Silty Clay Deposits Research Articles

Settlement predictions in the Anatolian Motorway, Turkey

The Anatolian Motorway through the Asarsuyu Valley passes across the landslides which have been extensively disturbed by past fault movements. The Asarsuyu Valley is the most important crossing of the motorway between Istanbul and Ankara route. Along the Asarsuyu Valley, about 7 km of the roadway is still under construction. In this study, the magnitude and the rate of the settlement over consolidated clays in lacustrine deposits within the Asarsuyu Valley were compared with each other. On the basis of field observations and laboratory test results, it was determined that the lacustrine deposits were eroded up to 15 m by the river in the valley bottom. As results of unloading and desiccation process, the clay layers are overconsolidated. Settlement calculations indicate that the amount of clay layers has caused the intolerable consolidation settlement under the concrete structures and motorway embankment. In this respect, preloading embankment on clay and silty clay deposits was projected and constructed. On the basis of evaluations, estimated values of settlement are lower than those realized. However, the predicted settlement quantities are found reliable and comparable to field measurements. On the other hand, significant differences were observed between calculated and measured rate of the settlement. The high rate of the settlement, which was measured during preloading, was caused by the viscoelastic strain due to the relatively high load and sandy pockets available in the clay layers, but was not detected by the drilling and the micro/macro texture of the clay layers.

Permeability evaluation and its implications for consolidation analysis of an Italian soft clay deposit

The present research concerns a comparative analysis of the possible methods for estimating soft silty clay permeability to be used in the analysis of consolidation. For this purpose the consolidation response of a thick and homogeneous, instrumented soft silty clay deposit, on which an embankment was constructed, is back-analyzed using the finite-element method. To model the consolidation process, permeability data are carefully determined both from laboratory and in situ piezocone tests. One-dimensional and triaxial permeability test data are compared with the results of piezocone dissipation tests, the latter interpreted using four different solutions. The effects of anisotropy on permeability characteristics influencing the consolidation rate are also discussed.Key words: consolidation, embankment, finite-element analyses, permeability, piezocone, soft silty clay.

Urban geology and environmental problems of Lahore City, Pakistan

The present study deals with the urban geology and environmental problems of the Lahore City in Pakistan. It is based on a set of the following thematic maps at 1:100, 000 scale: geology, urbanisation, engineering geology, land use, flood hazard, and aquifer drawdown depth. The major hazards of the Lahore metropolitan area are air pollution, water pollution, noise pollution, and deforestation, which are the result of rapid population growth as well as poor planning.
 The Lahore metropolitan area comprises the Early Pleistocene to Recent silty loess and silty clay deposits of the Ravi River. The foundation conditions of the Lahore metropolitan area are generally good. The city suffers from periodic floods during the monsoon season. The pavement and drains accelerate and increase the surface runoff and the peak flood. Unplanned groundwater development in the metropolis has caused a rapid lowering of the water table. Subsequently, the sand is dewatered and the water table has dropped to 7-13 m.

Effects of water quality on infiltration, runoff and interrill erosion processes during simulated rainfall

This paper discusses the effects of water quality on the hydrological and erosion response of non-saline, non-sodic soils during simulated rain experiments. It is well known that rain water quality affects the behaviour of saline soils. In particular, rain simulation experiments cannot be run using tap water if realistic values of infiltration rates and soil erosion are to be found. This paper reports on similar effects for non-saline, non-sodic soils. Two soils – a well-aggregated clay-rich soil developed on marine silty clay deposits and a soil developed on silt loam – were selected and subjected to a series of simulated rainstorms using demineralized water and tap water. The experiments were conducted in two different laboratories in order to obtain results independent of the tap water quality or the rainfall simulator characteristics. The results indicate that time-to-ponding is largely delayed by solute-rich water (tap water). When tap water is used, infiltration rates are significantly overestimated, i.e. by more than 100 per cent. Interrill erosion rates increase by a factor of 2·5–3 when demineralized water is used. The silty clay soil was more affected by the water quality than the silt loam soil, with respect to infiltration and runoff production. Regarding interrill erosion rates, the two tested soils were similarly affected by the water quality. Therefore, it can be concluded that rainfall simulation experiments with non-dispersive soils (e.g. non-saline, non-sodic) must also be conducted using water with very low electrical conductivity (i.e. less than 30–50 µS cm−1), close to that of distilled water. The use of tap water certainly hampers comparisons and the relative ranking of the hydrological and erosion response of different soils, while parameter values, such as final infiltration rate or time-to-ponding, cannot be extrapolated and extended to natural situations. Therefore, the majority of hydrological and erosion models and parameter values measured during rainfall simulations in the past should be used with caution for all types of soils. Copyright © 2001 John Wiley & Sons, Ltd.

00/02347 Estimation of reservoir parameter using a hybrid neural network

A new open-air Mousterian site was found in karst depression on hilly limestone terrain of central Israel at Nesher Ramla. The paper highlights the complex history of depositional, post-depositional and pedogenic processes that took place at the later phases of Mousterian site formation during the OSL age interval between ∼80 and ∼115 ka. The Upper sequence is divided into Unit I and Unit II, both comprising rather uniform calcareous, gravel-rich, silty clay deposits. Gravel largely consists of calcrete (Nari) and possibly some chalky limestone. Unit I is darker, partially decarbonated, magnetically enhanced, and shows microscopic features of shrink–swell process analogous to Vertisols. Mousterian artifacts, chunks of ochre and animal bones are scarce in this unit. Unit II has increased gravel, magnetic susceptibility values drop, and humus and carbonate content both increase. Mousterian artifact density significantly increases in the middle part of Unit II. Lithologic characteristics, thin sections and SEM/EDS all indicate that the Upper sequence originated from periodic erosion of loess-derived soils developed upon chalky hillslopes intermittent with more stable periods when hominins occupied the site. The proposed model relates the Upper sequence to heterogeneous anthropogenic pedosediments with high proportions of eroded soil materials and signs of in situ pedogenesis. Apart from singular mm-sized pyrogenic features, remnants of bedded combustion features in the Upper sequence are lacking, probably because of pedogenic and diagenetic alterations on the site.

Seismically triggered turbidites in small margin basins: Alfonso Basin, Western Gulf of California and Santa Monica Basin, California Borderland

Box cores and gravity cores collected in Santa Monica Basin, California Continental Borderland, and in Alfonso Basin, western Gulf of California, contain turbidites, some of which can be traced over much of the respective basin floors. In Santa Monica Basin, at least six of these basin-wide flows have been deposited over the past four to five centuries. In Alfonso Basin, 9–10 basin-wide turbidites have been deposited over the past few millenia. Both Santa Monica and Alfonso Basins have anoxic conditions over the deep basin floors, which inhibit bioturbation and preserve primary laminations. These deposits have been dated using the 210 Pb and AMS 14 C methods, and varve counting so it is therefore possible to date the turbidites. Those that were deposited during historic time can be matched with major floods or earthquakes in the region. In Santa Monica Basin, turbidity currents can be generated directly from decadal major flood discharges, or by centennial slope failures triggered by major earthquake shocks. The flood-generated turbidites are typically a fifth or less of the volume of the earthquake-generated turbidites. In Alfonso Basin, the tributary coastal canyon discharges are small and have a high proportion of coarse-grained sand, which is trapped on the shelves, and cannot directly supply turbidite volumes of basin-wide magnitude. Thus the turbidites seen in that basin floor are probably produced by slope failures of silty clay deposits which were seismically generated. The distribution of the dated turbidites, and a slip face in one box core from the landward slope, indicates a source on the landward depositional slope of the fault-bounded basin. Similar discontinuities of the same age have been reported on the eastern side of the Gulf in the Guaymas area. In ancient basins, the criteria that may distinguish seismo-turbidites are areal extent and volume where those factors can be estimated. Basin-wide turbidites are probably seismically triggered. If paleogeographic data are sufficient to delineate basin form, then major turbidite volumes can also be estimated. These can be compared to average annual sediment-accumulation rates based on basin volume divided by basin age, as a means of determining potential minimum magnitudes of flood-generated volumes.

Behavior of a fine-grained soil during the Loma Prieta earthquake

Results of an investigation into the behavior of a fine-grained clayey soil at Moss Landing during the 1989 Loma Prieta earthquake are presented. A deposit of this soil underlies portions of the Moss Landing Marine Laboratory that experienced up to 1.3 m of lateral spreading deformations during this magnitude 7 earthquake. Silty clay from the deposit erupted to the surface in a "soil boil" characteristic of liquefaction, during and immediately after the earthquake. A sample from the silty clay boil had a liquid limit of 38, a plasticity index of 17, and a <5 µm fraction of 24%, and thus would be considered nonliquefiable according to commonly used criteria. Analysis of cyclic triaxial test data suggests that portions of the silty clay deposit likely developed high residual excess pore pressures (ru,r approx 80-90%) and significant shear strains during the earthquake and thus likely contributed to the observed lateral deformations. The field and laboratory data show that commonly used criteria for identifying "liquefiable" clayey soils should be applied with caution and should not be indiscriminately viewed as a substitute for detailed laboratory and in situ testing of low plasticity fine-grained soils.Key words: liquefaction, cyclic loading, silt, clay, earthquake, case history.

Behavior of a fine-grained soil during the Loma Prieta earthquake

Results of an investigation into the behavior of a fine-grained clayey soil at Moss Landing during the 1989 Loma Prieta earthquake are presented. A deposit of this soil underlies portions of the Moss Landing Marine Laboratory that experienced up to 1.3 m of lateral spreading deformations during this magnitude 7 earthquake. Silty clay from the deposit erupted to the surface in a "soil boil" characteristic of liquefaction, during and immediately after the earthquake. A sample from the silty clay boil had a liquid limit of 38, a plasticity index of 17, and a <5 µm fraction of 24%, and thus would be considered nonliquefiable according to commonly used criteria. Analysis of cyclic triaxial test data suggests that portions of the silty clay deposit likely developed high residual excess pore pressures (ru,r approx 80-90%) and significant shear strains during the earthquake and thus likely contributed to the observed lateral deformations. The field and laboratory data show that commonly used criteria for identifying "liquefiable" clayey soils should be applied with caution and should not be indiscriminately viewed as a substitute for detailed laboratory and in situ testing of low plasticity fine-grained soils.Key words: liquefaction, cyclic loading, silt, clay, earthquake, case history.

Limitations on infiltration and reinjection of treated groundwater to remove trace amounts of pesticides in groundwater and soil

AbstractInfiltration and reinjection of treated groundwater have been used to increase the recovery of pesticide‐related constituents at a pesticide formulation plant that produces consumer pesticide products. The stratigraphy at the site consists of silty and sandy clay deposits overlying a shallow silt, sand, and gravel aquifer. The groundwater and soils in two areas in the northwest portion of the property have been identified as being significantly affected by pesticide and pesticide‐related compounds.An integrated system of soil removal, recovery wells, injection wells, an infiltration gallery, and a cut‐off wall was selected as the best remedial alternative. Groundwater modeling, column tests, biological jar tests, and a pilot test demonstrated the feasibility of the system. The affected groundwater is treated to drinking‐water quality by a system of filtering and carbon adsorption. Approximately 75 percent of the treated water is reinjected or allowed to infiltrate through the vadose zone, and the remainder is discharged to the local sewer system. Initially, the system was effective in removing the dissolved, suspended, and weakly adsorbed constituents. Subsequently, the recovery rate of the chemical constituents became dependent on chemical and physical processes related to the presence of residual amounts of dense, nonaqueous phase liquids and the clay content of the strata. The rate of pesticide recovery has decreased because of the retarding effect of the clay and the low solubility of the pesticides.

Ground‐truthing 6.5‐kHz side scan sonographs: What are we really imaging?

A 1000‐km2 area on the distal lobe of Monterey Fan shows a digitate pattern of juxtaposed high and low backscatter on GLORIA side scan sonographs. This area was investigated using stereo photography, high‐resolution seismic profiles, and measurements of physical properties of cores to quantitatively evaluate the causes of backscatter from the 6.5‐kHz side scan sonar. Stereo photography and bottom video were used to determine that the sediment‐water interface typically has a bed roughness less than 10 cm over the entire ground truth area; consequently, bed roughness is not a significant contributor to the sonar backscatter. Vertical‐incidence 3.5‐kHz profiles reveal that high‐backscatter areas allow less penetration and have slightly more relief than low‐backscatter areas. Closely spaced measurements of p wave velocity, density, and grain size made on transponder‐navigated cores are used to investigate the geoacoustic properties of the sediment with the aid of a numerical model. The model results demonstrate that the sediment‐water interface is, in most cases, acoustically transparent to the sonar energy and that most or all of the energy is refracted into the sediment to depths of at least a few meters rather than scattered from the surface. The variability of the dominant lithofacies (sands with minor silty clays or silty clay with minor sands) accounts for a regional correlation with backscatter when viewed over hundreds to thousands of square kilometers, but at the detailed scale of hundreds to a few square meters, we have not yet been able to identify a correlation of backscatter intensity with the angle of incidence, surface lithology, measured acoustic impedance, or attenuation. However, there is a qualitative, but unexpected, correlation with lithostratigraphic variability. In this area, thick (up to 50 cm) sand deposits with thin interbeds of silty clay correlate with lower backscatter than do silty clay deposits with thin interbeds of sand. This suggests that volume inhomogeneities and complex constructive and destructive interferences caused by the subsurface volume inhomogeneities within the top few meters of the sediment ultimately modulate the intensity of backscatter. The ground‐truthing effort was further complicated by trying to compare the very large sonar footprint of a pixel (∼70,000 m2) relative to the area of an individual core (0.006 m2), bottom photograph (∼5 m2), or seismic profile. Although 6.5‐kHz sonographs appear easy to interpret in a conventional and simplistic manner, caution should be used when interpreting lithofacies from backscatter intensities.

Behavior of Mexico City clay subjected to undrained repeated loading

This note describes a series of cyclic triaxial tests on undisturbed soil samples of Mexico City clay, obtained near the SCT building. The site is a silty clay deposit of a very high water content and soft consistency. The material exhibits elastic behavior in spite of its very high water content. Three empirical relationships describing an equivalent Young's modulus, an equivalent damping ratio, and a cyclic stress level, associated with cyclic strain level, were obtained. Test results define two different patterns of strength loss. Key words: undrained strength, repeated load, clay, modulus, damping, Mexico City.

Pollutant migration from two sanitary landfill sites near Sarnia, Ontario

Contamination profiles below two youthful landfills founded on thick silty clay deposits near Sarnia, Ontario were obtained by squeezing pore water from Shelby tube samples and analyzing this water by absorption flame photometry for Ca++, Mg++, Na+, and K+. Pollution fronts were observed below both sites, the contaminant cation concentrations attenuating with distance to normal background values.The older landfill was about 7 years old, was founded at 5.6 m depth below the weathered crust on intact silty clays, and was characterized by a downward flow gradient from the base of the fill. Pollution (cation) migration had proceeded downwards for a distance of 30 cm compared to the calculated maximum possible advance of the seepage front of only 4 cm.The younger landfill was about 2.5 years old, was founded at 2.3 m depth within the crust on weathered and fissured soils, and was characterized by upward flow into the landfill due to heavy loads created by the large mound of waste. Pollution migration had proceeded for a distance of 50–80 cm opposite to the prevailing direction of seepage flow and is presumed to have occurred along well developed fissures in the soil.At both sites the diffuse pollution fronts are attributed to cation (chemical) diffusion which, in the early stages of both landfills, has overwhelmed seepage flow.

A palynological study of postglacial vegetation changes in the University Research Forest, southwestern British Columbia

The postglacial vegetation history of the University of British Columbia Research Forest was investigated using percentage and absolute pollen analysis, macrofossil analysis, and radiocarbon dating. A marine silty clay deposit records the oldest (12 690 ± 190 years before present (B.P.)) assemblage of terrestrial plant remains so far recovered from the postglacial of south-coastal British Columbia. Lodge-pole pine (Pinus contorta) dominated this early vegetation, although some Abies, Picea, Alnus, and herbs were also present. Sediment cores from two lakes were also studied. The older is Marion Lake, where five pollen assemblage zones are recognized, beginning with a previously undescribed assemblage of Pinus contorta, Salix, and Shepherdia in clay older than 12 350 ± 190 B.P. The pollen diagram from Surprise Lake (11 230 ± 230 B.P.) is divided into three pollen zones which show the same major trends of vegetation change as the Marion Lake diagram.The first report of the postglacial vegetation history of cedar (Thuja and perhaps Chamaecyparis) in southwestern British Columbia is presented from pollen and macrofossil analyses.At about 10 500 B.P. in both lakes, pollen of Douglas fir (Pseudotsuga menziesii) began a rapid increase, probably in response to climatic amelioration. The palynological evidence, supported by well-preserved bryophyte subfossils, suggests that humid coastal conditions have prevailed in the study area since about 10 500 B.P., with virtually no evidence for a classical Hypsithermal interval between 8500 B.P. and 3000 B.P.

Sediments and Sedimentary Structures of the Astoria Submarine Canyon-Fan System, Northeast Pacific

ABSTRACT Cores taken from the Astoria Submarine Canyon-Fan system illustrate the typical lithology and structure found in sediment deposited in these environments. The deposits include both postglacial and late glacial sediment. The postglacial sediment is mostly hemipelagic silty clay, except on the floor of Astoria Canyon and Channel where the clay is interbedded with some turbidity current deposits. The late glacial sediment, however, consists of numerous interlayered silty clay and turbidity current deposits. The turbidites range in grain size and thickness from micaceous silt laminae to thick beds of sand and gravel. In addition to these deposits, ice-rafted pebbles occur in glacial sediment and slump structure and burrows in the postglacial sediment of the canyon-fan system. The sediment and sedimentary structures of the Astoria Canyon-Fan system provide a basis for comparison with other modern and fossil canyon-fan systems. Certain characteristics of the canyon and fan deposits that permit them to be identified as a related system include the laterally continuous contacts between postglacial and glacial sediment, distinctive mineral and faunal compositions, and rhythmically interbedded turbidites and hemipelagites. Certain distinctions, however, can be made between deposits of the canyon and fan. Homogeneous silty clay beds dominate the canyon deposits, which also contain more organic material and glauconite and show more evidence of slumping than do the fan deposits. The deposits of the fan, in contrast, contain numerous thick, coarse, well-sorted sand and silt beds that exhibit well-developed internal structures. Distinctions can also be made between deposits from different parts of the fan. Beds from the lower fan typically show features of the Bouma sequence of sedimentary structures (grading, parallel lamination, current ripple lamination). The beds themselves consist of moderately well-sorted sand and silt and are separated by clearly defined clayey interbeds. In contrast, deposits from the upper fan channels are characterized by poorly sorted, structureless muddy gravel, sand, and silt beds. Sediment from interchannel regions on the upper fan is mostly clay that contains poorly sorted silt laminae.