The researchers conducted tests on Jingmen weak expansive soil to study how it changes in volume when compacted. They found that the volume change of the soil depends on factors like moisture, external load, and swelling potential. By analyzing the results, they discovered that the volume change is influenced by the hydro-mechanical path the soil follows. The tests showed that the soil's volume change is affected by its compactness, structure, and swelling potential. The researchers also developed a formula to predict the soil's swelling behavior over time, which can help in understanding and managing expansive soil.