Huabei Liu

Finite-Element Simulations of Full-Scale Modular-Block Reinforced Soil Retaining Walls under Earthquake Loading

A finite-element procedure was used to simulate the dynamic behavior of four full-scale reinforced soil retaining walls subjected to earthquake loading. The experiments were conducted at a maximum horizontal acceleration of over 0.8 g, with two walls subjected to only horizontal accelerations and two other walls under simultaneous horizontal and vertical accelerations. The analyzes were conducted using advanced soil and geosynthetic models that were capable of simulating behavior under both monotonic and cyclic loadings. The soil behavior was modeled using a unified general plasticity model, which was developed based on the critical state concept and that considered the stress level effects over a wide range of densities using a single set of parameters. The geosynthetic model was based on the bounding surface concept and it considered the S-shape load-strain behavior of polymeric geogrids. In this paper, the calibrations of the models and details of finite-element analysis are presented. The time response of horizontal and vertical accelerations obtained from the analyses, as well as wall deformations and tensile force in geogrids, were compared with the experimental results. The comparisons showed that the finite-element results rendered satisfactory agreement with the shake table test results.

Analyzing the Reinforcement Loads of Geosynthetic-Reinforced Soil Walls Subject to Seismic Loading during the Service Life

It is more rational to analyze permanent geosynthetic reinforced soil (GRS) walls against seismic loading based on their behavior during service life, but it has seldom been attempted. Calibrated finite-element procedure was used to investigate the reinforcement loads of GRS walls subject to seismic loading during service life, the results of which were compared to those predicted by Federal Highway Administration (FHwA) guideline. Parametric studies were carried out to investigate the effects of various wall parameters and characteristics of earthquake excitations. It is found that due to the isotach behavior of geosynthetics, the reinforcement loads during earthquake that occurs 10 years after construction were similar to those if the earthquake occurs at the end of construction. The FHwA method predicted roughly the maximum reinforcement load but it could not consider strain softening of soil and characteristics of earthquakes. The horizontal locations of maximum reinforcement load in lower reinforceme...

Finite Element Analysis of Pipe Buried in Saturated Soil Deposit Subject to Earthquake Loading

A coupled stress-flow finite element procedure, based on dynamic Biot equations, was used to analyze the behavior of pipe buried in liquefiable soil. The governing equations, soil constitutive model, finite element discretization and solutions were described. The results of analysis were compared with two cases of dynamic centrifuge test of soil deposit and pipe conducted at 30 g acceleration field. The horizontal soil deposit was analyzed followed by the deposit having a buried pipe of diameter 10 cm (3 m in prototype). The deposit was composed of loose Nevada sand that was saturated with a viscous solution in satisfying the similitude rules of time for the dynamic event and diffusion phenomena. The response of the ground, such as acceleration and excess pore water pressure, and the earth pressure and uplifting of the pipe, were presented and compared. The results of analysis indicated that a coupled stress-flow finite element procedure where the soil was expressed by Pastor–Zienkiewicz Mark-III model was able to simulate the dynamic response of the soil and pipe up to the stage of liquefaction. Several other issues related to the analysis were discussed.

Effects of relative creep of geosynthetic-reinforcements on the responses of geosynthetic MSE walls

The creep of geosynthetics leads to the decrease of long-term strength and the increase of deformation. More importantly, the influences of creep of geosynthetics are also affected by the creep properties of soils. In this paper, the effects of creep of geosynthetic-reinforcements are investigated using Finite Element procedure, on the context of its relations to the creep of backfill soils. The nonlinearity and creep of both geosynthetics and backfills were considered in the procedure. A model MSE walls at a height of eight-meter was analyzed using the Finite Element program ABAQUS. Geosynthetic reinforcements with different rates of creep were analyzed to investigate the effects of relative creep on the responses of the model MSE wall. It is found from the analysis that the relative creep rate between geosynthetic reinforcement and backfill soil is very important to the responses of the model wall. Both the reinforcement loads and the stress states in the soils were influenced by the relative creep rates of the two materials.