Study Of Safety Evaluation Method Of The Surrounding Rocks Of Underground Cavern Based On Safety Coefficient Method

One of the most important study contents in geotechnical engineering is stabilityevaluation of the surrounding rocks of underground cavern is, making correct evaluation resultsis the key to the success of the whole engineering. At present, the range of stability ofsurrounding rocks can be defined by the displacement change or the plastic zone, itslimitations is that the surrounding rocks in what circumstances will be destroyed is unclear, soit can't calculate the safety factor. Compared with other methods, safety coefficient methodbased on theoretical basis, expressed with clear physical expression and has the only analyticsolution, is more scientific and reasonable stability evaluation method. Thus, safetycoefficient method can develop a quantity standard for underground cavities rocks' stabilityanalysis, which can provide theoretical support and reference data for the structure design ofunderground cavern. In view of the above two aspects, this article takes soil slope and undergroundcavern for example and does the following main jobs:1. Present point safety coefficient as the safety evaluation method of the surroundingrock of underground cavern, compare different safety coefficient definition methods andanalyze the rationality. Study the basic theories of the surrounding rock stability analysis, andon that basis to derive the safety factor formulas based on the difference of yield criterionsuch as M-C,D-P,Strength Reduction Theory and Unified Strength Theory. Probe into theshortcomings of single axis strength safety coefficient, after that introduce the definitions ofmulti-axial intensity safety coefficient based on stress path method,failure distance methodand displacement sensitivity method.2. Compare the advantages and shortages of different methods with specific exampleanalysis. Using Finite Element Software ADINA expertly, and take loess tunnel for example,using ADINA to analyze the stability of slope and the failure mechanism of loess tunnel,explore the feasibility of the safety factor method in stability studies of slope and tunnel,which accords a new reference value for the stability analysis of geotechnical engineering.Finally,summarize the advantages and disadvantages of different methods as well as theresults rationality.3. Study of stability analysis of the surrounding rocks of underground cavities based on unified-strength safety coefficient method. This article writ the finite element programNFEM6based on the unified strength theory, which improves the defect that the program onlycan adopt a yield criterion, thus different materials can adopt different yield criterion, andextends convergence criterion of linear computation nonlinear computation to four. Finally,the stability analyses of the soil slope and loess tunnel are simulated by the program NFEM,furthermore the calculation results are compared and analyzed with the analysis results ofusing ADINA. Through verification and calculation the program has some special functions,it not only provides various choices of yield criterion, but also easy to modify for differentmodels' expression. Moreover, it can get more flexible output and make combined with somepractical drawing software through data exchange. This way, the calculation results will bebrought out with the form of image visual presentation.