During a number of recent projects our technicians have discovered very shallow post-tension (PT) cables on job sites. This is a huge issue and can be incredibly dangerous, as well as resulting in costly repairs.
Our technicians have reported finding cables up 7mm below the surface, which is usually unheard of. These cables are under massive stress and should they be hit, or cut in anyway they can explode out of buildings and through the concrete itself!
What is a post-tension cable?
Post-tension cables are used in concrete construction to add strength to thin and long slabs. Concrete has very high compressive strength but lacks in tensile strength, which is where post-tension cables and rebar come in.
The cables themselves consist of steel wires within a plastic sheath which are then tensioned after pouring in the concrete. This vastly increases the load-carrying capacity of the structure meaning that less concrete can be used, and allows for fewer beams, longer spans, and thinner slabs. It is used across a wide range of structures including apartment buildings, office buildings, and bridges.
Dangers surrounding post-tension cables
When cables are drawn tight they are under thousands of pounds of pressure. If theses cables are cut, nicked, or compromised, they can rip through the concrete and cause serious injuries and damages.
Cables are usually below a layer of rebar, however, recently our technicians have reported finding PT cables at very shallow depths. This causes a lot of issues as contractors do not realize they are laid so shallow. Luckily we are able to detect them and allow those on site to avoid them.
Scanning concrete for obstructions and hidden objects
During construction there is often the need to cut or core through the concrete slab, along with the need for anchoring for pipes or walls. It is incredibly important to avoid hitting PT cables when carrying out this work.
GeoScan are Canada’s leading experts when it comes to concrete scanning and are able to scan and identify obstructions below the surface and differentiate PT cables from other in-slab targets such as rebar or conduits. Using our Xradar™ Concrete Scanning methods, we are also able to determine the depth of objects and advise on the best course of action when carrying out work.
For more information on concrete scanning, or what we are currently finding when it comes to post-tension cables, get in touch with one of our expert technicians on (604) 436-7226.
GeoScan Subsurface Surveys is pleased to announce that we are the only provider of Xradar™ Enhanced Concrete Scanning on the West Coast.
Xradar™ is an advanced imaging capability utilizing GPR technology which allows you to map and locate objects that conventional GPR cannot. Xradar™ allows you to scan the ground for subsurface objects and is commonly used in applications across construction, archaeology, geophysics, and the military.
What is Xradar™?
The scanning process works by sending high-frequency electromagnetic waves into the ground from a transmitting antenna. These waves are reflected back as they bounce off objects, which forms an image of the subsurface.
This method can be used on a wide range of surface materials including rock, soil, ice, water, pavements, and other concrete structures. Unlike conventional GPR, Xradar™ can also distinguish between multiple layers of steel reinforcement, locate objects hidden below steel, as well as accurately measuring the size and depth of steel reinforcement.
Why choose Xradar™?
While conventional GPR is an unregulated industry, Xradar™ technicians are highly trained and have an advanced understanding and knowledge, meaning they can accurately interpret the data to form a clear picture of the subsurface.
When used for scanning concrete the accuracy and range far outshines that of any other method, while scanning errors are reduced to less than 1%, compared to the 25% typical for the industry.
Using Xradar™ saves you time, prevents injuries, and vastly reduces costly errors that can happen as the result of poor scanning.
GeoScan Subsurface Surveys and Xradar™
GeoScan is proud to be able to offer Xradar™ Enhanced Concrete Scanning Services as we continue to strive to deliver the highest level of service to our clients. As such, we are the only company on the West Coast that guarantee our concrete scans. This means that you can have full confidence in our services, allowing you to focus on your project without any costly and time-consuming errors.
Xradar™ is based in Toronto and Montreal, and GeoScan are excited to bring this industry leading service to the West Coast as the sole provider.
For more information on Xradar™ and the services we offer, get in touch with one of our expert technicians on (604) 436-7226.
GeoScan were recently hired by a leading engineering company to perform a geophysical survey of a suspected waste dump.
An area south of Victoria on Vancouver Island was suspected to have been used as an illegal dumping ground. Approximately 6,700 square meters, the area required an Electromagnetic Conductivity Survey to determine the presence of buried waste, and therefore confirm the company’s suspicions of illegal dumping.
A GeoScan technician performed an Electromagnetic Conductivity Survey of the area in order to test for areas of high conductivity and metallic disturbance.
This technique is commonly used to identify subsurface features, areas of high or low conductivity, and areas of high magnetic disturbance. The data was processed to create two differing colour-coded maps of the subsurface, showing conductivity data in MilliSiemens per Meter (mS/m) and In-Phase (magnetic) data in Parts Per Million (PPM).
The scan showed the main concentration of conductivity in the southern part of the area, confirming the presence of buried waste. The eastern area of the survey also displayed some responses, although with evidence of existing dumping, scrap metal, and other items scattered throughout the survey area on the surface, this is suspected to mainly consist of surface metal.
Although Electromagnetic Conductivity was used for this site, we could also have used a Magnetometer which draws accurate results when determining old, buried material.
For more information on our geophysical services and Electromagnetic Conductivity Surveys, get in touch with a GeoScan technician.
GeoScan are regularly called to scan sites previously scanned by other companies in order to verify the work, or to correct failed scans.
The issue with GPR (Ground Penetrating Radar) is that it is currently an unregulated industry and many companies operate with untrained technicians. This can cause major problems for those utilizing these services and can generate a lack of trust in the technology.
At GeoScan we have developed Xradar, an advanced imaging capability, utilizing GPR technology. Xradar uses radar amplitude, phase and shape to achieve maximum performance for freehand B-scan analysis.
Xradar has the ability to accurately locate objects beneath the surface that GPR cannot. In addition, all of our technicians are fully trained experts and can guarantee the results of our scans.
Recent Project: Verifying Core Location
We were recently called to a site where an engineer would not clear a hole for coring in an area that had been scanned by another company. Our GeoScan technician performed a scan using Xradar and proved the engineer's concerns were justified.
In the below images you can see the clear difference in the detection capabilities of GPR vs Xradar.
The proposed core location is indicated by the black circle. While Figure 1 appears to have detected the top rebar for the most part, it cannot see past the "shadowing" created by this layer. In Figure 2 you can see that Xradar is able to see past this shadowing and allowed our technician to mark out Top Rebar (Green), Electrical Conduits (Red), and Bottom Rebar (Blue).
Had this core gone ahead originally it would have cut through an electrical conduit resulting in costly damage and more project time to correct the error.
Fast and Accurate Scanning
The process of scanning concrete with Xradar is incredible efficient and flexible. When scanning an area to core a hole you can know within a few moments whether the location will work, or a new one needs to be considered.
A recent example of this can be seen in the below images where GeoScan were called for a second opinion following a GPR scan from another company. In Figure 3 the company were confident they had mapped out the top layer of steel and advised the client that they could not see anything below this layer of steel.
A GeoScan technician performed a scan and within just 15 minutes identified and mapped out the contents of the slab. As you can see in Figure 4 the original scan was very far off and even missed an Electrical Conduit (Red).
For more information on concrete scanning and Xradar, get in touch!
GeoScan were recently hired by a Vancouver Architecture Firm to map the bedrock at the location of a West Vancouver property build.
A local client building a house on the shore in West Vancouver noticed visible bedrock on the surface of the property.
As it is expensive to blast bedrock it is important to map the location and depth through bedrock profile mapping in order to determine the cost and extent of a potential blast.
Local building regulations for blasting bedrock state that the “maximum allowable quantities are 1.5 m times the area in square metres of the principal building and garage footprint or 600 m³, whichever is less”.
GeoScan were hired to map the bedrock of the site for the client in order to show the exact depth across various locations.
Using GPR and ERT, two methods to confirm depths, our experienced technician scanned the area and referenced locations using GPS and 3D Laser Scanning to then display the depths over the site on CAD plans.
This provided the client with an accurate and easy to understand report which could then be used to quote and plan the required blasting of the bedrock.
There are a number of options when it comes to concrete scanning and utility locating, each with their own benefits and drawbacks.
For a long time Ground Penetrating Radar (GPR) has been the pinnacle of scanning technology. It is a fast, versatile, and inexpensive solution for detecting objects beneath the surface.
The issue with GPR is that its effectiveness relies solely on the technician using it which can lead to issues, especially in an industry that is, for the most part, unregulated.
Xradar is a new method of concrete imaging that has been proven to reduce scanning errors to less than 1%, compared to the 25% typical for the scanning industry.
What is Xradar?
Xradar is a new form of scanning developed from GPR with improved accuracy and a huge range of applications. Unlike GPR this method can only be carried out by trained and authorized technicians who are qualified to deliver the service to the highest standards. This ensures that clients receive the most accurate reports and can be confident in the results.
In addition Xradar has the ability to distinguish between multiple layers of steel reinforcement, recognize conduits below reinforcement, and determine the size of the steel reinforcement. All of which GPR is unable to do!
The Problem with GPR
While ground penetrating radar itself is a fast and effective solution to scanning requirements, the problem surrounding the service is the lack of regulation. This means that a lot of GPR contractors simply do not have the skill or the understanding to properly use the method effectively.
This is a huge problem as it not only gives the industry a bad name, but can cause major issues on site, such as damaging undetected conduits when coring.
GeoScan are regularly called on site to correct the work of unregulated GPR contractors using the more accurate Xradar.
Making the Right Decision for your Business
With specially trained technicians, Xradar provides you with complete confidence when scanning, and ensures that each job is carried out in the most efficient manner, providing the most accurate results.
This is far more cost effective, saves time, and prevents avoidable injuries and costly errors that can often plague the scanning industry.
Get in touch to find out more about our services and how they can help your business!
Subsurface Utility Engineering (SUE) is a practice used to manage the risks associated with utility mapping, design, coordination, and relocation.
Every year in North America hundreds of thousands of utilities are accidentally struck during work procedures, however, with the aid of SUE this number can be reduced to practically zero.
Utilizing SUE is incredibly important within the construction industry and saves both time and money by ensuring fewer project delays and costly repairs.
What is Subsurface Utility Engineering?
Subsurface utility engineering is aimed at obtaining accurate subsurface utility data at the design stage of projects.
The process begins by outlining the scope, project schedule, and service against the associated risk. It combines field identification activities such as GPR (ground penetrating radar) and electromagnetic equipment, with survey, CADD, and design in order to identify and map existing underground utilities.
SUE is completely non-destructive and allows those carrying out construction activities to ensure that no utilities are damaged as a result of the project.
Applications of SUE
SUE engineers are there to protect underground utilities, ensure the safety of those working on site, along with the continuation of utility services for surrounding residents and businesses.
It is mainly used at the design stage of projects as part of information gathering and asset management. Prior to the commencement of construction, the objective of SUE is to collect accurate utility information within the project area in order to avoid conflict during later stages of construction.
In terms of asset management, SUE is used when there is missing or inaccurate data, and the gathered information is added to the existing database for future reference.
Standards and Quality Levels
In 2003, the American Society of Civil Engineers (ASCE) published Standard 38-02 titled Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data. This outlined various guidelines for the collection and depiction of subsurface utility information.
The four quality levels are as follows:
Quality Level “D” – Information obtained through review of utility owner records.
Quality Level “C” – Information obtained through the identification and survey of surface features. This information is used in correlation with quality level D information.
Quality Level “B” – Information obtained from the use of geophysical survey equipment that searches for utilities. The surface geophysics is interpreted, and the location of the utility is marked on the ground for subsequent survey and review by utility owners.
Quality Level “A” – Information obtained by excavating to expose the utility. Collected data includes the horizontal and vertical location of the utility to within centimetre accuracy, the elevation of existing grade over the utility, as well as the utility’s diameter and material composition.
Concrete core drilling (or concrete coring) is the process of removing a cylinder of concrete from the rest of the structure.
There are many applications across a range of fields, including plumbing, electrical, drainage, manholes, HVAC, and structural testing. Depending on the requirement a range of sizes can be drilled, and we offer the coring of holes up to 18” in diameter, which can drill up to virtually any depth.
What is concrete coring?
Concrete coring utilizes a diamond cutting drill to cut a perfect round hole in any concrete structure. The process is low-noise, dust free and non-percussive, meaning it is the most popular choice when it comes to cutting.
Holes can be drilled at any angle – whether vertical or horizontal, and a choice of electric or hydraulic rigs can be used for drilling in sensitive locations or confined spaces.
How does it work?
A concrete drilling tool is comprised of a diamond cutting end attached to a steel tube. In most case the rig is attached to the floor or surface using an anchor, bolt, or vacuum seal in order to stabilize it.
As the rig drills the cutter is cooled by water in order to reduce friction. The cutting process is completed by the removal of the slug, leaving a perfect hole with no cosmetic damage or requirement for after care.
It is always important to scan the area prior to cutting to ensure that there is in the way of the drill such as rods or conduits. Find out more about concrete scanning HERE.
When is it used?
Coring is used on floors, walls and ceilings whenever there is a requirement for a hole. There are many applications, but in general it is used for utility penetrations.
Core holes are necessary for making way for water pipes, sewer lines, phone lines and computer lines. It is also required for plumbing, electrical wiring, and heating, along with the creation of vaults and manholes.
If you are looking for concrete core drilling services, get in touch today!
Ground Penetrating Radar (GPR) is a method for scanning the ground for subsurface objects.
GPR is a non-destructive process with a variety of applications from earth sciences, archaeology, construction, to military.
The process works by sending high-frequency electromagnetic waves into the ground from a transmitting antenna. These waves are then reflected back up to form an image of the subsurface. It can be used across a wide range of materials, including rock, soil, ice, fresh water, pavements and structures.
A Ground Penetrating Radar system consists of a transmitter, a receiver, and a control unit. The transmitting antenna begins by sending electromagnetic waves into the ground, which are then reflected off underground layers and objects.
Reflections are produced whenever the wave enters a material that differs in its conduction properties from the material it left. The receiving antenna then receives the wave reflections and measures the travel time and strength. This is then converted into an accurate image of whatever is below the surface.
A number of factors can be altered depending on the requirement of the process. Changing the frequency of the wave can alter the depth and detail of the scan, therefore antenna choice is one of the most important factors in survey design.
GPR has applications in a number of fields. It can be used in Earth Sciences to study bedrock, soils and groundwater, along with water table profiling.
Most commonly it can be used in engineering applications as a form of non-destructive testing (NDT) on structures and pavements. It can be used for concrete scanning, utility locating, and oil tank locating, to name a few.
Another application lies in archaeology, with the detection and mapping of archaeological features and cemeteries. GPR also has uses in military and law enforcement, for the detection of dangerous objects such as landmines.
For more information on ground penetrating radar and how it can be used, feel free to get in touch!