| With the continuous improvement of China’s railway construction level,at the end of the "13th Five-Year Plan",China’s railway development has made great progress,and the railway development in the southwest region is also very rapid,gradually changing the original "small,remote,low" situation.However,there is a large area of dry-hot valleys with arid climate,barren soil and sparse vegetation in southwest of China,and the environment is extremely harsh.The construction of the railway has produced a lot of adverse effects on the ecological environment in the fragile area of the dry-hot valley,and there are many natural disasters in this area,which poses a great threat to the smooth operation of the railway.Therefore,during the construction of the railway,it is necessary to ensure the safety of later operation and the integrity of the ecological environment in the fragile areas of dry-hot valleys along the line.The green protection of subgrade slope has become the best way to solve this problem.However,the current studies on slope protection mainly focus on the reasonable allocation of slope protection vegetation and the construction of universal slope protection evaluation system,and there is no set of evaluation system suitable for the green protection effect of subgrade slope in the special area of dry-hot valley.Therefore,it is of great practical significance to analyze and evaluate the effect of green protection of subgrade slope in this region in combination with the regional characteristics of the fragile area of dry-hot valley,for ensuring the stability of subgrade and restoring the ecological environment of the fragile area of dry-hot valley along the railway.Taking the fragile area of dry-hot valley in Southwest China as the research background,this thesis analyzes the action mechanism of green protection engineering of subgrade slope and considers the environmental characteristics of the fragile area of dry-hot valley,and constructs a hierarchical structure system with multi-level and multi-angle for evaluating the green protection effect of railway subgrade slope in the fragile area of dry-hot valley.At the same time,based on the cloud theory,the evaluation model of green protection effect of railway subgrade slope in the fragile area of dry-hot valley was established by using the MCGC method and two-dimensional cloud model,and the feasibility of the model was verified in the actual project of Chengdu-Kunming Railway.Firstly,through the in-depth analysis of the landform,soil,vegetation,hydrology and climate in the fragile area of the dry-hot valley,and the detailed analysis of the protection effect of the green slope protection project on the subgrade and the environmental restoration effect.Then starting from two aspects of structure and function,and refined to five perspectives: soil matrix quality,vegetation community quality,protection function,mechanical function,and landscape function,the factors affecting the green protection effect of subgrade slopes are screened,including 5 first-level indexes and 27 second-level indexes,a multi-level and multi-angle railway subgrade slope green protection effect evaluation hierarchical structure system was constructed.Secondly,according to the uniqueness of the dry-hot valley and the different evaluation index attributes,the improved group analytic hierarchy process method(IGAHP)is used to calculate the subjective weight of evaluation index,and the projection pursuit model optimized by genetic algorithm is used to calculate the objective weight of the evaluation index based on the data of index,and finally through the game theory,the subjective and objective weights are combined to determine the comprehensive weight of index,so that the determination of the weight not only considers the conflict and difference between the subjective and objective weights,but also highlights the characteristics of the fragile areas of dry-hot valley,and the weight distribution is more reasonable.Finally,the membership cloud gravity center(MCGC)method was used to conduct parallel aggregation and vertical upward aggregation of the eigenvalues of the second-level indexes to obtain the eigenvalues of the first-level indexes,and MATLAB software was used to draw the subordinate cloud map to analyze the influence of the first-level indexes on the structure and function.On this basis,the structure and function are taken as the two basic variables of the two-dimensional cloud model,and the eigenvalues of the structure and function are calculated to form a two-dimensional comprehensive effect cloud,and the effect of green protection of subgrade slopes is evaluated.At the same time,with the help of forward cloud generator of MATLAB software to draw two-dimensional cloud preliminary reflect subgrade slope green protection level of the fragile areas of dry-hot valley.In view of the similarity and spatial error of two-dimensional cloud map,the nearness degree is introduced to calculate the closeness degree between two-dimensional comprehensive effect cloud and standard effect cloud,and the evaluation result is determined accurately.Taking the green protection project of a section of subgrade slope in the Mipan section of Chengdu-Kunming Railway as the research object,the protection effect is analyzed by using the established evaluation system and evaluation model.The results show that the green protection effect of the subgrade slope of this section in the Mipan section of ChengduKunming Railway is good,which is basically consistent with the actual situation of the project,which verifies the applicability of the system and model constructed in this thesis.At the same time,it also shows that the green protection of the slope has a very positive effect on protecting the stability of the subgrade and restoring the ecological environment in the fragile area of the dry-hot valley along the line.The research in this thesis has certain reference value for the government to monitor the quality of the green protection project of subgrade slope. |
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