Cyclic degradation and pore pressure dynamics of EICP treated hydrocarbon contaminated sands

Most cyclic soil models which are used to estimate strain and pore pressure accumulations, are soil specific and, often evaluate the accumulation model either as a function of the number of load cycles or they tend to utilize parameters which can only be obtained by using detailed laboratory tests. This paper attempts to enhance the capabilities of a simple plasticity model which can approximate the trend of pore pressure accumulation. This function uses a stress dependent degradation parameter which allows the yield loci to adjust and reduce its size at the end of each load cycle. The cyclic degradation model which was originally developed for clays, was adapted for sands and silts in this work with the use of two new parameters. The model was tested by using the cyclic triaxial data of three non-plastic soils. These samples were subjected to cyclic load amplitudes which are normally used in most seismic studies. The modified degradation model could predict fairly well the pore pressure accumulation in high-load amplitude tests but lead to over-prediction in low-load amplitude tests, unless the function was allowed to taper off at large cycles. Notwithstanding the above, the above cyclic model using the degraded yield surface, was incapable of correctly predicting the stress paths which were close to the sample’s ultimate state as it failed to permit phase transformation which is generally observed in sands and silts.

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Significance and technological capacities of natural study of the ground pore pressure dynamics under the freezing and thawing conditions

Геоэкология Инженерная геология Гидрогеология Геокриология ◽

10.31857/s0869-78092019582-88 ◽

2019 ◽

pp. 82-88

Author(s):

А. А. Ginzburg ◽

R. G. Kal’bergenov ◽

V. S. Isaev ◽

G. S. Tipenko ◽

D. O. Sergeev ◽

...

Keyword(s):

Pore Pressure ◽

Soil Mass ◽

The Arctic ◽

Monitoring Systems ◽

Freezing And Thawing ◽

Geotechnical Monitoring ◽

Hardware Development ◽

Pressure Dynamics ◽

Technological Base

Actual geotechnical monitoring systems and models of geocryological processes are aimed at assessing and preventing hazardous dynamic impacts on infrastructure facilities in the Arctic and Subarctic of Russia. The level of methodological support and hardware development of these systems are insufficient in Russia in the context of a changing climate, growing environmental impact and decreasing quality of geological survey and design. Pore pressure is successfully studied at the sample level in the laboratory and in the field by using the static sensing method, however, the dynamics of pore pressure and the physical patterns of this dynamics in soil massifs remain studied inadequately. For theoretical reasons, pore pressure should change under the influence of processes associated with freezing and thawing, and, consequently, it should affect the intensity of gas hydrate dissociation as well as the mechanical properties of soils. The modern technological base provides new opportunities for the study of the pore pressure dynamics in the soil mass. This opens prospects for improving geotechnical monitoring systems for the protection of infrastructure facilities from adverse natural and man-made impacts.

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