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In this study the effect of using a biopolymer soil stabilizer on soil stiffness characteristics was investigated. Chitosan is a bio-waste material that is obtained by chemical treatment of chitin (a chemical component of fungi or crustaceans’ shells). Using chitosan solution as a soil stabilizer is based on the assumption that the biopolymer forms temporary bonds with soil particles. What is important is that these bonds are biodegradable, so the product does not leave any harmful waste and has high eco-compatibility. The biopolymer itself is a by-product of many industrial chemical processes, so its application is compliant with the goals of sustainable geotechnical engineering. The effect of chitosan on soil shear strength, permeability or surface erosion has already been investigated in several different studies. In this study specimens of low-cohesive soil stabilized with two different chitosan solutions were subject to cyclic loading (torsional shearing test) and dynamic loading (resonant column) to obtain soil shear modulus G as a function of strain values. It has been shown that chitosan solution added to medium-grained materials improves their shear modulus G substantially (up to 3 times) even for relatively low chitosan concentration solutions (1.5 g of chitosan per 1 kg of dry silica sand). The results obtained in this study and the known chitosan properties suggest that chitosan solutions can be a very effective and eco-friendly short-term stabilizer for temporary geotechnical structures, e.g., working platforms.

With the accelerating progression of global climate change, switching to renewable energy sources is inevitable. Wind energy is a fast-growing branch of this industry, and according to the 2021 Global Wind Report, this trend must continue in order to limit the increase in global average temperature. While onshore wind turbines still dominate and account for most recent growth, offshore wind turbines are becoming a promising alternative for geographical, power density-related or even aesthetic reasons. Offshore wind turbines are subjected to more complex loading conditions and proper foundation design is very challenging, however, this is crucial for ensuring and maintaining the structure’s reliability. Soil dynamic tests are one of the bases for wind turbine foundation design. Technical regulations in many countries require such tests to be carried out in a Resonant Column (RC). In this study, a modification of the RC sensors and data acquisition system was introduced in order to conduct in-depth analysis of vibrating soil specimens. The new set of sensors contained five additional accelerometers (Analog Devices ADXL345) attached to the surface of a soil specimen that was subjected to dynamic loading. These accelerometers sent the data to a new data acquisition system, an ARM microcontroller with software developed by authors. The software was able to process test results synchronously with the original software of the RC device. Additionally, the load control system was supplemented with a current pulse generator, which makes it possible to observe the propagation of high-frequency mechanical waves in the tested materials. The modified dynamic testing equipment allowed for the measuring of accelerations and displacements at specific selected points located along the height of the sample, with sampling frequency more than three times higher than that offered by the sensors originally built into the RC device. As a result, some additional dynamic phenomena (i.e., disturbances in the uniformity of vibrations of non-cohesive materials, specimen–device contact imperfections) were observed in the tested soil specimens which remained undetected in standard RC test.