Abstract
This study investigated the antiliquefaction property of the pile group. It is shown in the pore pressure ratio, pile acceleration, and bending moment response of saturated silt fine sand. The response law of pile acceleration and bending moment during liquefaction development is proved. The results show that liquefaction occurs in single piles, four piles, and six piles under the action of 0.35 g seismic wave. But the time of liquefaction is different. There is an obvious difference in the response of pile acceleration and bending moment during liquefaction. Liquefaction in the saturated silt fine sand develops from shallow to deep. The complete liquefaction of six piles takes the longest time, while the single pile takes the shortest time, and the average delay was 8.82 s. With the increase of the number of piles, there are some differences in pile acceleration, magnification factor, and pile bending moment, which are mainly reflected in time. The peak acceleration appearance of six piles was 3.08 s later than that of the single pile on average. The maximum bending moment appearance of six piles was 1.96 s later than that of the single pile on average. The acceleration and bending moment of the pile begins to attenuate when the pore pressure ratio increases. It shows that the saturated silt fine sand has softening and damping effect before liquefaction. In summary, the antiliquefaction performance of the pile group is better than that of a single pile. In the seismic design of pile foundation in liquefied soil, the antiliquefaction performance of the pile group is better.
Highlights
According to the results of earthquake damage investigation, the seismic performance of pile foundation is better than other types of foundation
Sand liquefaction induced by earthquakes is one of the important causes of earthquake damage to the pile foundations [1,2,3,4]. erefore, research on antiliquefaction treatment measures of pile foundation has become an important direction and hot topic in geotechnical engineering. rough the research on the antiliquefaction performance of pile foundation, it is found that the antiliquefaction technical measures can be divided into two kinds [5,6,7,8]
One is to treat the soil around the pile to completely lose the liquefaction condition, which has a large amount of work and large limitations. Another is that liquefaction is allowed without changing the properties of the soil around piles, which optimizes the design of the pile foundation to improve the antiliquefaction performance of the pile foundation itself
Summary
According to the results of earthquake damage investigation, the seismic performance of pile foundation is better than other types of foundation. In terms of model tests, Feng et al [16] and others studied the dynamic response of rock-socketed pile foundations under strong earthquakes and the influence of sand liquefaction on the dynamic response of bridge pile foundations and proposed a method of burying the pile foundation with saturated silt liquefaction judging method based on depth, seismic intensity, and pore pressure ratio. Xu et al [17] researched pile group dynamic responses characteristics in liquefied and nonliquefied sites by shake table tests. Ere are few studies on the micromanifestation of pile group liquefaction resistance superior to single pile foundation under earthquake In this shaking table test, three working conditions of the single pile, four piles, and six piles were designed. Engineering Background e Haiwen Bridge (formerly Puqian Bridge) in Hainan Province, China, is located in a strong earthquake zone. e seismic fortification intensity of the Haiwen Bridge is VIII degree. e basic design acceleration of ground motion is 0.35 g, which far exceeds the design value of fortification intensity (0.20 g) in Article 3.1.4 of the “Specification of Seismic Design for Highway Engineering (JTGB02-2013)” [27] and exceeds the standard value of penetration hammer of liquefaction criterion in Article 4.4.2. e liquefaction of sand soil is serious, so it is urgent to study the antiliquefaction performance of pile foundation. e Haiwen Bridge adopts pile group, among which 55# pile foundations are 4 friction piles with 2m diameter and 35m length, as shown in Figure 1. e pile foundation passes through clay 5 m, fine sand 8 m, pebble soil 25 m from top to bottom. e specific gravity of the fine sand is 2.67, the saturation gravity is 22.19 kN/m3, the void ratio is 0.83, the plasticity index is 19.3, and the liquidity index is 0.32
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