ripping many contractors, when investigating a project, ask the question “do i have to blast?”...

RIPPINGMany contractors, when investigating a project, ask the question “Do I have to blast?”That is the wrong question.What we should investigate is

“Can I rip?”

RIPPINGPhysical characteristics which favor ripping are:• Fractures, faults and planes of

weakness• Weathering

RIPPINGPhysical characteristics which favor ripping are:

• Brittleness and crystalline structure

RIPPINGPhysical characteristics which favor ripping are:

• High degree of stratification or lamination

• Large grain size

Stratification

RIPPING PRODUCTIONProduction depends on:• Tractor speed• Shank depth• Number of shanks

2 shanks

RIPPING PRODUCTION

Tractor speedThe tractor develops its greatest drawbar pull in first gear.

Generally speed should be between 1 and 1½ mph.

RIPPING PRODUCTION

Shank depthRip at the maximum depth that penetration and traction allow.

Rip to a uniform depth if possible.

This is very important when scrapers are being used to haul the material.

RIPPING PRODUCTION

Shank depth at the start of a pass.

Shank depth during the pass.

SHANKS

Number of shanks

Single shank

3 shanks

SHANKS

RIPPING PRODUCTIONNumber of shanksThe correct solution lies in trial and error.• Start with one in the center pocket.

If the material breaks satisfactorily • Try two, one in each outside pocket• Three may act as a rake and hold slabs under the ripper.

RIPPING PRODUCTION ESTIMATES

Seismic-Velocity Method, most ripping-production charts are based on the relationship between rippability and the seismic wave velocity response of a material. Fig. 7.23

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RIPPING PRODUCTION ESTIMATES

A refraction seismograph can be used to determine the top of bedrock, and the thickness and strength of rock layers at or near the ground surface.

RIPPING PRODUCTION ESTIMATES

Raw seismograph data. It takes training to read and interpreter the data.

RIPPING EXERCISE

How many 370 hp dozers are needed to rip 8,000 bcy of trap rock in 8 hours. The rock has a seismic velocity of 6,200 ft per second. The conditions should be considered average. Efficiency will be a 45-minute working hour.

RIPPING EXERCISEStep 1. Check Capability370-hp tractorTrap rock, seismic velocity 6,200 ft/sec.

See Figure 7.18, which is for a 370-hp tractor.

Should be able to rip trap rock with seismic velocity up to 7,000 ft/sec.

RIPPING EXERCISEStep 2. Ideal Production370-hp tractor Figure 7.23Trap rock having a seismic velocity of 6,200 ft per secondConditions should be considered average. (half way between the A and B on the chart)

500 bcy/hr

RIPPING EXERCISEStep 3. Adjust for Igneous Rock with high seismic velocity

In igneous rock with seismic velocity of 8000 fps or higher for 850-hp tractors, and 6000 fps or higher for the 305 through 570-hp tractors , the production values shown on most

charts should be reduced by 25%.

RIPPING EXERCISEStep 3. Adjust for Igneous Rock with high seismic velocity

In igneous rock with seismic velocity of 6000 fps or higher reduce by 25%.

Trap rock having a seismic velocity of 6,200 ft per second

Reduce production by 25%

RIPPING EXERCISE

Step 4. Calculate Production

Production =

500 BCY / hr 0.7545 min hr

60 min hr

280 bcy/hr

RIPPING EXERCISEStep 5. Number of dozers

Number tractors =8,000 BCY

280 BCY / hr 8 hr

Must be an integer number

RIPPING

Heavy ripping will increase machine maintenance requirements by

30 to 40%.