by the Guidance Notes on Pavement Design, Research and Development Division, (1993/22).
In Hong Kong, flexible pavements comprised a subgrade which was typically decomposed granite material, crushed granular subbase material, bituminous roadbase material and bituminous surfacing material. The pavement details are shown in
Chapter Four, Table 4.1. The models developed under this project were based on standard pavement configurations and there was no attempt to modify the type of material used in each layer ofthe pavement or the order of the layers in the pavement structure. In addition, materials incorporating non-standard grading or binders were not considered as they represented a relatively small proportion ofthe materials produced in Hong Kong.
Key areas offocus in this research project, were;
development of commercial vehicle damage factors. The vehicle loading data were collected using; static dynamic weighbridge and piezo-electric weighbridge surveys, Annual Traffic Census records compiled by the Hong Kong Transport Department. The model development were discussed in Chapter Five,
prediction of pavement design temperature for Hong Kong. Data was compiled during a 12 month continuous survey of an instrumented pavement section at the Hong Kong Observatory in King's Park, and an 18 month survey of ten instrumented control sites in the Shatin New Town highway network. The details of temperature modeling are discussed in Chapter Six,
development of models for determination of the time ofloading associated with commercial vehicle speed and modeling the affect of the time ofloading and temperature on the stiffuess of the bituminous layers in flexible pavements. The details of this modeling are discussed in Chapter Seven,
development of models for the determination of flexible pavement failure criteria. The models for this purpose were based on data from laboratory and FWD assessments. They covered; fatigue characteristics, compressive strain and creep. The details are discussed in Chapter Eight,
modeling the influence of pavement temperatures, applied stress and time ofloading on FWD deflections and bituminous material moduli. The development of models for the assessment of subgrade properties using corrected FWD deflections are also discussed. The data used for these tasks were collected from an 18 month survey of road temperatures and deflections at ten selected control sections in the Shatin New Town highway network. The details ofthese assessments are discussed in Chapter Nine.
In evaluating the suitability of these models it was inevitable that the structural analysis of existing pavements needed to be carefully considered. The nature of the layered pavement structures with complex material characteristics required the use of computer hardware and software for the assessment of material properties and the evaluation of critical stresses strains and displacements. A number of established flexible pavement design systems were investigated in order to assess the validity of the models covering a range of design life in terms of millions of standard axles, (MSA), typical for Hong Kong pavement conditions. The programs used for comparative analysis included; PC versions of; EFROMD-2, for the determination of pavement layer moduli from the analysis ofthe falling weight de:flectometer, (FWD), deflection bowls, CIRCLY, for the evaluation of stresses, strains and displacements in the layered pavement system and the Shell Pavement Design Manual, (SPDM) for the monitoring stiffuess changes with temperature through the pavement cross-section based on thermocouple monitoring is Shatin, and BANDS, for the determination of bitumen and bituminous material stiffness characteristics, based on material properties and pavement temperatures.
This thesis was developed with the intention that it would function as a working document, and as such key information was repeated where it was considered necessary to assist the reader to follow the discussion. In other situations references
were made to locations where the relevant infonnation were located throughout the text.
School:The University of Hong Kong
School Location:China - Hong Kong SAR
Source Type:Master's Thesis
Keywords:road materials china hong kong pavements design and construction
Date of Publication:01/01/2000