Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, -, Turkey
Approval Date: 2017
Thesis Language: Turkish
Student: Güneş Babagiray
Supervisor: SAMİ OĞUZHAN AKBAŞ
Open Archive Collection: AVESIS Open Access Collection
Abstract:In this study, the behaviors of buried pipes protected by geosynthetics in various combinations under impact loading were examined. For this purpose, laboratory and field impact load experiments were carried out with HDPE pipes that are frequently used in practice. In the laboratory experiments, 110 and 160 mm diameter pipes were tested under impact load with protective layers consisting of single and double layer geosynthetics laid at varying depths and wrapped one and four times around the pipe. In the full-scale impact load experiments carried out in the field, different types of single-layer and laminar geosynthetic material types at a fixed depth were used as the protective layer on 600 mm outer diameter pipes. In these experimental studies, using the acceleration measurements taken from the pipe surface, the energy adsorption capacities of the various protective layers were calculated and evaluated together with their cost. As the depth of the protective geosynthetic layers laid on the buried pipe approaches to the ground surface, better protection performances have been observed. In the experiments with single-layer geosynthetics, the most successful protection was obtained through the use of geonet 3D with 72,9% acceleration adsorption. In the experiments where two layers of geosynthetic materials were placed at a depth of 120 mm, the most successful performance in terms of acceleration adsortion capacity was obtained by the combination of geonet 3D and geocell (h=50 mm, t=1 mm). Increasing the number of turn of wrappings increased the cost, but it also reduced the maximum acceleration exerted on the pipe through the impact load, thereby increasing the protection performance. Comparing the results of tests using single layers of geonet 2D, geonet 3D and geotextile elements and those with wrapping technique, quadruple wrapping using geonet 2D (rockshield) has been the most successful application, with an acceleration adsorption capacity of 83,0%. Considering the 29 laboratory impact tests, the protective structure consisting of the combination of geocell (h=50 mm, t=1,5 mm) and geotextile with 91,7% acceleration adsorption capacity has demonstrated the best performance. In the field tests, geotextile exhibited the best performance, especially with increasing density, with a 83,3% acceleration and a 46,6% pressure adsorption capacity. Evaluating the results of geosynthetics that were used both in the field and laboratory experiments, it can be stated that geocell exhibited the lowest success in terms of acceleration adsorption performance, whereas geotextile element was observed to have a higher protection potential against impact loads. In terms of "acceleration adsorption rate per unit cost", it has been shown that the optimum performance has been achieved by using single layer of geogrid.