南阳中膨胀土水泥改性的室内试验研究

Laboratory Experimental Testing of Cement Modified Nanyang Medium Expansive Soils

取南水北调中线工程南阳段自由膨胀率77%的中膨胀土,开展了一系列不同水泥掺灰率和不同龄期下,压实度为98%试样的物理力学特性试验。通过对素膨胀土与改性膨胀土的胀缩性、界限含水率、级配及无侧限抗压强度的对比,揭示了掺灰率及养护龄期对膨胀土改性效果的影响。试验结果表明:(1)随掺灰率的增加,改性膨胀土的胀缩性指标及反映黏土亲水性的液限和塑性指数均降低、胶粒含量减小、级配曲线随趋于平缓、无侧限抗压强度和弹性模量增加;合理的掺灰率应取6%;(2)随养护龄期的增加,胀缩性指标、液限、塑性指数、胶粒含量减小,无侧限抗压强度和弹性模量则增大。

A cement modified Nanyang medium expansive soil with a free expansion ratio of 77% is extensively studied in the laboratory conditions under a degree of compaction of 98 %. The expansive properties of modified and unmodified expansive soil samples, such as, free expansion ratio, shrink-swelling indices, Atterberg Limits, grain size distribution and unconfined compressive strength, are tested with different cement ratios and curing ages. The following conclusions can be drawn： 1） with the increase of cement content, the liquid limit and plastic index, which are the indices of shrinkage-swell and plasticity of modified expansive soils, are reduced. The clay content in soil samples is also reduced. A flat gradation curve is observed. The uncon- fined compressive strength and elastic modulus are increased. The optimum cement ratio is tested to be 6%. 2） with the increase of curing time, the shrinkage-swelling indices, liquid limit, plasticity index and clay content are reduced and the uncon- fined compressive strength as well as elastic modulus are increased.