https://sites.google.com/site/permafrostfoundations/english-version
The objective of the method is to develop theoretically and substantiate experimentally the Express-Method for determination of the long-term strength (bearing capacity) and unsteady creep (settlement) parameters of frozen soils in laboratory and field tests.
Profit
The proposed Express-Method is:
- time saving, as less time is required for each load increment;
- money saving, as the prototype piles can be substituted by the reference ones, without affecting the reliability of the data obtained;
- applicable in any season, time of the year and permafrost temperature being considered when interpreting the results obtained.
The Method is distinguished for:
- its versatility, as it may prove useful for testing punches, pile models, prototype piles and soil samples; it can be applied for the cases of separate as well as joint response of the pile lateral surface and pile end, for both reinforced concrete and metal or wooden piles;
- comprehensiveness of the data obtained (test results help predict not only the frozen soils' mechanical characteristics, but the foundation bearing capacity and its settlement within the design maintenance life of the structure);
- high reliability of the predicted values.
Approaches
The working hypotheses approved experimentally:
- character of creep of the frozen soils is different for the ranges of stresses of the higher and lower long-term strength;
- soil strains at variable stresses occurs in accordance with the theory of strengthening;
- the well-known analytic models applied in soil mechanics have been used to determine the long-term strength and creep strains of the frozen soils at constant stresses.
The new Express-Method is based on the soil deformation theoretical model being worked out, which is described by the theory of strengthening; the parameters of such deformation and bearing capacity are determined basing as on the usual linear regression analysis as on the plural regression analysis of the deformation equation.
The advantages and disadvantages of the well-known methods of processing the laboratory and field test data are analyzed, and these methods are compared with each other and with the proposed means of processing the data of the experiments carried out at different modes of loading.
Based on the theoretical investigations and analysis of many field tests of prototype and model piles (with the pile's lateral surface and end working both separately or jointly), the influence of stress-strain state of soils, cross-sectional size, material and roughness of the lateral surfaces of piles upon their bearing capacity and settlement is studied। According to the data of these investigations, the conditions of modeling are formulated and the possibilities are determined to carry out model tests of the reference piles of smaller sizes as well as the laboratory express-technique tests instead of the field tests of the piles of design sizes.
The possibility of using the proposed Express-Method for the field tests of piles and punches in unfrozen clay soils can be analyzed by the same way, followed by the appropriate experimental data.
Based on the theoretical and experimental studies, the method provides the following:
- qualitative and quantitative assessments of the advantages and disadvantages of the existing methods of frozen soil testing;
- a universal Express-Method for determination of the mechanical properties of frozen soils in laboratory and field tests of various types (samples of uniaxial and triaxial compression, laboratory models of the foundations, punches, reference and prototype piles with the lateral surface and end working separately or jointly) and at different modes of loading (constant or stepped loads of any duration, including those of different duration);
- a universal computer program for the quantitative assessment of the mechanical properties of frozen soils with the given confidence probability on the basis of the proposed method;
- criteria of modeling and recommendations on the technique of express-tests.
Comments are represented through the author e-mail on the website:
https://sites.google.com/site/permafrostfoundations/english-version
