Discussion of Sharma, R., Chen, Q., Abu-Farsakh, M., and Yoon, S. (2009) “Analytical modeling of geogrid reinforced soil foundation” Geotextiles and Geomembranes, vol. 27, pp. 63–72

Abstract

The discusser appreciates the authors’ effort in conductingmodel tests and in deriving an analytical model for the bearingcapacity of footings on reinforced soil foundations. The discusseralso acknowledges the authors used the analytical model of Huangand Menq (1997) to interpret their results. The disagreementbetween the values of bearing capacity ratio (BCR) calculated usingHuang and Menq’s model and the test results obtained by theauthorshighlightssomeaspectswhichmighthavebeenignoredbythe authors.(1) The cohesion intercept (c) of the moist soils (sand and siltyclay) used by the authors may account for the generally lowvaluesofBCRobtainedbytheauthors.Ingeneral,experimentalvalues of BCR were lower than 1.5 in author’s study, whileabout 2–2.5 times larger values of experimental BCR werereported by previous studies (Huang and Tatsuoka, 1990;Takemura et al., 1992; Khing et al., 1992) based on similarreinforcing conditions for dry sands. The existence of thecohesion intercept also accounts for the discrepancy betweenthe test results and those calculated using Huang and Menq’smodel which was originally derived for cohessionless (c¼0)soil.(2) The ‘mode 3’ failure mechanism was used to simulate the testresults for silty clay foundations; the ‘mode 4’ failure mecha-nism was used to simulate the test results for sandy founda-tions. This contradicts the principle of mechanics which statesthat the failure is always controlled by the critical mechanism,instead of one based on subjective judgments.(3) Some important parameters were introduced in the authors’analytical model, such as the cohesion intercept (c), elasticmodulus (E