A direct algorithmic process can deal with the solution of the support–ground interaction in a circular tunnel excavation through the convergence-confinement method (CCM) with the concept of increment. This process is the so-called direct calculation method (DCM) that can find solutions, the mobilized support pressure and the convergence, in the analysis of CCM. To achieve the solution, using two linear equations in the elastic region and Newton’s recursive method to find the roots in the plastic region are proposed and realized by a calculated spreadsheet. The validity of the algorithmic process for the analytical solutions was investigated and verified by the finite element computation, and compared with the published results, Rocksupport (2004), Oreste (2009), and Gschwandtner-Galler (2012). The results obtained between DCM and related studies show no significant differences.
Laying ballastless track on railway bridges has the advantages of reducing the train noise problem, improving passenger comfort, and reducing track maintenance costs. Therefore, railway bridges with ballastless track have gradually turned into a major trend in railway systems all over the world. In Taiwan, railway bridges with ballastless track have been in use for many years, with ballastless track turnouts also starting to be constructed in recent years. Where railway bridges with ballastless track turnouts are located in urban areas, special consideration must be given to the road crossings and the use of continuous bridges in the turnout zones. Accordingly, there arise a number of difficulties related to the bridge configurations or the continuous length of bridges being excessively long. Often, such situations necessitate the use of extremely large-sized bridge piers in the bridge design, or create the risk of serious damage to the pier structure should insufficient attention be given to any of the factors. This article will take a continuous prestressed concrete bridge as an example. The prestressed concrete bridge must be absolutely continuous, be able to include ballastless track turnout zones, and meet the needs of crossing roads. For this example, the length of the continuous prestressed concrete bridge is over 300 m. This article will also discuss the configuration of a continuous prestressed concrete bridge of railway, and-through the analysis of track-bridge interaction and temperature detection-provides suggestions on the optimal configuration model of the continuous prestressed concrete bridges, which should allow improper configuration and possible structural damage to be avoided.
This study and verification are based on the Brillouin frequency shift (BFS), which is related to the strain and temperature changes of a single-mode fiber, because such a shifted frequency can be quantitatively measured and converted to strain and temperature differences. We explain the installation of a Brillouin distributed fiber sensing system (DFOS) on an actual operating railway to measure the temperature and strain of the rail. In addition, the measured data were calculated and analyzed, revealing the geometric irregularity of the tested rail and the location of the abnormality. We obtained a temperature difference of 12.1 °C between the temperature distribution of the measured rail and the atmospheric temperature, and there was a 1.5 h delay between the two. We also obtained rail irregularities ranging from −0.3 to +0.4 mm by calculating the slight strain difference of the rail in this test.
Carrying out underground excavation work with retaining pile supports adjacent to a running railway is a risky and cautious job. To evaluate the safety and practicability of underground excavation, a three-dimensional finite element program was developed and used in this study to simulate and analyze the mechanical behavior of the gravel layer in response to excavation to serve as the design for retaining piles as supports. Monitoring instruments (such as inclinometers and subsidence observation points on railway track surfaces) were installed during construction to provide immediate monitoring of the excavation area and information for safety assessments. The calculation process in the numerical analysis included the execution of programs such as pre-processing, central calculation, and post-processing, as well as the simulation of construction steps, such as the initial stress of gravel layer, railway vehicle load, layered excavation, and support installation. By comparing the results of 3D finite element analysis with monitoring data, it was found that the construction method of excavating the gravel layer near the adjacent railway and supporting it with retaining piles provides a reliable engineering technology. The results of the comparative analysis were all within a safe range and showed a consistent trend.
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