Temperature and plant root effects on soil hydrological response and slope stability

Previous studies do not consider the coupled influence of temperature and plant roots on soil hydrological response and slope stability. This study aims to investigate the suction response and stability of a vegetated slope under changing temperature. A new hydrological model is proposed by considering both temperature- and rootdependent soil water retention curve and hydraulic conductivity function. The model is validated against the four-month field monitoring results. Then, a parametric analysis regarding the stability of a vegetated slope is carried out by considering root decay ratio (0 % and 20 %) and temperature (5 degrees C, 20 degrees C, and 45 degrees C) effects on soil hydraulic properties. The results show that the hydrological model can predict the suction response reasonably well when both temperature and plant root effects are considered. If only the temperature or plant root effects are considered, the suction response can be overestimated or underestimated by 35 % or 20 %, respectively. When plants on slopes are actively growing without root decay, there exists consistently larger suction under higher temperature during both transpiration and rainfall periods. Compared with the slope at 5 degrees C, the slope at 45 degrees C has a larger FOS and an 8.6-hour delay in terms of slope failure time under a 10-year return period of rainfall. However, for the elder plants with a root decay ratio of 20 %, the slope failure time is independent of temperature, even though the transpiration induced suction before rainfall is the highest under 45 degrees C. Decaying root induced negative influence on soil hydraulic properties can cancel out the positive influence of high temperature on FOS.