Numerical study of design parameters influencing anchored diaphragm walls for deep excavation

Abstract

Using the Plaxis 2D v20 code, this paper presents numerical modeling of a large and deep excavation in layered soil supported by anchored diaphragm walls under unequal load to investigate the influence of several design parameters on the stability and safety of the supporting system, as well as their impacts on the nearby structures. The numerical model's results were compared to those of a case study of braced excavation in clays, and a close agreement was found. The soil profile is made up of multiple clay layers that are represented by the hardening soil model with a small strain (HSsmall). The diaphragm walls are represented as plates, while the anchor rods are represented as node-to-node connections. The studied parameters include the inclination angle of anchors, number of ground anchors, groundwater level, diaphragm wall thickness, surface load distance from the excavation edges, and various wall-embedded depths to the excavation depth ratios. The analysis's results were examined and discussed in terms of maximum lateral and vertical displacements, bending moments in the wall supporting system, vertical displacement of the ground surface behind both sides of the excavation, and the heave developed at the bottom of the excavation. The analysis's results show that as $D_{b} /D_{{{\text{ex}}}}$ increased from 0.3 to 0.5, $u_{xw}$ and $M$ are reduced by about 10.5 and 8.1%. However, when it increased more to 0.7, their values remained unchanged. Furthermore, $t_{{{\text{wall}}}}$ within the range of (0.8–1.0) m corresponds to $t_{{{\text{wall}}}} /D_{{{\text{ex}}}}$ = 0.04–0.05, and $D_{b} /D_{{{\text{ex}}}}$ = 0.7 can be used as a non-dimensional design parameter that satisfies all design factors for deep excavation design and similar geotechnical problems.