Clay Till Research Articles

Trace element geochemistry of a thick till and clay-rich aquitard sequence, Saskatchewan, Canada

Samples collected from a 170 m borehole penetrating till, bentonitic clay, and sand at the Birsay site, Saskatchewan, Canada, has been studied as a first step for understanding the controls on dissolution and transport of trace elements, including REEs, in porewaters of a clay-rich aquitard. The REE budgets of the till, clay, and sand are dominated by apatite and monazite, with sporadic zircon and Y-phosphate. Apatites contain 0.3 to 1.7 wt.% REE, and monazites 12 to 55 wt.%. All three units are characterized by unusual bulk sample REE patterns, with maxima at Eu–Gd, convex down patterns from La–Sm with minima at Ce, and variably fractionated HREE. Apatites feature maxima at Eu–Gd. Consequently the complex patterns arise from variable modal proportions of apatite, monazite, and plagioclase feldspar. Relative to Post-Archean Average Shale (PAAS), the till is SiO 2 and CaO rich with about half the contents of Al 2O 3, TiO 2, and Fe 2O 3. These compositional relationship stem from relatively high proportions of quartz and carbonate, but low modal abundances of ferromagnesian and Ti-oxide minerals. Similarly, the till has Cs, Co, Ni, Sc, V, Cu, Pb and Zn contents at about half PAAS. The bentonite clay has slightly higher SiO 2 and CaO contents than PAAS, with lower abundances of most other trace elements, including REE which plot at 0.7 to 0.9 PAAS. The major and trace element composition is similar to continental arc andesites, and the clay is interpreted to have a mixed provenance of arc andesite and eroded underlying sands. The composition of the till appears to reflect mixed provenance: erosion of the underlying Cretaceous clay and sand, Paleozoic carbonate rocks, and the Precambrian Shield. The silicious Ardkenneth sand has lower concentrations of REE and most trace elements compared to the clay, but the most fractionated REE patterns. The clay and till have inherited more subdued REE patterns in part from the underlying sand unit. Compositional variations between the units are marked by an upturn of Nb, Th, U and REE concentrations at the till–clay interface (80.2 m), and decrease of these elements at the clay–sand boundary (156.2 m). Ce and Eu anomalies vary erratically with depth: the anomalies appear to reflect the degree of sedimentary sorting, which in turn controls the modal abundances of detrital monazite, apatite, zircon, and plagioclase feldspar. Zr/Zr*, Hf/Hf* and Zr/Hf ratios are higher in the till than the clay and sand, indicating an additional Zr (Hf)-bearing phase with a distinctively high Zr/Hf ratio. The observed small compositional variations in the till and clay are not reflected in variations of geotechnical properties. Given that the REE budget of the till and clay are dominated by highly insoluble trace minerals, it is unlikely that the REE patterns of porewaters will be controlled by bulk sample REE concentrations. Weathering of the upper 3 m of the till has oxidized Fe 2+-bearing silicates, oxides, and sulphides, and dissolved carbonates relative to the underlying unoxidized till, weathering has not disturbed major, REE or other trace element compositions.

Assessment of Two Automated Electrical Resistivity Data Acquisition Systems for Landfill Location Surveys: Two Case Studies

Two types of automatic DC resistivity data acquisition systems, the Aarhus PA-CEP system and the ABEM Lund Imaging System, are assessed in connection with surveys for characterization of future landfill sites. In the first case, the extent of a natural clay layer in connection to an enlarge­ ment area of the Filborna landfill was mapped, and in the second case the soil cover at a proposed new landfill at Flaskebo was examined. At Filborna both resistivity systems and seismic refraction were used, whereas at Flaskebo the Lund system was used together with a VLF survey. At both locations 5 km of resistivity profiling were achieved. The resistivity datasets were interpreted with a smoothest constrained inversion. At Filborna a layer of thick clay till was identified in the southwest part of the investigation area, and thin clay tills were found in other parts. It was clear from the PACEP resistivity models that the underlying sedimentary rock possesses an undulating surface, which has an important implication regarding the soil cover barrier properties. At Flaskebo the resistivity survey successfully delineated the bedrock surface and effectively mapped the soil cover. Both re­ sistivity systems worked well acquiring data suitable for data inversion. The seismic refraction model and resistivity models corresponded reasonably well. The pulled array continuous electrical profiling (PA-CEP) is fast, but has limitations on the traversability of the site conditions. When fourteen different electrode spacings are used the Lund Imaging System is four to five times slower than the PA-CEP system in an open terrain. However, using fourteen different electrode spacings the Lund system has a much higher vertical resolution. Furthermore, as experienced in Flaskebo, the Lund system works well in very rough terrain.

P- and S-wave characterization of near‐surface reflectivity from glacial tills using vertical seismic profiles

Fundamental reflectivity properties are established within the glacial deposits of central Saskatchewan, Canada. Multicomponent vertical seismic profile (VSP) data collected in three shallow boreholes are used to obtain detailed acoustic property information within the first 80 m of the near‐surface strata. The integration of both P- and S-wave VSP data, in conjunction with other borehole geophysics, provided a unique opportunity to obtain in‐situ seismic reflection response properties in layered clay and sand tills. P- and S-wave interval velocity profiles, in conjunction with P- and S-wave VSP reflectivities are analyzed to provide insight into seismic wavefield behavior within ∼80 m of the surface. In general, shear wave energy identifies more reflective intervals than the P-wave energy because of better vertical resolution for S-wave energy (0.75 m) compared to P-wave energy (2.3 m) based on quarter wavelength criterion. For these saturated, unconsolidated glacial deposits, more details about the lithologic constituents and in‐situ porosity are detectable from the S-wave reflectivity, but P-wave reflections provide a good technique for mapping the bulk changes. The principal cause of seismic reflectivity is the presence and/or amount of sand, and the degree of fluid‐filled porosity within the investigated formations.

Hydrogeology of a thick clay till and Cretaceous clay sequence, Saskatchewan, Canada

Clay-rich glacial till and Cretaceous clay are common throughout the Interior Plains of North America. Quantifying groundwater flow through these aquitards has implications for solute transport in aquitards and protection of underlying aquifers. Groundwater flow through a two-tiered aquitard system was investigated using laboratory and field methods at a test site in Saskatchewan, Canada. The aquitard system consists of 80 m of uniform, plastic clay-rich Battleford till (deposited 12-18 ka BP) disconformably overlying 77 m of late Cretaceous plastic marine clay (Snakebite Member, deposited 70-72 Ma BP). The upper 3-4 m of till is oxidized and fractured whereas the remainder is unoxidized. For the scales investigated, results suggested that hydraulic conductivity, K, is independent of scale for relatively thick till and clay bedrock deposits. Analysis of slug tests in the unoxidized till and laboratory tests on cores of unoxidized till yielded geometric mean K values of 5.4 × 10-11 and 2.7 × 10-11 m/s, respectively. Laboratory K tests of clay samples yielded a geometric mean K of 4.3 × 10-12 m/s. Bulk K of the clay was estimated to be 2.3 × 10-12 m/s assuming steady-state flow through the till and clay. The present-day groundwater velocity through the aquitard system was estimated to be between 0.5 and 0.8 m/10 ka downward based on the measured K values, measured hydraulic gradients, and measured porosities. Results suggested that pore water in much of the till was introduced during or shortly after glaciation.Key words: hydrogeology, aquitards, Cretaceous clay, Battleford till, hydrogeologic properties, geotechnical properties.

Hydrogeology of a thick clay till and Cretaceous clay sequence, Saskatchewan, Canada

Hydrogeology of a thick clay till and Cretaceous clay sequence, Saskatchewan, Canada

Drilling, Sampling, and Construction of Monitoring Wells Under Flowing Artesian Conditions

Research Article| January 01, 1997 Drilling, Sampling, and Construction of Monitoring Wells Under Flowing Artesian Conditions GARY D. ROGERS; GARY D. ROGERS Applied Geosciences and Engineering Inc., 405-A Parkway Drive, Greensboro, NC 27401 Search for other works by this author on: GSW Google Scholar DANIEL R. MOORE DANIEL R. MOORE Joyce Engineering, Inc., 436 Spring Garden Street, Greensboro, NC 27401 Search for other works by this author on: GSW Google Scholar Author and Article Information GARY D. ROGERS Applied Geosciences and Engineering Inc., 405-A Parkway Drive, Greensboro, NC 27401 DANIEL R. MOORE Joyce Engineering, Inc., 436 Spring Garden Street, Greensboro, NC 27401 Publisher: Association of Environmental & Engineering Geologists First Online: 09 Mar 2017 Online Issn: 1558-9161 Print Issn: 1078-7275 © 1997 Association of Engineering Geologists Environmental & Engineering Geoscience (1997) III (3): 369–373. https://doi.org/10.2113/gseegeosci.III.3.369 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation GARY D. ROGERS, DANIEL R. MOORE; Drilling, Sampling, and Construction of Monitoring Wells Under Flowing Artesian Conditions. Environmental & Engineering Geoscience 1997;; III (3): 369–373. doi: https://doi.org/10.2113/gseegeosci.III.3.369 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Drilling and sampling in flowing artesian aquifers is significantly more complex than in unconfined aquifers, especially in settings such as dam sites and hazardous waste sites where flow of water from the aquifer can cause safety or contamination problems. Successful drilling in flowing artesian conditions requires four items: properly weighted drilling fluid, inflatable packers, surface casing cemented in place, and driven casing. The primary control used to counteract the upward flow of water and thus prevent flow at the surface is drilling fluid of sufficient density. If the borehole begins to flow during drilling, the other three items are necessary to regain control of the flow. The packer can be used to stop the flow so that drilling fluid can be replaced under no-flow conditions. The surface and driven casings prevent erosion of the borehole walls if artesian flow occurs, and provide secondary locations for installation of a packer.When a boring has been drilled to the desired depth, monitoring well materials may be placed in the hole. These materials consist of a well screen, an inflatable packer, and riser pipe. The well materials are lowered through the drilling fluid into the boring, and a packer attached to the well riser pipe is inflated against the confining bed above the aquifer. Drilling fluid is flushed from above the packer with clean water, which is subsequently displaced with cement grout using a tremie pipe. After the grout has hardened, the drilling fluid can be flushed from inside the well riser and screen. The well can be developed by surging, followed by a period of free flow to remove drilling fluid from the aquifer.These techniques were used to successfully install a number of monitoring wells at a site in a river valley underlain by interbedded clay tills and outwash sand deposits of glacial origin. The deeper sand deposits were confined aquifers, with the clay tills acting as confining beds. Once the clay till was penetrated during drilling, flowing artesian conditions would have occurred unless proper drilling techniques were used. Soil sampling and installation of monitoring well materials would not have been possible under flowing conditions, necessitating the special procedures and equipment for drilling, sampling, and well installation. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Origin and physical and chemical characteristics of glacial overburden in Essex and Kent counties, southwestern Ontario

The overburden of Essex and Kent counties, southwestern Ontario, has been described as consisting of a clayey silt to silty clay till overlying a gravelly unit resting on bedrock. Recent Quaternary geology mapping has identified additional materials and redefined the origin of others by determining the stratigraphic position and physical and geochemical properties of materials encountered in a sonic drilling program and field mapping. Catfish Creek Till was deposited on the bedrock surface during the Nissouri Stadial as ice advanced south over the area. As ice retreated during the Erie Interstade, fine-grained glaciolacustrine material was deposited in glacial Lake Leverett and overlay Catfish Creek Till. Tavistock Till was deposited over glacial Lake Leverett material as the Huron lobe readvanced south during the Port Bruce Stadial. As the Huron lobe retreated north, coarse-grained glaciolacustrine materials were deposited in the Leamington area. Ice from the Erie lobe deposited the Port Stanley Till along the north shore of Lake Erie in Kent County and deflected meltwater southward from the Huron lobe in the Blenheim area. A series of recessional moraines were deposited by the Huron lobe as it retreated north. The area is capped by a fine-grained glaciolacustrine deposit.

Stress-dependent flow through fractured clay till: a laboratory study

Stress-dependent hydraulic conductivities of weathered fractured clay till were measured in a flexible-wall permeameter. Measured conductivities were in the range 10–7 to 10–8 cm/s, of the same order as the clay matrix (10–8 cm/s), and representing equivalent hydraulic apertures in the range 0–5 μm. In general, the isolated fractures exhibited strongly nonlinear closure characteristics and hysteric behaviour under stress reversal. Some fracture samples exhibited only weak stress dependency, representing observable features of only nominal conductivity. Results of the investigations suggest fractures are closed to residuel aperture for an overburden load of the order of 12 m, this defining an effective closure depth and the degree of maximum useful compactive effort that might be applied to "seal" fractures and reduce fluid migration. Key words: fracture permeability, till, stress permeability, landfills.

STOREBAELT EASTERN RAILWAY TUNNEL: CONSTRUCTION.

Keywords AS STOREBAELTFORBINDELSEN, MT GROUP, MONBERG & THORSEN, DYCKERHOFF & WIDMANN, CAMPENON BERNARD, SOGEA, KIE TUNNELS, RAILWAYS, CONSTRUCTION, BORING, CROSS PASSAGES, HAND, MINING, METHODS, CUT AND COVER, CIVIL ENGINEERING, WORKS, GEOLOGY, WATER, PRESSURE, EARTH, BALANCE, MACHINES, MACHINERY, TBM, TUNNELLING, MODIFICATION, UNDERSEA, SUBMARINE, DEWATERING, CRYOGENICS, FREEZING, JUNCTIONING, GLACIAL, TILL, GROUND, TREATMENT, ONSITE, MANUFACTURING, HIGH, STRENGTH, DURABILITY, CONCRETE, LININGS, EPOXY, COVERED, COATED, REINFORCEMENT, CAGES, PROJECTS, MANAGEMENT, CONTRACTS, BORED, JOINT VENTURES, BEHAVIOUR, ALIGNMENT, SURVEYS, MUCK, DISPOSAL, SEABED, WATER, CON STOREBAELT, EASTERN DENMARK, SCANDINAVIA... Show All

STOREBAELT EASTERN RAILWAY TUNNEL: DESIGN.

This paper describes the design of the 8km long eastern railway tunnel of the Storebaelt (Great Belt) crossing in Denmark. Conceptual design was carried out in 1986, and several options were considered. Tender design was conducted in 1987-88, for two tunnel options. The contract was awarded for the bored tunnel option, designed by the Mott McDonald Group. The structures include: (1) earthworks, approach ramps, and cut-and-cover tunnels at each end; (2) twin 7.7m diameter circular bored tunnels; and (3) 31 4.5m diameter cross passages for equipment and emergency evacuation purposes. Site investigations showed complex ground conditions; the rocks include: glacial clay tills with layers of silt and sand, marl with fissured and jointed zones, and boulders of granite and gneiss. In anticipation of these geological conditions, four sophisticated earth pressure balance machines (EPBMs) were specified for the tunnel boring. The design of the main components of the project, including the mid-point drainage sumps, is discussed. For the first time in the tunnelling industry, it was decided to use fusion-bonded epoxy-coated reinforcing cages for the precast concrete segmental tunnel linings. Two-dimensional finite element ground/lining analyses were conducted for the main tunnel lining.

Field performance of thin wall foundations

The feasibility of building residential basement foundation walls of unreinforced concrete thinner than the conventional 200 mm thick wall is investigated. An optimum thickness of 150 mm was determined for an unreinforced 2400 mm high foundation wall based on the use of equivalent fluid pressures with sand and gravel backfill material. For walls backfilled with other than clean sand and gravel, or with a submerged condition, it was found that the theoretical maximum backfill heights for both 150 and 200 mm walls are substantially less than those presently specified by the Alberta Building Code. The primary purpose of the study described in this paper was to test under actual field conditions the performance of a 150 mm unreinforced concrete wall under varying lateral loads imposed by different soil types, and to compare measured and calculated lateral loads with the equivalent fluid pressure specified as a criterion in the Alberta Building Code. The lateral earth pressures resulting from the backfilling of 150 mm thick concrete foundation walls were investigated for two backfills, namely sandy lean clay (clay till) and sand. The findings indicate that for longer term placement conditions, the resulting pressure distribution supports the hypothesis of a triangular soil pressure distribution and can be described using traditional earth pressure theory. Two design methods based on the concept of equivalent fluid density were evaluated and compared with the field measurements. Key words: thin wall foundations, earth pressure, field measurement.

Disturbance effects on herbaceous layer vegetation and soil nutrients in Populus forests of northern lower Michigan

Abstract. Recent disturbance models have identified changes in resource availability as factors that control plant community response. Soil nutrient resources typically are assumed to change following forest disturbance, usually with nutrient availablity increasing initially and subsequently decreasing through later stages of succession. We examined the effects of disturbance (clearcut harvesting with a brief recovery period) on soil organic matter, pH and extractable soil nutrients in successional aspen forests of northern lower Michigan to determine relationships of these variables to changes in herbaceous layer vegetation. Two site types were identified: drymesic (glacial outwash sands, low in organic matter) and mesic (calcareous clay till, high in organic matter). Extractable nutrient concentrations were 1.5 to 3 times higher in the A1 horizon of mesic sites than those of dry‐mesic sites. Soil pH and cations increased after disturbance on mesic sites, but not on dry‐mesic sites. Patterns of change with disturbance were less pronounced in lower horizons on both site types. Herblayer species diversity increased after disturbance on mesic sites, but with decreases in the importance of shade‐tolerant tree species and Maianthemum canadense. Species characteristic of open habitats (e.g. Pteridium aquilinum, Rubus spp., Fragaria virginiana, and Diervilla lonicera), increased in importance. Soil factors, species composition and diversity on dry‐mesic sites changed little after disturbance, with Pteridium aquilinum and ericaceous species remaining dominant in both mature (55–82 yr) and disturbed (≤ 15 yr) stands.These results suggest that soil nutrient resources do not always change through secondary succession and that patterns of change can be distinctly site‐dependent. Disturbance response patterns in the herbaceous layer of these aspen forests are also site‐dependent.

Landforms and structures of the waterlain west end of St. Thomas moraine, SW Ontario, Canada

The western part of St. Thomas moraine was deposited by the Erie lobe terminating in Lake Maumee II during the Bruce stadial of the late Wisconsinan. The marginal 5 km wide zone of the Erie lobe became stagnant in the relatively shallow (15–20 m) part of the lake. Crevasse fillings, in the form of hundreds of slightly curved ridges were deposited as mesoforms upon the 5 km wide and 10 m high morainic macroform that consisted of Port Stanley basal till. Most crevasse fillings trend N-S, and consist of stratified pebbly sand deposited upon silty clay till, squeezed up by the load of the ice blocks from the macroform underneath. A couple of the till ridges were overthrusted eastward. This overthrusting was accomplished probably by wind-driven ice blocks at the time when lake level rose by about 7 m from Lake Maumee II to Lake Maumee III. The stagnant ice blocks did not melt out until after Lake Whittlesey time. South of the southwestern end of the St. Thomas moraine at Wallacetown, the area is flat, without any morainic landforms, gently sloping for about 7 km as far as the Lake Erie bluffs. About 7 km south of Wallacetown natural exposures along creeks and lake bluffs reveal the northern edge of an erosional depression cut at least 20 m deep into the Port Stanley Drift and covered by glaciolacustrine sediments. Two small morainic ridges, each of them about 10 m high and about 1 km wide, are exposed in lake bluffs at the extension of the St. Thomas moraine on land. The lower one consists of Port Stanley basal till, the upper one of “waterlain till” and glaciotectonically deformed glaciolacustrine sediments. The erosional depression was cut probably by an ice stream that was more active than the rest of the Erie lobe, and the buried morainic ridges are probably contemporaneous with the St. Thomas moraine.

Field experiments in a fractured clay till 2. Solute and colloid transport : L. S. McKay, R. W. Gillham & J. A. Cherry, Water Resources Research, 29(12), 1993, pp 3879–3890

Field experiments in a fractured clay till 2. Solute and colloid transport : L. S. McKay, R. W. Gillham & J. A. Cherry, Water Resources Research, 29(12), 1993, pp 3879–3890

Field experiments in a fractured clay till: 2. Solute and colloid transport

A field tracer experiment was conducted in a lateral flow field in the weathered and highly fractured upper 6 m of a 40‐m‐thick clay‐rich till plain in southwestern Ontario. In the upper 3 m where fractures are closely spaced (<0.13 m) the advancing front (C/C0 = 0.01) of the nonreactive solute tracers, bromide and 18O, migrated at rates of 0.01 to 0.07 m/d, over distances of 4 and 6 m and under a lateral hydraulic gradient of 0.24. In this same zone, two strains of colloid‐sized bacteriophage tracers migrated at rates of 2 to >5 m/d. Simulations with a discrete fracture/porous matrix flow and transport model, which used the cubic law for flow in fractures, showed that diffusion of the solutes, but not the much larger colloids, into the matrix pore water between fractures is sufficient to cause the observed difference in solute and colloid transport rates. Transport‐derived and hydraulic conductivity‐derived fracture aperture values were similar, within a factor of 3 and falling mainly within a range of 5–40 μm. In the upper 3 m the solute tracers were evenly distributed between pore water in the fractures and the matrix, and as a result, solute transport can be closely approximated with an equivalent porous medium (EPM) approach. Below this depth, fractures are more widely spaced (0.13 to >1 m) with concentration peaks tending to occur near visible fractures, and solute transport cannot be adequately described with an EPM approach.

Field experiments in a fractured clay till, 1. Hydraulic conductivity and fracture aperture : McKay, L D; Cherry, J A; Gillham, R W Water Resour ResV29, N4, April 1993, P1149–1162

Field experiments in a fractured clay till, 1. Hydraulic conductivity and fracture aperture : McKay, L D; Cherry, J A; Gillham, R W Water Resour ResV29, N4, April 1993, P1149–1162

A Comparison of Pumping and Slug Tests for Estimating the Hydraulic Conductivity of Unweathered Wisconsian Age Till in Iowa

AbstractThe low conductivity of glacial till is usually thought to preclude pumping tests, which has led to the predominate use of laboratory permeameter and single well response (slug) tests for estimating hydraulic conductivity. Slug tests only sample a small region around the well and may be more representative of the disturbance of well installation or development than in situ conductivity. To provide a larger scale comparison to slug test estimates of hydraulic conductivity for unweathered Wisconsin age till in Iowa, a pumping test was performed, with both the pumping and monitoring wells placed in unweathered till. Maintaining a constant drawdown of 439 cm in the pumping well for over five days yielded an average flowrate of only 26.3 ml/min, but produced a maximum drawdown of 104 cm at a radial distance of 178 cm. Assuming radial and vertical flow, least‐squares parameter estimation yielded a hydraulic conductivity estimate of 7.5 · 10‐7 cm/s and a specific storage estimate of 6.6 · 10‐6 cm‐1. Slug test results compared favorably, with geometric mean hydraulic conductivity estimates of 4.9 · 10‐7 cm/s from a Cooper et al. (1967) analysis and 7.1 · 10‐7 cm/s from a Hvorslev (1951) analysis. For this relatively low clay till (20% clay fraction), borehole smearing does not appear to have a significant impact on slug tests. The results indicate pumping tests can be performed, on an appropriate scale, in some unweathered tills.

Field experiments in a fractured clay till: 1. Hydraulic conductivity and fracture aperture

Field values of horizontal hydraulic conductivity measured in the upper 1.5–5.5 m of a weathered and fractured clay‐rich till were strongly influenced by smearing around piezometer intakes, which occurs during augering, and by the physical scale of the measuring device. Values measured in conventional augered piezometers were typically 1–2 orders of magnitude lower than those measured in piezometers designed to reduce smearing. Measurements of hydraulic conductivity in small‐scale seepage collectors or piezometers, which typically intersect fewer than 10 fractures, vary over a much greater range, 10−10 to 10−6 m/s, than large‐scale values based on infiltration into 5.5‐m‐deep trenches which intersect thousands of fractures (range 10−7 to 3×10−7 m/s). Values of hydraulic fracture aperture, 1–43 μm, and fracture porosity, 3×10−5 to 2×10−3, were calculated using the cubic law with fracture orientation/distribution measurements and the small‐scale hydraulic conductivity measurements. This paper provides the first reliable determination of the magnitude and spatial distribution of hydraulically derived fracture parameters in a clay deposit. The absence of such data has, until now, severely limited the application of quantitative groundwater flow and contaminant transport models in this type of deposit.

Observation and analysis of a failure in a cliff of glacial clay till at Cowden, Holderness : Butcher, A P Proc Conference on Slope Stability Engineering: Developments and Applications, Isle of Wight, 15–18 April 1991P271–276. Publ London: Thomas Telford, 1991

Observation and analysis of a failure in a cliff of glacial clay till at Cowden, Holderness : Butcher, A P Proc Conference on Slope Stability Engineering: Developments and Applications, Isle of Wight, 15–18 April 1991P271–276. Publ London: Thomas Telford, 1991

Investigations of the stiffness of a glacial clay till : Hird, C C; Powell, J J M; Yung, P C Y Proc 10th European Conference on Soil Mechanics and Foundation Engineering, Florence, 26–30 May 1991, V1, P107–110. Publ Rotterdam: A A Balkema, 1991

Investigations of the stiffness of a glacial clay till : Hird, C C; Powell, J J M; Yung, P C Y Proc 10th European Conference on Soil Mechanics and Foundation Engineering, Florence, 26–30 May 1991, V1, P107–110. Publ Rotterdam: A A Balkema, 1991