Geotechnical Track (Morning)
Geotechnical Reports: Proper use in Design and Construction Contracting
Douglas Clark, P.E., Civil & Environmental Consultants, Inc., Pittsburgh, PA
Subsurface conditions represent some of the largest uncertainties and risks in civil construction. Fortunately, most owners recognize the need to perform a geotechnical investigation as part of the design development to obtain information pertinent to project design and construction. What is often less understood is how the geotechnical report and information should be used in design, and how it applies to the construction contract. Many assume, often incorrectly, that the geotechnical report serves as a “baseline” for establishing the site conditions. While this may be true in some cases, most standard contract general conditions (AIA, EJCDC, etc.) place the risks associated with subsurface conditions on the bidder, and provide the geotechnical report only as information, not as a contract document. This presentation discusses the issue of reliance on the geotechnical report by the parties involved, presents case-studies, and provides recommendations for owners and contractors to reduce risks.
Civil Engineers, What Rammed Aggregate Pier (RAP) Ground Improvement means to You
Keithe J. Merl, P.E., GeoStructures, Pucellville, PA
Have you worked on sites that had undocumented fills, soft soils, or adjacent structures? Difficult site conditions, variable subsurface conditions, and tight construction budgets can bring your project to a complete stand-still.
This session will focus on how civil, geotechnical, and structural information is synthesized during the schematic phase of your project to provide a comprehensive ground improvement design. By recognizing and seizing opportunities to integrate ground improvement during pre-construction, you can successfully aid your clients in the management of risk and cost on their projects.
Local case studies including support of the PPG Paints Arena and projects in the Strip District will be used to illustrate:
- ground improvement design;
- the benefits of performance based specifications;
- how sequencing of RAP installation and bulk filling operation affect the overall performance of the structure and construction costs; and
- best practices for reviewing ground improvement designs during construction.
Advanced Design Methodology for Shallow Landslide Repair Using Launched Soil Nails
Corey D. Mislinski, P.E., GSI, Pittsburgh, PA
Ballistic soil nails have been used in the United States to repair shallow roadway landslides for nearly 20 years. The U.S. Forest Service/Federal Highway Administration “Application Guide for Launched Soil Nails” is the principal design manual for designing with ballistic soil nails and employs a simplified sliding wedge analysis using limit equilibrium concepts to determine the factor of safety of a slope reinforced with soil nails. The design methodology quantifies the tensile and shear resistance provided by the individual nails, but is simplistic and is limited to linear failure surfaces in homogenous materials.
The presentation will explain some of the recent advancements in launched soil nail design methodology using PC-based limit equilibrium programs, including the use of shear calculations in RocScience’s Slide 7.0 and GeoStudio’s Slope/W program, as well as a brief introduction to the program LSNAP (Launched Soil Nail Analysis Program). An improved method of estimating bond strength is presented. The shear contribution of ballistic soil nails, often ignored in conventional soil nail design, is shown to be an important contribution to the stability of ballistic soil nail landslide repairs.
Controlled Modulus Column (CMC) Rigid Inclusion Support for Embankments and MSE Walls– Design and Full-Scale Test Results
Nina Carney and Sarah Ramp, Menard, Pittsburgh, PA
Controlled Modulus Column (CMC) Rigid Inclusions are grouted, auger-displacement elements that are installed using a specially designed tool at the working end of a high torque, high down-pressure drilling machine. The tool is hollow so that flowable cementitious grout can be placed from the bottom up once the tooling has advanced to the desired depth. The patented CMC system fits in the generic category of rigid inclusions. There are a number of other types of inclusions that are currently designed and constructed using stone, grout, and concrete. The design technology behind the development of the CMC rigid inclusions makes them uniquely efficient for the immediate support of MSE walls and embankments on soft, compressible soils for public transportation, other infrastructure facilities, large storage tanks, and building facilities.
CMC rigid inclusions are an ideal solution for the immediate support of fill walls and embankments for bearing capacity and settlement control, as compared to other solutions with long consolidation periods such as wick drains with surcharge. The CMC rigid inclusion system relies on a granular Load Transfer Platform (LTP) which efficiently distributes the load from the structure or embankment to the rigid inclusions, while limiting the amount of load transferred to the surrounding soils. CMC rigid inclusions are designed using special proprietary finite element techniques that include the effects of load sharing between the LTP, the columns, and the surrounding improved ground.
This presentation will include a technical overview of the design theory of CMC rigid inclusions for embankment support, case studies of projects completed in the region, and finally, the results of full-scale instrumented testing of CMC rigid inclusion projects. We will compare actual performance monitoring data to the key predictions of the finite element models.