Effect of cyclic loading on connection strength of geosynthetic-reinforced structures

This study investigates the effect of cyclic loading over the connection strength of geosynthetic reinforced segmental (modular) block walls. For this purpose a specially designed machine has been built and reduced size cyclic loading test programme has been utilized. Geosynthetic reinforced walls have so far shown a very good performance under earthquake effects. However one of the key parameter has been generally omitted during design. This is the connection strength parameter mobilized under cyclic (repetitive) loading effects. Consequently, the research adressed this issue of whether there is a loss of strength or not after a series of cyclic loading tests. For this purpose, a typical rectangular modular block with dimensions of 19cmx19cmx39cm and two types of geosynthetic reinforcements (geotextile and geogrid) have been used during the tests. The test programme involved 3 load cycles (0%-50%, 25%-75%, 50%-75%), 2 reinforcement types, 13 normal load interval (from 150kg to 3250kg) resulting 3x2x13=78tests. All these tests are also repeated twice to get a better and more realistic results so that the total number of tests performed for the study is 78x2=156. The load cycles are determined so that a M=7.5 magnitude earthquake can be represented in the best way that is possible. For this purpose, an equivalent of 15 cycles are considered as suggested by several literature. However, it should be noted that there is no purpose of simulating a scenario earthquake, the purpose is to observe the effects of cyclic (repetitive) loading. At the end of the tests, It can be concluded that the geotextile reinforcement is more sensitive to cyclic loading than as compared with the geogrid reinforcement. It was also observed that the normal load increment, and or load cycle variation does not make significant effect on the change in the connection strength. As stated in the conclusion section of this research, the studies given herein can be extended by other variables (such as block types, reinforcement type etc.) and the effect of cyclic loading over connection can be better understood in a more comprehensive manner.