چكيده به لاتين
Controlling the volume of maintenance operations of ballast layer under cyclic loading and reducing its deterioration and failure are among the important issues that have been investigated by researchers. Reinforcing the ballast layer with the help of various types of reinforcements or trying to replace these materials with granular materials that have the same characteristics as the ballast are among the things that can lead to reducing the deterioration of the ballast. On the one hand, considering the high importance of preserving the environment, solutions that can have less harmful environmental effects by using environmentally friendly materials and materials is in priority. In recent years, the production of steel slag and waste tires have created a large amount of environmental pollution, and their storage or burial has caused serious damage to the environment. Therefore, converting these types of materials into secondary products can create added economic value while reducing environmental problems. In this research, an attempt has been made to investigate the effect of combining the use of the two mentioned products in a new idea in order to reduce the deterioration of ballast. In this regard, the simultaneous use of steel slag in combination with ballast aggregate, along with ballast reinforcement with the help of geogrid made with waste rubber strips and also the ballast box device, has been investigated. For this purpose, 5 samples of different combinations of stone ballast and steel slag including 0%, 25%, 50%, 75% and 100% combinations were studied. According to the tests, it was found that the of Los Angeles result for slag ballast is 23% more than stone ballast. Also, microdual test in wet state for slag ballast is 29% less than stone ballast, which is due to the presence of more elements such as silica in aggregate ballast, as well as the sharp and rough structure of slag materials. Also, during the testing of the ballast box device, which is a cyclic loading simulator, it was determined; Increasing the percentage of slag in the compounds reduces the settlement, but by placing rubber nets at distances of 50, 100 and 150 mm from the bottom of the box, the settlement increases. This increase is due to providing more flexibility by placing a network of rubber bands in the ballast. According to the force-displacement diagrams and the hysteresis loop obtained from the results of the ballast box device, it was determined that the damping ratio increases with the increase in the percentage of slag in each composition, and also the placement of rubber nets at the level of 50, 100 and 150 mm increases the damping compared to when the rubber net Does not exist. So that the 50 mm distance has shown the best performance in terms of increasing the damping, which dynamically acts like a damping body-spring. Also, the hardness of the top layer increased first by increasing the percentage of slag, and then decreased by placing rubber nets at a distance of 50 mm. Therefore, it was generally determined that: firstly, the best dynamic performance of ballast reinforcement with rubber strip geogrids occurred at a depth of 50 millimeters, secondly, adding slag ballast led to the improvement of the performance of these reinforcements. So that by combining 75% of slag aggregates, more favorable results are obtained. The results show that, on average, the values of settlement, damping, hardness and fracture index of the ballast layer with 75% slag and reinforcement with rubber band net at 50 mm level are suitable compared to the state of stone ballast without reinforcement. In this case, the settlement is reduced by about 16%, the fracture index is increased by about 15%, the damping ratio is increased by about 2 times, and the hardness is reduced by about 8%.
