Flexible wall device and method for measuring gas permeability coefficient and gas diffusion coefficient of soil

A flexible wall device for measuring gas permeability coefficient and gas diffusion coefficient of unsaturated soil, comprising:

• a gas washing device;
• a confining pressure-volume change system;
• a drying-wetting cycle control system;
• and
• a gas measuring device;
• wherein the gas washing device comprises a high-purity nitrogen cylinder, a pressure reducing valve, a pressure regulating valve and a steady-flow valve;
• wherein the confining pressure-volume change system comprises an air compressor, a first pressure regulating valve, a second pressure regulating valve and a volume change measuring tube;
• wherein the drying-wetting cycle control system comprises a humidity controller, a first humidity controller valve and a second humidity controller valve;
• wherein the gas measuring device comprises a top lid, a cylindrical wall, a base, an upper chamber and a lower chamber, wherein the top lid, the cylindrical wall and the base are connected by bolts and nuts, and the base has four passages, wherein the four passages are respectively connected to the gas washing device, the confining pressure-volume change system, the drying-wetting cycle control system and the gas measuring device;
• and
• wherein between the base and the top lid are sequentially arranged from bottom to top as the lower chamber, a lower perforated plate, a lower permeable stone, a sample, an upper permeable stone, an upper perforated plate, the upper chamber, and a control rod;
• wherein the top lid, the cylindrical wall and the base enclosing a pressure chamber;
• the four passages of the base are respectively an air inlet passage, an air outlet passage, a water inlet passage and a base passage,
• wherein an air inlet end of the air inlet passage is connected to the gas washing device, and an air outlet end of the air inlet passage is connected to the upper chamber;
• wherein an air inlet end of the air outlet passage is connected to the upper chamber, and an air outlet end of the air outlet passage is connected to the drying-wetting cycle control system;
• wherein a water inlet end of the water inlet passage is connected to the volume change measuring tube, and a water outlet end of the water inlet passage is connected to the pressure chamber;
• and
• wherein a first end of the base passage is connected to the lower chamber, and a second end of the base passage are respectively connected to the drying-wetting cycle control system and the confining pressure-volume change system.