Estimation of deformation and stiffness of fractures close to tunnels using data from single-hole hydraulic testing and grouting
Artikel i vetenskaplig tidskrift, 2010

Sealing of tunnel sin fractured rocks is commonly performed by pre- or post-excavation grouting. The grouting boreholes are frequently drilled close to the tunnel wall, an area where rock stresses can be low and fractures can more easily open up during grout pressurization. In this paper we suggest that data from hydraulic testing and grouting can be used to identify grout-induced fracture opening, to estimate fracture stiffness of such fractures, and to evaluate its impact on the grout performance. A conceptual model and a method are presented for estimating fracture stiffness. The method is demonstrated using grouting data from four pre-excavation grouting boreholes at a shallow tunnel (50 m) in Nygard, Sweden, and two post-excavation grouting boreholes at a deep tunnel (450 m) in Aspo HRL, Sweden. The estimated stiffness of intersecting fractures for the boreholes at the shallow Nygard tunnel are low (2-5 GPa/m) and in agreement with literature data from field experiments at other fractured rock sites. Higher stifness was obtained for the deeper tunnel boreholes at Aspo which is reasonable considering that generally higher rock stresses are expected at greater depths. Our method of identifying and evaluating the properties and impact of deforming fractures might be most applicable when grouting takes place in boreholes adjacent to the tunnel wall, where local stresses might be low and where deforming (opening) fractures may take most of the grout. (C) 2010 Elsevier Ltd. All rights reserved.

coupled hydromechanical behavior

Hydraulic testing

Fractured rock

Hydromechanical coupling

pressure

field

Fracture normalstiffness

Stress

Grouting

hard-rock

Författare

Åsa Fransson

Chalmers, Bygg- och miljöteknik, Geologi och geoteknik

C.-F. Tsang

Imperial College London

Lawrence Berkeley National Laboratory

J. Rutqvist

Lawrence Berkeley National Laboratory

Gunnar Gustafson

Chalmers, Bygg- och miljöteknik, Geologi och geoteknik

International Journal of Rock Mechanics and Minings Sciences

1365-1609 (ISSN)

Vol. 47 6 887-893

Ämneskategorier

Geovetenskap och miljövetenskap

DOI

10.1016/j.ijrmms.2010.05.007