مهندسی عمران شریف (May 2022)
INVESTIGATION OF AREAS AFFECTED BY VERTICAL CONCAVE CORNERS DURING VERY DEEP EXCAVATIONS AND DETERMINATION OF THE PLAIN STRAIN RATIO
Abstract
The mechanism of deformation in very deep excavation is more complex than in shallow excavations. The deformation of the excavation near the corners is lower and a three-dimensional effect can be considered in the design in order to optimize very deep excavations. On the other hand, in practical projects, three-dimensional modeling is avoided and the plain strain models ordinary has been used which will increase the project costs. It must also be ensured that the assumption of a plain strain governs the problem. This study examines the results of monitoring a very deep excavation to a depth of 60 meters which has been stabilized by the anchorage method, validates a three-dimensional model, and considers the vertical concave corner effect in three-dimensional models including factors such as the depth and length of the excavation. Also, the Plain Strain Ratio (PSR) in this excavation is evaluated in accordance with parametric studies. The lowest value of the PSR occurred at a distance of 5 m from the corner and was equal to 0.45. By maintaining the maximum deformation, the length of the anchors was designed first without considering the three-dimensional effect; in another case, the effect of the corners was considered and the volumes were compared. The results showed that if the corner effect was included in the design of the stabilization method, about 21% to 55% of the total length of the anchors would be saved, being dependent on the excavation depth. The minimum and maximum values of the plain strain ratio in the corner and middle of the excavation are the same in all dimensions and are equal to 0.75 to 1. Due to the equality of the dimensions of the excavation (length and height), none of them has an effect on the range of the plain strain ratio values.
Keywords
