Study And Application On Optimization Design Of Retaining Walls Of Deep Excavation

Deepfoundation pit in building is a systematic engineering with a variety ofcomplicated factors influencing each other. And the choice and design of deepfoundation supporting project affect directly the stability and economy of thefoundation pit, because even a small negligence may cause the instability and damagethe foundation pit and hence increase the cost of the project. Therefore, the niche-targeting selection and optimization of the supporting structure of foundation pit arevital for the smooth implementation of the deep foundation pit engineering.Combining the theories with practice of deep foundation pit engineering, thispaper summarizes several common types of foundation pit supporting, their respectiveapplicable conditions, merits and demerits, and the influencing factors that affect deepfoundation supporting project. Based on deep foundation pit design theory and fuzzymulti-objective decision making theory, this paper establishes a relatively systematicselection system for deep foundation supporting project by using FuzzyComprehensive Evaluation and Analytic Hierarchy Process, taking safety andreliability, low cost, short construction period, small environment impact, andconvenient construction as the optimization objectives. The paper also analyzes thecomputational model of deep foundation pit supporting design and surveys on theoptimization methods, including pile diameter, pile spacing, built-in depth of the pile,and the anchor position of anchor rod.By using Fuzzy Comprehensive Evaluation and Analytic Hierarchy Process andalso combining with engineering examples, the paper selects preferably among foursupporting projects: underground diaphragm wall, pile and anchor rod, the upper soilnail wall plus pile plus anchor rod, pile and inner support. The supporting project withhighest comprehensive evaluation value, that is the upper soil nail wall plus pile plusanchor rod, is selected finally.The foundation pit supporting project is established through the detailed designof optimized supporting project. And Plaxis finite element software was used tomodel the deep foundation pit. Besides, the paper also analyzes the stress and horizontal displacement of the engineering, compares the horizontal displacement ofenvelop enclosure among different pile diameters, pile spacings, built-in depths, andthe anchor positions, and then chooses a more reasonable supporting parameter anddetermines a new supporting project. Finally, this paper analyzes the rationality of theoptimized supporting project. The result reveals that compared with the originalsupporting project, the optimized supporting project reduces the cost of theengineering under the premise of stability.