Original scientific paper The distribution of stresses and strains during the portal section excavation for the right tube of the Sleme Tunnel is analysed by the Finite Element Method (FEM). Results of analyses obtained using 2D and 3D models have been compared to in-situ measurements of tunnel convergence and ground surface settlements. Multistage excavations with pipe roof support of the working face were modelled. The numerical models verified that for this particular case a sufficiently safe and cost-efficient construction technology was applied.Keywords: Finite Element Method; pipe roof; stress and strain analysis; tunnel excavation
Analiza stanja naprezanja i deformacija tijekom iskopa tunela SlemeIzvorni znanstveni članak Analizirano je stanja naprezanja i deformacija tijekom iskopa portalne dionice desne cijevi tunela "Sleme" primjenom metode konačnih elemenata. Napravljena je usporedba rezultata proračuna ravninskog (2D) i prostornog (3D) modela s rezultatima terenskih mjerenja konvergencija u tunelu i slijeganja površine terena. Modelirani su višefazni iskopi s ojačanjem čela cijevnim krovom. Proračunski model je pokazao da je u navedenom slučaju primijenjena dovoljno sigurna i ekonomična tehnologija iskopa.Ključne riječi: analiza stanja naprezanja i deformacija; cijevni krov; iskop tunela; metoda konačnih elemenata
This paper discusses the pullout capacity of spatial anchors in soil under applied vertical force. In field tests, the pullout forces were gradually increased and the ground surface displacements measured in two profiles perpendicular to each other. The laboratory and field tests were performed for several embedment depths and anchor diameter ratios in the same sand and under the same conditions. The anchor pulling was also laboratory‐tested so that the vertical anchor displacements were given and the corresponding force intensity measured. The finite element method was used for the pullout force computation in test cases. The relations between displacements and pullout forces obtained by the laboratory tests, field tests and numerical computations were statistically analysed. Owing to gradual convergence of pullout forces towards the limit value, the exponential function was adopted as an approximation curve. The two obtained constants of the function represent the significant mechanical characteristics. The first is limit pullout force and the second gives the total stiffness of the soil mechanical system.
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