Determination of the Boundaries of the Compressible Strata When Conducting Engineering Surveys

Purpose of research. Errors and inaccuracies in the preparation of deliverables based on the results of engineering surveys which are an integral and important part of the design and estimate documentation, can lead to irreversible consequences and significantly reduce the life of buildings and structures. The main difficulty in investigating soil physical and mechanical properties at a construction site is to determine the depth of excavation. This is due to the fact that an increase in the calculated depth leads to the increase in the cost of work, and its decrease leads to the risk of inaccuracies and errors in the design of foundations of buildings and structures. In accordance with the current regulatory documents, the excavation depth during soil investigation should be 1-2 meters below the boundary of the compressible strata. The condition on the basis of which the specified boundary is determined is provided. The development of a technique that allows determining the depth of the compressible strata at the stage of engineering surveying with adequate accuracy is an important task from a practical standpoint.
Methods. Determining natural stress Ϭ_zg,0 as the product of foundation depth d and the specific gravity of the soil above the base ɣ′_ІІ,  , taking into account the fact that the average pressure tends to the value of the estimated resistance of the soil, it is shown that physical-mechanical structure of the base soil exerts the main influence on the parameters of the compressible strata, and correspondingly, to the excavation depth value. In this case, the stresses transferred by the foundation of a building or structure have an indirect effect.
Results. The maximum values of the depth of excavation for engineering and geological surveying for tight coarse sand, medium density and fineness sand, and fine sand and sandy loam are determined.
Conclusion. It is concluded that the given technique allows determining the depth of excavation during engineering and geological surveying with an adequate accuracy.

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