The microstructure test of the soil requires dry samples. Traditional drying methods, such as air drying and drying methods, have the disadvantages of shrinking the volume of the soil sample and changing the microstructure of the soil, and the reduction of the moisture content of the clay. Its microstructure will also change and its size will shrink. Conventional air drying and drying methods tend to make large changes in the microstructure of the soil, which cannot meet the test accuracy of microstructure research. The soil samples prepared by vacuum freeze-drying through a soil freeze dryer ensure that the microstructure of the soil samples does not change after dehydration.

Comparison of soil freeze dryers and drying air drying methods:

Air drying method. Due to the large surface tension of the liquid in the pores at normal temperature, the soil sample is often contracted and cracked, the soil particles are rearranged, and the pore state changes.

Drying method. Due to the uneven distribution of molecular stress during moisture migration in soil samples, cracks and volume shrinkage occur, and physicochemical interactions between soil particles can occur at high temperatures.

Freeze-drying method. The lyophilizer firstly turns the liquid water in the soil sample into amorphous ice without causing volume expansion, and then sublimates the water under a low temperature vacuum to discharge the vacuum piping system, so that the soil sample is dried.