Abstract
Cyclic mechanical loading of soils due to natural causes such as earthquakes or due to loads coming from structures causes the accumulation of strains and excess pore-water pressures endangering the long term serviceability and stability of the structures built on them. In this study, un-drained cyclic loading tests at 0.1 Hz frequency are carried out on a normally consolidated unsaturated silty clay soil at different deviatoric stresses for up to around 1400 cycles. The results of the tests, which were performed using a recently developed cyclic electromechanical tri-axial device, show a significant dependence of the cyclic mechanical behavior of the silty clay soil, such as in the form of cyclic axial and accumulated plastic strains, on the number of cycles and applied deviatoric stresses.
Highlights
IntroductionCyclic mechanical loading of soils leads to the accumulation of plastic or permanent strains and development of excess pore-water pressures, compromising the safety and stability of structures built on them [1].Cyclic loading behavior and the accumulation of high plastic strains of soils is of importance in many practical cases of geotechnical engineering, where the tolerance to displacement is small, and may endanger the long term serviceability of the structures, causing serviceability failures, and should be carefully studied prior to the design and operation of the structures.In this paper, the cyclic mechanical behavior of an unsaturated silty clay soil from Germany is assessed experimentally at different deviatoric stresses using a cyclic tri-axial device.2.1 Tested soil A silty clay soil (Fig. 1) from Thuringia, Germany was investigated in this study
A cyclic loading can cause the accumulation of plastic strains at high number of cycles even for small amplitudes of loading causing differential settlements, and endangering the long-term serviceability of structures
For un-drained conditions, a cyclic loading with a considerably high amplitude can cause the accumulation of high porewater pressures leading to the liquefaction or the loss of strength of the soil [1,2,3]
Summary
Cyclic mechanical loading of soils leads to the accumulation of plastic or permanent strains and development of excess pore-water pressures, compromising the safety and stability of structures built on them [1].Cyclic loading behavior and the accumulation of high plastic strains of soils is of importance in many practical cases of geotechnical engineering, where the tolerance to displacement is small, and may endanger the long term serviceability of the structures, causing serviceability failures, and should be carefully studied prior to the design and operation of the structures.In this paper, the cyclic mechanical behavior of an unsaturated silty clay soil from Germany is assessed experimentally at different deviatoric stresses using a cyclic tri-axial device.2.1 Tested soil A silty clay soil (Fig. 1) from Thuringia, Germany was investigated in this study. Cyclic mechanical loading of soils leads to the accumulation of plastic or permanent strains and development of excess pore-water pressures, compromising the safety and stability of structures built on them [1]. Cyclic loading behavior and the accumulation of high plastic strains of soils is of importance in many practical cases of geotechnical engineering, where the tolerance to displacement is small, and may endanger the long term serviceability of the structures, causing serviceability failures, and should be carefully studied prior to the design and operation of the structures. The cyclic mechanical behavior of an unsaturated silty clay soil from Germany is assessed experimentally at different deviatoric stresses using a cyclic tri-axial device. The cyclic mechanical behavior of the silty clay soil was analyzed experimentally using a recently developed electromechanical cyclic tri-axial testing device (Fig. 3). The cyclic testing apparatus consists of a loading machine (with a capacity of 25 kN and capable of applying cyclic deviatoric stresses with frequencies of up to 5 Hz) for applying vertical deviatoric stresses, a dynamic high precision cell pressure system capable of applying cyclic cell pressure to the specimen, two WDC dynamic real time digital closed-loop actuator controllers, one for the deviatoric stress and the other for the cell pressure, a single volume-pressure-controller or VPC 10/1000 back-pressure application system, an optional (unused) Huber Ministat 125 Pilot ONE heat pump for controlling the temperature of the cell using a circulating fluid (glycol + distilled water), and a PC data logger system for control and data recording
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