分散性土单轴抗拉强度影响因素试验研究

为准确测定土体的抗拉强度,采用自行研制的制样模具和电动式单轴拉伸仪,对分散性土单轴抗拉强度影响因素及其断裂机理进行分析研究,并以非分散性土和过渡性土作为对照。试验结果表明：试样长径比取2.5,拉伸速率取0.8 mm/min可有效避免端部效应和自重影响。分散性土、非分散性土和过渡性土的单轴抗拉强度随含水率的增大而减小,随压实度和黏粒含量的增大而增大,其变化趋势基本相同。与非分散性土和过渡性土的单轴抗拉强度相比,分散性土的单轴抗拉强度显著低于非分散性土和过渡性土。究其原因,主要是分散性土中含有一定量的钠离子和pH较高,使得土颗粒表面的扩散双电层厚度增加,颗粒间的引力降低,斥力增大,宏观表现为单轴抗拉强度降低。

Influencing factors for uniaxial tensile strength of dispersive soils

In order to measure the tensile strength accurately, by using the self-developed moulds and the electric uniaxial tensile tester and comparing the transitional soils with the non-dispersive ones, the influencing factors for tensile strength and fracture mechanism of dispersive soils are studied. The experimental results show that the tester can effectively avoid the end effect and the influence of weight if the length-diameter aspect ratio is 2.5 and the tensile rate is 0.8 mm/min. The uniaxial tensile strengths of the three kinds of soil samples all decrease with the increase of the moisture content and increase with the increase of compactness and clay content. The uniaxial tensile strength of the dispersive soils is lower than that of the transitional soils and non-dispersive soils. The main reasons are that the dispersive soils have a certain amount of Na⁺ and alkaline pH. These factors make the diffusion double layers thicker and lead to smaller gravitational and larger repulsion among particles. Thus the tensile strength becomes lower macroscopically.