Clay Zone Research Articles

Surface geophysical investigations of landslide at the Wiri area in southeastern Korea

A geophysical survey was undertaken at Wiri area of the Andong in southeastern Korea to delineate subsurface structure and to detect the fault zone, which affected the 1997 mountain–hill subsidence and subsequent road heaving initiated by the intense rainfall. Electrical resistivity methods of dipole–dipole array profiling and Schlumberger array sounding and seismic methods of refraction and reflection profiling were used to map a clay zone, which was regarded as the major factor for the landslide. The clay zone was identified in electrical resistivity and seismic sections as having low electrical resistivity (<100 Ωm) and low seismic velocity (<400 m/s), respectively. The clay zone detected by using geophysical methods is well correlated with its distribution from the trench and drill-core data. The results of the electrical and seismic surveys showed that slope subsidence was associated with the sliding of saturated clay along a fault plane trending NNW–SSE and dipping 10°–20° SW. However, the road heaving was caused by the slope movement of the saturated clay along a sub-vertical NNE-trending fault.

Airborne EM mapping of rockslides and tunneling hazards

We have investigated potential rockslides in Western Norway using a time- and cost-efficient airborne electromagnetic (AEM) survey approach. The study area comprises phyllite, a low-grade metamorphic rock type that tends to be reworked to clay in disturbed zones. Mapping these electrically conductive clay zones was the aim of the AEM survey. Based on indications that precipitation drives the reported rockslide movements, the local municipality and regional hydroelectricity company are evaluating the option of draining the unstable area to a nearby hydropower reservoir using a drainage tunnel of more than 10 km. We conducted the AEM mapping survey to locate the sliding planes and to investigate the tunnel corridor for areas with potential tunneling hazards. Spatially constrained inversion of the data set (250 km) reveals extended conductive zones interpreted as sliding planes and/or gneiss/phyllite interface. Detailed follow-up of these initial results is planned with targeted percussion drilling and ground resistivity surveys.

Mineralogical characteristics of the footwall clay zone of the Minamishiraoi barite deposit, Hokkaido

Mineralogical characteristics of the footwall clay zone of the Minamishiraoi barite deposit, Hokkaido

Intensive kaolinization during a lateritic weathering event in South-West Spain

Abstract This study documents the mineralogical and geochemical record of a lateritic weathering event during the Pliocene in South-west Spain. The paleoweathering profile derived from arkosic sands and comprises a white sandy clayey saprolite, a red mottled clay zone overlain by a thick soft layer, and a ferruginous pisolitic hardcap partially dismantled by erosive processes. Kaolinite, quartz and degraded K-feldspars are the major minerals forming the saprolite, along with Al-goethite (mottled zone) as well as gibbsite and boehmite (soft layer), while the pisolitic duricrust is essentially composed of quartz grains embedded in a matrix of Fe oxy-hydroxides (hematite, goethite, and/or maghemite). Besides quartz, the phases most resistant to alteration were a variety of heavy minerals (mostly titanium oxides) that are present as minor impurities in the residual kaolin deposit. The dominant weathering process of kaolinization is geochemically characterized by striking losses of Na, K, Ca, Mg, and large-ion lithophile elements (Rb, Sr, Cs, Ba, and U), because of the almost entirely breakdown of primary minerals (mainly feldspars and 2:1 phyllosilicates). The Ti-normalized distribution patterns of trace elements also reveals remobilization and redistribution processes within the profile, involving high field strength elements classically regarded as immobile, like Zr and Hf. Iron showed a contrasted behaviour, with depletion in the saprolite zone and strong accumulation in the pisolitic duricrust. Various transition trace metals (Cr, V, Sc, Th, Nb, and Ta) remained relatively immobile during the weathering, and were residually concentrated in the duricrust linked to the Fe oxy-hydroxides. The geochemical and mineralogical evolution of the paleosol studied is consistent with a laterization process evolved under humid subtropical conditions, and driven by morphodynamic and hydrodynamic factors (gently sloping coastal area with fluctuating water table and rapid water percolation) favourable for the development of a deeply kaolinized paleosurface.

Reappraisal of the Activity of Clays. Activity Chart

The proposed activity chart, which aims to classify soils (<425 μm) using the Atterberg limits, differs from the plasticity chart recently proposed by the author because the inorganic soils with platey clay minerals are classified (in addition to clay percentage) on the basis of their activity rather than on the degree of plasticity as a function of the liquid limit value, currently used by the standards. This is because soils that have the same liquid limit value may have very different characteristics because of both the amount and type of clay minerals contained in the soils. On the activity chart, the silt and the clay zones are subdivided (by two straight lines) in three new groups (low activity, medium activity and high activity) making it possible to classify inorganic soils with platey clay minerals (or their fraction) <425 μm on the basis of the amount and type of clay minerals they contain. The activity chart adapted to predict residual shear behaviour of cohesive soils is also shown. Finally, the distinction between coarse-grained soils and fine-grained soils based on their percentage of clay (<2 μm), might be useful in characterizing and predicting soils' engineering behaviour.

Casing-Collapse Strength Reduction Under Lateral Loads From Yielding Shales in the Daqing Oilfield

Summary Casing failure has been found in nearly 20% of production wells in the Daqing oil field after 45 years of oil-production history. Plastic failure of casing strings has been recognized in the zones of yielding shales overlying reservoir pay zones in the field. This type of casing failure is one of the most costly problems in the field. No research has been conducted to study the resistance of the casing string to the lateral loads from the yielding shales. This paper offers results from such research. Assuming a lateral load uniformly distributed along a casing section from a clay zone clamped between an upper and a lower sandstone zone, a mechanistic model was developed in this study. Results of the model indicate that the resistance of casing string to the lateral loads drops sharply in the early stage of development of radial deformation. The resistance of the casing string to the lateral loads is not very sensitive to the longitudinal deformation. The remaining strength of the casing string also depends on properties of the casing string. A calculation example is illustrated in this paper. This work provides an analytical tool that can be used for optimizing casing programs against lateral loads from yielding-clay zones to minimize casing failure and field-operation cost.

Physical and finite element modeling of lateral stability of offshore skirted gravity structures subjected to iceberg impact load

Static stability mainly against sliding of a typical, relatively large skirted gravity structure was investigated using three-dimensional finite element modeling. The numerical model was validated against centrifuge test results. A specific set of dimensions was chosen to model a typical skirted gravity structure in a centrifuge with two types of foundation soils: uniform saturated sand and a clay zone sandwiched between two sand layers. Soil shear strength parameters used in the finite element models were estimated from in-flight cone penetration resistance measurements obtained in the centrifuge. Numerical parametric studies were conducted using the validated finite element model. The parameters included were the depth and strength of the clay zone and the inclination of external load. It is shown that a relatively simple three-dimensional finite element model was effective in providing information that would be needed to design such a critical and expensive offshore structure. Basic Mohr–Coulomb strength parameters and moduli based on cone penetration resistance measurements and published empirical correlations were appropriate in modeling the soils in the finite element simulations.

Sodic metasomatism in a dacite weathering profile in Pinxiang, Guangxi, China

The Pinxiang weathering profile is well developed on Early Triassic dacite lavas of the Baisi Formation. At the top of the profile is developed a red clay zone which is characterized mineralogically by kaolinite, iron oxide minerals, quartz, and a small amount of illite, montmorillonite and vermiculite. In going downwards the red clay zone gives way to a saprolite zone in which plagioclase pseudomorphs have been well preserved although replaced by kaolinite. Beneath the saprolite zone is the saprock zone characterized by less weathering for dacite. At the bottom of the weathering profile is the parent material, dacite, which is composed mainly of plagioclase, quartz, K-feldspar and biotite which have been largely altered into chlorite owing to submarine extrusion of dacite lavas. Some layers in the weathering profile show obvious sodium enrichment and potassium depletion relative to others. In the Al2O3-(CaO*+Na2O)-K2O triangular diagram, the weathering trends of these layers in the middle stage are remarkably deviated from normal ones. Both mineralogy and micro-morphology of these layers indicate such deviation resulted from sodic metasomatism of orthoclase.

Diagenetic effect on magnetic properties of marine core sediments from the southern Okhotsk Sea

Abstract It is well known that magnetic records of marine sediments are affected to a certain degree by early diagenesis, the extent and mode of which are controlled by depositional environments. In order to investigate variations in the effects of early diagenesis, we have analyzed 11 gravity cores estimated to be Holocene in age that constitute a depth transect off the southern coast of the Okhotsk Sea. The rock magnetic parameters have peaks produced by the presence of volcanic ashes, basaltic granules and/or relatively coarser-grained layers. The concentration-dependent parameters display characteristic trends of a rapid decrease within the homogeneous silty clay zone in the middle parts of the cores, assuming that the total amount of magnetic minerals decreases through early diagenesis at this interval. This decrease is found in all of the cores from the transect (from both near-shore and offshore sites). In near-shore sites where larger volumes of organic materials are supplied compared to offshore sites, the depth of the decrease in magnetic minerals is relatively shallow. These results imply that the presence of organic materials accelerates the pyritization through the bacterial reduction of ferric ion, thereby causing the decreases in magnetic minerals to become shallower.

Sequential tracer tests for determining water seepage paths in a large rockfill dam, Nakdong River basin, Korea

The rockfill dam of this study has a clay core, filter zone, and sandy gravel shell, and it is located in the Nakdong River basin in Korea. Filling the reservoir began in August 1994 and it was full by April 1998. When the reservoir level was approximately 150 m, three settlement holes were found in the dam crest. To determine possible seepage paths and potential damaged areas within the rockfill dam, 15 tracer tests were performed during two periods. During the two test periods, six and nine tracer tests were conducted when the average water levels of the reservoir were 145 m and 142 m, respectively. Rhodamine WT (RWT) and bromide ion were used as tracers. For each test, 1800 to 4000 L of tracer solution were injected into the riprap for about 5 h. The 15 injection points were uniformly distributed from the right to left sides of the embankment and the two tracers were injected alternately. Tracer concentrations were monitored at 26 observation wells, which were divided into four groups by their geographical positions: right side of the crest, left side of the crest, right side of the dam toe, and left side of the dam toe. For each tracer test, more than 30 water samples were taken during a period of 96 h at each observation well. Based the breakthrough curves obtained from the sequential tracer tests, it was inferred that the most probable seepage paths and potential damaged area were in the left side of the crest (tongue wing zone) and, to a lesser extent, in the right side of the dam abutment.

Clay minerals related to the hydrothermal activity of the Bouillante geothermal field (Guadeloupe)

The geothermal field of Bouillante (Guadeloupe, FWI) is a high-enthalpy hydrothermal system emplaced in submarine volcanoclastic formations (hyaloclastites, scarce lava flows) and subaerial formations (andesitic lava flows, pyroclastites, lahars) which belong to the Lesser Antilles arc. Three directional wells were drilled in 2001 to optimize the productivity of the geothermal field up to 15 MWe and to investigate the vertical distribution of clay alteration from the surface area down to a depth of 1000 m where temperatures exceed 250 °C. Special attention has been paid to the “clay signature” of the fractured zones which channel the present geothermal fluids. Three successive zones, dominated, respectively by dioctahedral smectite, illite and chlorite were identified at increasing depths. Alteration petrography indicates that these mineralogical clay zones result from the spatial superimposition of at least two successive alteration stages. The first one, assimilated to a propylitic alteration stage, affected all parts of the system and consisted of crystallization of trioctahedral phyllosilicates (chlorite or corrensite), Ca-silicates (heulandite-clinoptilolite, prehnite, pumpelleyite, wairakite and epidote), quartz and minor calcite in replacement of most of the primary minerals of the intersected volcanic or volcanoclastic formations. The later stage of alteration is related to the circulation of the present geothermal fluids and is assimilated to argillic or phyllic alteration. It consists of a more or less intense argillization which results from the crystallization of aluminous dioctahedral clay phases (smectite, illite ± I–S mixed layers, and accessory kaolinite) associated with quartz, calcite, hematite or pyrite. The permeable zones which channel most of the present geothermal fluids are fracture controlled and do not contain specific clay parageneses. However the illite ± I–S mixed layers minerals differ from those of the surroundings by specific properties including both crystal structure and texture. These specific properties (decrease in the expandable component of the illitic material, increase of the illite crystallinity) can be controlled by the nucleation/growth rates operating in zones of active flow regime. Being mainly a product of the earlier propylitic alteration stage, chlorites are much less informative on the fracture controlled permeable levels. However, the compositional variations of chlorites recorded within the shallower fractured zone suggest a significant change in fO 2 conditions related to early circulation of fluids along the major near west striking normal faults (Plateau fault).

The Callovo-Oxfordian argillites from the eastern Paris Basin: Magnetic data and petrofabrics

A set of regularly spaced specimens, made up of dark-coloured calcareous argillites, were collected from borehole-cores from the Early Callovian up to the Middle Oxfordian, in the eastern Paris Basin. These specimens have been studied for their magnetic susceptibility, natural and artificial remanence, and for their anisotropy of magnetic susceptibility. Compared with sulfate, carbonate and iron contents, these magnetic properties provide information on both the nature and the relative amounts of the constitutive minerals. To a first approximation, these data outline the main end-members of these argillites, namely ( i) carbonate-enriched and less susceptible, ( ii) clay-enriched and more susceptible, and ( iii) more remanent and partly due to the silt fraction. The middle of the Callovo-Oxfordian formation, called the maximum clay zone, is marked by the highest recorded susceptibility, mainly due to the paramagnetic iron-bearing clay minerals, and by a rather low remanence. The anisotropy of susceptibility provides information on the petrofabric of mostly the clay fraction. The fabric is highly planar, in agreement with the subhorizontal preferred orientation of the clay platelets, but the always present linear anisotropy of the argillites, although modest in strength, points to ∼north–south trending directions throughout most of the formation. These directions agree with the detrital fractions coming from the northern Rhineland, Bohemian and London–Brabant massifs. To cite this article: L. Esteban et al., C. R. Geoscience 338 (2006).

Comparison of performance of concrete barriers in a clayey geological medium

Cement based materials play an important role in the design and performance of future deep radioactive waste disposals. The type of materials selected for engineered barrier systems (EBS) is an important issue: protection of waste packages against corrosion and chemical degradation may be greatly enhanced by a proper choice and dimensioning. The long-term geochemical performance of two concrete types, CEM-I (pure Portland cement) and CEM-V (blended Portland, fly ash, blast furnace slag cement) was evaluated using reactive transport simulations of the interactions between the Callovo-Oxfordian mudrock (argillite) and concrete EBS over periods up to 10 6 years at 25 °C. Simulations have been run with cylindrical geometry using the modeling tool Hytec 3.5 (ENSMP/CIG). Diffusion of solutes in the porewater of the solid media was considered to be the dominant transport process. Different scenarios were studied, including the case of sulfate attack. Various assumptions on the transport properties of the EBS and the argillite medium have been considered and compared. The interactions between concrete, CEM-I or CEM-V, and mudrock are in both cases predicted to lead to a significant clogging in the mudrock, in the vicinity of the interface with the concrete EBS. However, the nature and extent of the EBS/mudrock interface transformations greatly differ for the two materials considered. CEM-V, due to lower diffusion coefficients, keeps longer internal high pH conditions which are favorable to the waste packages from a chemical point of view. In addition, simulations predict that CEM-V material should have a better resistance to sulfate attack than CEM-I based barriers. In the case of CEM-I, the altered clay zone has a greater extent (up to 1.3 m in 400,000 y) and the drop of porosity is mainly due to zeolites and reprecipitated illite, quartz and calcite. For CEM-V, the altered clay zone is much smaller (less than 0.2 m in 400,000 y) and secondary smectite and calcite precipitation are predicted to cause porosity reduction.

Application of an effective stress design method to concrete piles driven in Mexico City clay

Piled foundations are used widely in the lake clay zones of Mexico City, with “friction” piles being driven into soft diatomaceous clay deposits that show an extraordinary range of mechanical properties. The paper assesses the applicability of the Imperial College pile (ICP) design method to the concrete piles driven in these deposits. After the ICP methodology and Mexico City ground conditions are reviewed, an experimental study is reported of the key soil properties required for the ICP procedures: yield stress ratio, unit weight, interface friction angle (δ), sensitivity (St), and intrinsic properties. The new data are then applied to a specially assembled database of static pile load tests from different Mexico City clay locations, with allowance being made for site-specific details and local installation procedures. A quantitative assessment shows that the ICP methodology is free from significant bias and leads to more reliable estimates of static capacity than the total stress (α) design method routinely used in Mexico City.Key words: validation, database, static axial pile capacity, driven friction pile, effective stress design, silty clay.

Electrical Methods for Detection and Discrimination of Saline Groundwater in Clay-Rich Sediments in Northern Victoria

Conductivity surveys (Induced Polarization and Transient Electromagnetics) have been conducted on the southern bank of the Goulburn River, near Murchison, Victoria, to discriminate between clay zones and saline discharge streams. The combined surveys provide a consistent dataset and multiple conductive zones are delineated within the regolith. The ambiguity between salinity and clay content variations is resolved by means of the induced polarization parameters. In particular, normalised chargeability values are shown to highlight the location of clay lenses containing saline pore water.

Fault Structure Control on Fault Slip and Ground Motion during the 1999 Rupture of the Chelungpu Fault, Taiwan

The Chelungpu fault, Taiwan, ruptured in a Mw 7.6 earthquake on 21 September 1999, producing a 90-km-long surface rupture. Analysis of core from two holes drilled through the fault zone, combined with geologic mapping and detailed investigation from three outcrops, define the fault geometry and physical properties of the Chelungpu fault in its northern and southern regions. In the northern region the fault dips 45-60 east, parallel to bedding in both the hanging wall and footwall, and consists of a narrow (1-20 cm) core of dark gray, sheared clay gouge. The gouge is located at the base of a 30- to 50-m zone of increased fracture density confined asymmetrically to the hanging wall. Microstructural analysis of the fault gouge in- dicates the presence of extremely narrow clay zones (50-300 lm thick) that are interpreted as the fault rupture surfaces. Few shear indicators are observed outside of the fault gouge, implying that slip was localized within the gouge zone. Slip localization along a bed-parallel surface resulted in a narrow gouge zone that pro- duced less high-frequency ground motion and larger displacements (average 8 m) during the earthquake than in the southern region. Displacement in the southern region averaged only 2 m, but ground shaking consisted of large amounts of high- frequency ground motion. The fault in the southern region dips 20-30 at the surface and consists of a wide (20-70 m thick) zone of sheared, foliated shale with numerous gouge zones. These data demonstrate a potential correlation between fault structure (i.e., gouge width, geometry) and earthquake characteristics such as displacement and ground motion (i.e., acceleration).

Proposal for a new plasticity chart

This study investigates the consistency limits of the pure clay minerals kaolinite and montmorillonite, and their respective mixtures with fine silica sand in various proportions. Plotting the plasticity index data as a function of the liquid limit allows the zones where mixtures with the same clay contents fall to be defined. In particular, the line corresponding to 50% clay (designated as the 0·5C-line) makes it possible to distinguish the points that lie below the line, namely clay, from the points lying above the line in the silt zone. The clay zone includes inorganic soils with clay contents ≥50%, whereas the silt zone includes inorganic soils composed of silt and/or sand (2–425 μm) in percentages &gt;50%. A new plasticity chart, which aims to classify soils (&lt;425 μm) using the Atterberg limits, is defined herein. It differs from Casagrande's plasticity chart, especially in terms of its silt and clay zones, whose positions are reversed compared with Casagrande's chart. This can be explained by the fact that, contrary to what is commonly believed, in inorganic soils—liquid limits being equal—the plasticity index increases as the clay content decreases. Save only a few exceptions, the examples of inorganic soils plotted on the new plasticity chart lie above the 0·5C-line in the silt zone or below the line in the clay zone when their clay contents are less or greater than 50% respectively. On Casagrande's plasticity chart, the same soils lie above the A-line in the clay zone, regardless of their clay contents (9·7–100%). Only the kaolinite samples (relatively pure) lie below the A-line in the silt zone.

THE EFFECTS OF COLEMANITE DEPOSITS ON THE ARSENIC CONCENTRATIONS OF SOIL AND GROUND WATER IN IGDEKÖY-EMET, KÜTAHYA, TURKEY

The hydrochemical study of the area surrounding the Hisarcik (Emet-Kutahya) colemanite mine shows extremely high arsenic contamination in ground water between 0.07 to 7.754 mg L-1. This contamination in and around the Igdekoy village of Emet was caused by naturally occurring arsenic dissolution from a borate bearing clay zone due to the leaching of arsenic bearing minerals. The arsenic concentration in the ground water varies locally from spring to spring and is related to the mineralogical and geochemical compositions and lithofacies of the contaminant aquifer. The Neogene borate-bearing clay unit, which contains some arsenic minerals such as realgar (AsS) and orpiment (As2S3) observed in colemanite (Ca2B6O11⋅5H2O) nodules, is responsible for the arsenic contamination in ground waters in the study area. Soil geochemical analyses show unremarkable concentrations, varying from <0.01 to 7.11 mg kg-1.

Geostatistical prediction of clay percentage based on soil survey data

In precision farming fields may be divided into management zones according to the spatial variation in soil properties. Clay content is an important soil characteristic, because it is associated with other soil properties that are important in management. Soil survey data from 150 sampling sites taken from an area of 218 ha were used to predict the spatial variation of clay percentage geostatistically in an agricultural soil in Jokioinen, Finland. The exponential and spherical models with a nugget component were fitted to the experimental variogram. This indicated that the medium-range pattern could be modelled, but the short-range variation could not, due to sparsity of sample points at short distances. The effect of sampling density on the kriging error was evaluated using the random simulation method. Kriging with a spherical model produced a map with smooth variation in clay percentage. The standard error of kriging estimates decreased only slightly when the density of samples was increased. The predictions were divided into three classes based on the clay percentage. Areas with clay content below 30%, between 30% and 60% and over 60% belong to non-clay, clay and heavy clay zones, respectively. With additional information from the soil samples on the contents of nutrients and organic matter these areas can serve as agricultural management zones.;

Reservoir Description and Development of a Mature Oil Field

The Mishovdag oil field is located in the southwest of Baku, Azarbaijan. The sandstone reservoirs consisting of five middle Pliocene age Horizons I, II, III, IV, and XII provide 40% of total oil production from the Sirvan oil field region. The reservoir trap is an anticline, and its size is approximately 15 × 5 km. Since its discovery in 1956, 516 wells had been drilled and 198 of them are still producing from successive layers of sandstone formations. This study was conducted to describe Horizon I of Block-9, prepare input data for a modeling study and suggest development scenarios for this block. From this point of view, it was aimed to properly describe the reservoir properties with the use of core and, mainly, well log data. In this respect, these data set were evaluated to define the reservoir. According to field reports, seven producing layers were present in Horizon I of Block-9. From the results of further analysis on well logs, it was recognized that the reported seven layers were not continuous within Block-9 so, for modeling studies, these sandstone layers could be grouped under three main sand layers, namely, S1, S2, and S3, that were separated by two clay zones. The results of the modeling study showed that oil production was mainly from level S3 and level Sl was less swept by water injection. The oil saturation distribution at three levels at the end of 39 years of production indicated that there was still recoverable oil in levels S1 and S2. No free gas could be observed in any of the levels because the pressure maintenance provided by water injection caused free gas to redissolve in oil.