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In-situ Test Study And Numerical Analysis On Retaining And Protection Of Foundation Excavations

Posted on:2007-01-29Degree:DoctorType:Dissertation
Country:ChinaCandidate:J J WangFull Text:PDF
GTID:1102360185479389Subject:Geotechnical engineering
Abstract/Summary:PDF Full Text Request
The present dissertation proposes the FLAC numerical analysis method for design of the retaining and protection of foundation excavations with an aim to solve the existing problems: the displacement calculation of soil nailing wall, calculating model of double-row-piles, and design of pile-anchor considering the top beam action. Furthermore, it verifies the calculated results through in-situ tests carried in the deep foundation pit project of Henan Arts Centre-Grand Theatre as follows: (a) 18 test sites of soil nailing wall and 20 test sites of retaining pile are tested by electronic tachometer total station and theodolite in order to verify the calculated displacement of soil nailing wall and retaining pile; (b) 5 test sites for deep displacement of pile are tested by dipcompass with an aim to validate the calculated displacement of piles; (c) 110 bar gauges embedded in pile and 18 bar gauges embedded in top beam are tested by vibrating frequency receiver to substantiate the calculated internal force of pile and top beam. The whole process from the design of retaining and protection project to the completion of foundation construction combined with the overall in-situ monitor lasted for 12 months. As a result, more than 20,000 effective test data are collected. They are valuable for testifying to the reliability of numerical analysis method for calculation and for the research on stress state of retaining and protection structures. Through in-situ test and numerical analysis, numerical calculated method of soil nailing wall, double-row piles, pile and anchor retaining structure, and cooperation between pile in rows and top beam are studied systematically. The main conclusions and innovative results are listed as follows:1. The contrastive analysis of the calculated results got by in-situ tests and methods proposed by codes proves that FLAC numerical calculated method which produces reliable results is feasible in the designing of soil nailing wall. (1) The calculated value of the displacement of soil nailing wall is very close to the in-situ test data. The shape and rule of soil deformation tally with the research results described in documents: (a) the maximum soil deformation appears in the middle of soil nailing wall, (b) the contour line of deformation takes the shape of arc. (2) The tensile force of per soil nailing and the distributing shape of soil nailing force can be calculated. The calculated tensile force of soil nailing by FLAC numerical calculated method is smaller than that calculated by codes method. Calculation shows that the maximum tensile force of soil nailing appears in sliding plane, and the distributing shape of tensile force agrees with corresponding theoretical analysis. (3 ) The strength reduction method based on FLAC can be adopted to analyze the stability of soil nailing wall, calculate the safety factor, and predict the sliding plane position when the wall is ruined. The safety factors got by such method and by simplified finite slice method are quite similar with the max D-value below 10 percent.2, The contrastive analysis of the calculated results got by in-situ tests and conventional methods proves that FLAC numerical calculated method which produces more rational results is feasible in the designing of double-row piles retaining. (1) The "soil-structure" model adopted by numerical method avoids the hypothesis of soil pressure distribution raised by conventional method. Action of beam between front row pile and back-row pile makes the stress state of double-row piles different from that of cantilever pile. The stress state of front row pile is equivalent to adding rigid supporting to the pile top, and that of back row pile to adding pull-back bar to the pile top. The alikeness between the stress shape of calculated results and that of in-situ test data indicates that calculated model of numerical method can represent the real stress state of double-row piles, and...
Keywords/Search Tags:Foundation excavations, Retaining and protection design, In-situ test, Numerical analysis, Cooperation effective, Fast Lagrangian Analysis of Continua
PDF Full Text Request
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