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|Title:||Expansive grout plug effects in restrained environments|
|Authors:||Sandia National Laboratories.|
Pace, Carl E.
Gulick, Charles W.
Finite element analysis
Finite element method
Hazardous waste storage
Cylindrical expansion theory
Expansion in pipes
Strains and stresses
Waste Isolation Pilot Plant
|Publisher:||Structures Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Technical report (U.S. Army Engineer Waterways Experiment Station) ; SL-85-9.|
Abstract: Technology needs to be developed which can assure the safe storage of hazardous waste material in underground cavities. Both analytical-techniques and experimental methods will be used in the development of this technology. For instance, finite-element analysis can be used to determine stresses and deformations in the plugging environment. Experimental methods can be used to determine parameters (under the proper environmental conditions) such as the properties of the material which forms the cavity, the properties of the plugging material, the relation of pressure and restraint of the plugging material, and the durability of both the host material and the plugging material. A large portion of this report is devoted to the pressure-versus-restraint relation of the plugging material. This relation can be determined by using steel pipes to provide known restraints on the plugging material as it expands. The pressure-versus-restraint of the expansive material can be determined from pressures obtained from the fluid pressure calibration of the pipes and from later measurements of strains on the pipes due to the presence of the expansive material inside the pipes. The pressure-versus-restraint relation as demonstrated in tests of BCT-1-FF grout in pipes under conditions of insignificant temperature effects is included only as an illustration of the analysis procedure. In later checking it was found that the data acquisition system used in testing BCT-1-FF probably had baseline or initial voltage changes. After several days, the drift in baseline voltage could have caused the test data to be inaccurate. A new instrumentation system has been implemented to eliminate this problem. It was found that temperatures between 85°F and 110°F will produce optimum expansion of the BCT-1-FF grout (this was determined by testing the BCT-1-FF grout in glass jars). This can vary somewhat with setting time and strength gain of an expansive mixture. This report also contains a section which illustrates how average pressures created by grout bar tests can be correlated with the pressures produced in cylindrical containers. It is recommended that a range of expansive characteristics be determined for effective stressing and sealing in practical borehole plugging situations. The best expansive material should be determined for these environments, and the causes of extraordinary variations in the· expansion of material from the same batch should be determined. The phasing of strength gain and expansive product development should be studied in relation to plug expansion and durability. It is also recommended that appropriate computer programs be linked together with instructions for a finite-element solution which can iterate to obtain equal strains at the plug-rock interface from the pressure-versus-restraint relation and the finite-element solution, and thus obtain stress fields in any env!ronment. Stress in physical situations may affect index properties such as permeability, compressive and tensile strengths, durability, etc., reflected by test results which are determined for unstressed specimens. For example, it has been established that stress promotes deterioration of concrete in a freezing and thawing environment. It is suggested that tests be conducted to determine whether realistic stress conditions affect short- and long-term properties which are used in evaluating the safety of borehole plugging situations. NOTE: This file is large. Allow your browser several minutes to open the file.
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