DOE 2000. - Waste Isolation Pilot Plant - U.S. Department of Energy

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 4
However, based on experience with the Site and Preliminary Design Validation (SPDV) rooms and the
rooms in Panel 1, pattern bolting is not expected to be required until 2-5 years after excavation. Disposal
rooms may be pattern bolted prior to waste emplacement. The expert panel convened to study Panel 1 in
1991 concluded that the then current support technology of 10 ft (3.05 m) long mechanical bolts used in
Panel 1 should be adequate to ensure stability for 7 to 11 years from the time of excavation. These bolts
were installed beginning approximately two years after initial excavation on a pattern described as a 5 ft
by 5 ft (1.5 m by 1.5 m) offset pattern (one bolt per 25 ft 2 [2.3 2 m]). Experience in Panel 1 confirms the
conclusion of the expert panel. Plans call for bolt systems installed in future bolt patterns to be equal to
or exceed the bearing characteristics of the mechanically anchored bolts used in the primary pattern in
Panel 1.
The justification for choosing these systems includes their demonstrated ability to support the expected
loads. In the case of yielding systems, they will be chosen based on their support capabilities and the
ability to accommodate expected rock deformation.
Primary support will consist of Grade 75 steel mechanically-anchored bolts of at least 5/8 in (1.6 cm)
diameter. Depending on the need, the bolts may be as short as 24 in (61 cm) and as long as 72 in
(183 cm). Mesh may be chain-link, welded wire, or polymer.
Pattern bolting will be designed using the best support technology available at the time. Because
yielding systems are still under evaluation, current plans call for use of Grade 60 threaded bars of at least
7/8 in (2.2 cm) diameter installed on a maximum 5 ft by 5 ft (1.5 m by 1.5 m) pattern in the center half of
the room. The bars would be resin-anchored above the first clay/anhydrite interface. Four or 6 ft (1.2 or
1.8 m) long mechanical bolts would be used near the ribs.
Materials procured for installation as primary support, spot bolting, and pattern support will meet the
requirements of 30 CFR 57, Subpart B. 4 This requirement will be verified as part of the quality
assurance program. Primary support installation requires quality control by the installation crews.
Proper installation is confirmed as part of the audit function of the underground safety and Quality
Assurance groups. Quality control and assurance is more rigorous during a pattern bolting sequence.
Work instructions for the sequence will require Quality Assurance to perform at least one random
inspection to verify that material requirements and hole construction specifications are met.
Operations (construction) supervisors will also be responsible for monitoring the construction. Finally,
before turnover or completion of the installation, Quality Assurance will review the work, and certify
their approval. Independently, MSHA inspectors also perform a Quality Assurance function during their
frequent inspection visits to the WIPP, making certain that support construction is performed in
accordance with 30 CFR 57, Subpart B. 4
Supplementary Support Systems
Similar to the plan for pattern bolting, any supplementary system will be designed using the best support
technology available at the time. Should a supplementary support system be required, it is anticipated
that, if not already in place, mesh will be installed over the primary and pattern support. The mesh will
be augmented either by cables (wire ropes) anchored near the ribs and suspended across the rooms or by
steel mats. The cables or mats and, therefore, the mesh will be further pinned to the roof by bolting. The
use of either the cables or mats in conjunction with meshing and re-bolting should be adequate in
supporting even a highly fractured roof beam.
4.3-13 January 28, 2003