Solution to critical suction pressure of penetrating suction caissons into clay using limit analysis: Fid-Bau Portal

Solution to critical suction pressure of penetrating suction caissons into clay using limit analysis

Wu, Yuqi / Zhang, Yu / Li, Dayong

Abstract The critical suction pressure will lead to the difference in equivalent overburdens at the skirt-tip level between outside and inside the caisson exceeds Nc ^rs u (Nc ^r is the local reverse bearing capacity factor, and s u is the undrained shear strength of clay at the skirt-tip), which may induce the local reverse bearing capacity failure of soil near the skirt-tip. As a result, soil flows into the caisson cavity, making soil plug heave higher that prevents the caisson from penetrating to its desired depth. This paper is the first to apply the limit analysis to obtain a theoretical study on determining the critical suction pressure based on the local reverse failure mechanism near the skirt-tip. This study is also the first to consider the effects of adhesion factors along the inside (α i) and outside (α o) of the skirt wall on the local reverse bearing capacity failure mechanism reflecting that Nc ^r includes α i and α o. It is shown that Nc ^r ranges from 5.14 (α i=α o=0) to 8.28 (α i=α o=1), and the values of α o and α i are all between 0 and 1. In addition, the critical penetration depth can be determined under the condition that the critical suction pressure equals the required suction pressure. And, the proposed method of calculating the critical penetration depth is testified to be in good agreement with the experimental results.