Soil and structure interaction investigation features

The interaction of soils with underground structures is an important and complicated geotechnical problem, because a new stress-strain state is formed on their contact, associated with reduced strength properties of soils. To determine these characteristics, laboratory tests by direct shear scheme with stiff clay and loam interacting with a concrete surface were carried out. Soil samples were taken from a depth of more than 35 m in Moscow. The tests were carried out according to the “soil-soil” and “soil-solid surface” schemes with a speed of 0.005 mm/min for clay and 0.05 mm/min for loam. According to the results of laboratory tests, strains and deformations were obtained. Also, the strength reduction factors were determined equal to 0.53 for clay and concrete and 0.44 for loam and concrete. This coefficient is one of the main parameters characterizing the magnitude of decrease of the strength characteristics at the contact in numerical calculations. Moreover, two methods for modeling the contact zone of the soil massif and a single pile were considered in the PLAXIS 2D software package. In the first case, the problem was modeled with use special contact elements “interfaces”, which have zero (virtual) thickness, and in the second case, the contact zone was defined by a layer of soil of real thickness, for which the properties are equivalent to the properties of the virtual interface. The results of numerical modeling showed that the shear stresses on the contact in the case of a real interface will be less than when using a virtual interface, and the bearing capacity of the pile will decrease by almost 2 times.