Tensile fracture and fatigue of cement stabilized soil

Abstract

Concepts of elastic fracture mechanics are applied to an airfield pavement material. The material used to conduct the experimental work is a portland cement stabilized fine grained soil. Two primary areas of interest and one secondary area of interest are explored. The two primary fracture studies include "static" (monotonic loading) behavior and fatigue (cyclic loading) behavior. The secondary study is of a preliminary nature in that initial concepts are presented concerning how the primary studies could be applied to pavement problems. It is hypothesized that "static" fracture toughness can be related (through regression analyses) to certain compositional factors. The general form of a regression model which effectively describes the relationship is proposed and is based on a derivation using a Lennard-Jones potential energy model. The effectiveness of the model is demonstrated using experimental results. Use of the model for other materials is discussed. Stable crack growth in fatigue is described using a power law which relates the crack growth per cycle to the change in stress intensity factor in each cycle. Although statistical variability plays a significant role in the fracture of the stabilized soil, concepts are introduced which allow the use of fatigue data to describe stable crack growth as a function of the change in stress intensity factor normalized to the 'static1, mode I, critical plane strain stress intensity factor. The "static" and fatigue results are used to qualitatively describe crack growth in certain cases for which elastic solutions exist.