Additions to the method of calculating the load-bearing capacity of two-layer foundations
https://doi.org/10.52170/1815-9265_2022_62_57
Abstract
There is often a weak underlying layer in the foundations of the designed structures. Such a layer reduces the bearing capacity of the foundation. This case is considered in the normative literature when determining the calculated resistance of the soil. There are no instructions for assessing the bearing capacity of a foundation with a weak underlying layer. Also, there is no strict solution to the theory of the ultimate equilibrium of soils for this scheme.
The article provides information about previous studies in which an algorithm has been developed to calculate the bearing capacity of a two-layer base using the logarithmic spiral method. Then, based on this algorithm, a program was written and patented for automated calculation. However, the logarithmic spiral method gives inflated values of the limiting pressure. Therefore, the purpose of this article is to determine the correction factor to obtain a reliable result of the bearing capacity of a two-layer foundation. The result of solving this problem is presented in this article.
Based on the fact that the bearing capacity of a two-layer base is in the range between the bearing capacity of a homogeneous base of strong and weak soils, a formula with a correction coefficient for its determination is obtained. The correction factor varies from 0 to 1 and depends on the depth of the weak layer. The concept of the depth of influence of a weak underlying layer is defined, at which a weak layer ceases to affect the bearing capacity of the foundation. Accordingly, at this depth, the correction factor will be equal to 1.
With the help of the written program, the depth of the influence of the weak layer is determined. And according to the obtained formula, the correction factor is calculated at the depth of the laying from 0 to the depth of the influence of the weak layer in increments of 0,1 m. Then, based on these data, a graph of the dependence of the correction factor on the depth of the underlying layer is plotted. Having this graph and the values of the bearing capacity of homogeneous foundations for strong and weak soils calculated according to SP 22.13330, the bearing capacity of a foundation with a weak underlying layer can be calculated at any depth of its laying.
About the Author
M. V. Shokhirev
Siberian Transport University
Russian Federation
Russian Federation
Maxim V. Shokhirev – Post-graduate Student of the Geotechnics, Tunnels and Subways Department
Novosibirsk
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Review
For citations:
Shokhirev M.V. Additions to the method of calculating the load-bearing capacity of two-layer foundations. Bulletin of Siberian State University of Transport. 2022;(3):57-66. (In Russ.) https://doi.org/10.52170/1815-9265_2022_62_57
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