Here Are Some of the Questions We Ask Martin:
- What are wick drains and how do they work?
- How are wick drains designed and who is typically responsible for the design?
- How long have they been used in the US?
- What types of soils are they installed in and what types of structures are they installed for?
- When shouldn’t wick drains be installed?
- What ground improvement techniques would you go to for soft clays if wick drains aren’t appropriate?
- What are the biggest challenges with installing wick drains?
- Are there any specific safety concerns when working with wick drains?
- What advice would you like to give to engineers that are specifying wick drains?
Here Are Some of the Key Points Discussed About Wick Drains for Ground Improvement in Geotechnical Engineering:
- When you place fill on some types of soils, they experience issues because there is pore pressure building up in the soil. These soils are slow-draining fine-grain soils such as clay. It is known as consolidation settlement which can take years or even decades to occur. Wick drains are installed to shorten the drainage pattern pathway, speed up the consolidation process, and increase the strength of the soil. Wick drains are thin prefabricated drains that consist of a plastic core with channels in them and are encased by a geotextile fabric that acts as a filter that prevents fine soil from migrating into the drain.
- Wick drain designs can be made in many ways depending on the schedule and economics of the project. It is an iterative process while looking at the different factors. Wick drains are used to speed up the settlement while other ground improvement techniques are used to mitigate settlement. They are best designed by the project’s engineer as opposed to the installer because of the many variables that must be considered.
- Wick drain has been used since the late 1970s with the development of geosynthetics and replaced sand drains by the mid-1980s.
- Wick drains bring the water up to the surface of the soil, or below the consolidating layer. When the water comes up to the surface, you need a way of receiving the water like a drainage blanket made from sand or rock.
- Pre-drilling is a common issue when installing wick drains. The drilling is more expensive than only installing the wick drains. It is required when you have a dense or stiff layer at the surface.
- Wick drains are installed in fine grain slow draining soil like clays, silts, silty clays, sludges, and fine grain dredged materials. They are used in transportation projects, storage tank projects, large port projects, and general buildings and structures.
- Wick drains are used for up to 3-story buildings but cannot be used in mid or high-rise buildings.
- Wick drains are typically used in soft clays. If wick drains are not appropriate, Controlled Modulus Column (CMC) rigid inclusions can be used because stone columns or aggregate piers have issues with the lack of confinement in the soft clays.
- When working with wick drains, you must look at how stiff the soils are and if the mandrel will be able to penetrate them. If the soils are too stiff, then other ways of assisting the mandrel must be considered. When installing the wick drain with the mandrel, there is a rebar anchor that must be secured before extracting the mandrel. If the soils are too soft, then the wick drain will not be securely anchored and will be pulled up with the mandrel. Rupturing artesian pressure layers can cause a high velocity of up flow which can cause the wick drain to not anchor securely.
- When using very long masts to insert the wick drains, be cautious of overhead utilities and powerlines. Working platforms can become an issue when working with heavy machinery on them. Whenever you are penetrating the ground, buried utilities can be a concern.
- Get involved with organizations like DFI and get all the information that they have available for working platforms and educate yourself on working with them. Working platforms are an ongoing problem that the industry is working on improving.
- Do your due diligence in what you are specifying is a practical, buildable, and cost-effective approach. Involve specialty contractors to walk through projects with you and maybe suggest alternate solutions that can help the projects.
More Details in This Episode…
About the Guest: Martin Taube, P.E., P.G.
Martin G. Taube, P.E., P.G. is Vice President of Business Development for Menard USA. In this position, he is responsible for business development and managing corporate educational, communications, and marketing processes. Before joining Menard, Marty was with Nicholson Construction Company, most recently as business development manager. He has held positions at Michael Baker Corporation, Orbital Engineering, Inc., and the US Army Corps of Engineers. Marty is registered as a professional engineer and professional geologist in the Commonwealth of Pennsylvania. He received a BS in geophysics from Virginia Tech and an MS in geotechnical engineering from the University of Pittsburgh. Marty has written numerous papers about a variety of ground improvement techniques and specialty geotechnical construction practices. He is a member of the American Society of Civil Engineers, Louisiana Engineering Society, Engineers without Borders, and GBA, and is currently serving on the Board of Trustees of the Deep Foundation Institute’s Ground Improvement Committee.
About the Host: Jared M. Green, PE, D.GE, F.ASCE
Jared, originally from southwest Philadelphia, Pennsylvania, graduated from Syracuse University’s College of Engineering in 2001 with a B.S. in Civil Engineering. He later went on to attain his M.S. in Civil Engineering (Geotechnical Focus) from the University of Illinois, Urbana-Campaign, in 2002. In 2003, he began working in the New York City office of Langan. He has since become a Principal / Vice President and is one of the owners of this international land development engineering consulting firm. After 15 years at Langan, Jared has moved to the Philadelphia office and is one of the geotechnical practice leaders in that office.
Jared is a consultant and team leader who also enjoys mentoring young engineers and first-generation college students. He has been instrumental in increasing the number of pre-college students who are interested in STEAM majors and fields. He strives to make complex engineering topics relatable and understandable to people new to the field and to people who are completely unfamiliar with engineering. Jared and his family currently reside in Flemington, New Jersey. He and his wife have three energetic, inquisitive, and awesome children. You can connect with Jared here.
This Episode Is Brought to You by
Menard USA is a specialty ground improvement contractor that works nationally providing design-build ground improvement solutions at sites with problematic soils. Menard works closely with civil, structural, and geotechnical engineers to minimize foundation costs for a wide range of soil conditions, structure types, and loading conditions. To learn more about Menard USA, or for help on your next project, please visit www.menardusa.com.
PPI has helped engineers achieve their licensing goals since 1975. Passing the FE and PE exams can open doors to career advancement and new opportunities. Check out PPI’s wide range of prep options, including live online courses, on-demand courses, and digital study tools to help prepare you to pass your licensing exam. Check out PPI today at ppi2pass.com to see all the options available for FE and PE exam prep.
Please leave your comments or questions in the section below on wick drains for ground improvement in geotechnical engineering.
To your success,
Jared M. Green, PE, D.GE, F.ASCE
Host of The Geotechnical Engineering Podcast