Basic Research On Seismic Design And Engineering Application Of GRS Abutment

Geosynthetic Reinforced Soil(GRS)is a type of reinforced soil that exhibits excellent structural performance and has broad application prospects in small and medium-sized single span bridges.Currently,the theoretical research on GRS abutments is insufficiently in-depth,particularly in terms of their dynamic characteristics.The mechanism of seismic deformation and failure remains unclear,and there is a lack of seismic design methods and specifications for GRS abutments,which impedes their promotion and application in China.Therefore,researching the dynamic characteristics of GRS abutments under earthquake action is essential to promote the development of seismic design theory and corresponding specifications for GRS abutments.Based on the summary of research achievements both domestically and internationally,this paper systematically studied the dynamic characteristics of GRS bridge abutments under seismic loads using methods such as shaking table model testing,numerical simulation,and theoretical calculation,aiming to solve the seismic design problem of modular panel GRS bridge abutments.This study established a calculation method for seismic dynamic earth pressure and lateral displacement applicable to GRS abutments.It proposed a seismic design process for GRS bridge abutments based on displacement and conducted applied research through seismic verification calculations for specific GRS bridge abutment projects.The main research content and conclusions are as follows:(1)Shake table model testing was conducted on the GRS abutment.The modular panel GRS abutment demonstrated good seismic performance in scaled shaking table model tests,achieving no damage even when the acceleration reached 0.4g.The combined action point of seismic active earth pressure on the front wall was between 0.45H and 0.48H(H is the wall height),and the combined action point of seismic active earth pressure on the side wall was between 0.40H and 0.44H.The horizontal displacement of the panel showed an overall increasing trend along the wall height,with a maximum value of 0.16%H.The maximum settlement difference at the top was 0.73 mm,indicating that the modular panel GRS abutment has good resistance to deformation under earthquake action.(2)Numerical simulation research on GRS abutments under dynamic action was conducted.It was found that the form of the panel,peak dynamic load,and frequency had a significant impact on the acceleration amplification,seismic dynamic earth pressure,panel horizontal displacement,top settlement,reinforcement strain,and potential fracture surface position of GRS abutment.The strength of reinforcement only had a small impact on the amplification of GRS abutment acceleration,seismic earth pressure,and horizontal displacement of the panel.Soil properties of the filling material significantly affected the amplification of GRS abutment acceleration,reinforcement strain,and potential fracture surface position.The setback of the bridge abutment slightly impacted the settlement of the top of the GRS abutment but had little effect on other factors.The thickness of the encryption zone significantly impacted the potential fracture surface position of the GRS abutment.(3)A calculation method for seismic active earth pressure of GRS bridge abutment was established based on the consideration of reinforcement friction,and compared with other methods.The calculated seismic active soil pressure coefficient increased with acceleration,and the combined force of seismic earth pressure was relatively close to the experimental value.The combined action point of seismic earth pressure was at 0.37H,which was lower than the test value and between the 1/3H and 0.39H given by current specifications.(4)This study proposed a specific calculation formula for seismic lateral displacement(permanent displacement)of GRS abutment based on the general form of estimating Newmark permanent displacement suggested by Martin&Qiu(1994).The calculated value of seismic lateral displacement of GRS abutment obtained using the formula in this article slowly increased with acceleration,and the calculated value was closest to the experimental value at an acceleration of 0.1g～0.4g.(5)The study proposed a displacement-based seismic design process for GRS bridge abutments and conducted applied research through seismic verification calculations for a certain highway GRS bridge abutment test project under different seismic peak accelerations.This method was used in seismic lateral displacement calculation and seismic active earth pressure calculation.