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Evaluation of the damping factor of foundation bases subjected to vertical vibrations

Conclusions

1. The damping factor b depends on the elastic properties of the soil base and the dimensions of the lower surface of the foundation. Hence, one of the values — the coefficient of uniform elastic compression Cz — makes it possible to find both the elastic and damping characteristics of the soil base. To evaluate the damping characteristics, it is expedient to use the specific damping factor introduced in this article.

2. To find the maximum amplitudes of unsteady vibrations of massive foundations under the action of an instantaneous impulse, use can be made of Eqs. (21)–(23), which determine the factor bz if the limit from which the elastic waves may be reflected (rock, soil layer with higher wave velocities, etc.) is located below the lower surface of the foundation at a depth greater thanl/2,l being calculated from Eq. (16). To find the parameters of steady vibrations of massive foundations, the damping properties of the soil base are determined by the factor bz, calculated from Eqs. (12)–(15).

3. The equations for the factor bz are related to the mean soil conditions; however, the effect of the characteristics of the geologic morphology is exerted on this factor more strongly than on the rigidity modulus of the soil base; hence, it is desirable to gather experimental data for the systematization and processing of which use can be made of the relations obtained in this article.

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Literature cited

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    N. P. Pavlyuk, "Vibrations of solid body resting on an elastic base," in: Vibrations of Foundations [in Russian], ONTI, Leningrad (1933).

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    V. A. Il'ichev, "Dynamic analysis of foundations," in: Collection No. 67 of the Scientific-Research Institute of Bases and Underground Structures, Foundations under Dynamic and Seismic Loads [in Russian], Stroiizdat, Moscow (1976).

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    L. S. Maksimov, "Parameters of free vibrations of large massive structures," Tr. Gidroproekta, Sb. No. 10.

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Additional information

Scientific-Research Institute of Bases and Underground Structures. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 15–18, September–October, 1981.

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Il'ichev, V.A. Evaluation of the damping factor of foundation bases subjected to vertical vibrations. Soil Mech Found Eng 18, 180–186 (1981). https://doi.org/10.1007/BF01711427

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Keywords

  • Soil Layer
  • Wave Velocity
  • Lower Surface
  • Elastic Property
  • Soil Condition