Reference: CTS Case Study GPR for Railway Platforms (East – West) JMB 28-05-2016 (Link to Full Report)
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 meterswith 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 piecesof 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.
Reference: CTS Case Study for Counter Creeks Project (Chelsea & Kensington ) JMB. 21-05-2016 (Link to Full Report)
The client 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.
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