Correlation Between MWD Compound Parameters and SPT N-values in Nebraska-PPT Presentation

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The study investigated whether compound parameters derived from Measurement While Drilling (MWD) data can predict Standard Penetration Test (SPT) N-values in Nebraska’s fine-grained soils, including low- and high-plasticity silts and clays. MWD records drilling responses such as thrust, torque, rotation speed, penetration rate, and fluid pressure.<br /><br />Researchers compared MWD averages from three depth intervals: above the SPT test, at the same depth, and below it. They also cleaned noisy data caused by drill-bit changes and excluded SPT refusal results, which had been artificially capped at N=100 and increased scatter.<br /><br />The strongest predictors of SPT N-values were the Somerton Index and Soil-Rock Resistance. Averaging MWD data over the same depth interval as the SPT test produced the most reliable correlations, even though the SPT process may disturb the soil. Both 12-inch and 18-inch averaging intervals were usable, provided the interval was applied consistently.<br /><br />The findings show that careful data cleaning and exclusion of refusal points are important for improving correlation quality. However, the results are based on a limited dataset of fine-grained soils. The authors recommend larger studies and separate correlations for different soil types.

Keywords

Measurement While Drilling

MWD

SPT N-values

fine-grained soils

Nebraska soils

Somerton Index

Soil-Rock Resistance

data cleaning

geotechnical correlation

soil classification