چكيده به لاتين
Sleepers are transverse elements of ballasted tracks that maintain the geometry of the track and bearing and transferring the incoming loads from the rail to the underlying layers. Wooden sleepers are one of the oldest types of railroad sleepers, which gradually replaced by steel and concrete sleepers due to their short lifespan, environmental problems caused by cutting down trees, etc. Nowadays, cement concrete sleepers, due to their advantages such as providing adequate lateral resistance, non-flammability, easier access to materials for production, etc., have made it the most common type of sleeper used in railway tracks in the world today. However, this kind of sleepers also has disadvantages such as low resistance against impact forces caused by the passage of the fleet, low resistance in corrosive environments, etc., which lead many researchers to find new materials and remove the existing limitations of cement concrete sleepers. The results of these investigations have shown that the composite sleepers produced by removing water and cement and replacing them with polymer materials have a good performance compared to the existing concrete sleepers. Despite the good experiences of using this type of sleepers, the production and use of composite sleepers has no place in Iran’s railway infrastructure. For this reason, in this research, the investigation of these sleepers in two phases of determining the optimal mix design and evaluating the impact resistance of the sleepers is on the agenda. In order to achieve the mixed design of composite sleepers based on polymer adhesives, due to the lack of a written method for calculating the mixed design, previous researches were selected as the basis of the tests and with the change in the type and amount of materials used, the final design with a compressive strength of 58.4 MPa after 24 hour, 69.2 MPa after 7 days and 72.4 MPa after 28 days is obtained. In the negative bending moment test of the center of the sleepers, the composite sleeper made by optimized mix design has started to crack at a load of 230 kN, which is 92 kN for B70 sleepers. Similarly, in the positive bending moment test of the rail seat, the composite sleeper has started to develop and grow cracks at loads of 32.9 and 1.36 tons, respectively, which this values are 18.8 and 23.6 tons for the B70 sleepers. The results of the 100 kg weight drop test show that the performance of the composite sleepers was better than the cement concrete sleepers, as in the resistance tests, in such a way that the composite traverse began to crack when the weight drop from a height of 100 cm and after the crack grew, drop from 200 cm height, the crack grows up to the top surface of the traverse and the top surface of the traverse fails. Under the same conditions, B70 sleepers begin to crack at a drop height of 50 cm and crack growth begins at a height of 60 cm. The failure of B70 concrete sleepers occurs when the weight drops from a height of 120 cm. Also, in BR70 concrete sleepers, the first crack was created at a drop height of 30 cm, and the growth of the crack started with the increase of the fall height from a height of 40 cm, and the failure of the traverse occurs when the weight drops from a height of 100 cm. The results of the resistance and impact tests shows that the performance of composite sleepers is much better than the cement concrete type and can be used as an alternative to the existing sleepers.
