Upper-bound Limit Analysis On Seismic Stability Of Waterfront Retaining Wall Under Tsunami Effect

When subjected to the combined action of tsunami and earthquake,the waterfront retaining wall is prone to passive damage,threatening the safety of life and property of the people behind the wall.At present,most of the research on the stability of waterfront retaining wall is based on the limit equilibrium theory.Therefore,when analyzing its stability,it is necessary to determine the magnitude and distribution of seismic earth pressure,and then derive the expression of seismic acceleration coefficient through the mechanical balance equation and moment balance equation of the wall.Due to the particularity of geological conditions in coastal areas,the coexistence of water and soil should be considered when solving seismic earth pressure.At this time,the solution process will become extremely cumbersome,and its location and distribution still have no clear solution.At the same time,the limit equilibrium theory assumes that the retaining wall is a non-gravity thin plate,so the seismic earth pressure based on the static equilibrium condition will ignore the displacement mode of the retaining wall.The upper bound theory of limit analysis is different from the limit equilibrium theory.In this method,the retaining wall and the soil wedge behind the wall are regarded as a complete wall-soil system,and the stability of the retaining wall is solved by establishing the velocity allowable field,so as to avoid solving the magnitude and distribution of seismic earth pressure.Although this method has been widely used in the study of the stability of the waterfront retaining wall,the theoretical study of the stability of the waterfront retaining wall under the combined action of tsunami and earthquake is still lacking.The specific contents of this paper are as follows :(1)Based on the upper bound theory of limit analysis,the wall-soil system and the velocity allowable field of the sliding of the waterfront retaining wall and the overall sliding of the soil wedge in the failure zone are established,and the expression of the seismic acceleration coefficient of the waterfront retaining wall under the pure sliding failure mode is derived.(2)The soil wedge is divided into numerous rigid soil slices parallel to the rupture surface by the oblique slice method.The wall-soil system and the velocity allowable field of the retaining wall rotating around the wall heel and the soil wedge sliding behind the wall are established.The expression of the seismic acceleration coefficient of the waterfront retaining wall under the pure rotation failure mode is derived.(3)The optimal solution is obtained by controlling the change of fracture surface angle.The influence of various parameters(sea level water level height,groundwater level height,wave height,etc.)on the ultimate fracture angle and seismic yield acceleration coefficient of backfill soil is analyzed under the pure sliding and pure rotation failure modes of waterfront retaining wall.Compared with the traditional limit equilibrium theory,the effectiveness of the proposed method is verified.