粉土改良膨胀土工程特性试验研究

Experimental study on engineering characteristics of modified expansive soil with silt

为探讨粉土改良膨胀土的工程特性,对不同粉土占比的改良膨胀土进行了击实试验、膨胀特性试验、界限含水量试验、承载比(CBR)试验和无侧限抗压试验。结果表明,掺加粉土降低了膨胀土亲水性能,改善其压实特性,粉土占比为40%时,最大干密度达到峰值。改良土的膨胀性指标显著降低,自由膨胀率可降低至24.5%,有荷膨胀率逐渐接近0;随着粉土占比的提高,改良土的CBR值得到明显提升,无侧限抗压强度先增大后减小,粉土占比为10%时,改良土无侧限抗压强度达到峰值0.87 MPa。结合连宿高速公路工程实际,利用低掺量石灰降低膨胀土塑性,使其易破碎从而提高材料拌和均匀性,对40%粉土与2.5%石灰联合改良膨胀土进行室内试验,发现石灰掺入提高了土体无侧限抗压强度,进一步抑制了土体的膨胀潜势。

Compaction test,expansive properties test,Atterberg limits test,California bearing ratio test(CBR) and unconfined compression test on modified expansive soil with different proportions of silt were carried out to investigate its engineering characteristics.It is concluded that the addition of silt reduces the hydrophilicity of expansive soil and improves its compaction characteristics.The maximum dry density reaches the peak when the proportion of silt is 40%.The swelling index of the modified soil is significantly reduced,the free expansive rate can be reduced to 24.5%,and the loaded expansive rate is gradually close to zero.With the increase of the proportion of silt,the CBR of the improved soil is significantly increased,and the unconfined compressive strength increases first and then decreases.It can be found that its unconfined compressive strength has a peak value of 0.87 MPa when the proportion of silt is 10%.Combined with the engineering practice of the Liansu expressway project,the uniformity of the mixed materials is improved by adding a small amount of line to the expansive soil to reduce its plasticity and increase its breakability.The laboratory tests were carried out on expansive soil improved by combining 40% silt and 2.5% lime.The results show that the addition of lime improves the unconfined compressive strength of the soil and further inhibits the expansion potential of the soil.