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Semi-discrete procedure for dynamic response analysis of saturated soils
25A
Dynamic properties
the finite element method coupled with a fast probability integration technique. Results are presented for the idealised linear elastodynamic case, but extension to more realistic situations is possible.
See also: 921203 921188 Reflection and transmission of elastic waves at a loosely bonded interface between an elastic solid and liquid-saturated porous solid Vahisth, A K; Sharma, M D; Gogna, M L Geophys J V105, N3, June 1991, P601-617
The presence of a liquid in a porous skeleton way weaken the strength of welded contact at the surface. Reflection and transmission of a plane periodic wave incident at such a loosely bonded interface between a saturated porous solid and an elastic solid is analysed. The solids are considered contiguous, the interface maintaining continuity of stress and allowing a finite amount of slip. Analytical expressions for energy ratios are determined in closed form. Attenuation of energy for different degrees of bonding with angle of incidence is shown graphically. Practical applications are considered. 921189 Field measurements of azimuthal anisotropy: first 60 meters, San Francisco Bay area, CA, and estimation of the horizontal stresses ratio from Vsl/Vs2 Lynn, H B Geophysics V56, N6, June 1991, P822-832
In situ elastic and anelastic properties (Vp, Vs, Q) were measured in the weathered surficial zone at two sites. Shear wave azimuthal anisotropy of at least 5% was found. Ratio of the horizontal stresses estimated from shear wave polarisation is considered too large to be supported by the unconsolidated weathered zone. Fabric anisotropy introduced by the depositional agent and stress-aligned fluid filled microcracks or pores are probable contributors to the anisotropy. 921190 Semi-discrete procedure for dynamic response analysis of saturated soils Chohan, H S; Sandhu, R S; Wolfe, W E lnt J Num Anal Afeth Geomech VI5. NT, July 1991, P471496 Blot's equations for wave propagation in porous, fluid saturated soils arc discretized spatially using the finite element method and the equations of motion solved in Laplace transform space using an cigenvcctor representation. The solution is then inverted to the space-time domain term by term. Errors in calculated response are solely due to the spatial approximation. Numerical examples are presented for one-dimensional wave propagation in a linear elastic medium and in a fluid saturated elastic soil layer. In the absence of exact solutions, this procedure can act as a benchmark for assessing time integration schemes and appropriate spatial requirements. 921191 Probabilistic analysis of an impulsively loaded deep-based structure. Application brief Harren, S V; Fossum, A F lnt J Num Anal Ateth Geomech VI5. NT, July 1991, P513526
Propagation of ground level disturbance towards a deeply buried structure depends on the material properties of the geological strata, which generally show considerable scatter, as well as any uncertainties about the ground level blast. Stress wave loading of such a structure is analysed probabilistically using
921192 Anisotropy of X ray absorption in a slate: effects on the fabric and March Strain determination Chen, R J J Geophys Res II96, NB4, April 1991, P6099-6105
X ray absorption of a sample of Dorothea slate from North Wales has been found to be anisotropic, related to preferred orientation of phyllosilicates. A correction equation has been formulated and is applied in re-estimation of principal strains. The linear absorption coefficient is replaced by what is probably a second rank tensor quantity. Transmission pole figure X ray data, corrected for anisotropy of X ray absorption, give values of principal strains very similar to those measured on ellipsoidal strain indicators, but different from empirically corrected results. 921193 Fluidization technique for mine backfill with slurry of high density Chen, L J g i n Sci Technol V12, N3, May 1991, P325-332
High density slurry fill is widely used in underground mines. A laboratory and field program to develop an economic method of preparation of such slurries is described. Tailings of different sizes were allowed to settle in a silo, then a water jet under pressure used to suspend the solid particles in a slurry such that they are able to move freely. Velocity of the water jet, dimensions of the fluidifying area, and discharge method are the primary factors affecting slurry density. Solids contents of 75-80% by weight are possible using this technique. 921194 Ductility criterion for evaluating remedial measures to increase liquefaction resistance of sands. Technical note Yoshimi, Y; Tokimatsu, K Soils Found V31, NI, March 1991, P162-168
The application of ductility as a criterion to evaluate the reliability of sand compaction piles and gravel drains to prevent excessive deformation of saturated sand deposits as a result of liquefaction following an earthquake greater than the design value is studied. The vibratory sand compaction pile is considered viable because the compacted sand shows ductile behaviour. Gravel drains are suitable in sands of moderately high initial liquefaction resistance, but must be installed at close spacings in order to be effective in loose sands. 921195 Liquefaction of fluid saturated rocks due to explosion-induced stress waves Dey T N; Brown, J A Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18-20 June 1990 P889-896. Publ Rotterdam: A A Balkema, 1990
Shock induced liquefaction of saturated rocks due to the passage of large amplitude stress waves has been studied numerically and experimentally. The mathematical model is evaluated for both small and large deformations and any initial saturation. Fitting the model to dry gas gun experiments on limestone samples allows reasonable prediction for nearly saturated experiments. Liquefaction occurs when pore pressure exceeds mean stress, during the unloading portion of the
© 1992 Pergamon Press plc. Reproduction not permitted
Dynamic properties
the finite element method coupled with a fast probability integration technique. Results are presented for the idealised linear elastodynamic case, but extension to more realistic situations is possible.
See also: 921203 921188 Reflection and transmission of elastic waves at a loosely bonded interface between an elastic solid and liquid-saturated porous solid Vahisth, A K; Sharma, M D; Gogna, M L Geophys J V105, N3, June 1991, P601-617
The presence of a liquid in a porous skeleton way weaken the strength of welded contact at the surface. Reflection and transmission of a plane periodic wave incident at such a loosely bonded interface between a saturated porous solid and an elastic solid is analysed. The solids are considered contiguous, the interface maintaining continuity of stress and allowing a finite amount of slip. Analytical expressions for energy ratios are determined in closed form. Attenuation of energy for different degrees of bonding with angle of incidence is shown graphically. Practical applications are considered. 921189 Field measurements of azimuthal anisotropy: first 60 meters, San Francisco Bay area, CA, and estimation of the horizontal stresses ratio from Vsl/Vs2 Lynn, H B Geophysics V56, N6, June 1991, P822-832
In situ elastic and anelastic properties (Vp, Vs, Q) were measured in the weathered surficial zone at two sites. Shear wave azimuthal anisotropy of at least 5% was found. Ratio of the horizontal stresses estimated from shear wave polarisation is considered too large to be supported by the unconsolidated weathered zone. Fabric anisotropy introduced by the depositional agent and stress-aligned fluid filled microcracks or pores are probable contributors to the anisotropy. 921190 Semi-discrete procedure for dynamic response analysis of saturated soils Chohan, H S; Sandhu, R S; Wolfe, W E lnt J Num Anal Afeth Geomech VI5. NT, July 1991, P471496 Blot's equations for wave propagation in porous, fluid saturated soils arc discretized spatially using the finite element method and the equations of motion solved in Laplace transform space using an cigenvcctor representation. The solution is then inverted to the space-time domain term by term. Errors in calculated response are solely due to the spatial approximation. Numerical examples are presented for one-dimensional wave propagation in a linear elastic medium and in a fluid saturated elastic soil layer. In the absence of exact solutions, this procedure can act as a benchmark for assessing time integration schemes and appropriate spatial requirements. 921191 Probabilistic analysis of an impulsively loaded deep-based structure. Application brief Harren, S V; Fossum, A F lnt J Num Anal Ateth Geomech VI5. NT, July 1991, P513526
Propagation of ground level disturbance towards a deeply buried structure depends on the material properties of the geological strata, which generally show considerable scatter, as well as any uncertainties about the ground level blast. Stress wave loading of such a structure is analysed probabilistically using
921192 Anisotropy of X ray absorption in a slate: effects on the fabric and March Strain determination Chen, R J J Geophys Res II96, NB4, April 1991, P6099-6105
X ray absorption of a sample of Dorothea slate from North Wales has been found to be anisotropic, related to preferred orientation of phyllosilicates. A correction equation has been formulated and is applied in re-estimation of principal strains. The linear absorption coefficient is replaced by what is probably a second rank tensor quantity. Transmission pole figure X ray data, corrected for anisotropy of X ray absorption, give values of principal strains very similar to those measured on ellipsoidal strain indicators, but different from empirically corrected results. 921193 Fluidization technique for mine backfill with slurry of high density Chen, L J g i n Sci Technol V12, N3, May 1991, P325-332
High density slurry fill is widely used in underground mines. A laboratory and field program to develop an economic method of preparation of such slurries is described. Tailings of different sizes were allowed to settle in a silo, then a water jet under pressure used to suspend the solid particles in a slurry such that they are able to move freely. Velocity of the water jet, dimensions of the fluidifying area, and discharge method are the primary factors affecting slurry density. Solids contents of 75-80% by weight are possible using this technique. 921194 Ductility criterion for evaluating remedial measures to increase liquefaction resistance of sands. Technical note Yoshimi, Y; Tokimatsu, K Soils Found V31, NI, March 1991, P162-168
The application of ductility as a criterion to evaluate the reliability of sand compaction piles and gravel drains to prevent excessive deformation of saturated sand deposits as a result of liquefaction following an earthquake greater than the design value is studied. The vibratory sand compaction pile is considered viable because the compacted sand shows ductile behaviour. Gravel drains are suitable in sands of moderately high initial liquefaction resistance, but must be installed at close spacings in order to be effective in loose sands. 921195 Liquefaction of fluid saturated rocks due to explosion-induced stress waves Dey T N; Brown, J A Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18-20 June 1990 P889-896. Publ Rotterdam: A A Balkema, 1990
Shock induced liquefaction of saturated rocks due to the passage of large amplitude stress waves has been studied numerically and experimentally. The mathematical model is evaluated for both small and large deformations and any initial saturation. Fitting the model to dry gas gun experiments on limestone samples allows reasonable prediction for nearly saturated experiments. Liquefaction occurs when pore pressure exceeds mean stress, during the unloading portion of the
© 1992 Pergamon Press plc. Reproduction not permitted