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Title: Permeameter studies of water flow through cement and clay borehole seals in granite, basalt and tuff

Abstract

Boreholes near a repository must be sealed to prevent rapid migration of radionuclide-contaminated water to the accessible environment. The objective of this research is to assess the performance of borehole seals under laboratory conditions, particularly with regard to varying stress fields. Flow through a sealed borehole is compared with flow through intact rock. Cement or bentonite seals have been tested in granite, basalt, and welded tuff. The main conclusion is that under laboratory conditions, existing commercial materials can form high quality seals. Triaxial stress changes about a borehole do not significantly affect seal performance if the rock is stiffer than the seal. Temperature but especially moisture variations (drying) significantly degrade the quality of cement seals. Performance partially recovers upon resaturation. A skillfully sealed borehole may be as impermeable as the host rock. Analysis of the influence of relative seal-rock permeabilities shows that a plug with permeability one order of magnitude greater than that of the rock results in a flow increase through the hole and surrounding rock of only 1-1/2 times compared to the undisturbed rock. Since a borehole is only a small part of the total rock mass, the total effect is even less pronounced. The simplest and mostmore » effective way to decrease flow through a rock-seal system is to increase the seal length, assuming it can be guaranteed that no dominant by-pass flowpath through the rock exists.« less

Authors:
;
Publication Date:
Research Org.:
Arizona Univ., Tucson, AZ (United States). Dept. of Mining and Geological Engineering
OSTI Identifier:
60628
Report Number(s):
NUREG/CR-4748
ON: TI87900100
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Oct 1986
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 05 NUCLEAR FUELS; CEMENTS; PERMEABILITY; CLAYS; SEALING MATERIALS; PERFORMANCE TESTING; BOREHOLES; GRANITES; BASALT; TUFF; STRESSES; FLOW RATE; EXPERIMENTAL DATA; Yucca Mountain Project

Citation Formats

South, D L, and Daemen, J J.K. Permeameter studies of water flow through cement and clay borehole seals in granite, basalt and tuff. United States: N. p., 1986. Web. doi:10.2172/60628.
South, D L, & Daemen, J J.K. Permeameter studies of water flow through cement and clay borehole seals in granite, basalt and tuff. United States. doi:10.2172/60628.
South, D L, and Daemen, J J.K. Wed . "Permeameter studies of water flow through cement and clay borehole seals in granite, basalt and tuff". United States. doi:10.2172/60628. https://www.osti.gov/servlets/purl/60628.
@article{osti_60628,
title = {Permeameter studies of water flow through cement and clay borehole seals in granite, basalt and tuff},
author = {South, D L and Daemen, J J.K.},
abstractNote = {Boreholes near a repository must be sealed to prevent rapid migration of radionuclide-contaminated water to the accessible environment. The objective of this research is to assess the performance of borehole seals under laboratory conditions, particularly with regard to varying stress fields. Flow through a sealed borehole is compared with flow through intact rock. Cement or bentonite seals have been tested in granite, basalt, and welded tuff. The main conclusion is that under laboratory conditions, existing commercial materials can form high quality seals. Triaxial stress changes about a borehole do not significantly affect seal performance if the rock is stiffer than the seal. Temperature but especially moisture variations (drying) significantly degrade the quality of cement seals. Performance partially recovers upon resaturation. A skillfully sealed borehole may be as impermeable as the host rock. Analysis of the influence of relative seal-rock permeabilities shows that a plug with permeability one order of magnitude greater than that of the rock results in a flow increase through the hole and surrounding rock of only 1-1/2 times compared to the undisturbed rock. Since a borehole is only a small part of the total rock mass, the total effect is even less pronounced. The simplest and most effective way to decrease flow through a rock-seal system is to increase the seal length, assuming it can be guaranteed that no dominant by-pass flowpath through the rock exists.},
doi = {10.2172/60628},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1986},
month = {10}
}