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Collaborating Authors
Results
Mechanical and Hydraulic Performance of Sludge-mixed Cement Borehole Plugs in Rock Salt
Tepnarong, P. (Suranaree University of Technology) | Deethouw, P. (Suranaree University of Technology)
Abstract The objective of this study is to experimentally assess the performance of sludge-mixed cement grouts for sealing boreholes in rock salt. The cement grout is prepared from the commercial grade Portland cement mixed with Bang Khen water treatment sludge, brine and chloride resistant agent. The results are used in the design of borehole seal in rock salt to minimize the brine circulation and potential leakage for the industrial waste repository. The rock salt specimens are prepared from the 54 mm diameter cores drilled from the Middle member of the Maha Sarakham formation. The results indicate that the viscosity of grout slurry tends to increase as the sludge-mixed cement (S:C) ratio increases. The permeability of the sludge-mixed cement grouting materials measured from the longitudinal flow test with constant head decreases with curing time at 7, 14, 21 and 28 days. The results indicate that when the curing time increases the intrinsic permeability (k) of cement grout decreases. The mixture with the S:C of 5:10 by weight gives the lowest permeability. The S:C mixtures have the mechanical and hydraulic properties equivalent to those of the commercial grade Portland cement mixtures which indicates that the sludge can be used as a substituted material to mix with cement for rock salt fracture grouting purpose. The compressive strength after 28 day curing times is 9.58±0.52 MPa. The highest compressive strength is from S:C = 5:10. The average tensile strength is 1.99±0.14 MPa. The highest bond strength is 7.49 MPa. When the curing increases. Similarities and discrepancies of the grouting performance in terms of mechanical and hydraulic properties are compared.
- North America > United States (0.69)
- Asia > Thailand > Maha Sarakham > Maha Sarakham (0.25)
- Energy > Oil & Gas > Upstream (1.00)
- Water & Waste Management > Water Management > Lifecycle > Treatment (0.35)
Laboratory Assessment of Fracture Permeability under Normal and Shear Stresses
Phueakphum, D. (Suranaree University of Technology) | Fuenkajorn, K. (Suranaree University of Technology)
Abstract Falling head flow tests have been performed to determine the hydraulic conductivity of tension-induced fractures while under normal and shear stresses for eight rock types. The joint roughness coefficients are determined and used to calculate the mechanical aperture. The shear stress is applied while the shear displacement and water head drop are monitored for every 0.5 mm interval of shear displacement. The fracture hydraulic conductivities decrease exponentially with increasing normal stresses. The physical and hydraulic apertures increase with shearing displacement, particularly under high normal stresses. The magnitudes of the fracture permeability under no shear and under peak shear stress are similar. For both peak and residual regions, the physical apertures are about 5 to 10 times greater than the hydraulic apertures. This is probably because the measured physical apertures do not consider the effect of fracture roughness that causes a longer flow path. The difference between the permeability under residual shear stress and that under peak stress becomes larger under higher normal stresses. The findings are useful to determine the rock mass permeability where the fractures are subject to changes of stress states induced by surface and underground excavations.
Verification of Some Rock Mass Strength Criteria Using Laboratory Test Models
Thaweeboon, S. (Suranaree University of Technology) | Fuenkajorn, K. (Suranaree University of Technology)
Abstract The objective of this study is to determine rock mass strength and deformability in the laboratory by simulating joints in sandstone specimens. The results are used to assess the predictive capability of rock mass strength criteria developed by Hoek-Brown, Ramamurthy-Arora, Yudhbir and Sheorey. Empirical criteria developed by Goodman, Yoshinaka and Yamabe and Ramamurthy criteria are used to predict the deformation modulus of rock mass. Triaxial compressive strength tests have been performed on cubical sandstone specimens with nominal dimensions of 60×60×60 mm and 80×80×80 mm.A true triaxial load frame is used to apply confining pressures up to 12 MPa. The joints are simulated by saw-cut surface. The compressive strengths and deformation modulus of rock specimens decrease exponentially with increasing joint frequency. Under the same joint frequency the deformation modulus tends to increase with confining pressure. When the major principal stress is normal to the joint planes the specimen strength is greatest and the deformation modulus is lowest. Hoek-Brown strength criterion can effectively describe the specimen strengths under all configurations. The m and s parameters decrease rapidly with increasing joint frequency and joint set number. Ramamurthy criterion can best describe the deformation modulus of rock specimens under all configurations.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.46)
- Energy > Oil & Gas > Upstream (0.48)
- Health & Medicine > Diagnostic Medicine > Lab Test (0.41)
Effects of Loading Rate on Strength and Deformability of Rock Salt Under 273-373 Kelvin
Sartkaew, S. (Suranaree University of Technology) | Fuenkajorn, K. (Suranaree University of Technology)
Abstract The objective of this study is to determine effects of loading rate on compressive strength and deformability of the Maha Sarakham salt under elevated temperatures. The effort is aimed at determining the safe maximum withdrawal rates for the compressed-air energy storage (CAES) in salt caverns. The constant axial stress rates range from 0.0001 to 0.1 MPa/s. The testing temperatures are maintained constant between 273and 373 Kelvin. The results indicate that the shear stress-strain curves monitored under various loading rates and temperatures show nonlinear relations, particularly under high temperatures. To incorporate the thermal and rate (time-dependent) effects into a strength criterion the distortional strain energy at dilation of the salt is calculated as a function of the mean strain energy density. Finite difference analyses (FLAC 4.0) are also performed to determine the stresses and strains at the boundaries of CAES caverns for various reduction rates of the internal pressures. The maximum stresses and strains obtained during retrieval period are used to calculate the strain energy density induced at the cavern boundaries. The results are compared against the criteria developed above, and hence the safe maximum withdrawal rate of the compressed-air can be determined.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Mineral > Halide > Halite (0.53)
Assessment of Pore Pressure Effect on Mechanical Properties of Low Porosity Rocks
Khamrat, S. (Suranaree University of Technology) | Fuenkajorn, K. (Suranaree University of Technology)
Abstract The objective of this study is to experimentally determine the effects of pore pressure on the compressive strengths and elasticity of three Thai decorating stones. An indirect approach for determining the pore pressure in low porosity rocks is presented. Rectangular rock specimens (50×50×100 mm) under dry and saturated conditions are axially loaded under different rates from 0.001 to 10 MPa/s using a polyaxial load frame. The confining pressures are maintained constant between 0 and 12 MPa. The saturated granite, marl and marble specimens have average water contents of 0.14%, 2.71% and 0.09%. Compressive shear failure is observed in specimens under slow loading rate while extension failure is found in specimens under high loading rate. The strengths of the saturated specimens are lower than those of the dry ones, particularly under the high confining pressures and loading rates. The strengths obtained from the dry testing are used to quantitatively isolate the loading rate effect from the saturated strengths, and hence the true effect of pore pressure can be revealed. The pore pressures notably reduce the compressive strength and elastic modulus, and slightly increase the Poisson's ratio of the rocks tested.
- North America > United States (0.68)
- Asia > Thailand (0.49)