The impact of reinforcing vegetation roots on the stability of expansive soil slopes with moisture absorption and expansion was investigated. Then, poinsettia is selected as the slope protection plant, and ABAQUS software (version 2022) with secondary development is used to simulate the moisture absorption and expansion of the expansive soil slope. After that, the strength reduction method is employed to study the effects on the displacement and plastic zone, and on the shallow layer of the expansive soil slope at different rainfall conditions. The following points are revealed: (1) The roots of the poinsettia can reduce the displacement of the slope. But, when the rainfall intensity exceeds the soil permeability coefficient, the soil reinforcement effect decreases. (2) The poinsettia root system can alleviate the concentration of plastic strain, disperse the plastic zone, and increase slope stability along the distribution of the roots. (3) The poinsettia roots can improve the shallow stability of the slope. But when the rainfall intensity exceeds the surface permeability coefficient, the magnitude of the reinforcement decreases. The results demonstrate that the poinsettia roots can enhance shallow slope stability. However, with increasing rainfall intensity, the ability of the poinsettia roots to enhance shallow slope stability gradually weakens.

To investigate the mechanism of reinforcing soft soil with cement-mixing pile, based on ABAQUS secondary development, a numerical simulation study of the hydration reaction of cement-mixing piles was conducted. In this study, the influence of ground temperature variations on the distribution patterns of the temperature field in and around the pile was also considered. The temperature field of the pile–soil model can be primarily divided into two stages: the temperature rise stage (0~5 d) and the temperature decrease stage (5~90 d). The following observations were made: (1) The temperature of the pile body rapidly increased within the first 5 days, dissipating heat to the surrounding soil, leading to an elevation of the temperature in the soil around the pile and a decrease in soil moisture content. Around the 5th day, the temperature reached its maximum value, and the heat release rate of the pile body was higher than that of the surrounding soil. (2) With a 15% cement admixture, under the influence of 425^# cement hydration, the temperature inside the pile increased by 5 °C, and the temperature in the soil around the pile increased by 4.2 °C. After considering the ground temperature, the temperature in the soil around the pile increased by 4.6 °C. (3) The maximum temperature generated during the hydration of 425^# Portland cement is higher than that of 525^#; the temperature of the soil around piles made with 425^# cement is consistently higher than that made with 525^#. (4) The hydration temperature of piles with a 10% cement admixture increased by 4.4 °C; for piles with a 15% cement admixture, the hydration temperature increased by 6.6 °C; and for piles with a 20% cement admixture, the hydration temperature increased by 9.1 °C. The temperature field of this structure gradually stabilizes after 7 days with increasing time and cement admixture. The results indicate that the hydration of cement-mixing piles raises the temperature of the soil around the piles. Additionally, the temperature resulting from the hydration of cement-mixing pile increases with the addition of cement.