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Friday, February 24, 2017

7:30 am Registration and Continental Breakfast
8:15 am Welcome
Dean Samuel Mukasa, Ph.D.
College of Science and Engineering
University of Minnesota, Twin Cities
8:25 am Kersten Lecture
LRFD Calibration Concepts for Geotechnical Soil-Structure Systems

Richard Bathurst, P. Eng., Ph.D.
Professor of Civil Engineering
Royal Military College of Canada

The load and resistance factor design (LRFD) approach for geotechnical structures is now accepted practice in North America. Limit states design equations cast within a LRFD framework appear in design codes and design guidance documents for shallow footings, piled foundations, soil nail walls, and unreinforced and mechanically stabilized earth (MSE) retaining wall structures both in the USA and Canada. While most geotechnical engineers are confident how to use LRFD equations for the design of geotechnical structures, the concepts behind how load and resistance factors are computed are less well understood. The most recent version of the Canadian Highway Bridge Design Code and the next edition of the National Building Code of Canada (which are LRFD foundation engineering codes) incorporate the concept of “level of understanding”. The idea behind level of understanding is to reward engineers with higher resistance factors for those cases with better project-specific site information, material properties, better design models and for which the engineer has greater experience. This lecture reviews basic concepts for LRFD calibration of limit state equations for simple soil-structures. Basic concepts are demonstrated using internal stability limit states for MSE walls constructed with both polymeric and steel soil reinforcement products. The details behind the use of level of understanding at the design stage are also explained.

9:20 am Assessment of Rock Strength from Scratch Testing

Emmanuel Detournay, Ph.D.
Professor, Civil, Environmental, and Geo- Engineering
Minnesota of Minnesota, Twin Cities

The uniaxial compressive strength (UCS) is the most common measure of strength used in civil, mining, and petroleum engineering, with applications ranging from the design of underground structures in rocks to the selection of tools for mechanical excavation. The procedure to determine the UCS has been standardized by the ASTM and the ISRM. The scope of this paper stems from an effort initiated at the University of Minnesota (UMN) in the mid-nineties to build a scientific apparatus to study the cutting action of a single cutter in order to assess the dependence of the cutting force on the rock mechanical properties and on the UCS, in particular. This paper first reviews the basic aspects of the mechanics of rock cutting, with considerations given to the ductile and the brittle regimes, and to the influence of a wear flat on the magnitude of the cutting force. The paper then describes the rock strength device, as well as the test methodology. Finally, it produces compelling evidence that under conditions referred to as the ductile regime, the specific energy of cutting is well correlated with the UCS.

10:00 am Break
10:30 am Innovations in Modeling and Monitoring Technologies for Response of Deep Urban Excavations

Youssef Hashash, Ph.D.
Professor, Civil and Environmental Engineering
University of Illinois, Urbana-Champaign

Development of urban excavations requires detailed understanding of the impact of construction activities on ground deformations and on adjacent structures. This presentation describes advances in modeling and monitoring techniques to aid in control of deformations around excavations in the context of a number of excavation case histories in Boston, Chicago and San Francisco. New imaging technologies, combined more recently with social media, are used to obtain detailed records of construction activities. Advancements in wireless and networked instrumentation provide timely information on changes in movements and loads. Novel computational techniques can now take advantage of this information to learn relevant soil behavior and provide reliable estimates of excavation response where no instrumentation is available, for later excavation stages or for future excavations.

11:10 am Performance of bridges constructed using the Geosynthetic Reinforced Soil Integrated Bridge System (GRS IBS)

Daniel Alzamora, P.E.
Senior Geotechnical Engineer
Federal Highway Administration – Resource Center, Lakewood, CO

Over the past six years, the Federal Highway Administration (FHWA) has been promoting the use of the Geosynthetic Reinforced Soil Integrated Bridge System (GRS IBS) as part of the Every Day Counts initiative. GRS IBS is an innovative, accelerated bridge design option to replace many of the country’s aging small, single span bridges. GRS is defined as an engineered composite consisting of closely spaced (< 12”) alternating layers of compacted granular fill material and geosynthetic reinforcement. The Integrated Bridge System is a fast and cost effective method of bridge support that transitions the roadway into the superstructure using GRS technology and addresses the differential movement between the superstructure and the approach embankments alleviating the “bump” at the end of the bridge. This presentation will provide an overview on the reported performance of these types of structures, instrumented by FHWA researchers and others. The presentation will also discuss a summary of the types of structures and site conditions where they have been used nationally.

11:50 am Lunch
1:00 pm U-864 Counter fill- Securing a Toxic Time Bomb

Per Sparrevik, M.S.
Expert Adviser & Discipline Leader, Subsea Technology
Norwegian Geotechnical Institute, Oslo, Norway

In 1945, during the last days of the Second World War, the British Royal Navy torpedoed and sank the German submarine “U-864” north of the Norwegian city of Bergen. U-864 was dispatched to deliver war supplies to Japan, including 1,857 canisters hidden in the keel with 67 tonnes of mercury for use in weapons production. Nearly 30,000 square meters of the seabed surrounding the submarine is now contaminated by mercury. The submarine was split in two main parts with smaller debris scattered across the wreck site. The bow, which is resting in a 15° slope, is the most exposed part and geotechnical calculations have shown that the soft clay sediments in the slope are very unstable. In 2015, the Norwegian Government allocated funding for remediation and protection of the site with the Norwegian Coastal administration as the responsible authority. The first step was to stabilize the soft clay seabed near the wreck by installing a large counter fill at the foot of the slope preventing the bow from sliding deeper into the ocean at a later stage. The paper describes the slope stability problem in more detail and the purpose of the counter fill for future and final remediation including capping of the wreck site with layers of special materials.

1:40 pm Health Assessment of Levees in New Orleans

Victoria G. Bennett, Ph.D.
Assistant Professor, Civil and Environmental Engineering
Rensselaer Polytechnic Institute, Troy, NY

The integrity and reliability of levees, earthen dams and flood-control infrastructure are essential components of homeland safety. The failure of such systems due to a natural or manmade hazard such as a (hurricane) storm surge, flood, earthquake, deterioration, or terrorist attack can have monumental repercussions, sometimes with dramatic and unanticipated consequences on human life, property and the country’s economy. This paper presents the integration of affordable sensing technologies, such as satellite-based interferometric synthetic aperture radar (InSAR), for use in a new health assessment framework to monitor, manage and ensure the safety of levees and other systems of a flood-control infrastructure. Early results of applying TerraSAR-X data for widespread settlement monitoring in the New Orleans area are presented herein. Historic and newly acquired StripMap data over a 1500 km2 footprint in New Orleans have been utilized to monitor ground settlements from February 2009 to October 2014. Local measurements from GPS and ShapeAccelArrays are integrated with the satellite-based InSAR measurements to monitor the response of flood-control levees.

2:20 pm Break
2:50 pm

Case Histories

Concurrent Session 1A:

A Tale of Two Stadiums: Foundation Conditions at the New Minneapolis Sports Facilities

Gregory R. Reuter, P.E., P.G., D.GE
Principal Engineer, Geotechnical Division
American Engineering Testing, Inc., St. Paul, MN

Two different professional sports teams; two different stadiums; two completely different geotechnical conditions. The new Minnesota Twins stadium (Target Field) and the new Minnesota Vikings stadium (U.S. Bank Stadium) have both been constructed within the last 10 years. Although both stadiums are located in Minneapolis, each site represents completely different geotechnical conditions, requiring different foundation solutions. The site of the Twins ballpark overlies a deep, buried bedrock valley that had been filled with rather soft alluvial settlements during the last stage of glaciation. These soils necessitated supporting the stadium on deep driven piles, while also incorporating lightweight fill to mitigate settlement. In contrast, the playing field at the Vikings stadium lies approximately 45 feet below street level, just above the bedrock surface in this area, and was constructed over the old Metrodome site. The bedrock is relatively flat-lying and consists of the typical sequence of Platteville limestone, Decorah shale, and St. Peter Sandstone that is found elsewhere in downtown Minneapolis. The stadium is supported on spread footings and drilled shafts into the limestone. One unique feature of the stadium is the primary roof truss structure that bears within the limestone and imparts significant lateral load into the bedrock.

Concurrent Session 1B:

Anomie of Non-Uniform Pavement Foundation

Bernard I. Izevbekhai, P.E., Ph.D.
Research Operations Engineer, Office of Materials & Road Research
MnDOT, Maplewood, MN

Sinking support moments are commonly analyzed when uneven surfaces are expected to induce a moment on superstructures. A sub-surface research initiative built a two-lane 500-ft test section composed of a 15-ft jointed plain concrete pavement over an open graded aggregate base at the MnROAD facility in 2011. A sudden appearance of multiple cracking on the surface 12 months after construction necessitated a forensic evaluation. This paper discusses the responsive forensic evaluation of the extensive surface distress that was ultimately attributed to loss of support from the underlying unstable base. It elucidates how the investigation was characterized by a stepwise evaluation process ranging from non-destructive surface tests to the semi-destructive tests while reviewing design adequacy based on layer moduli analysis. It subsequently accentuates progression of testing that exposed certain routine aggregate quality tests as inadequate for prediction of base material stability while recommending other tests that may be more indicative of stability. While methods of instability prediction and avoidance are discussed, tenable remediation after loss of support has occurred are also postulated.

3:15 pm Concurrent Session 2A:

Repair of the West River Parkway Slope Failure

Michael B. Haggerty, P.E.
Senior Geotechnical Engineer
Barr Engineering, Minneapolis, MN

On June 19, 2014, after historic sustained and heavy rains in Minnesota’s Twin Cities, an approximate 10,000-square-foot section of bluffs along the Mississippi River and adjacent to West River Parkway failed. The resulting mudslide covered the parkway with over 4,000 cubic yards of debris and soil and exposed several Fairview–University of Minnesota Medical Center (UMMC) structures located at or near the bluff’s edge and a Minneapolis Park and Recreation Board (MPRB) property line. The Federal Emergency Management Agency (FEMA) officially declared the site a disaster on July 21, 2014, and Hennepin County, where the failure occurred, was added as an area eligible to receive reimbursement for disaster-related expenses. Barr Engineering was hired in mid-August 2014 to implement monitoring of the slope and the adjacent infrastructure, perform field investigations necessary for final repairs, and engineer temporary and permanent repairs. The slope repair design developed consisted of five retaining walls, soil nails, new stormwater infrastructure, and erosion-control measures. This presentation will provide an overview of the design and construction associated with this challenging project.

Concurrent Session 2B:

Performance Study of Minnesota’s 1st GRS-IBS Structure in Rock County, MN

Derrick Dasenbrock, P.E.
Geomechanics/LRFD Engineer
MnDOT, Maplewood, MN

Geosynthetic Reinforced Soil Integrated Bridge Systems (GRS-IBS) for use in major highway transportation applications are a relatively new concept. Closely spaced layers of geosynthetic reinforcement, compacted fill, and fascia elements are used to build economical bridge structures with readily available materials, small equipment, and labor. A GRS-IBS structure was constructed over the Minnesota Southern Railroad in Rock County, approximately 3.8 miles west of Luverne, Minnesota. A unique feature of this bridge in relation to previous GRS-IBS structures is that the bridge has a 5% grade and the reaction of the GRS wall to additional stress imposed by a bridge constructed at this grade was of research interest. It was hoped that insight could be gained with respect to the magnitude of the movement during thermal cycles, the reaction of the GRS walls to that movement, and additional stress due to downslope bridge movement- if any occurred. The bridge was constructed in the spring of 2013. A variety of geotechnical sensors were installed to monitor the performance of the bridge abutments over a 3 year period through Minnesota weather extremes. An overview of the monitoring program and the performance data collected during the complete study period is presented.

3:40 pm

Concurrent Session 3A:

Development and Application of an Automated Model Calibration Procedure for Two Case Histories: Tailings Basin and Landslide Repair

Raul A. Velasquez, Ph.D.
Geotechnical Engineer
Barr Engineering, Minneapolis, MN

It is common practice in geotechnical engineering to use field measurements to calibrate computer models to simulate ground behavior. Typically, a manual "trial and error" approach is used by practitioners to estimate and back-calculate soil properties. A flexible and robust automated model calibration procedure has been developed and implemented to improve the current manual approach. The developed calibration tool uses a modified Newton-Raphson iteration method to efficiently move toward identification of model parameters (e.g., shear strength, deformability, and groundwater flow parameters) that minimize a user-specified error function to a desired tolerance. The automated calibration procedure was successfully applied to two case histories. First, the procedure was used to calibrate groundwater flow parameters (permeability and associated anisotropy) of a tailings basin with complex stratigraphy and with an extensive database of field measurements. The second project involved a state highway landslide repair where limited piezometer field measurements were available but again the method was used to calibrate groundwater flow parameters (permeability, anisotropy, and boundary conditions). This paper presents a brief summary of each case history and the details of the automated seepage model calibration results.

Concurrent Session 3B:

Dynamic Cone Penetrometer and Relative Density Relationships for Uniformly-Graded Sands

Mark A. Muszynski, P.E., Ph.D.
Assistant Professor, Civil Engineering
Gonzaga University, Spokane, WA

The dynamic cone penetrometer (DCP) is a portable instrument capable of providing an indication of the state-of-compactness of soils for use in foundation and pavement engineering applications, among others. This instrument is, at a basic level, able to assist the engineer in evaluating whether the ground conditions encountered on a site during foundation excavation activities are consistent with the original soils exploration. More information about the ground conditions may be gleaned with the instrument, however. The ability to evaluate soils at depth, and in a relatively non-destructive and cost-effective manner, is an advantage that the DCP enjoys over the nuclear density gauge test and, at times, the standard penetration test (SPT), if suited to the project at hand. However, engineers often begin using the DCP with minimal information regarding correlations of its results with relative density or relative compaction. These relationships are often gained over the course of time. This paper is intended to share current information about the use of the Sowers DCP, primarily on soils consisting of clean, uniformly-graded, quartz sand; either natural/undisturbed or when used as engineered fill. Additionally, several specific case studies are highlighted including further description of some of the sites where Sowers DCP measurements were compared to SPT and/or nuclear density tests.

4:05 pm

Concurrent Session 4A:

Numerical Simulation for the Feasibility Study of a Parking Ramp over the LRT Station Minneapolis-St. Paul International Airport

Lee Petersen, P.E., Ph.D.
Principal Engineer
Itasca Consulting Group, Minneapolis, MN

Minneapolis-St. Paul International Airport (MSP) serves about 36 million passengers annually. On-airport parking provides about 22,900 parking spaces and is frequently at or near capacity. As a result, design is underway for a parking ramp expansion at Terminal 1-Lindbergh. The facility is served by the Metro Transit light-rail (LRT) Blue Line. The existing LRT station is underground and adjacent to the existing parking ramp. The proposed parking ramp expansion will be constructed over the north end of the station. The LRT station is constructed in an excavation of the St. Peter sandstone and Glenwood shale, with a flat roof of the Platteville limestone. Construction of the parking ramp expansion involves two principal impacts on the LRT station: a) column loads on the Platteville limestone above or nearby the station; and b) excavation of the soil cover and some of the Platteville limestone above the station. As part of the feasibility study, the magnitude of these impacts was assessed by conducting a 3D geostructural analysis of the station using Itasca’s distinct element modeling software called 3DEC. Six different options were chosen for detailed geostructural feasibility analysis and compared. The differences between these options affected the response of the station roof and walls, and were the basis for assessing the feasibility of the proposed construction.

Concurrent Session 4B:

Highway 53 – DTH Pile Installation Case Study: Variable Diameter, Difficult Drilling

Nathan W. Iverson, P.E.
Chief Geotechnical Engineer
Veit & Company, Rogers, MN

The Highway 53 Bridge foundations were constructed by utilizing Down the Hole Hammer (DTH) installed pipe pile. A DTH is an excellent tool to drill in difficult rock formations and can be used in conjunction with an overburden drilling system to drill through some of the most difficult site conditions, but had been untested in the abandoned Rouchleau Mine Pit in Northern Minnesota. During the design phase, three different diameters of DTH pile were evaluated. DTH pile with diameters of 18, 24, and 30 in. were successfully installed onsite, but each posed their unique challenges. These piles were installed to a depth in excess of 176 ft below existing grade through 131 ft of mine debris and penetrating 45 ft into the underlying bedrock. The geology at the site is very unique due to the variable nature of the fill, high groundwater table in an environmentally sensitive water body, and the extremely high compressive strength and hardness of both the bedrock and the fill. This case study will contrast the challenges encountered with each of the different diameter piles installed and discuss the results.

4:30 pm Adjournment
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