Study On The Optimum Design Method Of Soil Nailing Retaining Structure

Soil nailing retaining structure is one of the important supporting forms which are applied for reinforcing foundation pit and slope. It has been generalized rapidly and applied widely in our country because of its characteristics of economy, reliability and convenient construction. But for that the people has not enough acquantanceship about the action mechanism of this technique, its design method is still staying at the empirical stage. Its characteristic of safety is always emphasized in the course of design, but the economical characteristic of it is neglected at the same time. So, in order to consider both of them, the optimum design method of this technique must be studied thoroughly. It has important theoretical and enginnering practical meaning.Based on studying the present status of relating research at home and abroad, firstly, a concept of distribution coefficient of the nail's maximum tense is advanced in this paper by analyzing the action mechanism of soil nailing retaining structure, and then the corresponding computing method is given out. Furthermore, by comparing the results which are achieved by using this method with the field test results, its reasonableness is proved. Then, combined with the limit equilibirum analysis method for the globe stablity of soil nailing retaining structure, the computation model for determining the reasonable length of soil nails is established. It lays a good foundation for the optimum design of soil-nailing. Thirdly, based on the thorough research on the influencing factor of design, a optimum design model in which the layer number of soil nails, the interval of soil nails, the inclination of soil nails and the length of soil nails are considered is constructed. Finally, simulated annealing algorithm and its monocase betterment strategy is introduced in .A new method of optimization design for soil-nailing is advanced by combining them with the method of geometric controlling parameters. And then the corresponding programs are developed in FORTRAN Language.The analysis of engineering cases show that the method of optimization design for soil nailing advanced in this paper is reliable and stable, and the optimal design schemes achived by this metod are safe enough and economic and reasonable. So, a new thought and method is supplied for the optimum design method of soil nailing retaining structure.