Technical Review of the Lined Rock Cavern Concept and Design ...

Technical Review of the Lined Rock Cavern (LRC) Concept and Design Methodology iv
not be appropriate. In lieu of a more sophisticated fracture mechanics analysis, the current
method should use consistent values of tensile strength and fracture toughness. An
example derivation of consistent values of tensile strength and material toughness is provided
in Appendix B.
Although not emphasized in the current LRC design methodology, the methodology is
only applicable for the design of a single independent cavern. The design methodology
should be used with caution when multiple caverns are involved that have overlapping
effects. In such cases, detailed design evaluations will be necessary using numerical
models.
The effect of seismic loads is not considered in the LRC design methodology. The potential
for seismic loads should be included. The effect of such loads would require detailed
design evaluations using numerical models.
The LRC design methodology should include a verification of its probabilistic approach
by evaluating the design for a set of credible lower-bound conditions using a detailed
numerical model. The minimum result of the model should be a barely acceptable design.
With the noted important exceptions, the review has found the implementation of the
LRC concept to be a carefully planned incremental design procedure. Although of considerable
proportions, the lined rock cavern size is not unprecedented. There is extensive
worldwide rock engineering experience in developing large complex rock caverns. By
following established principals, one should expect that stable, large, lined rock caverns
can be constructed in different lithology rocks of reasonable quality. During cavern operation,
the combination of shallow cavern depth and high gas pressure makes the LRC
concept unique in terms of the cavern loads, and the structural integrity of the steel liner
must be maintained for these loads. This requires a design methodology that not only
relies on the somewhat simple design analyses contained in the FLRC1 and FLRC2 models,
but also considers analyses that account for the discontinuum nature of rock masses
in detailed two- and three-dimensional numerical models as appropriate. By adopting a
careful design methodology that considers the detailed interaction of the rock mass and
cavern wall response, and a design implementation that is guided by physical observations
during cavern construction, one should expect to develop an LRC storage that will
operate successfully for a level of gas pressures as high as 25 MPa in a rock mass of reasonable
quality.