Effects of the configuration of a baffle–avalanche wall system on rock avalanches in Tibet Zhangmu: discrete element analysis

Rock avalanches with a high mobility and kinetic energy pose a potential geological risk to surrounding buildings. Baffles and avalanche walls are effective ways to protect these buildings. However, the primary focus of previous studies has been on baffles or avalanche walls alone, and there have been very few studies investigating the effectiveness of a combination of baffles and avalanche walls as a countermeasure against rock avalanches. In addition, previous studies on lab-scale tests and numerical analyses often did not take the actual topography effects into consideration. In this study we adopted a numerical simulation approach based on an actual project in the town of Zhangmu, Tibet, with the aim to investigate the effect of different configurations of a combined baffle–avalanche wall system on impeding the kinetic energy of rock avalanches. A series of numerical analyses with discrete element methods (DEM) were conducted. First, the effect of three different pile groups on the reduction of the effect of the rock avalanche was studied using the numerical modeling study. Secondly, the influence of the size of the retaining wall on the maximum impact force of the rock avalanche was studied. Finally, a DEM modeling study on the energy dissipation capacity of the baffle–avalanche wall system was conducted. The results demonstrate that an arrangement of different baffle–avalanche wall systems will produce different results in terms of dissipating the energy of rock avalanches: when the wall is long enough to block all rock masses, enhancing baffle density will decrease the maximum impact force exerted on the avalanche wall; however, if the wall is just long enough to protect the target region, reducing baffle density will decrease the maximum impact force exerted on the avalanche wall. The results of this study are significant in terms of providing guidelines for the design of baffle–avalanche wall systems for protection against rock avalanches.

     

Surface deflection-based reliability analysis of asphalt pavement design

The surface deflection of asphalt pavement reflects the strength and stiffness of the entire structure, which can be used to evaluate the rutting life of asphalt pavements. However, it is influenced by various stochastic variables including traffic loads, material properties and structural thickness of each pavement course. The uncertainty of above stochastic variables is of significance for accurately predicting the rutting life of asphalt pavement. In this study, the statistical characteristics of stochastic variables of asphalt pavement were assessed based on the field data collected from asphalt pavement projects. A unique formula with a fairly good accuracy was found using multiple linear regression based on numerical simulation results to ease the calculation of pavement deflection during the reliability analysis. It is shown that the stochastic variables of asphalt pavement can be well characterized by normal distribution or logarithmic normal distribution. The regressed formula to calculate the surface deflection of pavement has a fairly good accuracy with an error of less than 6.0% compared to the numerical method. The proposed surface deflection-based reliability analysis can be used easily to evaluate the influence of input parameters on the rutting life and to guide the structure design of asphalt pavement with required reliability.

     

55MW燃煤发电机组主蒸汽旁路的爆管分析及处理

主蒸汽旁路是在主蒸汽管道的电动主汽门发生故障、无法正常给汽轮机供汽时紧急启动的管道系统，所以旁路处于完好的备用状态是机组正常运行的必要保障。我公司的#3发电机组主蒸汽旁路在运行仅仅1年后就发生了爆管事故，不但没有起到备用功能．反而导致了机组停机的事故。经检查分析为错用材质所致，将设计材质12CrlMoV错用为20G钢材。本文重点对爆管原因进行分析，同时制定合理的措施进行更改，并做了必要的检验，保障了机组的正常运行。