İSTİNAT (KLASİK KONSOL VE TOPRAKARME) DUVARLARINA ETKİYEN DİNAMİK YÜKLERİNİN BELİRLENMESİ (UDAP-Ç-19-08)

Project Supported by Other Official Institutions, 2019 - 2022

Project Type: Project Supported by Other Official Institutions
Begin Date: September 2019
End Date: December 2022

Project Abstract

In Turkey; besides the classical retaining walls such as gravity, semi-gravity, cantilever, crib/bin, the application areas of mechanically stabilized earth (MSE) type retaining structures has also a large place. Mechanically stabilized earth walls consist of facing elements (segmental panel, full height panel, metallic panel, modular block, geosynthetic wrap face etc.) and metal or geosynthetic reinforcements which connect to facing element. It is also of great importance to determine dynamic loads that will affect mechanically stabilized earth structures, since mechanically stabilized earth structures exhibits different behavior in terms of displacement, acceleration response and earth pressure than classical retaining structures under seismic loads. Equations for determining the dynamic loads acting on mechanically stabilized earth walls are still lacking in the literature. Additionally, there are important deficiencies in the design codes on the dynamic behavior of mechanically stabilized earth walls reinforced with polymeric geostrip. In addition, there are not enough experimental studies in the literature. In this study, the seismic behavior of mechanically stabilized earth wall reinforced with polymeric geostrip reinforcement and traditional gravity wall investigated under sinusoidal acceleration excitations using a series of 1-g shaking table test. In the MSE wall tests the effect of peak ground acceleration (𝑃𝐺𝐴), stiffness of reinforcement (𝐽) and slope angles of the backfill material (𝛼) on the acceleration amplification factors (𝑅𝑀𝑆𝐴), the lateral displacement of the wall (𝑆), the surface settlement of the backfill (𝑆𝑒𝑡), the distribution of static (𝜎𝑠𝑡) and dynamic (𝜎𝑑𝑦𝑛) earth pressure along the height of MSE wall and the strain (𝜀) or tensile load (𝑇) distributions on the polymeric geostrip reinforcement were investigated. In the traditional gravity wall tests, the effect of peak ground acceleration (𝑃𝐺𝐴), the slope angles of back of the wall (𝜓), slope angles of the backfill material (𝛼) on the acceleration amplification factors (𝑅𝑀𝑆𝐴), the lateral displacement of the wall (𝑆), the surface settlement of the backfill (𝑆𝑒𝑡) and the distribution of static (𝜎𝑠𝑡) and dynamic (𝜎𝑑𝑦𝑛) earth pressure along the height of traditional gravity wall were investigated. MSE wall test results showed that the dynamic forces obtained with traditional pseudo static limit equilibrium equations were excessively larger than measurement values. However, traditional pseudo static limit equilibrium equations for gravity retaining walls were insufficient to determine the dynamic force acting on the back of the wall. In MSE wall tests due to increasing the inclination angle of the backfill (𝛼); increases in the surface settlements (𝑆𝑒𝑡), lateral wall displacements (𝑆), static (𝜎𝑠𝑡) and dynamic (𝜎𝑑𝑦𝑛) earth pressures, acceleration amplification factors (𝑅𝑀𝑆𝐴) and strains (𝜀) or tensile loads (𝑇) on the polymeric geostrip reinforcements were observed.The stiffness of the polymeric geostrip reinforcement (𝐽) has a negligible effect on the lateral displacement (𝑆), static (𝜎𝑠𝑡) and dynamic (𝜎𝑑𝑦𝑛) earth pressures and failure surface geometry. In gravity wall tests, depending on increasing slope angles of backfill material (𝛼) and back of wall (𝜓), increase of surface settlements (𝑆𝑒𝑡), lateral wall displacements (𝑆), static (𝜎𝑠𝑡) and dynamic (𝜎𝑑𝑦𝑛) earth pressures were observed. It has been observed that the traditional pseudo static limit equilibrium equations proposed in the literature for gravity retaining walls are insufficient at peak ground accelerations (𝑃𝐺𝐴) greater than 0.25g. Upper limits for stress distribution behind of the MSE walls reinforced with polymeric geostrip have been proposed to the designers for static and dynamic conditions. Additionally, two different analytical limit equilibrium methods have been proposed for MSE wall reinforced with polymeric geostrip under seismic loads.