In an on-going research project with the NJDOT, we have instrumented an integral bridge and have been gathering data every two hours for the past two years. We found that there is a significant pressure built-up in the soil behind the abutment. We have reported the built-up to the NJDOT, however our project does not allow for an in-depth analysis of the mechanics that are responsible for the development of the high pressures. We have identified at least four mechanisms responsible for the increase in the pressure: 1) strain ratcheting (or the plastic accumulation of strain) due to the cyclic loading of the soil; 2) a flow of the sand particles during the daily and seasonal cyclic loading; 3) the presence of frozen ground; and 4) possible failure of a soil wedge during the active pressure periods of the winter months which may be shifting the equilibrium position during every season. In order to recommend design parameters for the correct pressure distribution and magnitude, we must understand the pressure development mechanisms. This is of vast and immediate importance to the design community, considering that the construction of integral abutments is becoming widespread.