Stress disturbance on the cyclic behavior of soils and its impact on geotechnical structures

Unexpected long-term settlement of roads or tunnels has been observed after opening to traffic. Existing studies have suggested that traffic loading is one of the reasons for that. Due to space limitation, many pits and tunnels are inevitably to be constructed next to existing roads, railways and tunnels which may be subjected to traffic loading. The excavation changes the stress state in soils along different stress paths and affects the deformation behavior of soils under cyclic loading. To study the impact of stress disturbance on soil behaviour under cyclic loading, a large number of cyclic triaxial tests were carried out to investigate the cyclic deformation behavior of typical sand and clay samples. The tests on clay are performed under undrained condition to reveal the axial strain and excess pore water pressure accumulations, and the tests on sand are carried out under drained condition to investigate the axial and volumetric strain accumulations. The stress disturbance is simulated by changing the radial and axial stresses in between loading cycles under different stress paths. The dependence of the strain accumulations on the stress disturbance schemes is presented and discussed under different confining pressures, loading frequencies (on clay) and relative densities (on sand). The effects of precedent stress history on the direction of strain accumulation and critical stress ratio of sand are analyzed. The effects of loading intermittency on the cyclic deformation behavior of soft clay are also investigated. Preliminary experimental results show that loading intermittency enlarges the strain accumulation of soil. In addition, a series of physical model tests were performed on a footing in dry sand to further investigate the effects of nearby excavation on the settlement behavior of existing structure under cyclic loading. The lateral excavation is simulated by translating a retaining wall between loading cycles. The cyclic loading-induced footing settlement behavior and the earth pressure in ground are presented and discussed under different lateral displacements of the retaining wall. An empirical model is proposed to estimate the accumulative deformation of soils with the consideration of lateral unloading effects between loading cycles. After being validated using cyclic triaxial test results, the proposed model is employed to predict cyclic loading-induced settlement of an existing road reported in literature and the footing modeled in the physical model tests before and after including the lateral pit excavation. The predicted accumulative settlement is comparable with that observed in the physical model tests.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2022

Author dc:creator

• Liu, Zhiyong

• Soft clay and sand
• Cyclic loading
• Excavation activities
• Stress disturbance
• Permeant deformation and excess pore water pressure
• Stress state
• Soil’s memory
• The direction of strain accumulation
• The flow rule of Modified Cam Clay
• Physical model tests
• Footing settlement under cyclic loading
• The prediction of accumulative deformation
• Intermittent cyclic loading
• anzsrc-for: 400502 Civil geotechnical engineering

Statement dc:rights

• open access
• CC BY 4.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

en

Identifier

https://doi.org/10.26190/unsworks/24154

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/100447