The behavior of secant pile wall embedded within soil by numerical analysis

Deep excavation projects in areas with high groundwater levels, such as industrial zones with large, heavy structures, present significant challenges. Secant piling techniques offer an effective solution for these conditions. These retaining walls are constructed by overlapping reinforced concrete and plain concrete piles to form a continuous barrier against soil and water ingress. This research investigates the effectiveness of secant pile walls as a deep excavation support system, focusing on the impact of various parameters on ground movement, analyzed using the DeepEX program. The case study centers on the Al Dawoodi/Al Mansur District in Baghdad, Iraq. Key factors examined include excavation depth, water level fluctuations, pile diameter, wall stiffness, soil properties, and the bonding between piles. The results revealed that lowering the groundwater level decreases the total lateral earth pressure while enhancing lateral resistance. For a constant excavation depth of 12.85 m, the total active stress at a depth of 9 m decreases as the water table level drops. When the water table is at -1.8 m, the total active stress is 92.952 kN/m²; at -3.5 m, it decreases to 87.837 kN/m²; and at -5.5 m, it further reduces to 82.016 kN/m². Additionally, deeper excavations result in greater horizontal displacement at the top of the wall. Increasing the pile diameter from 0.6 m to 1.2 m reduces lateral displacement from 0.503 m to 0.467 m but increases the bending moments from 832.56 kN.m/m to 1430.22 kN.m/m within the secant pile wall. Furthermore, the interlock ratio between the piles significantly influences wall performance. As this ratio increases, the bending moment also rises, with moment resistance increasing from 1134.72 kN.m/m to 1209.94 kN.m/m when the overlap distance grows from 5% to 30% of the pile diameter. The analysis also demonstrates that enhancing the strength of the secondary piles within the wall leads to higher bending moments, improving the wall's stability against excavation-induced stresses.