纤维加筋固化土抗拉强度试验研究

Experimental Study on Tensile Strength of Fiber Reinforced Solidified Soil

针对水泥固化土作为简易机场道面材料时抗拉强度差、易开裂的问题,利用掺入纤维的办法来改善力学性能,采用玄武岩纤维、玻璃纤维、细聚丙烯和粗聚丙烯纤维对不同地域3种水泥固化土进行了加筋。使用路强仪和自行设计的直拉试验仪,以劈裂抗拉强度(STS)和直接抗拉强度(DTS)为评价指标,对固化土力学性能、受力破坏过程中应力应变曲线及破坏后的形态进行了分析。结果表明:水泥的加入可显著提高土样的劈裂抗拉强度和直接抗拉强度值;以劈裂抗拉强度为评价指标,玄武岩纤维最佳掺量下,西安加筋土的劈裂抗拉强度值相比水泥土增加了87%,细聚丙烯纤维掺量越高抗拉强度越高,但过高的掺量会造成试样成型困难;以直接抗拉强度为评价指标,粗、细聚丙烯纤维及混合纤维最佳掺量下,西安加筋土的直接抗拉强度值相比水泥土增加了26%;过多的纤维加入会占用土粒空间,造成纤维与纤维直接接触,减小土粒间的黏聚力;高压实度下纤维与固化土间结合更为紧密,更能发挥加筋作用;纤维的加入改善了试样的脆性破坏,且粗细混合聚丙烯纤维的改善效果最佳。纤维加筋作用显著增强了固化土的抗拉性能,用于简易机场可改善道面力学性能,增加使用寿命。

In view of poor tensile strength and easy cracking when cement solidified soil is used as pavement material for airstrip,the mechanical properties is improved by using mixing fiber,3 kinds of cement solidified soil in different regions are reinforced by adopting basalt fiber,glass fiber,fine polypropylene fiber and coarse polypropylene fiber.By using road strength meter and self-designed direct tensile tester,taking splitting tensile strength(STS)and direct tensile strength(DTS)as the evaluation indicators,the mechanical properties,stress-strain curves of solidified soil in the process of mechanical failure and the modes after failure are analyzed.The result shows that(1)the mixing of cement can improve STS and DTS of soil specimens significantly;(2)taking STS as the evaluation indicator,the STS value of Xi’an reinforced soil increased by 87%compared with that of cement soil under the optimum content of basalt fiber,and the more the fine polypropylene fiber,the higher the tensile strength,but too much mixture will result in difficult forming of specimens;(3)taking DTS as the evaluation indicator,the DTS value of Xi’an reinforced soil is 26%higher than that of cement soil under the optimum contents of coarse and fine polypropylene fiber and mixed fiber;(4)excessive fiber addition will occupy the space of soil particles,causing direct contact among fibers and reducing the cohesion among soil particles;(5)the fiber and solidified soil bond more closely under high pressure compactness,which improves the reinforcement;(6)the addition of fibers improved the brittleness failure of the specimens,and the coarse-fine mixed polypropylene fiber has the best improvement effect.The tensile properties of solidified soil are improved by fiber reinforcement,which can improve the mechanical properties of airstrip and prolong its service life.