测定原砂。粘土等粘结力小的试样透气性时，试样简内应放置与试样筒内壁紧密

Determine the original sand. When the air permeability of the sample with low cohesive force such as clay, the sample holder should be placed in a <br>metal sheet sleeve that closely matches the inner wall of the sample cylinder . The sheet metal sleeve is made of 2mm thin steel plate, densely covered with 2mm small holes (not less than 15 holes per square centimeter) and lined with 100 mesh screen cloth. When preparing the sample, put a metal sheet sleeve into the bottom of the sample holder, then put the sand sample, and then put another metal sheet sleeve into the sample cylinder and place it on the sample preparation machine. The metal sheet sleeve is accompanied by the sand sample. Be tight.

Determine the raw sand. When the sample is breathable with a small bonding force such as clay, the sample should be placed in a simple fit with the inner wall of the sample barrel<br>Metal sheet set. The metal sheet sleeve is made of 2 mm thin steel plate, which is covered with 2 mm small holes (no less than 15 holes per square centimeter) and lined with 100 mesh sieves. When preparing the sample, one piece of metal is placed at the bottom of the sample, then into the sand sample, and then another piece of metal is placed in the sample sleeve, placed on the sample machine, the metal sheet sleeve is piled together with the sand sample.

Determine the original sand. When the permeability of the sample with small cohesive force such as clay is small, the sample should be placed in the sample shell which closely matches the inner wall of the sample barrel<br>Sheet metal sleeve. The sheet metal sleeve is made of 2mm steel sheet, which is covered with 2mm holes (no less than 15 holes per square centimeter) and lined with 100 mesh sieve cloth. When preparing the sample, one metal sheet sleeve is put into the bottom of the sample brief, then the sand sample is placed, and the other metal sheet sleeve is placed in the sample barrel, and placed on the sample, and the metal sheet sleeve is tightly packed with the sand sample.