To start with, an analytical layer-element (i.e., a symmetric stiffness matrix), which describes the relationship between the generalized displacements and the stress levels of a layer subjected to non-axisymmetric loading, is exactly derived in the transformed domain by the application of a Laplace–Hankel transform with respect to variables t and r, a Fourier expansion with respect to variable θ, and a Laplace transform and its inversion with respect to variable z, based on the governing equations of Biot’s consolidation of multi-layered saturated poroelastic materials with anisotropic permeability. The analytical layer-element experiences considerable improvement in computation efficiency and stability, since it only contains negative exponential functions in its elements. In addition, a global stiffness matrix for multi-layered saturated poroelastic media is obtained by assembling the interrelated layer-elements based on the continuity conditions between adjacent layers. By introducing the boundary conditions and solving the global stiffness matrix, the solutions in the Laplace–Hankel transformed domain are obtained, and the final solutions can be recovered by a numerical inversion of the Laplace–Hankel transform. Finally, numerical examples are presented to verify the theory and to study the effect of the property of anisotropic permeability on vertical displacements and excess pore pressure. The calculation results show that the property of anisotropic permeability has a great influence on the process of consolidation. 相似文献
The dynamic analysis of saturated poroelastic media is significant in many areas such as seismology, earthquake engineering, soil mechanics and geophysics. In 1956, Biot[1—3] first developed the dynamic equations for saturated poroelastic media. He also discussed systematically the propagation of waves in such two-phase media and further predicted the existence of the slow longitudinal wave. Biots work is consummate while the two formal parameters he introduced are difficult to measure. In t… 相似文献
To better understand the role of groundwater-level changes on rock-slope deformation and damage, a carbonate rock slope (30 m×30 m×15 m) was extensively instrumented for mesoscale hydraulic and mechanical measurements during water-level changes. The slope is naturally drained by a spring that can be artificially closed or opened by a water gate. In this study, a 2-h slope-dewatering experiment was analyzed. Changes in fluid pressure and deformation were simultaneously monitored, both at discontinuities and in the intact rock, using short-base extensometers and pressure gauges as well as tiltmeters fixed at the slope surface. Field data were analyzed with different coupled hydromechanical (HM) codes (ROCMAS, FLAC3D, and UDEC).
Field data indicate that, in the faults, a 40 kPa pressure fall occurs in 2 min and induces a 0.5–31×10−6 m normal closure. Pressure fall is slower in the bedding-planes, lasting 120 min, with no normal deformation. No pressure change or deformation is observed in the intact rock. The slope surface displays a complex tilt towards the interior of the slope, with magnitudes ranging from 0.6 to 15×10−6 rad.
Close agreement with model for both slope surface and internal measurements is obtained when a high variability in slope-element properties is introduced into the models, with normal stiffnesses of kn_faults=10−3×kn_bedding-planes and permeabilities of kh_faults=103×kh_bedding-planes. A nonlinear correlation between hydraulic and mechanical discontinuity properties is proposed and related to discontinuity damage. A parametric study shows that 90% of slope deformation depends on HM effects in a few highly permeable and highly deformable discontinuities located in the basal, saturated part of the slope while the remaining 10% is related to elasto-plastic deformations in the low-permeability discontinuities induced by complex stress/strain transfers from the high-permeability zones. The periodicity and magnitude of free water-surface movements cause 10–20% variations in those local stress/strain accumulations related to the contrasting HM behavior for high- and low-permeability elements of the slope. Finally, surface-tilt monitoring coupled with internal localized pressure/deformation measurements appears to be a promising method for characterizing the HM properties and behavior of a slope, and for detecting its progressive destabilization. 相似文献
The paper presents an analytical solution for the vertical dynamic interaction analysis of a poroelastic soil layer and an embedded pile with the consideration of pile-soil radial deformations. The soil is treated a three-dimensional porous continuum and described by the Boer’s poroelastic model, while the pile is treated as a two-dimensional rod with both radial and vertical deformations of which the equation of motion is derived by the Hamilton’s variational principle. Without the introduction of potential functions, first take the volumetric strain of soil skeleton and pore fluid pressure as intermediate variables to deal with the equations of motion for the soil and then use the separation of variables to solve the equations of motion for the soil and the pile. By imposing the boundary and continuity conditions of the pile-soil system, the dynamic impedance in frequency domain and the velocity response in time domain of the pile top are obtained. The present solution is then verified by comparing with the corresponding finite element model computation results and the existing solutions. The effects of the pile-soil parameters on the dynamic characteristic of the pile-soil system are also analyzed. Some significant conclusions are drawn, which can provide useful reference for related engineering practice. 相似文献
This paper discusses a mathematical and numerical modeling approach for identification of an unknown optimal loading time signal of a wave source, atop the ground surface, that can maximize the relative wave motion of a single-phase pore fluid within fluid-saturated porous permeable (poroelastic) rock formations, surrounded by non-permeable semi-infinite elastic solid rock formations, in a one-dimensional setting. The motivation stems from a set of field observations, following seismic events and vibrational tests, suggesting that shaking an oil reservoir is likely to improve oil production rates. This maximization problem is cast into an inverse-source problem, seeking an optimal loading signal that minimizes an objective functional – the reciprocal of kinetic energy in terms of relative pore-fluid wave motion within target poroelastic layers. We use the finite element method to obtain the solution of the governing wave physics of a multi-layered system, where the wave equations for the target poroelastic layers and the elastic wave equation for the surrounding non-permeable layers are coupled with each other. We use a partial-differential-equation-constrained-optimization framework (a state-adjoint-control problem approach) to tackle the minimization problem. The numerical results show that the numerical optimizer recovers optimal loading signals, whose dominant frequencies correspond to amplification frequencies, which can also be obtained by a frequency sweep, leading to larger amplitudes of relative pore-fluid wave motion within the target hydrocarbon formation than other signals. 相似文献