Clayey Silt Layer Research Articles

Field Experimental Study on the Infiltration and Clogging Processes at Aksu Research Site, Kazakhstan

The challenge of a good quality drinking water supply to southeastern Kazakhstan’s local population from far-away natural surface water sources motivates groundwater utilization from local aquifers. To prevent groundwater resource deficits, artificial groundwater recharge is needed. To this end, infiltration and clogging processes were evaluated through comprehensive field research in southeastern Kazakhstan’s typical river drainage basin (Aksu experimental site). The infiltration scenario included constructed mini pools and their typical soil profile clogging and silting processes. The local aquifer unsaturated and upper saturated zones underwent a detailed study of water balance, hydrodynamic setting, and filtration properties. The research results suggest that the infiltration rate decreased from 15 m/day until the saturation steady state and remained at 0.75 m/day until the end of the experiment. In summer, clogging layers with thicknesses ranging from 3 mm for the clayey silt layer to 6 mm for muddy clay began to form at the mini pools nearly one month after the test began. During infiltration, the mini pools’ upper soil layer dirt-holding capacity varied from 3.72 to 5.25 kg/m2. The field study results serve as a factual basis for artificial replenishment system design and groundwater replenishment methodology optimization in southeastern Kazakhstan and similar regions.

Flow dynamics at the origin of thin clayey sand lacustrine turbidites: Examples from Lake Hazar, Turkey

AbstractTurbidity currents and their deposits can be investigated using several methods, i.e. direct monitoring, physical and numerical modelling, sediment cores and outcrops. The present study focused on thin clayey sand turbidites found in Lake Hazar (Turkey) occurring in eleven clusters of closely spaced thin beds. Depositional processes and sources for three of those eleven clusters are studied at three coring sites. Bathymetrical data and seismic reflection profiles are used to understand the specific geomorphology of each site. X‐ray, thin sections and CT scan imagery combined with grain‐size, geochemical and mineralogical measurements on the cores allow characterization of the turbidites. Turbidites included in each cluster were produced by remobilization of surficial slope sediment, a process identified in very few studies worldwide. Three types of turbidites are distinguished and compared with deposits obtained in flume studies published in the literature. Type 1 is made of an ungraded clayey silt layer issued from a cohesive flow. Type 2 is composed of a partially graded clayey sand layer overlain by a mud cap, attributed to a transitional flow. Type 3 corresponds to a graded clayey sand layer overlain by a mud cap issued from a turbulence‐dominated flow. While the published experimental studies show that turbulence is damped by cohesion for low clay content, type 3 deposits of this study show evidence for a turbulence‐dominated mechanism despite their high clay content. This divergence may in part relate to input variables, such as water chemistry and clay mineralogy, that are not routinely considered in experimental studies. Furthermore, the large sedimentological variety observed in the turbidites from one coring site to another is related to the evolution of a sediment flow within a field‐scale basin made of a complex physiography that cannot be tackled by flume experiments.

고창군 해리면 사반리 일대 3차원 지질모델링을 활용한 제4기 퇴적환경분석

본 연구는 고창군 해리면 사반리에 대해 3차원 지표모델과 3차원 지질모델을 기반으로 고창지역의 제4기 극한 기후에 따른 퇴적기록 분포 특성에 대해 분석하였다. 3차원 지표지질 모델 및 하부지질모델을 구축한 결과, 연구지역의 지질은 기반암, 플라이스토세 퇴적층, 홀로세 퇴적층이 순차적으로 퇴적되었으며, 주로 기저부의 기반암과 상부의 홀로세 퇴적층이 주를 이룬다. 또한 플라이스토세 퇴적층은 연구지역의 동부에 렌즈상의 퇴적층으로, 북동부에 쐐기상의 형태로 관찰된다. 연구지역의 홀로세 퇴적층은 전체적으로 모래층과 점토질 실트층이 순차적으로 퇴적된 지역으로, 이는 해침 환경 당시 퇴적된 하성층으로 사료된다. 특징적으로 연구지역 동부에 분포하는 플라이스토세 점토질 실트층과 홀로세 모래층은 와지 형태로 관측되며 과거 극한기후에 민감하게 영향을 받는 오버워시에 의한 폭풍퇴적물로 사료된다. This study examined stratigraphic research containing extreme climate event during Quaternary period in Saban-ri, Haeri-myeon, Gochang by constructing 3D topographic model and 3D geological model. As a result of 3D topographic model and subsurface geological model, the geology of study area accumulated bedrock, Pleistocene series, and Holocene series chronologically. Most of the study area consist of bedrock on basement and Holocene series on upper layer. Additionally, Pleistocene series are presented as lens-shaped deposit on eastern part, and wedge-shaped deposit on northeastern part. Holocene layers consist of sand and clay-silt layer deposited sequentially where implies fluvial deposits on transgression environment. Distinctively, Pleistocene clayey silt layer and Holocene sand layer on eastern are observed as pond shape deposits that are considered as storm-related deposits originated from overwash system caused by extreme paleoclimate.

PERFORMANCE OF VACUUM CONSOLIDATION IN A THICK CLAYEY DEPOSIT IN SHANGHAI

A vacuum consolidation test was successfully carried out in a (more than 25 m) thick soft clayey deposit in Shanghai. At the site, there is a clayey silt layer located about 5.3 to 6.8 m depth with a relative higher hydraulic conductivity, and a cement deep mixing formed cut-off wall was able to prevent the vacuum leakage through this layer. Prefabricated vertical drains (PVDs) were installed with a spacing of 1.4 m and triangular pattern to a depth of 14 m. The measured results indicate that the degree of vacuum consolidation reached more than 90% in PVD improved zone for a period of about 38 days. Analysis results indicate that the vacuum pressure induced ground deformations can be calculated reasonably well by a previously proposed method. Further field monitoring results show that one month after stopping the vacuum loading, 10 to 65% of the vacuum pressure induced lateral displacement was rebounded, and the percentage rebounding increased with the depth.

Ground Movement during Concrete Pipe Piles Jacking in Silt Deposit

In this study a comprehensive field test program was carried out to closely monitor the ground responses during open-ended concrete pipe piles jacking into a deposit mainly consisting of silt soils. The horizontal soil movement due to pile jacking was of depth-dependent characteristic that cylindrical cavity expansion models were unable to capture. The magnitude of displacement decreased rapidly with depth, and no discernible deflection was measured below the depth of the pile tip. The maximum displacement along the depth occurred at clayey-silt layer with relative lower permeability. The rebound of soil movement may be attributed to the setup effect following the piling stage.

Palynofacies Analysis of Inner Continental Shelf and Middle Slope Sediments offshore Egypt, South-eastern Mediterranean

Marine palynological studies of Quaternary sediments usually focus on dinoflagellate and pollen assemblages for paleoceanographic and paleohydrographic interpretations of past events. This paper focuses on the use of palynofacies analysis for paleohydrological reconstructions of deltaic and deep sea environments to evaluate transport of organic matter to the ocean. These palynodebris data are used to interpret palaeoenvironmental and paleohydrographic changes in two marine cores from the continental shelf (core-1, 27 m water depth) and middle slope (core-2, 1030 m) offshore Egypt, south-eastern Mediterranean Sea, during the latest Pleistocene and the Holocene. The relative abundances of various types of sedimentary organic matter such as phytoclasts, zooclasts, amorphous organic matter and palynomorphs are related to paleohydrographic changes of the overlying water column. Based on the total palynodebris and organic carbon content, sediments of the inner continental shelf core are characteristic of a prodelta environment proximal to a fluvio-deltaic source and moderately distal oxic environments with enhanced structured organic matter preservation potential. In contrast, the palynodebris of the middle slope core show that the basal sediments (105–140 cm depth) indicate suboxic to dysoxic bottom water conditions, followed by anoxic-suboxic bottom water conditions for the interval from 30–85 cm, which represents the S1 Sapropel. The top sediments of core-2 (0–25 cm) were deposited under oxic bottom water conditions, suggesting good ventilation in the water column. A quantitative approach was also used for interpreting the Holocene sea-level changes, based on the correlation between phytoclast and organic matter abundances. Sedimentation rate in the continental shelf is varied, being relatively very low (6.7 cm/kyr) in the basal part and increased upward to be 20 cm/kyr (depth 115–120 cm). In the upper Gray clayey silt layer the sedimentation rate was high (about 40–45 cm/kyr) due to the high discharge from El Manzala Lagoon and Damietta Nile branch. In the middle slope depth the sedimentation rate was relatively low and uniform, around 14 cm/kyr.

Geochemical processes underlying a sharp contrast in groundwater arsenic concentrations in a village on the Red River delta, Vietnam

Abstract The spatial variability of As concentrations in aquifers of the Red River Delta, Vietnam, was studied in the vicinity of Hanoi. Two sites, only 700 m apart but with very different As concentrations in groundwater (site L: NH 4 + (∼10 mg/L), HCO 3 - (500 mg/L) and dissolved P (600 mg/L), in addition to elevated As at site H are consistent with a release coupled to microbially induced reductive dissolution of Fe oxyhydroxides. Other processes such as precipitation of siderite and vivianite, which are strongly supersaturated at site H, or the formation of amorphous Fe(II)/As(III) phases and Fe sulfides, may also influence the partitioning of As between groundwater and aquifer sands. The origin of the redox contrast between the two sites is presently unclear. Peat was observed at site L, but it was embedded within a thick clayey silt layer. At site H, instead, organic rich layers were only separated from the underlying aquifer by thin silt layers. Leaching of organic matter from this source could cause reducing conditions and therefore potentially be related to particularly high concentrations of dissolved NH 4 + , HCO 3 - , P and DOC in the portion of the aquifer where groundwater As concentrations are also elevated.

Comparison of hydrogeologic and hydrochemical conditions between two uncontrolled landfills

Hydrogeologic and hydrochemical conditions of two uncontrolled landfills without underlying liners, leachate collection and treatment systems in Korea were compared. The landfills are located in Cheonan and Wonju cities. With similar weather conditions, spatial distribution and temporal variations of contaminants of concern and redox parameters were largely different for the two landfills. These differences are highly associated with ages and hydrogeologic settings of the landfills. Groundwater flow diverges from the Cheonan landfill while it converges to downgradient area in the Wonju landfill. Less permeable clayey silt layer or silty soil in the subsurface limited dispersion of leachate plume in the former landfill but highly permeable sandy soil with good lateral extent facilitated rapid plume dispersion in the latter landfill. In addition, hydraulic properties of the cover soil played a role in the different development of redox conditions, which resulted in significantly different concentrations of nitrates. Most problematic contaminants at downgradient wells of the landfills are ammonia and nitrate. Especially in Wonju area, high concentrations of nitrates in downgradient groundwaters exceeding the Korean drinking water standard of 10 mg/L (as NO3‐N), essentially required a mitigation measure.

Numerical analysis of a landslide in soils with strain-softening behaviour

The results of an analysis concerning a landslide of great dimensions, which occurred at Senise (Southern Italy) on 26 July 1986, are presented. The landslide was of a translational type, and the failure developed within a thin clayey silt layer interbedded by a slightly cemented sand formation. Both these soils experienced a pronounced strain-softening behaviour during laboratory tests. From the analyses performed using the traditional limit equilibrium approach, it has been found that the average operational resistance along the sliding surface was less than that of the peak and greater than the residual resistance deduced from the laboratory tests. As a consequence, it has been postulated that a progressive failure had occurred. Such a failure process can be appropriately studied using methods that are capable of simulating the formation and development of shear zones, where strain is localised. From a computational point of view this presents many difficulties, because the numerical procedures currently used are very often affected by a lack of convergence, and the solution may depend strongly on the mesh adopted. In order to overcome these numerical drawbacks, in the present study use is made of both an elasto-viscoplastic constitutive model and a nonlocal elasto-viscoplastic model implemented in a finite element code. The Mohr–Coulomb plastic law is adopted, and the strain-softening behaviour of the soil is simulated by reducing the strength parameters with the accumulated deviatoric plastic strains. The results of the analysis show that a progressive failure occurred owing to deep excavations carried out at the toe of the slope. In addition, the soil mass involved in the sliding and the location of the failure surface deduced from the numerical simulation are found to be very similar to those observed.

The recent sedimentation history of Aqualate Mere (central England): assessing the potential for lake restoration

As part of English Nature’s Lakes Flagship Project to address adverse environmental impacts on selected, important lakes, a proposal has been made to dredge Aqualate Mere. The site has experienced rapid, ‘recent’ sedimentation thought to be derived from a nearby canal. The aim of this study has been to determine the recent sedimentation history of the site in order to assess the possibility of the disposal to land of its sediments and the efficacy of this form of lake restoration. A predominantly clayey silt layer was found across the lake beneath which darker, organic-rich sediments were noted. This transition may represent the input of canal-derived sediments, although it may reflect other environmental changes at this time. The radiometric dating technique employed was unable to date this sediment boundary. A further change in the characteristics of the upper part of the clayey silt layer may represent an additional influence of the canal. Heavy metal levels were modest, whereas nutrient levels were relatively high and some pesticides were detected. Topsoil erosion supplying nutrients and other compounds associated with agriculture have been an important source of the lower layers of the clayey silt sediments in particular. The highest levels of most pollutants were found in the finer sediments in the uppermost (post-1950s) part of the sediment profile. These sediments appear to reflect a change in the characteristics of the sediments of the canal, which was associated with a change in the nature of its water supply. The key geochemical properties of the sediments should not preclude the land-based disposal of dredged materials under current UK regulations for waste management. Accurate estimation of sediment quantities was limited, as the interface between the ‘recent’ and underlying sediments was not positively identified at all sample points.

Geological criteria for waste disposal site selection: a case study from Kanichadar, Dhangarhi, Far Western Nepal

Proper management of municipal solid waste in an environmentally friendly way needs first-hand knowledge of site geology. A clay layer (i.e. geological barrier) of sufficient thickness and extension beneath the surface is a suitable condition for a sanitary landfill site. The clay layer acts as a natural barrier against the migrating pollutants originating from leachate into the ground. The leachate generated at the landfill site can pollute the groundwater in absence of such geologic barrier.
 The Kanichadar area is underlain by about 3 m thick fine-grained soil. The topmost soil layer is 20-50 cm thick dark brown organic clay. There is a highly compact, dark brown and dry inorganic clayey silt layer of more than 1.5 m thickness below the organic clay layer. Soil samples collected from different Auger holes were subjected to laboratory analysis to determine their physical and chemical properties. The values thus obtained indicated that the soil belongs to 'CL' type, implying that the soil is inorganic clay of low to medium plasticity. However, the hydrometer analysis showed that the samples were of clayey silt.
 The cation exchange capacity (CEC) values obtained from the depth of 0.5-2.30 m revealed that the soil had moderate to high barrier potential for attenuation of the migrating pollutants. Therefore, the area close to these auger holes was found to be suitable for sanitary landfill.

Time variations of phosphorus and sources of sediments beneath the Chang Jiang (Yangtze River)

Depth-dependent changes of different forms of sediment phosphorus in a 98-m drill core from near the mouth of the Chang Jiang (Yangtze River) have been determined using a modified chemical extraction method. Results indicate that the dominant portion of the phosphorus is in inorganic form, and that there is an upward increase in detrital apatite. The concentration of phosphorus associated with hydrous ferric oxides (Fe-P) exhibits an excellent positive correlation with the fine size fraction of the sediments, indicating the close association between ferric oxides and high-surface-area mineral grains. Most notable is a yellow clayey-silt layer of low sand content at 39.5-m depth which is very rich in Fe-P. Four possibilities are presented to explain the possible source of the yellow layer. One possibility is that the yellow layer may represent loess-rich Huang He (Yellow River) sediment transported far to the south due to a large former shift of the Huang He mouth. The visual characteristics and chemical observations for the above core, combined with some geological clues are in agreement with this hypothesis. Besides these geological observations, Chinese historical documents provide additional evidence for large former shifts of the mouth of the Huang He.

Kern River Steam-Foam Pilots

Summary Shell conducted two steam-foam pilots in the Kern River field, one on theMecca lease (1980–85) and the other on the Bishop fee (1982–86). The pilotsconsisted of four contiguous inverted five-spots covering 12 and 14 acres [4.8and 5.7 ha], respectively. The Mecca pilot began after 9 years of steam soaksand 10 years of unconfined steam-drive; the Bishop pilot was preceded by 19years of steam soaks and 1 year of steamdrive. Steam foam in both pilots wasgenerated by continuous injection of 250 B/D [39.7 m3/d] per pattern [coldwater equivalent (CWE)] of 50% quality steam, with 4 wt% NaCl and 0.5 wt%AOS-1618 surfactant in the aqueous phase and 0.06 mol% N2 in the vapor. Introduction The Kern River oil field is in the eastern San Joaquin Valley about 4 miles[6.4 km] north of Bakersfield, CA. The productive sand intervals (Sand J, M, and Q) were deposited in the Pliocene and Pleistocene as a high-energyalluvial-channel complex. Both pilots (Fig. 1) are near the northeast andeastern (updip) boundaries of the Kern River field (Fig. 2). Compared to theheart of the field, the pilot areas are characterized by a higher content ofpore-filling clays, lower oil gravity and higher viscosity, and lower net/grosspay ratios. Tables 1 and 2 give concise, chronological pilot summaries. Geology The steamdriven Sand M in the Mecca pilot (Fig. 3 and Table 3) is dividedinto the Upper, Main, and Poor M sands. The Upper M is about 15 ft [4.6 m]thick and is separated from the Main M by a 3- to 5-ft [0.91- to 1.52-m] clayor clayey-silt layer that is seemingly continuous across the pilot area, withthe exception of the northeastern producer, Mecca Well 27. Below this claybreak, there is a 40-ft [12.2-m] -thick sand package, the Main M, which has nosignificant silt or clay breaks. The Poor M comprises the remaining 25 ft [7.62m] between the Main M and the Sand M base. No definite breaks separate the PoorM from the Main M. In some wells, the Poor M grades from a good-quality sand toa poor-quality pebbly sand mixed with silt and clay. In other wells, the Poor Mconsists of pebbly sand, silts, and clays randomly mixed throughout theinterval. These silt and clay layers do not appear to be continuous from wellto well. Average gross thickness for Sand M in the Mecca pilot is 83 ft [25.3m], and net pay thickness is 67 ft [20.4 m]. The remaining 16 ft [4.9 m] can besplit between poor sand (7 ft [2.1 m]) and clay or clayey silts (9 ft [2.7 m]). The geometrical pilot area is 11.6 acres [4.7 ha]. Because steam foam invadedthe Poor M, the net pay thickness was adjusted to 74 ft [22.6 m], increasingthe original oil in place (OOIP) in the geometrical pilot area from 1,190,000to 1,400,000 STB [189 × 10–3 to 223 × 10–3 stock-tank m3]. The latter value isthe upper bound on the volume of oil originally in the Mecca pilot. Sand Q inthe Bishop pilot (Fig. 4) is a 100-ft [30.48-m] -thick sand package dividedinto several layers by 0 to 3 clay or clayey-silt barriers that are continuousacross at least a single pilot pattern and by 0 to 3 discontinuous barriersthat are randomly distributed throughout the pilot area. Average pay thicknessof good sands in the Bishop pilot is 65 ft [19.8 m] and total thickness ofbarriers is 15 ft [4.6 m], and there is 20 ft [6.1 m] of poor-quality sand. TheOOIP in the geometrical pilot area (14 acres 5.7 ha]) is 1,500,000 STB (238 x10-3) stock-tank m3]. Cation exchange capacity (CEC) is 8 meq/100 g in MeccaSand M and approaches 9 meq/100 g in Bishop Sand Q. These large CEC's arecaused by a high content of montmorillonite and illite (85% in calcium andmagnesium form initially). Oil in the Tank The Kern River pilots were designed to evaluate the performance of steamfoam when applied either very late in a steamdrive (10 years at Mecca) or veryearly (1 year at Bishop). Production and injection histories of the pilots aredetailed in Table 4. In evaluating the pilots performance, we are interestedonly in the incremental oil production resulting from improved volumetric sweepby steam foam (observed in both pilots), and possibly from reduction ofresidual oil saturation (ROS) in the foam-swept zones (none with AOS-1618). Weare disregarding any acceleration of oil production, such as the early responseof the Mecca pilot immediately after the start of foam injection. An unconfinedsteamdrive was run during 1970–80 at Mecca. Such a drive in a dipping reservoirshould produce more oil than a corresponding confined drive, and possibly evenmore than the OOIP because of gravity drainage. JPT P. 496⁁

A DEPOSITIONAL PROCESS OF REVERSE GRADED BEDDING IN FLOOD DEPOSITS OF THE SAKURA RIVER, IBARAKI PREFECTURE, JAPAN

The Sakura River flows in a narrow alluvial channel with gentle slope, draining the southeast area of Ibaraki Prefecture (Figs. 1 and 2). The bed consists of arcosic sand and gravel which reflect the geological condition of the upper drainage basin of the river. The investigation of flood deposits in the upper reaches of the river shows that the flood deposits have reverse grading structure (becoming coarser grain from bottom to top of a bed) and that a sedimentary unit, the lower mud layer and the upper sand layer, is formed during a single flood. It is the purpose of this paper to explain the depositional process of the reverse graded bed from the characteristics of sediment transport in the Sakura. Main results are as follows. The flood deposits are thick only on the cut-sides of the river channel, which are attacked by the main flow of the flood (Fig. 6). Levees are better developed in these areas. Medium and fine sand make up the thick flood deposits on the natural levee (Fig. 7). It begins with the deposition of a thin silt layer and is followed by a thick sand layer which displays no internal structures. Sand sizes, φ1 as well as φ50, gradually increase toward upward. Fig. 8 shows the repeated cycles of coarsening upward sequence of flood deposits on the natural levee. The maximum diameter of each flood deposit has the upper limit of about 10(0. 5mm) . The floods which left the thick flood deposits are shown in the time-stage curves of Fig. 9. Reverse grading is also developed among the thin flood deposits on the lower part of the flood plain (Fig. 7). The lowest clayey silt layer with a thickness of a few milimeters suddenly changes the upper sand layer which usually has fine lamination. Fig. 9 shows the observational results on the hydraulic regimes and the suspended sediment transports in some floods in the Sakura River. It is the common fact to all observations that the maximum concentration of suspended load precedes the peak discharge. Furthermore, it is clear from Fig. 10 that the amount of the finer sediment load of silt-clay and very fine sand is extremely high at the leginning of each flood and rapidly decreases with the rising of waterlevel. The depositional process of reverse graded bedding in flood deposits can be explained as follows and Fig. 12 schematized them. 1. Deposition of the mud layer (Fig. 12-I) It is very likely that the lower muddy part of reverse graded bed is deposited during the beginning of the flood when the concentration of finer grained suspended sediments, the socalled “wash load”, is extremely high. Flood water with large quantities of wash load is diverted into the flood plain and the stagnation of flows on the flood plain causes the deposition of this finer sediments. It can be considered that the reason why mud layers on the natural levee are very thin and rather indistinct (Figs. 7 and 8) is that the natural levee is not covered by the inundated water at this stage. Boils along the bank begin to occur in the mean while. 2. Deposition of the sand layer (Fig, 12-II) The upper sandy part is presumed to be produced by the deposition of suspended sand after the rapid decrease of wash load concentration. The upward coarsening structure in this sand layer may be produced under the condition of gradual increase of flow intensity. The sand make up the natural levee is coarser than that of suspended up to the bankfull level at the center of the channel (Figs. 7, 8 and 11). This fact is explained as follows. Boils over the bank become more and more violent. This suggests that the upward flows (kolks) near the bank become violent with increases of discharge. It is supposed that these kolks cause the coarser sediment grains to suspend near the bank. 3. Preservation of the reverse graded bed (Fig. 12-III) With the beginning of water level falling, the inundated flow turns back from the flood plain to the channel.