Evaluating Helical Pier Installations for Stability

Evaluating Helical Pier Installations for Stability

* Advantages of Carbon Fiber over Traditional Repair Methods

* Understanding Soil Conditions and Their Impact on Pier Stability


Okay, so you're putting in helical piers, right? Carbon fiber reinforcement strengthens walls in need of foundation wall repair service residential foundation repair service waterproofing. Smart move for a stable foundation. But listen, you can't just screw them into the ground and hope for the best. The key thing you absolutely *have* to get right is understanding the soil. Seriously, it's everything.

Think of it like this: the soil is where your pier gets its grip. If it's loose, sandy stuff, your pier's going to struggle to hold anything up, like trying to grab onto smoke. Clay, on the other hand, can be strong, but it can also expand and contract with moisture, which can play havoc with your pier's stability over time. And let's not even talk about organic soils – they decompose and compact, which is a recipe for disaster.

So, what do you need to do? Get a soil report! Seriously, spend the money. It'll tell you the soil type, its density, its moisture content, and its bearing capacity. This information is gold. It tells you how deep you need to drive the pier, how much load it can handle, and whether you need to take any special precautions.

For example, if you're dealing with weak soil near the surface, you might need to drive the pier deeper to reach a more competent layer. Or, if you're in an area with high water tables, you might need to consider corrosion protection for the pier.

Ignoring the soil conditions is like building a house on sand. It might look good at first, but it's just a matter of time before things start to shift and crack. Understanding the soil is the foundation for a stable helical pier installation. Get it right, and you'll sleep soundly knowing your structure is secure. Get it wrong, and well, let's just say you'll be paying for it later.

* Key Factors Affecting Helical Pier Installation Integrity


Evaluating helical pier installations for stability hinges on understanding the key factors that affect their installation integrity. Think of it like baking a cake – you can have the best recipe (design), but if you don't follow the instructions carefully (installation), the result might be a soggy mess.

One critical aspect is **proper soil investigation**. You need to know what you're screwing into! The soil's composition, strength, and groundwater levels dictate the pier's depth, size, and helix configuration. Ignoring this step is like guessing the oven temperature – potential for disaster.

Then comes the **installation process itself**. The pier needs to be advanced at the correct torque, monitored closely, and installed to the specified depth. Too little torque and the pier might not achieve the required capacity; too much, and you risk damaging the helix or even buckling the pier. It's like trying to force a screw in too quickly – you strip the threads and weaken the connection.

**Equipment calibration and operator skill** are also paramount. Using a properly calibrated torque motor ensures accurate readings, while an experienced operator can interpret these readings and adjust the installation technique as needed. A skilled operator can sense subtle changes in soil resistance and make informed decisions to ensure a solid installation. It's the difference between a seasoned carpenter and someone just picking up a hammer for the first time.

Finally, **material quality and manufacturing tolerances** play a role. Using substandard piers or those with manufacturing defects can compromise the entire system. You wouldn't build a house with rotten lumber, would you? The same principle applies here.

In essence, ensuring helical pier installation integrity is a multi-faceted process. It requires thorough planning, careful execution, and constant monitoring. Neglecting any of these factors can lead to instability and ultimately, failure of the foundation. So, pay attention to the details, just like you would when baking that perfect cake!

* Critical Inspection Points During and After Installation


Okay, so you're putting in helical piers, right? Smart move, especially if you've got some iffy soil going on. But here's the deal: just sticking them in the ground isn't enough. You've gotta keep a sharp eye out, both while they're going in and after, to make sure they're actually doing their job and not just becoming expensive metal decorations. We're talking stability here, the whole point of the exercise.

During installation, the first thing I'm watching is the torque. Your engineer should have given you a target torque range, and you need to hit it. This is your primary indicator that the pier is biting into competent soil and achieving the required load-bearing capacity. If you're spinning the pier in like butter and the torque's way low, something's wrong. Stop. Figure it out. Maybe you hit a void, maybe the soil is weaker than expected. Don't just keep going and hope for the best. That's a recipe for disaster. Also, keep an eye on the pier itself; is it bending or buckling under the pressure? That's a huge red flag. And of course, proper alignment is crucial. You don't want the pier wandering off course during installation because that can compromise its ability to support the load properly.

Okay, so the piers are in, and you're feeling good. Don't relax just yet. Post-installation, you've got a few more things to check. First, immediately after installation, verify the final torque readings. Make sure they are within the acceptable range. Document everything meticulously. Then, you need to ensure proper connection to the structure. Is the bracket securely attached to both the pier and the foundation? Are all the bolts tightened to the correct specification? No shortcuts here. And finally, give it some time and monitor the structure for any signs of settlement. Hairline cracks in the drywall, doors that stick, floors that slope – these could be indicators that the piers aren't performing as expected. Regular inspections, especially in the first few months after installation, are essential.

Basically, think of it like this: helical piers are a precision instrument for stabilizing a structure. They're only as good as the care and attention you give them during and after installation. So, be vigilant, be thorough, and don't be afraid to ask questions if something doesn't look or feel right. Your structure's stability depends on it.

* Common Signs of Instability and Potential Causes


Okay, so you're out there evaluating a helical pier installation, looking for stability. What are the red flags, the little whispers that something might not be quite right? And what could be causing those whispers?

First, let's talk about the obvious stuff. Obvious, but sometimes overlooked. Is the structure that the piers are supporting showing any new cracks, especially in the foundation or walls? Are doors and windows sticking that didn't used to? These are classic signs of movement, and while not *always* pier-related, they warrant a closer look. Think of it like this: if your house is suddenly developing a limp, you need to figure out why.

Then there's the pier itself. A big one is visible movement or deflection of the pier shaft. Is it leaning in a way it definitely wasn't before? Is there any bending or buckling? This screams instability. Corrosion is another sneaky culprit. Rust is a natural process, sure, but excessive corrosion, especially near the connection points or in areas exposed to harsh soil conditions, can seriously weaken the pier.

What about the soil around the pier? Any signs of heaving or settling? Gaps forming between the pier and the surrounding soil? These could indicate that the soil is failing to provide adequate support, putting undue stress on the pier.

Okay, so those are some common signs. Now, what could be causing them?

A big one is improper installation. Did they use the right size and type of pier for the soil conditions and the load it's supposed to bear? Were they installed to the correct depth and torque? If the installation was shoddy, you're setting yourself up for problems down the road.

Then there's the soil itself. Soil conditions can change over time. Increased moisture content, erosion, even changes in the water table can all affect the soil's ability to support the pier. Maybe the soil wasn't properly tested before the piers were installed, and it turns out it's less stable than originally thought.

Overloading is another possibility. Has the structure's load increased since the piers were installed? Maybe an addition was built, or heavy machinery was added to the building. If the piers are being asked to support more weight than they were designed for, they're going to struggle.

Finally, don't forget about environmental factors. Things like earthquakes, frost heave, and even tree root growth can put stress on the piers and contribute to instability.

Basically, evaluating helical pier stability is about paying attention to the details. Look for the subtle signs of movement, consider the potential causes, and don't be afraid to call in a qualified professional for a thorough inspection if you have any concerns. It's better to be proactive than to wait for a small problem to become a big, expensive one.

* Methods for Assessing Pier Load Capacity and Performance


Okay, so you're looking at helical pier installations, making sure they're stable, and you're wondering how to actually *check* if the piers are doing their job, right? Well, there's a few ways to go about assessing their load capacity and how well they're performing. It's not just a "set it and forget it" kind of thing.

One common method is load testing. Basically, you apply increasing loads to the pier after installation and monitor its movement (or settlement). This gives you a direct measurement of how much weight the pier can handle before it starts to give way. There are different types of load tests, like proof tests (where you apply a specific load to verify it meets a minimum requirement) and performance tests (where you push the pier to its ultimate capacity to see where it breaks). This is pretty straightforward but can be time-consuming and expensive.

Another approach involves using torque correlation. During installation, the amount of torque required to screw the pier into the ground is recorded. There's a relationship between this torque and the pier's estimated load capacity, based on the pier's design and the soil conditions. This is a quick and relatively inexpensive method, but it's an indirect measurement, so it relies on accurate soil information and a good understanding of the correlation.

Then you've got methods that involve monitoring the pier's performance over time. This could include things like visual inspections looking for signs of settlement, corrosion, or other damage. You might also use surveying techniques to precisely measure any movement of the structure supported by the piers. This isn't a one-time assessment; it's more of an ongoing process to ensure long-term stability.

Ultimately, the best approach for evaluating helical pier installations depends on the specific project, the soil conditions, the loads involved, and the budget. Often, a combination of methods offers the most comprehensive assessment of pier capacity and performance. You want to be sure those piers are holding up their end of the bargain!

* Remedial Actions for Addressing Unstable Helical Piers


Okay, so we've got a helical pier installation that's showing signs of instability. Not good. We need to talk about fixing that. Think of it like this: the ground isn't cooperating, and our piers are wiggling when they really should be solid as a rock. What's the game plan?

First, *diagnosis is key*. We need to figure out *why* the pier is unstable. Is it poor soil? Was the pier under-torqued during installation? Is there a water table issue causing soil softening? A thorough geotechnical investigation is crucial. We're talking soil borings, maybe some cone penetration testing, the whole nine yards. Knowing the enemy (the soil conditions) is half the battle.

Once we understand the problem, we can start thinking about remedial actions. One option is *supplemental pier installation*. Basically, we're adding more piers adjacent to the unstable one to share the load. It's like giving your weak friend a buddy to lean on. These new piers need to be installed properly, reaching competent soil and adequately torqued.

Another approach might involve *grouting*. We can inject grout around the unstable pier to stabilize the surrounding soil. This essentially creates a reinforced soil matrix, providing greater resistance to movement. Think of it like injecting concrete into the gaps around the pier, stiffening everything up. Different types of grout exist, and the right one depends on the soil type and the nature of the instability.

Sometimes, the only solution is *replacement*. If the original pier was undersized or installed improperly, pulling it out and putting in a larger, properly installed pier might be necessary. This is the most disruptive option, but sometimes it's the only way to guarantee long-term stability.

Finally, *drainage improvements* can be critical, especially if water is contributing to the problem. Redirecting surface water away from the pier and installing subsurface drains can prevent soil saturation and maintain soil strength. A dry pier is a happy pier.

Ultimately, the right remedial action depends on the specific situation. There's no one-size-fits-all solution. It requires careful evaluation, expert judgment, and a healthy dose of engineering know-how. The goal is always the same: to ensure the long-term stability and safety of the structure relying on those helical piers.

* Importance of Professional Evaluation and Certification


Let's talk frankly about helical piers. You've got these metal shafts, screwed deep into the ground, holding up a structure. Sounds simple enough, right? But like anything that involves engineering, load bearing, and the long-term stability of something you probably care deeply about (like your home, or a commercial building), "simple" is a dangerous illusion. That's where professional evaluation and certification come in, and frankly, why they're absolutely vital when it comes to helical pier installations.

Think about it. Someone installs these piers. How do you *really* know they're doing it right? Are they using the correct type of pier for the soil conditions? Are they torquing them to the appropriate depth to achieve the necessary load-bearing capacity? Are they even *capable* of accurately assessing these factors in the first place? A visual inspection might catch the obviously bad stuff, but it won't tell you if the piers are subtly failing, shifting, or destined to become a problem down the line.

That's where a qualified professional evaluator steps in. They're not just eyeballing it; they're using specialized equipment, applying engineering principles, and adhering to established standards to analyze the installation. They're looking for things you wouldn't even think to look for, verifying that the piers are performing as designed and providing the intended support. Certification, then, is the stamp of approval. It's assurance that the installation has been rigorously assessed and meets the required criteria.

Skipping this step is like building a house on a shaky foundation – literally. You might save some money upfront, but you're setting yourself up for potential disaster. Foundation problems are notoriously expensive and disruptive to fix. Imagine cracks in your walls, uneven floors, doors that won't close properly. And that's just the cosmetic stuff. The structural integrity of your building could be compromised, putting everything – and everyone – at risk.

So, while helical piers can be a fantastic solution for foundation repair or new construction, don't cut corners. Insist on professional evaluation and certification. It's not just about peace of mind; it's about ensuring the long-term stability, safety, and value of your investment. It's an investment in doing things right, the first time, and knowing that your foundation is truly solid.



 

Boston's Big Dig presented geotechnical challenges in an urban environment.
Precast concrete retaining wall
A typical cross-section of a slope used in two-dimensional analyzes.

Geotechnical engineering, also known as geotechnics, is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics to solve its engineering problems. It also relies on knowledge of geology, hydrology, geophysics, and other related sciences.

Geotechnical engineering has applications in military engineering, mining engineering, petroleum engineering, coastal engineering, and offshore construction. The fields of geotechnical engineering and engineering geology have overlapping knowledge areas. However, while geotechnical engineering is a specialty of civil engineering, engineering geology is a specialty of geology.

History

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Humans have historically used soil as a material for flood control, irrigation purposes, burial sites, building foundations, and construction materials for buildings. Dykes, dams, and canals dating back to at least 2000 BCE—found in parts of ancient Egypt, ancient Mesopotamia, the Fertile Crescent, and the early settlements of Mohenjo Daro and Harappa in the Indus valley—provide evidence for early activities linked to irrigation and flood control. As cities expanded, structures were erected and supported by formalized foundations. The ancient Greeks notably constructed pad footings and strip-and-raft foundations. Until the 18th century, however, no theoretical basis for soil design had been developed, and the discipline was more of an art than a science, relying on experience.[1]

Several foundation-related engineering problems, such as the Leaning Tower of Pisa, prompted scientists to begin taking a more scientific-based approach to examining the subsurface. The earliest advances occurred in the development of earth pressure theories for the construction of retaining walls. Henri Gautier, a French royal engineer, recognized the "natural slope" of different soils in 1717, an idea later known as the soil's angle of repose. Around the same time, a rudimentary soil classification system was also developed based on a material's unit weight, which is no longer considered a good indication of soil type.[1][2]

The application of the principles of mechanics to soils was documented as early as 1773 when Charles Coulomb, a physicist and engineer, developed improved methods to determine the earth pressures against military ramparts. Coulomb observed that, at failure, a distinct slip plane would form behind a sliding retaining wall and suggested that the maximum shear stress on the slip plane, for design purposes, was the sum of the soil cohesion, , and friction , where is the normal stress on the slip plane and is the friction angle of the soil. By combining Coulomb's theory with Christian Otto Mohr's 2D stress state, the theory became known as Mohr-Coulomb theory. Although it is now recognized that precise determination of cohesion is impossible because is not a fundamental soil property, the Mohr-Coulomb theory is still used in practice today.[3]

In the 19th century, Henry Darcy developed what is now known as Darcy's Law, describing the flow of fluids in a porous media. Joseph Boussinesq, a mathematician and physicist, developed theories of stress distribution in elastic solids that proved useful for estimating stresses at depth in the ground. William Rankine, an engineer and physicist, developed an alternative to Coulomb's earth pressure theory. Albert Atterberg developed the clay consistency indices that are still used today for soil classification.[1][2] In 1885, Osborne Reynolds recognized that shearing causes volumetric dilation of dense materials and contraction of loose granular materials.

Modern geotechnical engineering is said to have begun in 1925 with the publication of Erdbaumechanik by Karl von Terzaghi, a mechanical engineer and geologist. Considered by many to be the father of modern soil mechanics and geotechnical engineering, Terzaghi developed the principle of effective stress, and demonstrated that the shear strength of soil is controlled by effective stress.[4] Terzaghi also developed the framework for theories of bearing capacity of foundations, and the theory for prediction of the rate of settlement of clay layers due to consolidation.[1][3][5] Afterwards, Maurice Biot fully developed the three-dimensional soil consolidation theory, extending the one-dimensional model previously developed by Terzaghi to more general hypotheses and introducing the set of basic equations of Poroelasticity.

In his 1948 book, Donald Taylor recognized that the interlocking and dilation of densely packed particles contributed to the peak strength of the soil. Roscoe, Schofield, and Wroth, with the publication of On the Yielding of Soils in 1958, established the interrelationships between the volume change behavior (dilation, contraction, and consolidation) and shearing behavior with the theory of plasticity using critical state soil mechanics. Critical state soil mechanics is the basis for many contemporary advanced constitutive models describing the behavior of soil.[6]

In 1960, Alec Skempton carried out an extensive review of the available formulations and experimental data in the literature about the effective stress validity in soil, concrete, and rock in order to reject some of these expressions, as well as clarify what expressions were appropriate according to several working hypotheses, such as stress-strain or strength behavior, saturated or non-saturated media, and rock, concrete or soil behavior.

Roles

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Geotechnical investigation

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Geotechnical engineers investigate and determine the properties of subsurface conditions and materials. They also design corresponding earthworks and retaining structures, tunnels, and structure foundations, and may supervise and evaluate sites, which may further involve site monitoring as well as the risk assessment and mitigation of natural hazards.[7][8]

Geotechnical engineers and engineering geologists perform geotechnical investigations to obtain information on the physical properties of soil and rock underlying and adjacent to a site to design earthworks and foundations for proposed structures and for the repair of distress to earthworks and structures caused by subsurface conditions. Geotechnical investigations involve surface and subsurface exploration of a site, often including subsurface sampling and laboratory testing of retrieved soil samples. Sometimes, geophysical methods are also used to obtain data, which include measurement of seismic waves (pressure, shear, and Rayleigh waves), surface-wave methods and downhole methods, and electromagnetic surveys (magnetometer, resistivity, and ground-penetrating radar). Electrical tomography can be used to survey soil and rock properties and existing underground infrastructure in construction projects.[9]

Surface exploration can include on-foot surveys, geologic mapping, geophysical methods, and photogrammetry. Geologic mapping and interpretation of geomorphology are typically completed in consultation with a geologist or engineering geologist. Subsurface exploration usually involves in-situ testing (for example, the standard penetration test and cone penetration test). The digging of test pits and trenching (particularly for locating faults and slide planes) may also be used to learn about soil conditions at depth. Large-diameter borings are rarely used due to safety concerns and expense. Still, they are sometimes used to allow a geologist or engineer to be lowered into the borehole for direct visual and manual examination of the soil and rock stratigraphy.

Various soil samplers exist to meet the needs of different engineering projects. The standard penetration test, which uses a thick-walled split spoon sampler, is the most common way to collect disturbed samples. Piston samplers, employing a thin-walled tube, are most commonly used to collect less disturbed samples. More advanced methods, such as the Sherbrooke block sampler, are superior but expensive. Coring frozen ground provides high-quality undisturbed samples from ground conditions, such as fill, sand, moraine, and rock fracture zones.[10]

Geotechnical centrifuge modeling is another method of testing physical-scale models of geotechnical problems. The use of a centrifuge enhances the similarity of the scale model tests involving soil because soil's strength and stiffness are susceptible to the confining pressure. The centrifugal acceleration allows a researcher to obtain large (prototype-scale) stresses in small physical models.

Foundation design

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The foundation of a structure's infrastructure transmits loads from the structure to the earth. Geotechnical engineers design foundations based on the load characteristics of the structure and the properties of the soils and bedrock at the site. Generally, geotechnical engineers first estimate the magnitude and location of loads to be supported before developing an investigation plan to explore the subsurface and determine the necessary soil parameters through field and lab testing. Following this, they may begin the design of an engineering foundation. The primary considerations for a geotechnical engineer in foundation design are bearing capacity, settlement, and ground movement beneath the foundations.[11]

Earthworks

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A compactor/roller operated by U.S. Navy Seabees

Geotechnical engineers are also involved in the planning and execution of earthworks, which include ground improvement,[11] slope stabilization, and slope stability analysis.

Ground improvement

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Various geotechnical engineering methods can be used for ground improvement, including reinforcement geosynthetics such as geocells and geogrids, which disperse loads over a larger area, increasing the soil's load-bearing capacity. Through these methods, geotechnical engineers can reduce direct and long-term costs.[12]

Slope stabilization

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Simple slope slip section.

Geotechnical engineers can analyze and improve slope stability using engineering methods. Slope stability is determined by the balance of shear stress and shear strength. A previously stable slope may be initially affected by various factors, making it unstable. Nonetheless, geotechnical engineers can design and implement engineered slopes to increase stability.

Slope stability analysis
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Stability analysis is needed to design engineered slopes and estimate the risk of slope failure in natural or designed slopes by determining the conditions under which the topmost mass of soil will slip relative to the base of soil and lead to slope failure.[13] If the interface between the mass and the base of a slope has a complex geometry, slope stability analysis is difficult and numerical solution methods are required. Typically, the interface's exact geometry is unknown, and a simplified interface geometry is assumed. Finite slopes require three-dimensional models to be analyzed, so most slopes are analyzed assuming that they are infinitely wide and can be represented by two-dimensional models.

Sub-disciplines

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Geosynthetics

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A collage of geosynthetic products.

Geosynthetics are a type of plastic polymer products used in geotechnical engineering that improve engineering performance while reducing costs. This includes geotextiles, geogrids, geomembranes, geocells, and geocomposites. The synthetic nature of the products make them suitable for use in the ground where high levels of durability are required. Their main functions include drainage, filtration, reinforcement, separation, and containment.

Geosynthetics are available in a wide range of forms and materials, each to suit a slightly different end-use, although they are frequently used together. Some reinforcement geosynthetics, such as geogrids and more recently, cellular confinement systems, have shown to improve bearing capacity, modulus factors and soil stiffness and strength.[14] These products have a wide range of applications and are currently used in many civil and geotechnical engineering applications including roads, airfields, railroads, embankments, piled embankments, retaining structures, reservoirs, canals, dams, landfills, bank protection and coastal engineering.[15]

Offshore

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Platforms offshore Mexico.

Offshore (or marine) geotechnical engineering is concerned with foundation design for human-made structures in the sea, away from the coastline (in opposition to onshore or nearshore engineering). Oil platforms, artificial islands and submarine pipelines are examples of such structures.[16]

There are a number of significant differences between onshore and offshore geotechnical engineering.[16][17] Notably, site investigation and ground improvement on the seabed are more expensive; the offshore structures are exposed to a wider range of geohazards; and the environmental and financial consequences are higher in case of failure. Offshore structures are exposed to various environmental loads, notably wind, waves and currents. These phenomena may affect the integrity or the serviceability of the structure and its foundation during its operational lifespan and need to be taken into account in offshore design.

In subsea geotechnical engineering, seabed materials are considered a two-phase material composed of rock or mineral particles and water.[18][19] Structures may be fixed in place in the seabed—as is the case for piers, jetties and fixed-bottom wind turbines—or may comprise a floating structure that remains roughly fixed relative to its geotechnical anchor point. Undersea mooring of human-engineered floating structures include a large number of offshore oil and gas platforms and, since 2008, a few floating wind turbines. Two common types of engineered design for anchoring floating structures include tension-leg and catenary loose mooring systems.[20]

Observational method

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First proposed by Karl Terzaghi and later discussed in a paper by Ralph B. Peck, the observational method is a managed process of construction control, monitoring, and review, which enables modifications to be incorporated during and after construction. The method aims to achieve a greater overall economy without compromising safety by creating designs based on the most probable conditions rather than the most unfavorable.[21] Using the observational method, gaps in available information are filled by measurements and investigation, which aid in assessing the behavior of the structure during construction, which in turn can be modified per the findings. The method was described by Peck as "learn-as-you-go".[22]

The observational method may be described as follows:[22]

  1. General exploration sufficient to establish the rough nature, pattern, and properties of deposits.
  2. Assessment of the most probable conditions and the most unfavorable conceivable deviations.
  3. Creating the design based on a working hypothesis of behavior anticipated under the most probable conditions.
  4. Selection of quantities to be observed as construction proceeds and calculating their anticipated values based on the working hypothesis under the most unfavorable conditions.
  5. Selection, in advance, of a course of action or design modification for every foreseeable significant deviation of the observational findings from those predicted.
  6. Measurement of quantities and evaluation of actual conditions.
  7. Design modification per actual conditions

The observational method is suitable for construction that has already begun when an unexpected development occurs or when a failure or accident looms or has already happened. It is unsuitable for projects whose design cannot be altered during construction.[22]

See also

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  • Civil engineering
  • Deep Foundations Institute
  • Earthquake engineering
  • Earth structure
  • Effective stress
  • Engineering geology
  • Geological Engineering
  • Geoprofessions
  • Hydrogeology
  • International Society for Soil Mechanics and Geotechnical Engineering
  • Karl von Terzaghi
  • Land reclamation
  • Landfill
  • Mechanically stabilized earth
  • Offshore geotechnical engineering
  • Rock mass classifications
  • Sediment control
  • Seismology
  • Soil mechanics
  • Soil physics
  • Soil science

 

Notes

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  1. ^ a b c d Das, Braja (2006). Principles of Geotechnical Engineering. Thomson Learning.
  2. ^ a b Budhu, Muni (2007). Soil Mechanics and Foundations. John Wiley & Sons, Inc. ISBN 978-0-471-43117-6.
  3. ^ a b Disturbed soil properties and geotechnical design, Schofield, Andrew N., Thomas Telford, 2006. ISBN 0-7277-2982-9
  4. ^ Guerriero V., Mazzoli S. (2021). "Theory of Effective Stress in Soil and Rock and Implications for Fracturing Processes: A Review". Geosciences. 11 (3): 119. Bibcode:2021Geosc..11..119G. doi:10.3390/geosciences11030119.
  5. ^ Soil Mechanics, Lambe, T.William and Whitman, Robert V., Massachusetts Institute of Technology, John Wiley & Sons., 1969. ISBN 0-471-51192-7
  6. ^ Soil Behavior and Critical State Soil Mechanics, Wood, David Muir, Cambridge University Press, 1990. ISBN 0-521-33782-8
  7. ^ Terzaghi, K., Peck, R.B. and Mesri, G. (1996), Soil Mechanics in Engineering Practice 3rd Ed., John Wiley & Sons, Inc. ISBN 0-471-08658-4
  8. ^ Holtz, R. and Kovacs, W. (1981), An Introduction to Geotechnical Engineering, Prentice-Hall, Inc. ISBN 0-13-484394-0
  9. ^ Deep Scan Tech (2023): Deep Scan Tech uncovers hidden structures at the site of Denmark's tallest building.
  10. ^ "Geofrost Coring". GEOFROST. Retrieved 20 November 2020.
  11. ^ a b Han, Jie (2015). Principles and Practice of Ground Improvement. Wiley. ISBN 9781118421307.
  12. ^ RAJU, V. R. (2010). Ground Improvement Technologies and Case Histories. Singapore: Research Publishing Services. p. 809. ISBN 978-981-08-3124-0. Ground Improvement – Principles And Applications In Asia.
  13. ^ Pariseau, William G. (2011). Design analysis in rock mechanics. CRC Press.
  14. ^ Hegde, A.M. and Palsule P.S. (2020), Performance of Geosynthetics Reinforced Subgrade Subjected to Repeated Vehicle Loads: Experimental and Numerical Studies. Front. Built Environ. 6:15. https://www.frontiersin.org/articles/10.3389/fbuil.2020.00015/full.
  15. ^ Koerner, Robert M. (2012). Designing with Geosynthetics (6th Edition, Vol. 1 ed.). Xlibris. ISBN 9781462882892.
  16. ^ a b Dean, E.T.R. (2010). Offshore Geotechnical Engineering – Principles and Practice. Thomas Telford, Reston, VA, 520 p.
  17. ^ Randolph, M. and Gourvenec, S., 2011. Offshore geotechnical engineering. Spon Press, N.Y., 550 p.
  18. ^ Das, B.M., 2010. Principles of geotechnical engineering. Cengage Learning, Stamford, 666 p.
  19. ^ Atkinson, J., 2007. The mechanics of soils and foundations. Taylor & Francis, N.Y., 442 p.
  20. ^ Floating Offshore Wind Turbines: Responses in a Sea state – Pareto Optimal Designs and Economic Assessment, P. Sclavounos et al., October 2007.
  21. ^ Nicholson, D, Tse, C and Penny, C. (1999). The Observational Method in ground engineering – principles and applications. Report 185, CIRIA, London.
  22. ^ a b c Peck, R.B (1969). Advantages and limitations of the observational method in applied soil mechanics, Geotechnique, 19, No. 1, pp. 171-187.

References

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  • Bates and Jackson, 1980, Glossary of Geology: American Geological Institute.
  • Krynine and Judd, 1957, Principles of Engineering Geology and Geotechnics: McGraw-Hill, New York.
  • Ventura, Pierfranco, 2019, Fondazioni, Volume 1, Modellazioni statiche e sismiche, Hoepli, Milano
[edit]
  • Worldwide Geotechnical Literature Database

 

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Radon mitigation is any process used to reduce radon gas concentrations in the breathing zones of occupied buildings, or radon from water supplies. Radon is a significant contributor to environmental radioactivity and indoor air pollution. Exposure to radon can cause serious health problems such as lung cancer.[1]

Mitigation of radon in the air by active soil depressurization is most effective. Concrete slabs, sub-floors, and/or crawlspaces are sealed, an air pathway is then created to exhaust radon above the roof-line, and a radon mitigation fan is installed to run permanently. In particularly troublesome dwellings, air exchangers can be used to reduce indoor radon concentrations. Treatment systems using aeration or activated charcoal are available to remove radon from domestic water supplies. There is no proven link between radon in water and gastrointestinal cancers; however, extremely high radon concentrations in water can be aerosolized by faucets and shower heads and contribute to high indoor radon levels in the air.

Testing

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A typical radon test kit
Fluctuation of ambient air radon concentration over one week, measured in a laboratory

The first step in mitigation is testing. No level of radiation is considered completely safe, but as it cannot be eliminated, governments around the world have set various action levels to provide guidance on when radon concentrations should be reduced. The World Health Organization's International Radon Project has recommended an action level of 100 Bq/m3 (2.7 pCi/L) for radon in the air.[2] Radon in the air is considered to be a larger health threat than radon in domestic water. The US Environmental Protection Agency recommendation is to not test for radon in water unless a radon in air test shows concentrations above the action level. However, in some U.S. states such as Maine where radon levels are higher than the national average, it is recommend that all well water should be tested for radon. The U.S. government has not set an action level for radon in water.

Air-radon levels fluctuate naturally on a daily and seasonal basis. A short term test (90 days or less) might not be an accurate assessment of a home's average radon level, but is recommended for initial testing to quickly determine unhealthy conditions. Transient weather such as wind and changes in barometric pressure can affect short-term concentrations as well as ventilation, such as open windows and the operation of exhaust fans.

Testing for radon in the air is accomplished using passive or active devices placed in the building. Some devices are promptly sent to a laboratory for analysis, others calculate the results on-site including digital Radon detectors. Radon-in-water testing requires a water sample being sent to a laboratory.

Retesting is recommended in several situations, for example, before spending money on the installation of a mitigation system. Test results which exceed accuracy tolerances also require re-testing. When a mitigation system installation is warranted, a retest after the system is functional is advised to be sure the system is effectively reducing the radon concentration below the action level, and after any mitigation system repairs such as replacing a fan unit. The US EPA recommends retesting homes with radon problems every two years to ensure proper system function. Due to the vast fluctuation in indoor radon levels, the EPA recommends all homes be tested at least once every five years.[3]

Testing in the United States

[edit]
Radon map of the United States

ASTM E-2121 is a US standard for reducing airborne radon in homes as far as practicable below the action level of 4 picocuries per liter (pCi/L) (148 Bq/m3).[4][5] Some states recommend achieving 2.0 pCi/L or less.

Radon test kits are commercially available[6] and can be used by homeowners and tenants and in limited cases by landlords, except when a property is for sale.

Commercially available test kits include a passive collector that the user places in the lowest livable floor of the house for 2 to 7 days. The user then sends the collector to a laboratory for analysis. Long-term kits, taking collections from 91 days to one year, are also available. Open land test kits can test radon emissions from the land before construction begins, but are not recommended by the EPA because they do not accurately predict the final indoor radon level. The EPA and the National Environmental Health Association have identified 15 types of radon test devices.[7] A Lucas cell is one type of device.

Retesting is specifically recommended in several situations. Measurements between 4 and 10 pCi/L (148 and 370 Bq/m3) warrant a follow-up short-term or long-term radon test before mitigation. Measurements over 10 pCi/L (370 Bq/m3) warrant only another short-term test (not a long-term test) so that abatement measures are not unduly delayed.

Progress has been made regarding radon in the home. A total of 37 states have now[when?] passed legislation requiring home-sellers to disclose known radon levels before completing the transaction (although only a handful have introduced criminal penalties for misrepresentation).[8] And over half the legislatures have written radon into their state's building code.[9] Purchasers of real estate may delay or decline a purchase if the seller has not successfully abated radon to less than 4 pCi/L.

The accuracy of the residential radon test depends upon whether closed house conditions are maintained. Thus the occupants will be instructed not to open windows, etc., for ventilation during the pendency of test, usually two days or more. However, the occupants, if the present owners, will be motivated to pass the test and insure the sale, so they might be tempted to open a window to get a lower radon score. Moreover, there may be children or immature teens or young adults in the house who will open a window for ventilation notwithstanding instructions not to do so, particularly in uncomfortably hot weather. Accordingly, whether the potential purchaser should trust the result of such a test is problematic.

Management of radon service provider certification has evolved since being introduced by the EPA in 1986. In the 1990s this service was "privatized" and the National Environmental Health Association (NEHA) helped transition the voluntary National Radon Proficiency Program (NRPP) to be administered by private firms. As of 2012, the NRPP is administered by the American Association of Radon Scientists and Technologists (AARST).[10]

Some states, such as Maine, require landlords to test their rental properties and turn the results in to the state. In limited cases the landlord or tenants may do the testing themselves. The rules in each state vary. In many cases there are private contractors that will inspect hired by the city.

Testing in Canada

[edit]

Health Canada recommends regular annual testing, either by hiring a qualified tester or by using a home-testing kit that should be checked quarterly.[11]

Canadian Government, in conjunction with the territories and provinces, developed the guideline[12] to indicate when remedial action should be taken was originally set at 800 Bq/m3 (becquerels per cubic meter) and since reduced to 200 Bq/m3. This new guideline was approved by the Federal Provincial Territorial Radiation Protection Committee in October 2006.[13]

Testing in the UK

[edit]

Radon testing in the UK is managed by UKradon and the UKHSA.[14]

Testing in Norway

[edit]

The Norwegian Radiation and Nuclear Safety Authority (DSA) developed the protocol[15] for radon measurements in residential dwellings[16] with respect to rental accommodation, which is governed by The Radiation Protection Regulations.[17]

Methods of radon gas mitigation

[edit]
Part of a radon mitigation system including the fan and vent pipe is visible near the gutter downspout.

Because high levels of radon have been found in every state of the United States,[18] testing for radon and installing radon mitigation systems has become a specialized industry since the 1980s. Many states have implemented programs that affect home buying and awareness in the real estate community; however, radon testing and mitigation systems are not generally mandatory unless specified by the local jurisdiction.[19]

Anticipated high radon levels can be mitigated during building design and construction by a combination of ensuring a perfectly sealed foundation, allowing sufficient passive dispersal of under-slab gas around rather than through the building, and proper building ventilation. In many instances, such approaches may achieve a sufficient reduction of radon levels compared to other buildings where such approaches were not taken. However, quality of implementation is crucial and testing after construction is necessary. For instance, even a small gap in the sealing of the slab may be sufficient for excessive quantities of radon to enter, given pressure differentials.

Where such approaches were not taken during construction or have proven insufficiently effective, remediation is needed. According to the EPA's "A Citizen's Guide to Radon",[20] the method to reduce radon "primarily used is a vent pipe system and fan, which pulls radon from beneath the house and vents it to the outside", which is also called sub-slab depressurization, soil suction, or active soil depressurization (ASD). Generally indoor radon can be mitigated by sub-slab depressurization and exhausting such radon-laden air to the outdoors, away from windows and other building openings.[21] "EPA generally recommends methods which prevent the entry of radon. Soil suction, for example, prevents radon from entering your home by drawing the radon from below the home and venting it through a pipe, or pipes, to the air above the home where it is quickly diluted" and "EPA does not recommend the use of sealing alone to reduce radon because, by itself, sealing has not been shown to lower radon levels significantly or consistently" according to the EPA's "Consumer's Guide to Radon Reduction: How to Fix Your Home".[22] Ventilation systems can utilize a heat exchanger or energy recovery ventilator to recover part of the energy otherwise lost in the process of exchanging air with the outside. For crawlspaces, the EPA states,[22] "An effective method to reduce radon levels in crawlspace homes involves covering the earth floor with a high-density plastic sheet. A vent pipe and fan are used to draw the radon from under the sheet and vent it to the outdoors. This form of soil suction is called submembrane suction, and when properly applied is the most effective way to reduce radon levels in crawlspace homes."

High radon levels in a Minnesota (USA) basement with a passive under slab vent pipe system can be seen in the left half of the graph. After installation of a radon fan (ASD), a permanent reduction in radon levels to approximately 0.6 pCi/L can be seen in the right half of the graph.
  • The most common approach is active soil depressurization (ASD). Experience has shown that ASD is applicable to most buildings since radon usually enters from the soil and rock underneath and mechanical ventilation is used when the indoor radon is emitted from the building materials. A less common approach works efficiently by reducing air pressures within cavities of exterior and demising walls where radon emitting from building materials, most often concrete blocks, collects.
  • Above slab air pressure differential barrier technology (ASAPDB) requires that the interior pressure envelope, most often drywall, as well as all ductwork for air conditioning systems, be made as airtight as possible. A small blower, often no more than 15 cubic feet per minute (0.7 L/s) may then extract the radon-laden air from these cavities and exhaust it to the out of doors. With well-sealed HVAC ducts, very small negative pressures, perhaps as little as 0.5 pascal (0.00007 psi), will prevent the entry of highly radon-laden wall cavity air from entering into the breathing zone. Such ASAPDB technology is often the best radon mitigation choice for high-rise condominiums as it does not increase indoor humidity loads in hot humid climates, and it can also work well to prevent mold growth in exterior walls in heating climates.
  • In hot, humid climates, heat recovery ventilators (HRV) as well as energy recovery ventilators (ERV) have a record of increasing indoor relative humidity and dehumidification demands on air conditioning systems. Mold problems can occur in homes that have been radon mitigated with HRV and ERV installations in hot, humid climates.[citation needed] HRVs and ERVs have an excellent record in cold dry climates.
  • A recent technology is based on building science. It includes a variable rate mechanical ventilation system that prevents indoor relative humidity from rising above a preset level such as 50% which is currently suggested by the US Environmental Protection Agency and others as an upper limit for the prevention of mold. It has proven to be especially effective in hot, humid climates. It controls the air delivery rate so that the air conditioner is never overloaded with more moisture than it can effectively remove from the indoor air.
    • It is generally assumed that air conditioner operation will remove excess moisture from the air in the breathing zone, but it is important to note that just because the air conditioner cools does not mean that it is also dehumidfying. If Δt is 14 degrees or less, it may not dehumidify at all even though it is cooling.
    • Factors that are likely to aggravate indoor humidity problems from mechanical ventilation–based radon installations are as follows and an expert radon mitigator/building scientist will check for and correct any and all of the following when he or she performs radon mitigation procedures:
      • Air conditioner duct leaks located outside the breathing zone, such as in the attic.
      • Excessive exhaust fan operation
      • Oversize or over-capacity air conditioners
      • AC air handler fans that do not stop running when the air conditioner compressor stops running.
      • Delta tt), which is the amount that the air is cooled as it is passed through the air conditioner's cooling coils. A good Δt performance figure for home air conditioners is about 20 °F (11 °C). In comparison, automobile air conditioners deliver Δt performance of 32 to 38 °F (18 to 21 °C). A Δt of 14 °F (8 °C) will dehumidify poorly if at all.

In South Florida, most radon mitigation is performed by use of fixed rate mechanical ventilation. Radon mitigation training in Florida does not include problems associated with mechanical ventilation systems, such as high indoor humidity, mold, moldy odors, property damage or health consequences of human occupation in high humidity of moldy environments[citation needed]. As a result, most Florida radon mitigators are unaware of and do not incorporate existing building science moisture management technology into mechanical ventilation radon installations. Home inspectors may not necessarily be aware of the mold risks associated with radon mitigation by mechanical ventilation.

The average cost for an ASD radon mitigation system in Minnesota is $1500.[23] These costs are very dependent on the type of home and age of construction.[24]

Methods of radon-in-water mitigation

[edit]

Radon removal from water supplies may be at a treatment plant, point of entry, or point of use. Public water supplies in the United States were required to treat for radionuclides beginning in 2003 but private wells are not regulated by the federal government as of 2014. The radon can be captured by granular activated charcoal (GAR) or released into the air through aeration of the water. Radon will naturally dissipate from water over a period of days, but the quantity of storage needed to treat the water in this manner makes home systems of this type impracticably large.[25]

Activated carbon systems capture radon from the water. The amount of radiation accumulates over time and the filter material may reach the level of requiring disposal as a radioactive waste. However, in the United States there are no regulations concerning radiation levels and disposal of radon treatment waste as of 2014.

Aeration systems move the radon from the water to the air. Radon gas discharged into the air is the release of a pollutant, and may become regulated in the United States.

References

[edit]
  1. ^ Nunnally, Diamond (2022-03-30). "Dangerous radon gas dangers and detection tips". WBMA. Retrieved 2022-04-10.
  2. ^ WHO Handbook on Indoor Radon: A Public Health Perspective. World Health Organization. 2009.
  3. ^ US EPA, OAR (2013-08-27). "Radon". www.epa.gov. Retrieved 2023-02-04.
  4. ^ "Recommended Residential Radon Mitigation Standard of Practice". United States Environmental Protection Agency. Archived from the original on 2008-01-16. Retrieved 2008-02-02.
  5. ^ "ASTM E2121-03 Standard Practice for Installing Radon Mitigation Systems in Existing Low-Rise Residential Buildings". ASTM International. Retrieved 2008-02-02.
  6. ^ "Commercially Available Radon Kits". Alpha Energy Labs. Archived from the original on 2012-07-12. Retrieved 2012-04-19.
  7. ^ "Radon Measurement Method Definitions". The National Environmental Health Association—National Radon Proficiency Program. Archived from the original on 2007-12-24. Retrieved 2008-02-02.
  8. ^ "State Radon Laws". lawatlas.org. Retrieved 2021-07-12.
  9. ^ "National Conference of State Legislatures (NCSL) - Radon".
  10. ^ "National Radon Proficiency Program - NEHA and NEHA-NRPP History". Nrpp.info. Retrieved 2015-03-30.
  11. ^ "Home radon testing important for health". lethbridgeherald.com. 18 March 2022. Retrieved 2022-04-10.
  12. ^ "Radon Gas | Vancouver, BC, Canada". Radoncontrol.ca. Retrieved 2015-03-30.
  13. ^ "Radon Frequently Asked Questions - Health Canada". Hc-sc.gc.ca. 2014-07-30. Retrieved 2015-03-30.
  14. ^ "UKradon - Home". www.ukradon.org.
  15. ^ "Radon measurements in residential dwellings".
  16. ^ "Radon boliger 2013" (PDF).
  17. ^ "Legislation".
  18. ^ "Radon: Myth vs Fact". Radon-Rid/EPA. Retrieved 2009-11-13.
  19. ^ "Listing of States and Jurisdictions with RRNC Codes". EPA. Retrieved 2009-11-13.
  20. ^ "A Citizen's Guide to Radon" (PDF). EPA. Retrieved 2024-12-27.
  21. ^ "Radon Mitigation Methods". Radon Solution. Archived from the original on 2008-12-15. Retrieved 2008-12-02.
  22. ^ a b "Consumer's Guide to Radon Reduction: How to Fix Your Home" (PDF). EPA.
  23. ^ "Radon Mitigation System - EH: Minnesota Department of Health". Health.state.mn.us. 2014-12-10. Retrieved 2019-03-26.
  24. ^ "Featured Radon Mitigation System Archives". Radonreductioninc.com. Retrieved 2015-03-30.
  25. ^ ""Radon in Drinking Water Health Risk Reduction and Cost Analysis: Notice"" (PDF). Federal Register. 64. February 26, 1999. Retrieved 2015-03-30.
[edit]
  • Radon at the United States Environmental Protection Agency
  • National Radon Program Services hosted by Kansas State University
  • Radon and Lung Health from the American Lung Association
  • It's Your Health - Health Canada
  • Radon's impact on your health – Quebec Lung Association

 

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Jeffery James

(5)

Very happy with my experience. They were prompt and followed through, and very helpful in fixing the crack in my foundation.

Sarah McNeily

(5)

USS was excellent. They are honest, straightforward, trustworthy, and conscientious. They thoughtfully removed the flowers and flower bulbs to dig where they needed in the yard, replanted said flowers and spread the extra dirt to fill in an area of the yard. We've had other services from different companies and our yard was really a mess after. They kept the job site meticulously clean. The crew was on time and friendly. I'd recommend them any day! Thanks to Jessie and crew.

Jim de Leon

(5)

It was a pleasure to work with Rick and his crew. From the beginning, Rick listened to my concerns and what I wished to accomplish. Out of the 6 contractors that quoted the project, Rick seemed the MOST willing to accommodate my wishes. His pricing was definitely more than fair as well. I had 10 push piers installed to stabilize and lift an addition of my house. The project commenced at the date that Rick had disclosed initially and it was completed within the same time period expected (based on Rick's original assessment). The crew was well informed, courteous, and hard working. They were not loud (even while equipment was being utilized) and were well spoken. My neighbors were very impressed on how polite they were when they entered / exited my property (saying hello or good morning each day when they crossed paths). You can tell they care about the customer concerns. They ensured that the property would be put back as clean as possible by placing MANY sheets of plywood down prior to excavating. They compacted the dirt back in the holes extremely well to avoid large stock piles of soils. All the while, the main office was calling me to discuss updates and expectations of completion. They provided waivers of lien, certificates of insurance, properly acquired permits, and JULIE locates. From a construction background, I can tell you that I did not see any flaws in the way they operated and this an extremely professional company. The pictures attached show the push piers added to the foundation (pictures 1, 2 & 3), the amount of excavation (picture 4), and the restoration after dirt was placed back in the pits and compacted (pictures 5, 6 & 7). Please notice that they also sealed two large cracks and steel plated these cracks from expanding further (which you can see under my sliding glass door). I, as well as my wife, are extremely happy that we chose United Structural Systems for our contractor. I would happily tell any of my friends and family to use this contractor should the opportunity arise!

Chris Abplanalp

(5)

USS did an amazing job on my underpinning on my house, they were also very courteous to the proximity of my property line next to my neighbor. They kept things in order with all the dirt/mud they had to excavate. They were done exactly in the timeframe they indicated, and the contract was very details oriented with drawings of what would be done. Only thing that would have been nice, is they left my concrete a little muddy with boot prints but again, all-in-all a great job

Dave Kari

(5)

What a fantastic experience! Owner Rick Thomas is a trustworthy professional. Nick and the crew are hard working, knowledgeable and experienced. I interviewed every company in the area, big and small. A homeowner never wants to hear that they have foundation issues. Out of every company, I trusted USS the most, and it paid off in the end. Highly recommend.

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