METHODOLOGY FOR CONSTRUCTION OF WELL FOUNDATIONS

 

 CONSTRUCTION OF WELL FOUNDATIONS.

A)            SETTING OUT:

The centerline of the road will be marked, in the portion where the bridge is to be constructed, based on the GPS points already available. Subsequently, the center of the individual wells will be marked. A temporary benchmark will be established near the well foundations and got approved by the Engineer.

 

B)            GENERAL DESCRIPTION:

 

Ø     LOCATION OF BRIDGES HAVING WELL FOUNDATION :

Sl.	Bridge No.	Chainage	No. of Well	Dia of Well

 

D)         MACHINARY TO BE USED:

 

Crane

Grab buckets – capacity 1.5 cum

                                                Excavator / J.C.B. which ever is applicable

                                                Chisels of appropriate sizes

                                                Batching Plant of capacity 30 M³/ hr

                                                Weigh Batches of Capacity 500 Kg.

                                                Petrol/Electrical Vibrator & 60mm Nozzle.

                                                De-Watering Pump

                                                Transit Mixer 

Other relevant tools.

 

E)         SEQUENCE FOR CONSTRUCTION OF WELL FOUNDATION:

 

01.  CUTTING EDGE :

 

Ø  The mild steel cutting edge will be fabricated in four segments.

Ø  It will place and assembled in site at the time of executing well foundations.

Ø  The cutting edge will be erected on firm level ground.

Ø  After assembling of cutting edge, steel strakes of required height as per drawing will be welded.

Ø  Cutting edge will be prepared as per MOST Clouse No. 1900.

                                                                                                      

     02. WELL CURB :

 

Reinforcement work

Ø  Steel reinforcements will be assembled as per drawing.

Ø  The bottom ends of vertical rods will be fixed securely to the cutting edge by welds.

Ø  Epoxy Coated Steel only will be used in the reinforced concrete.

Ø  Bar Bending Schedule will be prepared according to the drawing and submitted for Engineer's approval.

Ø  The coated reinforcement bars should be protected against any damage

Ø  The reinforcement bar should be tied together properly at every intersection and lapping.

Ø  Reinforcement Steel will be as per MOST Clouse No. 1600.

 Form work

Ø  The design drawing for formwork will be submitted for approval to the Engineer.

Ø  Formwork will be as per MOST Clouse No. 1500.

Concreting Work

Ø  Concreting will be done in one continuous operation.

Ø  The concreting layers will be limited to about 450mm.

Ø  Adequate No. of Needle vibrator will be used for proper compaction of concrete.

     03.  WELL STEINING:

Ø  The height of steining shall be calibrated by making four gauges.

Ø  The gauges will be start with zero at bottom of the cutting edge.

Ø  Marking of the gauges will be done carefully with a steel tape.

             Form work

Ø  Details’ drawing for shuttering and supporting arrangement is as per approved Drawing.

Ø  Steel formwork of a height of 1.8m will be provided for the well steining.

Ø  The formwork on outer face of well steining will be removed after 24 hours of concreting & inner face will be removed within 48 hours.

Reinforcement work

Ø  Steel reinforcements will be assembled as per drawing.

Ø  Wherever necessary, reinforcement will be fixed by welding process.

 

            Concreting Work

Ø  Concrete cover block of required size will be provided for reinforcement work.

Ø  Regarding concrete procedures please follow sequence 3.

Ø  Laitance formed top surface of lift shall be removed to expose coarse aggregates before setting of concrete for the next lift.                                                                                                                    

    05. WELL SINKING:

Ø  The well will be sunk by excavating material uniformly from inside the dredge hole.

Ø  The well will be uniformly seated at the founding strata. Water jetting may be employed for well sinking wherever necessary.

Ø  Loading of the well with knetledge will be placed in an orderly on the loading platform. Loading will be commenced only after 48 hours of concreting.

Ø  Tilts and shifts will be carefully checked and recorded in the format.  Wherever any tilts is noticed adequate preventive measures like placing eccentric knetledge, pulling, strutting, anchoring or dredging unevenly, water jetting etc. shall be adopted before any further sinking.

Ø  After a portion of well has been sunk, another height of well steining will be cast and further sinking will be carried out.

Ø   Well sinking tilt shift  format has to recorded jointly with Engineer.

      06.        BOTTOM PLUG :

Ø  Before commencing plugging, all loose material from the bottom of the well will be removed.

Ø  For bottom plug, concreting will be done by tremie pipe method.

Ø  Concrete mix will be as per drawing. Concreting work will be done in one continuous operation till the concrete filled up to the required height..

07.   SAND FILLING:

Ø  Sand filling will be started after a period of 3 days of laying of bottom plug.

Ø  Sand will be filled up to the bottom of top plug, as mentioned in drawing.

Ø  Sand will be cleaned and free from earth, clay, clods, roots, boulders etc. Compaction will be done properly as direction of Engineer.

   08. TOP PLUG :

                     After filling of sand or concrete upto the require level a plug of concrete will                           be provided over it as shown on the drawing.

   09. WELL CAP :

Ø  A reinforced cement concrete well cap will be provided over the top of the staining in accordance with the drawing.

Ø  Reinforcement will be assembled as per drawing.

Ø  Bond rods of steining shall be anchored in to the well top.

Ø  Properly designed false steining will be provided as per drawings

10. CURING : 

Ø  Conventional water curing will be carried out for the stipulated duration.

Ø  Hessian cloth will be used for ensuring the proper curing work.  

        SAFETY MEASURES:

A)    Provisions for workmen:

Ø  It is required that all persons working at the site shall be provided with the safety equipments, protection means such as hand gloves, safety helmets and other necessary kinds.

Ø  All persons working on the site shall be trained by conducting the training course for safety to ensure that they are fully aware of the contents.

B)   Provisions for Equipment, Machine:

Ø  All equipment will be ensured to operate safely, maintained and repaired periodically.

Ø  All power equipment should be insulated and covered to all exposed live parts.

Ø  A competent person shall inspect equipment during shift duty.          

C)   Provisions for Job Site:

Ø  Relevant Caution boards and sufficient lighting system shall be installed at the working area to ensure safety for construction activities at night time.

Ø  The working area shall be free from hazards before starting the work.

Ø  Unnecessary materials such as empty bags and rubbish shall be removed periodically.

Ø  Proper safety measures like barricading, guard poles painted with florescent in alternate bands, flags etc. will be provided prior to the commencement of excavation operations.