Research On Aseismic Mechanism And Design Calculation Method Of Gravity Wall Tensioned With Horizontally Flexible Reinforcements

Gravity retaining wall is a kind of slope retaining structure widely used in civil engineering,but its seismic performance often has certain deficiencies.Focusing on improving the seismic performance of traditional gravity wall,this paper applies a new type of retaining structure combined with gravity retaining wall and reinforced soil technology,namely gravity wall tensioned with horizontally flexible reinforcements,and establish a seismic design calculation method for such retaining walls in the fill slope project with plastic limit analysis method,limit equilibrium method and numerical simulation method on the basis of studying the mechanism of its aseismic mechanism.The main research results are as follows:(1)Revealing the aseismic mechanism of gravity wall tensioned with horizontally flexible reinforcements.On the one hand,the lacing has a restraining effect on the wall displacement during the earthquake,which can directly reduce the wall displacement;on the other hand,the lacing reinforcement has a reinforcing effect on the backfill of the wall,which can reduce the earth pressure on the wall and improve the overall stability of the wall.The combined effect of the lacing increases the yield acceleration of the wall and causes the retaining wall to be relatively less susceptible to damage during an earthquake.(2)Based on plastic limit analysis upper bound method and the pseudo-static method,the calculation formula of seismic active earth pressure of gravity wall tensioned with horizontally flexible reinforcements is derived for linear,logarithmic spiral and multi-block sliding modes.The engineering example analysis results show that the calculated results of the three theoretical methods are larger than the numerical simulation results;the calculation result of the logarithmic spiral surface sliding mode is about 6-20% higher than that of the multi-block sliding and plane sliding mode,so that the engineering design is relatively conservative.(3)Based on Newmark slider theory and plastic limit analysis upper bound method and considering the translation and rotation modes of the retaining wall,the calculation formula of the permanent displacement of the gravity wall tensioned with horizontally flexible reinforcements is derived.By means of reinforcement,the yield acceleration of the retaining wall during translation or rotation can be improved,thereby effectively reducing the permanent displacement of the wall.The example analysis shows that the horizontal displacement calculated by the theoretical method is slightly larger than the numerical simulation result,and the deviation is about 11%.(4)Using equivalent gravity method,retaining wall and fill are considered as one.Based on assumptions of the Fellenius method and simplifying Bishop method,the formula for calculating the factor of wall-slope overall stability is derived.For the factors of wall-slope overall stability,the numerical simulation results are similar to the simplified Bishop method,and both of them are larger than the Fellenius method.(5)The main factors,including backfill cohesion and internal friction angle,foundation cohesion and internal friction angle,geometric size of retaining wall,ultimate tension of geogrid,reinforcement spacing,top length of geogrid,seismic coefficient,etc,which affect the seismic active earth pressure,the yield acceleration coefficient and the overall stability of the wall-slope of the reinforced gravity wall are discussed.Sensitivity analysis of these factors was also carried out.Reducing the spacing of reinforcement can effectively improve the yield acceleration of the wall and increase the overall stability coefficient,but with the shortening of the length of the top rib,the overall stability coefficient decreases nonlinearly.The internal friction angle of fill is more sensitive to the overall stability factor than that of foundation.The research results of seismic active earth pressure,permanent displacement and wallslope overall stability of gravity wall tensioned with horizontally flexible reinforcements in this paper can provide guidance and reference for seismic design of this kind of engineering structure in practical engineering,which has important theoretical significance and engineering application value.