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Thrust Boring

Thrust Boring is also part of “Flora Boring” service rendering to our valuable customers. In this field we are in well experienced hand and never fails to develop and use modern method and strategy.



To handle such type of works we can able to do Thrust Boring from 4” to 56”. We are using American Machine Ditch Witch to work from 4” to 20” and another machine bore it type fro 12” to 30”, and Boland Machine for 30” to 56”.



We done major works by using this machinery as mentioned in list of job carried out.



Thrust Boring Method Statement :

General

The Thrust Auger Boring is a method of Non-Destructive Road Crossing (NDRC). It is a method of simultaneously jacking a pipe horizontally through the earth while removing the soil by rotating auger, which is ahead of pipe.

Our BOR-IT machine model 24 is unit constructed, with ear selected direct drive rotation and controlled pressure hydraulic thrust. The machine had been designed to thrust bore upto 750mm dia.

It is equipped with auger, cutting heads machine power is provided by diesel engine mounted at the rear of the machine. The engine RPM and selectable gear of the machine control rotation speed. The machine is having a master casing pusher that encloses the spoil paddle assembly.

Special head unit is fitted in the auger in front of the casing to actually bore a hole for the casing to enter. There is special head for different soil conditions whether loose, stable or rocky.

Introduction to Method Statement

In this particular project, the thrust boring shall be carried out in dry soil conditions and the water table has effects.

Bore-IT Machine Model 24 shall be used in this project with standard cutting Head. The cutting head dia meter is 5mm greater than the outer diameter of the casing.



Procedures

1- Set out thrust receiving pits as per approved drawing ensuring that the location is free of obstruction and services.

2- All safety measures needed are to be taken in to consideration prior commencement of excavation, including warning taps and concrete barricades.

3- Thrust and receiving pits shall be excavated as per relevant approved drawings, nothing that trench shall be free of water by using dewatering pump at all times, during the operations, if found necessary.

4- The dimension of the Thrust pit shall be 10 meter long with a width of 2 meter for jacking 6-meter long pipe sleeves. If 3 meter long sleeves to be used, only the length of the Thrust pit shall be 7 meter depth to decided by the consultant / Client. But normally, the required for 200mm dia casing is between (1.2 to 1.5) meter and for 300mm dia the depth is between (1.5 to 2) meter.

5- Thrust and receiving pits excavation shall be 3 meter away from the edge of the road asphalt or 2 meter from the edge of the footpath.

6- Thrust pit shall be leveled and compacted to provide solid bid for the guiding tracks for proper alignment and level fixing at the required depth. Concrete thrust blocks shall be firmly fixed in excavated trench.

7- If the crossing is longer than 30 meter, it is recommended that 5cm thickness of the concrete to be castled in the Thrust pit to provide solid bed for proper alignment.

8- Thrust boring machine shall be installed in driving (Thrust) pit. The cradle guides shall be installed in front of machine to the correct line and level.

9- 300 or 200mm steel sleeves pipes 6 meter a long as required, shall be used in driving operation which will be initially slow to ensure that thrust boring is to the correct level & alignment. The spoil shall be retraced from the driving pit side.

10- Prior to work commencement, level control points shall be established to keep level monitoring during Thrust bore operation. These points to be fixed at edges and center of existing asphalt read. Level check by assigned surveyor to be recorded before, during and after completing proposed Thrust bore.

11- 6 / 3 meter length of 200 / 300mm dia steel pipe sleeves shall be jacked with consequent

12- 6 / 3 meter length pipe welded and jacked in the same manner.

13- The driving operation shall be continued till the head of cutter appears in the receiving pit side. At this stage, the auger shall be retracted from the driving pit side.

14- While taking all precautionary measures to avoid any settlement to the existing asphalt road as per requirements of concerned departments and applicable specification.

15- Once NDRC operation has been completed, the equipment shall be dismantled. The contractor shall reinstate the area.

16- Tolerances of misalignment (Vertical / Horizontal) are to be according to Contract specifications. i.e. The line and grade combined is 200mm / 100m. Installed pipes in the casing will be tested separately.

17- Removing of excavated material outside of pit from 6” to 12” by manually. If it is morethan 12” upto 30” by manual with our crane.

Thrust Bore works under soft sand area

- Various types of cutter heads used for different types of sand. Under soft sand area normal cutter heads used for.

Thrust Bore works under rock area

- Various types of special cutter heads used for different types rocks. Under rock area special heads used for.
- Minimum depth of cover over the crown of casing pipe shall be according to the requirements of contract.
- Minimum clearance between the thrust bit and edge of the road according to the requirement of contract.