Abstract: To investigate the reliability of spraying method for precisely preparing compacted bentonite samples with target water content, the water content at both upper and lower parts of compacted specimen was measured. Since orthogonal test method could reduce test times and shorten test cycles, nine orthogonal experiments were designed to study the influences of added water quantity (target water content), curing time, and compaction force on water content, with the help of the orthogonal table. Results imply that specific abnormal data indicates that the spraying method is artificial in the process of compounding, hence should be removed firstly. Moreover, with the increase of water addition, water content at both upper and lower parts of the compacted specimen decreased to be smaller than the target water content; local agglomeration was weakened, and water loss intensified. Curing time and compaction force have significant influences on the uniformity of water content in compacted specimens. As the spraying method is superior to other methods in terms of time, it is worth recommending after abnormal test data are removed. Nevertheless, due to the water loss in the process of bentonite mixing, the actual water content of compacted samples should be corrected before further use.

Key words: bentonite, water content, spraying method, orthogonal test, agglomerate phenomena, uniformity