Browsing by Author "Yilmaz, Mustafa Tolga"
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Article Citation Count: 0The effect of group behavior on the pull-out capacity of model soil nails in high plasticity clay(Springer int Publ Ag, 2024) Akış, Ebru; Bakir, Bahadir Sadik; Yilmaz, Mustafa Tolga; Civil EngineeringSoil nailing technique is widely used in stabilizing roadway and tunnel portal cut excavations. The key parameter in the design of soil nail systems is the pull-out capacity. The pull-out capacity of soil nails can be estimated either from the studies involving similar soil conditions or from the empirical formulas available in the literature. Particularly, it has been documented placing nails closer than a certain minimum distance results in a reduction in the pull-out resistance of a nail placed in sand. However, this requirement has not been discussed for the nail groups located within clay formations. In order to investigate the influence of nail spacing on the pull-out resistance of nails, a series of laboratory pull-out experiments were performed in clay of high plasticity. The results of these experiments showed a remarkable trend. Specifically, there was a significant reduction in the pull-out capacity of a nail when the spacing between nails two times the nail diameter (2 & Oslash;). In contrast, the pull-out capacity of a nail embedded in clay remained unaffected by neighboring nails, provided the spacing was maintained at six times the nail diameter (6 & Oslash;). In addition, during the conducted pull-out tests, it was observed that the failure mode of a single nail and 6 & Oslash; spaced group nails near the surface results as heaving around the single nail. However, in the case of closely positioned (2 & Oslash; spaced) nails, the affected area following nail failure exhibits distinct characteristics, which operate as a group. This leads to the occurrence of failure in the form of heaving around the group of nails.Article Citation Count: 3Investigation of the effect of shearing rate on residual strength of high plastic clay(Springer Heidelberg, 2020) Akış, Ebru; Mekael, Ahmad; Yilmaz, Mustafa Tolga; Civil EngineeringThe residual shear strength on failure plane is a crucial parameter to be estimated for analysis of an active landslide. This strength must be determined precisely to build a reliable theoretical model for calculations. The multi-reversal direct-shear test is a practical method to determine this shear strength in laboratory due to wider availability of apparatus. The shearing rate is among the factors that significantly affect the precision of test results for clay specimens. However, limits for this rate are yet to be clarified to shorten the duration of multi-reversal direct-shear tests. In this study, two tests series at different shearing rates were performed to investigate the effect of shearing rate on the residual strength of highly plastic clay sample recovered from a landslide area in Northern Turkey. The shearing rates were set to 0.024 mm/min which was decreased to 0.001 mm/min during the last forward shearing phase for the first test series, whereas the rate was fixed to 0.0007 mm/min for the second test series. The residual friction angle determined by these tests was interpreted by using a theoretical analysis of the landslide, and they were compared with the estimations due to empirical relationships given in the literature. It is concluded that, although the rate of 0.024 mm/min is consistent with the recommendations in literature, this rate can yield overestimation of residual shear strength determined in multi-reversal direct-shear tests.