前言不饱和土的问题,简单地说,在像日本这样多雨、潮湿,地基地下水位高的地方可看作特殊问题,不当作常见的问题来处理。在日本,饱和度低的土只在筑坝填土中看到,然而这也仅在施工后由于降雨而接近于饱和状态。因此,在外国半干燥地区或者干燥地区常见的由于土吸水引起地基急剧的下沉或者由于吸湿而引起粘土膨胀这样的工程土质学上的巨大问题可以说在日本是罕见的。可是,若是饱和度稍低于100%,在土的孔隙中产生气泡而孔隙水压为负的话,不饱和土的范围扩大,许多问题就成为不饱和土的问题。例如:作为饱和粘土的非排水强度试验所广为利用的单轴压缩试验里也在土样中由于取样伴随应力的解除而发生负的孔 Foreword The problem of unsaturated soil, simply put, can be seen as a special problem in areas where groundwater level is high, such as Japan, where it is rainy and humid, and it is not treated as a common problem. In Japan, low-saturated soils are only seen in dam filling, but this is only due to rainfall and close to saturation after construction. Therefore, the huge geotechnical problems of engineering, such as the sudden sinking of foundations due to water absorption in soil or the swelling of clay due to moisture absorption, which are common in semi-dry regions or dry regions in foreign countries, can be said to be rare in Japan. However, if the saturation is slightly less than 100%, air bubbles are generated in the pores of soil and the pore water pressure is negative, and the range of unsaturated soils is enlarged, and many problems become problems of unsaturated soils. For example, in a uniaxial compression test that is widely used as a non-drainage strength test for saturated clay, a negative hole is also generated in the soil sample due to the cancellation of the sample accompanying stress.