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Pulling-Power of Equipment Depth and Patterns of Movement Use the following rule of thumb for tractor horsepower (hp) whenever deep ripping and As previously noted both Phase 1 Deep Ripping through significantly compressed, exposed subsoil decompacting a significantly impacted site: For both types of implement, have at least 40 hp of and Phase 2 Decompaction (deep subsoiling) through the replaced topsoil and upper subsoil need tractor pull available for each mounted shank/ leg. to be performed at maximum capable depth of each implement. With an implement’s guide wheels attached, some have a “normal” maximum operating depth of 18 inches, while others may go Using the examples of a 3-shank and a 5-shank implement, the respective tractors should have 120 deeper. In many situations, however, the tractor/implement operator must first remove the guide and 200 hp available for fracturing down to the final depth of 20-to-24 inches per phase. Final wheels and other non essential elements from the implement. This adapts the ripper or the deep depth for the deep ripping in Phase 1 is achieved incrementally by a progressive series of passes subsoiler for skillful pulling with its frame only a few inches above surface, while the shanks or (see Depth and Patterns of Movement, below); while for Phase 2, the full operating depth of the legs, fracture the soil material 20-to-24 inches deep. deep subsoiler is applied from the beginning. There may be construction sites where the depth of the exposed subsoil’s compression is moderate, The operating speed for pulling both types of e.g.: 12 inches, rather than deep. This can be verified by using a ¾ inch cone penetrometer and a implement should not exceed 2 to 3 mph. At shovel to test the subsoil for its level of compaction, incrementally, every three inches of this slow and managed rate of operating speed, increasing depth. Once the full thickness of the subsoil’s compacted zone is finally “pieced” and maximum functional performance is sustained there is a significant drop in the psi measurements of the soil penetrometer, the depth/thickness of by the tractor and the implement performing the compaction is determined. This is repeated at several representative locations of the construction soil fracturing. Referring to Figure 8, the site. If the thickness of the site’s subsoil compaction is verified as, for example, ten inches, then implement is the 6-leg version of the deep the Phase 1 Deep Ripping can be correspondingly reduced to the implement’s minimum operable angled-leg subsoiler. Its two outside legs are depth of 12 inches. However, the Phase 2 simultaneous Decompation (subsoiling) of an 11 inch “chained up” so that only four legs will be thick layer of replaced topsoil and the upper subsoil should run at the subsoiling implements full engaged (at the maximum depth), requiring no operating depth. less than 160 hp, (rather than 240 hp) of pull. The 4-wheel drive, articulated-frame tractor in Figure 8 is 174 hp. It will be decompacting this Fig. 8. A deep, angled-leg subsoiler, ideal for unobstructed, former construction access area Phase 2 decompaction of after the topsoil layer simultaneously through 11 inches of replaced is graded on top of the ripped subsoil. topsoil and the upper 12 inches of the previously deep-ripped subsoil. In constricted areas of Phase 1) Deep Ripping, a medium-size tractor with adequate hp, such as the one in Figure 9 pulling a 3-shank deep ripper, may be more maneuverable. Some industrial-grade variations of ripping Fig. 10. An early pass with a 3-shank deep Fig. 11. A repeat run of the 3-shank ripper implements are attached to power graders and ripper penetrating only 8 inches into this along the same patterned pass area as Fig. 9; bulldozers. Although highly durable, they are worksite’s severely compressed subsoil. here, incrementally reaching 18 of the needed generally not recommended. Typically, the 22 inches of subsoil fracture. shanks or “teeth” of these rippers are too short and stout; and they are mounted too far apart to achieve the well-distributed type of lateral and Fig. 9. This medium tractor is pulling a 3- Typically, three separate series (patterns) are used for both the Phase 1 Deep Ripping and the vertical fracturing of the soil materials shank deep ripper. The severely compacted Phase 2 Decompaction on significantly compacted sites. For Phase 1, each series begins with a necessary to restore soil permeability and construction access corridor is narrow, and the moderate depth of rip and, by repeat-pass, continues until full depth is reached. Phase 2 applies the infiltration. In addition, the power graders and 120 hp tractor is more maneuverable for Phase full depth of Decompation (subsoiling), from the beginning. bulldozers, as pullers, are far less maneuverable 1 deep ripping (subsoil fracturing), here. for turns and patterns than the tractor. Every separate series (pattern) consists of parallel, forward-and-return runs, with each progressive 7 8 Page 307 of 1493