水泥改性膨胀土的非饱和强度试验研究

改性膨胀土的主要目的是减小膨胀土的膨胀潜势和提高膨胀土的强度。选取南水北调中线工程河南南阳段膨胀土,采用非饱和直剪仪进行素土与水泥改性土控制吸力条件下的直剪试验。试验表明,3%的水泥掺量使得膨胀土的自由膨胀率由51%下降到30%。在不同的基质吸力和竖向压力下素土试样由于结构性遭到彻底的破坏应力应变关系表现为应变硬化特性,而水泥改性膨胀土的应力应变关系表现为应变软化特性。水泥改性在提高膨胀土饱和抗剪强度参数c′、φ′的同时,也使得非饱和抗剪强度参数φb有所增大。试验成果为膨胀土现场水泥改性的设计施工提供了科学的、有价值的依据。

Study on Unsaturated Shear Strength Characteristics of Cement-stabilized Expansive Soil

The purposes for the modification of expansive soil are decreasing the expansive potential and improving the shear strength.The expansive soil in Nanyang section of Median-line South-to-North Water Transfer Project is selected to perform the unsaturated direct shear test of soils before and after cement modification.The results show that the free expansive ratio is reduced from 51% to 30% when the expansive soil is blended with cement of 3%.The stress-strain curves of the remoulded expansive soil samples are strain hardening owing to the complete damage of the soil structure under different matric suctions and vertical stresses,while the stress-strain curves of the cement-stabilized expansive soil samples are strain softening.The saturated shear strength parameters c′ and φ′ of the expansive soil are increased after cement modification,while the unsaturated shear strength parameter φb is also improved.A scientific and valuable basis is provided for the design and construction of site cement modification of expansive soils.