Effect of Grain Size Distribution on California Bearing Ratio (CBR) and Modified Proctor Parameters for Granular Materia
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RESEARCH ARTICLE-CIVIL ENGINEERING
Effect of Grain Size Distribution on California Bearing Ratio (CBR) and Modified Proctor Parameters for Granular Materials Jose Duque1 · William Fuentes2 · Silvia Rey1 · Enois Molina1 Received: 8 February 2020 / Accepted: 25 May 2020 © King Fahd University of Petroleum & Minerals 2020
Abstract The California bearing ratio (CBR) and modified proctor parameters (maximum dry unit weight 𝛾d(max) and optimum moisture content wopt ) are valuable indicators of the compaction quality of subgrades, embankments and granular fills. In the engineering practice, correlations of these variables with granulometric properties of the soil are required, especially since testing for these variables can be time-consuming when a large number of samples are analyzed. In this work, 20 different granular materials with varying grain size distributions were prepared and tested. Their grain size distribution properties and their parameters CBR, 𝛾d(max) and wopt were determined. These results were analyzed along with a compilation of 77 additional experimental results on granular materials reported in the literature. The influence of some granulometric properties on the parameters CBR, 𝛾d(max) and wopt was statistically examined, and some correlations were proposed for these variables. Subsequently, it was demonstrated that the proposed correlations show better accuracy tother reported correlations in the literature. Finally, this work ends with some concluding remarks Keywords California bearing ratio (CBR) · Grain size distribution · Modified proctor · Granular soils
1 Introduction The compaction quality of subgrades and compacted granular fills is evaluated through the analysis of some geotechnical parameters, as for example, the California bearing ratio (CBR), the maximum dry unit weight 𝛾d(max) and its corresponding optimum moisture content wopt . The CBR is obtained from a penetration test, which indirectly evaluates the strength of soils [1, 2], while 𝛾d(max) and wopt are compaction parameters obtained from the modified Proctor test. Their determination is of great importance for the design of pavements and some foundation structures [3–7]. These parameters depend, among others, on some physical properties of the grains, such as sphericity S , roundness R , smoothness Sm , compaction energy and grain size distribution [8–18]. In the engineering practice, empirical correlations to determine the parameters CBR, 𝛾d(max) and wopt as a function of some physical and index properties of the soil, are useful * Jose Duque [email protected] 1
University de la Costa, Barranquilla, Colombia
Findeter, Bogotá, Colombia
2
to analyze and interpret a large number of experimental results [19–26]. Accordingly, several authors have conducted experimental works to draw some conclusions in this regard and to provide some correlations for the CBR [1–7, 27–32], and the modified proctor parameters 𝛾d(max) and wopt [8–11, 33–40]. Table 1 summarizes some of the available correlations in the literature for th
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