Abstract

The construction monitoring of Ráckóczi square metro station of Budapest Metro Line 4 offered a great opportunity to back analyse the braced deep excavation in the building period. Building movements, strut forces and wall displacement measurements have been compared to numerical results derived by PLAXIS using HSsmall soil model. Considering the influence of small strain stiffness of plastic soils, good fit of the measured and calculated movements could be observed and the strut forces could be calculated reasonable. Curve characteristic of surface settlements was explored, as well. Analysis were carried out to observe influence of the following inputs on the numerical results: soil material model; consolidation effects, boundary conditions. A detailed evaluation is given about the results of parametric analysis.

The paper focuses on the numerical back analysis of the monitored deep excavation of II. János Pál pápa square of Budapest Metro Line 4. Inclinometric measurement of diaphragm wall deformations has been compared to numerical results derived by PLAXIS using HSsmall soil model. Considering the influence of small strain stiffness of plastic soils, good fit of measured and calculated deformations could be observed. Parametric analysis were carried out to observe influence of the following inputs on the numerical results: Construction time and sequence Consolidation effects Small strain stiffness parameters A detailed evaluation is given about the results of parametric analysis, considering the inherent errors of the inclinometric measurements, as well.

In this paper, the numerical back analyses of four, typical, monitored deep excavations completed in Budapest are presented. The typical excavation solution in Budapest city center, down to 15–18 m excavation depth, is a diaphragm wall embedded in the clay bedrock and supported by prestressed anchors embedded in the sedimentary soils above the clay. In these case studies this solution is analyzed with traditional Winkler type and more complex PLAXIS 2D and 3D finite element models. The focus of the study was to compare the measured wall deformations with the calculated ones derived by the listed methods. As the clay bedrock is a deterministic layer for the wall behavior, several different FEM models were prepared to analyze the appropriateness of the potential constitutive models for its proper characterization. As a conclusion, practical proposals were made for practitioners for future excavations.

Mély munkatérhatárolások témakörével foglalkozó doktori kutatási projektünk keretében Budapesten megvalósult munkagödrök mozgásmérési eredményeit rendszereztük és elemeztük. Vizsgálatunk eredményeit jelen publikációban ismertetjük. Bevezetésként összefoglaljuk a munkatárhatárolások deformációinak számítási lehetőségeit és összegezzük a nemzetközi szakirodalmak releváns, mozgásmérési tapasztalatait, ajánlásait. Bemutatjuk azt az adatbázist, amely az utóbbi 15 évben Budapesten, annak jellegzetes belvárosi talajkörnyezetében megvalósult 9 db mereven (támaszfödémes és/vagy csőtámaszos) vagy rugalmasan, talajhorgonyokkal megtámasztott mély munkatárhatárolás megvalósítása során mért deformációkat tartalmazza. Végezetül ismertetjük a faldeformációk és felszínsüllyedések a munkagödörmélység és megtámasztási mód függvényében azonosított tendenciáit és az azokból levonható következtetéseket.