Join us at Geo-Congress 2014 – Booth #105

Geo-Congress 2014, Atlanta, Booth 105 Join us at Geo-Congress 2014 in Atlanta starting Sunday, February 23rd and running through Tuesday, February 25th, 2014. We're excited to be a part of this historic gathering, the first Geo-Institute conference focused on sustainability. CPT is an important part of structural design, including sustainably focused projects. It is also a vital technology for ground water monitoring, protection and soil remediation which are essential to sustainable development. Vertek CPT is excited to be sharing the latest breakthrough CPT tools including the new S4 quick attach CPT system! We'll be planning our spring product demo schedule that is kicking off in May. So stop by booth #105 to arrange a time and place to experience these products first hand and see how Vertek CPT can help you to be successful in the CPT business. Hope to see you there!

The Importance of Proper Soil Quality

Sometimes it's hard to imagine how important designing the proper foundation support for a structure can be. The public may assume that the ground we are standing on is pretty much stable and should be able to hold whatever we build on it, without consideration of soil quality. However, there are examples throughout history of structures that were built upon soil conditions that were not suitable for their weight. Perhaps the most famous is the Leaning Tower of Pisa. With better soil quality, it may have been known today as the Tower of Pisa Unfortunately for the constructors, the Tower was built upon a patch of soil that was too soft on one side for the pressure the structure would exert as it's height climbed. The Tower actually had begun leaning during the construction process and had quite a tilt before it was even completed. Over time, builders began to realize that in order to build magnificent structures, and to have them endure over time, they had to understand the geology they were building on. They had to be able to translate an understanding of the soil quality that is not able to be seen into foundation designs that would support even the tallest skyscrapers we build today. Through lots of experimentation, science, engineering and creative solutions, we've been able to evolve our understanding of how to perform a variety of soil tests and how to link that to solid design and construction methods that will support structures as varied as highway bridges and high-rise buildings. As you explore the resources that we've provided in our CPT University, you'll learn about a variety of soil tests and the advantages of each. Tests such as Standard Penetration Tests (SPT), Cone Penetration Tests (CPT) and other forms of testing all have their [...]

Standard Penetration Test (SPT) a Basic Soil Testing Procedure

A widely used soil testing procedure is the Standard Penetration Test (SPT). This test is still used because of it's simplicity and low cost. It can provide useful information in very specific types of soil conditions, but is not as accurate as a Cone Penetration Test. Here's more information about this basic soil testing procedure. For this test, a sample tube, which is thick walled to endure the test environment is placed at the bottom of a borehole. A heavy slide hammer (140 lbs) is dropped repeatedly 30 inches onto the top of the sample tube, driving it into the soil being tested. The operation entails the operator counting the number of hammer strikes it takes to drive the sample tube 6 inches at a time. Each test drives the sample tube up to 18 inches deep. It is then extracted and if desired a sample of the soil is pulled from the tube. The borehole is drilled deeper and the test is repeated. Often soil recovery is poor and counting errors per interval may occur. The number of hammer strikes it takes for the tube to penetrate the second and third 6 inch depth is called the 'standard penetration resistance', or otherwise called the 'N-value'. The standard penetration resistance offers a gauge of the soil density of soils which are hard to pull up with simply a borehole sampling approach. You can imagine pushing a sample tube into gravel, sand or silt and struggling to recover samples that are useful for analysis. Coupling the standard penetration test with borehole drilling and sampling can be an improvement for understanding certain soil types underground. This basic soil testing procedure gives reasonably consistent results in fine-grained sands and is not as consistent in coarse sands or clays. It can be useful in [...]

Soil Electrical Conductivity

In terms of measuring soil contamination, measuring soil electrical conductivity can provide useful information for a more complete site characterization study. Measuring sub-surface soil electrical conductivity is becoming less expensive as well as faster and easier. This form of measurement has most commonly been used for measuring physical and chemical soil properties but the ability to pinpoint contaminants is improving, particularly with software designed for the job. How to Measure Soil Conductivity Measuring soil electrical conductivity is facilitated by two different types of sensors, a contact sensor and a non-contact sensor. Contact sensors work by making contact with soil to measure electrical conductivity directly. These types of instruments are most often used along the surface of a field to characterize the soil for agricultural purposes. Non-Contact Sensors Non-contact sensors, as the name implies, function without having to touch the soil directly. This method is based on the measurement of the change in mutual impedance between a pair of coils passed through the soil. Electricity is applied through the coils, which creates a magnetic field. Much like the way an induction motor operates, this magnetic field induces an electrical current in nearby materials that are magnetic. You can assess the level of current induced by measuring the impedance in the operating coils. Passing non-contact sensors down a borehole has been used effectively to establish geophysical properties such as the presence of clay (which may have highly conductive materials distributed through it) and water table levels. In cases where an area is known to have contamination, the identification of clay layers and groundwater distribution can help to estimate where 'plumes' of contamination might be contained orspread underground. In the case of a borehole test, water samples can be gathered directly from discrete depths to confirm the presence of various types of contaminants. [...]

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 [...]

Soil Quality and Soil Liquefaction

Soil quality typically refers to three characteristics of a soil; the chemical, physical and biological properties. When used as an agricultural term, soil quality is often a measure of the soils ability to produce crops over the long term. However, because the chemical and physical properties of soils are of interest to engineers as well, soil quality is often a term used to describe soil properties of interest to designers, engineers and constructors. The soil quality parameters of most interest are the chemical properties and physical properties. We have featured a closer look into some of the other chemical properties of soils in previous posts, including the ability of soils to conduct electricity, and what this can tell us about types of soil contaminants that might be present. Here, we’re going to delve more deeply into physical soil quality, and one property of certain soils that can be fascinating, but also tragically dangerous. That property is the propensity of certain soil types, under certain conditions to exhibit liquefaction. Liquefaction and Soil Quality Liquefaction, as the name implies, is the term used to describe soil that behaves like a liquid. As you can see from the image above, this can lead to catastrophic outcomes. If the people constructing this building had a better understanding of the impact of soil quality on the stability of the structure, they might have had the opportunity to mitigate the potential damage. So clearly, the susceptibility of a soil to liquefaction is an important indicator of the soil's quality. But what is soil liquefaction? Well, as we noted above, liquefaction is when soil acts like a liquid, but how can this happen? Soil liquefaction most often occurs in loose, sandy soil types where the soil itself is mostly, or completely saturated with water. When this type [...]

See the Vertek CPT Lightweight Portable CPT Push System in Action!

At Vertek CPT we love to develop innovative, yet practical CPT solutions with real ROI. There are many situations where an ultra-mobile, yet reliable CPT push system makes a lot of sense. In areas where it is difficult to get rig-based CPT equipment into place, maybe due to the terrain, soil conditions or distance from the nearest road, a CPT system that can be carried and operated by a small crew makes sense. Maximize Your Soil Testing Service Vertek's 10 Ton Portable Cone Penetrometer Test (CPT) hydraulic load frame is the lightest, smallest, most portable hydraulic CPT unit available. The hydraulic power pack and the hydraulic cylinders are independent and coupled by hydraulic quick-disconnects. The aluminum twin cylinders and power pack weigh only 195 kg (430 lbs) and 160 kg (355 lbs) respectively. Even within this lightweight form-factor, the unit still pushes up to 10 tons, meaning that you can reach the depths necessary for many types of tests. After setting 4 sturdy augers with the included drive unit and hand tools as simple as a tape measure, you are ready to mount the unit and start pushing. You can see how easy transportation, set-up, operation and tear-down are here: [/fusion_youtube]

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 [...]

Using a Compaction Test to Determine Site Safety Standards

Compaction is an engineering term used to describe the ability of a soil type to be treated with mechanical energy and compressed such that air voids are removed. With individual grains compressed to remove air voids, it becomes more difficult for the soil being compressed to 'settle' further on its own. The strength of the soil in loads other than compression can be increased because the individual particles within the soil become interlocked and friction can become a more important function of the soil behavior. Compacted soil, because air spaces between the particles are reduced has lower hydraulic conductivity (passes water less easily under a given pressure). Why do a Compaction Test? Compaction can be important when high loads such as building foundations may cause a soil to settle over time causing shifting or even collapse. It can be valuable for soil that you want to retain in place, such as along an embankment or behind a retaining wall to be compacted. The compaction process, by increasing the friction in the compacted soil helps to maintain against horizontal slippage which can either result in a landslide off from an embankment or in higher pressure behind a retaining wall, causing it to bow outwards. Because compaction lowers hydraulic conductivity, it can be useful, or even essential in the functioning of earthen dams, drainage ditches and levees. A measurement of compaction is the change in density, or weight per unit volume increase after the soil in question is compacted. That's why sometimes 'compaction' is also called 'densification'. This is actually not a correct designation as 'densification' actually includes both 'compaction' which is described above as well as 'consolidation'. Consolidation involves fluid flow out of the soil being densified, such as when you are treating clay heavy soils. Water is squeezed out from [...]

Soil Quality in Geological Engineering

Agronomists, Civil Engineers, Geological Engineers and more will often talk about 'Soil Quality'. As a result, there can be varying definitions of what 'quality' soil means. That means that there are a wide variety of tests to determine 'Soil Quality'. What Does Soil Quality Mean for You? For the Agronomist, Soil Quality refers to the capacity of soil to provide a kind of function related to growing capacity. This will take into account the soils ability to support life as in its chemical properties (does it have enough nitrogen etc.), it's biological properties (does it have the right bio-system to support the production of certain types of crops), will it retain the right amounts of water, is it's grain size suitable for tilling etc. There are many tests that will help one to evaluate the agricultural viability of soils. For the Civil and Geological Engineer some of these tests might be valuable. For instance, in making recommendations in how to reclaim a 'brown field' (a site that was formerly industrial that is now being re-developed for other purposes) it can be useful to identify the level of ability of an area to support specific types of grasses. When performing earthworks, it is not uncommon to use plantings such as trees as part of the anchor system to help to hold berms and such in place. Knowing Soil Quality in this respect can help to support a good decision with respect to the structural support that a living ecosystem can bring. Generally though, Engineering types are after more specific physical properties in order to 'do the math' on how an engineered system will interact with the soil conditions that are present. This enables engineers to either recommend changing the systems in place (such as by excavating large quantities of soil out, [...]