Study on the effect and mechanism of hot-air-boosted vacuum preloading solidification of dredged silt via model tests

The traditional vacuum preloading method (TVP) is improved, and a “hot-air-boosted vacuum preloading (HAVP) method”, which combines vacuum preloading with hot gas injection into soil for heating, is proposed. The thermal‒mechanical coupling consolidation mechanism of dredged silt under the action of HAVP is discussed by selecting hot gas at 120 °C and 60 °C for a model test of hot gas pressurization, and process optimization is carried out by analyzing the measured data. The results show that HAVP can improve the soil settlement compared with TVP and that the settlement rate of the 120 °C group is better than that of the 60 °C group. A pressure of 20 kPa can achieve better consolidation, whereas a higher pressurization pressure has no obvious effect on the consolidation effect. After heating, the pore water pressure inside the soil increases, and the soil gradually rebounds during the heating process. The vacuum attenuation in the silt layer near the drainage plate is more uniform. In this test device, gas at 20 kPa and 120 °C is introduced, the influence range of the temperature in the horizontal direction is not more than 20 cm, and there is a more obvious warming phenomenon in the vertical direction at 60 cm, indicating that air flow can effectively increase the temperature of the soil. After HAVP, the gap between the soil particles is significantly reduced; the mechanism of hot gas pressurization is attributed to the combined effects of bubble disturbance, crack formation, additional pressure, and vacuum negative pressure reapplication.