膨胀土CBR强度特性机制分析

Characteristics and mechanism of California bearing ratio of expansive soils

以在建的周集—六安高速公路为依托工程,采集典型弱、中膨胀土开展系统的试验研究,探讨了膨胀土CBR强度随含水率、击实功和膨胀潜势的变化规律。试验研究表明:CBR峰值含水率要大于最优含水率,且膨胀潜势越高,击实功越大,CBR峰值含水率与最优含水率的差值越大。结合非饱和土气水状态理论,分析了膨胀土CBR强度特性的内在机制。研究发现,CBR强度特性的上述规律性,主要是由不同饱和度条件下膨胀土所处的气水状态所决定的。当饱和度小于界限饱和度时,土体处于非饱和状态,CBR强度随饱和度的增加呈指数增长,说明膨胀土的固有特性对CBR强度的影响很大;当饱和度大于等于界限饱和度时,膨胀土强度特性与饱和土类似,CBR强度主要受干密度控制。

The influence of moisture content, compacting energy and swelling potential grade on California bearing ratio（CBR） of expansive soils is experimentally studied. It is found that the moisture content of maximum CBR is always higher than the optimum moisture content. The difference increases as the compacting energy or swelling potential grade increase. The unsaturated soils theory is applied to explain these characteristics. The regularity is due to the different gas-water phases of expansive soils with different saturation degrees. When the saturation degree is less than the boundary saturation ratio, the CBR value increase assumes the exponential relationship along with the increment of saturation degree. But when the saturation degree is more than the boundary value, the strength property is similar with saturated soil and the CBR value is controlled by the dry density.