Geotextiles used as reinforcing elements in soil structures transfer a majority of the shear stress from the soil to the reinforcement by friction. The interfacing ability manifested by soil/geotextile frictional contact is thus very important in the perfor mance of reinforced soil structures. In this study, the interaction criteria of geotextiles with soil are evaluated by conducting model pull-out friction tests in a laboratory. The study includes an investigation of the influence of surface roughness of different woven geotextiles embedded in glass beads on interfacial friction under varying normal stresses. Pull-out friction tests on embossed acrylic plates are also done in the same manner to support beads/geotextile friction test results. The surface roughness of woven geotextiles can influence in-soil frictional behavior depending on the relationship between soil particle size and surface asperity of the geotextile: the closest fit of soil particles into the surface irregularities gives the maximum frictional resistance.
This paper deals with the false-twisting mechanism and the twist distributions of a yarn in both the twisting and untwisting zones using an air twister, which provides air jet owing to air vortex.In the case of using air jet twister as shown in fig. 2 the twisting and untwisting phenomena are analyzed by taking photographs and the following results are obtained: 1) The twist of the twisting zone immediately propagates to the untwisting zone in the case of the non existence of solid contact which obstructs the propagation of the twist in the air jet twister, and the twist of the whole zone into which the twist is able to propagate is observed to be the same direction as the twisting zone. The twist distribution is shown in fig. 10. 2) The yarn is rotated by the air vortex and makes the balloon, and its configuration becomes a complicated form which holds inherent balloons as the air pressure increases.3) It is considered that the yam rotates as if without contacting the twister and is twisted by the ballooning at the place of twister. It is so considered, because the yarn revolutions, as calculated under the considerations of the twist contraction and projective length, agree well with the balloon revolutions obtained from high speed cine-photography. 4) The experimental values of , twist distribution in the untwisting zone meet well with that calculated from the theory of twist propagation, in which the yarn is considered to be viscoelastic.
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