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The Application of Dynamic Cone Penetration Testing (DCPT)

Assessing the level of compaction of sub-surface soils can be essential to designing and building structures, particularly those subject to transient or cycling loads. A perfect example is roadways. If the soil beneath a roadway is not compacted sufficiently, then over time the cycling loads of passing traffic will compact the soil further, leading to surface failure such as large cracks, potholes and displaced pavement. Assessing the compaction of non-cohesive soils such as fine sands is a difficult challenge. As we've noted in other blog posts, removing a sample from the ground and sending it to a lab is not only time consuming and expensive, but can be highly inaccurate in non-cohesive soils because the samples by necessity are disturbed from their sub-surface condition. The Dynamic Cone Penetrometer Test (DCPT) is one of many forms of in-situ soil characteristic tests that are designed to assess soil density. It shares some characteristics of both SPT and CPT testing, which enables it to provide a useful and in the right application can deliver a complementary data set and is less expensive and troublesome than Nuclear Density testing. The Standard Penetration Test (SPT) is done by using a sample tube which has thick walls to prevent deformation during the test. To conduct a test, a borehole is drilled to a specified depth. The sample tube is driven into the bottom of the borehole using a drop hammer of a defined weight dropped a defined distance. The number of blows (N) needed to drive the sample tube 6, 12 and 18 inches is recorded. The SPT provides a rough indication of the soil density at depth. As noted in previous posts (link here), getting accurate data for soil density can be a complex challenge. SPT provides an estimate but is not as accurate as [...]

By smadi66|December 3rd, 2019|Geotechnical Colorado, Geotechnical Virginia, Geotechnical Washington, Geotechnical Wyoming, Geotechnical Wisconsin, Geotechnical Alabama, Geotechnical West Virginia, Soil Testing, Geotechnical Arizona, Geotechnical Arkansas, Geotechnical California|0 Comments

Ensure Properties are Accurate Using Sediment Cone Testing

Obtaining a representative and undisturbed sample of cohesive sedimentary soil, such as sand, is very difficult and often times impossible. Because of this, determining the properties of sandy or fine grained soils is best done in-situ, making Cone Penetration Testing (CPT) one of the best testing methods for measuring mechanical properties of sediment. Sediment Cone Testing When conducting cone testing of sediment the horizontal stress and sediment density are the most influential parameters on the cone tip resistance. The cone penetration tip resistance is influenced by the soil properties ahead and below the tip. If you're dealing with a sand layer that is less than 70 cm., it's important to consider what types of stratification it is located between. For example, if it's located between deposits of soft clay the CPT may not reach it's full value within the sand layer, meaning the relative density of the sand may be underestimated. By monitoring the CPT pore pressures, these influencers can be identified. The substantial effects of soil compressibility on CPT measurements are considered to be an advantage if they are identified correctly. Compressibility is one of the key factors to successfully determining soil properties and classifying soil types. Using CPT, relative density and friction measurements soils can be broken up into high, medium and low compressibility. By classifying sediment compressibility during cone testing you can better measure the particular sediment properties. Sand for example, originates from quartz or silica; it contains hard materials, does not have cleavage planes and is resistant to weathering. Certain sands, for example siliceous sand, contain trace portions of other minerals, like chlorite. Compared to other types of soil, the compressibility of sand is most complicated because it is dependent on several different factors, including: grain size and shape, particle crush-ability, angularity, grain mineralogy, void ratio, [...]

By smadi66|December 3rd, 2019|Geotechnical California, Geotechnical Colorado, Geotechnical Delaware, Geotechnical Wyoming, Geotechnical Wisconsin, Geotechnical Alabama, Geotechnical Connecticut, Geotechnical West Virginia, Experienced, Geotechnical Arizona, Geotechnical Arkansas|0 Comments

When Should You Consider SPT Testing Over CPT?

If you’ve been following the CPT University, you likely already know that Cone Penetration Testing isn’t the only method of testing soil. Mud rotary drilling, for example, has come up in the past along with one of the best known soil testing procedures out there: the Standard Penetration Test (SPT). Like Cone Penetration Testing, SPT Testing is widely used. But can it outperform CPT Testing? Read on to find out. What is SPT Testing? SPT Testing uses a thick sample tube to determine the relative density of granular deposits, typically sand and gravel. The sample tube is placed at the bottom of a borehole and struck with a heavy slide hammer repeatedly. The number of hammer strikes is important; the test operator must track how many strikes it takes to drive the sample tube 6 inches into the soil. The test is completed when the sample tube reaches 18 inches deep. As you might imagine, a test that requires only a sample tube and a hammer offers a few notable benefits, namely that it is simple and inexpensive to perform. It is also the best solution for testing soil in areas that are difficult to access with vehicles. In other words, if you need to perform a soil test quickly, easily and at minimal cost, SPT Testing is hard to beat. SPT Testing does have its drawbacks, though. Most notably, it’s inaccurate compared to more advanced methods, especially when sampling coarse sands or clay. As such, it’s rare to encounter a scenario in which SPT Testing is preferable to Cone Penetration Testing. Not only is CPT far more accurate than the standard penetration test, it also manages to be relatively inexpensive compared to other testing methods. CPT is also a fast, safe and versatile option. Sure, it can’t match the [...]

By smadi66|December 3rd, 2019|Geotechnical California, Geotechnical Colorado, Geotechnical Delaware, Geotechnical Wyoming, Geotechnical Georgia, Geotechnical Alabama, Geotechnical Connecticut, Geotechnical Florida, Introductory, Geotechnical Arizona, Geotechnical Arkansas|0 Comments

10 Essentials of Construction Testing and Engineering

Testing construction material is an important step in the building process, as the outcome of testing, as well as the processes used, will ultimately affect the safety and longevity of the final building site. While the reality on most building sites is that the accuracy of testing and cost effectiveness are often balanced, these days it's pretty easy to ensure a high degree of accuracy while still keeping costs at a minimum. Regardless, the overall goal is to establish the foundation for assisting design engineers in making good, informed decisions while meeting building code requirements. By testing construction materials, along with ensuring proper geotechnical analysis, it's possible to guarantee buildings will meet regulatory requirements and last over time. Overall, construction materials, engineering and testing (CoMET) are used to ensure quality control and construction quality assurance. However, construction testing and engineering can only go so far without some key essentials. 10 Essentials of Construction Testing and Engineering: Observation, testing and evaluation of building materials Observation, testing and evaluation of quality construction methods and processes Observation, testing and evaluation of building outcomes Meeting building code compliance Site grading and subsurface prep Soil testing and analysis; evaluation of subsurface materials Cost-effective geotechnical sliutions and materials used Safe application of contaminated subsurface materials Proper recycling of excavated materials and debris Assurance of ground stability, especially in areas common to environmental disaster such as earthquakes, flooding, etc. By making sure to follow each of these 10 essential steps, you're ensuring that every aspect of inspection is covered, in turn ensuring a stable, up-to-code building for the long run. That said, there are a couple more important points to note: CoMET services must be performed during the early stages of a project and processes must be hands-on to ensure each step is given complete attention. Getting [...]

By smadi66|December 3rd, 2019|Geotechnical Colorado, Geotechnical Delaware, Geotechnical Idaho, Geotechnical Illinois, Geotechnical Georgia, Geotechnical Connecticut, Geotechnical Florida, Introductory, Geotechnical Arizona, Geotechnical Arkansas, Geotechnical California|0 Comments

Should you Use a Sand Cone Test in Construction?

It may seem at times that there are almost too many soil testing methods, but many are developed to fit certain scenarios or address issues with other testing methods. This is the case with the sand cone test, which is used to determine soil compaction and is an alternative to using a nuclear density gauge. But does this mean the sand cone test is worth using when working on construction sites? The Pros and Cons of the Sand Cone Test There are many benefits to performing a sand cone test, especially for those relying on a nuclear density gauge. With a sand cone test, you can get similar results at a much lower cost, without the need for radioactive material. The cost of the sand cone test apparatus is also fairly low, making sand cone testing relatively inexpensive. The apparatus consists of a plastic container, a metal cone with a valve and a high density base plate. Its also relatively small and portable, making testing possible pretty much anywhere. The sand cone test has its fair share of negatives as well, including: Easy to compromise samples during testing. Soil samples are sensitive to vibrations, shifting of particles, and any errors in set up of the test site Samples that contain mixed particles can be less accurate Samples that contain too much moisture content can be less accurate Long result time: 20 minutes (vs. nuclear gauge which only takes 1 minute for results) Technicians, of course, should be aware of the limitations of the sand cone test as many factors can skew its results. In other words, the sand cone test may not be worth using when working on construction sites, except to confirm observations and inform opinions about soil moisture and density. This is especially true when you consider that [...]

By smadi66|December 3rd, 2019|Geotechnical Colorado, Geotechnical Delaware, Geotechnical Indiana, Geotechnical Idaho, Geotechnical Illinois, Geotechnical Georgia, Geotechnical Connecticut, Geotechnical Florida, Geotechnical Iowa, Introductory, Soil Testing, Geotechnical California|0 Comments

Is a Sieve Analysis Accurate?

If you regularly use Cone Penetration Testing on the job, you probably already know that there are a number of alternative soil testing methods out there. Some of the more common procedures include the Standard Penetration Test, which has been covered before in this blog, and the sieve analysis, also known as the gradation test. Most commonly used in civil engineering, this basic soil testing method is used to assess the particle size distribution of soil and other granular material. But is sieve analysis accurate? As is the case with Standard Penetration Testing, sieve analysis can provide accurate results, but only in the right conditions or scenarios. In fact, sieve analysis can achieve optimal accuracy only if certain conditions are met. First off, sieve analysis needs a proper representative example of soil from the building site, meaning particles must be mixed well within the testing sample. The sample must also be of the right size, so it does not overload the sieve and skew the results. In terms of equipment, sieve analysis requires: Test sieves that conform to relevant standards Reliable sieve shaker and analytical balance Error-free evaluation and documentation Proper cleaning and care of equipment, especially sieves When these conditions are met, it is possible to get accurate and consistent results from sieve analysis, but only with coarse materials larger than #100 mesh. When it comes to finer materials smaller than #100 mesh, sieve analysis becomes less accurate. The reason for this is the mechanical energy used to move particles through the dry sieve can compromise particle size. Fortunately, this can be offset somewhat with wet sieve analysis as long as the testing particles aren't changed by the addition of water. Sieve testing is also less accurate for non-spherical particles as they may have trouble fitting through the mesh. [...]

By smadi66|December 2nd, 2019|Geotechnical Washington, Geotechnical Wisconsin, Geotechnical Wyoming, Geotechnical Alabama, Geotechnical West Virginia, Introductory, Soil Testing, Geotechnical Arizona, Geotechnical Arkansas, Geotechnical California, Geotechnical Colorado, Geotechnical Virginia|0 Comments

What is DCP testing, and how does it compare to CPT?

Dynamic Cone Penetration (DCP) testing is used to measure the strength of in-situ soil and the thickness and location of subsurface soil layers. It is similar to CPT in that a metal cone is advanced into the ground to continuously characterize soil behavior. However, unlike in CPT, where the cone is driven into the ground at a constant rate by varying amounts of force, in DCP, the cone is driven by a standard amount of force from a hammer, and how far the cone moves with each blow is used to determine the soil density and properties at that level. In DCP testing, the pushing force is applied by manually dropping a single or dual mass weight (called the hammer) from a fixed height onto the push cone unit. The resulting downward movement is then measured. Unlike CPT systems, basic DCP equipment is hand-portable and may be limited to test depths of 3-4 feet: this makes it a good choice for shallow testing applications such as road bed construction and maintenance. Since DCP is essentially hand-powered, it is cheaper and more portable than CPT equipment, but the possibility of human error makes it trickier to obtain consistent and accurate data. Historically, one of the largest difficulties associated with DCP has been obtaining accurate depth difference measurements with a hand rule after each blow of the hammer. As you can imagine, taking these measurements by sight and recording them by hand can be slow, finicky work. Plus, to measure the total depth, the sum of these measurements is calculated, so it is easy to accumulate a troublesome amount of error if each measurement is even slightly off. Fortunately, handheld electronics technology has alleviated these issues to a great extent. Vertek’s Handheld DCP System uses a smartphone app and a laser rangefinder [...]

By smadi66|December 2nd, 2019|Geotechnical Connecticut, Geotechnical West Virginia, DCP, Introductory, Cone Penetration, Geotechnical Arizona, Geotechnical Arkansas, Geotechnical California, Geotechnical Colorado, Geotechnical Wisconsin, Geotechnical Delaware, Geotechnical Alabama, Geotechnical Wyoming|0 Comments

ASTM Standard Cone Penetrometer Sizes: Which is Best for Your Application?

CPT cones are available in multiple sizes, but the 10 cm2 cone is the industry standard. Other sizes, the most common of which is the 15 cm2 cone, are essentially scale models of the 10 cm2 cone, having the same proportions as specified by the ASTM Standard for CPT testing. What factors determine what cone size you should use? Most CPT cones range from 5 cm2 to 15 cm2 in cross-sectional area, though smaller cones (down to 1 cm2) are used in specialized lab or research applications. Different cone sizes have different advantages depending on the testing situation: The larger 15 cm2 size is more robust and gives more accurate cone resistance values in very soft soils. Additionally, it has more room inside for additional sensors. Smaller piezocones have faster pore pressure sensor response and thus are better suited for characterizing very thin layers of soil. The 10 cm2 cone is suitable for most applications. It is the industry standard and considered the reference penetrometer for field testing. Cones in the 5 cm2 to 15 cm2 range have been shown to produce consistent data in most soils, so corrections for different sizes are generally not needed. When using a cone outside this size range, corrections may be necessary to ensure that results are consistent with the body of CPT data: for example, very small cones tend to produce higher cone resistances than standard-size cones. If there are questions as to the effect of scaling the penetrometer to either larger or smaller size, a 10 cm2 penetrometer should be used in the same soils so that the results can be compared. Penetrometers are made of high strength steel and designed to resist abrasion by soil, but over time, normal wear and tear may blunt the cone and effect the accuracy of [...]

By smadi66|December 1st, 2019|Geotechnical Connecticut, Geotechnical Florida, Introductory, Geotechnical Arizona, Geotechnical Arkansas, Geotechnical California, Geotechnical Colorado, Geotechnical Delaware, Geotechnical Wyoming, Geotechnical Wisconsin, Geotechnical Alabama|0 Comments

Smart DCP – Get the app for instant data logging and laser accuracy!

DCP (Dynamic Cone Penetrometer) testing is a highly portable, lightweight soil testing method. It is ideal for shallow tests and can be carried by hand from one location to the next, making it a good choice for applications such as road bed construction and maintenance. However, traditional DCP testing has drawbacks: though the equipment is lightweight, the test requires two people—one to operate the hammer and the other to measure the displacement with each blow. This manual process makes the test quite labor-intensive, and human errors in measurement and recording can make it difficult to obtain consistent results The Vertek Smart DCP system takes this portable, low-cost testing method into the 21st century with laser measurement and real-time data acquisition. Rather than relying on by-hand measurement to track the displacement of the cone, our laser measurement system makes this process both instantaneous and accurate, eliminating the need for a two-person test. Displacement data is transmitted wirelessly and collected via our convenient smartphone app. Where a traditional DCP system would require two people, Smart DCP requires only one person and a phone--yet it allows the test to be completed much faster. Time and labor savings don't stop when the in-situ test is completed: rather than having to manually enter and plot your data on your laptop or computer, our smartphone app lets you log data in real time and gives you access to powerful presentation and analysis capabilities in the field. The raw and processed data can be transmitted by text or email in multiple formats. Like any other app, it can simply be downloaded from the app store on your phone and is available for iOS and Android operating systems. See the Smart DCP system in action in the video below, and check out our website for more information about [...]

By smadi66|November 29th, 2019|Geotechnical Florida, DCP, Geotechnical Arizona, Geotechnical Arkansas, Geotechnical California, Geotechnical Colorado, Geotechnical Delaware, Geotechnical Idaho, Geotechnical Georgia, Geotechnical Alabama, Geotechnical Connecticut|0 Comments