聚丙烯纤维加筋水泥土的强度特性试验研究

发布时间：2018-01-25 19:22

本文关键词： 聚丙烯纤维水泥土无侧限抗压强度三轴试验干湿循环试验　出处：《广东工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：纤维加筋土作为一种新型的土工材料,其具有抗剪、抗裂和抗腐蚀性好等优点,常被用于加固路基和挡土墙等结构,是目前加筋土技术的热点。本文以广州南沙固化淤泥为研究对象,以纤维含量、纤维长度以及水泥掺量等因素对土体加固效果缺乏统一认识为背景,在目前加筋土强度理论基础上进一步探究以上因素对纤维加筋水泥土强度及变形的影响规律,并且研究其强度在滨海条件下随干湿循环次数的变化关系。本文在前期水泥基外掺剂对南沙淤泥力学性质影响研究的基础上,进一步研究聚丙烯纤维加筋水泥土的强度特性及变形特性,为其实际工程提供重要的理论支撑。(1)通过基本的室内土工试验测出了广州南沙淤泥的基本物理力学指标,并且简要介绍了聚丙烯纤维的物理、化学和力学性质。(2)详细介绍了纤维对土体的强度增强机理,其机理可归纳为“弯曲机理”和“交织机理”,土体的物理力学性质在两者的共同作用下得到明显的改善。(3)通过单掺试验研究分析了纤维含量、纤维长度以及水泥掺量对纤维水泥土无侧限抗压强度的影响,并且与前人的研究成果进行了对比分析;通过电镜扫描试验和结合纤维加筋土的强度理论分析了纤维水泥土强度增强的机理以及对其破坏形态进行了初步的分析;通过正交试验得出了纤维水泥土的优方案。试验结果表明:纤维水泥土的无侧限抗压强度随纤维含量、纤维长度以及水泥掺量的增加都有了一定程度的增强,但纤维长度对水泥土强度的增强作用没有纤维含量和水泥掺量明显;纤维的掺入能够阻止水泥土在受压破坏过程中裂缝的扩展;纤维水泥土的优方案为:纤维含量为0.4%,纤维长度为3mm,水泥含量为18%。(4)通过不固结不排水三轴剪切试验,研究分析了在不同纤维含量下纤维水泥土的应力-应变特征,得出了不同纤维含量下纤维水泥土粘聚力和内摩擦角的变化特征;建立了不同纤维含量下土体的本构模型,通过试验求出了相关模型的参数。试验结果表明:纤维的掺入能够在一定程度上增大水泥土的峰值应力和破坏应变,并且随着纤维含量的增加,水泥土的粘聚力得到明显的提高,而内摩擦角的变化幅度则不大。(5)对纤维水泥土在滨海条件下进行干湿循环试验,研究分析了不同纤维含量下纤维水泥土的无侧限抗压强度、粘聚力和内摩擦角随干湿循化次数的变化关系,得出了干湿循环条件下纤维水泥土强度特性的变化规律。试验结果表明:同一纤维含量下,纤维水泥土的无侧限抗压强度和粘聚力均随干湿循环次数的增加出现先增大后减小的趋势;同一干湿循环次数下,纤维水泥土的无侧限抗压强度和粘聚力均随纤维含量的增加而增大。
[Abstract]:Fiber reinforced soil, as a new type of geotechnical material, has the advantages of good shear resistance, crack resistance and corrosion resistance. It is often used to strengthen subgrade and retaining wall and other structures. This paper takes the solidified silt of Nansha in Guangzhou as the research object, and takes the fiber content, fiber length and cement content as the background for the lack of a unified understanding of the soil reinforcement effect. On the basis of the current strength theory of reinforced soil, the influence of the above factors on the strength and deformation of fiber reinforced cement-soil is further explored. The relationship between the strength and the number of dry and wet cycles in coastal conditions was studied. In this paper, the influence of cement based admixture on the mechanical properties of Nansha silt was studied. The strength and deformation characteristics of cement soil reinforced with polypropylene fiber are further studied. The basic physical and mechanical indexes of Nansha silt in Guangzhou are measured through basic indoor geotechnical tests, and the physics of polypropylene fiber is briefly introduced. The mechanism of strength enhancement of fiber to soil is introduced in detail. The mechanism can be summarized as "bending mechanism" and "interwoven mechanism". The physical and mechanical properties of soil are obviously improved under the joint action of the two. (3) the fiber content is analyzed by the single admixture experiment. The influence of fiber length and cement content on the unconfined compressive strength of fiber cement soil is analyzed and compared with the previous research results. The mechanism of strength enhancement of fiber cement soil and its failure pattern were analyzed by SEM and the strength theory of fiber reinforced soil. The results show that the unconfined compressive strength of fiber cement soil increases with the increase of fiber content, fiber length and cement content. But the fiber length has no obvious enhancement effect on the strength of cement soil without fiber content and cement content. The addition of fiber can prevent the crack of cement soil from spreading in the process of compressive failure. The excellent scheme of fiber cement soil is: fiber content is 0.4, fiber length is 3 mm, cement content is 18. 4) through unconsolidated and undrained triaxial shear test. The stress-strain characteristics of fiber cement soil under different fiber content are studied and analyzed. The change characteristics of cohesive force and internal friction angle of fiber cement soil under different fiber content are obtained. The constitutive model of soil mass with different fiber content was established, and the parameters of the model were obtained by experiments. The experimental results show that the addition of fiber can increase the peak stress and failure strain of cement soil to some extent. And with the increase of fiber content, the cohesion of cement soil was obviously increased, while the change of internal friction angle was not significant.) the dry and wet cycle tests of fiber cement soil under coastal conditions were carried out. The unconfined compressive strength, cohesion and internal friction angle of fiber cement soil under different fiber content were studied and analyzed. The change law of strength characteristics of fiber cement soil under dry and wet cycling conditions is obtained. The experimental results show that the same fiber content can be obtained. The unconfined compressive strength and cohesion of fiber cement soil increase firstly and then decrease with the increase of dry and wet cycles. Under the same dry and wet cycles, the unconfined compressive strength and cohesion of fiber cement soil increase with the increase of fiber content.
【学位授予单位】：广东工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU41

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