The Effect of Placement Method on the Response of Soil Stress Gages

摘要

One of the most severe problems in laboratory or field studies of ground shock in soils is the measurement of earth pressures, since measured results are often erratic. These erratic results may result from the way the gage is placed in the soil rather than from the gage itself. This study is an investigation of the effect of several arbitrarily chosen placement methods on the static response of SE (steel-epoxy) soil stress gages in dense sand and stiff clay. It illustrates that the way the gage is placed has a significant influence on both the overregistration ratio and the scatter of the data about the mean. Results of this study indicate that, for placement methods similar to those used, measurement of stress magnitude with a single gage is a practical impossibility and that, if accuracy within plus or minus 20 percent of the true stress is desired, the average of at least three measurements (corrected for over- and underregistration) should be used. A further result of this study is a proposed calibration method to determine statistically the overregistration ratio and confidence interval on the mean for a given gage in a given soil using a particular placement procedure in order that these parameters may be used to predict the over- or underregistration of the buried gage in a virgin loaded test specimen. Although not directly applicable to the main objective of this study, information was also obtained on the effect of placement method on response during repetitive loading. The data, presented in an appendix, indicate that overregistration ratio and confidence interval for sand tests decrease with repetitive loading. (Author)