CMD Civil Case Studies
Case Study 1: Ground Penetrating Radar (GPR)
GPR scanning to locate floor beams using the Mala CX11 GPR
A local design company engaged CMD Civil to scan a floor slab of an existing home in order to locate any structural beams. The owners were planning to add a second floor to the home and the designers needed to see what structural support the home had before resorting to design changes or destructive testing.
The home was broken down into cross sections running from north to south, east to west starting from the eastern corner of the house. The first scans were carried out east to west in 500mm increments parallel to the front of the home to as far back as was required.
The same steps were carried out north to south in 500mm increments through the home, only being diverted where permanent fixtures were located.
After multiple pass scans and onsite analysis of the data it became clear no structural beams were present under the slab.
This scan provided the designers with the information they required allowing them to design the second floor structure based on the fact there were no structural beams present.
Using the Ground penetrating radar eliminated the need for destructive testing to be undertaken inside the home which was of much relief to the family living there.
Case Study 2: Ground Penetrating Radar (GPR)
Mapping of mesh depth over 64 square meter slab using the Mala CX11 GPR
A Victorian building contractor along with the local council engaged CMD Civil to map the concrete cover over the mesh after the sub-contractors brought in to pour the slab knocked down a lot of the reinforcing spacers potentially compromising the suitability of the slab for its intended purpose.
The building contractor and the CMD technician agreed that spacing the scans in 2 meter increments would be suitable in order to map the slab effectively.
Once the entire slab had been mapped there were three individual areas that were detected that were below or above the ideal depth.
These areas were then scanned again to accurately gauge the extent of the area that was defective.
It was also a requirement that the key joints be scanned to determine how level they were sitting and that they weren’t set on to much of an angle, which in turn could compromise their effectiveness on the structure. All of the key joints were successfully located and the angles they were sitting at clearly marked on the slab. All of the key joints scanned were sitting at acceptable angles parallel to the surface.
The data was then collected and presented as a scale C.A.D. drawing, clearly indicating the three areas of concern and approximate depths of the mesh.
The building contractor and Council were then able to review the information presented and then make a decision on what course of action to take.
Case Study 3: Ultrasonic Pulse Echo Imaging
Mapping of potential voiding and honeycombing within a concrete structure using the Mira Ultrasonic pulse echo imaging system
A 550mm thick concrete slab was poured when it was noticed there was water flowing in underneath whilst the concrete was curing, this resulted in water penetrating through the slab slowly compromising the quality of the concrete's final finish.
The slab was approximately 28 square meters in size in the base of what was to be a tank. We used an Ultrasonic pulse echo imaging system to map any potential voids or honeycombing that may have occurred within the concrete or around any of the steel reinforcing during the curing process. This testing was essential before any further construction on the tank could proceed and was the only accurate way to gauge the condition of the concrete before resorting to destructive testing.
The ultrasonic pulse echo imaging system is capable of creating cross-sectional 2D scans and 3D images of the concrete elements in less than 4 seconds after data collection. This allowed for any areas of potential concern to be examined more accurately helping to determine the full extent of any voiding or honeycombing.
As a result it was discovered there was a high level of moisture within the top two hundred millimetres of the slab and no inconsistencies in the concrete that surrounded the reinforcing.
This data was then presented report in a 3D format clearly displaying any areas that may be of concern to the designers. From the data collected they were then able to make a decision on what course of action to take.
Case Study 4: Ground Penetrating Radar (GPR)
Surveying to locate possible utilities using the Seeker (SPR) cart mounted (GPR) system with a 500 MHZ antenna
A 900 square meter section of a temporary car park verging on the edge of local tram lines needed to be surveyed in order for fence to be constructed with multiple bracing poles being inserted 800mm into the ground.
The land was essentially a waste land which the public were taking advantage of and using as a car park for the local train station, problem being there was no fence line or barriers separating parked vehicles from the tram line running past and it was causing some issues for the trams when vehicles would park too close to the lines.
The section of land was is one of the older areas of town so not all services could be confirmed by the 1100 Dial before you dig service. The surface was covered with gravel and overgrown trees and grass as well as being extremely rough.
The area also consisted of power poles, communication boxes and storm water drains running directly in and around the path of the intended location of the proposed fence.
The Cart mounted GPR was ideal for this terrain, allowing it to travel over the gravel and long grass without disrupting the data it was collecting. It produced very high resolution data of the subsurface elements; we had the depth set to around 1.5 meters although it can comfortably scan down to depths of 4.8 meters in good conditions.
This scanning coinciding with an onsite walk over to establish where the power, communication and water services were located and where possible lifting any lids on services to trace the direction they were running.
Being such an old site it produced a variety of inclusions within the subsurface such as large pieces of steel; segments of old rail tracks and old disused pipes. Using the GPR we were able to trace the length and depth of these various inclusions and clearly indicate on the ground and plans exactly where they lay.
All services and other inclusions were clearly marked on the ground, photos taken and because no proper plans were available of the area a C.A.D. representation was produced outlining all areas where services or inclusions in the ground would possibly affect the bracing poles being inserted into the ground safely.
This provided the necessary information required about the subsurface elements before any construction could commence, helping to avoid digging through vital services which could cause injury and cost time and money.
