Line-source superposition method of thermal response test without ground temperature recovery

For the condition that the ground temperature does not recover between the two successive tests in thermal response test (TRT), presents a calculation method of average heat conduction coefficient of soil based on the line-source superposition method, in which calculates the heat conduction coefficient of soil according to the linear relationship between time function and average fluid temperature. Establishes the line-source model for ground heat exchangers. Conducts the TRTs in three different boreholes with two different heating powers, respectively, and the ground temperature does not recover between the two successive tests. Analyses the second TRT data by using both of the conventional line-source method and the new method. The comparison shows that the results based on the superposition method have enough accuracy.