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.

Diaphragm wall-soil-cap interaction in rectangular-closed-diaphragm-wall bridge foundations

Rectangular-closed-diaphragm-wall foundation is a new type of bridge foundation.Diaphragm wallsoil-cap interaction was studied using a model test.It was observed that the distribution of soil resistance under the cap is not homogeneous.The soil resistance in the corner under the cap is larger than that in the border;and that in the center is the smallest.The distribution of soil resistance under the cap will be more uniform,if the sectional area of soil core is enlarged within a certain range.Due to the existence of cap,there is a“weakening effect”in inner shaft resistance of the upper wall segments,and there is“enhancement effect”in the lower wall segments and in toe resistance.The load shearing percentage of soil resistance under the cap is 10%–20%.It is unreasonable to ignore the effects of the cap and the soil resistance under the cap in bearing capacity calculations.