聚乙烯醇水凝胶改良红黏土强度特性研究

Study on Strength Characteristics of Red Clay Modified by Polyvinyl Alcohol Hydrogel

摘要:

以红黏土为研究对象,聚乙烯醇(PVA)为改良材料,通过直剪和无侧向抗压强度试验,研究了不同PVA浓度和养护龄期对红黏土强度的影响,并利用扫描电镜观察了改良土的微观结构。结果表明:在各养护龄期相同的条件下,红黏土的黏聚力和无侧限抗压强度均随着PVA浓度增加呈先增大后减小的趋势,内摩擦角随着PVA浓度的增加未呈现出明显的变化规律,但均大于红黏土的内摩擦角。取浓度为3%PVA改良红黏土抗剪强度和无侧限抗压强度的效果比较理想。微观测试表明:PVA与土颗粒反应,形成高弹性、高强度的立体丝网状结构,搭接于孔隙间。低浓度的PVA所形成的网状结构不完整,黏结力弱,随着浓度的提升,网状结构逐渐完整,更能有效限制土颗粒的移动,从而提高土体的抗剪和抗压强度。然而,较高浓度的PVA导致水凝胶黏度增大,影响其与红黏土的均匀混合,不利于PVA与土颗粒接触,减弱了网状结构与土颗粒的连接,反而降低黏聚力和无侧限抗压强度。

Abstract:

Taking red clay as the research object and polyvinyl alcohol as the improved material, the effects of different polyrinyl alcohol (PVA) concentrations and curing ages on the strength of red clay were studied by direct shear and non-lateral compressive strength tests, and the microstructure of the improved soil was observed by scanning electron microscopy. The results show that under the same conditions of each curing age, the cohesion and unconfined compressive strength of red clay increase first and then decrease with the increase of PVA concentration. The internal friction angle does not show obvious variation with the increase of PVA concentration, but it is greater than the internal friction angle of red clay. The effect of improving the shear strength and unconfined compressive strength of red clay with 3% PVA is ideal. Microscopic tests show that PVA reacts with soil particles to form a three-dimensional mesh structure with high elasticity and high strength, which is lapped between pores. The network structure formed by low concentration of PVA is incomplete and the cohesive force is weak. With the increase of concentration, the network structure is gradually complete, which can effectively limit the movement of soil particles, so as to improve the shear and compressive strength of soil. However, the higher concentration of PVA leads to the increase of the viscosity of the hydrogel, which affects its uniform mixing with red clay, which is not conducive to the contact between PVA and soil particles, wea-kens the connection between the network structure and soil particles, and reduces the cohesion and unconfined compressive strength.