The undrained bearing capacity of skirted strip footing on soft clay

FANG Zhou;ZHAO Zhifeng;MA Qing;College of Civil Engineering,Nanjing Forestry University;

skirted strip footing;;bearing capacity;;numerical computation;;theoretical analysis;;soft clay

The bearing capacity of footing is the important issue of soil mechanics. According to classic bearing capacity theory,the increase in footing depth can improve the bearing capacity of soil,but also cause the adverse effect on the increase self-weight of footing. This contradiction is overcome by use of skirted footing. At present,the studies on skirted footing mainly focus on the circular shape,and the bearing capacity of other shape footings is lack of discussion.The skirted strip footing on the cohesive soil is chosen as study objective,and the numerical simulation with different parameters is used to analyze the deformation behavior of footing when the subsoil collapses. Afterwards,the formulas to calculate the undrained bearing capacity of skirted strip footing are put forward by the theory deduction.The results of numerical computation illustrate that the failure mechanism of skirted strip footing is similar to the embedded footing with the same depth,and the undrained bearing capacity is increased obviously when compared to footing with the same width but without skirts. Moreover,the bearing capacity is increased with the relative length of skirts( d/b) when other parameters remain unchanged. Based on the failure mechanism of skirted strip footing on the clay,the Meyerhof bearing capacity theory is applied to calculate the bearing capacity of skirted footing because the depth influence on the bearing capacity is considered in this theory. When the subsoil is soft clay,the internal friction angel is zero under the undrained condition. Therefore,the theoretical analysis of bearing capacity can be simplified,and the formula for calculating the undrained capacity of skirted strip footing is deduced. In order to verify the validity of deduced formulas,the formula computation results are compared with the results obtained by numerical simulation and empirical formula. The empirical formula was put forward by the foreign scholars who took the influence of depth into account. The comparison result indicates that the bearing capacity of theoretical calculation in the study is close to the numerical simulation. However,the empirical formulas underestimate the bearing capacity to some extent. Therefore,the deduced formulas can be applied to calculate the undrained bearing capacity of skirted strip footing on the soft clay.