Závitové trubky plné nebo perforované pro ponechání ve vrtu pro účely stavební, zakládání, degazaci nebo odvodnění.
Nejčastější rozměry jsou OD 89 mm, 101,6 mm, 108 mm, 114,3 mm.
Application and profile
Tube umbrellas become use in unstable soil and rock for the tunneling, to save the work and make the job faster. This kind of working principle was developed in 1970, and was used in casing diameter of 114 and 140 mm. Till from 1997 EDC start to provide six different casing sizes which can be used on standard Jumbos. As a rule tube umbrella is used in a saw or tooth profiles (pictures below). It is the overlapping between the tunnel's top and the ground surface less us 10 meters, it will be a flat profile (Picture 1). The standard length of a tube umbrella section is between 12 and 18 meters and the overlapping from section to section 3 to 5 meter. With the new develop casing shoes from EDC you can make also tube umbrella holes with 30 m lengths.
Working principle and finish
The casing use in 2 or 3 m length, of each casing is always a question of the weight from one pipe.
The drilling job is doing with standard jumbo. (Tamrock, Atlas Copco, AMV). The first pipe is provide with a Symmetric ringbitsystem, that you get straight hole. The drilling, it self is doing with a drill rod, that is during inside of the casing. In this kind of system the casing not rotated and you need a very low troque. If the first casing is drilled in to the soil you put the next casing include a drill rod on the mast an connect together and start the drilling again.
After the tube umbrella section is ready drilled the grouting working start the grouting can be doing on different method´s. (Grouting plug, single or double packer).
Possible outside pipe diameters for pipe umbrellas:
|Outside Diameter||Wall Thickness||Bit Connection||Hydraulic Hammer||DTH Hammer|
|76 mm||max. 7 mm||MF R 32||Yes||No|
|89 mm||max. 8 mm||MF R 32||Yes||No|
|102 mm||max. 8 mm||MF T 38||Yes||No|
|114 mm||max. 8 mm||MF T 38||Yes||No|
|133 mm||max. 8 mm||MF T 45||Yes||Yes|
|140 mm||max. 10 mm||MF T 58||Yes||Yes|
|152 mm||max. 10 mm||SD4 o.5||No||Yes|
|168 mm||max. 12 mm||SD5||No||Yes|
Working principle of the pilot and ring bit
The pilot bits are with three mud holes provide and they end in low ? lying flushing slots. This slots go to the side of the pilot bit and there in to the back flushing slots. With the low ? lying flushing slots you get a better reflushing from the mud in to the casing.
Effect of the tube umbrella
After the strengthen of cement absorb the tunnel roof the load from the ground over the tunnel. You can calculate 1000 kg - 4000 kg each pipe.