Optimization of the Ultimate Bearing Capacity of Reinforced Soft Soils through the Concept of the Critical Length of Stone Columns

Nour El Islam Boumekik, Mohamed Labed, Mekki Mellas, Abdelhak Mabrouki


The objective of this paper is to develop an analytical equation based on the concept of the critical-length of columns in order to optimize the ultimate bearing-capacity of soft soils, supporting a strip footing and reinforced by a group of floating stone columns. Optimization procedure was performed on three-dimensional numerical models simulated on the Flac3D computer code, for various soft-soils with different undrained-cohesions (Cu=15–35kPa), reinforced by columns of varying lengths (L) and area replacement ratio (As=10-40%), considering different footing widths B. Obtained results indicate that the optimal bearing-capacity ratio (Ultimate bearing-capacity of reinforced soil/unreinforced soil) is reached for the column critical-length ratio (Lc/B) and increase with increase of the later ratio, depending  on As and Cu. Analysis of results also showed that the optimal values of the bearing-capacity ratio in the reinforced soils remain bounded between the lower and higher values (1.28-2.32), respectively for minimal and maximal values of the critical-length ratio (1.1) and (4.4). Based on these results, a useful analytical equation is proposed by the authors, for the expression of the critical-length; thus ensuring an optimal pre-dimensioning of the stone columns. The proposed equation was compared with the data available in the literature and showed good agreement.


Doi: 10.28991/cej-2021-03091737

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Stone Columns; Critical-length; Footing; Ultimate Bearing Capacity; Numerical Simulation; Soil Reinforcement.


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DOI: 10.28991/cej-2021-03091737


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