The assessment of coarse granular materials for performance based pavement foundation design

Abstract

The need to use more recycled and marginal materials in pavement foundations is encouraging moves towards performance based specifications. Such an approach needs data on the fundamental material parameters of stiffness and resistance to permanent deformation (strength) to allow analytical design and achieve comparable compliance testing on site. Whilst a number of laboratory and field tests to measure such performance exist, all have limitations relative to either the particle size of materials that can be tested and/or correlation between the laboratory and field derived data. This paper presents the development of a large scale resiliently lined steel laboratory material box tests proposed for routine material assessment. The test utilises a Lightweight Deflectometer, similar to that proposed for field compliance testing to provide performance data from compacted large particle size granular materials. The system developed utilises a "soft" base condition to replicate typical subgrade stiffness and allows wetting and drying of materials to assess their environmental stability. The results show that such a test can simply provide suitable data for performance based design, but consideration needs to be given to the water content of materials, the time of testing after compaction, and the use of appropriate boundary conditions. These findings have both implications not only for the developed tests but for field compliance testing of pavement foundations.

Performance-Based Analysis in Civil Engineering: Overview of Applications

“…Thus, civil engineers would seek an optimal design of pavement layers and subgrade so as to reduce the life-cycle cost of designed pavements. Various applications in this area [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] are summarized in Table A2.…”

“…Despite the development of prediction models, both lab testing and in-suite measurements were reported to properly assess physical pavement response. Lambert et al [41] used four different materials for pavement subgrade design: mudstone, crushed concrete, site-won sandy gravel, and crushed rock. They performed both lab and field tests to assess the performance of granular materials in terms of composite stiffness and strength with respect to moisture content.…”

Developing Statistical Limits for Using the Light Weight Deflectometer (LWD) in Construction Quality Assurance

“…The Clegg hammer device is similar to the LWD and is used to measure the subgrade stiffness (i.e., to predict CBR values) as a function of the deceleration rate that results from dropping the mass. Soil with a higher bearing strength decelerates the mass more rapidly (Boston, Robek, & Rathom, 2012;Kim et al, 2010;Lambert et al, 2008).…”

“…Typically, these devices usually measure a single deflection on the center of a bearing plate or on the surface of the prepared material being tested. The measured deflection may relate to the influence of one or more layers of material and could be used to determine the field values of parameters relevant in quality control and quality assurance (Lambert, Fleming, & Frost, 2008).…”

“…This rate could be utilized to measure many material properties including CBR, shear strength of granular materials, subgrade resilient modulus, elastic modulus, and soil classification. These properties of foundation materials can be routinely assessed using the DCP, but it is not suitable for coarse materials due to the DCP's relatively low impact energy and small cone size (Alshibli et al, 2005;Kim et al, 2010;Lambert et al, 2008;Nazzal, Abu-Farsakh, Alshibli, & Mohammad, 2004).…”