Surveying technical Surveying on the by Clare van Zwieten, PositionIT

Gauteng’s freeway network is undergoing a much-needed major overhaul and the 1,4-million people using these congested roads are already experiencing the effects of this construction work.

owever, if road users think Tolling will take place via an open road The original aerial mapping was used that the upgrade work is toll system to avoid slowing down by the appointed civil engineers to Hinconveniencing them, they traffic, and all toll transactions will take complete the preliminary designs, need to give a thought to how the place automatically and electronically while the above-mentioned higher traffic is inconveniencing the surveyors at toll collection locations. Vehicles accuracy conventional survey contracts and construction crews working on the will be issued with “transponders” were necessary for the final designs freeway upgrade. and as vehicles pass under gantries, and quantity calculations for both Freeway Improvement placed approximately 10 km apart, an the construction of new lanes and Project automatic transaction will take place. structures along the route.

To improve Gauteng’s traffic flow and SANRAL has awarded seven contracts, Trail Surveys was awarded two tenders to provide a road network that would worth over R11-billion, for the first by SANRAL to provide a detailed stimulate the province’s development phase (125,5 km) of the GFIP. Over topographical survey of two portions potential, the South African National the next three years upgrading of on the N1 running from 14th Avenue to Roads Agency (SANRAL) proposed that the following freeway sections will Kilometre 35 and from Kilometre 35 to the existing road network be improved take place: N1 from Soweto to the the Buccleuch Interchange. and that additional infrastructure be in ; from Alberton to Surveyors provided. This led to the development Buccleuch; Sections of the south of of the Gauteng Freeway Improvement as well as the N12 from Trail Surveys appointed seven field Project (GFIP), a joint venture between Gillooly’s to the to . teams to the project with the survey SANRAL, Gauteng Province, and the responsibilities allocated as follows: This article focuses on the surveying Ekurhuleni, Tshwane and Johannesburg l Project leaders: Hanno Schoeman, Metros. work undertaken by Trail Surveys and Franscouis Maré and the GFI Contractors Joint Venture on the The goal of the GFIP is to provide Philip Schalekamp. GFIP. an interconnected network of inner l Structures: Danie Roelvert and and outer ring roads as a solution to Trail Surveys Mof Muller. the traffic congestion experienced in l General surveys: Fantie Botha, To enable design of the GFIP, SANRAL Gauteng. It is predicted that the project Ernest Baatlhodi, Siphiwe Mohale, awarded eight mapping contracts will contribute -billion to the GDP Kobus Spangenberg, Mable by the end of 2009 and that almost (N1S20) in 2007 for various sections Mamoshe, Jack Chiloane and 30 000 direct jobs will be created of the freeway network. The mapping Thabo Setale during the construction period. from the eight awarded contracts were l CAD: Charmaine Marnewick combined with existing aerial mapping Equipment The initial construction period runs in order to have one map for the eight from July 2008 to May 2010 with continuous contracts that were used for The equipment used by Trail Surveys construction expected to be complete all the design purposes. was made up of a combination of by May 2010. Should this not be the case, work will be halted for three months to facilitate smooth traffic flow during the FIFA 2010 World Cup and will resume afterwards.

Project description

The -billion project will involve the provision of additional lanes, interchange improvements and intelligent transport management systems, including cameras, ramp metering and electronic signage. To encourage the use of public transport the roads will include high occupancy vehicle lanes that can be integrated with bus rapid transport systems, taxi, bus and train routes. Fig. 1: Surveying across the traffic on the N1.

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various brand names. The GPS-RTK systems included three sets of the Trimble 5700, a Trimble R8 and a Leica 300 series. The total station equipment ranged from the Leica 405 High Power (Booker software), the Trimble 5600 (Trimble data controller), the Sokkia Set5 (Logger software), the Topcon GTS4 (Quess software), the Topcon 302 (Logger software), and the Topcon GPT 1002 (Logger software). A Topcon DL101C and two Zeiss NI2 levels were also utilised during the course of this contract.

All mapping was done in Model Maker and then exported to the required Drawing eXchange Format (DXF) and Fig. 2: Surveyors had to drive from the north-bound side of the freeway to an Microstation formats. Results were off-ramp, drive to the on-ramp and get back onto the south-bound carriageway presented to the client according to the just to complete work on the opposite side of the road to where they had been required technical specifications working previously. in Technical Methods for Highways (TMH 11). beacons using conventional level are acting as references for the Methodology methods. (Level and check.) appointed civil contractors that began The scope of the survey included, l Survey of road prism – implementing the design in July 2008. from fence to fence, the tarred surface north-bound, intersections, Challenges sides, the median, river crossings, all cross-roads, river crossings structures and on- and off-ramps within and structures. (Prismless total The challenges started during the the road reserve along the route (see stations.) tender process with most parties Table 1). The methodology involved the l Survey of road prism – providing very similar estimates as following: south-bound. (Conventional to what the job would cost. Two companies, however, tendered almost l Horizontal fixing and verification methods.) double for each contract. It turned of existing control beacons l Arrange data, check, re-survey and out later that these companies had using RTK-GPS and conventional mapping. methods. (Double polars.) been involved with previous work l Compile data records and mapping. on the R21 and had more realistic l Vertical fixing and verification of (TMH 11 specifications.) existing control beacons using expectations of the work requirements. conventional level methods. (Level Work on the project commenced in Experience has shown that the totals and check.) February 2007 and ended in June provided by these companies were a 2007. The mapping from the two areas l Construction of new beacons. more accurate reflection of the costs (North-bound and south-bound.) allocated to Trail Surveys, along with involved in undertaking the required that from the six other N1S20 contracts, work. l Horizontal fixing of new control were then combined with the existing beacons using RTK-GPS and aerial mapping. This was coordinated The biggest challenge for the Trail conventional methods. (Double by MHP Geomatics who did the quality Surveys’ team was the traffic. polars.) control on behalf of SANRAL. The The noise on the side of the N1 is l Vertical fixing of new control benchmarks placed by Trail Surveys unbearable and the constant noise was a major distraction preventing surveyors from hearing each other, Description Unit Surveyed quantity hearing their cell phones, and generally making it difficult to think (see Fig. 1). Maintenance of beacons Beacons 2 Building of beacons Beacons 118 Workers on the GFIP, including the surveyors, are not allowed to cut across Horizontal fixing Beacons 118 the carriageways and heavy penalties Levelling Beacons 124 are imposed on offenders to deter DTM – road prism km 25 people from crossing the median and DTM – ramps and cross-roads km 15 endangering their lives and that of the drivers using the freeway. DTM over- and under-passes km 3 Due to these restrictions, surveyors River crossings Crossings 10 working on this contract had to drive Rail crossings Crossings 0 from the north-bound side of the freeway Structural detail surveys Structures 37 to an off-ramp, drive to the on-ramp and get back onto the south-bound Table 1: Description of survey work undertaken by Trail Surveys on the GFIP. carriageway just to complete work on

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Fig. 3: Cross sections drawn in Road Maker showing the varying elevation levels between the north-bound and south-bound carriageways as well as the layerworks.

the opposite side of the road to where they had been working previously. This sometimes took an hour, depending on the traffic conditions (see Fig. 2).

SANRAL appointed two companies to assist the surveyors working on the eight contracts with traffic accommodation. The companies provided high impact vehicles, flagmen and road signs to alert motorists. Surveying took place between the key peak hour periods (09h00 to 15h00), and even then traffic volumes remained very high. The median had to be surveyed on Sundays.

The number of teams required to complete the work made quality control and logistics a concern on this contract but the appointed project leaders managed this effectively.

GFI Contractors Joint Venture Fig.4: Design illustrating the upgrade work planned for the Rivonia Interchange. The Gauteng Freeway Improvement (GFI) Joint Venture was awarded the contract to upgrade a 21 km stretch along the N1 between 14th Avenue and the Buccleuch Interchange in July 2008 (work package B). Participants in this joint venture include WBHO Roads & Earthworks, Sanyati Construction, Rainbow Construction, Glash Construction, Munasi Civil Contractors, and Patula Construction.

Contract

The GFI Contractors Joint Venture is responsible for widening the section of the freeway running from Kilometre 27 all the way through to Kilometre 48 so as to provide an extra lane on each side of the freeway. Space for these extra lanes is being taken from the existing median that separates the north-bound and south-bound carriageways. The existing median will be replaced by a narrow concrete median made up of interlinked New Fig. 5: Japie Diedericks, Sifiso Mgozi and Alan Edmunds of the Jersey barriers. WBHO Roads & Earthworks surveying team.

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Due to the lane widening, the existing Similarly existing telecommunications, to check on the surveying work bridges along the route need to be electrical, sewer and water lines at all the undertaken by the GFI Contractors widened to close up the gaps created major intersections and where existing Joint Venture team on the structures by the lane widening. In total fifteen bridges are being widened, have to be and the layers. bridges will be widened and four new moved and decisions taken as to where Surveying equipment bridges will be going up in the vicinity they can be moved to. The difficulty here of the Rivonia Interchange. Retaining lies in getting the various utilities moved Each surveyor uses their own total walls will be utilised where the varying by the responsible parties who are not station with brands ranging from elevation levels of the north-bound and working to the same fixed time schedule the Leica TCR 303, Nikon 352, south-bound carriageways, require this as the GFI Contractors Joint Venture. Topcon DT11D and Sokkia Set 3. Due to be done (see Fig. 3). All side drains to the length of the contract area, two Surveyors on the freeway are to be replaced and GPS systems – the Trimble 5700 base additional drainage facilities are to be The surveyors working for the GFI and 5800 rover combination – are positioned alongside the median barrier Contractors Joint Venture will be being run on site. The total stations are due to the increased run-off expected focusing on ensuring that the levels used mainly for the structures while as a result of the lane widening. are correct, checking the structures the GPS systems are being used for i.e. bridges and incorporating the new the bulk earthworks. The GPS systems The on-ramps at the Malibongwe design with the existing freeway design are manned systems as the nature of Interchange are going to be shifted as well as the layerworks. the design does not suit using GPS out, and new slip lanes constructed so controlled graders. The total stations that it becomes a clover interchange. Heading up the survey department and levels are being used to check on Due to space constraints the existing is Alan Edmunds who is working with the tolerances. The levels being used structure at the William Nicol a team of experienced surveyors on site include the Sokkia SDL 50 Interchange is merely being extended, responsible for each of the major electronic level and the Leica NA 720 while the Rivonia Interchange is getting intersections: Andries Mulder (Rivonia and NA 820 levels. a whole new face-lift. New slip lanes Interchange); Victor Phahlamohlaka are being constructed at the Rivonia (William Nicol Interchange); and Japie The surveying team is using three of Interchange and the existing bridges Diedericks (Malibongwe Interchange). the Model Maker Systems packages are being widened. In addition two new Satellite camps with offices have been – Model Maker, Road Maker and Pipe loop off-ramps from the north-bound set up at each interchange to make Maker. Most of the digital terrain and south-bound carriageways are also logistics easier. models (DTMs) are done with the being constructed. GPS, and are downloaded back at the Working in the median are survey office with Trimble Geomatics Office to Overall the surveying work on this operators Sifiso Mgozi, Sipho Tswu and calculate the earthworks volumes. Road contract is fairly routine with the Sam Yaphi. They will be based in the Maker is being used to calculate the exception of the intricate Rivonia median doing levels and working with volumes and to check that two designs Interchange design (see Fig. 4), which the total station. Dumisani Malindise – existing and new – tie up with each requires a lot of checking to ensure and Vusi Mthimkulu are the GPS other. there is seamless integration between operators who will be working in the the new and existing structures. median or anywhere needed on site. Methodology

Due to the widening of the lanes, The consulting engineer on this work The consultants provided the GFI SANRAL’s existing fibre optic cable for package is SSI and Danie Grobler from Contractors Joint Venture surveying their cameras has had to be relocated. Omega Surveys has been contracted team with the benchmarks that were placed by Trail Surveys and these were verified. Tolerances are being done according to COLTO, with 20 mm accuracy for the elevation of the layers and 5 mm for concrete works.

Traffic

The biggest problems on this job are the safety and the traffic accommodation. As it is not possible to close the freeway to allow construction to take place, construction has to take place around the traffic. This makes for very dangerous working conditions. (A survey assistant on one of the other contracts was killed when a motorist collided with a safety vehicle parked on the side of the road where a survey was taking place.)

The speed limit on the freeway has been dropped to 80 km/h because of Fig 6: Support structures for a bridge widening on the N1 being put into position. the reduced width of the lanes, however

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design clashes in the early stages of construction will save time and money.

Bridge pilings

Work on the support structures for the bridge widening has been done. The piles are in place and the bases prepared for positioning of the new abutments (see Fig. 6). The structures are being done now so that the bridge-widening teams will be finished with the drilling work for the piles before the rains start and the rivers start filling up. Once the abutment is cast, the precast beams will be placed. In preparation for this the GFI Fig 7: Preparing for layerworks at the Malibongwe Interchange. Contractors Joint Venture team is busy surveying the existing bridges in order to check the required lengths for the precast beams. Once the beams are many drivers are ignoring the lower It will be used to transport material correctly in place the deck sections will speed limits. The safety of road users, from outside the freeway (where the be laid over the beams. drivers, passengers and construction layer material will be mixed), across workers is a huge concern and road the carriageway above the cars via The surveying work involved in this works signboards have to be maintained conveyor belt. On entering the median process is routine with the focus every day. the road material will be dumped onto being on ensuring that the various the back of a truck that will drive up elements of the bridge structure are SANRAL has procedures and times as and down the median delivering it as positioned correctly. Working from to when lane closures can take place. and where required. existing structures is a lot easier for This traffic accommodation makes surveyors than working from design as work on the project more complicated Initially the pugmill will be situated this usually involves queries regarding and is one of the largest expenses close to the William Nicol Interchange the levels and the lengths. However the on the contract. The coordination on the south-bound carriageway. challenge when working from existing required to access the site, the Once the layerworks in this area structures involves ensuring that the required safety equipment, and are complete, the pugmill will be new design elements are tying in with the time delays with deliveries and dissembled by cranes and moved to the the actual existing structures. procurement of required materials next location where layerworks will be come at a considerable cost. taking place. An issue that had to be dealt with by the surveying team was that the Accessing the median is a nightmare Traffic has also made it difficult for the original design coordinates for the so the construction crews stay surveyors to access the benchmarks existing bridges did not tie in with the permanently in the median. If one of (situated on either side of the freeway) actual existing structures. This resulted the personnel working in the median when working in the median. Just to in the surveyors having to physically is needed elsewhere, he has to be get from one benchmark to the other measure off the existing structures, set picked up and transported to where he requires a 14 to 20 km drive to get out the piles, pick up coordinates for is required. Construction workers enter from one side of the freeway to the them and then include the coordinates the median early in the morning with other. To avoid these time-consuming onto the as-built drawings. official transport and come out in the manoeuvers the surveying team put afternoon. To facilitate this, traffic is new benchmarks in the median, which Layer preparations either flagged down a way back or a involved levelling them and fixing the The layerworks on this contract are specially marked construction vehicle YX coordinate. made up of three different of types of is called to move into the fast lane to Work to date layers: the selected, the subbase and slow traffic down in the area enabling the bitumen-treated base. The two the vehicle from the median to merge Construction access to the project layers of selected, consisting of G6 with the traffic. area is controlled by SANRAL, which and G7 graded material, are laid first. determines when and where work takes As construction trucks can’t be Next come the two layers of subbase place in an effort to minimise traffic expected to merge easily with fast consisting of graded gravel mixed disruptions. As a result work on the traffic when exiting the median, a with cement (3%). This gives the project is being done in chunks. pugmill mixing plant together with a subbase layers an extra bond thereby conveyor constructed over the freeway The two main aspects that are being strengthening the road to meet the will be used for the safe transfer of worked on at the moment are: the anticipated traffic loads. Following this materials into the median working area. bridge pilings and the layer preparations. is the bitumen-treated base and on Construction of the 41 m by 2,6 m As part of this process the surveying top of this comes the 50 mm layer of conveyor structure is intended to prevent team has loaded the work package asphalt seal. construction traffic from interfering with design onto computer and checked The off-ramps require a slightly the regular running traffic. for design clashes upfront. Identifying different layerworks – the

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bitumen-treated base is replaced with batter poles and the location of vehicles complicates routine surveying with crushed stone – as the reduced utilities pinpointed. During layerworks it and construction work dragging speed of the off-ramp traffic results in is important that the fill levels are not simple tasks out over much longer decreased road loads. overfilled as this results in excess road time periods and adding to overall material being used. Any materials construction costs. Each of the three layers (150 mm placed above this point will not be paid thick) needs to meet a certain grade There is also the risk of surveying and for by the client. construction personnel becoming used as required by the consultants and to working alongside fast moving traffic the surveying team is responsible for Once extra material has been used in a and making careless movements into ensuring that these conditions are met. layer the only way to get it back is to the path of oncoming traffic. Likewise use an excavator to try and remove it. there is the heightened accident risk as Before layerworks can begin, the utility However this is a costly time-wasting drivers become used to and increasingly services need to relocate their pipes. exercise and often it is simply cheaper frustrated with the construction work Once the roadwork is complete, the and easier to leave the extra volume in utility services personnel return to lay taking place on Gauteng’s highways. It place. is going to be a case of headaches all their pipes and excavate the stormwater around until work on this much-needed drains. Drainage pipe work known as On completion of the lane-widening project is complete. subsoil drains also have to be placed and structures work, the existing alongside the layerworks to cut off concrete sections of freeway are going Acknowledgement any groundwater that may come from to be covered with a 50 mm overlay of premix. This blacktop will assist with I would like to thank Alan Edmunds and the side to penetrate and soften the Philip Schalekamp for their assistance dampening the noise volumes from the layerworks leading to the creation of with this article. potholes. freeway. Contact Alan Edmunds, Conclusion The surveying team has been preparing WBHO, Tel 083 325 7779, the roadbed for layerworks (see Fig. 7) Traffic is the biggest challenge facing [email protected] and and work on the layers will start once the surveying teams working on Philip Schalekamp, the pugmill is up and running. The cut the Gauteng Freeway Improvement Trail Surveys, Tel 012 347-7879, and fill lines have been marked out Project. The continuous flow of [email protected]

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