Research On The Optimization Design Of Retaining And Protecting Engineering For Foundation Excavation Based On Genetic Algorithm

The scheme design and detail design are the two levels of the optimization design of the retaining and protecting engineering for foundation excavation. They are associated with each other and can't be separated. So to combine two of them to the uniform analysis is the basic idea of the optimization design of the retaining and protecting engineering. It is also called the collaborative optimization design method. But, there are two difficulties in the method. One is the existing of numerously discrete variables, high dimensionality and great solution spaces, which may lead to the explosion of combination. The other is that the relationship between optimization object and the design variables is often very complex, and can hardly be expressed by plaint equation. Considering these two difficulties, people often separate the two levels of the design of the retaining and protecting engineering for simplicity in practice. Therefore, there exist lots of vestiges of artificial interference in the optimization design of the retaining and protecting engineering. So, two problems should be solved in the design of the retaining and protecting engineering. One is to construct the analysis model of optimization design of the retaining and protecting engineering based on the idea of collaborative optimization design. The other is to find a optimization method to get "the best solution" or "quasi-optimal solution" using the model constructed before. Therefore, there are important theoretic and practical significances to solve these problems.All existed supporting structures and their corresponding optimization design methods are introduced first in this paper. The analysis of the system structure and the factors that may influence the retaining and protecting system for foundation pit is given by using systematic engineering method. The method of the optimization design of retaining and protecting engineering is outlined. It should follow the procedure described in the systematic engineering, combine the characteristics of retaining and protecting engineering and apply the optimization algorithm to arrange the design work. The systematic optimization design thought of the retaining and protecting engineering, "natural selection, system analysis, hierarchical evaluation, collaborative optimization", is presented. The procedure, principles and methods of the optimization design of the retaining and protecting system are addressed as well.The analysis model of the collaborative optimization design of the retaining and protecting system for foundation pit based on searching is proposed. The model describes the scheme design and detail structure design as two designing questions in different spaces and different levels. Scheme design belongs to scheme space, and the detail design belongs to detail structure space. These two spaces are separated. But they are inter-influenced, inter-related at the same time. Thus, the optimization design of the retaining and protecting system is the procedure of alternative searching between these two spaces. This model depicts the procedure of the collaborated optimization design of the scheme and details. It represents the thought that scheme design has instructive meaning to detail design and the detail structure design can also give some feedback to scheme design to modify it. The mathematical model of the optimization design of each level in retaining and protecting system is also given.The novel optimization algorithm, genetic algorithm popular these years, is introduced. Genetic algorithm has the characteristics of multi-point searching, parallel computing and self-adaptive global optimization. So it is very suitable for the solution of complex engineering problems, which often have numerous variables, high dimension, highly nonlinear optimization objects, and the great solution spaces. The co-evolution model and algorithm of the collaborated optimization design for the scheme design and detail design is constructed based on the simple genetic algorithm. The results of the experim...