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PRIETTO (2000). Gé otechnique 50, N o. 1, 99-105 T.-W. Feng, Chung Yuan Christian University, Republic of China The authors have shown the results of an experimental study on the triaxial response of artificially cemented sands. Basically, the authors prepared two groups of soil-cement specimens that were cured without stress or under stress for 48 h. Subsequent triaxial tests determined the strength and stress-strain properties of these specimens. Since most of the conclusions were drawn from the test results, it is important to know about the test method in much more detail than that reported by the authors. First, it is not known how the rapid-hardening Portland cement was mixed with the silty sand sample. Was the cement mixed with the sand in its powder state or in a slurry state? Second, it is not known how much time elapsed from the beginning of the soil-cement mixing until the end of the undercompaction. If the specimens were made in six sub-layers by the under-compaction method, the bottom sub-layer would have more cementing bonds than other sub-layers since it was prepared first. Thus it may not be possible to obtain a homogeneous specimen by using the undercompaction method. Unlike the authors' description, the writer believes that significant cementing bonds would have been formed in the specimens of the second group (cured under stress) before they were consolidated, especially when the rapid-hardening Portland cement was used. Third, it is not known whether both groups of specimens were connected to the drainage line during curing. It can be seen from Table 1 that the specimens cured without stress have lower water contents and degrees of saturation than those of the specimens cured with stress. The differences in the water content and the degree of saturation can lead to some differences in the developed cementing bonds. There is no doubt that the specimens cured without stress should be weaker than the specimens cured under stress. The main reason for this is that the specimens cured under stress will have undergone volume reduction at the beginning of curing and therefore are denser than the specimens cured without stress before shearing. This is evidenced by the stress-strain curves and the curves of volumetric strain against axial strain for the two specimens sheared under 50 kPa of consolidation pressure (Figs 1(a) and 1(b)). The stress-strain curve of the specimen cured under stress shows a large-strain principal stress difference of 310 kPa, whereas the stress-strain curve of the specimen cured without stress shows a large-strain principal stress difference of 200 kPa. The curve of volumetric strain against axial strain for the specimen cured under stress is still climbing at an axial strain of 6%, whereas that for the specimen cured without stress has already levelled off at this strain. Furthermore, the volumetric strain of the specimen cured under stress is larger than that of the specimen cured without stress. These observations all indicate that the specimen cured and sheared under 50 k...

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