新乡地区改良膨胀土路用性能研究

Research on road performance of improved expansive soil in Xinxiang area

为减小膨胀土对公路工程的危害,采用粉砂土和聚乙烯醇(PVA)纤维对新乡地区弱膨胀土进行改良,研究了改良前后膨胀土的路用性能;通过加州承载比(CBR)试验、冻融循环试验、无侧限抗压强度试验,研究了不同试样的膨胀率、CBR以及冻融循环对无侧限抗压强度的影响规律。结果表明:素膨胀土、30%粉砂土改良膨胀土、30%粉砂土+0.2%PVA纤维改良膨胀土的膨胀率随压实度的增大而增大,随含水率的增大而减小;CBR随压实度的增大而增大,随含水率的增大呈先增大后减小的趋势;30%粉砂土+0.2%PVA纤维对膨胀土的改良效果最好,最佳含水率时膨胀率最多降低59.76%,CBR最大提升467%;随着冻融循环次数增加,膨胀土的无侧限抗压强度不断减小并趋于平稳,其中第1次冻融循环对土的强度影响最大;PVA纤维的掺入使土体经历冻融循环后的残余强度仍大于初始状态下的素膨胀土,且土体应力-应变曲线由软化型转变为弱软化型;粉砂土和PVA纤维能够有效改善膨胀土的不良性质,显著提升其承载能力及抗冻性。

In order to reduce the harm of expansive soil to highway engineering,silt and polyvinyl alcohol(PVA)fiber were used to improve the weak expansive soil in Xinxiang area,and the road performance of the expansive soil before and after improvement was studied.Through the California bearing ratio(CBR)test,freeze-thaw cycle test and unconfined compressive strength test,the influence rules of expansion rate,CBR and freeze-thaw cycle on unconfined compressive strength of different samples were studied.The results show that the expansion ratios of plain expansive soil,30%silt improved expansive soil and 30%silt+0.2%PVA fiber improved expansive soil increase with the increase of compactness and decrease with the increase of water content.CBR increases with the increase of compactness and increases first and then decreases with the increase of water content.30%silt+0.2%PVA fiber has the best effect on improving expansive soil.At the best water content,the expansion rate can be reduced by 59.76%and the CBR can be increased by 467%.With the increase of freeze-thaw cycles,the unconfined compressive strength of expansive soils decreases and tends to be stable,and the first freeze-thaw cycle has the greatest impact on the strength of soils.With the addition of PVA fibers,the residual strength of soil after freeze-thaw cycles is still greater than that of the original plain expansive soil,and the stress-strain curve of the soil changes from softening to weakening.Silt and PVA fibers can effectively improve the undesirable properties of expansive soil and significantly improve its bearing capacity and frost resistance.