| Loads in practical engineering always change cyclically along with time, and the moving traffic loads and sea-wave loads both are common cyclic loading. Under these conditions, the stress path on foundation soil element is extraordinary complex. And one of the important features of the complicated stress path is the coupling of multidimensional stress, which means not only the vertical stress changes cyclically, but also the horizontal stress and shear stress follow the similar cyclical changes. Study on the response behavior of soil in this kind of multidimensional stress coupled field, aimed at reproducing the more accurate stress state of soil element, will be helpful to understand and explore the service performance of foundation soil under actual stress condition. As we well know, more and more traffic and ocean projects are being constructed in the coastal areas of China, where deep soft clay layers are widely distributed. Soft clay is tend to suffer large deformation and even failure under the complex cyclic stress path because of its low strength and high compressibility, which probably lead to failure of upper structure and even engineering disasters. Therefore, experimental study on the behavior of soft clay under multidimensional coupled stress path will contribute to exploring the catastrophe mechanism of soft clay and developing the disaster control technology.In this study, a series of multi-dimensional coupling stress path tests on Wenzhou undisturbed soft clay samples are carried out through the GDS static/dynamic true triaxial apparatus and dynamic hollow cylinder system. The detailed research contents are as follows:(1) Vertical-horizontal coupling monotonic shear tests on Wenzhou saturated undisturbed soft clay samples under true triaxial stress path are conducted firstly in this study. And the stress-strain and excess pore pressure response as well as strength characteristics of soft clay under undrained conditions are discussed. Meanwhile, the influence of horizontal stress is analyzed, and then the experimental failure surface is obtained through the projection of all experimental failure points to the deviatoric stress plane. Afterwards, some well-accepted criterion, such as Mohr-Coulomb, Lade-Duncan and SMP model, are adopted to simulate the experimental failure surface to determine which one is most suitable to describe the monotonic strength properties of Wenzhou soft clay, which will provides the basis for subsequent multi-dimensional coupling cyclic stress test research.(2) Lade-Duncan criterion which is verified by true triaxial monotonic shear test on Wenzhou soft clay is embedded in ABAQUS computing model through the UMAT subroutine. And a3-D ballasted railway embankment model is established to analyze the change of stress path under the passage of traffic loading, and the results of this simulating calculation will provide theoretical basis for the multi-dimensional coupling cyclic stress path.(3) The evolution rule of cyclic strain of various dimension, cyclic pore pressure, stress-strain hysteresis curve and rebound modulus under vertical-horizontal coupling cyclic stress path are studied through dynamic true triaxial test on anisotropic consolidated soft clay. And the effect of vertical-horizontal coupling stress ratio, cyclic stress level and vibration frequency on the dynamic response characteristics of saturated undisturbed soft clay is discussed as well.(4) A series of undrained tests under vertical-torsional coupling cyclic tress path are carried out through the GDS dynamic hollow cylinder test system to study the dynamic response characteristics of anisotropic consolidated soft clay suffering principal stress rotation. The evolution regularity of dynamic strain, dynamic pore pressure, stress-strain hysteresis curve as well as rebound modulus in the vertical-torsional coupling cyclic tress condition are analyzed involving the effect of cyclic stress level and vibration frequency. |
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