Browsing by Author "Shirazi, Mohammad Gharehzadeh"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Performance of Kenaf geotextile in improving bearing capacity of soft soil
    (Universiti Teknologi Malaysia, 2019) Shirazi, Mohammad Gharehzadeh
    Soil improvement techniques such as geotextile reinforcement system are used to increase the bearing capacity of soil and to reduce the structure's settlement. Geotextiles which are commercially made from synthetic fibres, however, have been linked with some environmental issues. To accommodate these concerns, several efforts had been done to study on the use of bio-base materials. This study attempts to investigate on ground improvement method by using Kenaf geotextile as a bio-base material. To this end, two phases of investigation were conducted. The investigation of the behaviour of Kenaf geotextile, manufactured with and without sodium hydroxide (NaOH) treated fibres, subjected to tensile loading was first carried out. Due to the high water absorption capability of Kenaf fibre, the effect of wet and dry condition on tensile behaviour of Kenaf textile was investigated. Two patterns of weaving Kenaf namely plain and hexagonal patterns which have two different opening size between their yarns (0*0, and 2^2 mm) were produced. Tensile strength of Kenaf was then determined by using the wide-width strip test based on the ASTM 4595 standard. The most obvious finding emerged from this part of study is that the alkaline treatment using 6% NaOH has significantly improved the tensile properties of the woven Kenaf as compared to those of untreated Kenaf textile. Next, the Kenaf textile in dry condition has shown the highest tensile strength as compared to its wet counterpart. Furthermore, the Kenaf textile with 0 mm opening size between their yarns has shown the highest tensile strength and elongation at break value in comparison to that with 2 mm opening size. Finally, the results show all the plain patterns presented the highest tensile properties as compared to those of hexagonal patterns. In the next stage of the investigation, the effects of Kenaf geotextile reinforcement on the white kaolin clay bearing capacity under rigid strip footings were examined. The effect of the first geotextile reinforcement depth or top layer spacing (d/B), the vertical spacing between reinforcement (S/B) and number of reinforcement layers (N), where B is the footing width, on the bearing capacity was investigated by a series of small-scale laboratory tests and numerical program using finite element software PLAXIS 2D version 2017. Unreinforced sample was tested for comparison purposes to determine the improvement bearing capacity factor (Nc). Research variables include four different d/B ratios of 0.25, 0.5, 0.75 and 1.0; three different S/B ratios of 0.25, 0.5 and 0.75, and different number of reinforcement layers from 1 to 4, for selected Kenaf geotextiles. The results clearly show that the bearing capacity of rigid strip footings on kaolin clay was significantly increased by the installation of Kenaf geotextile layers in the kaolin clay. It was found that the optimum d/B ratio which resulted in the maximum ultimate bearing capacity of the Kenaf-reinforced model was about 0.25. The ideal S/B ratio which brought about the highest level of ultimate bearing capacity of the Kenaf-reinforced model was about 0.25. The results of laboratory tests and PLAXIS analyses have also shown that the optimum number of reinforcement, N is 3 layers with a very small difference with the four-layer system. Finally, a very high agreement between the experimental and numerical results on the position and the values of the Kenaf geotextile was observed.