Why Would You Need a Track CPT Rig?

Vertek CPT wants to ensure that you have the right equipment to grow your business. As you are going through the CPT rig purchase process, we’ll have extensive conversations to ensure that we are both on the same page when it comes to where you will be testing, what types of tests you can most easily sell, and which rig or rigs will help you to make the most money. Track Rig Features As you look around our site, you’ll see that some rigs are built on tracks, as opposed to truck beds with wheels. As per with construction equipment, you might expect the tracked equipment to be larger, with CPT rigs the tracked units tend to be smaller. This is because tracked rig CPT platforms are designed to not only traverse and work in difficult terrains, but also to be highly maneuverable around obstacles such as trees, rocks and gulleys. Remember, CPT testing may be specified by your customer for pre-construction activities, meaning that it takes place on a site with little preparation. Having a highly maneuverable platform with low ground pressure can make the difference between you being able to win certain jobs and not. Track rigs are usually designed in order to distribute the weight of the rig over more square inches of contact area. This helps to minimize damage to sensitive areas as well as help the rig not get stuck in less than optimum ground conditions. The overall rig footprints are designed so that the units can be effectively trucked to sites within your service area. Track rigs are designed for deep pushes in tough geologies and the Vertek CPT tracked rigs push from about 10 tons up to 25 tons. With the right combination of weight, ease of maneuverability and set-up features, a tracked [...]

Measuring the Moisture Content of Soil Using CPT

Measuring 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. Because establishing subsurface moisture content can be safety-critical in certain cases, Cone Penetration Testing methodologies have evolved to provide relative soil moisture content data. It is now possible to measure soil moisture more directly at the cone head vs. inferring what the moisture might be through interpreted sounding data. One method of measuring the presence of water is with a ‘piezocone’. This is a CPT cone that is fitted with a device that measures pore pressure. As the cone penetrates into saturated soils, hydraulic (water) pressure is exerted on the instrumented cone. By watching this pressure increase and decrease as the cone is driven deeper into the ground, it is possible to measure the presence of moisture at depth. This type of approach is better suited to soil conditions in which it is expected for the soil to be fairly wet to saturated conditions. Another method of establishing the extent of the presence of water is by using electrical sensors such as a dielectric probe, which measures soil electrical conductivity. This can be a useful practice and can be helpful in soils with less [...]

LED Fluorescence Detectors and Fuel Fluorescence Detection (FFD)

Hydrocarbons: including gasoline, kerosene, diesel fuel, jet fuel, lubricating and hydraulic oils, and tars and asphalts contain Polycyclic Aromatic Hydrocarbons (PAH’s). Polycyclic Aromatic Hydrocarbons (PAH’s) distributed in soils and groundwater fluoresce when irradiated by ultraviolet light. Because different types of PAHs fluoresce at different wavelengths, each has its own fluorescence signature. Using an instrument that measures the intensity and wavelength of the fluoresced hydrocarbon enables the assessment of the hydrocarbons present. This makes UV Fluorescence a useful technology to use in characterizing surface, subsurface and groundwater hydrocarbon contamination. We call this Fuel Fluorescence Detection (FFD). What's the right fluorescence detector for you? Using handheld UV lights enables site technicians to establish the nature and distribution of contamination above ground. For surface spills such as what gathers along a shoreline or for surface based operations such as above ground tanks and pipes, this can be a useful place to start. For underground storage tanks a useful way to begin site characterization is with a subsurface probe. Engineers trying to establish the limits of the ‘plume’ or the depth of the contaminant as it travels underground. Plumes will extend outward, downward and upward depending upon factors such as the flow of groundwater and the confining layers of clay and rock. Leveraging the ability to generate and measure fluorescence underground requires a step up in technology. In the case of CPT, a UV light source is placed in the cone itself. Fiber-optic cables transmit the resulting fluorescence to the surface where the intensity and wavelength can be measured. Because of the efficiency of CPT, large and complex sites can be characterized quickly and efficiently. The data logs are available immediately to influence critical decision-making which can help to manage costs in the long term. For instance monitoring wells may need to be installed [...]

Ensuring That Your CPT Data is Correctly Reported and Interpreted

It 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. In CPT (Cone Penetration Testing), when the tip of the cone is being advanced, there is pressure exerted on the tip itself. This pressure is created from the resistance to downward force by whatever soil is resisting on the cone tip. However, this pressure is not simply exerted from the ground immediately in front of the tip. Rather, the cone forces the ground immediately in front of it to compress. This compression forces the ground in front of it to 'fail' that is, the soil cohesion is not sufficient to resist the tip load, and the soil compresses further down or moves out of the way down, sideways or a little bit away from the cone itself, upwards. Because of this movement and compression, the pressure exerted back on the cone tip is generated from a large area of soil below, around and a bit behind the cone tip itself. This means depending on soil stratification that the instruments in the tip sense soil resistance from around 5 or more cone diameters ahead and around the tip of the cone. Using a cone of 1.5 inches in diameter means that you are actually taking an average cone resistance measurement. This is sometimes called a 'tip influence zone'. If you are pushing through a sub-surface feature, such as a landslide slip face or a layer of softer clay that is a foot or less, it is quite possible to miss this feature entirely. In engineering speak, you might read something like 'exercise caution [...]

CPT Case Study: GEI Consultants

30 years of Cone Penetration Testing with GEI We're proud of the relationship we have with our long time customers. We succeed together. One of these groups is GEI Consultants, which has been delivering engineering services around the globe since 1970. Sean Brady, Senior Instrumentation Specialist with GEI, provided CPT University with background on their operation as it pertains to their CPT efforts. Briefly describe GEI’s engineering focus. What do you do for whom? GEI is a medium size engineering firm with around 700 employees in the United States. Our business line within GEI is Geo-technical, non-destructive testing, and geophysics. Our engineering’s have designed over 75% of downtown Chicago’s foundations and most of the tallest buildings in the world. We often are part of the design team when difficult and challenging soils are encountered. We perform CPT’s on earthen dams/embankments, river sediment depths, USCOE projects from Ft. Peck Montana to New York, RR alignments, bridge embankments, and Power plants. A little of everything you can imagine from Water, RR bridges, Landfills, stability of tail basins for the mines. We also oversee other companies performing CPT. We just worked in Asantana, Kazahkstan overseeing a new energy exposition 2016 project for both SPT’s and CPT. Also have overseen CPT testing in Doha, Qatar. When did CPT first become of interest and why? We have over 30 years of CPT testing experience. In the late 80’s we purchased a 30T CPT truck and traveled around the US performing CPT on challenging geo-technical projects. In the mid-90’s we sold our truck and started to perform CPT testing behind drill rigs. At the time we had a fleet of 18 drill rigs from track mounted, ATV, truck mounted, Barge mounted, etc. We get involved with delicate soils all the time. In some cases even when [...]

Cone Penetrometer Testing via Speed Lock Rods

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. Increase Speed, Reduce Operator Fatigue Our dual-lead thread provides fast coupling; 2.5 turns to couple or uncouple compared with 5-7 turns for competitor’s rods improving worksite productivity. Flexibility and Adaptability to Variety of Cones Speed Lock Rods are available in standard 1.44” and 1.75” diameters. Custom sizes include 2”, 2.25” and 2.5”. Vertek also manufactures custom adapters to permit use of our advanced thread design with your current inventory of CPT equipment. Make the most of your CPT rig and cone penetrometer testing equipment with Vertek Speed Lock Rods!

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 [...]

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, [...]

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 [...]

Cone Penetration Testing Glossary of Terms

This brief glossary contains some of the most frequently used terms related to CPT/CPTU. These are presented in alphabetical order. CPT: Cone Prenetration Test or the act of Cone Penetration Testing. CPTU: Cone Penetration Test with pore water pressure measurement - a piezocone test. Cone: The part of the Cone penetrometer on which the end bearing is developed. Cone penetrometer: The assembly containing the cone, friction sleeve, any other sensors and measuring systems, as well as the connections to the push rods. Cone resistance: The total force acting on the cone, divided by the projected area of the cone. Corrected cone resistance: The cone resistance corrected for pore water pressure effects. Corrected sleeve friction: The sleeve friction corrected for pore water pressure effects on the ends of the friction sleeve. Data acquisition system: The system used to measure and record the measurements made by the cone penetrometer. Dissipation test: A test when the decay of the pore water pressure is monitored during a pause in penetration. Filter element: The porous element inserted into the cone penetrometer to allow transmission of the pore water pressure to the pore pressure sensor, while maintaining the correct profile of the cone penetrometer. Friction ratio: The ratio, expressed as a percentage, of the sleeve friction, to the cone resistance, both measured at the same depth. Friction reducer: A local enlargement on the push-rod surface, placed at a distance above the cone penetrometer, and provided to reduce the friction on the push rods. Friction sleeve: The section of the cone penetrometer upon which the sleeve friction is measured. Normalized cone resistance: The cone resistance expressed in a non dimensional form and taking account of stress changes in situ. Net cone resistance: The corrected cone resistance minus the vertical total stress. Net pore pressure: The meausured pore [...]