红黏土的胀缩特性及对检测压实度的影响研究

Swell-shrink behaviors of lateritic clay and their effect on test compactness

针对江西红黏土堤坝填筑工程后期检测存在的压实度变化问题,通过对同一土样进行不间断的收缩、膨胀试验,研究了自然干湿循环作用下典型红黏土压实土样的胀缩特性及机理,并对后期压实度的检测偏差进行了分析。试验结果表明:自然干湿循环作用下,压实红黏土具有明显的干缩湿胀特性;无荷载作用时,土样表现出明显的膨胀特性,绝对膨胀率随循环次数的增加而增大,最大膨胀率达12.88%;有荷载作用时,随循环次数的增加表现出压缩特征,且荷载越大,压缩特征越明显。红黏土工程后期压实度的检测结果较施工过程有较大偏差,且不同干湿状态时检测的结果也有明显差异,在后期检测评定中应予以考虑,同时提出了减小偏差的建议。

Aiming at the problem that the compactness of earthworks in Jiangxi varies in the later tests on lateritic clay embankment, this study has explored swell-shrink properties and mechanism of typical compacted lateritic clays under natural dry-wet cycling by applying a continuous swell-shrink procedure on the same soil sample, and conducted an analysis on the biases of compactness tests. The results indicate that in the case of natural dry-wet cycling, compacted lateritic clay shows significant shrinkage and swell. When no load was applied, the soil sample swelled obviously, and its absolute swell ratio increased with an increase in cycling times, reaching a peak swell ratio of 12.88%. Application of loads made a soil sample compressed： the greater load was applied, the more significant the compression was; an increase in cycling times under loading condition caused greater compression. Thus, in assessing construction quality, we must consider that compactness tests of lateritic clay earthworks performed in the later stages have biases significantly greater than those tested in the initial stage at the time of construction. In addition, similar biases will occur if dry-wet cycles are applied. A method for reducing the biases is suggested in this paper.