桥梁施工工艺方案Method-Statement-for-Bridge.docx

METHOD STATEMENT
FOR BRIDGE, MICRO PILING, LOAD TEST AND CONCRETE WORKS

CONSTRUCTION METHOD FOR THE BRIDGE
OBJECTIVE
The objective of this method statement is to describe and outline a working methodology to ensure a fair degree of control, attention and consideration had been given to the construction of Bridge over Sg. Dapu, Sarawak.
SCOPE OF WORK
The scope of work will cover the work methodology for:
o Site Preparation
o Pilling Work (Bored Pile)
o Testing of Piles (PDA, Load Test and Pile Integrity Test*) o Construction of Foundation
o Construction of Abutment o Construction of Pier o Construction of Girder Beam o Launching of Girder Beam o Construction of Bridge Deck o Finishing work
WORK METHODOLOGY
SITE PREPARATION
a. Prior of any construction being carried out, location for the construction of the bridge shall be identified and check by the surveyor.
b. R.O.W. shall be verified to ensure no construction of permanent and temporary structures are out of the site boundaries.
c. If the required area for construction is insufficient, negotiation with adjacent landowner shall be conducted for the rental of the land for bridge construction activities.
d. Temporary crossing over different river shall be identified, assessed and constructed based on the most suitable solution available for each river crossing.
e. In order for the construction of the bridge abutment and pier, a working platform shall be constructed.
f. The surveyor shall identify and set on site the location of the abutments/piers for the bridgework.
g. For the abutment or pier which is located at the riverbank or in the river, working platform shall be constructed by extension of the river outwards to the river.
h. Suitable fill material from the earthwork activities shall be used to extend the riverbank outwards to the center of the river.
i. Adequate opening or gap shall be retained for the continuous flow of the river and also to provide access for the longboat travelling up and down stream of the river.
j. Existing logs and tree trunks from the site clearing work shall be used as anchorage or temporary retaining structure to retaining the fill material over the river bank where the working platform shall be constructed.
k. The working platform shall be properly compacted and fill up to the required level for the safe operation of pilling and abutment/pier construction.
l. Proper access shall be constructed to enable access for the pilling machine and delivery of material including concrete supplies.
m. The working platform shall be monitor from time to time to ensure its stability and safety.
n. A well compacted and flat casting yard shall be prepared for the construction of the girder beam.
o. The casting yard for the girder beam shall be located at an area which will not interfere with other construction activities and close to the bridgework activities. Access to the working casting yard shall be provided and maintained.
p. A storage yard shall be prepared next to the casting yard to store all the material required for the construction of the girder beam.
q. Worker’s quarters shall be constructed close to the casting yard and shall be provided with the basic facilities and complied with the requirement of the local authorities.
MICRO PILLING
PURPOSE
To outline the method statement by which Micro piles is carried out.
SCOPE
The scope of works for this method statement is to construct the piling works for Micro piles according to specification, dimensions, setting out and site preparation per design drawings.
REFERENCE DOCUMENT
The piling works shall be constructed in conformance to the followings:
Contract Construction Drawing
Contract Specification
SEQUENCE OF ACTIVITIES, SPECIFIED REQUIREMENTS AND VERIFICATON ACTIVITIES.
HANDLING
All API pipes must be lifted and transferred accordingly.
STORAGE OF MATERIALS
All API Pipes shall be placed on adequate support with adequate slippers in order to avoid slipped off from the storage area.
All pipes within a stack shall be in groups of the same size and length.
PLANT, MACHINERY AND EQUIPMENT
Micro piles piling rigs rotary wash and down the hole hammer type by using air flush come with water circulation wash, air compressor, welding sets, generators, concrete grouts mixer etc as applicable.
PREPARATION WORKS
Obtain relevant approved construction drawing from structural consultant.
Setting out for reference lines by marking on the peg.
WORK METHODOLOGY
a. The piles used for the project shall be as specified diameter. The size of the hole drill shall be as per construction drawings.
b. The piling points (position) shall first be set out by the surveyor to ensure all piles installed are as per indicated in the drawings.
c. Off set the piling position and make sure that the pile position can be set back accurately
d. Area where the pile is to be constructed must be cleared.
e. Upon confirmation of pile position, verticality of the pile will be checked by using spirit level.
f. Mobilizing the micro piles piling rig into position.
g. Drill with temporary casing until firm strata is encountered. The drilling technique used shall be both rotary wash and down the hole hammer.
h. Drill with appropriate tool until hard strata or rock is encountered or drill the hole to the required depth. If the length of the API is required to extend further to meet the required strata, API pipe shall be joined up by butt welding.
i. Upon confirmation, flash the hole until it is reasonable clean, then move the machine to the next position.
j. Insert the pile reinforcement into position and prepare the grout in accordance to construction drawing details as specified in drawing as well as take the necessary number of cubes for testing. (6 pieces per set, 2 for 7 days strength, 2 for 28 days strength and the remaining 2 pieces for reference). One set of test cube shall be taken for every batch of grout that being prepared for the mentioned work.
k. Pumping the grout to the drilled and cleaned pile position by inserting the tremie pipes or 32 mm HDPE pipes until the bottom portion of the pile, pump to flush the grout out of the drilled and cleaned hole until the acceptable grout is being flushed out at the top portion of the pile. Clean up the area around the pile.
l. Repeat the whole process for the next pile.
SAFETY PRECAUTION FOR PILING WORK
Workers shall follow approved HSE plan while carry out piling work. Personal Protective Equipment (PPE), warning signage, tool box meeting, competent operators, etc, shall be implemented and maintained during the phase of works.
EXPECTED OUTCOMES
The micro piles works are completely constructed according to the construction drawings and specification.
TESTING OF PILES
PDA TEST
a. Upon completion of the pilling work. PDA test shall be conducted.
b. The Resident Engineer shall select the pile to be tested based on the allocation provided by the contract for pile.
c. Pile head shall be prepared before PDA test is being carried out.
d. For Bored Pile, the top of the pile is to be provided with a steel sleeve for confinement /restraint against bursting of the concrete during impact from the hammer. The steel sleeve can either be installed during concreting of the pile or it can be a build-up section of the pile to be constructed over the top of the installed pile after selection of the pile to be tested. The concrete at the top of the pile is to be finished level and be of comparable strength with the pile proper to receive the impact from the drop hammer.
e. Two pairs of strain transducers and accelerometers are to be attached to the sides of the pile top at approximately diametrically opposing positions. Where possible, the sensors are to be attached at 1.5 times or more the diameter of the pile below the top of the pile. The sensors are attached to the concrete of the pile using mechanical anchors installed into 6mm nominal diameter holes drilled about 40mm into the concrete.
f. After the sensors have been installed onto the pile, the sensors are connected to the Pile Driving Analyser (PDA) using signal cables. A system check is then conducted and the relevant details of the pile are keyed into the PDA.
g. When the setup is ready, a test impact will be carried out to check the system and effectiveness of the selected parameters. Appropriate adjustments to the hammer such as height of drop, positioning and cushioning will be carried out where necessary. Similarly, fine adjustment of the sensors may be carried out if necessary. Further impacts for the Acceptance Test on the pile are then carried out. The test will be terminated upon successful demonstration that the mobilized pile resistance equals or exceeds the required test load.
h. The data for each impact will be stored, printed and submitted to the consultant for their perusal.
STATIC LOAD TEST
a. Upon completion of the pilling work. Static load Test shall be carried out on the Resident Engineer selected pile for testing.
b. The Resident Engineer shall select the pile to be tested based on the allocation provided by the contract for both bored pile.
c. The loading for the static load test for Bored Pile shall be as per the specifications for 600 mm diameter and 1000 mm diameter pile.
d. The ground surrounding the test pile shall be well compacted in order to set up the static load test.
e. Sufficient length of Pile above the compacted ground shall be maintained in order to carry out the test.
f. The Kentledge System is assembled with care. Extra care shall be taken during the placement and stacking of the I beam.
g. Extra care shall be taken when placing the concrete block onto the I beam frame.
h. The number of concrete block to be place shall vary pending the loading required.
i. The geometry of the arrangement shall also aim to minimize interaction between the test pile, reaction system and reference beam support.
j. A hydraulic Jack and calibrated load cell reacting against the main girder and the test pile is placed. A steel plate is place between the test pile and the hydraulic jack in which the dial gauge will measure the movement of the steel plate.
k. Four (4) numbers of dial gauges is fix to an independent steel support frame to measure the displacement of the steel plate.
l. Movement of the pile head shall be measure using the four (4) numbers of dial gauges and checked with leveling instrument against a scale ruler fixed to their holder. Another scale ruler shall be fixed as independent references point or bench mark to be rested on the ground protected and firmed inserted into the ground.
m. All testing equipment shall be protected against any disturbance prior to and throughout the load test.
n. The loading sequences shall follow the Resident Engineers specification including the step and duration.
o. Records shall be kept throughout the testing period and submitted to the consultant for their perusal at the end of the loading test.
PILE INTEGRITY TEST
a. Once all the bored pile had been completed Pile Integrity Test can be carried out on all the bored pile.
b. The top of the bored pile shall be prepared for the test to be carried out.
c. A small accelerometer is to be held on the pile, parallel with its axis.
d. The pile will then be struck with the hammer provided by the testing equipment for a number of times pre-determined and deem necessary by the testing team.
e. The data from the sonic method shall be stored into the equipment and submitted to the Consultant for their perusal.
f. The same process is repeated until all the bored piles are being tested.
ABUTMENT
a. Upon the completion of the pilling work, as built survey shall be carried out on the piles and submit for the consultant perusal, o Once the pilling work had been approved, the construction of the abutment shall begin with the construction of Pile Cap. o Surveyor shall off set the dimension of the abutment for control during the construction process.
b. The working platform is then excavated down to the cut off level of the pile.
c. Once the excavation has reach the required level, a layer of lean concrete shall be pour to prepare a working area for the construction of the pile cap.
d. As the piles had been exposed, the pile head shall be hack and cut to the required level. Extra length of the pile shall be removed from site.
e. The inside of the pile shall then be roughened and the starter bar inserted into the pile as per the construction drawing.
f. Reinforcement work shall then be carried out on the pile cap while the formworks are being prepared.
g. Prior of any casting. Site Engineer shall check the dimension and reinforcement detail to the construction drawing.
h. Once the Site Engineer is satisfied with the work, a joint inspection shall be carried out by the R.E./C.O.W. and the contractor’s representative for approval of casting.
i. Only with the approval from the consultant's representative shall the casting be allowed.
j. Concreting shall be carried out with the supervision of the C.O.W. and the Site Supervisor.
k. Concrete shall be pour into the structure evenly by alternating the pouring location. Proper compaction shall be achieved with the use of the concrete vibrator.
l. Concreting work shall continue until the finishing level had being achieved and the finishing level being properly compacted and screed.
m. Formwork shall be left overnight for the setting of the concrete and removed once the site engineer is satisfied with the strength and hardness of the structure.
n. Upon the removal of the formwork, curing shall be applied to the structure. This is achieved by either using a curing compound or damp gunny sag.
o. The abutment shall be cast in 3 sequences. First section shall be the pile cap and then continue with the abutment wall and finally ends with the wing wall casting.
p. The construction shall then move onto the construction of the abutment wall starting with the reinforced work and then the formwork and finished with concreting work.
q. The same process shall be repeated for the abutment wing wall.
PIER
a. Upon the completion of the bored pilling work, an as built survey shall be carried out and submit for consultant perusal.
b. Once the pilling work had been approved, the construction of the pier shall begin with the construction of Pile Cap.
c. Surveyor shall off set the dimension of the pier for control during the construction process.
d. The working platform is then excavated down to the cut off level of the bored pile.
e. Once the excavation has reach the required level, a layer of lean concrete shall be pour to prepare a working area for the construction of the pile cap.
f. As the bored piles had been exposed, the pile head shall be hack and cut to the required level. Extra length of the pile shall be removed from site.
g. Reinforcement work shall then be carried out on the pile cap while t