Estimation of lateritic soils elastic modulus from CBR index for pavement engineering in Burkina Faso
- PDF / 866,431 Bytes
- 9 Pages / 595.32 x 841.92 pts (A4) Page_size
- 60 Downloads / 225 Views
International Journal of Pavement Research and Technology Journal homepage: www.springer.com/42947
Estimation of lateritic soils elastic modulus from CBR index for pavement engineering in Burkina Faso Yassia Gansonréa*, Pierre Breula, Claude Bacconneta, Miguel Benzb, Roland Gourvèsb a Université
Clermont Auvergne, CNRS, SIGMA Clermont, Institut Pascal, F-63000 Clermont-Ferrand, France b Department of Research and Innovation, Sol-Solution, France
Received 22 April 2020; received in revised form6 August 2020; accepted 23 August 2020
Abstract
Pavement design with some soils, such as lateritic soils, is still a “real challenge” in some countries. In the tropical countries guide, recommended for Burkina Faso, the pavement design is performed according to the class of traffic and the soil bearing capacity, characterized by the soaked CBR index (Californian Bearing Ratio). In practice, the validation of pavement structures is possible using numerical models requiring the thick ness, the Poisson’s ratio and the elastic modulus of the pavement’s layer materials, as input data for the stresses and the strain calculation. Until now, the guides provide none value of the modulus for the lateritic soils. So, the modulus is estimated by assimilating the lateritic soils to untreated coarse gravels (or GNT: Graves Non Traitées in the French guideline) with known modulus or by using empirical correlations based on the soaked CBR index. This approach lead to an erroneous estimating of modulus of lateritic soils, and to an under or overdesign of pavement structures, due to the fact that the spec ific correlation suitable for these soils in Burkina Faso is not known. So, this paper was interested in the characterization of lateritic soils from Burkina Fas o, according to their CBR bearing capacity, their elastic modulus and to their compaction parameters, after having been assured that the selected soils were representative of country’s road soils. The objective is to perform a specific model for estimating the elastic modulus of these soils. Analysis of the studied parameters showed that CBR and elastic modulus, both depend on moisture content and dry unit weight of soils. A correlation was thus performed between elastic modulus and CBR index. The specific correlation obtained is in power form: E= a.CBR b and relatively close to whose obtained by Green and Hall, where a=66.50 and b=0.526. Keywords: Pavement design; Lateritic materials; Modulus and CBR correlation
1. Introduction 1.1. Lateritic Soils Laterite is a material resulting from the bedrock physical and chemical weathering under tropical climate. From engineering point of view, lateritic soils and mainly the lateritic gravels, constitute an abundant source of road-building materials in tropical climatic zones. Because of their availability, they are used in pavement engineering, mainly in the base, sub-base or the subgrade layers of road as showed in [1,2]. The pavement’s design requires the knowledge of the Californian Bearing Ratio (CBR) or in the best case, the Young
Data Loading...
