Study of Static and Dynamic Penetration Test Capable of Applying Pore Pressure

穿透试验是对地面进行的一种强度试验。土壤的强度取决于有效应力。强度试验必须在两种不同的有效应力下进行。然后，考虑了能从锥尖对地面某一点施加有效应力的侵彻试验。在小型储罐中对模型进行了试验。可以对模型地基施加任意的覆盖层压力。同时利用同一储槽研究了渗透过程中产生的孔隙水压力对渗透阻力的影响。结果如下：1)黏性地基侵彻试验中，侵彻速率越低，侵彻阻力越大。究其原因，是在缓慢侵彻速度下，由于产生的孔隙水压力耗散，锥尖周围地面的强度接近于排水强度。2)低空隙比时，饱和地基的静、动侵彻阻力均大于干燥地基，高空隙比时反之。其原因是由于锥尖周围的膨胀产生了孔隙水压力。(3)从锥尖处施加孔隙压力时，砂土的静、动侵彻阻力与有效应力呈线性关系，有效应力由覆盖层压力减去给定孔隙压力得到。给饱和土施加孔隙水压力时，给饱和土和干土施加孔隙空气压力时，直线的斜率是不同的。此外，坡度取决于地面抗剪的角度。

A penetration test is a kind of a strength test for a ground. A strength of a soil depends on an effective stress. Strength tests must be carried out under two different effective stresses. Then, the penetration test in which an effective stress can be given to a point in the ground from a tip of a cone, is considered. Tests were carried out for the model grounds in the small tank. An arbitrary overburden pressure can be given to the model ground. Also influence of pore water pressure generated during penetrating to penetration resistance was investigated using the same tank.The results are as follows. 1) In the penetration test for the cohesive ground, the lower the penetrating rate is, the larger the penetration resistance is. The reason is that the strength of the ground around the tip of the cone approaches the drained strength due to dissipation of generated pore water pressure when the slow penetrating rate. 2) The static and the dynamic penetration resistances for the saturated ground is larger than ones for the dried ground when low void ratio, and vice versa when high void ratio. The reason is due to generated pore water pressure by dilatancy around the tip of the cone. 3) The static and the dynamic penetration resistances for sand ground when pore pressures are given to the grounds from the tip of the cone have linear relation to the effective stress which is obtained by subtracting the given pore pressure from the overburden pressure. Slopes of the straight lines when giving pore water pressure to the saturated ground and when giving pore air pressure to the saturated and the dried ground differ from each other. Also the slope depends on the angle of the shearing resistance of the ground.