Friday, June 4, 2010

Road works and earthwork

A road is an identifiable thoroughfare, route, way or path between two places which may or may not be available for use by the public

Road construction requires the creation of a continuous right-of-way, overcoming geographic obstacles and having grades low enough to permit vehicle or foot travel. and may be required to meet standards set by lawor official guidelines.

(wikipedia)



this is my favourite part in construction stage. roadworks and earthworks are put under infra works. i think this part is the most challenging during construction stage because its deal with nature, good planning and proper work arrangement. even roadworks at my site is not massive as highway construction, but i still learn a lot.

reminder
* road and drainage must be in same direction interm of progress. it is better to finish drainage before we call for roadworks sub-con to start their work. or it is better award both of work to the same sub-con (it will be easier for main con)
* check a road level as stated in drawing with actual condition on site. maybe it need a little adjustment
* it is better for earthwork done before building constructed. it will give a good platform level, good compaction and construction debris will not available in soil.

roadworks stage.

1. platform level. (cutting/backfilling) to receive road level
  • at our site, most of road alignment involved cutting work ( OGL is higher than road level). at this stage, the challenge is more to planning of work ( where to start, what should start first, what we should remove and timeline. machinaries involved are excavator ( a must), backpusher and compactor.
2. road excavation.
  • it is follow a spec from consultant. at our site is is type 1, which consist of 100mm of sand, 375mm of crusher run, 60mm wearing course and 40mm binder course. so total excavation is 575mm.
  • deeping- is a part to checking excavation is fullfilled or not. by pegging at left,centre and right of the road. using measuring tape, measure the excavation level. due to chambering, centre must be at least 500mm, left and right shoul be 575mm.
  • compaction is a must before deeping. if we notice something unfamiliar (soft soil/high water table) do a testing, at our site, we notice soft soil at certain area. so our RE decided to conduct probe mackintosh test at certain point. from the probe result it will be decided what kind of treatment will be used.
  • at one point (near TNB 2) a treatment using sand 600mm is been used, make excavation is 1.1m. because it is so soft and water table are high.
problem:
  • some part, drainage are still not done, so water get stagnant and soil get watery, if crusher run are layed, it getting soaked (not good)
  • it is an alternatif to construct temporary earth drain to flow the water out from road
  • drainage not properly done, so temporary earth drain to flow out water from road allignment.
  • actually, we need this road to be done, to replace our temporary access, because still a lot of infra works (drainage, TNB, sewerage) will be at layed at temporary acess.
  • what i learn here, progress of work should be properly monitored.
3. testing
  • certain test should be carried out to ensure the quality of roadworks and to prevent future problem.
  • Mackintosh Probe
- carried out due to certain area of excavation, we detected a very soft soil. RE suggested to carry out a mackintosh probe. 3m depth or 400 blow over 1ft (whichever come first)
-
3 points at very critical area were chosen
- the result were compared and the decision only one area (about 50m long) need treatment (600mm sand backfilling)

proba mackintosh



600mm area sand backfilling
  • CBR test (california bearing ratio)
- is a test for subgred strength
- it should be more than 5% at penetration 5mm


CBR test for subgred

4. compaction
  • it is a very important stage in road construction
  • start with compaction of subgrade. using 30 tonne compactor.
  • 375mm crusher run is also divided into 2 layer (200mm and 175mm) to ensure compaction going well at this part.

earthwork and site clearance, well compacted road level.



laying crusher run


finish crusher run level and well compacted

machinaries used (compactor and excavator)

obstacles:
  1. before we called roadwork sub-con, we already called for infra M&E subcon for street lighting and telecom to start their work, but they cannot commit to it. so, we proceed to roadworks first.
  2. when finish level crusher run done, M&E subcon start their work. because their excavation and location of their pipe at side table (3m) and excavation has ruined half of the road and side table.
  3. compaction damage, crusher run also teared (due to their machinaries). C&S consultant have to instruct new rectification method and it involve cost and time. rectification is to re-excavate 2m length (from side table). and lay again sand, crusher run and compact again.
  4. due to drainage progress cannot catch up with roadwork progress, a lot of problem occured such as :- during excavation for drainage (crossing between building and at temporary access) all the transport for concreting, lorry to supply material use a not complete road, that cause a lot of trouble. 300mm crusher run layer completely disappear, road completely damage (as per attached picture).
  5. due to that, we has to considered a treatment using geotextile ( there goes my 6 month bonus)
  6. we can see that, the road become worst day by day ( it started about 30/5- 4/06/2010)
  7. for temporary, it just being compacted and lay with used premix. the rectification will be done after all the crossing and infra works done.

excavation for street lighting


excavation for telekom pipe (damage side table and certain part of road)




road damage (due to usage before well compacted/ done)


it became worst due to raining day...

* this situation also occur due to unproper drainage at side table. water ponding at centre of the road, soil became soft, and when heavy workload use it ( lorry/machinaries), it will be teared up.
* conclusion - if you fail to plan, it a plan to fail....


ENOUGH FOR ROADWORKS... (FOR THIS TIME BEING, DUE TO THE CONSTRUCTION ALSO STOP AT THIS PROGRESS) I WILL POST EARTHWORK IN A NEW PAGE.

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19 comments:

  1. this has been a great help for me as a junior engineer.. Thank you for posting these.. It would be really helpful if you could post more on the drainage system used.. Thanks again..

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  2. thanks reading my blog..but, the drainage system at this site is so conventional, nothing special about it :-)

    and now, i've change my job to the specialist..

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