Quick Clay Research Articles

Quick clays of eastern Canada

This paper describes the results of research carried out during the past fifteen years on the quick clays of eastern Canada. The mineral composition and structure of these clays is similar to that of other glacial marine clays but they often exist with an unusually low salt content in the pore water. There is evidence of strong rigid bonds between particles of those deposits that are overconsolidated. The bonds are broken when the soil is loaded and this may lead to large volume changes or to exceptional loss of strength if drainage is not permitted. Some studies have been made on the physico-chemical characteristics of the soil and on its fabric but most of the research to date has involved laboratory and field observations of the response of the soil structure to stress changes. The important influence of rate of loading has revealed the need of careful interpretation of laboratory tests for field application.

Settlement of a Furnace Foundation, Sorel, Quebec

The Smelter of Quebec Iron and Titanium Corporation at St. Joseph de Sorel, Quebec, is located in an area which is underlain by about 80 feet of compact stratified sand, silt, and clay, followed by at least 150 feet of Leda clay. Five furnaces were constructed during 1950–52, and four more furnaces have been added subsequently. Settlement records spanning some fifteen years are available for the original furnaces.Recently, it was decided to replace No. 1 Furnace with a new unit, the weight of which will be slightly more than twice that of the existing furnace. The present furnace is founded on 32 Franki piles of 75 tons capacity; the piles are 22 feet long and are cut off about 5 feet below ground level. As it was desired to incorporate the existing piles in the foundation for the new furnace it was necessary to know whether new piles could be driven and loaded together with the existing piles without causing overstressing of the latter, which had been preloaded by the weight of the existing furnace.A settlement analysis of the existing furnace foundation was undertaken, in which sensible agreement was obtained with the observed settlements. Predictions of the rebound of the existing furnace foundation during demolition were made and these were in approximate agreement with field observations. Finally, an estimate of the settlement which the new furnace will experience was made.A significant feature of the problem is that a large portion of the total settlement experienced to date is due to consolidation of the underlying Leda clay stratum, despite the fact that the furnace foundation areas are small in size compared to the thickness of the overlying granular deposits, thereby inducing only small increases in pressure in relation to the existing overburden pressure.

Settlement of an Embankment on Leda Clay

Before construction, standard consolidation tests indicated that the stresses imposed by a high embankment on a deep and relatively homogeneous deposit of Leda clay would exceed the preconsolidation stress and result in settlements of up to 18 in. Later, the results of more refined sampling and testing methods showed that the preconsolidation pressure had been underestimated by 1 ton/sq. ft. and that the imposed stresses would in fact fall within the recompression range. Time-settlement relationships, however, were not elastic; vertical strains continued to increase long after the embankment was completed. Field measurements of settlement are compared with values computed using compression moduli determined both from consolidation and compression tests in the laboratory.

Settlement Observations at Kars Bridge

A 26 ft. high approach fill was constructed in November 1959 for a bridge over the Rideau river near Kars, Ontario. The fill was placed over 50 ft. of Leda clay, the lower 30 ft. of which was extremely sensitive and compressible. Prior testing indicated that the preconsolidation pressure of the clay would be exceeded.Settlement gauges and piezometers under the fill have been observed since the start of construction. After 7½ years, 20 in. of settlement has occurred under the centre of the fill. Settlements are continuing at an appreciable rate although the excess pore water pressure has dissipated to a low level and is nearly constant through the clay layer.The field observations of settlement and pore water pressure are compared with values calculated and a closed form solution to the process of consolidation obtained by a heat balance integral technique and by considering the clay layer to be a rigid plastic.

Application of Electro-Osmosis to a Foundation Problem in a Norwegian Quick Clay

Synopsis The Paper describes a case where the application of electro-osmosis resulted in an increase in strength of a very soft quick clay from an initial value of less than 1 t/m2 to an average value of 4 t/m2. Based on observations made during treatment and at the excavation site, an attempt is made to give a picture of the effect of electro-osmotic treatment on a soft clay. The observations include measurements of settlements and pore pressures at various depths and studies of the change in properties of the clay resulting from the treatment. On décrit une application d'électro-osmose. La résistance au cisaillement d'une argile très fluide a augmenté de 1 t/m2 à une valeur moyenne de 4 t/m2. On discute les effets électro-osmotiques sur la base des observations Qu'on a fait uendant le traitement électro-osmotique et des invetigations des échantillons qu'on a prit pendant l'excavation. On a mesuré des tassements et des pressions de l'eau interstitielle aux profondeurs variés, en même temps qu'on a étudié les changements de propriété de l'argile dû au traitement électro-osmotique.

Some Problems on Mass Movements

A hard and fast classification of mass movements can neither be given nor make sense, because its practical application to the actual or natural phenomena encounters great difficulties. For the time being a simplification is preferable to pining for a too detailed classification of mass movements. This paper is chiefly concerned with clay minerals in areas of mass movements of flowand slip-type in Canada, compared with those in Scandinavia and in Japan, and it stresses the important role of swelling clay minerals. Classification of mass movements The classification of types of mass movements proposed by Sharpe (1938, pp. 97, Fig. 14) is well-known, and it appears to be very comprehensive and nicely systematic. However, it has neither any standard measure nor scientific criterion; and thus conscientious researchers must have been sorely perplexed in its application to their own studies. In this connection, a much better classification of landslides has been recently presented by Varnes (1958, pp. 20-47). The writer (Yatsu 1966, pp. 102-103) has proposed a tentative classification of mass movements which emphasized only the mechanics of the phenomena and ignored shapes and so forth, since it is doubtful whether complicated classifications are of any practical use at all. The most important task at present is to clarify the mechanism of movement in individual cases which will then be assigned to one type or a transitional type of fall, creep, rupture, slip, flow, and others. Generally speaking, falls, creeps, and ruptures are observed everywhere under certain conditions irrespective of rock types, while slips and some of the flows seem to be conspicuously associated with materials of which the slopes are composed, especially with the type of clay minerals. Clay minerals in areas of slipand flow-types of mass movements Slips or landslips, presumably most closely corresponding to earthflows in Sharpe's classifica396 tion of types of mass movements, have a remarkable relationship to swelling clay minerals and occur on slopes more gentle than those of lope ruptures which occur withouttheexistence of clay minerals. The results of studies on this problem in Japan (Nakano, Yatsu and Teruta 1961, pp. 1-20; Yatsu 1964, pp. 7-30; Yatsu 1965, pp. 54-66) will now be compared with those in Canada and in Scandinavia. In eastern Canada, most mass movements of flow-type, called flowslide by civil engineers, have occurred in the valleys of the Ottawa and the St. Lawrence rivers where extrasensitive quick clays are observed. Also in British Columbia and in the Prairie Provinces, mass movements of slipor flow-type are frequently observed in glacial till deposits. The writer has observed mass movements of flow-type near Lakelse Lake, B.C. and near Pavilion, B.C.; and those of slip-type at Spences Bridge, B.C., and near Hixon Station B.C., (about 1.5 miles north of the station along the railway). Many slope ruptures are observed, of course, along the Fraser River which erodes the tips of the slopes and causes their occurrence. Concerning the clay mineralogy of Canadian soils, Forman and Brydon (1961, pp. 140-146) have reviewed and have mentionedthe existence of montmorillonites in prairie soils. Kodama and Brydon (1965, pp. 151-173) have reported interstratified montmorillonite-mica clays, and Maiklem and Campbell (1965, pp. 354-371) studied mixed layer clays of the Prairie Province. In Leda clay from eastern Canada, clay fractions have been examined and show a predominant composition of illite and chlorite with occasional traces of montmorillonite (Allen and Johns 1960, pp. 75-86; Brydon and Patry 1961, pp. 169-181). The X-ray identification of clay minerals was done on several samples collected from mass movement areas of flowor slip-type in British Columbia and around Ottawa, and also on Scandinavian quick clays. Some examples of This content downloaded from 157.55.39.175 on Sun, 02 Oct 2016 05:41:26 UTC All use subject to http://about.jstor.org/terms SOME PROBLEMS ON MASS MOVEMENTS

Chemical aspects of quick-clay formation

In connection with the systematical examination of the slope stability in the Go¨ta River Valley in Sweden it was impossible to get a satisfactory explanation of the cause of the high sensitivity of quick clays which could be used in the continued examination as a basis for geotechnical investigations. It was concluded that the quick-clay problem must be regarded as a problem of colloid chemical nature. Many of the results obtained pointed out the fact that the surface properties of the grains will play an important role, and in this connection the problem with the possible existence of surface-active agents (dispersing agents) in natural quick clays has been studied. Systematic isolations of dispersing agents have been made by different methods, and the subsequent extracts have been analysed chromatographically. It is found to be easy to isolate dispersing substances by most of the methods tested, but it is very difficult to find any substances with a known composition. Instead, this part of the examination will approach the humic problem. In one case it has been possible to break up the complexes into individual components of known composition, i.e., in the case of fatty acids and soaps. Quick clay contains homologuous series of normal saturated fatty acids and for this reason soaps seem to be components which contribute to the quick-clay formation.

Norwegian research into the properties of quick clay—a review

The ultra-sensitive type of clay called quick clay has caused severe landslides in Scandinavia and on the east and west coast of Canada. Slides of this type were the mentioned in literature in the fourteenth century. Quick-clay properties were described in 1901. Later geologists at the Norwegian Geological Survey, the Norwegian Highway Laboratory and the Norwegian Geotechnical Institute carried out research on this material. The present opinion is that the peculiar properties are based upon colloidal-chemical phenomena. According to this the clays deposited and consolidated in a flocculated state. Later chemical changes increased the double layer potential, either by leaching of electrolyte or by addition of suitable anions. The flocculated structure remains, unstable though, until mechanical disturbances cause a breakdown. Thus the clay is transformed into a dispersed state.

Quick-clay microstructure

The article deals with a quick clay which was originally deposited in sea water. By leaching in situ the salt content has been reduced to a very small value. By using a special technique for step-wise replacement of pore water with acrylate plastic, 500A˚thick sections were cut with a precision microtome. The sections were photographed in an electron microscope and the micrographs obtained could be used for a study of the clay microstructure. The microstructure is characterized by a linkage of groups or chains of small particles in and between denser flocs or aggregates or between bigger particles. There is no preferential orientation either of small or of bigger particles. A preliminary study of the quick clay and of unleached parts of the same clay stratum has not revealed any microstructural differences. The extreme thinness of the clay sections means that the micrographs reveal pores larger than about 500A˚. Thus the micrographs give a fairly complete picture of the size and shape variation of the micropores in the clay. By measuring the maximum dimension of all pores which could be identified and by using suitable methods for statistical condensation, representative values of mean pore size and two-dimensional “porosity” were obtained. These characteristics are discussed in relation to the permeability and strength properties of the quick clay and of some fresh- and brackish-water deposited clays which have been investigated previously. Finally, on the basis of the micrographs a hypothesis is made concerning the rate of settlement.

The Fabric of Anisotropically Consolidated Sensitive Marine Clay

The relationship between soil fabric and the anisotropic consolidation characteristics of a sensitive, highly flocculated marine clay has been studied using x-ray diffraction techniques. Measurements of the clay particle parallelism (fabric) were performed on “undisturbed” and remoulded samples of Leda clay from Ottawa, Canada, in an attempt to determine the influence of sample disturbance on soil fabric and laboratory consolidation test results.The amplitudes of the 10 Å clay peaks of the “undisturbed” natural clays, measured in the major principal plane, increased from about 11 counts/second at low consolidation pressures to about 40 counts/second at 64 tons/sq. ft. This is interpreted as resulting from reorientation of many of the clay platelets into the plane perpendicular to the direction of the consolidation pressure. An abrupt reorientation occurred when the pre-consolidation pressure was exceeded.Remoulding the clay apparently causes a marked breakdown of the interparticle bonds as evidenced by stronger 10 Å peaks and inferred greater particle parallelism at any given consolidation pressure within the range studied. This increase in parallelism is associated with a pronounced reduction in void ratio when compared with the “undisturbed” clay.

Direct Simple-Shear Tests on a Norwegian Quick Clay

Synopsis The Paper gives a short description of a recently developed direct simple-shear apparatus. The cylindrical sample (diameter 8 cm, height 1 cm) is confined in a reinforced rubber membrane allowing vertical deformations and horizontal displacements with no change in diameter. Consolidated constant-volume shear tests showed shear strengths which were lower than those found in comparable triaxial tests. The ratio of the constant-volume shear strength to vertical consolidation pressure with the new equipment was found to be 0·18 compared with 0·29 measured in the triaxial tests and 0·13 found by vane tests in situ. The drained tests on samples consolidated at a pressure equal to the overburden in the field indicate that the structure of the clay might be stable for small shear stresses but starts to collapse at a certain critical value. This phenomenon might contribute to explain some landslides which have occurred in slopes in quick clay at a shear stress much below the ultimate drained shear strength. Cet article décrit brièvement un appareil de cisaillement simple direct développé récemment. L'échantillon cylindrique (8 cm de diamètre, 1 cm de hauteur) est placé dans une membrane en caoutchouc renforcée permettant des déformations vertitales et des déplacements horizontaux sans changer le diamètre. Des essais de cisaillement sous volume constant sur échantillon consolidé ont indiqué des résistances au cisaillement inférieures à celles qui ont été constatées dans des essais triaxiaux parallèles. Le rapport de la résistance au cisaillement sous volume constant a la pression de consolidation vertitale s'est révélé de 0,18 avec le nouvel appareil, comparé à 0,29 mesuré dans des essais triaxiaux et 0,13 relevé dans des essais á moulinet in situ. Les essais drainés sur des échantillons consolidés à une pression égale à la surcharge sur le terrain indiquent que la structure de l'argile peut être stable pour de petits efforts de cisaillement mais commence à s'affaisser à une certaine valeur critique. Ce phénomène peut contribuer à expliquer des glissements de terrain s'étant produits sur des pentes d'argile fluide pour des efforts de cisaillement bien inférieurs à la résistance au cisaillement drainé finale.

A STUDY OF SENSITIVITY IN LEDA CLAY

The sensitivity of Leda clay from the Ottawa area is relatively independent of the salt content in the pore water. Sensitivity values may vary between 10 and 1 000 in the low salt content range (less than 2 g/liter); at higher salt contents strong flocculating effects of the electrolyte limit the sensitivity, but values as high as 75 have been measured.A relationship has been determined experimentally between electrokinetic potential and sensitivity that is consistent with the theory of interparticle repulsion and attraction. The main deviations are attributable to differences in grain size.Chemical analyses of pore water show that large variations in sensitivity, particularly within one profile, are related to the nature of the pore water electrolyte in the low salt content range. Soils that are unusually sensitive have a high monovalent cation content. Large differences in sensitivity can be accounted for in this way, but the reason for small variations is still obscure.The electroosmosis technique used to determine electrokinetic potentials is discussed in detail. This apparatus was used also to verify Rosenqvist'a leaching theory of sensitivity for soils known to have had a marine origin.

Shrinkage of Soil Samples with Varying Clay Concentration

The influence of texture on shrinkage was studied for samples prepared in the laboratory to have varying proportions of Leda clay and glass beads. Total shrinkage and moisture content at the shrinkage limit increased linearly with the percentage of clay as long as the clay formed a continuous matrix. At lower clay concentrations shrinkage decreased rapidly. Total shrinkage per unit weight of clay in the mixtures increased with decreasing clay content, because the clay in parallel orientation around glass beads had a higher moisture content than the remainder of the clay.

Observations on Quick Clay

Certain glacial and postglacial clay strata, long static in almost flat terrain, with little or no warning may flow spontaneously with destructive consequences. Samples of such clays, known as “quick clays,” have been examined from Scandinavia, Canada, and the northeastern United States. These have been compared with similar clays in areas where quick-clay movement has not been reported. The principal minerals in the clay-size fraction of the quick clays observed are sheet-layer silicates. Illite (hydromica) and chlorite occur most frequently, interlayered illite-montmorillonite is common, interlayered chlorite-montmorillonite occurs occasionally, and interlayered illite-vermiculite was found in one sample. Quartz, feldspar, hornblende, and calcite predominate in the coarser-size fractions and are found to some extent in the clay-size fractions. Most of the clays examined are of marine origin, but one of established fresh-water origin was included. The quick clays contain an average by weight of 57.3 per cent less than 2-μ. material, and the nonquick clays average 31.6 per cent less than 2-μ material. Chlorinity tests indicate that pore-water salinity of marine quick clays, about 35 g per 1 when deposited, becomes 0.2–15 g per 1 at flowage. The pore-water content of quick clays noted exceeds 44 per cent and in some clays may be as high as 80 per cent. Major critical conditions which contribute to quick-clay movement appear to be: substantial quantities of layer-lattice silicates of colloidal size (about 40 per cent or more by dry weight), substantial pore water (44 per cent), a reduction in electrolyte concentration below 5 g of salt per 1, and the addition of a dispersant. Under such conditions a clay becomes critically sensitive and may flow spontaneously or as the result of a shock. In quick clay of marine origin it has been suggested that a random orientation of clay particles is probably induced by coagulation during deposition. This orientation appears to provide stability to such clay strata. Removal of an electrolyte by natural leaching with fresh water appears to render the clay unstable. When the clay structure undergoes collapse, flowage is believed to result. Field conditions suggest that flowage of non-marine quick clay may be attributed to the action of a dispersant such as humic acid.

Studies of Sensitivity and Electro-kinetic Potential in Leda Clay

IN a previous communication1, an anomalous difference was pointed out between two supposedly similar geological deposits from widely separated regions of the world. Whereas a relationship between sensitivity (the ratio of undisturbed shear strength to remoulded shear strength) and pore-water salt concentration has been reported for some Norwegian marine soils, this was not true for Leda clay from the Ottawa–Hull area in the St. Lawrence Lowland region of eastern Canada.

Calibration of a Neutron Moisture Meter in Leda Clay

A neutron moisture meter using a scintillation detector for slow neutrons was previously calibrated in materials carefully selected to avoid inaccuracies resulting from neutron absorption. Preliminary readings of moisture density in the field using this calibration, however, were not in agreement with values obtained by auger borings. Consequently the instrument was recalibrated; in the laboratory using samples of remolded Leda clay; and in the field, by taking readings throughout a summer in the natural material. Details of moisture content and density control are described. The new calibration curve is parallel to the original one, but considerably displaced from it by what appears to be a neutron absorption effect. Chemical analyses of the clay and pore water failed to detect any elements whose capture cross-sections for neutrons are large. They did however indicate a high percentage of iron whose capture cross-section is a little larger than those for elements occurring naturally in mineral soils. Although further research is required for confirmation of this observation, results of preliminary experiments point primarily to the presence of iron in quantities large enough to explain the discrepancy between the two calibration curves.

Infiltration av ytvatten i lera och därmed sammanhängande hållfasthetsförändringar

Abstract In 1934 geotechnical analyses were carried out in the Timrå area (15 km north of the city of Sundsvall, Northern Sweden). 27 years later, in 1961, new analyses were made. The results in 1961 gave lower H1‐values (the shearing resistance of the remoulded sample) than those obtained in 1934. The clay had become quick. Control analyses were made in the laboratory. The dried residue from the interstitial water of the quick clays was able to lower the H1‐values of non‐sensitive glacial clays. The dried residues of the sensitive and non‐sensitive clays of the Timrå area were X‐rayed, and it was found possible to distinguish the different types of water. Some organic substances were examined, and it was found that non‐sensitive postglacial clays gave low H1‐values when treated with chemicals extracted from bark with distilled water. This might be one of the explanations for the slides in the Ådalen where some recent slides have their slip surfaces just below organic material, for instance, bark and wood.

The Modulus of Elasticity of Leda Clay from Field Measurements

The construction of the Ottawa Sewage Treatment Plant provided an opportunity to measure bottom heave in two large excavations in clay. With gauges installed prior to excavation, elastic heave, swelling, and heave due to pile driving were measured in an excavation 31.5 ft. deep. Using a Poisson's ratio of 0.4, the modulus of elasticity determined from field measurements compared favourably with the initial tangent modulus from the best unconfined compression strength tests. In the other excavation a drop in the ground water table produced an elastic settlement that exceeded the elastic heave resulting from unloading by excavation.

Studies on the Properties and Formation of Quick Clays

AbstractIn a natural clay, the occurrence of a high sensitivity, i.e. a high quotient between the shear strength of the undisturbed and remolded soils respectively, under undrained conditions, is connected to thixotropic effects and to “quickness”.The general composition of the soils in which quick clay occurs is described, and mention is made of the occurrence of non-argillaceous rock fragments in a matrix of clay particles. Mite is the main clay mineral. Quickness occurs both in salt-leached, marine deposited clays and in clays deposited in fresh water. The pore water of these clays is low in electrolytes and undecomposed organic material. It is found that quick clays often occur near peat and similar humic deposits. Also briefly discussed is the internal stress distribution in natural clays under various consolidation conditions, the structure of quick clays and their conditions of formation. The consistency of clays is considered, as is the stability and coagulation conditions of suspensions. This is followed by a commentary on physico-chemical effects contributing to the formation of quick clays under natural conditions, and a discussion of the salt-leaching theory and the theory on the effect of peptizing agents.In the discussion, the author draws parallels between the coagulation and the thixotropic phenomena, and between the stability and dispersion of suspensions and the quickness.

Sensitivity in Leda Clay

Sensitivity in Leda Clay