Dynamic Behaviour of Soil (I)

High Speed Compression Test

Abstract

Although the farm equipments such as the tillage tools and the tractor wheels act dynamic force upon the soils, the dynamic resistances of soils have not been tested and have been merely analogized with the static test data. For the purpose to know the speed effects on the fractures of the soils, the uni-axial high speed compression tests, varying the compression speed 0.1-300cm/sec, are done by the authors. The stresses and straines are recorded with the strain-gauge and oscillograph (Fig. 1).
The test results are as follows: (1) The slopes of stress-strain curves increase with the increasing speed, but more than a constant speed decrease. The higher the speed, the greater strain occures at which the soil fractures (Fig. 2). (2) At high speed the fracture phenomenon of the soils are due to the shearing same to the static tests (Fig. 3). (3) The fracture stress σ increases with log δ to a certain speed, and more than this speed σ decreases. (Fig. 4) These phenomenon are caused upon that the non-linear σ-ε relation gives the varying strain wave propagation speed c and yields the critical velocity at which the plastic modulus dσ/dε and c reach to zero and leads to rapid fracture by the localized strain.
These test results may offer the optimum speed of tool to give the least resistance, and to give the greatest traction and support of the tractor wheel.