Study On The Adaptability Of Block-Rock-Embankment In Permafrost Regions

As far as roadway in permafrost regions is concerned, the stability is determined by subgrade, the stability of subgrade is determined by permafrost, and the key problem to permafrost is thaw settlement. As an effective solution to protect the underlying permafrost and prevent the roadway damages, Block-rock-embankment (BRE) achieves the cooling effect of the foundation and eliminates the thaw settlement by adjusting the convective heat transfer. Due to the advantages of obvious cooling effects, relatively small construction difficulties, easy sampling, and environmentally friendly, the Block-rock-embankment has been widely used in Qinghai-Tibet railway, Qinghai-Tibet highway, Ching-Hong road, and will be further promoted to other roadways in the future. Therefore, it would be very important and meaningful to study on the application evaluation of BRE in permafrost regions. The adaptability of Block-rock-embankment in permafrost regions has been selected as the object of this study. On the basis of systematically understanding the study on cooling mechanisms, cooling characteristics, cooling effects of BRE at home and abroad, we analyze the factors affecting the adaptability of BRE; build the integrated indicator system of the adaptability of BRE in permafrost regions based on the theory of evaluation index system. Finally, the mathematical model of evaluation is established by catastrophe progression method and BP neural network method, and verified by practical engineering projects. The main achievements include the following parts:1﹑By analyzing the research literature results about the BRE in the field of indoor and outdoor experiment, numerical simulation calculation,etc at home and abroad, The study achievements of BRE in permafrost has been summarized and refined to lay foundation for the quantitative evaluation study of adaptability of BRE in permafrost regions.2﹑The factors affecting the adaptability of BRE are summarized and analyzed by the classification of external climate conditions, frozen soils internal factors and subgrade characteristics. External climate conditions are incentives and motivations to influence the applicable condition of BRE; frozen soils internal factors are fundamental mechanisms directly affecting the transmission of temperature and moisture fields in roadbeds; subgrade characteristics is the only manual adjustment factors.3﹑Based on the theory of evaluation index system, evaluation indexes of12which impact significantly on the adaptability of BRE and function clearly are extracted from the factors affecting the adaptability of BRE. Then, the integrated indicator system of the adaptability of BRE in permafrost regions is set up according to definite hierarchical relationships between factors, which consists of three levels:object hierarchy, rule hierarchy and index hierarchy.4﹑According to the correlations among indicators, The mathematical model of evaluation is established by catastrophe progression method. Practical engineering projects of28are selected to verify the rationality and practicability of the model.5、The integrated assessment model set up by BP neural network method is selected to validate the evaluation results. It is concluded that, after training and learning, the adaptability of BRE can be evaluated and predicted more accurately.