Numerical modeling of current-induced scour around multi-wall foundation using large-eddy simulation

Scouring is one of the primary triggers of failure for bridges across rivers or seas.However,research concerning the scour mechanism of multi-wall foundations(MWFs)remains scarce,hindering the further application of MWFs.In this study,for the first time,the scouring effect caused by unidirectional flow around MWFs was examined numerically using FLOW-3D involving a large-eddy simulation.Initially,the applicability of the scouring model and input parameters was validated using a case study based on published measured data.Subsequently,the scouring effects of four MWFs with different wall arrangements and inflow angles,including the flow field analysis and scour pit and depth,were investigated thoroughly.It was found that the maximum scour depth of MWFs with an inflow angle of 0°was smaller than that of those with an inflow angle of 45°,regardless of the wall arrangement.Meanwhile,changing the inflow angle significantly affects the scour characteristics of MWFs arranged in parallel.In practical engineering,MWFs arranged in parallel are preferred considering the need for scouring resistance.However,a comparative analysis should be performed to consider comprehensively whether to adopt the form of a round wall arrangement when the inflow angle is not 0°or the inflow direction is changeable.

The behavior of a rectangular closed diaphragm wall when used as a bridge foundation

The rectangular closed diaphragm(RCD)wall is a new type of bridge foundation.Compared to barrette foundation,measuring the performance of RCD walls is relatively complicated because of their incorporation of a soil core.Using the FLAC3D software,this paper investigates the deformation properties,soil resistance and skin friction of a laterally loaded RCD wall as well as the settlement,axial force and load-sharing ratio of a vertically loaded RCD wall.Special attention is given to the analysis of factors that influence the performance of the soil core.It was found that under lateral loading,the RCD wall behaves as an end-bearing friction wall during the entire loading process.The relative displacement between the wall body and the soil core primarily occurs below the rotation point,and the horizontal displacement of the soil core is greater than that of the wall body.Under vertical loading,the degree of inner skin friction around the bottom of the soil core and the proportion of the loading supported by the soil core increase with increased cross-section size.The wall depth is directly proportional to the loading supported by the outer skin friction and the tip resistance of the wall body and is inversely proportional to the loading borne by the soil core.

Soil arching effect of Lattice-Shaped Diaphragm Wall as bridge foundation

As a new type of bridge foundation, Lattice-Shaped Diaphragm Wall （hereinafter for LSDW） is highly concerned in relevant construction area but its research is far from achievement. Based on PFC2D, the soil arching effect of LSDWs is studied thoroughly in this paper and the special attention is given to its influencing factors. It turns out to be that a differential wall-soil settlement can be found at the lower location of soil core of an LSDW which is one of the trigger factors of soil arching; meanwhile, the differential settlement degree can reflect the exertion degree of soil arching; the shape of soil arching is basically a hemisphere which can be explained by the theory proposed by Hewlett and Randolph; normally, the chamber number is a negative factor for the development of soil arching; the soil arching effect is significantly influenced by the distance of two adjacent wall elements and the foundation depth, and a relatively large or small value of these factors is disadvantageous to the exertion of soil arching; in addition, the soil arching effect increase with the growth of stiffness and friction coefficient of particles and the friction coefficient of particles has insignificant influence on the development of soil arching effect compared with particle stiffness.

Surficial stability analysis of soil slope under seepage based on a novel failure mode

Normally,the edge effects of surficial landslides are not considered in the infinite slope method for surficial stability analysis of soil slopes.In this study,the limit stress state and discrimination equation of an infinite slope under saturated seepage flow were analyzed based on the Mohr-Coulomb strength criterion.Therefore,a novel failure mode involving three sliding zones(upper tension zone,middle shear sliding zone,and lower compression zone)was proposed.Accordingly,based on the limit equilibrium analysis,a semi-analytical framework considering the edge effect for the surficial stability of a soil slope under downslope seepage was established.Subsequently,the new failure mode was verified via a numerical finite element analysis based on the reduced strength theory with ABAQUS and some simplified methods using SLIDE software.The results obtained by the new failure mode agree well with those obtained by the numerical analysis and traditional simplified methods,and can be efficiently used to assess the surficial stability of soil slopes under rainwater seepage.Finally,an evaluation of the infinite slope method was performed using the semi-analytical method proposed in this study.The results show that the infinite slope tends to be conservative because the edge effect is neglected,particularly when the ratio of surficial slope length to depth is relatively small.