Recently,the actively heated fiber optic method(AHFO)has been successfully applied to monitor the soil moisture profiles in boreholes.To evaluate the influence of grouting materials on the monitoring results,a series of numerical and experimental studies were carried out.Two numerical models were established and the heat transfer from heat source to surrounding soils was simulated,and the grout moisture at different dewatering time was calculated.The simulation results indicate that the maximum heat disturbance radius is about 10 cm during the 20 minutes heating period,and in the first 10 minutes,the heat transfer characteristic is determined by heat source and grout,in which the temperatures are suggested to discard.If carbon fiber heated sensing tube(CFHST)buried in a borehole is broken and water flows into it,the heat transfer model will change largely.After water level dropping a height of H,the grout moisture reduces with time and then reaches a stable value.This moisture stabilization time depends on H:i)if H is 90 cm,it needs about 3 hours to becomes stable,i)if H is 9 m,25 hours have to cost,and ii)if H is 30 m,60 hours are need.When the grout moisture has already become stable,the measured moisture of surround soils has a high accuracy,and the AHFO method is effective under this condition.These findings provide a new approach for assessing whether the AHFO method is suitable for vertical soil moisture monitoring or not.