Seismic Approach to Quality Management of HMA
MnDOT Contract No. 1034287
Federal Project Number: TPF-5 (341)
Execution: January, 2020 - December, 2021
PROJECT PROGRESS (June, 2020)
Summary

  • Acquisition System Being Constructed (16-bit max. 96-channel AD converter)

    The system is under construction and scheduled for a field test in June-July by using the MEMS microphone receiver array used for
    SYS-RYD-2019.   


    Thickness (H) of HMA layer can be evaluated from the same Lamb-wave dispersion curve (A0) that is used to evaluate the shear-wave
    velocity (Vs).  On the other hand, it can also be evaluated from the spectral characteristics of obtained seismic data through the Impact
    Echo (IE) method.  Both approaches are examined during the month of June, 2020.  

    In theory, thickness of HMA layer (H) can be measured by the same Lamb dispersion curve, the fundamental anti-symmetric (A0) mode,
    that is used to evaluate the shear-wave velocity (Vs) of the layer.  An A0 curve consists of a curved part that has increasing phase
    velocity with frequency  and occurs at the low-frequency side of the curve (e.g., 1-10 kHz) and a relatively flat part with a fairly constant
    phase velocity that occurs at the higher-frequency side of the curve (e.g., 10-50 kHz).  The constant phase velocity of the curve
    corresponds to the Rayleigh-wave velocity (VR) of the HMA layer, which is about 92% of the shear-velocity (Vs) for the common range
    of Poisson’s ratio (e.g., 0.15-0.35).  For a given HMA layer of VR, the onset frequency of the curved part from the flat part of the curve
    changes with the thickness (H) of the layer; i.e., the thicker layer will result in the lower onset frequency.  In consequence, the overall
    shape of the curved part will also change with H.  All these properties of A0 curve are graphically illustrated in this report.  

    Conventional seismic measurements through contact approach (e.g., accelerometer) well depicted both curved and flat parts of A0
    curve.  However, the non-contact rolling measurements by using MEMS microphones did not show clear definition of the curved part
    although they delineated the flat part with superb quality.  It is believed that this can be closely related to the spectral characteristics of
    the light impact source that tends to generate more energy at higher frequencies (e.g., 10-50 kHz).  This, however, will be verified soon
    in the near-future when more microphone data sets are collected by using multiple impact sources of different impact energy.  However,
    the phenomenon may also be related to the near-field effect of surface waves as well as attenuation properties of the pavement layer.
      
    In this report, these two aspects (i.e., near-field effect and attenuation property) are examined by using field data sets acquired in the
    past by using both contact (i.e., accelerometer + hammer) and non-contact (i.e., microphones + bouncing ball) approaches.

    In parallel to the Lamb curve (A0) approach to evaluate the thickness (H), another independent approach that works on the spectral
    characteristics of the measured seismic wavefields is now considered.  It is the Impact Echo (IE) approach that measures the spectral
    peak that is associated with the seismic resonance within the solid material.  The peak occurs at the resonance frequency (fr) that is
    determined by the P-wave velocity (Vp) and thickness (H or d) of the layer; i.e., = BVp / (2d) where B  (=0.96) is called a correction
    factor that slightly changes with Poisson’s ratio, but is commonly set to a constant value of 0.96.

    First, two different approaches are tested to construct the amplitude spectrum; i.e., stacking individual amplitude spectrum from each
    channel’s data [frequency-domain stacking (FDS)] and stacking all channels seismic data first and then construct the amplitude
    spectrum [time-domain stacking (TDS)] (Ryden, 2016).  It turned out TDS is far more effective than the former.  Second, the most recent
    development by Bjurstrom and Ryden (2016) that applies negative phase velocity to construct a frequency-phase velocity spectrum is
    tested.  This approach (Bjurstrom and Ryden, 2016) turned out highly effective and will be used as the main IE method in this project.

    The future plan is to apply both approaches (A0 curve and IE) to evaluate the thickness (H).  Then, both values will be used to come up
    with an average value (Have) by applying an appropriate weight to each value based on a few quality factors.
    In this report, the general scheme of the IE method is briefly explained.  Then, a synthetic seismic record is generated to be used to test
    each type of IE approach.  Finally in this report, Bjurstrom and Ryden (2016) is used for real data sets from both contact and non-
    contact approaches.


    A project to build a C++ module to read the TDMS file of seismic data saved by the acquisition system being developed at Norrfee Tech
    is launched.  The project will complete a separate C++ program that reads TDMS files and converts them into the ParkSEIS data format,
    which is the standard format for the software package being developed.    

Project Tasks | Summary (see details)

    Task 1: Project Management and Administration
    Task 2: Hardware Development (Seismic Data Acquisition System) & Testing
    Task 3: Software Development & Testing
    Task 4: Delivery and Demonstration of Seismic Data Acquisition System and Software
    Task 5: Final Report

Year 1 (2020):

Year 2 (2021):
Progress Table (Prime Contractor - Park Seismic LLC) - June, 2020