Profit
- An analytic method for test-free determination of mechanical characteristics of ice-rich soils as composite materials.
- An improved way of computing the design values of the mechanical characteristics of soils by the method of the smallest squares.
- Use of the design values in both the linear and nonlinear methods of settlement analysis for columnar and pile foundations.
The Objective of the Research
The objective of the research is to develop theoretically and substantiate experimentally the analytic methods for determination of mechanical properties of ice-rich soils with layered and other cryogenic structures (creep-strength, the point of fluidity, the limit of linear creep, the viscosity coefficient, long-term strength and non-linearity parameters of deformability) by the similar properties of the components (frozen non-ice-rich soil and ice) or by the similar properties of ice-rich soils with a different ice content, determined through experiments or tables.
Approaches
The main working hypotheses approved experimentally:
- estimation of ice-rich soil properties accordingly to the composite approach is curried out taking into consideration: the cryostructure and iciness at the expense of ice inclusions; physical-mechanical properties of mineral and ice inclusions; the stress-strain state of ground; the design temperature;
- deformations of an ice-rich soil are shown as the sum of compaction and creep strains;
- at low stresses, the rate of creep of an ice-rich soil is determined predominantly by the creep of ice layers, while at high stresses it is a function of the creep strains of ice and soil components;
- at low stresses, the steady-state creep of an ice-rich soil arises at rise of the steady-state creep of mineral layers;
- the condition of strains continuity and assumption of linear additivity of pressure in both ice and mineral inclusions are considered;
- in short-term tests, the long-term strength of an ice-rich soil is determined mainly by the strength of an ice-poor soil, while in long-term tests (low stresses) it depends upon the strength of components;
- experimental determination of the mechanical properties of an ice-rich soil can be fulfilled according to the uniaxial or triaxial compression test of ice and non-ice-rich soil, and also according to the model test;
- analysis of bearing capacity of foundations and appropriate deformations of ice-rich soils can be fulfilled by as the well-known methods using the proposed formulas and tables for determination of mechanical characteristics, as new methods which embrace non-linear behavior of ground and pile foundations (the sections 8,10 and 11 of the book).
The determination of the mechanical properties of ice-rich soils according to the components' properties is carried out by means of analysis using the approaches applied in the theory of composite materials. The theoretical investigations are fulfilled taking into account the numerous experimental data published in the literature and obtained in laboratorial tests of soil samples, punches and model piles.
The computation of long-term strength and steady-state creep rate can be made by the regression analysis, the appropriate design values of the mechanical characteristics being determined when necessary. The estimation of these values carries out taking into account their deviations from the average experimental 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 section 14 of the book).
A particular attention is paid to the manner of alteration of the steady-state creep rate and long-term strength of the components in the range of low stresses which are close to the long-term strength. There is studied the fact (revealed by the author) of altering the intensity of the decrease in the strength of ice and clay soils as the time-before-destruction increases, as well as the alterations in the intensity of the decrease in the steady creep rate in the range of low stresses (a bend of the appropriate regression lines).
The results of the computations of the creep-strength, point of fluidity, linear creep limit, steady creep rate, long-term strength and other magnitudes of the ice-rich soils fulfilled by the formulas obtained on the basis of the composite approach are compared with the results of the multifactor tests. The uniaxial compression and model tests of the ice, non-ice-rich and ice-rich soils have been conducted in addition necessarily. The resultant conclusions are confirmed by the stamp and prototype pile tests.
Based on the theoretical and experimental studies, the work provides the following:
- formulas for computation of the mechanical characteristics of ice-rich soils as per the similar characteristics of the components or ice-rich soils with a different ice content;
- proposals for laboratory and field tests;
- new methods of foundation analysis at both linear and non-linear statements.
Use of the suggested technique in practice of geocryological research and foundations designing allows to reduce considerably, or exclude completely, carrying out tests of frozen soils with various iciness.
Comments are represented through the author e-mail on the website:
https://sites.google.com/site/permafrostfoundations/english-version
