Micaceous Sand Research Articles

Influence of Mica Content on Shear Strength, Shear Modulus, and Damping Response of Micaceous Sand

Influence of Mica Content on Shear Strength, Shear Modulus, and Damping Response of Micaceous Sand

A Review on Geotechnical Properties of Soil Profile

The geotechnical properties and litho-stratigraphic soil profile of soils in Ikole area of Ekiti State were investigated from the analysis of results of laboratory tests on disturbed and undisturbed soil and water samples obtained from 3 borings. The investigation revealed a subsurface stratification made up of reddish brown granitic clayey sand from existing ground level to a depth of 9m to 12.0m. This is underlain by a layer of mottled, brown, decomposed micaceous sand to a depth of 16.5m - 18m immediately after which are layers of mottled grey, decomposing quartzite sand to about 18.0m to 19.0m depth. This is further underlain by fragments of freshly weathered granitic rock to the termination depth of 19.5m. The consistency limits indicate LL of 44 – 58% and PL of 18 – 26% while the quick undrained triaxial tests indicate undrained cohesion within the range (128.4 - 157) kN/m2 and undrained angle of internal friction (15.0 - 20.0)0. Groundwater was encountered between 6.5m to 7.5m below the existing ground level during the course of soil exploration. The water in the area has pH values of 5.79 to 7.05, the chloride content values range between 12.0mg/l and 16.0mg/l while sulphate content varies from 6.12mg/l to 7.10mg/l.

State-of-the-Art Review on the Influence of Mica Toward Geotechnical Performance of Micaceous Sand: A Micro- to Macroscopic Perspective

State-of-the-Art Review on the Influence of Mica Toward Geotechnical Performance of Micaceous Sand: A Micro- to Macroscopic Perspective

Liquefaction Susceptibility and Characterization of Rebound Response of Micaceous Sand

Liquefaction Susceptibility and Characterization of Rebound Response of Micaceous Sand

Effect of Lime, Kaolinite and Bentonite treatment on mechanical behaviour of micaceous sand

ABSTRACT Micaceous sands are known as problematic/undesirable soils for road/railway construction as such soils exhibit rebound action under traffic loading conditions leading to severe damage in subgrades and embankments. In the current research, three commercially available materials (Bentonite, Kaolinite and Lime) have been used independently for treating the micaceous soil to determine the appropriate stabilising agent for the overall enhancement of mechanical behaviour of micaceous soil including compatibility, cyclic stability, stiffness and strength characteristics subjected to various loading and boundary conditions. In the current research, extensive experimental research has been performed on MS treated with Bentonite/Kaolinite/Lime by conducting Compaction, Triaxial (unconsolidated undrained, consolidated undrained and consolidated drained) and cyclic triaxial tests. Bentonite treatment exhibited significant improvement in all the properties of micaceous sand (MS) as compared to Kaolinite and Lime treatment. Bentonite treatment of MS reported a marked reduction in the rebound response of micaceous soil with sustainable cyclic stability. The present research reported Bentonite treatment is the most effective, environmentally friendly and economical treatment for micaceous soil.

Designation of a composite-stratotype section for the lower Paleocene (Danian) Brightseat Formation in Prince George’s County, Maryland, USA

The lower Paleocene (Danian) Brightseat Formation consists of fine-grained, dark-gray, micaceous sand and silty clay, with glauconite and abundant, but generally poorly preserved, fossils. The Brightseat Formation represents deposition of lower, but not lowermost, Paleocene sediments that were deposited on the middle to outer shelf of what is now the Atlantic Coastal Plain. A basal disconformity separates the Brightseat from the underlying Upper Cretaceous Severn Formation, and it is disconformably overlain by the middle to upper Paleocene Aquia Formation. The type locality of the Brightseat Formation, previously exposed approximately 1 mile (1.6 km) west-southwest of the former village of Brightseat in Prince George’s County, Maryland, just outside ofWashington, D.C., has been destroyed by urban development, prompting the establishment of a composite-stratotype section from nearby outcrops approximately a half mile to the south-southwest of the original location. The outcrop at Cabin Branch is hereby designated as the principal reference section for the Brightseat Formation and the “Cabin Creek” outcrop (an informally designated tributary of Cabin Branch) is designated as a supplementary reference section that illustrates the boundary of the Brightseat with the overlying Aquia Formation. Paleontological analyses, grain-size analyses, and petrographic techniques are used to document this new stratotype section and to correlate and contrast it with underlying and overlying sediments. This composite-stratotype section is designated using the guidelines outlined in Article 8, remarks (d) and (e) of the North American Code of Stratigraphic Nomenclature.

Dynamic behaviour of micaceous sand with varying mica content and its association with compactability, compressibility and monotonic shear response

ABSTRACT Cohesionless soils are highly susceptible to liquefaction under dynamic loading with high-strain amplitude simulating earthquake loading conditions. The presence of flaky mica particles among spherical sand influences the microscopic particle level mechanisms due to complex geometric arrangements caused by bridging, ordering and pore filling phenomena. Such variations substantially affect the compactability, compressibility and shear strength behaviour under monotonic and dynamic loading conditions. The current experimental investigations evaluated the effect of mica content on dynamic behaviour of micaceous sand through a series of strain-controlled cyclic triaxial tests at constant frequency and double axial strain amplitude of 0.5 Hz and 0.6% per cycle. The variation in dynamic parameters such as shear modulus and damping was determined at different mica contents along with cyclic stiffness degradation. Cumulative dissipated strain energy was also estimated to understand the contact-force networks of varying sand and mica matrix from sand-sand to mica-mica through sand-mica particle contact.

Effect of mica content on pore pressure and stress-strain response of micaceous sand using energy dissipation and different failure mechanisms

ABSTRACT Mica particles are platy, flexible and resilient in nature having numerous intact mica flakes foliated over each other with low stiffness. Presence of mica among sand particles creates complex geometric arrangements due to bridging, ordering or pore filling phenomena; which make micaceous sand highly compressible with low shear strength. When flaky mica particles are augmented among spherical sand particles, the governing shear behaviour mechanisms substantially varies due to redistribution of contact forces among sand-sand matrix, sand-mica matrix and mica-mica matrix formation of micaceous sand. The current experimental study investigated the effect of mica content on pore pressure and stress-strain behaviour of micaceous sand due to varying sand-mica microstructural evolutions. The variation in shear strength parameters were studied under different failure criteria: peak deviatoric stress and peak effective stress ratio. The deviations in mechanical behaviour of micaceous sand at varying mica content were further examined through cumulative dissipated strain energy mechanisms to understand the inter-particle contact-force transfer mechanisms for varying sand and mica matrix.

Effect of Successive Impact Loading on Compactability, Microstructure, and Compressibility Behavior of Micaceous Sand

Micaceous soils are generally known for their high compressibility, low compactability, and low shear strength behavior. Mica particles are flaky, flexible, and resilient nature with low stiffness and hardness due to numerous foliated intact mica flakes, which allows them to undergo deformation upon loading and rebound upon unloading. However, the weak mica particles among strong sand particles are highly susceptible to crushing, which affects the performance of geotechnical structures. The current research is focused on the effect of successive impact loading on crushability, compactability, compressibility, and microstructure of micaceous sand containing 30% mica. Significant increase in MDD, fine content, and compression index of micaceous sand was observed with the increase in successive cycles of impact loading. The reduction in resilient nature of micaceous soil due to crushing of intact mica particles along with the reduced bridging and ordering combination of sand-mica particles could be responsible for altered compactability behavior of micaceous sand. The increased percentage of fines due to crushing of mica particles caused the reduction in stiffness leading to higher compressibility of micaceous soil.

Sub-surface Biogeochemical Characteristics and Its Effect on Arsenic Cycling in the Holocene Gray Sand Aquifers of the Lower Bengal Basin

High arsenic (As) content in the fertile delta plains of West Bengal has been widely reported since the 1990s. The shallow grey sand aquifers (GSA) deposited during the Holocene, are more commonly used as potable water sources, but they have high As levels. The release of As into groundwater is influenced by indigenous microbial communities metabolizing different organic carbon sources present in the GSA sediments. After pre-screening the groundwater for assessing their microbial phylogenetic diversity, two50-m deep boreholes were drilled in the GSAs, and 19 sediment samples were recovered from each core. In each of these samples, grain-size distribution, sequential extraction, and quantification of trace metals and total extractable lipids were analyzed. The aquifer sediments consisted of medium to fine micaceous sand with clay lenses in between them; a thick clay layer occurred on top of both boreholes. Arsenic concentration in these sediments varied from 1.80 to 41.0 mg/kg and was mostly associated with the oxide and silicate-rich crystalline minerals. Arsenic showed a significant correlation with Fe in all fractions, suggesting the presence of Fe-(oxy)-hydroxides bound As minerals. The diagnostic lipid biomarkers showed presence of compounds derived from higher plants (epicuticular waxes) and microbial inputs. The biomarkers were abundant in clay and silt-rich layers. The samples indicated preferential preservation of n-alkanes over other functional compounds (e.g. alcohols and fatty acids), that are more reactive, and hence subject to further degradation. Sediments recovered from the borehole indicated the presence of Eustigmatophytes and vascular plant waxes that are mostly surface-derived. The sedimentary lipids also indicated the presence of complex petroleum-derived hydrocarbons. These compounds provide organic substrates, and support the preferential survival of specific microbial communities in these sediments.

Groundwater quality analysis of quaternary aquifers in Jhajjar District, Haryana, India: Focus on groundwater fluoride and health implications

Several types of health problems in Jhajjar district of Haryana state are prevailing owing to groundwater quality problems such as high concentration of fluoride, chloride, salinity, TDS, etc. The objective of this work was to assess the overall groundwater quality of the district based on Water Quality Index (WQI), and find out the factors leading to continuous deterioration in groundwater quality. The study demonstrates that groundwater quality of Jhajjar district is totally unsuitable for drinking purposes and is directly or indirectly influenced by geogenic factors. About 60–70% of the samples analysed show high fluoride content. Other parameters such as hardness, electrical conductivity, Total Dissolved Solids (TDS), and Chloride are also above the permissible limits. Hydrogeologically the study area belongs to Indo-Gangetic alluvial plains, which are dominated by clay-silt, clay and grey micaceous sand formations. Clay rich formations are rich in fluorine and other salts and their weathering is most probably causing the continuous escalation in the fluoride and salinity concentration in groundwater. Several in-situ and ex-situ measures have been suggested for remediation and to prevent further escalation of water quality problems that are needed imperatively for the sustainable development of water resources.

Geochemical controls on fluoride concentrations in groundwater from alluvial aquifers of the Birbhum district, West Bengal, India

Groundwaters with high fluoride (F−) concentration up to 13.61mg/L occur in some parts of the Quaternary alluvial aquifer of Birbhum district, West Bengal, India. The high F− groundwater zones are mainly located in the discharge areas of Dwarka river basin, especially in places where groundwater occurs at a depth of 24–30m within alluvial sediments, consisting of micaceous sand, silt and clay. Soil depth samples were collected from the 3 bore holes drilled up to about 30m depth for geochemical analysis. Total F− in the sedimentary material from the drilled holes measured about 400 to 450mg/kg at deeper depth in CS1 and CS3 but no abnormal values found in CS2. XRD, XRF and total F− analyses of sediments from aquifer zone reveal that, the presence of intercalated zeolitic clay within the aquifer sand is the major source of F− in groundwater. Furthermore, geochemical investigations and laboratory analysis emphasize that sorption and de-sorption of intercalated zeolitic clay at different pH levels along with ion-exchange are the major mobilising factors for F− in pre- and post-monsoon seasons. Most of the groundwater having fast recharge component either from flowing canals or rainfall, contains relatively depleted δ18O content (−5 to −4‰). However, δ18O content has no correlation either with Cl− or F− that shows more than one contaminant sources.

Depositional history and palaeoclimatic variations at the northeastern fringe of Thar Desert, Haryana plains, India

The >400 m thick column of alluvial, lacustrine and aeolian strata at the semi-arid northeastern fringe of Thar Desert in Haryana has vast potential to provide information on fluctuating climate since the Middle Pleistocene. The sediment column has been deposited by Himalayan-fed rivers, most of which subsequently disappeared due to climatic and tectonic reasons. The distinctive lithologies with minor variations offer direct evidence to their depositional environments and indirect clues to the monsoonal climate of the region. In this study, broad palaeoclimatic variations, since the terminal part of the last interstade, have been inferred on the basis of sediment characters and luminescence dating of representative sections along the Thar margin and in its ameliorated part. The general field stratigraphy established for the upper part of Late Quaternary plains comprises a buried alluvial sequence of grey micaceous sand, deposited by perennial rivers, overlain by undifferentiated, partially buried aeolian brown sands. Optically stimulated luminescence (OSL) ages from the upper parts of alluvium indicate a gradual disorganization of the river system ca. 28–20 ka. The disorganization commencing at around 28 ka corresponds with the increasing aridity of the last glacial maximum (LGM) and shows the decreasing strength of the monsoon. However, the survival of river system until ca. 20 ka, even during the LGM aridity, signifies that the monsoon had not completely disappeared in this region. Further weakening of monsoon is indicated by the deposition of aeolian sand over the alluvium. The area witnessed a major phase of aeolian deposition ca. 18–12 ka which extended up to the present day 600 mm isohyet. The subsidiary phase appears to have prevailed in southern parts of Haryana ca. 9–7 ka. Younger aeolian activity has occurred since ca. 3.2 ka near the Thar front. No record of aeolian deposition during LGM is identified in this area, as in the core of the Thar Desert. However, the post LGM, aeolian deposition in Haryana is found to have begun earlier and continued longer than in the Thar Desert.

Applications of the oedometer, triaxial and resonant column tests to the study of micaceous sands

Intergranular void ratio, e s, can be used as an alternative indicator to assess the mechanical and dynamic properties of composite matrix of coarse and fine grains. In this paper, an intensive laboratory study of saturated coarse rotund sand (i.e., Leighton Buzzard Sand) and fine (i.e., mica) mixtures with various mix ratios is performed by a series of oedometer, triaxial and resonant column tests. Oedometer tests performed on coarse rotund sand–fine mixtures show that initial conditions, fines percentages, and stress conditions affect the compression behaviours. Tests indicated that, up to a fraction of mica, which is named as transition fines content (FC t), compression behaviour of the mixture is mainly governed by the sand grains. As the percentage of mica exceeds FC t, mica governs the compression. In the triaxial tests, deviatoric stress ( q), pore pressure ( u), and undrained Young's modulus (Eu) have been obtained in a triaxial testing apparatus. Results revealed that there is a close relationship between the FC t and q, u, and Eu values. In the resonant column tests, a study of dynamic properties of saturated mixtures was investigated by measuring its shear modulus ( G) and damping ratio ( D), which is harmonic with the oedometer test results.

Unstable behaviour of model Jamuna micaceous sand

(a) A specimen can collapse under a drained condition if the test is conducted under a load-controlled loading mode as shown and discussed in detail by Chu & Leong (2003a, 2003b) and Chu & Wanatowski (2009). (b) By confining the conclusion to ‘fully drained conditions’, the discussers would assume that the author considers that instability under ‘fully undrained conditions’ involves collapse or loss of strength. This is also an observation made by a number of researchers (e.g. Lade & Pradel, 1990; Lade, 1992, 1993; Sasitharan et al., 1993; Leong et al., 2000; Chu & Leong, 2003a, 2003b; Chu et al., 1993, 2003; Chu & Wanatowski, 2009). As the author did not specify otherwise, the discussers assume that the term ‘drained’ is used to refer to a condition where water is allowed to flow in or out of the specimen under a constant back pressure condition. Under such drained condition, the effective confining stress or the effective stress path can be controlled by varying the cell pressure. With today’s laboratory testing techniques, it is possible to carry out a special ‘drained’ triaxial test to trace the curved effective stress path followed in an undrained test in which the specimen has collapsed. Assume this special test is conducted under a load-controlled loading mode, would the specimen in this test collapse or not? If it would, then this collapse is under a drained condition. If it would not, then what are the other factors that control the collapse in addition to the effective stresses?

Migration of the Ganga river and its implication on hydro-geological potential of Varanasi area, U.P., India

Borehole data reveals that during Late Quaternary, the Ganga river was non-existent in its present location near Varanasi. Instead, it was flowing further south towards peripheral craton. Himalayan derived grey micaceous sands were being carried by southward flowing rivers beyond the present day water divide of Ganga and mixed with pink arkosic sand brought by northward flowing peninsular rivers. Subsequently, the Ganga shifted to its present position and got incised. Near Varanasi, the Ganga river is flowing along a NW-SE tectonic lineament. The migration of Ganga river is believed to have been in response to basin expansion caused due to Himalayan tectonics during Middle Pleistocene times. Multi-storied sand bodies generated as a result of channel migration provide excellent aquifers confined by a thick zone of muddy sediments near the surface. Good quality potable water is available at various levels below about 70 m depth in sandy aquifers. Craton derived gravelly coarse-to-medium grained sand forms the main aquifer zones of tens of meter thickness with enormous yield. In contrast, the shallow aquifers made up of recycled interfluve silt and sandy silt occur under unconfined conditions and show water-level fluctuation of a few meters during pre-and post-monsoon periods.

Micaceous Sands: Microscale Mechanisms and Macroscale Response

The presence of mica changes the mechanical behavior of sandy soils. In this study, micro- and macroscale tests are used to explore the unique packing characteristics that develop in mixtures made of round and platy particles, and the effects that mica exerts on small, medium, and large strain parameters. Mixtures are prepared with different mica contents and various mica-to-sand size ratios, Lmica∕Dsand. Results provide a comprehensive characterization of mixtures made of spherical and platy particles. Mica plates change sand packing through pore filling, bridging, ordering, and mica–mica interaction; bridging prevails and leads to open fabrics when Lmica∕Dsand≥1. As the mica content increases in mixtures with Lmica∕Dsand≥1, the shear-wave velocity decreases and it becomes more sensitive to the state of stress; the constraint modulus decreases; and the peak and residual friction angles decrease. Remixing during disordered granular flow prevents mica alignment and diminishes the otherwise weakening effect of mica on large-strain strength.

Vertébrés de l'Oligocène terminal (MP30) et du Miocène basal (MN1) du métro de Toulouse (Sud-Ouest de la France)

Latest Oligocene (MP30) and Earliest Miocene (MN1) vertebrates from the Toulouse subway (SW France). The excavation for the line B of the Toulouse subway led in 2002–2003 to the discovery of various vertebrates, including the rhinocerotids Diaceratherium lemanense, Mesaceratherium paulhiacense, and Protaceratherium cf. minutum, an unidentified schizotheriine chalicotheriid, the artiodactyl Cainotherium sp., the theridomyid rodent Issiodoromys bransatensis, the testudinid tortoise ‘Ergilemys’ bruneti, and the small alligatoroid Diplocynodon sp. These first in situ diversified faunas of Toulouse confirm the Latest Oligocene (MP30) to Earliest Miocene age (MN1) of the micaceous sands interbedded with marl banks of the Toulouse underground. The fauna indicates the occurrence of various environments, ranging from forests to open habitats, nearby steady rivers for the concerned period and area. To cite this article: P.-O. Antoine et al., C. R. Palevol 5 (2006) .

Success Factors in Troll Geosteering

This article, written by Technology Editor Dennis Denney, contains highlights of paper OTC 17110, “Success Factors in Troll Geosteering,” by S. Leiknes and I. Osvoll, Norsk Hydro ASA, prepared for the 2005 Offshore Technology Conference, Houston, 2–5 May. Copyright 2005 Offshore Technology Conference. Reproduced by permission. Hydro has produced oil from horizontal wells in the thin oil layer of the Troll West field offshore Norway since 1995. The main challenge is to drain the thin target sands efficiently, within a remain-ing oil column less than 20 m thick covering an area of approximately 500 km2. New horizontal producers are continually being drilled. Vertical geosteering is performed on a centimeter scale, and quick decision making within the well teams is needed to optimize the well paths while drilling. Introduction The Troll field is the largest producing oil and gas field on the Norwegian continental shelf. The field is in the northern North Sea on the margin of the Viking graben and is divided by two major north/south trending faults separating the field into three provinces: Troll West oil province, Troll West gas province, and Troll East. Oil has been produced from horizontal wells in the Troll West oil and gas provinces where the initial oil-column thickness was 22 to 27 m and 11 to 13 m, respectively. More than 150 horizontal producers have been drilled in Troll West, and approximately two-thirds of the total oil reserves of 1.4 billion bbl has been produced. The oil column in Troll East is 1 to 4 m thick, and only the huge gas cap has been considered commercial. New horizontal producers are drilled in the progressively thinning oil layer. As shown in Fig. 1, well planning and drilling are increasingly difficult because of the ever-larger number of existing producers, the consequent decrease in remaining targets, and movement of the fluid contacts resulting from production. Collaboration between geophysicists, geologists, and reservoir and production engineers is crucial to meet this challenging task. Reservoir Framework The reservoir consists of stacked, off-lapping, shallow marine sandstones and intervening siltstones mostly in the Upper Jurassic (Oxfordian) Sognefjord formation. Reservoir zones correspond to the finer and coarser portions of the prograding wedges (parasequences) and can be mapped with good confidence over most of the field. For geomodeling and well-planning purposes, the depositional succession is simplified into clean sand and micaceous sands. The clean sands generally are well sorted, with permeabilities ranging from 1 to 30 darcies, while the micaceous sands are characteristically finer and silty, with permeabilities ranging from 10 to several hundred millidarcies.

Hydrogeology of Brahmaputra Basin, India

The Ganga-Brahmaputra river system together forms one of the largest deltas in the world comprising some 59570 sq km. The waterpower resources of the Brahmaputra have been presumed to be the fourth biggest in the world being 19.83 x 103 m3s1. The entire lower portion of the Brahmaputra consists of a vast network of distributary channels, which are dry in the cold season but are inundated during monsoon. The catchment area of the entire river is about 580,000 sq km, out of which 195,000 sq km lies in India. The maximum discharge as measured at Pandu in 1962 was of the order of 72800 m3 s-1 while the minimum was 1750 m3 s-1 in 1968. The drainage pattern in the valley is of antecedent type while the yazoo drainage pattern is most significant over the composite flood plain to the south of the Brahmaputra.
 The Brahmaputra valley is covered by Recent alluvium throughout its stretch except a few isolated sedimentary hills in the upper Assam, inselbergs/bornhardt of gneissic hills in the Darrang, Kamrup and Goalpara districts and a few inlying patches of Older Alluvium in the Darrang and Goalpara districts.
 The basin is very unstable. The present configuration of the basin is the result of uplift and subsidence of the Precambrian crystalline landmasses. Four geotectonic provinces can be delineated in the N-E India through which the Brahmaputra flows. These are bounded by major tectonic lineaments such as the basement E-W trending Dauki fault, a NE-SW trending structural feature of imbricate thrusts known as 'belt of Schuppen' and the NW-SE trending Mishmi thrust.
 Hydrogeologically, the Brahmaputra basin can be divided into two distinct categories, viz(a) dissected alluvial plain and (b) the inselberg zone. The first category is rep resented in the flood plain extending from the south of Sub-Himalayan piedmont fan zone in the north to right upto the main rock promontory of Garo Hills and Shillong Plateau. The inselberg zone is characterized by fractured, jointed and weathered ancient crystalline rocks with interhill narrow valley plains, consisting of thin to occasionally thick piles of assorted sediments.
 From the subsurface lithological data, two broad groups of aquifers are identified. These are i) shallow water table and ii) deeper water table or confined ones, separated by a system of aquicludes. The shallow aquifer materials, in general, consist of white to greyish white, fine grained micaceous sand and the thickness ranges from 1.2 to 10.3 m. The sand and clay ratio varies from 1: 2.5 to 1:26. The bedrock occurs at depth ranges of 30.4 to 39.5 m. The materials of the deeper aquifers comprise grey to greyish white, fine to medium grained sand. The sand and clay ratio varies from 1:2 to 1:7. The effective size of the aquifer materials varies from 0.125 to 0.062 mm with uniformity co-efficient around 4.00, porosity 38 to 42%, co-efficient of permeability 304 to 390 galls per day/0.3m2. The ground water is mildly alkaline with pH value 6.5 to 8.5, chloride 10 to 40 ppm, bi-carbonate 50 to 350 ppm, iron content ranges from a fraction of a ppm to 50 ppm. Total dissolved solids are low, hardness as CaCo3 50 to 300 ppm, specific conductance at 25 °C 150 to 650 mhos/cm. The yield from shallow aquifers is 1440 litres to 33750 litres/hour and for deeper aquifers ~ 1700 litres/hour at a drawdown of 13.41 m, specific capacity 21 litres/minute. The temperatures of ground water are 23°-25° C during winter, 24°-26° C during pre-monsoon and 27°- 28° C during peak monsoon. The general hydraulic gradient in the north bank is 1:800 whereas in the south bank it is 1: 300-400 The Tertiary sediments yield a range of water from 200 to 300 l.p.m whereas the yield from the Older Alluvium is 500 to 700 1.p.m. The estimated transmissibility and co-efficient of storage is of the order of ~ 800 1.p.m/ m and 8.2 x 10-3 respectively. Depths to water levels range from 5.3 to 10m below land surface (b.l.s). In the Younger or Newer Alluvium, ground water occurs both under water table and confined conditions. Depths to water levels vary from ground level to 10 m b.l.s. Depth to water ranges from 6 m b.l.s. to 2 m above land surface. The yield of the deep tubewells ranges from 2 to 4 kl/minute for a drawdown of 3 m to 6 m. The transmissibility of the aquifers varies from 69 to 1600 l.p.m/m and the storage co-fficient is of the order of 3.52 x 10-2.