| Summary: | 碩士 === 中原大學 === 土木工程學系 === 87 === The advantages of geogrids in reinforcement of earth material have been evaluated and confirmed. Pull-out test is by far the most commonly used method for determining the interface properties such as interaction between soil and geogrid. The objective of this study is dissertation aims to present their mechanical behavior and interaction mechanism for the future applications.
In this study, a custom-made, large-scale pullout testing device, with a size of (H)90cm*(W)100cm*(L)150cm is used. Four types of geogrids and one type of sandy soil are used, and the pressure is applied by the air bag. The interface between geogrid and soil was forced to mobilize displacement, Connecting the conjunctions of the geogrid with five LVDTs, measurements are taken of deformation of the geogrid, and combining the tensile strength of the geogrid, we can obtain the stress distribution on the geogrid. Observing and analyzing test results, the mechanisms were determined.
According to the results of this study, pullout resistance development can be categorized in the following three stages： (1) The period of frictional resistance development. (2) The period of passive resistance development. (3) The period of soil mass plasticity. Under lower normal stress, the pullout resistance of the geogrid is almost applied by frictional resistance, and the proportion of frictional resistance decreases with confining pressure. While using the concept of average resistance to evaluate the pullout interaction coefficientμ,the effective area method can apply better simulation, but the maximun slope method may have greater variance as the accuracy of the tensile development curve. Geogrid's pullout resistance increases with confining pressure, while pullout interaction coefficientμdecreases with confining pressure, the proposed models are compared with the pull-out test results that show they can predict the relationship betweenμvalue and confining pressure .
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