Study on the effect of microwave irradiation improvement on the long-term stability of expansive soil

In dry-wet cycles, the clay minerals of expansive soil repeatedly hydrate and dehydrate, causing its expansion and contraction, resulting in many cracks, which will bring harm to human engineering construction. Microwave, as an efficient material improvement method, has been used in clay mineral synthesis and material manufacturing. Our previous studies have proved that microwave technology can improve the performance of soil, but the long-term stability of expansive soil by microwave has not been studied. In this paper, microwave technology is used to improve the performance of expansive soil, and the effect of microwave on the damage law and long-term stability of expansive soil under dry-wet cycles is studied. The soil was heated to 200 °C, 300 °C, 400 °C and 500 °C respectively by microwave irradiation, and dry-wet cycle tests were carried out. According to the data of SEM, unconfined compressive strength and free expansion rate, the damage law and long-term stability of expansive soil were analyzed. The results show that, compared with original samples, the compressive strength can be increased by 27 times and the expansion rate can be reduced to 0 by microwave heating to 500 °C. In addition, microwave irradiation changes the way of fracture development. The change of fracture development pattern leads to the improvement of water resistance and strength of expansive soil, and thus the long-term stability of expansive soil is improved. The researches result of this paper can provide a reference for stability evaluation and design of expansive soil slope engineering.