Application of the Taguchi Method to Enhance Bearing Capacity in Geotechnical Engineering: Case Studies

In this study, the Taguchi design of experiments (TDOE) is employed to enhance the bearing capacity of geotechnical structures. To this end, two different case studies, including tapered helical piles as a novel kind of deep foundation (Case 1) and a shallow foundation resting on braid-reinforced soil as a new type of soil reinforcing technique for shallow foundation beds (Case 2), are studied. A series of large-scale tests, including pile loading tests in frustum confining vessel (Case 1) and standard plate load tests in test pit (Case 2), have been conducted in conjunction with numerical analyses. To the best of the authors' knowledge, this study is the first of this kind that uses the capability of the TDOE method to evaluate and improve the bearing capacity using large-scale tests. After conducting the tests, analysis of signal-to-noise, analysis of means, and analysis of variance were used to interpret the experimental results, to obtain the optimum condition, and to determine the percentage of each factor's participation in bearing capacity. Moreover, the Taguchi method output predictions are compared with the test observations and numerical modeling results. The comparison between test results and TDOE method predictions confirms that the Taguchi method can predict the bearing capacity well (R-2 > 0.95). Additionally, verification tests on optimum models show a low level of relative error (RE < 5%) between the TDOE predictions and test results for both the case studies. Therefore, the results prove the ability of the TDOE method to predict and determine the optimum condition in geotechnical bearing capacity problems.