Databank

POSIVA Report 1996-9

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Name:

Characterization of the Excavation Disturbance Caused by Boring of the Experimental Full Scale Deposition Holes in the Research Tunnel at Olkiluoto

Writer:

Jorma Autio

Language:

English

Page count:

128

ISBN:

951-652-008-1; 1239-3096

Summary:

Working report: CHARACTERIZATION OF THE EXCAVATION DISTURBANCE CAUSED BY BORING OF
THE EXPERIMENTAL FULL SCALE DEPOSITION HOLES IN THE RESEARCH TUNNEL
AT OLKILUOTO



Three holes the size of deposition holes were bored in the Research Tunnel using a novel full-face
boring technique. During the boring test procedures were carried out in order to determine the
effect of changes in operating parameters on the performance of the boring machine and the
quality of the hole. Evaluation of the quality of the hole included studies of the geometry of the
holes, measurements of surface roughness using a laser profilometer, rock mechanical
determinations and study of excavation disturbances in the zone adjacent to the surface of the
holes using two novel methods, the He-gas method and the 14C-polymethylmethacrylate (14C-
PMMA) method. It was found that there is a distinct disturbed zone adjacent to the surface of the
full scale deposition holes which can be divided into three different zones. The zones are as
follows: a crushed zone penetrating to a depth of about 3 mm from the surface, a fractured zone
extending to a depth of 6 -10 mm from the crushed zone and a microfractured zone extending to a
depth of 15 - 31 mm from the fractured zone. The porosity of the rock in the disturbed zone
measured using the 14C-PMMA method was clearly greater than the porosity of undisturbed rock
to a depth of about 11 mm. The values of permeability and effective diffusion coefficient in the
disturbed zone measured in a direction perpendicular to the disturbed surface were found to be
approximately one order of magnitude larger than those of undisturbed rock. The degree of
disturbance was found to be greater where higher levels of thrust had been employed during the
boring process. The results obtained also suggest that the disturbance caused by using 4- and 5-
row cutters in the cutter head is more pronounced than the disturbance caused when using 5- and
6-row cutters.

Avainsanat - Keywords
Excavation disturbance, boring of deposition holes, characterization, He-method, 14C-PMMA-method
CHARACTERIZATION OF THE EXCAVATION DISTURBANCE CAUSED BY BORING OF
THE EXPERIMENTAL FULL SCALE DEPOSITION HOLES IN THE RESEARCH TUNNEL
AT OLKILUOTO



Three holes the size of deposition holes were bored in the Research Tunnel using a novel full-face
boring technique. During the boring test procedures were carried out in order to determine the
effect of changes in operating parameters on the performance of the boring machine and the
quality of the hole. Evaluation of the quality of the hole included studies of the geometry of the
holes, measurements of surface roughness using a laser profilometer, rock mechanical
determinations and study of excavation disturbances in the zone adjacent to the surface of the
holes using two novel methods, the He-gas method and the 14C-polymethylmethacrylate (14C-
PMMA) method. It was found that there is a distinct disturbed zone adjacent to the surface of the
full scale deposition holes which can be divided into three different zones. The zones are as
follows: a crushed zone penetrating to a depth of about 3 mm from the surface, a fractured zone
extending to a depth of 6 -10 mm from the crushed zone and a microfractured zone extending to a
depth of 15 - 31 mm from the fractured zone. The porosity of the rock in the disturbed zone
measured using the 14C-PMMA method was clearly greater than the porosity of undisturbed rock
to a depth of about 11 mm. The values of permeability and effective diffusion coefficient in the
disturbed zone measured in a direction perpendicular to the disturbed surface were found to be
approximately one order of magnitude larger than those of undisturbed rock. The degree of
disturbance was found to be greater where higher levels of thrust had been employed during the
boring process. The results obtained also suggest that the disturbance caused by using 4- and 5-
row cutters in the cutter head is more pronounced than the disturbance caused when using 5- and
6-row cutters.

Avainsanat - Keywords
Excavation disturbance, boring of deposition holes, characterization, He-method, 14C-PMMA-method

Keywords:

Excavation disturbance; boring of deposition holes; characterization; He-method; 14C-PMMA-method

File(s):

Characterization of the Excavation Disturbance Caused by Boring of the Experimental Full Scale Deposition Holes in the Research Tunnel at Olkiluoto (pdf) (10.3 MB)


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