Assessing confined and semi-confined compression curves of highly calcareous remolded soil amended with farmyard manure

Confined and semi-confined compression curves of a highly calcareous remolded soil amended with farmyard manure (FYM) from dairy cattle were investigated. The samples were collected from the topsoil of the experimental plots where FYM had been added to the soil at four application rates (0, 25, 50 and 100 Mg ha−1) for 7 years. Large remolded specimens were prepared by applying 100 kPa load at 17.1% and 20.9% dry basis moisture contents. The center section of the preloaded soil specimen was firstly submitted to a 50 mm diameter plate for plate sinkage test (PST). One cylindrical sample was also immediately cored for confined compression test (CCT). The S-shaped curves were observed with the CCT, whereas the bi-linear form was obtained with the PST. In the CCT, the S-shaped form was more obvious at the higher moisture content. The results revealed that the moisture content and the application rate of FYM influenced the start and end points and precompaction stress of compression curve for PST. Moreover, the moisture content and the application rate of FYM affected the end point and the compression index (Cc) in the case of CCT. However, it was concluded that the overall trend in compression curve only depends on the type of test conducted.