Method Statement -Earthworks

1.0 OBJECTIVE

To outline the method statement by which the earthworks are carried out. This shall include method statement for excavation and backfilling works.

2.0 SCOPE

 The activities for earthwork shall consist of many stages that include:

·         Preliminary work

·         Excavation

·         Excavation in rock (if any)

·         Embankment fill

·         Slope protection

 

3.0 REFERENCES

·                Construction Drawings

·                Project Specifications

·                Surveying Field Book

 

4.0 DEFINITIONS

       -Nil

 

5.0 RESPONSIBILITIES

·                Safety Officer/Supervisor

·                Site Manager

·                Project Engineer

·                Land Surveyor

·                Site Supervisor

 

6.0 MATERIALS

       -Nil

 

7.0 HANDLING AND STORAGE OF MATERIALS

Handling         : Transport of materials shall be carried out by dump trucks / other suitable machinery.

     Storage            : Nil

 

8.0 PLANT, MACHINERY AND EQUIPMENT

Excavator                    : For bulk excavation and slope trimming.

Dump truck                : For transporting the material.

Bulldozer                     : For ripping, loosening of earth, pushing and spreading the earth in layers for compaction.

Motor grader              : For spreading, leveling and shaping works

Backhoe                      : For general excavation in trenching works.

Water bowser            : For spraying of water.

Compactor                 : For compacting soil

Back pusher               : For spreading and leveling.

Survey equipment    : Theodolite / leveling.

 

9.0 PREPARATORY WORKS

Earthworks is based on the information and data obtained in the following document:-

 

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9.1               Earthworks shall be carried out in accordance with standard code of practice (refer to BS 6031 : 2009) approved by consultant/consultant’s representative.

9.2               Approved Pre Com plan endorsed by relevant Authority and Topographical Survey endorsed by Licensed Surveyor.

9.3               Obtained relevant approved construction drawing from consultant/consultant’s representative.

9.4               Set out the location, centre lines and limits of works.

9.5               Set out the toe peg and finish level for the work.

9.6               Set temporary earth drain and outlet structure before earthwork start.

9.7               Prepare temporary shoring or any slope protection if required for work safety.

9.8               During earthwork, temporary earth drain, sediment pond and outlet structure shall be maintained regularly.

 

10.0 WORK METHODOLOGY

 

10.1  Preliminary Works

         i.            Temporary perimeter drain with silt trap and lorry wash trough shall be constructed as per drawings.

        ii.            Temporary drain shall also be constructed from identified ponding areas to drain out the water prior to any inspection and testing.

      iii.            Joint inspection shall be conducted with the Consultant Representative to identify location of unsuitable /over wet materials and marked on a layout plan.

      iv.            Suitable earth shall be imported from cutting area to be identified by the Consultant Representative.

        v.            Survey to establish existing ground level (EGL) and proposed formation level shall be in accordance with contract, specification and drawings.

      vi.            Surveyors shall establish center line, boundary, slopes and level markers using wooden pegs with appropriate tags or colour coded for easy reference. OGL survey drawing shall be submitted before any actual earthwork to commence. OGL drawing shall comply with the contract requirement.

     vii.            All encumbrances shall be cleared or isolated with proper boundary markers.

   viii.            Inspection shall be conducted to confirm PBM and proposed TBM.

 

10.2  Excavation

         i.            The excavation works shall proceed first at the location of cut areas detailed on the EGL survey drawing to perform the waste and treatment pond.

        ii.            Prior to any cutting / excavation works, the surface of the ground shall be cleared of any waste, rubbish material, organic material and etc using the excavator to scrap the top surface.

      iii.            Excavation shall commence using excavators to form the required slope and formation level which are control by the survey pegs. Excavation to be kept dry whether in open cut or in trench.

      iv.            The excavated common material (not inclusive of rock) loaded into the dump truck and transport to the designated filling area or temporary stockpile area approved by Consultant Representative.

        v.            Any unsuitable materials identified as such shall be removed and transferred to other designated area upon approval from the Consultant / PMC Representative.

      vi.            Excavation materials for embankment fill shall be tested and complied with the clause 2.4.1(e) of the Technical Specification.

 

10.3  Excavation in Rock (If any)

         i.            Normal hydraulic excavation method cannot be employed for excavation of rock in trench or pit.

        ii.            For this, the rock shall be loosened either by drilling or blasting or by pneumatic tools. Normally pneumatic breaker or explosives are used to disintegrate the rock formation depending on the type and quantity of the rocks. The excavated rock shall be transport to the Consultant Representative approved stockpile area.

      iii.            A method statement shall be formulated and submitted upon encountering new method of excavation in rock (if necessary).

 

10.4 Embankment Fill (if necessary)

         i.            Suitable fill materials shall be hauled by dumper trucks to the designated fill areas.

        ii.            If suitable fill materials cannot be spread immediately, it shall be deposited at temporary stockpile area and then shall be shaped and compacted to ensure proper surface drainage.

      iii.            The fill material shall be deposited, spread, levelled and compacted using vibro compactor exceeding 20tonne. The maximum loose thickness for fill is 500mm each layer. For compaction of embankment slope, the fill shall be extended 600mm beyond the design slope and then trim back to the required slope angle. Degree of compaction for the whole embankment below the top 300mm of the subgrade shall not less than 90% of the Maximum Dry Density (MDD).

      iv.            When compaction has reached the full berm height, motor grader shall be used to grade the surface to the line, grade and level for the next construction activities.

        v.            The fill layer shall be built up evenly over the full width or up to the roadworks limit only (to facilitate the subsoil drain construction) with sufficient width (to ensure adequate compaction) and shall be always maintained with sufficient camber to avoid water ponding.

      vi.            In-situ Field Density Testing and CBR test shall be carried out on the subgrade and subsequent layers at the rate specified in contract or as deemed necessary at location to be selected by the Consultant Representative.

 

Subject to FDT result approval, compaction of the layers shall be continued as the following :-

·         If FDT passed – proceed next layer

·         If FDT failed – proceed with rectification and retesting

 

     vii.            Upon confirmation of the Consultant Representative, the subsequent layer shall be carried out as per sequence until formation level is reached.

   viii.            Each inspection sheet shall be signed off every day by contractor and the Consultant Representative.

 

10.5  Slope Protection

         i.            A gentle gradient shall be adopted to have a more stable slope.

        ii.            Where the condition of high gradient (i.e. steep slope), turfing of the area shall be applied or staggering of slope shall be done (if applicable) to prevent any erosion due to weather or other means.

 

10.6   Inspection and Test Plan

As the progress of the preparation for the earthwork, there are few inspections involve for conformation and assurance of the specified requirements.

The inspections required are:

                       i.             Field Density Test

Ø  Core Cutter Method

Ø  Sand Replacement Method – small cone

Ø  Sand Replacement Method – large cone 

                     ii.             Soil Compaction Test with Soil Classification Test (Proctor)

                    iii.            California Bearing Test

Ø  Lab CBR Test (soaked)

Ø  In-situ CBR Test using Core Cutter method (soaked)

Ø  In-situ CBR Test using Load to carry out at site.

                    iv.             Grading Test (Sieve for Analysis)

                     v.             Mackintosh Probe Test

The testing equipment and laboratory apparatus required are as below:

·         A balance accurate to 0.01g

·         A balance accurate to 0.5g

·         Air-tight non corrodible metal container (50mm OD x 25mm high)

·         Desiccators

·         Scoops

·         British Standard sieves as follows :

75mm, 63mm, 50mm, 37.5mm, 28mm, 20mm, 14mm, 6.3mm, 5mm, 3.35mm, 2mm, 1.18mm, 425mm, 212mm, 150mm and 63mm and appropriate receivers.

·         Cone penetrator or Casagrande liquid apparatus

·         Other suitable accessories and equipment necessary to carry out density test (including In-situ Test) sieve analysis, liquid limit analysis, CBR, Mackintosh probe and etc.

 

11.0 TRAFFIC MANAGEMENT AND MONITORING

11.1 Maintenance of existing roads, footpaths and service drains, etc.

The construction team shall maintain all existing site excess, roads, footpath, service drain, etc. and reinstate any damage caused by any reason whatsoever during the progress of the works.

It will be the Safety Officer/Supervisor’s responsibility to ensure that ingress and egress to the site are kept free from obstruction brought about by the work on this site and in no way shall cause hindrance to traffic or ancillary works either by his own vehicles or by his work people, material, etc.

 

12.0 SAFETY PROGRAMME

12.1    Temporary Works and Public Safety

The Safety Officer/Supervisor shall be responsible for submission of plans and drawings to the relevant Authorities for the construction of all the necessary temporary drains and desilting pits, safety nettings for the works.

The Safety Officer/Supervisor shall provide adequate signboards at all strategic positions warning the public to keep away from the work site and erect temporary fencing and barriers where necessary around the site to prevent unauthorized trespassing during works.

 

13.0  ENVIRONMENTAL PROGRAMME

All works should be carried out in accordance to best practice environmental management as defined in the EMP.

13.1    Site Access.

The access as well as the portion of public road and walkway connected with it shall be kept clean and safe at all times.

 

13.2    Temporary Work.

Existing drain shall be identified by contractor together with the flow of drain until discharge point in order to make use of it during clearing work. Silt trap shall be provided before any discharge of surface water within site towards existing drain. This work should be completed prior to the commencement of any site clearing activities.

Temporary earth drain shall be constructed along clearing area to retain the surface water from dismissal directly towards existing drain. Desilting work shall be carried out regularly and the existing drain will be maintained during site clearing work.

As the slope area will not be disturbed, the existing turf or grown grass shall be remain and only manually cut the grown trees without uprooting it. Plastic sheet /canvas will be provided on site on standby basis in order to be use as slope protection if necessary.

Any effluent discharges from the site must comply with the Third Schedule of the Environmental Quality (Sewage and Industrial Effluents) Regulation 1979.

 

13.3       Waste Management.

Any construction wastes, solid wastes and domestic wastes other than schedule wastes must be disposed-off at the approved disposal site. On site compositing for biodegradable waste is allowable but land filling and open burning activities for the solid waste are strictly prohibited.