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CPT Testing, Part 1: Introduction to the Basic Concepts

If you have ever been curious about the Cone Penetration Testing (CPT) business, you have come to the right place. In today's post we are going to take a dive into the basic concepts and what expanding into CPT can do for your engineering business. Geotechnical Engineers and CPT Testing Geotechnical engineering is a branch of civil engineering that focuses on the engineering behavior of earth materials. Geotechnical engineers have been using Cone Penetration Testing (CPT) for over 40 years to assist in the design and construction of foundations, embankments and other structures. The standardized CPT works by pushing a 55-60 degree cone into the ground at a rate of 1-2 cm per second and is used to identify the conditions in the upper 100 feet of the subsurface. The data compiled from this testing is valuable for assessing the subsurface stratigraphy associated with soft materials, discontinuous lenses, organic materials, potentially liquified materials (such as sand, silt and granule gravel), and predicting landslides or ground settling. The cone resistance in conjunction with the friction ratio can also be used to determine soil types. While these results are often more accurate when referring to textbook soils, there are some major benefits to utilizing CPT techniques as opposed to drilling. In fact, there are a number of different advantages of CPT, including: economically friendly testing, as well as its ability to perform at a fast rate and effective in characterizing large volumes of soil without having to do a large number of laboratory testing. CPT is also accurate, eliminating the possibility of disturbances to soil samples and sample storage. By leveraging CPT results, engineers can determine the best methods for several aspects of design and construction projects. Detect lenses, thin layers and sand stringers. Evaluate the thickness and extent of compressible soil [...]

By smadi66|December 3rd, 2019|Geotechnical Tennessee, Geotechnical Pennsylvania, Introductory, Geotechnical Rhode Island, Geotechnical South Carolina, Geotechnical South Dakota, Geotechnical Texas, Geotechnical Utah, Geotechnical Vermont, Geotechnical Virginia, Geotechnical Washington|0 Comments

Building a CPT Truck in Less Than 3 Minutes (Video)

This short video compresses about a month of construction time on a 20 Ton CPT Truck built by Vertek CPT at our Vermont facility during the summer of 2014. CPT Trucks are popular for those looking for maximum push force and all-in-one mobility. This truck will be delivered to the customer upon completion of the internal components. Large trucks provide greater push force and improved working environs while smaller trucks provide greater mobility in tight spaces. Contact us to see which is best for you. Our new S4 Push System also provides a path to entering the CPT market with limited investment. [/fusion_youtube]

By smadi66|December 3rd, 2019|Cone Penetration, Vertek Partners, Video Posts, Geotechnical New Jersey, Geotechnical New Mexico, Geotechnical New York, Geotechnical North Dakota, Geotechnical Oklahoma, Geotechnical Ohio, Geotechnical Oregon, Geotechnical Pennsylvania, Geotechnical Rhode Island, Geotechnical North Carolina|0 Comments

What is a CPT DataPack?

Your average Cone Penetration Testing Rig is a fairly complex piece of machinery, but it can’t do its job alone. Indeed, every CPT Rig needs a DataPack, or data acquisition and analysis package (DAS), to properly measure and document soil information gathered from digital CPT cones and other sensors. But what exactly is a DataPack? Typically, CPT DataPacks like the VTK DataPack offer a simple “all-in-one” solution to commercial CPT service providers. The DataPack is most often designed to be field portable as it operates onsite during the CPT Testing process. As such, most DataPacks are best used with any commercial, off-the-shelf laptop for optimal portability. The Benefits of Automated Data Collection While sensor-specific data, such as calibration factors, serial numbers and sensor type, are in fact stored in each sensor module in the cone, that data is also automatically transmitted to the DataPack with each penetration. This automated collection of data offers a number of advantages. For starters, with the DataPack handling all the data collection, even a technician with minimal training can operate the system with relative ease. Automated data collection and analysis also reduces operator error or bias, while further speeding up the CPT Testing process as reporting is instant. This in turn allows for increased productivity and profit for the operator as many more soundings can be performed in a shift. Perhaps most importantly, the DataPack can also present information immediately in the form of a client-ready visual report. Again, this saves field engineers time as they don’t have to crunch the data manually. Since CPT is still a fairly new field, this makes it easier for technicians to make the shift to CPT from related vocations. The added confidence the DataPack offers technicians in turn helps ease the way for new entrants into the CPT [...]

By smadi66|December 3rd, 2019|Introductory, Geotechnical New York, Geotechnical North Dakota, Geotechnical Oklahoma, Geotechnical Oregon, Geotechnical Rhode Island, Geotechnical South Carolina, Geotechnical South Dakota, Geotechnical Ohio, Geotechnical Pennsylvania, Geotechnical North Carolina|0 Comments

What Information Should you Include in a Geotechical Report?

It 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. Geotechnical Report Essentials Of course, you want to include specific information in your geotechnical report like the status of substrate soil, rock and water conditions. It also goes without saying that accuracy in all areas is crucial because the data in the report will be referred to often throughout the design and construction periods, as well as after the completion of the project, primarily for resolving claims. But let's get more specific. Here are some basic must have points that should be included in every geotechnical report; keeping in mind that final content will vary somewhat depending on the business and project: Location and surface conditions: specific address, current use, surface coverings, elevation, drainage, etc. Subsurface exploration data: soil profile, exploration logs, lab or in-situ test results, ground water conditions Interpretation and analysis of data Engineering recommendations for design Anticipated problems and discussed solutions: slope stability, seismic considerations, etc. Any recommended geotechnical special provisions Include other types of geotechnical reports: foundation report, centerline soil report, landslide study report, etc. With these points as a guideline, it's possible to create a geotechnical report that covers all the right points to satisfy all parties involved in a project. This includes any government agencies that require geotechnical reports. For example, the U.S. Department of Transportation [...]

By smadi66|December 3rd, 2019|Experienced, Geotechnical North Dakota, Geotechnical Oklahoma, Geotechnical Oregon, Geotechnical Rhode Island, Geotechnical South Carolina, Geotechnical South Dakota, Geotechnical Tennessee, Geotechnical Texas, Geotechnical Ohio, Geotechnical Pennsylvania, CPT Data|0 Comments

Financing of New CPT Equipment Now Available

We're pleased to announce a partnership with Oakmont Capital Services as our preferred lending partner allowing Vertek CPT customers in the U.S. and Canada to enter the CPT business with as litte as no money down! Oakmont Capital Services is a full-service provider of commerical equipment financing. Application-only financing from $5,000 to $300,000 Most companies approved with 100% financing Quick turnaround on applications with most decisions made within 2 to 4 hours Competitive rates and terms (better than most banks) Financing available on new/used equipment with terms from 12 to 84 months Financing for start-up companies with a background in related industry U.S. and Canadian customers only Apply to finance your CPT purchase!

By smadi66|December 3rd, 2019|Geotechnical Rhode Island, Geotechnical South Carolina, Geotechnical South Dakota, Geotechnical Texas, Geotechnical Utah, Geotechnical Vermont, Geotechnical Tennessee, Geotechnical Pennsylvania, Vertek Partners, Geotechnical Oklahoma, Geotechnical Oregon|0 Comments

Intro to CPTu: What Can You Learn From Pore Pressure Data?

The most basic CPT tests classify soil based on tip resistance and sleeve friction measurements. In coarse soils and shallow testing depths, this data may be sufficient to accurately characterize the soil behavior. However, most modern CPT cones incorporate a third measurement: pore water pressure. What does this measurement mean and how can it add to our understanding of soil behavior? Pore pressure is simply a measure of the in-situ groundwater pressure, i.e. the water pressure in the “pores” between soil grains. This data is used to determine the compressibility and permeability of the soil, as well as indicating groundwater conditions. It is used to correct or “normalize” the sleeve friction and tip resistance readings in the presence of in-situ moisture and overburden stress. This is especially important in soft, fine-grained soils where in-situ moisture takes longest to dissipate, and in tests at depths greater than 100 feet. A CPT cone that is equipped with one or more pore pressure sensors is called a piezocone, and a CPT test using a piezocone is often indicated with the abbreviation CPTu. Piezocones may have between one and three pore pressure sensors, located on the cone (denoted u1), directly behind the cone (u2), or at the top of the friction sleeve (u3). Most piezocones for everyday applications use one sensor located at u2 (see image below). The pore pressure sensor consists of a porous filter (usually made of plastic resin), a small cavity of incompressible, low-viscosity fluid, and a pressure transducer. The filter and tubing between the filter and transducer must be fully saturated with fluid, usually glycerin or silicon oil, to ensure fast and accurate readings. The filter must be replaced frequently so that it does not become clogged with soil. The procedure for the CPTu test is slightly different than the [...]

By smadi66|December 2nd, 2019|Geotechnical South Dakota, Geotechnical Texas, Geotechnical Utah, Geotechnical Tennessee, Geotechnical Vermont, Geotechnical Pennsylvania, Geotechnical Virginia, CPT Data, Geotechnical Washington, Introductory, Cone Penetration, Soil Testing, Geotechnical Rhode Island, Geotechnical South Carolina|0 Comments

Intro to Seismic CPT

What is Seismic Cone Penetration Testing? Seismic CPT or SCPT is a method of calculating the small strain shear modulus of the soil by measuring shear wave velocity through the soil. The small strain modulus is an important quantity for determining the dynamic response of soil during earthquakes, explosive detonations, vibrations from machinery, and during wave loading for offshore structures. The wave speeds and moduli derived from seismic CPT measurements aid in the determination of soil liquefaction potential and improve the interpretation of surface seismic surveys by providing wave speed profiles as a function of depth. Seismic waves from SCPT tests have been detected at depths of up to 300 feet. How does it work? SCPT testing is performed as part of a normal CPT or CPTU test. Equipment consists of a CPT rig, push system, and: SCPT Cone: The SCPT cone is a CPT or CPTU cone that is equipped with one or more geophone sensors. These sensors measure the magnitude and arrival time of seismic shear and compression waves. Wave Generator: Seismic shear waves are generated at the soil surface in one of two ways: The simplest method is to press a steel bar onto the ground lengthwise using the weight of the CPT rig, then strike the end of the bar with a large hammer. An electronic trigger attached either to the hammer or the bar records the exact time of the strike. Another method uses an electronic wave generator attached to the CPT rig. This method increases repeatability and reduces physical strain and testing time for the field team. The CPT test must be paused briefly at the desired intervals to perform the wave generation and data collection. These pauses may be used to conduct a pore pressure dissipation test as well. Data Acquisition System: As [...]

By smadi66|December 1st, 2019|Geotechnical North Dakota, Geotechnical Oklahoma, Geotechnical Ohio, Geotechnical Oregon, Geotechnical Pennsylvania, Geotechnical North Carolina, Introductory, Soil Testing, Geotechnical New Hampshire, Geotechnical New Jersey, Geotechnical New Mexico, Geotechnical New York|0 Comments

CPT Dictionary: Soil Shear Strength

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. The in-situ shear strength of soil is difficult to measure, and many methodologies for doing so have been proposed. In general, estimating undrained shear strength--that is, the shear strength of the soil with in-situ moisture--using the CPT is accomplished via the relationship between overburden stress and cone resistance, as shown in the equation below. su = (qc – σvo)/Nk Where: su = undrained shear strength (unitless) qc = cone resistance (psi) σvo = overburden stress (psi) Nk = empirical cone factor (a unitless constant) Nk is determined in the lab, for example via triaxial compression tests. The exact value varies based on the type of reference test used, so it is important to be consistent in this regard. Most test methods return values between 10 and 30, varying with factors such as OCR (over-consolidation ratio), pore pressure, and soil plasticity. Several alternative methods may be used to estimate undrained shear strength via CPT, depending on the test conditions and available data. One such method uses pore pressure at u2 (directly behind the cone) in place of overburden stress: su = (qc – u2)/Nk The disadvantage of this method is [...]

By smadi66|November 29th, 2019|Geotechnical Ohio, CPT Dictionary, Geotechnical Pennsylvania, Geotechnical North Carolina, Soil Testing, Geotechnical New Mexico, Geotechnical New York, Geotechnical North Dakota, Geotechnical Oklahoma, Geotechnical Oregon, Geotechnical Rhode Island, Uncategorized, Geotechnical South Carolina|0 Comments

Seismic Averaging in SCPTu testing

Did you know that our CPTSND Data Acquisition program can average repeat seismic strikes? Once you have a strike on the screen, simply accept (retain) the strike and then add another strike of the same type ( A strike for example). This second strike will display below the first strike and when the second strike is accepted (retained) it will be averaged with the first strike and only the averaged strike will remain on the screen. If a third strike is added and then accepted (retained) it will be averaged with the result of the first two. (NOTE: Our software does not retain all the individual strikes- once they are averaged only the average is on file) Averaging strikes is recommended by some of the top GeoTechs in the nation!

By smadi66|November 29th, 2019|Geotechnical Tennessee, Geotechnical Ohio, Geotechnical Pennsylvania, Geotechnical North Carolina, Geotechnical North Dakota, Geotechnical Oklahoma, Geotechnical Oregon, Geotechnical Rhode Island, Geotechnical South Carolina, Geotechnical South Dakota, Uncategorized|0 Comments