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Laser Profiling Case Study

Sun, 29 Sep 2024 12:39:05 GMT

Laser Profiling Case Study 2024

Laser Profiling Case Study

Written by Joseph Marland-Brown of CTS Ltd

In February 2024 testing and analysis has been conducted on a laser profiling system to ascertain its pros and cons for measuring the inside surface of pipes.

The hardware was a single class 2 red laser with a conical lens fitted, powered by battery and approximately 20mm diameter by 75mm long, the laser module is fitted to a rod which in turn is mounted to a camera housing on the front of a CCTV crawler system, the rod is made of small sections which screw together to extend the laser module at different distances away from the camera. The laser and rods could be retro fitted to any Crawler system.

The laser module is made of metal and glass and could be damaged if dropped or scraped along with the inside of a pipe, the laser modules are expensive and not readily available in the industry from suppliers, in the UK there is one supplier and the rest being in Europe,

The technology of lasers dates to 1900s Max Planck Kicks it All off, followed by Einstein’s Concept and Theory of Stimulated Light Emission, the Rise of MASER (Microwave Amplification of Stimulated Emission of Radiation) in 1954, then led to Gordon Gould in 1957 Coining the phrase of Laser, this led to mainstream innovations using this technology to now,

How does a laser distance meter work?

In a nutshell, laser measurement tools are based on the principle of reflection of a laser beam. To measure a distance, the device emits a pulse of laser in the direction of an object, for example a wall. The time necessary for the laser beam to get to the object and go back determines the measurement of the distance. In consideration of the speed of light, distances can be defined precisely with this kind of laser. Laser distance meters can also accumulate independently to calculate surfaces and volumes.

A Laser Profiling system for pipes was made approx. 15 years ago in New Zealand, Software has also been designed to read the laser data to form a report for others to gain an understanding of the inside measurements and ovality of pipes.

At this stage we must understand how this system works, the first very important note worthy feature of the laser profiling system is that it does not measure, it emits a red ring on the inside of the pipe by shooting the laser light at the conical lens which in return reflects the light 360 degrees to create a single red line on the nearest surface to the lens, the light ring is thin and measures 2mm from its outside edges. it will take the form of any shape.

Setting up the system is reasonably straight forward to trained professionals but can be confusing to others, once the equipment is put together the crawler has to be placed into the pipe, this is the most likely time damage will occur, with the rod sticking out up to 400mm and with the length and weight of crawler deployment with out man entry is difficult, the standard size of a manhole for a 400mm pipe is a 580mm internal square shaft, so the system must be lowered vertically and then swivelled upwards to set the crawler horizonal whilst attempting to guide the rod into the pipe, man entry and assembling in the manhole would prevent accidental damage to the laser module.

Once set and in place the crawler must be driven along the pipe whilst recording CCTV for general condition, the video will see the rod and laser module which blocks part of the view, a condition survey can still be gained. Once the crawler reaches the end of the survey length, the operator must switch of all the lights on the crawler, it is recommended that if the pipe has an open end a cover is put over the pipe to reduce the natural light, the crawler must then be reversed out of the pipe until it reaches its staring position, again a cover would help at the staring point to reduce the natural light, whilst this operation is going on the CCTV camera is recording video, basically its seeing a black background and a red light ring. Its is also recommend that any clever settings to enhance the imagery are all switched off.

As you can imagine reversing a crawler in the dark over long distances i.e. 50 meters and more is an uncontrolled process, the crawlers are generally steerable but without any light steering becomes in affective and if chanced could tip the crawler over, there are some guides on the software screen which indicate the level of the crawler but are not that accurate and really only used as a rough guide, a cradle can be fitted to the crawler to prevent tipping, that said in a 445mm pipe it’s not too difficult to reverse even in the dark, its when larger pipe diameters are attempted that the process becomes more cumbersome.

It is also worth noting that any water in the pipe will affect the laser light as laser will only reflect off the water and not give a fully formed ring, the video image also captures the rod so there is a break in the laser ring when viewing the video film.

To create a perfectly formed ring laser in a pipe the crawler must be aligned to the pipe both horizontally and vertically with the laser module central, as the crawler moves position the light ring moves with the orientation of the crawler, this will later lead to inaccurate analysis of the light ring survey. The accuracy is said to be 3% of the diameter of the pipe, so in a 445mm pipe this would be in perfect conditions, 3% of 445mm is 3 x 445mm over a 100 = 13.35mm.

After the survey is completed the software can then analysis the video and light ring created in the video, this is where the measurements take place, the first process is to Calibrate the laser using the video and a ruler, then the measurements can be put into the software, the software can then work out from the calibrated measurement the diameter of the light ring emitted onto the pipe interior surface and also gives a picture of the video from the survey, the video will be imported into a X,Y,Z environment commonly used in measuring software, from the still images measurements can be taken, the software will also analyse the red ring and draw around it, putting multiple rings together can then create a 3d cad model,

because the laser profiler hardware and crawler system do not have built in IMUs the 3d model cannot be relied on for longitudinal differences in the pipe or any bends however slight.

Summary,

Laser profiling is a good way of obtaining measurements of the inside of pipes, the users must take as much care in calibrating to give the best results, the uncontrolled process is a concern, whether the data and report are sufficient for design purposes is solely at the designer’s risk and could have expensive repercussions in a manufacturing process for pipe rehabilitation.

Next steps…

After this testing and analysis other ways have been considered to provide internal measurements of pipes, Laser scanning and Laser profiling are the best methods, with: Laser Scanning taking precedence over profiling as Laser scanning measures in real time by time of flight and return of the laser from a solid surface,

Laser profiling can be improved on, Ive taken into account the hardware, software set up and usage of the current system, The first thing to overcome is carrying out a survey in a more controlled manner, this can be achieved by using Green class 1 lasers, also the video resolution of CCTV camera on Crawler system is analogue with a video resolution of 720 x 480 with a small field of view. This can be increased to 1920 x 1080. Field of View Horizontal (In Degrees) of 92 and a Field of View Vertical (In Degrees) of 61. This allows for larger pipe diameters to be achieved. The resolution is also greatly increased giving a much higher pixel count which leads to more accurate measuring. Example Below (Note: Fisheye lenses will distort the image)

· 720 x 480 = 345,600 pixels no HD,

· 1920 x 1080 = 2,073,600 pixels HD

Having a controlled environment with a much higher resolution camera gives the Designer clearer detailed imagery, additional low light can be added to enhance the condition survey and not affect the laser in any way, the movement of the crawler can be controlled as you can see where you are in the pipe, greater diameters can now be achieved, a single pass can be carried out while the laser ring is visible in the lighted conditions, and overall the process becomes more efficient with controlled results.

From the video software’s can be used to extract out imagery, these images can then be imported into a CAD program, after scaling and aligning data can be extracted from the image,

The benefits are you can see the picture of the inside of the pipe with the light ring, inspect if theirs encrustation, water or any other foreign objects, that will lead to inaccurate measurements, create circles to overlay on the images and draw around the light ring when its deformed, this process is not automatic, the cad operator has to pay particular attention to the process and thus learning more in detail about the condition and size of the pipe.

The rings created can be made into a solid 3d model, and other solids can be fitted inside to see if they fit, we must be careful of heave, sagging, crushing and bends in the pipe, (Note: Laser Scanning the pipe will remove all these essential criteria’s)

We are now evaluating a new system which we have built and will report on the accuracies when final testing is completed, the initial testing gave a 0.5mm reading between two light rings in a 445mm ribbed land drainpipe tested at our Workshop in a controlled and measured environment. Further testing returned results of tolerance 0.61mm, tolerance 1.86mm & tolerance 2.18mm, we believe a safe number to work from would be 3mm accuracy which in turn reduces the 3mm percentage rate down to 0.5%.

Joseph Marland-Brown

(Contracts Manager) 07920429070, Joseph@ctsltd.info , www.ctsltd.info

CTS are now ready to supply this service.

CTS Rescue Training

Sun, 14 Jan 2024 10:35:47 GMT

CTS Rescue Training

Safety has always been embedded in our thoughts whenever we think about CTS, we think (CAUTION - THINK - SAFETY).

5 of our operatives have successfully completed Rescue and High Risk Training for Confined Spaces, the team attended the training together, in which we took on roles as the rescuers and top men so each of us had the opportunity to train in all tasks.

After our training we all contributed with suggestions on setting up our rescue van, we have chosen the appropriate confined space rescue ppe for the typical environments that we work in.

Our future plans include further training in real life environments and putting to use our ppe so we can do our best to ensure the safety of our team members and our clients.

Jack, our 3D Cad Design Technician, has been working with Joseph to recreate a 3D model storyboard of carrying out a survey, followed by a rescue operation.

Below we have created a few images of what a confined space rescue would look like in the environments that we work in along with the storyboard, this is to help others visualise the difficulties we would have to overcome when the alarm is raised.

ACTS (Alternative Crawler Tunnel System)

Fri, 13 Oct 2023 05:55:09 GMT

ACTS (Alternative Crawler Tunnel System)

CTS are always looking for other ways to surveys tunnels and realising the industry standard crawlers have their current limitations we spent days that turns into weeks researching alternative ideas.

This process sometimes develops into leads that are worth further investigation, although precious time is always on the agender.

Deciding once something of interest is discovered takes a lot of consideration, however our experience and carful thought and discussions normally turns up trumps and allows us to invest in new ideas, hardware and learning to put all this to the test.

The ATV we researched began with initial conversations with the manufacturers who helped us refine their product to best suite our needs and ideas, of course this soon became a can of worms but with many conversations, meetings, testing we where able to work out a way that seemed worth investing our time and money into a full-blown test.

The atv is more than capable of driving along a tunnel, just small enough to get down most manholes, and more than powerful enough to allow us to load it up with additional hardware.

This thing needed a name, so we have christened it ACTS (Alternative Crawler Tunnel System)

Now the hard work began, first we needed to test the distances we could reach using radio frequency, easy, but when you are considering over 1 kilometre finding an open space that is safe to test is harder than we thought, we decided to start shorter and soon found the limitation in open air conditions in an urban canyon was 430m, not bad to begin with. However not far enough, back to the drawing board and research, we soon found long distance RF was an option, designed for flight this posed additional difficulties in installing the receiver into ACTS, and configuring the program to make the vehicle move without failure, other issues we discovered was the full metal body of ACTS interfering with the signals, perseverance paid off and we soon moved things around. Upgraded the receiver and transmitter hardware, gave it some more power, upped the wattage to 2kw and we soon achieved over 1 kilo meter on ground in open environment, namely a runway.

Driver training was next, alright going forward but a lot harder in reverse, especially when out of sight and knowing we would lose sight in live testing in a tunnel it was imperative to get this right, worse case scenario was tipping everything over and damaging very expensive hardware. A slow approach was needed for this, and we soon got to grips with tuning the vehicle for the best speed and response within a tunnel.

Time to start adding survey parts, we took our knowledge and testing from a previous raft build and quickly adapted things to fit, that was solely lighting & cameras at this stage. We needed to get a laser scanner on board, again thinking of how we done this before helped and confidence grew that we could achieve this. Having the ability to send a vehicle a long way along a tunnel without having to use man entry in the right conditions for the vehicle is the first rule of Confined spaces, designing out the risk, When I say the right conditions, we must be careful, this cannot be sent into explosive areas, water will also have effects, silt again can cause havoc. However, there are tunnels where it can be used and with the correct approach, understanding and carful thoughtful planning a lot can be achieved. The ACTS is ok with some water and silt and as time goes by, we will learn what the limitations are.

Time for live testing, lets keep this short, it worked in a 2.5 meter diameter tunnel with 200mm of water in the invert and some silts banks along the way, the first test reached 400m, the way we done this was using a FPV headset linked to a camera on board which was only looking forward, so reversing out was cumbersome until some length had been covered and driving became smoother.

A big Sy of relief at this stage, but as always thinking of improvements and longer distances, next was 600m and that was round a huge bend, all this with Radio Frequency, how far could it go, we will discover that later, in testing we did have a track which was thrown off its wheels, not good and had to pull the ACTS out of the tunnel, in a way I’m glad that happened as we now know it could be retrieved from a long distance, their was very minimal damage to the hardware, and was soon fixed.

I forgot to mention ACTS was always tethered to a rope in the event of a breakdown, our Porto reel is more than strong enough to pull it back.

We discussed what went wrong, inspected the video footage, and looked at the hardware for visible signs of wear that caused this, after a final analysis we had concluded the tracks and wheels needed a redesign, this was already going on in the background, the atv went back into the supplier workshop and was immediately upgraded.

Right from the start of all this there was always an intention of ours not to use RF, we always thought this would be hazardous and trying to find research by others on this is almost non-existent. Our intention was to take RF and covert the signal and send it along a fibre optic cable, we already had a tried and tested 1200m fibre cable on a drum which we custom built and fitted a fibre optic slip ring too that we used to view the cameras on the raft system, another can of worms, always good coming up with the ideas but making it happen and hoping it will work can be wishful thinking, time and budget plays on you mind.

Research was always going on for this, and two companies were chosen to discuss this with, both offered their expertise, nothing was certain, a purchase on hardware was made, loads to consider,

6 weeks later they arrived, fitting commenced and then right onto testing, more to learn and initial testing was positive followed by huge disappointment, perseverance was back again and after configuring the transmitter and receiver we got it work, our initial aspirations had now been realised and the mind was full of what next. (We will come back to that later in another blog)

Back to the tunnel to test this, it worked just as expected but now we had eradicated the real possibility of losing the RF signal, 800 meters was quickly achieved a new record for us with tracked vehicle.

Overall, the R&D for all this has been a gratifying learning curve and we are all very proud of the team efforts to make all this happen. We have been refining the solution for more regular use by considering weight, pulling forces and how we can overcome having to use a rope and a fibre cable at the same time. Extremely difficult when launching from a 30-meter-deep shaft. Finding the right balance of fibre cable that is strong enough to pull the ACTS out of the tunnel and light enough to consider extending the system over 1200 meters is our main goal. Samples were sent for, and we have found the right cable with a pulling force over 1000n, next we need to get it fitted to a professionally made electronic cable drum and found a supplier to help us with this.

In time we will fine tune the hardware and system to push the boundaries of long-distance tunnel surveys for the future. We have also purchased a 4-wheel drive vehicle that we are currently testing, a 4K pan tilt, rotate, and Zoom camera with amazing night vision, and few other ideas.

We are very Proud of our Achievements in doing all this and will continue to Innovate.

Kew Gardens

Thu, 12 Oct 2023 10:56:53 GMT

Kew Gardens Water Mains

CTS were contracted in at Kew Gardens to survey to entire extents of their site. The survey was to trace all existing water utilities and supply the client with an updated water map of the gardens.

Working within this live environment, the CTS staff were at one with the public, to keep them safe we used a trolley provided by Kew to transport our equipment over their vast site. Also, CTS supplied their surveyors with low profile Personal Protective Equipment to blend in with the Gardens.

We also provided a full plant enquiry and stat pack to help the Kew management team understand the full extent of the different pipes and cables that are under the ground in their site.

Our surveyors worked on site, connecting to existing points, such as fountains, taps, water valves etc and using our SPX Radio detection RD8000 PXL and X-10 Transmitter they traced the lines of the metal water mains.

We collected the location of the water, using our S7 Robotic Station, all to OS nation Grid.

· 519 water assets were found and collected.

· 12099 feature points with X Y & Z were collected.

· In excess of 7 kilometers of pipework was located.

This data was taken back to the office for the data to be collated into one full map, displaying the location and depths of the water mains at Kew Gardens.

Park Royal/ Acton mark up.

Thu, 12 Oct 2023 10:50:32 GMT

Park Royal/ Acton mark up.

Durkins and Sons are one of our oldest clients. They contracted us in to survey and markup the utilities along their route for installing new Electric cables in Park Royal/ Acton area. This is an ongoing job for CTS requiring site revisits to mark up further as and when the client requires.

All pipes and cables are traced on site by CTS, and locations are marked in spray paint with depths, sizes, materials, and configurations of the services. All lids in the vicinity are lifted and any pipes which affect the digging route are marked out. The GPR trolley is pushed across the survey area to detect any hyperboles that could indicate an underground pipe, tunnel, or cable.

At the end of each shift, the surveyors complete a CTS utility awareness form, listing which utilities have been found, and do a site walk through with the client to discuss the survey and highlight our findings. The focus is to ensure safe digging for our client.

CTS Raft Build and Surveys (Nos Sewers, 12 Kilometres)

Sat, 07 Oct 2023 04:48:12 GMT

CTS Raft Build and Surveys

CTS were awarded by their client J Murphy and Sons a project to inspect and record the internal surface of the NOS Sewer system in East London, The Nos sewers consist of mainly of 4 barrels which are 2.6m diameter, in places they pass under roads and bridges.

The sewers span from wick lane to Beckton treatment works over 7 Kilometres, where the sewers pass under the bridges and roads, they spilt into 5 and 8 barrels, the flow is constant and generally the barrel is 50% full of effluent water.

Access into the sewer’s barrels are from Different kinds of manholes, some square, some round, and others as a rectangle construction where dams boards can be inserted.

With all this in mind the first stage of the surveys where to carry out Recces on the manholes to understand the launch positions, access sizes and general conditions of the entry and the surrounding area.

Whilst the recce information started to be collected, information was sent to the CTS workshop where the raft was in the process of being set up and later modified to allow for deployment.

The focus of the Raft build was stability & strength, the raft was built from a metal construction with two pontoons, and metal plate was used to straddle the pontoons to allow for the camera equipment to be mounted, wire rope was used for the attachment from the pulling rope to the raft.

CTS where also investigating the camera set up for the surveys, after testing 4 HD wide lens cameras where used, the cameras where mounted to the raft, forward, to both sides and one mounted looking upwards to capture the crown, a custom box was made to house all the electronics.

The raft cabling for live vision was established early on in this task, CTS modified a cable drum and housed 550 meters of fibre optic cable which was passed though a fibre optic slip ring, another custom box was made to house all the electronics for receiving the video footage from all of the cameras, using software the system was able to see all four cameras at once and switch to full screen and view individually, the receiver unit was installed in the CCTV van along with a HD monitor.

Pulling the raft through the barrels also posed a challenge, a Custom Porto reel on tracks was used for this part of the task, an encoder was built into the Porto reel to allow for the meterage count as the raft travelled through the tunnel. The focus for the potro reel was keeping hands of ropes and allowing the Potro reel to take the strain out of the movement of the raft.

The surveys commenced, after the first 5 or 6 deployments adjustments were made to the operation to achieve a smooth-running process, the raft travelled though the barrels with the aid of the flow of the water, early distances were achieved to 460 meters with stable connections and vision from all the cameras, after this stage CTS used a live streaming system, all four camera feeds were streamed directly to the internet, a link was sent to enable others to view the cameras with a 5-10 second delay, The footage was viewable in 1080p HD and was saved directly to the cloud for instance sharing.

As the days and weeks passed the surveys and recces continued, it was discovered that some of the survey lengths where further than initially anticipated due to the access into the barrels,

CTS, Murphy, and Thames water had discussions to establish a way forward, further investigations were carried out to establish extending the cable length, eventually a 1200m cable was used to overcome the distance, signals from the cameras were not affected by this and the live streams continued to work with the same lag.

In conclusion the overall project and surveys where complex, considering the conditions the system worked, the result was 1080P HD wide lens video of the internal barrels and structures which allowed for close examination and analysis, overall, 12 kilometres of the Nos Sewers system was surveyed.

Wedge Block Tunnels (40 Kilometres)

Sat, 07 Oct 2023 04:47:21 GMT

Wedge Block Tunnels

The wedge block tunnels are large diameter sewer & Storm Tunnels that are in regular demand and use. As they came up for routine inspection, Thames water awarded the task of surveying them for inspection to Barhale and CTS.

The aim of our inspection surveys, are to identify the condition of the wedge block tunnels, assessing for any general condition & damage. With the size and the sheer distance these tunnels cover, CTS made the decision to invest in new equipment and also added additional hardware to enhance the lighting and Video imagery.

We invested in a crawler system, one that could tackle long distances, and overcome obstacles like silt and water flow. CTS also invested in the new cable drum, which allowed for surveys up to 500m in length.

Some of tunnels brought the challenge of flow levels, too high for the crawler to drive through. This was something we had prepared for.

In our workshop we had designed and built two float systems. Both vessels were equipped with enough buoyancy and protection to withstand the harsh environment. We kept the raft attached to the rope which came from the Porto reel and using a drogue system, we launched from one shaft and surveyed the tunnels whilst the raft floated down to the next shaft.

CTS teamed up with Barhale on site, and worked together to safely enter the deep, large diameter shafts. Safety was the number 1 priority, for our teams but also the public. For each entry, we set up a site around the manhole, barriering us off to prevent any hazards. Working directly from the back of the CTS survey van allowed us to complete our surveys effectively.

Where conditions were appropriate, we decided to put our innovative prototypes into practise. After extensive research and development, we had customised an RC Crawler system, that would prove to be faster and managed to reach 800m from our RF control unit. We improved this once more, by converting from radio frequencies to fibre optic cable allowing for survey lengths of 1200 meters.

Across 5 months of work on site, we surveyed a total 40 kilometres of wedge block tunnel, diameters ranging from 1.8 meters to 3 meters. Back in the office, CTS brought the footage and information into a suitable format to be viewed and analysed by our clients.

Docklands Rising Mains (800MM)

Sat, 07 Oct 2023 04:46:12 GMT

Docklands Rising Mains

Thames water own and maintain two 800mm rising mains which were originally installed, made from a GRP material. Over the years these mains have deteriorated and moved.

Thames Water sought expertise from CTS, Barhale and McAllister's to investigate, expose, survey and line the mains.

CTS used laser scanning Techniques to survey the rising mains, to assess condition and ovality. CTS evaluated this request and using our combined skills, designed and built a trolley in our workshop to house a 3D laser scanner. On site we deployed the trolley into the main and pulled it through, stopping at intervals to take static scans until we reached the other end.

Overall, we surveyed 700 meters from shaft to shaft.

Back at the office, all the laser scans were stitched together, to create a 3D point cloud of the entire lengths of the mains surveyed.

From the point cloud we created a 3D model, synced to OS national grid and created cut sections of the main, to show the ovality.

From the results of the surveys and modelling, we informed all involved what we had discovered. The mains had lost their true form and over the years with ground movement had distorted.

Railway Platforms (East – West)

Sat, 07 Oct 2023 04:45:25 GMT

Box Station Railway Platforms (East – West)

The client discussed with JMB the possibility of finding GFRP rebar in concrete at the platform edge over a distance of 250 meters on both east and west platforms. JMB researched the possibilities of using ground penetrating radar to capture this information accurately. After some testing it was decided that GSSI structure Scan mini was up for the job.

The first Stage of the contract was for CTS surveyors to attend site specific inductions to allow them to go trackside to carry out the surveys.

The Stage 1 Site Surveys were carried out by a Utility Surveyor using the structure Scan mini and the second surveyor collecting data which had been marked on the platform, we learnt quickly and found that there were Steel rebar back form the platform edge that gave a very good indication as to what was going on inside the concrete, although this was not part of the spec CTS management insisted on collecting this data to help build a picture of what was in concrete, this proved valuable information at a later stage and helped with understanding the GPR graphs that were be analysed on site.

The surveyor’s confidence was building from this and he soon got the knack for identifying the GFRP rebar that wasn’t showing to well at first. The surveyors worked as a team and with their setting out producers working well they covered over a 1000 meters with the structure Scan mini marking all the steel rebar and GFRP rebar that they could see on the screen of the structure Scan mini. Spaced at approximately 200mm apart they recorded 3500 pieces of steel & GFRP Rebar. But it didn’t stop there.

Stage 2 was carried out at the CTS design office were we started looking at the raw Data.

It was decided to build a decent picture of what was going on in concrete and to help visualise this a 3D model started to take shape,

The Cad Ops first built the platform and then placed the rebar at every point that was collected to identify either the steel or GFRP rebar. They were placed at a given average from the front face and the top the platform.

Once this process was complete we were a bit stuck, all of a sudden we had a huge amount of GFRP rebar missing, it was then we conceived a process to accurately place the missing rebar in the model. Using our Cad Skills, we scaled in the GPR graphs and then analysed all the data, it was becoming clearer and using a 4K PC we were able to place in the missing rebar from the graphs that we couldn’t see on the structure scans mini screen.

That was it, we found this processor worked well and we could validate our survey drawing with the GPR graphs, this was showed to the client who agreed the data output had been verified and was convincing enough to proceed to their next stage.

The data was presented in project folders with the 3D cad model DWG exported to a 3D PDF as well as top view 2d wireframe pdfs. The GPR Scans were imbedded within the Cad model for viewing purposes.

This was overall a challenging process of which we all learnt new skills and are now very confident in this process, ironically the last day on site we had been given the opportunity of testing the New GGSI XT machine which had just arrived into the country, we found this machine enhanced the readings and showed a clearer picture of the concrete and rebar.

Water Ring Main GPR Report

Sat, 07 Oct 2023 04:45:23 GMT

Water Ring Main GPR Report

Cable tracing Services Limited appointed by Barhale for Thames water to conduct a trial GPR survey of the Thames water ring main at Kew Gardens over 300meters. The trail using ground penetrating radar was to establish a view of the ground behind the concrete wedge blocks.

The tunnel constructed from 140 mm thick un-bolted concrete wedge blocks to form an internal tunnel

diameter of 2.90 m. The blocks are wedged together by the surrounding soil and thus rely on this external pressure to confine the blocks in place whilst also resisting the internal tunnel water pressures. Thus, removing external pressure (i.e., soil excavation) potentially impacts the TWRM.

The tunnel is approx. fifty meters deep, Access to the tunnel is Via a shaft with numerous landings, CTS had previously surveyed part of the tunnel with Laser scanning techniques.

Equipment…

CTS researched the world industry for GPR and used a touchless GPR system designed for tunnels, the equipment had was imported into the UK, the supplier provided schematics and specifications for the system.

Stage 1, Designing

CTS cad operators built a conceptual 3d Design in AutoCAD on how 360-degree coverage could be established.

using the previous point cloud data, the GPR manufactures specifications and 3d modelling, parts where sourced to build a bespoke trolley to house all the equipment on. The 3d design was critical to ensure all parts and equipment would fit through the hatch opening of the tunnel.

Stage 2. Building the trolley

The next phase at the workshop the trolley build began, steel section pipes and joints formed the box frame of the trolley, wheels where added, the GPR antennas were attached to a main pole that rotated 360 degrees to give the coverage around the tunnel, 4 cameras, lighting, a laptop, batteries, and leads made up the remaining equipment. On completion and testing of the trolley all parts were secured into holdalls and boxes ready for deployment.

The Survey…

November 2022 in dry weather 4 CTS confined space operatives arrived at Kew gardens shaft, after inductions and safety briefs the equipment and parts were transported down to the tunnel entrance, the equipment and parts was then lowered into the tunnel.

Within the tunnel 3 ops built the trolley and attached all the equipment, a4 sheets of paper with 10m increments where put on the tunnel walls, the first walk along the tunnel pushing the trolley was carried out, this formed part of the initial testing to see how the trolley would react, and to encode the meterage wheel attached to the trolley. Whilst this push was conducted the cameras positioned at 45 degrees on each corner of the box frame recorded video over the full distance and on the return journey. The GPR system was then started, using a clock count within the tunnel, the GPR antennas were positioned at 7 different angles and pushed the 300 meters to build up the picture of the ground behind the wedge blocks, as the trolley wads being pushed the GPR scan graphs were viewed on the laptop to ensure data was being recorded. On completion of the trial all equipment was removed from the tunnel and shaft, a final check was made to ensure nothing was left in the tunnel and shaft, all operatives now left the confined space.

The data and analysis…

Once the trial was completed the data and analysis of the GPR scan graphs was carried out at CTS offices, using the GPR manufactures software the scan graphs where imported, cleaned up and then exported, a 3d model of the tunnel was built along with a clock, the GPR scan graphs where aligned in 3d to the path taken in the tunnel, Chainage was added to the model, analysis of the graphs was carried out, disturbances or hyperbola with in the scan graphs where identified and a 3d solid block dimension to the antennas field of view where applied to the 3d model over the disturbances and hyperbolas, a picture started to form, its seems that from 9 to 3 o clock the ground is reasonably similar in density, their where very few disturbances in the scan graphs, at 3 to 9 o’clock the opposite, the graphs showed many disturbances and hyperboles, the graphs identify the possibility voids are forming or water behind the tunnel wall is moving the ground to compact it, there also a possibility that gout has washed out and gathered, holding in certain areas

The overall condition of tunnel looks to be in a sound state, their where some cracks on the surveyed parts of the tunnel which have been repaired with grout of concrete.

Conclusion…

The survey results will assist in the next phase of the analysis, if possible, core drilling in areas that the scan graphs show disturbances and hyperbolas will help to corroborate the GPR graphs, to ensure a soil sample comparative various core would need to be taken at intervals where there are also no disturbances or hyperbolas in the scan graphs.

Recommendations.

This has been a challenging and informative trail; much has been learned.

The trolley build worked well, with more time a better safer and more stable trolley can be built, other attachments can be added, the manufacturers equipment worked well, and I am satisfied that the results where of a high standard, more antennas could be added to prevent multiple passes although weight need to be considered. Longer distances can be surveyed.

The equipment is high value, CTS are resolute in working with Barhale and Thames water to survey the ring main with this system and repeat surveys will give overall analysis of the ground with overlap surveys.

Hinkley Bathymetric Survey

Sat, 07 Oct 2023 04:45:21 GMT

Hinkley Bathymetric Survey

The Ashby-de-la-Zouch canal runs north to south along the dock in Hinkley, which the proposed Hinkley to Hartshill pipeline would need to avoid.

The construction plan was to design a trenchless crossing underneath the canal, so a bathymetric survey was requested from J Murphy & Sons Ltd.

CTS began to research the most accurate and practical method, finding useful information from an online news article of the canal being drained in the past. At the time this was for a collapse in the footpath, but it allowed us to understand the canal’s structure and to what specification our survey equipment would need to be.

After investigation, the Hydrographic-Solution was the ideal device for this kind of survey.

The Hydrographic-Solution is a small, rugged, and lightweight vessel which is controlled via an RF remote. It holds a fitted GPS device which automatically collects levels to OS national grid. Our surveyors manoeuvred along the canal to survey a complete grid of levels including ground, water, and riverbank levels.

Back in the office, we portrayed the data in a suitable table format and calculated average ground levels. Alongside photos in a report this was delivered to the client for them to design their trenchless crossing.

Lidar & Sonar Testing on a Raft in a tunnel.

Sat, 07 Oct 2023 04:45:21 GMT

Lidar & Sonar Testing on a Raft in a tunnel.

A Trial to test Lidar and Sonar in a 2.7 meter diameter tunnel which had 40% effluent water has been carried out, this report provides feedback from the site procedures carrying out the survey, and an analysis of the data. The survey was carried out in the day from a large chamber to gain access into the tunnel, the water level was 3.5 meters from ground level, with a medium flow, the effluent water carried rag and other household waste. The raft was deployed with 4 cameras, a lidar sensor and sonar, the raft was tethered to a Porto-reel drum by rope, the cam-eras on the raft where tethered to a cable drum by means of fibre optic cable which allowed live streaming from the cameras within the tunnel, The Lidar and the sonar where mounted on the raft and connected directly to a battery and computer also mounted on the raft. The survey consisted of a 190 meter downstream pass, stopped and then pulled back upstream. Their was no man entry procedures required for this trial survey.

The lidar device used for the trail had the following spec…

VERTICAL RESOLUTION - 128 channels, HORIZONTAL RESOLUTION - 2048, RANGE—50m, VERTICAL FIELD OF VIEW -90° (±45°) , PRECISION - 15mm, WEIGHT - 447 g, INGRESS PROTECTION RATING IP68, IP69K.

The Lidar was mounted to the raft on top of a peli-box which housed the battery and computer.

As the raft travel along the tunnel the lidar data was recorded and stored directly to a solid state drive.

The Sonar device used for the trail had the following spec…

Acoustic Frequency: 2MHz Beam Width: 1.1 degrees conical Receiver: Logarithmic

Bandwidth: 500kHZ Pitch/Roll Sensors: 3 Axis accelerometers, resolution 0.1 degrees

The Sonar was mounted below the raft 300mm below the water line, the peli-box housed the battery and computer. A deflector shield was also mounted to protect the sonar from rag and debris.

As the raft travelled along the tunnel the sonar data was recorded and stored directly to a solid state drive.

After the trial the Lidar data was sent to a software engineer for post processing,

the Raw data was processed by means of SLAM registration, lets

explain… Simultaneous Localization And Mapping – it’s essentially complex

algorithms that maps an unknown environment.

Using SLAM software, a device can simultaneously localise (locate itself

in the map) and map (create a virtual map of the location) using SLAM algorithms.

Here's a video that shows a snippet of that process

After receiving the data from the software engineer, the next step begins,.

Using more common file types the data was imported and exported through various software's, the overall initial results are promising, considering the environment and technical challenges to carry out such a trial the end results are as follows…

The point cloud has an accuracy of +-15mm

No stretching or skewing has been seen in the data

The data can be aligned to known fixed positions

The sonar results are instant, when the raft is removed from the tunnel, the data can be viewed on the computer onsite, for both the sonar and Lidar an interim sanity check is carried out to ensure the hardware has stored the data. For this trail an older and reliable method of recording time durations thought-out the survey gave the survey crew sufficient info on analysis to understand where the raft was in the tunnel at any given time, the same info would be used for post processing purposes.

Here's some photos and video that shows the sonar da-ta as it travels along the tunnel.

The sonar data gives a clear indication of the underwater structure, debris, silt and has the ability to find underwater connections. The data can be used along with the software to take measurements and calculations, furthermore that post processed data analysis can then be combined into a Cad model, annotated and coordinated or even silt levels modelled into a 3d solid model.

The trial has involved many hours and days of R&D, 10 people in their respected roles have all contributed to a successful survey along 190 meters of tunnel.

The onsite set up and deployment posses the hugest challenge, that basically equates into how you get a raft and all its hardware down a manhole with-out any entry, as proven it can be done in the right circumstances, for now unfortunately man entry cannot be ruled out to deploy a raft, the main factor is the size and set up of an entry location,

The Lidar data is currently undergoing further slam analysis to improve on the dataset, improvements in hardware, Imu's and considering using more than one device are just a few current options, a new technology has just been released which involves instantaneous slam, this if proven to be effective will save post processing time and will help developers and engineers explore the possibilities of using Lidar in other areas.

The sonar results where very informative and effective, taking the raw data from the sonar to create a Lidar style point cloud of the under-water structure is yet to be explored,

The next stage for CTS will be to redesign the raft system, with 12 kilometres of raft deployment carried out this year and from this trial we now have a better understanding of the typical site conditions, how the hardware works, weight, buoyancy, flow, balance and more, further trails of hardware will be carried out. CTS will now seek to design a large system similar to the one in the trial and a smaller version, our existing trail raft can be deployed and used in the field Today.

Counter Creeks Project

Sat, 07 Oct 2023 04:11:49 GMT

Counter Creeks Project

Barhale awarded CTS 80% of the overall Counter Creeks project, The Purpose of the surveys will assist in the planning phase for new infrastructure, at Low level and the design of a Deep Tunnel.

CTS Carried out surveys in stages to assist in the Positioning of 49 Boreholes for Monitoring purposes and later large areas of PAS128 Type a Surveys to assist with planning, the company also carried out Laser Scanning of streetscapes, Bridges and Underground structures which were mainly Large Diameter Storm and Sewer tunnels.

The first Stage of the contract was for CTS to carry out C2/Plant Enquiry’s for the entire project, from this information Stat packs were created in PDF format and A3 Bound copies for the clients who used them for their site excavation teams to meet HSG47. CTS Used their IPad Airs to view all the information for the Project.

The Stage 1 Site Surveys for the Borehole locations were managed in-house and carried out by Two-man survey teams, One Utility Surveyor detecting underground pipes and the second surveyor collecting data which had been marked on the ground, upon completion the data was emailed directly from site to the office for the Cad drawing to be created in 2D top view with X,Y,Z coordinates to Ordnance survey National Grid, CTS used its Internally designed Feature and Attribute library which creates a Layering system to Statuary undertakers and incudes depths, sizes, configurations, widths, heights, types, Top of pipe depths, Invert levels and more. Upon completion these were sent via email or CTS WE Transfer account to the client to verify and then implement the final position of the bore hole, all 49 drills were successful from 10 to 30 meters in places. This demanding process was managed successfully and there were no hold ups to the drilling teams.

Stage 2 Site surveys were carried out on large areas from 500 meters to 4 kilometres from boundary to boundary and lot more detailed in the data to allow for 3D cad design of all underground utilities and Surface Features, including Signs, Street Lamps columns, Chambers, Tress and more. Again the CTS Feature coding allowed for the smooth transition from site data to office 3D Accurate Cad Design.

CTS implemented its own in house Traffic management vehicle to allow for surveys to be carried out in the carriage way on low speed urban roads, CTS Surveyors are trained in NRSWA for signing lighting and guarding.

Stage 3 Site Surveys were carried out on the large areas were a two-man Survey team used its owned Leica P40 Laser Scanner to scan the streetscapes, two rounds of scanning were carried out which included HD photography, the point cloud data was register using Cyclone software and the point cloud was created in True-colour, the files were provide to the client in. RCP, RCS Format and Truveiw format. The data was sent to the client on usb3.0 - 2TB Hard drives.

Stage 4 Site surveys were carried out in confined spaces, the same surveyors used the scanner to traverse underground to collect point cloud data in some very dark conditions, these were mainly large sewer and storm tunnels, a single round of HDS scanning using the P40 was carried out. The scans were later combined and registered with the streetscape scans to create accurate Line and level of the tunnels, the point cloud data was also used for condition surveys, the files were provided to the client in. RCP, RCS Format and Truveiw format all in Grey scale.

Stage 5 site surveys involved the surveyors entering into resident’s properties to carry out laser scanning of basements to allow for accurate line, Level and condition.

CTS Surveyors used their Thames water passport training to good effect with all property owner’s concerns being answered in a professional manner, the key focus on these entries were relationships first and care of duty to the residents and their property.

The large amount of detailed data was managed with a simplistic approach using the CTS internal cloud system, the survey data was set up in project folders by area and stored in the cloud which has a real-time back up system.

312de41d

Laser Profiling Case Study

CTS Rescue Training

CTS Rescue Training

ACTS (Alternative Crawler Tunnel System)

ACTS (Alternative Crawler Tunnel System)

Kew Gardens

Kew Gardens Water Mains

Park Royal/ Acton mark up.

Park Royal/ Acton mark up.

CTS Raft Build and Surveys (Nos Sewers, 12 Kilometres)

CTS Raft Build and Surveys ﻿

Wedge Block Tunnels (40 Kilometres)

Wedge Block Tunnels ﻿

Docklands Rising Mains (800MM)

Docklands Rising Mains

Railway Platforms (East – West)

Water Ring Main GPR Report

Water Ring Main GPR Report ﻿

Hinkley Bathymetric Survey

Lidar & Sonar Testing on a Raft in a tunnel.

Lidar & Sonar Testing on a Raft in a tunnel.

Counter Creeks Project

Counter Creeks Project

CTS Raft Build and Surveys

Wedge Block Tunnels

Water Ring Main GPR Report