Are you a driller looking at adding a soil testing service to your business? If you’ve been in the drilling business for any length of time, or if you’ve been involved in drilling around sites that are being prepped for construction or development - you may have crossed paths with a Cone Penetration Test (CPT) operation. If you have been curious about this service, you probably noticed that the operating conditions of CPT are pretty comfortable. You may have also heard that the daily rates or rates charged per foot of depth for CPT are usually quite a bit better than what you can get for drilling. Adding soil testing services to your business can be a good way to diversify your workload and ensure a steady income for your business and your family. What you may not know, is that the skills you’ve acquired to drill are a good basis for entering the CPT business. What do you need to get started? A good place to start is to start comprehending the reasons why customers need a soil testing service and the basics of how this type of soil testing works. This will help you to start thinking about the needs in your area and the types of things you’ll need to learn in order to be successful in the business. Why a Soil Testing Service? When engineers are in the early stages of designing infrastructure, such as roads, bridges, or foundations for buildings, they need to know the characteristics of the ground that is going to be built on. Depending upon the type of construction, they may need to understand how soil, clay and rock are layered below the surface. This can help them to decide what the construction process will look like. For instance, will blasting or [...]
If you are considering entering the CPT business from, let’s say, operating a well-drilling business, you’ll want to prepare yourself for a few adjustments. Depending upon the type of business you are used to running or being a part of, you’ll find that the customer interactions may be different. CPT testing is all about gathering data from field tests and quickly turning that into useful information for the site owner, an engineer, construction company, government agency etc. This blog is an introduction to the basics of CPT reporting. We’ll start with what we’re trying to measure, then we’ll discuss how a CPT system, and in particular the probe, gathers specific types of useful data. Then we’ll, look at some ways that this data is interpreted to make useful information for your customer to make decisions. In real life, you’ll want to use a software application that quickly and efficiently does this interpretation for you. However, Vertek CPT believes in training it’s customer partners from the ground up (so to speak) so that you are comfortable and confident in every conversation you’ll have. What are we trying to measure? CPT is the quickest and most cost-effective way to map out what the soil conditions are under your feet. If you imagine being able to look at the ground ‘from the side’, you’d see layers something like this: For people responsible for building highways through hilly territory, or building a heavy structure, it’s important to know what’s underground before they begin planning. This is where CPT comes in. CPT lets you draw a picture of what’s underground for folks who need it. How Does a CPT Probe Gather Useful Types of Data? So let’s start with the Cone, the ‘C’ in CPT. If you look at the picture below, you can imagine [...]
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 [...]
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 [...]
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 [...]
Ohio Unversity Accelerated Pavement Tester in Action! In 1997 Vertek delivered our first of many Accelerated Transportation Loading Systems (ATLaS). Ohio University published this video, dated in 2012 of the pavement load tester in use at their Accelerated Pavement Load Facility. Common pavement tests include: Pavement coating lifetime analysis Experimental pavement fatigue estimation Pavement rutting Impact of temperature cycling on pavement Effects of wheel wander on pavement lifespan [/fusion_youtube] Though our designs have evolved since 1997 to better handle environmental and energy useage factors, many components of the above are still present on our current deliveries of pavement and bridge deck testers. These testers are designed to deliver actionable data regarding the lifespan and limits of road surfaces and pavement composition in shortened timespans. While this website is primary dedicated to our CPT business, Vertek's wealth of geotechnical manufacturing experience has led to additional focus on structural integrity fields such as load testing. See our ATLaS pavement and bridge load testing page for more information or to inquire.
If you're familiar with the CPT University then you may have had the chance to see our article: Why Are There So Many Kinds of CPT Rigs? As you may have read, there are many different rigs available; but depending upon the types of surface conditions or the terrain, one option may be more suitable for your project over another. Read on to take a deeper dive into a few different examples of CPT rigs, uses and applications. S4 CPT Push System The S4 is a robust and affordable push system that can be attached to many types of heavy equipment including ski steers, trailers, backhoes, and more. The S4 is revolutionary in many respects, for instance it provides 20 tons of CPT push capacity in a compact and affordable package. This agile, lightweight rig is only available from Vertek CPT and is one of the most inexpensive alternatives to the traditional rig. The system is equipped with full-systtem hydraulics giving you full operating control, as well as the ability to drive 2 Motorized Anchor Heads and all of the CPT system features you need to eliminate the need for external cylinders. There is no alternative to the S4 Push System that lets you enter the CPT business with confidence that you can prove out your business model before going 'all in'. CPT Track Rigs With fully equipped features and capabilities, CPT Track Rigs are available in light, medium and heavy configurations. These CPT rigs are designed to meet rigorous requirements and the demanding range of foundation work you are likely to encounter as your business grows. For certain geographical areas soft soils, boggy areas and changing environments demand a track rig. This means that you can immediately differentiate your services from the competition. CPT Track Rigs are super-pro. Track [...]
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!
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 [...]
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, [...]