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汶川地震产生了大量的震裂松动山体,为合理评价在这些震裂山体中新建隧道的围岩级别,通过极震区在建隧道现场震裂岩体调查,对震裂岩体特征及其对围岩稳定性的影响进行了分析。震裂岩体是一种受强烈地震波作用后,岩体结构面更加发育,层间结合更差的一种岩体;并且硬质岩和软质岩的震裂特征不同,硬质震裂岩体易产生集中式张裂缝和松动,软质震裂岩体易产生体积式松弛变形。在此基础上,提出了岩体震裂等级,划分为轻微、中等、强烈三种级别,并建立了震裂岩体围岩分级的修正方案,即:轻微震裂岩体对围岩稳定性影响不大,可不考虑降低围岩级别,或者降低0.5级;中等震裂岩体对围岩稳定性有不利影响,围岩级别降低0.5~1级;强烈震裂岩体对围岩稳定性影响极为不利,围岩级别降低1~1.5级。 相似文献
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After 1975, the appearance of finite element numerical limit method and the application and development of computer technology have brought the elastic-plastic analytical calculation of engineering materials into a new era of numerical limit calculation. The new methods, namely, strength reduction method and load increment method, as well as the recently proposed ultimate strain method, are adopted in the rock tunnels studied in this paper. To solve the uncertainty of mechanical parameters of surrounding rock in rock tunnels and provide more scientific and reasonable mechanical parameters of surrounding rock, the surrounding rock classification must be made combining theory, investigation and experience. Taking the surrounding rock classification in rail transit tunnels as an example, the improvement of the classification level includes improving the strength index, mainly adopting the quantitative classification method, reasonably determining the basic index BQ value of rock mass quality, increasing the number of surrounding rock classifications, formulating the surrounding rock classification tables for the running tunnel and the station tunnel, and achieving the coordination and unification of qualitative and quantitative classification methods. Finally, the quantitative indexes of surrounding rock self-stability are determined, and the more scientific and reasonable physical and mechanical parameters of surrounding rocks are put forward through back calculation. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
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Marcus B rner Rolf Isermann 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2005,43(8):601-612
Driver assistance systems have received increased attention as market demands have pushed for improved automotive safety. These systems are designed to aid the driver by preventing any unstable or unpredictable vehicle behaviour. One global indicator for stability and driving conditions could help to manage the control algorithms and driver warning subroutines. Another problem which could be solved by a precise driving situation indicator is evaluating new vehicles during test drives. After a short introduction to a linear lateral vehicle model, an analytical approach for an online calculation of different driving conditions (i.e., stability, understeering, oversteering, and neutralsteering) is given. A characteristic velocity stability indicator is defined, which allows online computation of the present driving condition. Results are then checked against real measurements of a test vehicle. 相似文献
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This paper presents a new class of models for predicting air traffic delays. The proposed models consider both temporal and spatial (that is, network) delay states as explanatory variables, and use Random Forest algorithms to predict departure delays 2–24 h in the future. In addition to local delay variables that describe the arrival or departure delay states of the most influential airports and links (origin–destination pairs) in the network, new network delay variables that characterize the global delay state of the entire National Airspace System at the time of prediction are proposed. The paper analyzes the performance of the proposed prediction models in both classifying delays as above or below a certain threshold, as well as predicting delay values. The models are trained and validated on operational data from 2007 and 2008, and are evaluated using the 100 most-delayed links in the system. The results show that for a 2-h forecast horizon, the average test error over these 100 links is 19% when classifying delays as above or below 60 min. Similarly, the average over these 100 links of the median test error is found to be 21 min when predicting departure delays for a 2-h forecast horizon. The effects of changes in the classification threshold and forecast horizon on prediction performance are studied. 相似文献
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The need of accurate forecasts of air passenger numbers to assist managerial decision making for both short and long terms is well recognized and a central problem on both short and long term forecasting is how to handle future trend. The aim of this paper is to develop a demand trend change early warning forecast model (EWFM) for the city of São Paulo multi-airport system (SPMARs). For SPMARs the EWFM is based on the combination of leading indicators and alarms against possible occurrence of changes on trend component of the monthly number of domestic air passengers. A topdown induction procedure is employed to identify leading indicators to provide an interpretable prediction procedure to support the development of scenarios for future demand trend. Results show that changes on such demand trend are mostly associated to changes on the economic activity and six different scenarios were built combining the identified leading indicators. The EWFM was employed to assist managerial decision making for both short and long terms in order to evaluate different alternatives to prevent congestion delay occurrences and to support infrastructure planning. 相似文献
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