重塑黄土的强度影响因素及基于核磁共振的微观解释

Influencing Factors of Remolded Loess Intensity and Microscopic Interpretation Based on Nuclear Magnetic Resonance

黄土的抗剪强度特性影响着黄土地区边坡和路基等的稳定性,抗剪强度特性与土体的含水率和干密度密切相关。通过制备不同含水率和干密度的重塑黄土试样,通过室内直剪试验和核磁共振测试对重塑黄土的抗剪强度特性进行研究。研究结果表明,在低含水率的情况下,重塑黄土应力应变曲线有峰值点存在,呈现应变软化特性;在高含水率的情况下,应力应变曲线没有明显峰值,呈现应变硬化特性。随着土样含水率变大,黏聚力显著下降,内摩擦角变化规律不明显;随着土样干密度变大,其黏聚力增大。随后采用核磁共振测试技术对上述不同含水率和干密度状态的环刀样开展了含水量分布的测试,测试结果进一步从微观层面上解释了重塑黄土抗剪强度参数变化的规律。

The shear strength characteristics of loess have an influence on the stability of slope and roadbed in loess area,and shear strength characteristics closely related to the water content and dry density of the soil.The specimens of remolded loess with different water content and dry density are prepared,and the shear strength characteristics of the remolded loess are studied by direct shear test and nuclear magnetic resonance test.The results show that at low water content,the stress-strain curve has remolded peak point is present,which shows strain softening properties;at high moisture content,the stress-strain curve has no obvious peak,showing the strain hardening properties/characteristics.With the increase of soil moisture content,the cohesive force decreased significantly and the variation rule of internal friction angle is not obvious;as the dry density of soil sample increased,the cohesion increased.Followed by NMR testing of the above-mentioned different moisture content and dry density state ring knife-like water content distribution carried out the test,and the test results further explain the laws remolded shear strength parameters from the micro level.