Soft Soil Performances Under Combined Static and Cyclic Loading
Mechanical properties of soft clays under combined static and cyclic stresses are experimental tested. The sensitivity of static stress and cyclic stress is examined in terms of the total and cyclic excess pore pressures and axial strains. Results show th
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Introduction Coastal areas are plenty of soft clays, on which there are static infrastructure loads as well as cyclic loads including traffic loads, wave loads, earthquake loads, etc. Recent research results indicate that the cyclic degradation of soft clays is closely related to the initial static shear stress apart from cyclic stress ratio, loading frequency, overconsolidated ratio, etc. In real situation, the excess pore pressure caused by the initial static shear stress can be either drained, partially drained or undrained, before the application of cyclic loads. The application of a drained initial static stress, also referred to as anisotropic consolidation, is to simulate the condition where enough time has elapsed after the embankment has been constructed and before cyclic loading has been applied, so that excess pore pressures have dissipated and the soft soil subgrade has gained sufficient strength. Researchers pointed out that the total shear strength might be proportional to the drained initial static shear stress [1–3].
J. Ni Y. Wei Y. Zhu Department of Civil Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China e-mail: [email protected] Y. Wei e-mail: [email protected] Y. Zhu e-mail: [email protected] X. Geng (&) School of Engineering, University of Warwick, Coventry CV4 7AL, UK e-mail: [email protected] © Springer Nature Singapore Pte. Ltd. and Zhejiang University Press 2018 X. Bian et al. (eds.), Environmental Vibrations and Transportation Geodynamics, DOI 10.1007/978-981-10-4508-0_23
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However, the application of an undrained initial static stress is to dissociate the effect of the initial static shear stress from the drainage that occurs during the application of a drained static shear stress. For an existing highway or an existing dam to be broadened, there may not be enough time for the dissipation of the excess pore pressures induced by the embankment before the application of traffic loads and wave loads, and therefore the excess pore pressures induced by the initial static shear stress can be considered undrained. The excess pore pressures and the axial stains induced by the initial static shear stress can be either included or excluded in the experimental analysis. Huang et al. [4] conducted cyclic triaxial tests on reconstituted Shanghai clays and found that a relatively large cyclic stress induces larger cyclic excess pore pressures and cyclic axial strains for a given value of combined static and cyclic stresses. The test results [5] from a series of direct, simple, cyclic shear tests conducted on intact sensitive clay from the St. Lawrence valley indicated that for an undrained initial shear stress of 0.3–0.8 times the undrained shear strength, the total shear strength was increased by 30% if 12 cycles are considered as the number of cycles to failure. In this paper, a series of tests on reconstituted Shanghai clay are conducted. Combined static and cyclic stresses with respect to different ratios are applied in seque
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