Effect of pre-dynamic loading on dynamic liquefaction of undisturbed loess
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Effect of pre‑dynamic loading on dynamic liquefaction of undisturbed loess Wei Liu1 · Qian Wang2 · Gaochao Lin3 · Wenwu Chen4 Received: 23 February 2020 / Accepted: 23 July 2020 © Springer Nature B.V. 2020
Abstract Earthquakes occur frequently in the Loess Plateau area, which result in damage to loess due to the disturbance of multiple cyclic loading. In this paper, the historical earthquake process is simulated by pre-dynamic loading treatment on undisturbed loess samples. Then cyclic tests are carried out on these treated samples to study the later liquefaction responses with different initial water content. The undisturbed sample is relative to the remold sample instead of the samples without disturbance. Results show that the axial deformation and pore pressure ratio of treated loess samples with initial water content of 5% are larger than those without treatment. For samples with initial water content of 10% and 15%, the cycle number required for liquefaction increases after treatment, but pore pressure ratio is between 0.18 and 0.36, which is less than the 5% water content samples. It means that liquefaction will have been formed before the excess pore pressure increases to large values. Combined with microstructural analysis, it is found that pre-dynamic treatment causes earthquake damage zone in loess with water content of 5%, which results in lower liquefaction stress ratio than non-treated ones. As for samples with water content of 10% and 15%, the internal voids become smaller and fine particles move into the gaps between large particles after treatment, resulting in denser structure which is hard to be liquefied. However, the increasing dynamic stress will aggravate the deterioration of loess at the water content from 5 to 15%. The changes of microstructure of loess samples are vulnerable to the dynamic stress amplitude and water sensitivity. Keywords Pre-dynamic treatment · Liquefaction · Loess · Stress path · Liquefaction stress ratio
1 Introduction Liquefaction refers to the process of stable flow of saturated soils due to sudden decrease or even total loss of shear strength induced by the increasing excess pore water pressure under earthquake and other cyclic loadings (Howells et al. 1976; Castro and Poulos 1980; Kayabasi and Gokceoglu 2018; Liu et al. 2020; Beyzaei et al. 2020; Enomoto 2019). * Wenwu Chen [email protected] Extended author information available on the last page of the article
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Bulletin of Earthquake Engineering
Liquefaction process is one of the most destructive phenomena that is particularly observed in loose sands during exposure to seismic action (Hughes and Madabhushi 2019; Karakan et al. 2019; Tasiopoulou et al. 2019; Beyzaei et al. 2020; Enomoto 2019). Since the 1964 Niigata earthquake in Japan and the Alaska earthquake in the United States, the destruction of structures caused by liquefaction has attracted the attention of geotechnical engineers. Relevant scholars began to work on the pattern of excess pore water pressure variation and th
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