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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 4
Presently, only the construction of these areas is planned. The above drifts extend from S-1600 to
S-3650 (i.e., 2,050 ft [625 m] long). Crosscuts (east-west entries) will be 20 ft (6.1 m) wide by 13 ft
(4 m) high by 470 ft (143 m) long. The layout of these excavations is shown on Figure 4.1-3.
Panel 1 is the first panel to be used for waste disposal, and was excavated from 1986 through 1988. Its
rooms and access drifts have been rock-bolted to assure stability. Panel 1 has been re-bolted with
threaded bar resin anchors. In addition, Room 1 has been supplied with a supplementary roof-support
system consisting of rock bolts, steel channel sets, and a wire-mesh and lacing system. The DOE intends
to mine panels in the following order:
Final ½ Panel 10 (access drifts for Panels 1,2,7, and 8)
Panel 2
Panel 9 (access drifts for Panels 3,4,5 and 6)
Panel 3
Panel 4
Panels 5 through 8
At normal operating (waste throughput) rates, rock bolting in Panels 2 through 8 may only be required
locally (i.e. spot bolting). Rock fixtures used at WIPP comply with 30 CFR 57, 1 Subpart B. Each
ground control support system installation is individually assessed and evaluated. As a result they vary
from time to time and place to place.
A discussion of the design life of underground disposal rooms is included in Section 4.3.9. An
evaluation of the effective life of the underground rooms in Panel 1 was performed during April 1991, by
a panel of geotechnical experts. The panel members concluded that if no additional remedial measures
were taken, the rooms in the panel would likely have a total life of seven to eleven years from the time of
excavation using the installed roof support system, consisting of patterned mechanically anchored
rockbolts. Experience in Panel 1 confirmed the conclusion of the expert panel.
Plans call for bolt systems installed in the future to equal or exceed the bearing characteristics of the bolts
used in the primary pattern in Panel 1. The configuration of Panel 2 through 8 will be similar to Panel 1,
therefore; the performance of these rooms should be similar to those in Panel 1. Supplementary support
systems will further extend the effective life of the rooms, should they be required. A detailed discussion
of initial and supplementary support systems is included in Section 4.3.9.
The support system will be subjected to longitudinal and lateral loading due to the rock deformation.
The anchorage components may undergo lateral deformation due to offsetting along clay seams or
fractures and increasing tensile loading. Rigid, non-yielding support systems are not designed to
accommodate salt creep; however, they do respond to creep and continue to provide support during
ductile behavior. Yielding support systems are currently being evaluated in the WIPP underground.
These systems are designed to yield at predetermined loads, and provide support over their prescribed
yield interval without maintenance. Preliminary data indicate that the design and performance of some of
these systems are clearly superior to rigid systems in their ability to respond to salt creep while
maintaining adequate ground support.
Because the disposal area access drifts must remain open and operational for a much longer period than
any panel, they will require additional consideration from time to time. They are subject to regular and
systematic inspection and evaluation, and appropriate ground control measures will be implemented
whenever necessary.
4.2-26 January 28, 2003