Survey of Micropile Use in Neighboring Western States
Started: April, 2015 Ended: October, 2015 Project ID #4W5365 Status: Completed
Results & Findings
The final report describes the survey findings, which included the following. Response to this survey indicated use of micropiles in situations for which they were intended. The use of micropiles was tied to the availability of qualified contractors. With the Pacific Northwest containing such contractors, use in this area has become common practice and satisfaction is high. In states where population density is lower and local micropile contractors are not available, micropiles have been used less frequently. Responses emphasized the importance of a well-qualified contractor and a well-qualified QA/QC program. Responses also indicated the importance of comprehensive geotechnical data describing the subsurface conditions in which micropiles will be installed. For the agencies responding, the greatest use of micropiles was for new bridge foundations, followed by projects involving retrofitting existing bridge foundations. Micropiles appear to be versatile as evidenced by their use on a variety of projects involving structures other than bridge foundations. Responses indicated that micropiles have been used exclusively on projects for which other conventional deep foundation approaches would not work. The reasons for this were approximately split between site surface conditions and subsurface conditions. These responses supported the notion that micropiles are particularly suited for difficult ground conditions (i.e. presence of cobbles and boulders, intermediate geomaterials) and sites with restricted work areas having limited space and/or remote access and/or urban, noise and vibration sensitive sites. Load testing of micropiles is common and appears to be incorporated in all projects. None of the agencies responding indicated a “failure” or lack of capacity with project micropiles that have been load tested, which speaks to the success and high degree of satisfaction of the users. Contracting methods for micropile subcontactors appear to be typical and well established. All agencies have developed specifications and/or special provisions for this technology. Limitations associated with micropiles involve limited lateral capacity in areas of high seismic demand and the higher cost of installation as compared to conventional deep foundations. The latter limitation is not necessarily applicable in common situations where a conventional deep foundation cannot be used.
The objective of the proposed project is to gain knowledge of the state-of-practice in western state departments of transportation regarding the use of micropiles for foundation support and earthen slope repair.
Micropiles are small diameter piles that are constructed by drilling and grouting techniques. Micropiles are a foundation alternative that are cost-effective in a variety of conditions encountered in Montana Department of Transportation (MDT) projects. While the technology was first introduced in the US in 1973, MDT’s experience with micropiles is limited. A limited experience base has led to underutilization of a potentially beneficial foundation alternative. MDT is interested in exploring a greater use of micropiles and would like to begin by gathering information from neighboring western states on their use of micropiles in transportation-related projects. The objective of the proposed project is to gain knowledge of the state-of-practice in neighboring western state departments of transportation regarding the use of micropiles for foundation support and earthen slope repair. This objective will be met by developing, conducting and compiling the results of a survey given to neighboring western state departments of transportation on the use of engineered micropiles. The results of this research will be used to develop plans and methods for the use of micropiles in bridge retrofitting projects, but will also be applicable to other applications.
Steve Perkins - PI
Susan Sillick - Main External Contact
Files & Documents
Sponsors & Partners
- Montana Department of Transportation (MDT) Sponsor