A Study On The Aseismic Reinforcing Mechanism Of Stabilizing Piles In Soil Slope

Earthquake-induced slope failures are popular in China and all over the world, and the stabilizing pile is one of the most common tools to prevent landslides. Therefore, the aseismic reinforcing mechanism of stabilizing piles in slope is an important topic in geotechnical earthquake engineering.In this paper, model concrete piles were produced, and a series of dynamic centrifuge model tests on pile-reinforced slopes were carried out, as well as a computer code was developed to analyze the three-dimensional dynamic consolidation problems. On the basis of the results of centrifuge modeling and numerical simulation, the aseismic reinforcing mechanism of stabilizing piles in slope was investigated. The main work and results are summarized as follows.1. A model concrete with similar mechanical properties as common concrete was designed to produce model piles. This kind of model piles is suitable for small scale model tests and can satisfy more strictly with the similarity criteria. Therefore, these model piles can reflect properly the dynamic response and failure characteristics of prototype reinforced concrete piles and overcome the model scale contradiction between the model and prototype resulting from the higher strength alternative materials, which are commonly used to make model piles.2. According to the results of dynamic centrifuge modeling, the aseismic effect and dynamic response of stabilizing piles in slope were investigated. Along with increasing the dimension of cross section of pile, the stable state of piles changes from statically failing to statically stable and dynamically failing then to dynamically stable, the deformation and nature period of the reinforced slope decreases, and the distribution of bending moment along pile changes essentially. This implies that the aseismic effect of stabilizing pile relies strongly on the dimension of cross section of pile. When the piles are installed near the crest of slope, the bearing capacity of piles can be mobilized sufficiently, while the deformation of the crest of slope is reduced effectively with the relatively large deformation of toe of slope. In contrast, when the piles are installed in the middle part of slope, the deformation of the crest of slope is bigger with the smaller deformation near the toe of slope.3. The dynamic behaviors of plain and pile-stabilized slopes with saturated subgrade were analyzed on the basis of dynamic centrifuge tests. In the former slope, the large deformation is induced by the slide of the toe of slope because of liquefaction of saturated subgrade during earthquake. The latter one maintains stable globally with smaller deformation because of the effective reinforcement of piles, although the toe of slope slides locally due to liquefaction of saturated subgrade. In contrast with the reinforced slope without water, the excess dynamic bending moment in piles increase sharply on condition that the subgrade is saturated. When the water level is high, landslide occurs and the piles break. This indicates that the water level has an important influence on the dynamic behavior and stabilizing effect of piles.4. A computer code for simulating three-dimensional dynamic consolidation with large deformation was developed based on the Pastor-Zienkiewicz III constitutive model for sand and Biot's dynamic consolidation theory. The results of numerical simulation for the prototypes of some typical model tests, such as excess pore pressure, the response acceleration and the bending moments in piles during earthquake agreed well generally with those of experiments, so that the reliability of the numerical program went through the benchmark in the complicated condition. Then, by combination of the fields of deformation, excess pore pressure and moments of pile obtained form the calculation and the results of centrifuge modeling, the characteristics of the kinematic interaction between pile and soil and the aseismic reinforcing mechanism of stabilizing piles in slope were investigated. Moreover, the numerical analysis can predict the stable state of the stabilizing piles and the moment when the piles break during earthquake.