Experimental studies of the bearing capacity of a two-layer foundation

Abstract

In construction practice, heterogeneous foundations are often encountered. One of the options for such a foundation – a foundation with a weak underlying layer – is of particular interest; a lot of theoretical and experimental work has been devoted to this type of foundation. However, so far only the method of determining the calculated resistance of a foundation with a weak underlying layer has been used for design, while there is no standard method for assessing its load-bearing capacity. To a certain extent, this is due to the lack of a strict static solution to the theory of limiting equilibrium of soils for this case. The use of approximate calculation schemes requires experimental substantiation of the process of formation of an uplift region in a two-layer foundation upon its destruction.

This article presents the results of experiments to study the outline and size of the soil uplift area in the foundation with a weak underlying layer at different depths. The experiments were carried out in a small soil tray for plane strain conditions.

The test results show that, firstly, at a certain depth of a weak underlying layer, the bearing capacity of such a base is equal to the bearing capacity of a homogeneous sand base. Secondly, with a further decrease in the depth of the underlying layer, the bearing capacity begins to decrease. Also, the line of destruction of the base begins to extend into the underlying layer.

The article also presents the results of field tests by another author testing a two-layer base with a weak underlying layer. In these tests, the prepared stand was subjected to monotonic loading of a rigid circular support (stamp). During the tests, the load on the die and the deformation of the base were measured. The results of these field studies confirm the results of our laboratory tests.