Permeability Of Clay Research Articles

Determination of diffusion and sorption parameters of thin confined clay layers by direct fitting of through-diffusion flux

Diffusion in compacted clays is often studied in sandwich-like arrangements where the clay is confined by porous filter plates in order to control its swelling. In some clays (for example, Na-montmorillonite) equilibrated with dilute electrolyte solutions, the fluxes of cationic radiotracers can be quite high due to cation-exchange reactions. Accordingly, the diffusion resistance of clay layers can become comparable with or even smaller than the diffusion resistance of porous filters (such layers are called “thin” in this study). In view of the typical uncertainties (ca. 20%) of diffusion permeability of porous filters reported in the literature, the diffusion resistance of clay layers cannot be reliably determined from the steady-state diffusion permeability of the filter–clay–filter “sandwich” in this case. In this study, it is shown that, rather unexpectedly, information on the diffusion permeability of “thin” clay layers can be obtained from the time dependence of diffusant flux into the outlet compartment because at very short times, there is a characteristic flux delay that does not occur in the limiting case of infinitely large diffusion permeability of clay. The flux behavior at longer times is controlled by the diffusion permeability of the filters, which makes possible its determination directly from through-diffusion data and makes superfluous independent diffusion experiments with filters. This approach has been validated via theoretical interpretation of literature data on the diffusion of 22Na radiotracers through confined compacted montmorillonite equilibrated with 0.01 M NaClO 4 solution. The filter and clay properties estimated in this way are in good agreement with the literature data.

Silica sol for rock grouting: Laboratory testing of strength, fracture behaviour and hydraulic conductivity

A recently introduced non-cementitious grout silica sol is a refined product of colloidal silica, where the particle sizes have been reduced to between 5 and 100 nm. Laboratory tests were performed to determine the behaviour of silica sol as a permeation grout in hard rock. The tests have involved methods such as fall-cone, unconfined compression, triaxial, and oedometer tests. Samples were tested at different time intervals and in different storage environments. Results showed that the initial strength of silica sol, a few kPa, increases over time. Silica sol has a ductile behaviour during the first few days and then becomes elastic–plastic. Its hydraulic conductivity ranges from 10 −10 to 10 −11 m/s. When immersed in water, silica sol hardens and a thin layer of weaker strength is formed at the surface. However, this layer only extends a couple of millimetres into the sample; beyond that the silica sol is not affected, rendering breakdown by erosion a negligible risk. The conclusions are: (1) the strength obtained in silica sol after hardening is sufficient to withstand most grouting conditions; (2) when sufficiently confined, silica sol is able to withstand loading and unloading cycles; (3) a pH environment of around 11 does not appreciably change the strength of the silica sol; (4) silica sol is a material with low risk of failure under blasting vibrations; and (5) due to its low hydraulic conductivity, silica sol can be compared to low permeable clays.

Kati Atik Depolama Alanlarindaki Taban Kil Şiltelerinin Geçirimliliklerine NaCl Tuzunun Etkisi

Effect of NaCl Salt on the Permeability of Base Clay Liners in Solid Waste Disposal Landfills Because of its low permeability, liners constructed from high plasticity clays are the main material used in solid waste disposal landfills. It is exposed there to various chemical, biological and physical events, and these clay liners are affected by the resulting leachate. For this reason, when attempting to define the geotechnical characteristics of clays, the use of distilled water or tap water is far from being representative of the in-situ conditions. In this study, laboratory permeability tests were conducted on two different CL-classes and one CH-class clay using NaCl solutions representing leachate. Evaluation of the experimental results indicated that the permeability of CH-class clay increased with increasing NaCl concentrations; however, NaCl concentrations had no discernible effect on the permeability of CL-class clays.

An investigation of groundwater condition in Agbede by Geelectrical resistivity method.

Vertical soundings (VES) for the purpose of drilling groundwater boreholes for the inhabitants were conducted in Agbede to determine: the depth to the aquifer (Ajali Formation which consists of porous and permeable coarse sandstones); the thickness of overlying aquiclude (Imo Shale which consists of non porous/ permeable thick clays) and to locate where the small lenticular sands within the Imo Shale called perched aquifer exists. Perched aquifers are hydraulically separated, are relatively small, and they occur above the water table when there is an impermeable layer of rock (aquiclude) above the main aquifer. The VES curves of the area were qualitatively interpreted and the result showed an ascent at the first decade (dry top soil), a decent at the second decade (Imo Shale) and with the right most segment ascending int6o the third decade which is an indication of the presence of the Ajali Formation below the Imo Shale. The geoelectric section from the from the VES revealed that the Ajali Formation could not be encountered even at a depth of 494.03m, indicating that the clay is as thick as 500m. Also perched aquifer could be encountered between the depths of 52.76-55.43m with thicknesses 9.89-10.86m but not in all locations. Journal of the Nigerian Association of Mathematical Physics Vol. 10 2006: pp. 71-76

Role of Diffusion in Chemical Oxidation of PCE in a Dual Permeability System

The effect of in situ chemical oxidation (ISCO) with permanganate (MnO4-) on tetrachloroethene (PCE) in a dual permeability system consisting of low permeability clay with high permeability sand lenses was investigated by two-dimensional laboratory experiments. The experiments imitate a field remediation at a former dry cleaning facility in Denmark. Results from laboratory experiments and field observations both show that after an application of MnO4- in the sand layer, the diffusion rate into the matrix is decreased due to reaction with PCE and the natural oxidant demand (NOD) related to the clayey till. A narrow but very efficient reaction zone is created in the clayey till. Initiallythe zone developed rapidlyfollowed by a slower expansion with time. PCE will counter diffuse into the reaction zone, where it will be degraded as long as MnO4- is present. A mass balance for the laboratory experiment revealed that the reaction between MnO4- and the clayey till was responsible for up to 90% of the total MnO4- consumption. Based on laboratory experiments, the high MnO4- consumption from reaction with clayey till appears to have been the limiting factor for the oxidation of PCE at the field site and is thus impairing the efficiency of ISCO as a remedy.

Crack initiation in clay observed in beam bending

Tensile cracking in clay is an important phenomenon that affects the strength and permeability of clays in many facilities, such as dams, embankments and landfill liners, as well as being a precursor to slope failures in the natural terrain. This study investigates the stress–strain criteria for cracking in clays by performing four-point bending tests on consolidated kaolin clay beams. Load-controlled and strain-controlled tests were performed on clay beams with varying initial suction to understand the stress–strain criteria for crack initiation in clay. At no stage was the negative pore pressure permitted to exceed the air entry value of the clay, so the clay remained saturated throughout. Strains in the clay were obtained by particle image velocimetry analysis of digital images of the clay beam, and suction measurements were obtained from pore pressure and tension transducers installed within the clay beams. Results from this investigation showed that the threshold tensile strain to cracking in kaolin clay decreased from about 4% at an initial mean effective stress of 15 kPa to about 1·5% at an initial mean effective stress of 100 kPa. The extreme fibre stress at failure of the clay beams indicated an effective tensile strength that was a fraction, dropping from 0·27 to 0·11 of the preconsolidation pressure as the overconsolidation ratio increased from about 2 to about 20. Alternatively, the tensile strength could be regarded as 0·45 ± 0·15 of the geometric mean of the preconsolidation pressure in the plane of shear and the initial mean effective stress. Most significantly, evidence is presented of a new understanding of cracking in clays. Cracks were seen to open either as pure tension cracks at zero minor principal effective stress, or as mixed-mode shear-tension cracks when an effective stress path reaches the Hvorslev criterion of brittle shear rupture, but only if the minor total stress is also tensile.

Engineering Properties of Fibrous Peats

This state-of-the-art paper presents an interpretation of the permeability, compressibility, and shear strength of fibrous peats using data from laboratory tests on undisturbed block samples of two fibrous peats, as well as extensive laboratory and field data from the literature on fibrous peat deposits. Engineering properties of fibrous peats are significantly different from those of most inorganic soils. However, the same fundamental mechanisms and factors determine behavior of both inorganic soils and fibrous peats. Fibrous peat deposits possess very high initial permeability, typically 1,000 times the initial permeability of soft clay and silt deposits. Upon compression, the permeability of fibrous peats decreases dramatically, with a ratio of permeability change index to in situ void ratio equal to 0.25, as compared to 0.50 for soft clay and silt deposits. Fibrous peats display extreme compressibility to the increase in effective vertical stress, with compression index values right after preconsolidation pressure 5 to 20 times the corresponding compressibility of typical soft clay and silt deposits. Among geotechnical materials, fibrous peats display the highest ratios of secondary compression index to compression index, in the range of 0.05 to 0.07. The values of coefficient of earth pressure at rest for normally consolidated young fibrous peat deposits are in the range of 0.30 to 0.35, as compared to 0.45 to 0.65 for inorganic soils. The values of friction angle from triaxial compression tests for fibrous peats are in the range of 40 to 60°, as compared to less than 35° for soft clay and silt compositions. For fibrous peats, the ratios of undrained shear strength in compression to preconsolidation pressure are usually in the range of 0.50 to 0.75, as compared to 0.32 for soft clay and silt deposits. For surficial fibrous peat deposits the ratio of vane shear strength to preconsolidation pressure is near 1.0, as compared to 0.12 to 0.35 for inorganic soft clay and silt deposits. For fibrous peats, the ratio of undrained Young's modulus to undrained shear strength is in the range of 20 to 80.

High-Strengthening of Cement-Treated Clay by Mechanical Dehydration

A technique called the cement-mixing and mechanical dehydration method (CMD) as one of recycling techniques for soft clay slurry is developed. In order to evaluate the effectiveness of the CMD for increasing the strength of soft clay, a series of unconfined compression tests and several durability tests were performed together with the literature review of unconfined compressive strength in cement-treated soils. Moreover, a series of constant strain rate consolidation tests were also performed to evaluate the effects of cement content and dehydration speed on the permeability of cement-treated clay. The following conclusions are obtained: 1) Literature review and theoretical considerations on the shear strength of cement-treated soils show that an additional treatment for the purpose of increasing the density of cement-treated specimen is effective for increasing the shear strength of cement-treated soil. 2) The mechanical dehydration of soft clay with high pressure is accelerated by cement mixing, where the coefficient of consolidation of cement-treated clay increases as the cement content increases. 3) The high-strength specimen having the unconfined compressive strength of more than 20 MPa can be created from soft clay treated by the CMD with the cement content of over 20% and the dehydration pressure of 20 MPa.

Evaluation of air permeability in layered unsaturated materials

Field estimation of air permeability is important in the design and operation of soil-vapor extraction systems. Previous models have examined airflow in homogenous soils, incorporating leakage through a low-permeability cap either as a correction to the airflow equation or as a boundary condition. The dual leakage model solution developed here improves upon the previous efforts by adding a leaky lower boundary condition, allowing for the examination of airflow in heterogeneous layered soils. The dual leakage model is applied to the evaluation of pump tests at a pilot soil-vapor extraction system at the Savannah River Site in South Carolina. A thick, low-permeability, stiff clay layer divides the stratigraphy at the site into two units for evaluation. A modified version of the previous model, using the water table as the impermeable lower boundary, is used to evaluate the permeability of the low-permeability stiff clay layer (3.2 × 10 − 10 cm 2) and permeable sand (7.2 × 10 − 7 cm 2) beneath it. The stiff clay permeability estimate is used in the evaluation of the shallow unit. Permeability estimates of the shallow sand (3.8 × 10 − 7 cm 2) and kaolin cap (1.5 × 10 − 9 cm 2) were obtained with the dual leakage model. The shallow unit was evaluated using the previous model for comparison. The effects of anisotropy were investigated with a series of model simulations based on the shallow unit solution. The anisotropy sensitivity analysis suggests that increased anisotropy ratio or decreased axial permeability has a significant impact on the velocity profile at the lower boundary, especially at high values of the anisotropy ratio. This result may increase estimates of SVE removal rates for contaminants located at the interface of the lower boundary, typical of chlorinated solvent contamination.

Modeling of concentration polarization layer evolution and breakthrough concentrations in dead-end hyperfiltration

An explicit determination of concentration correlations and auxiliary parameters for solutions may be paramount in assessing the geometry of concentration polarization layer (CPL) during dead-end hyperfiltration and transport of ions through low permeability clays. Different models have been proposed for hindered transient transport of water and ions. Most of these models depend on solute permeability, solute diffusivity, and reflection coefficient of the membrane. Some models can predict various parameters for simple ionic molecules well but few of these can be immediately extended to organo macromolecules without special modifications. A model that estimates effluent concentrations for simple molecules and macromolecules like ionic azo dyes prior to the gelation period on homoionic membranes is proposed. The proposed model depends on evolution of the CPL of whose evolution can also be estimated from Karman–Pohlhausen and film model methods. Sensitivity analyses indicated relative dependence of this model on the diffusion coefficient.

Helium gas permeability of montmorillonite/epoxy nanocomposites

Abstract Helium gas permeability of silicate clay (montmorillonite) particles/epoxy nanocomposites was examined. The incorporation of increasing amounts of montmorillonite particles reduced the helium gas permeability. Based on Fick’s law, gas permeation behavior of the nanocomposite was evaluated. With the increase of montmorillonite loading, gas diffusivity decreased, while gas solubility increased. Helium diffusion behavior is in agreement to the numerical results based on the Hatta–Taya–Eshelby theory. It has been revealed that dispersion of nanoscale platelets in polymer is effective in improving gas barrier property.

Practical Model of Frost Heave in Clay

Freezing behavior of clay differs from that of silt. This difference stems primarily from the low permeability or hydraulic conductivity of clay, and the higher water content of saturated clay. Freezing effects include simultaneous heave and consolidation. Six small physical model columns of clay were frozen: one at 1g; and five on a centrifuge at various scales and with corresponding accelerations, to bring self-weight stresses into similarity with a full scale column of clay 4m in height. The experimental results demonstrated the importance of replicating the prototype stress conditions in a model. They demonstrated the importance of local water content on development of heave in clay, and the relative insensitivity of heave to location of the phreatic surface. Low permeability caused the clay to behave essentially as a closed system with regard to water flow. A simple analytical model was developed to explain observed soil response. Further research is recommended to provide more guidance in selecting input parameters.

Experimental study of the permeability of clays from the potential sites for acid effluent storage

The protection of the underground water layer in storage of industrial waste (acid effluent) is accomplished using clays that are essential for reducing the hydraulic conductivity of natural clay liners in landfill sites. This work describes the experimental study of permeability and the characterisation of clays of the three following sites in Tunisia: Sebkhat El Malah-El Mkhacherma, Jebel Haidoudi and Zemlet El Beidha. In the laboratory, we first studied the permeability of the three clays with fresh water and with acid lixiviate (pH between 2 and 3) containing wastes. We concluded that the first site had the lowest permeability of 6.25 10 −11 m/s and a neutral pH for the recovered solution, due to the existence of carbonate in the clay. We already know that a high percentage of carbonate makes the plate alkaline; favouring all fixation modes. In a second step, mineralogical DRX study of clay of the same site (Sebkhat El Malah-El Mkhacherma) reveals significant amounts of palygorskite and the kaolinite which are strongly resistant to acid attack. Moreover, based on results of the other techniques of characterisation such as the infrared spectroscopy and the specific measurement of surface BET, we confirm that the (Sebkhat El Malah-El Mkhacherma) site is the most suitable for the storage of these acid effluent wastes.

Chlorine transfer out of a very low permeability clay sequence (Paris Basin, France): 35Cl and 37Cl evidence

The marine Callovo-Oxfordian clay formation is found at a depth around 410m in the eastern part of the Paris Basin (France). It is a very low permeability formation investigated by the French agency for nuclear waste management (ANDRA) to study the feasibility of a radioactive waste disposal. Examining hydrogeological and geochemical characteristics of the clay sequence may test confinement properties of this formation. This study uses chlorine isotopes to investigate long-term transport processes which may carry chemical elements out of the clay layer to the surrounding rocks. Detailed chlorine concentration and δ 37Cl depth profiles are examined using pore waters and aquifer waters sampled in the clay formation and its surrounding aquifers (the Dogger at the bottom and the Oxfordian/Kimmeridgian/Tithonian unit at the top). They are discussed in terms of chlorine budget and hydrogeological processes. Clay pore waters and aquifer waters show strong chlorine concentration depletion (<3000 mg/L) relative to the original marine interstitial water (∼19000 mg/L). This probably results from an early dilution by meteoric water in limestones (as also indicated by oxygen and hydrogen isotopes). A steep Cl-concentration gradient from the Dogger at ∼500m in depth (∼2500 mg/L) to the Oxfordian/Kimmeridgian/Tithonian aquifer near the surface (≈ 10 mg/L) is associated to a ‘v-shaped’ profile of the δ 37Cl values. Modelling Cl transport shows that a hydrodynamic dispersion process explains Cl concentration and δ 37Cl profiles in Oxfordian Limestone. This process implies a mean upward flux of chloride in the 2.6 10 −8–8.2 10 −8 mole/m 2/yr range from the clay formation towards upper limestones where a westward advective flow disperses the chloride. The modelling and knowledge of underground water transfer suggest a maximum effective Cl-hydrodynamic vertical dispersion coefficient (= vertical Cl-transport coefficient) of ∼7.6 10 −10 m 2/s. Chlorine transfer through the Callovo-Oxfordian clay, since deposition 160My ago, can be mainly described by the interplay of an early dilution and a later hydrodynamic dispersion event which has apparently erased most of the isotopic effects of diagenetic events (such as early diffusion, ion filtration etc.).

Naturally occurring arsenic: Mobilization at a landfill in Maine and implications for remediation

Elevated levels of dissolved arsenic (∼300 μg L −1) have been detected beneath and in groundwater plumes extending away from a closed landfill in southern Maine. This study sought to determine the source of arsenic to the aquifer, the processes responsible for arsenic mobilization, and to evaluate the effectiveness of remediation efforts that have occurred at this site. The As appears to originate in the natural (glacial) aquifer solids, which contain ∼5 mg kg −1 As on a dry weight basis. This conclusion is supported by the relatively uniform distribution of As in sediment samples, results of laboratory batch incubation experiments, and comparisons with groundwaters in nearby wetlands, which also have high levels of dissolved As that do not appear to originate within the landfill. The As is mobilized in the subsurface by strongly reducing conditions beneath the landfill and in nearby wetlands. In the aquifer beneath the landfill, the average oxidation–reduction potential (ORP) is −95 mV (Eh + 105 mV), and these reducing conditions were primarily induced by landfill leachate. Remediation efforts at this site have included installation of a low permeability clay cap; groundwater extraction, oxidation, and re-injection; and subsurface oxidation by injection of magnesium peroxide. The natural source of arsenic within the aquifer solids, coupled with widespread reducing conditions, has severely limited the effectiveness of these interventions on groundwater arsenic concentrations.

Evaluation of a thermal criterion for an engineered barrier system

The retention curve of French FoCa compacted clay has been determined at 20, 50 and 80 °C. A saline saturated solution has been used to control the suction. The temperature, up to 80 °C, has no influence on the e( P c) curve. On the other hand, the water content and the liquid saturation degree are lower at 50 or 80 °C than at 20 °C. A model is proposed to take into account the influence of the temperature, in the framework of Biot's theory. A method to determine the liquid permeability of an unsaturated porous media is proposed. It is based on an analytical solution and on an experimental survey of the transient phase of desorption. This method has been applied to the compacted FoCa clay, at 20 °C. It is easy to implement and efficient. The permeability of FoCa clay has been determined for a large range of suctions.

Enhanced Electrokinetic Removal of Phenanthrene from Clay Soil by Periodic Electric Potential Application

Electrokinetically enhanced in-situ flushing using surfactants has the potential to remove polycyclic aromatic hydrocarbons (PAHs) from low permeability clay soils; however, previous research has shown that the applied electric potential produces complex physical, chemical, and electrochemical changes within clay soils that affect mass transfer and overall efficiency. This article presents the results of a laboratory investigation conducted to determine the contaminant mass removal by using a periodic voltage application. The periodic voltage effects were evaluated by performing four different bench-scale electrokinetic tests with the voltage gradient applied continuously or periodically, under relatively low voltage (1.0 VDC/cm) and high anode buffering (0.1 M NaOH) as well as high voltage (2.0 VDC/cm) and low anode buffering (0.01 M NaOH) conditions. For all the tests, kaolin soil was used as a representative clay soil and it was spiked with phenanthrene, a representative PAH, with a target concentration of 500 mg/kg. A nonionic polyoxyethylene surfactant, Igepal CA 720, was used as the flushing solution in all the tests. The voltage was applied according to a cycle of five days of continuous application followed by two days of “down time,” when the voltage was not applied. The results of these experiments show that considerable contaminant removal can be achieved by employing a high, 2.0 VDC/cm, voltage gradient along with a periodic mode of voltage application. The increased removal was attributed to increased phenanthrene solubilization and mass transfer due to the reduced flow of the bulk solution during the down time as well as to the pulsed electroosmotic flow that improved flushing action.

Effects of diagenetic processes on seismic velocity anisotropy in near-surface sandstone and carbonate rocks

The effects of diagenetic processes on velocity anisotropy in Ferron sandstone and Ellenburger carbonate core samples are investigated using petrophysical/petrological and P-wave velocity ( V p) data at room pressure and ambient (air dry) saturation. The V p data are measured in both vertical ( V p v) and horizontal ( V p h) directions (parallel and perpendicular to the axes of the cores, respectively), using a 125-kHz sonic probe. The petrophysical/petrological properties for the Ferron sandstone are bulk porosity, fluid permeability and volume fractions of quartz, clay, feldspar and calcite; for the Ellenburger carbonate, they are bulk porosity, vertical permeability, horizontal permeability, maximum permeability, grain density and bulk density. In the Ferron sandstone samples, the V p h values are higher (∼8.5%) than the V p v values, which is attributed to laminated bedding or alignment of grain orientation. Correlations between V p anisotropy and minerals that represent diagenetic processes are clearly demonstrated in the Ferron sandstone. Anisotropy decreases with decreasing feldspar, increasing calcite and increasing clay. This correlation suggests that calcite cementation and pore-filling kaolinite reduce velocity anisotropy of the Ferron sandstone by reduction of the net grain alignment or preferred pore orientations. The heterogeneity of the Ellenburger carbonate caused by multiple karsting and burials does not provide observable correlations between the velocity anisotropy and petrophysical/petrographic properties. In the Ellenburger carbonate, V p v values are mostly higher (∼7.9%) than the V p h values and are likely to be related to near-vertically aligned regional fractures. The orientation and amount of velocity anisotropy and of permeability is scale dependent when fractures are present. Seismic anisotropy is closely related to subsurface lithology, rock fabric and texture, and to its diagenetic history. Consequently, analysis of seismic anisotropy provides an important tool for reservoir characterization and environmental and engineering applications.

Radioactive Marker Measurements in Heterogeneous Reservoirs: Numerical Study

A numerical study is performed to simulate the vertical deformation of a depth interval representing a marker spacing (10.5 m) located in a deep heterogeneous sedimentary reservoir. Realistic lithostratigraphic sequences typical of the Northern Adriatic basin are used. A number of scenarios are addressed consistent with the available data. In particular two basic geologic scenarios at the marker scale are simulated, one where sands prevail within the marker spacing (SD), and another where thin sandy and clayey layers alternate (CL). The sensitivity of the marker response is investigated in relation to clay and sand permeability and compressibility contrast, Biot’s coefficient, and respective position of monitoring and fluid pumping wells. The modeling results show that rock may indeed expand above and below depleted layers. Depending on the marker position the expansion may partially offset the compaction, especially in the CL scenario with a very low permeable clay. To obtain a representative field compaction the markers should span a depth interval made mostly by sand and entirely depleted, and should be installed in a test hole far from producing wells. Compressibility contrast and the Biot coefficient play a secondary role. Very critical measurements are provided by two markers which incorporate a thin (≈1 m) depleted level overlain and underlain by almost impermeable clay layers.

Effects of diagenetic processes on seismic velocity anisotropy in near-surface sandstone and carbonate rocks

The effects of diagenetic processes on velocity anisotropy in Ferron sandstone and Ellenburger carbonate core samples are investigated using petrophysical/petrological and P-wave velocity ( V p ) data at room pressure and ambient (air dry) saturation. The V p data are measured in both vertical ( V p v ) and horizontal ( V p h ) directions (parallel and perpendicular to the axes of the cores, respectively), using a 125-kHz sonic probe. The petrophysical/petrological properties for the Ferron sandstone are bulk porosity, fluid permeability and volume fractions of quartz, clay, feldspar and calcite ; for the Ellenburger carbonate, they are bulk porosity, vertical permeability, horizontal permeability, maximum permeability, grain density and bulk density. In the Ferron sandstone samples, the V p h values are higher (∼8.5%) than the V p v values, which is attributed to laminated bedding or alignment of grain orientation. Correlations between V p anisotropy and minerals that represent diagenetic processes are clearly demonstrated in the Ferron sandstone. Anisotropy decreases with decreasing feldspar, increasing calcite and increasing clay. This correlation suggests that calcite cementation and pore-filling kaolinite reduce velocity anisotropy of the Ferron sandstone by reduction of the net grain alignment or preferred pore orientations. The heterogeneity of the Ellenburger carbonate caused by multiple karsting and burials does not provide observable correlations between the velocity anisotropy and petrophysical/petrographic properties. In the Ellenburger carbonate, V p v values are mostly higher (∼7.9%) than the V p h values and are likely to be related to near-vertically aligned regional fractures. The orientation and amount of velocity anisotropy and of permeability is scale dependent when fractures are present. Seismic anisotropy is closely related to subsurface lithology , rock fabric and texture, and to its diagenetic history. Consequently, analysis of seismic anisotropy provides an important tool for reservoir characterization and environmental and engineering applications.