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CPT Dictionary: Soil Liquefaction

- Posted by VertekCPT

Sand boils are a dramatic manifestation of soil liquefaction, shown here in a 2011 earthquake in Christchurch, New Zealand. Source: http://resources0.news.com.au/images/2011/02/23/1226010/776488-a-vehicle-stuck-in-the-liquification.jpg

In our last blog, we discussed using the CPT to estimate the shear strength of soil, which helps gauge how soil will behave during changes in stress. One important application of this capability is the estimation of soil liquefaction potential, meaning the potential of soil to dramatically lose strength when subjected to changes in stress.

Liquefaction is of particular concern in sandy, saturated soils. Shaking due to an earthquake or other sudden force causes the grains of loosely packed, sandy soils to settle into a denser configuration. If the soil is saturated and the loading is rapid, pore water does not have time to move out of the way of settling soil: pore water pressure rises, effectively pushing the soil grains apart and allowing them to move more freely relative to each other. At this point, the soil can shift and flow like a liquid—hence the name liquefaction.

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Topics: Experienced, Cone Penetration, Soil Testing, CPT Dictionary

CPT Dictionary: Soil Shear Strength

- Posted by VertekCPT

Geological stresses (image source: http://earthquake.usgs.gov/learn/glossary/images/stress_types.gif)Shear strength is the ability of a material to resist shear forces—that is, forces that produce a sliding failure in the material parallel to the direction of the force. The diagram at right demonstrates shear stress, along with tensional and compressional stress. (What's the difference between a stress and a force? Stress is defined as force per area.)

How is this relevant to soil testing? Well, consider a sliding failure in soil, such as occurs along a fault plane in an earthquake. Shear strength tells us a great deal about how the soil will behave under shear forces and during changes in stress, for example due to an earthquake or excavation. 

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Topics: Experienced, Soil Testing, CPT Dictionary

Grow your Business by Increasing your Geotechnical Services

- Posted by VertekCPT

introductory

geotechnical-services

If you're looking for ways to help grow your business, consider expanding your geotechnical services. By increasing the geotechnical services your company offers, you'll be able to expand your current client base and increase your workload. To realize these benefits, you'll first have to decide which geotechnical services you can offer, which you could offer more in-depth, how it would affect your current workload, and how it can increase your revenue. 

What Geotechnical Services Can your Business Offer?

  1. Rental and sales of equipment
  2. Field exploration (soil and rock sampling, test boring, core drilling, electro-magnetic surveying, etc.)
  3. Site evaluation (for pavement/ sub grades, alternative site and route studies, definition of critical geotechnical parameters)
  4. Engineering analysis and design (slope stability evaluation, hillside grading recommendations, earth retaining structure design, earthquake damage analysis)
  5. Laboratory testing services (soil classification, shear strength, permeability, consolidation characteristics, resistivity)
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Topics: Experienced, Introductory, Geotechnical Services

What Information Should you Include in a Geotechical Report?

- Posted by VertekCPT

experienced

geotechnical-report-informationIt could be that you've learned everything there is to know about Cone Penetration Testing, but if you don't know about geotechnical reporting, you're missing out on a big step in the process. A geotechnical report is a tool used to communicate site conditions, as well as design and construction recommendations to be relayed to personnel. In other words, you're taking the results of your CPT testing and putting them into an easy-to-understand report along with relevant conclusions. Sound simple? There's more to it than you might think.

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Topics: Experienced, CPT Data

Geotechnical Investigation and CPT Papers Now Available From CPT '14

- Posted by VertekCPT

Did you attend CPT '14 in Las Vegas, Nevada?CPT14

If so then you know the wealth of geotechnical expertise that was shared, and if not, then be sure to examine the scope of professional papers published from the event available for review now on their website.

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Topics: Experienced

Cone Penetrometer Testing via Speed Lock Rods

- Posted by VertekCPT

experienced

The strongest direct push rods in cone penetration testing.

Unsurpassed Joint Strength

Vertek manufactures a full line of CPT push rods with our proprietary Speed Lock dual-lead thread design. Speed Lock Rods provide unsurpassed joint strength, up to 50% stronger than industry standard V-threads. Our unique rope thread design uses less of the available wall thickness and balances the strength between the male and female thread ends. Speed Lock coupled joint achieves nearly 90% of the strength of the heat treated rod stock.

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Topics: Experienced

Ensuring That Your CPT Data is Correctly Reported and Interpreted

- Posted by VertekCPT

experienced

cpt-dataIt is important to understand when interpreting CPT data the physics of how the data is produced.

This will lead to a better appreciation of where CPT data should be validated with other types of tests in order to ensure that it is being correctly reported and interpreted. 

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Topics: Experienced, Cone Penetration, Soil Testing

Measuring the Moisture Content of Soil Using CPT

- Posted by VertekCPT

experienced

moisture-content-of-soilMeasuring soil moisture content can be important for a variety of reasons.

In placing underground electrical equipment or digging tunnels, it can be essential to know exactly what soil moisture conditions look like at specific depths.

Early CPT test procedures used the standard CPT output data of cone resistance, sleeve friction and friction ratio to identify all of the parameters underground. When it comes to soils that have some moisture content or are saturated, it can be helpful to use a boring rig to obtain soil samples at depth close to the first CPT sounding. This enables you to ‘calibrate’ your rig to the site to ensure that the interpretations of the test data are accurate.

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Topics: Experienced

Screening for Soil Contamination Levels with CPT

- Posted by VertekCPT

experienced

soil-contamination-screeningExpanding from geotechnical Cone Penetration Test (CPT) into other services is a great way to grow your business. Evaluating subsurface soil contamination provides many business opportunities and a way to differentiate yourself from other CPT service providers – allowing you to protect your business, while expanding into new regions and adding clients.

In many instances, the existence of environmental contaminations in an area is known, but the question that needs to be answered is, “where is it”? In other postswe explain how CPT works, and how it can be used to characterize the strata underground hundreds of feet deep, depending upon the actual subsurface conditions, the equipment being used etc., In addition to identifying soil types by layer and depth, geo-technical CPT testing also helps to establish groundwater levels and potential migration pathways. This makes it useful for identifying where contamination may migrate or be confined. Establishing a depth profile of the contamination underground and how the ‘plume’ is located and migrated, or where it is likely to expand in the future is vital to establishing a cleanup or remediation plan. Once contamination has been shown to be likely, our discrete soil and ground water sampling equipment delivers physical samples for confirmation.

 

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Topics: Experienced