Study On Optimization Of Quantities' Calculation Methods For Changeing Slop Into Terrace In The Hilly And Mountainous, Southwestern China

Farmland is rapidly eroded by the process of With the rapid development of social economy, urbanization. There is a balance between farmland protection and social demand. Our country have carried out various projects to increase farmland area including slope changing terrace. China is a densely population and fairly limited farmland, especially little slope farmland in mountainous area. The slope farmland area account for 1/3 of cultivated land, and most of them have water, soil and fertilizer leakage so that the yield of them are lower and water and soil losses are serious, which become mainly source of soil erosion and rivers' sediment. However, the ecological impact and the quantities' accuracy of changing slope into terrace are ignored when implementing this project. The design and quantities of changing slope into terrace are the most important elements to measure input-output ratio of this project, and also the main parameters to evaluate economic, ecological and social benefits. Therefore, changing slope changing terrace project has become a research focus in land-use scientific.The hilly and mountainous southwest in China have distributed widely, rugged topography, biological and landform multiplicity, abundant rainfall, large evaporation volume, enough heat, temperate, distinctive seasons, long frostless season which is suit for the growth of crops. There were unreasonable agriculture structure, simple and extensive land use types, lake of intensive management, closed thought, inconvenience traffic and information and lower land utilization rate so that this paper paid attention to changing slope into terrace project in the southwest hilly mountain region.It that calculating the amount of the engineering of changing mountain slops into terrace field is one of the important study contents on the engineering of terracing of sloping fields. Presently more and more methods are used, which can be divided into four type o the whole such as square grid method, disperse points, section method and formula method . These methods have their own strongpoint and shortcoming, but all of them are not suited for the hilly county in the southwest. Computational process of some of them is too complex, or the computation is inaccurate. Therefore it is necessary that the methods of the engineering of terracing of sloping fields which is suitable for the hilly county in the southwest are researched.A general view of the situation of farmland, the particularity of study area and the progress situation of changing slope into terrace project, so researches on optimum calculation method had an important practical significance and urgency.In this paper, using spot investigation, data collection and comparative analysis, a more convenient method to calculate quantities, which was suitable for the hilly area southwest of slope changing terrace project, was put forward based on design theory and empirical methods. Meanwhile, taking 12 types of design elements for example, conclusions were modified and proved to form a accurate calculation formula. At the end, A better calculation table was establish to be convenient for quantity numeration, specialist examination and bidding.At first, the existing methods of slope changing terrace works were compared to analyze their advantages, disadvantages, and the applicability. Then, we analyzed some theories and principles of changing slope into terrace to study the design and quantities' calculation methods. At finally, we drew the main following conclusions:(1) According to the quantity's calculation of changing slope into terrace in the southwest hilly mountain region, the existing method of middle Grid, discrete test, section and the formula were not practical due to calculation inaccurate, too complex and so on.(2) A calculation method of changing slope into terrace in the southwest hilly mountain region was derived by comparing and learning the benefits of all calculation methods. The results facilitated the calculation process of changing slope into terrace project, and the results also were more precise, enriching the research content and making useful explorations for promoting this project in the southwest hilly mountain region.(3) The difference of ridge construction in this project had influence on the formula which was drawing from the previous study. When the ridge was not set after the down slope, the final calculation steps were adjusted. This calculation method was more stringent.