TY - RPRT

T1 - Investigation on the Effect of Drained Strength when Designing Sheet Pile Walls

AU - Iversen, Kirsten Malte

AU - Nielsen, Benjaminn Nordahl

AU - Augustesen, Anders Hust

PY - 2010

Y1 - 2010

N2 - Long sheet pile walls are constructed in the cities as an integrated part of deep excavations for e.g. parking lots, pumping stations, reservoirs, and cut and cover tunnels. To minimise costs, the strength of the soil needs to be determined in the best possible way. The drained strength of clay expressed by c and ϕ is often estimated as c 10% = 10%・cu, and found by estimations based on the soil describtion, respectively. However, due to possible slicken slides and tension cracks, c = 0 is used on the back side of the sheet pile wall. This reduces the strength significantly. A parametric study is made on the effective cohesion to investigate the influence of c when designing sheet pile walls. Aalborg Clay is used as a case material. The parametric study is made in both a commercial finite element program and by use of Brinch Hansen’s earth pressure theory. In both studies, the analyses are made based on soil pressures only. The finite element analyses show that the safety factors increase with increasing cohesion. The safety factor is defined as the ratio of the surface load applied on the back side to the surface load applied at failure. Brinch Hansen’s earth pressure theory indicates that the height, anchor force, and the maximum bending moment in the wall can be lowered significantly when the effective cohesion is increased above zero. However, as the cohesion increases, the drop in the moment levels off, which implies that the benefit obtained from investigations increasing the cohesion more than c10% is small.

AB - Long sheet pile walls are constructed in the cities as an integrated part of deep excavations for e.g. parking lots, pumping stations, reservoirs, and cut and cover tunnels. To minimise costs, the strength of the soil needs to be determined in the best possible way. The drained strength of clay expressed by c and ϕ is often estimated as c 10% = 10%・cu, and found by estimations based on the soil describtion, respectively. However, due to possible slicken slides and tension cracks, c = 0 is used on the back side of the sheet pile wall. This reduces the strength significantly. A parametric study is made on the effective cohesion to investigate the influence of c when designing sheet pile walls. Aalborg Clay is used as a case material. The parametric study is made in both a commercial finite element program and by use of Brinch Hansen’s earth pressure theory. In both studies, the analyses are made based on soil pressures only. The finite element analyses show that the safety factors increase with increasing cohesion. The safety factor is defined as the ratio of the surface load applied on the back side to the surface load applied at failure. Brinch Hansen’s earth pressure theory indicates that the height, anchor force, and the maximum bending moment in the wall can be lowered significantly when the effective cohesion is increased above zero. However, as the cohesion increases, the drop in the moment levels off, which implies that the benefit obtained from investigations increasing the cohesion more than c10% is small.

KW - Sheet Pile Walls

KW - Soil Strength

KW - Clay

KW - Cohesion

KW - Numerical Model

KW - Bending Moment

KW - PLAXIS

KW - Sheet Pile Walls

KW - Clay

KW - Numerical Model

KW - Bending Moment

KW - Cohesion

KW - Soil Strength

M3 - Report

T3 - DCE Technical reports

BT - Investigation on the Effect of Drained Strength when Designing Sheet Pile Walls

PB - Department of Civil Engineering, Aalborg University

CY - Aalborg

ER -