Geotechnical Engineering

Best Practices for Using Shotcrete for Wall Fascia, Phase 2

Fascia walls are structural earth retaining components for soldier pile and soil nail walls, and they are traditionally constructed with cast-in-place (CIP) concrete.  In recent years, some state departments of transportation have begun to replace the CIP concrete with shotcrete for wall fascias. The primary difference between shotcrete and CIP concrete is that shotcrete is placed and consolidated pneumatically (using high-pressure air). This method of construction is attractive because of its potential for saving cost and construction time. However, it also has potential drawbacks that raise concerns about its durability. Currently very limited information is available to evaluate curing practices, construction, and long-term durability for shotcrete. Phase I of this research (see WA-RD 870.1) showed that the performance of shotcrete is viable and promising in comparison to CIP concrete and that, if fully investigated, shotcrete may replace CIP concrete and be suitable for other applications. This Phase 2 project will follow up on issues identified in Phase I, such as the influence of mix design criteria on early age and long-term performance and the effects of air content on long-term performance. With the increasing desire for highway agencies to use shotcrete for accelerated construction and rapid renewal, the results will be a useful resource to help WSDOT achieve the best structure quality and durability.

Principal Investigator: Pizhon Qiao, Civil and Environmental Engineering, WSU
Sponsor: WSDOT
WSDOT Technical Monitor: Brian Aldrich
WSDOT Project Manager: Jon Peterson
Scheduled completion: June 2019

Update to WSliq Software for Soil Liquifaction Hazard Evaluation

This project is updating and extending the capabilities of a computer program, WSliq, for evaluating soil liquefaction hazards.  Probabilistic liquefaction hazard analysis (PLHA), developed previously for WSDOT and implemented in WSliq, has been recognized as an improved procedure for evaluating potential hazards from liquefaction.  PLHA considers all peak ground surface acceleration and magnitude levels based on site-specific ground motion hazard data and weights the contributions of all according to their joint probability of occurrence.  In doing so, it considers all possible earthquake scenarios and allows designs based on consistent likelihoods of triggering at all locations within the state. Because a number of changes have occurred in the geotechnical profession’s understanding and treatment of liquefaction since the development of WSliq, this project is developing, implementing, and testing new PLHA procedures and updating the WSliq program to incorporate the resulting improvements.

Principal Investigator: Steven Kramer, Civil and Environmental Engineering, UW
Sponsor: WSDOT
WSDOT Technical Monitor: Tony Allen
WSDOT Project Manager: Jon Peterson
Scheduled completion: September 2019