Geotechnical Engineering

DHARM

874 GEOTECHNICAL ENGINEERING

13. The elastic half-space theory, developed by Reissner (1936), Quinlan (1953), and Sung (1953) is
    one of the approaches for the design of machine foundations; the soil parameters needed are the
    shear modulus, the Poisson’s ratio, and mass density.
    The mass-spring-dashpot model, characterising the soil as a weightless spring in which damp-
    ing is present, is the other popular approach for the design of machine foundation; the theory of
    forced vibrations with damping is used.


14. Calculation of the unbalanced inertial forces is the important prerequisite in the design of foun-
    dations for reciprocating machines. Vibration absorbers such as springs may be interposed be-
    tween the machine and the foundation to limit amplitudes; in this case, the analysis becomes
    one with two springs.


15. Foundations for impact machines or hammers are generally reinforced concrete block-type, with
    suitable elastic pad below the anvil, and if necessary, between the foundation and the soil. Suit-
    able modifications may be needed in the analysis. Certain special considerations may be re-
    quired in the design and construction of foundations for impact machines.
    Barkan’s empirical procedure may be used for preliminary design of the weight of the foundation
    and the minimum base area required.


16. ‘Vibration Isolation’ is essentially of two types-the ‘active type’ in which isolation is required
    from the vibration produced by the machine itself, and the ‘passive type’ in which the foundation
    for delicate machinery is designed protecting it from the harmful effects of disturbing forces in
    the vicinity.
    There are several methods of isolation including the use of several structural measures and
    other approaches such as the construction of trench barriers.


17. Certain construction aspects of machine foundations need special care to ensure good perform-
    ance.

REFERENCES

1. Barkan, D.D.: “Dynamics of Bases and Foundations”, McGraw Hill Book Co., Inc., New York,
   USA, 1962.


2. IS: 1892-1979: “Code of Practice for Subsurface Investigation for Foundations”


3. IS: 1904-1986: “Code of Practice for Structural Safety of Buildings-Foundations”


4. IS: 2810-1979: “Glossary of Terms Relating to Soil Dynamics” (First Revision).


5. IS: 2974 (Part-I)-1982. “Code of Practice for Design and Construction of Machine Foundations-
   Part I Foundations for Reciprocating Type Machines” (First Revision).


6. IS: 2974 (Part. II)-1980: “Foundations for Impact-type Machines (e.g., forge hammers)”.


7. IS: 5249-1977: “Method of Test for Determination of insitu Dynamic Properties of Soil” (First
   Revision).


8. Major, A: “Vibration Analysis and Design of Foundations for Machines and Turbines”, Akademiai
   Kiado, Budapest, Collet’s Holdings Ltd., London, 1962.


9. Pauw, A: “A Dynamic Analogy for Foundation-soil Systems”. ASTM Special Technical Publica-
   tion No. 156, 1953.


10. Quinlan, P.M.: “Dynamic Testing of Soils: The Elastic Theory of Soil Dynamics” (Symposium),
    Special Technical Publication No. 156, 1953.


11. Reissner, E.: “Stationare Axial Symmetrische Durch Eine Schuttelude Masse Erragte
    Schuringungen Eines Homegenon Elastichen Haltraumes”. Inginieur Arch iv, Band, VII, 1936.