Study On The Seismic Response Of Reinforced Soil Retaining Walls With Rigid Facing Under High-intensity Earthquakes

The seismic performance of reinforced soil retaining walls has been verified in a large number of earthquakes,such as the JiJi earthquake in Taiwan,the Great Hanshin earthquake in Japan,and the Northridge earthquake in California.In Japan,Europe,and the United States,reinforced soil retaining walls are widely constructed in seismic areas.However,gravity retaining walls are still widely used in China due to the backward construction technologies and seismic concepts.According to the highway code in China,reinforced earth retaining walls should not be used when the peak ground acceleration is not less than 0.2gWith the development of infrastructure constructions in China in recent years,since a large number of civil engineering projects need to pass through high intensity regions,such as the Chengdu-Kunming double railway line and the Sichuan-Tibet railway line where the seismic fortification intensities are 0.3g and 0.6g which is larger than the maximum proposed value,0.4g in current design,respectively,it is necessary to carry out researches on the dynamic performance and seismic design of reinforced soil retaining walls.This research was supported by the Project of Science and Technology Research and Development Plan of China Railway Corporation-Researches on key technologies of light-retaining structures for railway subgrade in high intensity regions.Taking the structural form and the dynamic response of reinforced soil retaining walls as the research core,laboratory model tests,analytical calculations,and numerical simulations were carried outThe main research contents and conclusions of this thesis are as follows(1)Considering that the rigidity and deformation are small and large for blocked panel facing,respectively,and the construction of full-height rigid panel facing cast-in-place is complicate in fields,a new type of hybrid panel facing was proposed in terms of panel facing performances and construction requirements(2)According to the similarity laws,model tests of reinforced soil retaining walls with blocked panel facing,full-height rigid panel facing,and hybrid panel facing were designed and carried out,and the wall displacements,earth pressures,accelerations,reinforcement strains were collected.The results showed that the horizontal displacement of the model wall with blocked panel facing was largest,and the relative deformation between the blocks could be generated under high intensity loadings;the integrity of the hybrid panel facing was similar to that of the full-height rigid panel facing within range of the seismic fortification intensity for railways in China;the incremental earth pressures measured from the model tests were less than the theoretical values;the acceleration amplification factors of the walls increased firstly and then decreased with the input acceleration;the tensile forces of reinforcements for the wall with hybrid facing were smaller than those in full-height rigid facing case,especially when the input acceleration was greater than 0.4g(3)Analytical formulas of sliding and rotating yield acceleration coefficients were derived using a pseudo-dynamic method and a limit analysis method for reinforced soil retaining walls with rigid facings.The effects of pseudo-dynamic parameters and reinforcement parameters on walls'stabilities were analyzed.Parametric analyses showed that in contrast to the pseudo-static method,the proposed method could reflect the influences of pseudo-dynamic parameters,reinforcement arrangements,and strength of reinforcements on yield acceleration coefficients(4)The panel facing,backfill(reinforcement)-panel facing interactions were modeled by the Euler-Bernoulli beam and springs,respectively,and the natural frequency calculation model of reinforced soil retaining walls with variable cross-sections was established using a transfer matrix method.Parametric analyses showed that the influence of the panel facing on the natural frequency of reinforced earth retaining walls was more significant than that of the backfill(5)Dynamic simulation analyses of full-scale reinforced earth retaining walls under seismic loadings were carried out using Flac.Parametric analyses indicated that the loading intensity,backfill modulus,and panel modulus had a greater influence on the dynamic response of walls as compared to the backfill friction angle,reinforcements,and anchors(6)The seismic design of reinforced earth retaining walls was discussed based on the comprehensive analyses of model test results,numerical simulations results,and those calculated from pseudo-static methods.Results show that seismic stability was more influenced by the inertial force as compared to the dynamic earth pressure.Besides,the inertial force and rigidity of the facing have a significant influence on reinforcement loads.