A straightforward method has been discovered to assess the interaction between soil and reinforcing elements.

To ensure the stability of structures, such as the foundations of buildings and embankments for roads and platforms, reinforced soil structures are often utilized. These consist of alternating layers of soil and a reinforcing geosynthetic material made from synthetic raw materials. When designing these structures, it is crucial to understand how the reinforcing element interacts with the soil to guarantee reliable performance in the future. Currently, Russia has only one accepted methodology for conducting such tests, which is costly and labor-intensive, and there is a lack of sufficient foreign laboratory equipment. Researchers at Perm Polytechnic University have developed a convenient domestic method that requires less financial and time investment while remaining effective for application within the country's context.

2025-02-24 10:00:09https://naked-science.ru/article/column/sposob-otsenit-vzaimodejs

A patent has been issued for the invention patent. The research was conducted as part of the implementation of the strategic academic leadership program "Priority 2030".

Before beginning the construction of reinforced soil structures, appropriate calculations must be carried out. Such structures include embankments intended for roads and railways, foundations for shallow foundations, as well as reinforced soil retaining structures. However, insufficient study of the interaction processes between the soil and the reinforcing geosynthetic elements is one of the reasons hindering the application of such structures.

When calculating, it is necessary to take into account the contact characteristics of the interaction between the reinforcement and the soil, one of which is the friction angle, characterizing the joint work of the soil and the reinforcing (strengthening) material. The strength and durability of reinforced soil structures depend on this parameter. The values of the friction angle at the contact boundary between the reinforcing material and the soil are variable and depend on a multitude of factors – including the depth of reinforcement, soil type, reinforcement material, and their interaction with each other.

The accepted national standard describes the method for determining contact characteristics based on the results of tensile tests of geosynthetic material pulled from the soil mass. The main one is the friction angle at the "soil-geosynthetic" contact. The significant cost and labor intensity, as well as the necessity to use specialized equipment that is not manufactured in Russia, prevent the widespread application of this methodology.

Scientists at Perm Polytechnic have developed a more accessible, yet equally effective method for determining the friction angle, utilizing equipment available in many laboratories across the country.

“The proposed technology involves testing a soil sample reinforced with woven geosynthetic material in a triaxial compression device, where a sensor measures radial deformation, which is installed in the middle part of the test sample as an open chain or strip. The sensor records the moment of increase in the diameter of the sample in the reinforcement zone, which corresponds to the loss of grip between the reinforcing layers and the soil at a certain level of vertical stress. Such tests under various lateral pressures allow determining the friction angle at the contact of the geosynthetic material with the soil,” explains Maxim Kazakov, a graduate student at the Department of "Construction Production and Geotechnics" at PNIUP.

The soil sample in the triaxial compression device is reinforced horizontally with two layers of geosynthetic material in the middle part of the sample. The distance between the reinforcing layers equals the height of the radial deformation sensor chain. During the testing, the sensor installed in the reinforcement zone records the moment of increased radial deformation, corresponding to the loss of contact ("slip") of the reinforcing layers when the soil, expanding under the applied load, exceeds the boundaries of the geosynthetic material. Based on these indicators at various lateral pressures, a graph is constructed to determine the friction angle.

“Reinforcing granular soils with horizontal elements such as geotextiles and geogrids can significantly reduce the costs of constructing soil structures. Evaluating the joint work of soil and reinforcement and developing simple and inexpensive testing methodologies for such evaluations enable more effective application of horizontal reinforcement with geosynthetic materials in construction practices,” shared Vadim Ofrihter, the project's scientific supervisor, head of the Department of "Construction Production and Geotechnics" at PNIUP, Doctor of Technical Sciences.

The method developed by scientists at Perm Polytechnic allows for determining the friction angle at the contact of geosynthetic material with soil with minimal costs and labor intensity, using a triaxial compression device with a radial deformation sensor. The simplicity and accessibility of the technology contribute to the effective determination of important characteristics for calculating reinforced soil structures.