Abstract: The present disclosure provides systems and methods for determining residual tension of a target bolt. An example method may include modeling ratios of times-of-flight of longitudinal waves and times-of-flight of shear waves as a function of tension for a plurality of test bolts. The modeling may include receiving data from longitudinal wave and shear wave transducers, analyzing the data to assess certain quality characteristics, and using a machine learning algorithm to create the model. The example method may further include determining a ratio of a time-of-flight of longitudinal waves and a time-of-flight of shear waves in a target bolt. The example method may further include determining residual tension in the target bolt based on the model and the ratio of a time-of-flight of longitudinal waves and time-of-flight of shear waves in the target bolt.

Abstract: The present disclosure provides systems and methods for estimating the strength of a concrete foundation. The disclosed systems and methods can be used to estimate compressive strength of below-grade concrete without excavation. A method of estimating compressive strength may include determining compressive strength measurements corresponding to surface wave speeds for a plurality of concrete test specimens, determining a speed of surface waves in the concrete foundation, and estimating compressive strength of the concrete foundation based on the compressive strength measurements and corresponding surface wave speeds for the plurality of concrete test specimens and the speed of surface waves in the concrete foundation.