Vol. 14 Issue 1 PRACTICAL AND ENTERTAINING SINCE 1997 SPRING 2011

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THE POCKET

Consultant

chubbard@braunintertec.com

Charles HubbardPE, PG

Field and Laboratory Capabilities Expanded By Charles D. Hubbard, PE, PG

With the purchase of a flat-plate dilatometer, Braun Intertec has expanded its in-situ field testing capabilities. The dilatometer is an efficient tool for evaluating settlement and lateral deformation for projects such as turbine and transmission tower foundations.

We’ve also increased the number of

triaxial cells in our geotechnical laboratory to 18, reducing the time required to perform unconsolidated-undrained (UU) and consolidated-undrained (CU) triaxial shear tests with or without pore water pressure measurements. The CU triaxial shear test in particular provides a rigorous means of evaluating shear strength for a variety of geotechnical loading problems where the influence of pore water pressure needs to be considered. Our triaxial cells have been used extensively to assist the US Army Corps of

Engineers with their preliminary Fargo/Moorhead Diversion Study.

Our geotechnical and materials testing laboratory is used to processing large sample volumes. In addition to five standard consolidation cells, we have 17 pressure boards that can perform consolidation tests or triaxial shear tests. We also have two MTS computer-controlled, servo-hydraulic testing machines for special applications including, constant rate of strain consolidation testing and resilient modulus of soils testing.

Back pressure is applied to saturate a triaxial shear sample prior to loading.

Braun Intertec wins ACEC/MN Grand Award Braun Intertec was recently awarded a Grand Award from the American Council of Engineering Companies of Minnesota for work performed on the Central Corridor Light Rail Transit (CCLRT) project.

For this project, Braun Intertec was retained by the Metropolitan Council to perform a Phase II Environmental Site Assessment (ESA) for the length of the corridor at a point in the project when the design team had already finalized 60 percent of the overall design. Representatives from the Metropolitan Council had two primary objectives when

they retained Braun Intertec: incorporate into the design enough environmental data to (1) avoid encountering contamination during construction and (2) minimize environmental liability when developing the 11-mile rail line. Because of the rapid progression of the project, Braun Intertec needed to complete the Phase II ESA and associated soil sampling at hundreds of locations along the line by the end of 2009, while generating vital data and thousands of individual documents along the way.

Braun Intertec developed a custom web portal, data organization and report sharing application called Braun Interport Custom™ and implemented a streamlined process designed to provide field data results generally within 24 hours. Crews were on site with rugged computers while performing the field work and uploaded

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Braun Intertec launches new website We invite you to learn more about our firm by exploring our company’s new website at www.braunintertec.com. Key site features include multiple view/search options to review our markets and services, showcase projects, office locations and latest industry news. Clients can also conveniently access the Braun Interport™ client portal through the new site.

Look for a specific service you are interested in or check out our capabilities by reviewing the market sectors we serve.

Project overviews help familiarize you with our services and show you how we’ve applied our expertise to similar projects, as well as staffed projects that have multiple service needs.

Click here to access office locations, driving directions and contact information.

View the latest news about our people, projects and events. You can also read our newsletters and learn more about what Braun Intertec is up to these days.

Access your Braun Interport™ account through the web, too. Talk to your project manager about Braun Interport™ and the advantages it offers for viewing, downloading and sharing your project information.

Social media fan? Stay abreast of Braun Intertec news by following us on Twitter, LinkedIn and our RSS feed.

Want to know more about working at Braun Intertec? Check out our career opportunities and learn more about why we are the Employer of Choice.

ACEC/MN - Continued from page 1 AAMA testing now available

performance and forced entry resistance. Many construction materials specifications now require testing services by an AAMA- accredited laboratory. For more information, contact Kurt Berglund at 952.995.2278.

Braun Intertec is now accredited by the American Architectural Manufacturers Association (AAMA) to perform field and laboratory window and door testing. Our main window testing services include air infiltration, water penetration, structural

information to the Braun Interport Custom™ web portal for the project manager and ultimately for the client to review. This significantly cut the traditional reporting time in half, allowing the design team to incorporate the information into the final design. Because the client and project manager had access to Braun Interport Custom™, they could review the information and respond to concerns when sampling crews were in the area, saving time and ultimately completing the work several months ahead of schedule and well within budget. The Braun Interport Custom™ system and associated reports continue to be used on the CCLRT project.

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By Matt Glisson, PE Editor’s note: The following article is the second half of a two-part series. Visit www.braunintertec.com to view the Fall 2010 issue under News & Events.

In our previous article we discussed the different types of deep foundations and some of what goes into their design. Once a deep foundation system is selected and

Deep Foundations Part II: Proving Their Strength

mglisson@braunintertec.com

Matt Glisson, PE

load requirements are determined, the process of constructing then begins. Successful deep foundation projects include quality programs to validate the design assumptions and to determine if the contractor was able to install the deep foundation as planned. For most projects, the quality program is structured around two distinct operating procedures: observations and tests.

Observations Observations have been a part of quality programs for the construction of deep foundations for as long as deep foundations have been around. In many cases, they provide some of the most useful information to the design team in evaluating the ability of individual deep foundation elements to meet the design requirements. Unfortunately, observations often do not explain why something occurred but only give the result, such as a high grout-take for a portion of an auger-cast pile, or a driven pile having a sudden decrease in penetration resistance. Hopefully, the geotechnical engineer has enough other information from the design or even the construction phase of the project from which to interpret the results of the observations in a meaningful manner.

Specific observations during construction of a deep foundation system vary depending on the system. In general, observations include the installed depth/elevation relative to design depth/elevation, resistance to driving or drilling, and the measure of how plumb the pile top is. For drilled foundations, the amount of concrete or grout placed relative to the amount of drilled material is also observed in addition to testing the grout or concrete for consistency and strength. The bottom of a drilled shaft may be observed to document that the toe will bear in sound material. Similarly, a driven pipe pile will usually be observed for indications of damage, sweeping and/or water. With recent advances in technology, most observations are supplemented by electronic recording equipment that can count the number of blows for a driven foundation, record the depth, grout volume and pressure for auger-cast piles and many other pieces of data. However, computers cannot yet record every detail of construction. Thus,

there is a need for a human observer during the installation of deep foundations.

Load Tests Due to the associated costs, load tests are most often performed only on test piles, but they may occasionally also be performed on production piles. Some load tests are destructive. A destructive load test is a test that can damage the deep foundation or significantly alter the soils or rock supporting the deep foundation. In either case, the test pile may not be able to perform as designed after the test, and such test piles are sacrificed and not incorporated into the foundation system supporting the structure.

Other tests are non-destructive. A non-destructive load test is a test that allows evaluation of the resistance and structural strength of the deep foundation while also allowing the deep foundation to meet the project requirements for performance after the test. A deep foundation subjected to a non-destructive test can still be used to support the structure.

There are different types of load tests and even different purposes for performing them. Static load tests can be performed by applying the load to the top or bottom of the deep foundation. The load type(s) and magnitude(s) applied to the test pile determine if a static load test is destructive or non-destructive. Most static load tests are done with the intent of determining the ultimate resistance of the deep foundation, so this type of test is typically considered as a destructive test. Dynamic load tests are only performed by applying the load at or near the top of the deep foundation. Similar to static load tests, dynamic load tests may or may not be destructive depending on the load type(s) and magnitude(s), but the determination also depends on the type of deep foundation. However, most dynamic tests are non-destructive since only a portion of the design load is applied to the deep foundation as a force.

Osterberg Cells, also called “O-Cells,” were connected to the reinforcing cage during the load test for the new I-35W bridge. These cells helped measure deflections so the ultimate load-carrying capacity of the deep foundation could be evaluated.

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Survival Tips for Avoiding Trouble in the Wild Apply to Risk Management in Professional Practice

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Sometimes, “engineered things” fail. Most of the time (thank goodness) the failures are small and insignificant: foundation settlement, a pothole, a leaky roof. Sometimes, however, the failures are large and life-threatening: a crane collapse, a dam failure.

Ask the ProfessorBy Charles Hubbard, PE, PG

chubbard@braunintertec.com

Charles Hubbard,PE, PG

Sand pile theory tells us that failures are a normal characteristic of natural systems. Sand falling upon itself, as in an hourglass, reaches a critical state form whose height and geometry are subsequently maintained through random failures of various sizes. Small failures occur frequently, large failures less so. Preventing either type of failure is difficult without containing and modifying the entire system because we cannot predict where, when and under what circumstances the next failure will occur, or how extensive it will be.

Taking over an unstable system — a compressible foundation, a contaminant plume, a slope failure — is expensive. Only under the most severe circumstances can the expense be justified. For most other situations we are left to balance cost with risk.

Dams are good examples of tightly coupled, complex systems. Granular filters, blankets and chimneys are designed to intercept and control long-term, steady-state seepage and prevent internal and external erosion. However, under large system heads these features can be challenged or compromised by pressurized foundation soils, unintended penetrations through the dam and/or foundation soils, improperly graded or insufficiently permeable filter soils, poor fill placement procedures or poor compaction. Failure of any one element can cause dam failure.

System control is also difficult with engineered “things” because the systems are tightly coupled and complex. The parts and forces that interact can be difficult to conceptualize, identify and evaluate. Part/force interaction can produce unintended, unanticipated results that, singularly or together, lead to failure. And the effects of such interactions spread easily throughout the systems.

Survival experts, search and rescue professionals and other public safety personnel study system stability because knowing what gets us into trouble is the best way to avoid it. In the wild, learning by experience, if it does not initially cause death, risks not only the victims’ lives but also the lives of those with them and those trying to rescue them. But these people do more than just study systems. They study people, too. They understand that consistency and clarity in thought and decision-making processes is often more valuable than any other knowledge in survival situations.

As designers and builders of life-supporting projects we can learn from these ideas. We spend a lot of time gaining experience by evaluating system stability. We are taught engineering principles and theory in school. We determine factors of safety for design projects. We validate our findings through observations and measurements during and after construction. With our parameters, formulas and procedures effectively packaged up with convenient charts and

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RISK MANAGEMENT - Continued from page 4

graphs, however, and trusting in the complexities of software most of us could not code, we risk becoming trapped inside the box and missing the one factor we haven’t considered before, the one factor that hasn’t been significant before, and finding that, despite having engineered 99 safe systems, the 100th fails.

The more comfortable we are from our experience, the more confidence we gain from success, the more vulnerable we are, the less likely we are to fully take in the problem at hand as well as the environment surrounding it. We must always assume there is something we haven’t seen, something we haven’t learned. Humility, therefore — recognizing that every project could conceal something new — is a sound platform from which to approach our work.

Humility hones our ability to perceive (versus anticipate) and understand before acting. Make a plan, but be flexible — be prepared to adjust to something unforeseen (buried bridge debris), but also know when improvising may complicate things (moving the proposed building into an adjacent swamp).

Devoting an appropriate amount of time to understanding the system you are working with is also necessary. It seems that in this electronic age information cannot be gathered, sorted and transmitted fast enough. Deadlines, however, will be the least of our worries if we misjudge a project’s requirements and a failure occurs. Recognize or research the system(s) you will be dealing with and how the corresponding parts, forces and governing parameters could impact system performance. If you don’t have a lot of

Boils of fine to coarse sand formed wherever groundwater was able to escape initial efforts to contain it.

Excavations that intercepted a historic borehole on the Roads Acting as Dams project in Devils Lake, N.D., that had not been grouted allowed groundwater that would otherwise have remained contained to flood the site, stopping work until it could be contained.

experience, find out what you can about similar systems, what design and construction challenges they pose and how they may have failed in the past.

Finally, don’t be afraid to pass on an opportunity if you aren’t confident that you can succeed.

Acting on these principles consistently will occasionally cause you to pause and may lose you a potential project or two (which may prove to be a good thing in the long run). But it will also give you the insight along with the experience to approach and successfully tackle projects that, from a more narrow perspective, might have otherwise seemed too daunting.

With piping under control, groundwater still flowed unabated through approximately 15 feet of excavation backfill. The area was finally stabilized with a series of grouted boreholes and a blended soil/bentonite cover fill.

For a static load test where the load is applied to the top, some form of reaction system (typically piles connected by beams) is required to actually apply the load. The main beam is centered over the test pile and a hydraulic jack and load cell are placed between the beam and the top of the pile. The pile top is instrumented to measure deflections so the ultimate load-carrying capacity of the deep foundation can be evaluated. Application of the load at the bottom of the pile most commonly uses an Osterberg Cell (O-cell) that is similar to a hydraulic jack and contains instrumentation for measuring O-cell expansion and strains. This approach does not require a reaction system as the skin friction of the deep foundation provides resistance to testing the end bearing of the deep foundation and vice versa. Like a top-load test, the top of the deep foundation is instrumented when applying the load to the bottom of the deep foundation to evaluate the foundation’s ultimate load-carrying capacity. For either case of applying the load to the top or bottom of the deep foundation, instrumentation at different locations can be installed along the deep foundation length to allow evaluation of the skin resistance provided by different soil or rock layers.

Dynamic load tests consist of an impact load usually applied by a drop weight or power-driven hammer, like a diesel hammer used to install driven piling. They can also use a mass and an explosion to create a force-pulse in what is often referred to as a quasi-static load test. Most often, dynamic tests are referred to by the test equipment – PDA (Pile Driving Analyzer) for a high-strain, fully-dynamic test, or Statnamic, for a high-strain, quasi-static load test. Both types of testing require numerical methods to determine the overall deep foundation resistance and the resistance provided by different pile segments and the pile toe.

From a geotechnical engineering perspective, performing a load test to failure using instrumentation is most useful. This approach allows us to obtain the most information from the load test and can result in reducing the overall deep foundation length either by lowering the safety factor (or increasing the resistance factor for LRFD methodology), or by using higher shaft resistance values or end bearing resistance values. Of course, there is always the possibility that a load test will indicate that certain soil or rock layers do not provide as much resistance as estimated during design of the deep foundation system. Usually with a conservative design this does not happen often, but it does occur. When resistance is under-estimated, having instrumentation along the deep foundation length allows for the use of the actual resistance values for a revised design. The downside of performing a load test is that it often requires a robust (i.e., expensive) reaction system for a load applied to the top of the foundation, and the

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LOAD TESTS - Continued from page 3

See LOAD TESTS - Continued on page 7

A Pile Integrity Tester is used for low-strain integrity testing.

sacrifice of equipment needed to apply a load to the bottom of the foundation (which can also be expensive). Also, there is the difficulty surrounding issues of defining failure and the different criteria methods that exist to do so. We might need a Part III to discuss that topic!

Integrity Testing Integrity tests are usually performed on production piles in conjunction with observations. Thus, integrity tests are non-destructive tests intended to assist in evaluating the in-place shape of the deep foundation. We perform integrity tests most often on drilled, deep foundations since the act of driving a pile into the ground is a form of integrity testing itself. The most common integrity tests used with deep foundations are cross-hole sonic logging and low-strain tests using either pulse echo or transient response methods.

Cross-hole sonic logging requires installing access tubes within the shafts. After the grout or concrete has reached sufficient strength, a transducer and receiver are placed inside the tubes. The time required for a sonic wave to travel from the transducer to the receiver is measured as the transducer and receiver are raised together from the bottom of the tubes. The process is repeated until all possible combinations of transducer and receiver pairings between the tubes are tested. The data is evaluated to determine if there are significant differences in arrival time of the sonic wave that indicate an abnormality within the deep foundation.

Low-strain integrity tests are done by attaching an accelerometer to the top of a deep foundation and hitting the top with a lightweight (1- to 8-pound) hammer with a special cap. The cap on the hammer

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By Alfred Gardiner, PE, LEED AP

If you don’t follow ASTM C150 and AASHTO M85 committee activities, you may not have noticed changes in the specifications for portland cement. These changes are the result of the efforts of members of the Harmonization Tack Group, representing both ASTM and AASHTO. The C150 M85 specifications

LOAD TESTS - Continued from page 6

Alfred Gardiner, PE, LEED AP

agardiner@braunintertec.com

The New Cement on the Block

are well-established, but they are also dynamic and change with new research in portland cement production and use. Advancements in technology drive both the production of portland cement and the ability to study and understand hydration (the chemical reaction that causes cement to harden). The latest change in specifications, which led to this new cement type in both documents, occurred in 2009.

Type II (MH) is the new cement type specified in both ASTM C150 and AASHTO M85. This cement meets the specifications for Type II cement but also has to meet a maximum Blaine fineness of 430m2/kg and a heat index as follows: C3S + 4.75C3A < 100. This cement specification provides the concrete industry with another option for concrete members that are sensitive to heat generation during early hydration. Specifying Type II (MH) cement is one of many options for dealing with heat of hydration-related issues.

For more information concerning cement specifications or other concrete concerns, please contact the Concrete Consulting Group at Braun Intertec at 612.685.5125.

The story behind portland cement Did you know that the “p” in “portland cement” should appear lowercase? It oftentimes is published with a capital “p” because of automatic word correction programs on computers. This cement, which was invented in 1824, is called “portland cement” because the mason who invented it thought it looked like the cliffs at England’s Isle of Portland.

Isle of Portland

Braun Intertec expands Concrete Consulting Group

Alfred Gardiner, PE, LEED AP, (see The New Cement on the Block) was recently hired to manage the company’s Concrete Consulting Group, which examines concrete and concrete-related materials, including aggregates, mortar and cement. The Concrete Consulting Group combines Braun Intertec’s established service areas of petrography, materials testing and building sciences to provide you with information and solutions that can help you improve your projects. Specialty service areas include: • Concrete forensics • Concrete construction troubleshooting

• Concrete material design • Field investigations

• Research involving portland cement

Alfred has 15 years of experience in the concrete industry and is a licensed professional engineer in Minnesota and Michigan. He is also a Leadership in Energy and Environmental Design Accredited Professional (LEED AP). His background includes testing material laboratory management, concrete investigation and client education. For more information about how the Concrete Consulting Group can help with your concrete management needs, call Alfred at 612.685.5125.

lengthens the impact pulse so that it is suitable for integrity testing. The accelerometer measures the pile response to the induced stress wave. A good test will show a clear toe reflection at the anticipated length. However, numerous factors can influence the quality of the test and the results. These factors include soil resistance, material properties (strength, density, etc.), reinforcing within the deep foundation, and the length of the deep foundation. As a general rule of thumb, integrity testing is practical for deep foundations with a length that is about 30 times its diameter (e.g., we can reliably test a 1-foot diameter deep foundation to a length of about 30 feet) although we have successfully performed tests on deep foundation lengths up to 60 times the diameter on multiple occasions.

Putting It Together Experience, the wonderful teacher that it is, has repeatedly taught us that a successful project starts with planning and design and ends with a good, quality program. The only “real way” we can know what a contractor builds below the ground is to exhume it, which defeats the purpose of putting it there to begin with. A comprehensive program that includes detailed observations, load tests and applicable integrity tests, can provide us with enough information to apply our engineering judgment on the overall ability of the deep foundation system to meet the project requirements.

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©2011 Braun Intertec Corporation

Questions, Requests and Comments

Charles Hubbard, PE, PG Braun Intertec Corporation 1826 Buerkle Road Saint Paul, MN 55110 Phone: 612.221.2501. chubbard@braunintertec.com

Lindsey Buhrmann, editor Braun Intertec Corporation Phone: 952.995.2078 lbuhrmann@braunintertec.com

This newsletter contains only general information. For specific applications, please consult your engineering or environmental consultants and legal counsel.

Fighting a flood? We do more than pile sandbags

Braun Intertec engineers and geologists have firsthand experience fighting floods throughout the Midwest. In addition to providing design services for new levees and floodwalls, and providing certification services for existing structures, we are available to consult on the geotechnical issues pertaining to temporary or emergency structures, including:

• Stability assessments of proposed temporary/emergency alignments.• Alternative construction materials, such as earth fill, Hesco barriers and sheet piling. • Construction inspections• Flood-stage seepage and stability inspections.

To learn more how about Braun Intertec can help with your flood projects, contact:

Charles Hubbard, PE, PG, at 612.221.2501.

Providing engineering and environmental solutions since 1957