C.B.R Test

C.B.R test is abbreviation of California Bearing Ratio test. The test was developed by The California State Highways Department, California USA in 1930. It is developed to evaluate the mechanical strength of road structures. The road structures are defined as subgrades, lower subbase and upper subbase. Subgrade material is referred to soils, sand for lower subbase, whilst crusher run for upper subbase.
Generally the test performed is either Laboratory Test or Insitu CBR Test (on site). The test should be carried out in accordance with BS 1377. The good CBR value for road structrures is more than 5%. For value less than 3% is considered as poor material or Unsuitable Material (USM). During construction of road or pavement structures, samples existing subgrades shall be taken for test. If the value is less than 5%, the existing subgrade shall be removed at certain depth and replaced with suitable materials.

Environmental Matter

Environment is normally referred to all living things and non-living things occur on Earth. In construction work, protection of environment from pollution shall be taken into account before the start of construction. Project consultant or Engineer is the key person to review the topography of the project and responsible to protect the properties and facilities adjacent to the project from environmental pollution that originates from the project.
The potential effects of construction on the local environment such as blowing dust, heavy rains causes flash flooding, silting of stream and drainage system and traffic congesting due to construction operation. During construction operation the most common environmental problem encountered is slope erosion by rainfall. There are two slope protection method, turfing or cover by plastic sheet. Turfing is the best way to protect slope and it should be carried out as quickly as possible after slope cutting. Plastic sheeting is consider as temporary prevention measure for slope protection.
Rainfall commonly cause erosion of exposed soil. Prevent soil erosion from contaminating the open water such as stream, lake or other water body is the must requirements of construction. Sedimentation basins and silt fences are the common practice to prevent surface runoff and eroded soil directly flowing to the local streams and lakes.
Blowing dust is normally could be happened during dry season and a large amount of silt-particles could be produced at construction traffic area. Wind blowing may lift large amount of particles to high enough to transport them distances. Wind dust may damage to crops and vegetations, local residents and vehicles. Spraying water on top of dust is the best way to prevent blowing dust. Water bowser lorry is commonly used at construction area.

Embankment Fill

Another activity related to Earthworks is Embankment Fill works. Embankment Fill work is filling of suitable material or earth at valley or low ground area up to designated level as per construction drawing.

METHOD OF CONSTRUCTION

1. Materials for filling the embankments shall be suitable materials obtained from approved source or borrow pits.
2. Prior to commencement of filling work, the suitable materials shall be tested for Proctor test, moisture contain test, liquid limit test, plastic limit test, atterberg limits and sieve analysis and the test result should comply to requirement and specification.
3. Trial compaction for embankment fill shall be carried out at designated area of site project to get the rolling compaction pattern.
4. After the rolling compaction pattern accepted by Engineer, the earth filling shall be carried out layer by layer with approximately 300mm thick. The layers shall be compacted by vibro compactor as follow the accepted rolling compaction pattern.
5. All compacted layers shall be tested for Field density test (F.D.T) and the numbers of test point shall be accordance to specification and Engineer's advise.
6. All tests on site or at laboratory will be witnessed by Engineer or client’s representative. They will be notified to witness the test at least a day before. All the test results should be initial by laboratory technician and approved by Engineer.
7. Excavator will be used to loading suitable material on dump trucks at borrow pit area. A few numbers of dump truck will be used to transport the materials to embankment fill area. After the materials were unloaded motor grader will spread it on a layer with approx. 300mm thick and than compacted by vibro roller.
8. To avoid congestion and to ensure smooth flow during transporting the materials, two lanes haul roads shall be constructed.
9. A water bowser shall be provided at site project to control flowing dust. Flowing dust could be happened especially during dry season. Normally dust will spreading and flowing at hauls roads area. To control dust, water bowser could spraying water frequently a day.

Below are the number of machineries to be used during construction;

1. Excavator - For slope trimming, bulk excavation and loading to dump truck.
2. Dump trucks - For transporting the material from the cut area or borrows pits to form the embankment.
3. Bulldozer - Ripping and loosening of rock earth. Frequently the bulldozer is used for pushing and spreading the earth in layer for compaction.
4. Motor Grader - The motor grader can be used for spreading of sub-grades, shoulders, ditches and back slopes, maintenance of haul road.
5. Backhoe - Excavation below existing ground in firm or hard material as in digging pipe trenches.
6. Water bowser - For control dust on working area.
7. Compactor/Vibrating Roller - SAKAI CA 25 Vibrating Roller and DYNAPAC CF 51 - Compacting soil