Soil–structure cyclic direct shear tests: a new interpretation of the direct shear experiment and its application to a series of cyclic tests
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- 作者：Suriyavut Pra-ai ; Marc Boulon
- 关键词：Characteristic state ; CNL and CNS paths ; Cyclic loading ; Direct shear tests ; Granular soil–structure interface ; Large number of small cycles
- 刊名：Acta Geotechnica
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：12
- 期：1
- 页码：107-127
- 全文大小：
- 刊物类别：Engineering
- 刊物主题：Geoengineering, Foundations, Hydraulics; Continuum Mechanics and Mechanics of Materials; Geotechnical Engineering & Applied Earth Sciences; Soil Science & Conservation; Soft and Granular Matter, Compl
- 出版者：Springer Berlin Heidelberg
- ISSN：1861-1133
- 卷排序：12
文摘
This paper presents a series of cyclic 2D direct shear tests on sand–rough material interfaces under constant normal load (CNL) and constant normal stiffness (CNS) conditions. The aim of these tests is to describe the behavior of the soil–pile contact subjected to a large number of cycles due to environmental or anthropic loadings. These cycles (typically 104 or less due to an early rupture) are small (10, 20 and 40 kPa in terms of shear stress). A new interpretation of the direct shear tests is proposed. The sample of soil is schematically composed of a sheared interface and of a buffer under oedometric load. The problem of sand leakage between the shear box and the rough plate, classical phenomenon in this type of test, is focused. The effect of initial density, position of “center of cycles” in stress plane (mean cyclic variables) and cyclic amplitude is investigated. The cycles are defined by the initial mean cyclic normal stress, the level of initial mean cyclic stress ratio and the normalized cyclic amplitude. Under CNL condition, either dilation or contraction is exhibited, in agreement with the characteristic state developed by Luong (International symposium on soils under cyclic and transient loading, Swansea, 7–11 January, pp 315–324, 1980). The influence of a prescribed normal stiffness is especially considered. It can be highlighted that CNS cyclic paths are always contractive. This contraction results in a drop of mean cyclic normal stress often called degradation of friction.