Svl. Barrett et Dr. Mccreath, SHOTCRETE SUPPORT DESIGN IN BLOCKY GROUND - TOWARDS A DETERMINISTIC APPROACH, Tunnelling and underground space technology, 10(1), 1995, pp. 79-89
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Categorie Soggetti
Engineering, Civil","Construcion & Building Technology
The precise mechanisms by which shotcrete acts to stabilize the ground
around a tunnel are not well understood and are the focus of ongoing
research and discussion. Consequently design of shotcrete support is s
till more of an art than a science, with the majority of designs based
on past experiences in similar settings, on empirical recommendations
or on monitoring and modification, during construction. In an attempt
to provide an analytical alternative, and to gain some insight concer
ning the mechanisms which control shotcrete failure in blocky ground,
four deterministic design models are presented which illustrate shotcr
ete's effectiveness at supporting structurally defined blocks and wedg
es, thereby avoiding progressive loosening and destabilization of the
rock mass around an opening. These models may also be used to verify o
r refine design recommendations which have been based initially on emp
irical guidelines, and to give an indication of the approximate factor
of safety. Examples of typical design charts are given. Results of an
alyses based on these models show that failure of shotcrete is general
ly a two-step process, governed initially by loss of adhesion to the r
ock, followed by flexural failure. These results indicate that while a
dhesion is of critical importance in maximizing the peak ground suppor
t capacity of the shotcrete, flexural strength and toughness play a cr
itical role in the post-peak region, once adhesion is lost.