The Effect of Penetration Rate on the Strength of Remolded Clay and Sand Samples

Abstract

The penetration rate effect on the strength of clay and sand was studied by constant velocity penetration tests performed with various velocities up to 2.662 f.p.s. (81.14 cm/s). The clay and sand targets were of various strengths and moisture contents. The construction of the penetrometer is similar to that used in static tests, and in each test the cone resistance, sleeve friction, and penetration velocity were recorded.Experimental results indicated that for granular soils the effects of penetration velocity on cone and sleeve friction resistances are insignificant, whereas, for cohesive soils, the increase in penetration velocity causes an increase in the cone and friction resistances. It is found that for the cohesive soils the ratio of dynamic to static strength is directly proportional to the logarithm of the penetration velocity ratio. The proportionality constant of this relationship defined as soil viscosity coefficient depends on the physical properties of the soil and the soil strength and its value increases as the strength of the soil decreases. For the tested soils various values of the soil viscosity coefficient are proposed for different strength ranges. The validity of the analytical relationship is established for penetration velocities ranging from 0.0044 f.p.s. (0.13 cm/s) to 18 f.p.s. (550 cm/s).