The method is described in the book of D.Sc. A. Gerasimov “Foundations in Permafrost” (sections 1.2, 4, 6.2, 7.2.1, 8, 10, 14, 15):
https://sites.google.com/site/permafrostfoundations/english-version
Preview
- Analytic method for test-free determination of mechanical characteristics of saline frozen soils as composite materials.
- An improved way of computing the design values of mechanical characteristics of soils by the method of the smallest squares.
- A design methods for calculation bearing capacity and settlement of pile and columnar foundations on saline frozen ground deforming in the unsteady creep stage.
The Objective of the Research
The research objective is to develop theoretically and substantiate experimentally the analytic methods for determination of the mechanical properties (long-term strength, point of fluidity, viscosity coefficient, unsteady creep parameters and design resistances) of saline frozen soils with various degree of salinity and different ionic composition of salts by the properties of a similar non-saline soil or a saline soil with a different salinity, with a correction for the physical properties of the soil investigated.
Approaches
The working hypotheses approved experimentally:
- the mechanical properties of frozen soils are to a great extent conditioned by the unfrozen water amount depending upon many factors, of which the main ones are temperature, salinity, dispersion and peat content of soils (and as they increase the unfrozen water amount also increases), as well as ionic composition of salts in pore water;
- the well-known analytic models applied in frozen soil mechanics have been used to determine strength and creep of the saline soils;
- saline frozen soils are characterized by considerable deformation at the primary (unsteady) creep stage which, as a rule, should be taken into account when designing;
- to describe quantitatively, the unfrozen water and ice amount in soil in a wide temperature range, as well as the dependence of the mechanical properties upon various factors, have been taken into consideration, allowing to obtain the universal formulas;
- when determining the design temperature of saline permafrost, the significant influence of temperature upon thermal and mechanical properties of frozen saline soil should be taken into account;
- rheological properties of saline frozen soils at the same homologous temperature are often not depended practically on their salinity and ionic composition of salts.
The investigations of the dependence of the saline soils' mechanical properties upon the determining factors are conducted by analyzing the numerous experimental data published in the literature, as well as those obtained in the underground arctic laboratory। The quantitative evaluation of the dependence of these properties upon temperature is fulfilled by the well-known formulas.
The computation of the unfrozen water amount, long-term strength, the point of fluidity, the viscosity coefficient, unsteady creep parameters and design resistances of soils is made by the regression method, the appropriate design values of the mechanical parameters being determined when necessary.
The rigorous estimation of these values can be made taking into account their deviations from the average test values, with the help of the reliability coefficient which is determined by the specially developed numerical procedure through the analysis of confidence zones for the regression line.
The ascertained analytical relationships allow to determine the rheological properties by the similar properties of a non-saline soil or a saline soil with a different salinity and by the simplest physical properties of the soil investigated, commonly without analyzing its unfrozen water amount in the temperature range and determining the ionic composition of salts.
Determination of the design temperature of saline permafrost soils used to find the design values of the mechanical characteristics which are applied in calculations of bearing capacity and settlement foundations is fulfilled based on the analysis of thermal regime of permafrost.
Effective thermal characteristics of soils can be used in the calculations taking into account the soil's unfrozen water amount in the negative temperature range.
The thermal regime is analyzed by the numerical methods in a number of cases. Then the results of the numerical calculations are compared with the results of the computations of design values of temperature by the approximated analytic solutions including those recommended by the standards. The simplified methods to determine the design maximum (for columnar foundations) and equivalent (for pile foundations) temperature of saline soils are considered.
Based on the theoretical and experimental studies, the given information can provide the following:
- formulas for computation of the mechanical characteristics of saline soils by the similar characteristics of a non-saline soil or a saline soil with a different salinity;
- the list of the simplest physical properties of saline soils to be determined when exploring;
- the recommendations on determination of the design values of physical and mechanical characteristics of saline soils with test data statistical processing by the improved method of the smallest squares;
- a design method for determination of the design temperature of saline soils in order to analyze bearing capacity and settlement of columnar and pile foundations;
- use of the progressive estimation methods for bearing capacity and settlement analysis when the unsteady creep of ground - at linear and nonlinear dependence its strains on stresses.
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https://sites.google.com/site/permafrostfoundations/english-version
