You are invited to attend a workshop on non-intrusive 3D levee imaging in St. Louis, MO. This workshop is hosted by the Natural Hazards Engineering Research Infrastructure Equipment Facility at the University of Texas at Austin (NHERI@UTexas). The workshop will be held from 8 AM – 3:00 PM on Friday, 11 November 2016. The workshop will include presentations on NHERI@UTexas equipment and non-intrusive levee imaging, followed by a field demonstration of a proof-of-concept 3D imaging study on the Mel-Price Wood River levee. During the demonstration, NHERI@UTexas equipment will be used to collect a dataset of 3-component, 3-dimensional waveforms that can be processed for 3D levee imaging purposes via full-waveform inversion. Travel support is available for a number of participants. Preference will be given to those interested in submitting proposals to the Engineering for Natural Hazards (ENH) program of NSF.
Much of the Mel-Price Wood River levee is a sand core/clay cap levee, which sits on top of a relatively thin clay blanket underlain by a sand aquifer. During flooding events, underseepage through the sand foundation soils causes high hydraulic gradients under the levee and sand boils to develop on the dry side. Extensive characterization of the levee and foundation soils has been completed, including over 50 CPTs, over 100 borings/SPT, 100s of hand probes, and numerous pump tests. Foundation soil testing has revealed a heterogeneous mixture of sands/gravelly sands, including seams of silts, and at deeper depths, some cobbles and boulders. A number of relief wells were originally installed to prevent piping under the levee. However, these were not completely effective at eliminating sand boils during large flooding events. A number of alternatives, including a seepage cut-off wall, seepage berms, and pressure relief wells have been considered. Through a risk analysis, pressure relief wells were determined to be the most efficient and effective alternative and designs for this remediation are currently being generated. Further understanding of the overall condition/integrity of the levee, as well as the location(s) of the high and low permeability seams beneath the levee would aid in the design of the relief wells to effectively limit piping under the levee during flooding events. In an attempt to provide better 2D imaging of the levee, both pseudo 2D MASW and resistivity surveys were recently conducted by Dr. Wood and Dr. Bernhardt along the crest and on either side of the levee (dry and wet sides) for approximately a 4-km section. It is desirable to compare the results from a true 3D imaging survey with those developed using pseudo 2D methods.
The NHERI@UTexas Levee Imaging Workshop will highlight a potential use of NHERI@UTexas equipment for true 3D non-intrusive imaging of geotechnical systems via full waveform inversion. Specifically, during the workshop, we will use the urban, mobile, hydraulic shaker Thumper to generate small-strain dynamic vertical and horizontal loading on the ground surface at many locations on the crest and toe(s) of the levee. The response of the levee will be recorded using a combination of hundreds of vertical and three-component geophones deployed in a dense grid over the crest, slopes and toes of the levee. The waveforms recorded from this testing will be provided to all workshop participants and other interested researchers to use in full waveform inversion studies to develop 3D models of the levee and underlying soil deposits.
Those with ideas about small, proof-of-concept tests that could piggyback on the levee imaging workshop in order to generate preliminary proposal data are encouraged to contact us in advance of the workshop. Please contact Farnyuh Menq (firstname.lastname@example.org), NHERI@UTexas Site Operations Manager, with any questions regarding the workshop, piggyback proof-of-concept tests, or the equipment facility.
Special thanks to our colleagues Clinton Wood and Michelle Bernhardt from the University of Arkansas who have helped with site selection and logistics for the workshop, and the U.S. Army Corps of Engineers and Wood River Drainage & Levee District for allowing access to the Mel-Price Wood River levee.
Please contact us if you have any questions regarding the workshop.
Thank you for your interest. Registration for this event has closed.