Estimating an empirical equation connecting subgrade reaction modulus with cone penetration test for sandy soils

Abdelaziz Ahmed Bohagr 1, Ghassan Ahmed El gehani 1, Mohammed Mahmoud Boudejaja 1, * and Mustafa M Amami 2

1 Civil Engineering Department, University of Benghazi, Libya.
2 Engineering Surveying & Space Geodes, University of Benghazi, Libya.
 
Global Journal of Engineering and Technology Advances, 2021, 09(02), 001–008.
Article DOI: 10.30574/gjeta.2021.9.2.0127
Publication history: 
Received on 05 September 2021; revised on 28 October 2021; accepted on 30 October 2021
 
Abstract: 
In geotechnical engineering, the coefficient of subgrade reaction is regarded as one of the most important parameters used for describing the interaction of soil and structure as well as describing some soil characteristics, subgrade reaction coefficient can be calculated theoretically using many different formulas, laboratory via specific well-known tests, and in site through field plate loading test. On the other hand, the cone penetration test is one of the most frequently used field tests to investigate the soil. The lately carried out researches showed a good relation between the subgrade coefficient and the tip resistance collected from the CPT, but the results obtained from the proposed method are still doubtable.
In this paper, fifteen plate load tests and thirty CPTs, already collected for private site investigation project, have been used for finding the best fit equation connecting the subgrade reaction coefficient Ks with the tip resistance qc. The finds of the established equation have been compared extensively with those of other well-known related equations. The results show the ability of the concluded equation to get Ks results in the acceptable range of sandy soils. However, the depth and shape effect on the suggested formula need further investigations since all the plate load tests in this project have been carried out on the soil surface with a 45 cm diameter circular plate.
 
Keywords: 
Cone penetration test CPT; Module of subgrade reaction Ks; Plate Load Test; Tip resistance qc
 
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