Based on the shear failure mechanism, hydraulic fracturing criteria are extended to three dimensional stress state. According to the situation of the directions of borehole and major principal stress axes, three equations can be derived for three dimensional hydraulic fracturing problems. By comparing these equations, a single criterion is selected for hydraulic fracturing pressure in cohesive soils. The criterion is a function of maximum principal stress, minimum principal stress and soil parameters in UU conditions. The equation indicates that with any increase in maximim principal stress, hydraulic fracturing pressure decreases. In order to prove the integrity of the criteria, laboratory tests are performed on compacted cubical specimens using true a triaxial apparatus. The shape and direction of fractures are determined by injecting colored water after fracture initiation. It is found that the direction of fractures are perpendicular to the o1 plane.

Artificial ground freezing methods have been applied to geotechnical construction projects for stabilizing earth materials and controlling water seepage into the ground. However, this can result in frost heaving and causes the same engineering problems as encountered with the natural freezing of soil. In natural freezing, the ground freezes from the surface downward. When artificial ground freezing is applied at a deep location, however, freezing is limited locally. The soil condition differs between them as follows: Natural freezing - unsaturated and without overburden pressure. Artificial freezing -- saturated and under overburden pressure. The authors investigated the practical application of artificial ground freezing and examined the frost behaviour of a saturated soil under overburden pressure. This paper presents the results obtained from experiments concerning frost heaving and discusses frost heaving at the freezing site.

Polyol을 주성분으로 하는 A액과 MDI계 isocyanate로 구성된 B약을 배합비와 배합속도를 각각 1:2에서 1:4까지, 300rpm에서 900rpm까지 변화시키면서 혼합하였다. 생성된 foamed polyurethane은 600rpm의 배합속도에서 배합비가 1:2에서 1:4로 감소함에 따라 발포율이 증가하는 현상을 보였다. 300rpm의 배합속도에서는 거의 발포가 되지 않았음, 900rpm의 배합속도에서는 발포는 되었으나 brittle한 물성을 보였다. 열변형온도 및 하중에 대한 변형율은 600rpm에서 1:2에서 1:3의 배율시 가장 우수한 것으로 관찰되었다.