RIPPING Many 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?”

RIPPING Physical characteristics which favor ripping are: Fractures, faults and planes of weakness Weathering

RIPPING Physical characteristics which favor ripping are: Brittleness and crystalline structure

RIPPING Physical characteristics which favor ripping are: High degree of stratification or lamination Large grain size Stratification

Production depends on: Tractor speed Shank depth Number of shanks RIPPING PRODUCTION Production depends on: Tractor speed Shank depth Number of shanks 2 shanks

Tractor speed RIPPING PRODUCTION The tractor develops its greatest drawbar pull in first gear. Generally speed should be between 1 and 1½ mph.

RIPPING PRODUCTION Shank depth Rip 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 3 shanks Single shank

SHANKS

RIPPING PRODUCTION Number of shanks The 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

Ripping-production chart

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 EXERCISE Step 1. Check Capability 370-hp tractor Trap 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 EXERCISE Step 2. Ideal Production 370-hp tractor Figure 7.23 Trap rock having a seismic velocity of 6,200 ft per second Conditions should be considered average. (half way between the A and B on the chart) 500 bcy/hr

RIPPING EXERCISE Step 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 EXERCISE Step 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  280 bcy/hr Step 4. Calculate Production

RIPPING EXERCISE  3.6  4 Step 5. Number of dozers Number tractors =  3.6  4 Must be an integer number

RIPPING Heavy ripping will increase machine maintenance requirements by 30 to 40%.