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The study was intended to elucidate by HCl extraction the composition of that part of the clay fraction, essential for adsorption phenomena in the soil and also its resistance to attack by HCl.HCI extraction of 12 alluvial clay soils did not indicate the composition of the adsorption complex, as the analyses of the HCl extracts showed very different values for the composition of the Al-Fe-Si-complexes which were brought into solution, whereas the values for adsorption and residual adsorption showed that the chemical composition of the adsorptive parts of the clay fraction < 2μof the different soils was uniform.The uniformity of the clay fractions of the 12 soils in adsorption capacity, behaviour towards HCl extraction and the influence of this extraction on adsorption values suggested that the soils could be of the same mineralogical origin. However total analyses of the clay fraction yielded divergent SiO 2 : Al 2 O 3 and SiO 2 : sesquioxide ratios for the different soils.Therefore it was supposed that only the films of the hydrolytic products of the minerals present in clay were identical.

Stiboka research

Quantitative analysis of soil elay minerals after X-ray, differential thermal, infrared, cation exchange and chemica! analysis is treated. Partiele size, crystallite size, the grade of structural ordening in the minerals, and the surface being covered by an amorphous (Beilby) layer, have large influence on the results. Examples are given.

The parallel alignment of particles causes clay sediments to be anisotropic to thermal conduction. In marine sediments with a flocculated structure the anisotropy is small, while in fresh water clays that have a regular alignment of clay particles it is shown to be large. The anisotropy was shown to be related to particle alignment by comparing it with shrinkage results and particle orientation observed in thin sections. The sensitive relationships between anisotropic thermal conduction and particle arrangement are useful for investigating soil structure and because of this the transient heat flow method used is described in some detail.

A practical problem initiated this study. In the Haarlemmermeer, a former lake reclaimed about 1850, several farmers had difficulties with soil structure. Land, plowed in autumn, was very wet in spring. Free water was sometimes present on the soil surface. Planting and seeding were long delayed in spring and yields were unsatisfactory because of irregular crop development.Some farmers ascribed it to pressure from the back wheel of the tractor in the open furrow during plowing, compacting the subsoil and severely reducing permeability. Plowing practices were therefore changed. Equipment was used that could be moved by driving the tractor with all four wheels over the normal soil surface. This sometimes needed very old horse ploughs, adapted to tractors. Other farmers tried to improve drainage by laying more tile drains alongside existing systems, but usually the drains did not conduct water.The problems occurred on several soil types, but especially on the somewhat lighter textured sandy loams of the Hoofddorp Complex (Pgb) (Haans, 1954).The Agricultural extension service helped in the selection of two farms, where a pedon was selected. In one, henceforth called G, no problems occurred. In the other, called B, soil structure had deteriorated. Morphological and physical properties of each pedon were frequently investigated for about 18 months. Soil management was left to each farmer. Profile descriptions, particle size distributions and routine analytical data of each pedon are in Appendix I. Differences in these values between the two profiles are mainly a result of soil management.Originally the carbonate content of Pedon G was very low throughout. The content of 1%, as found now in the surface soil only, results from the application of lime for 30 years. The subsoil still contains no free carbonates. On Pedon B, decalcification during the formation of the profile, caused by a vegetation (Haans, 1954) was less pronounced. At about 50 cm the profile has much lime deposited as shells and small fragments. The surface soil, however, has been decalcified. It has not been limed as much as Pedon G as is shown by the difference in pH value (Appendix I). Pedon G has been green-manured and dunged for at least 25 years. During the last 10 years every field of the farm has been used for the growth of grass during three years, to be followed by use as arable land for the next three years. When wheat is grown, the soil is always green-manured. The field where Pedon G is found was notoriously bad about 1930. The surface soil had a weak unstable structure. Continued investment in lime and careful management has converted it into a productive soil.Pedon B, however, is on a field whose ownership has changed several times over the last thirty years. It was never green-manured until 1966. The surface soil therefore contains less organic matter and lime than that of Pedon G.The particle size distribution of the two pedons is identical. Average yields, as roughly estimated by the farmers from varying data of several years, were different for both farms. For sugar beet a yield of 50 tons, for wheat of 5.0 tons per ha was considered normal for farm G. For farm B this was 40 and 4.5 tons respectively. Such uncontrollable yield values, however, are not satisfying for describing soil quality and suitability. More important therefore was the opinion of the farmers that in general, soil B seemed more susceptible to structure deterioration and offered more problems than soil G. The suitability for agriculture of soil B was therefore considered inferior to that of soil G.The aim of this study is to investigate this general statement and to describe it in quantitative terms. Before discussing the results of the fieldwork and a series of model experiments, the term suitability, as used when comparing both soils, must be explained.The soil is used by the farmer to produce agricultural crops. His profit is determined by a difference between crop value and costs. A low yield may not necessarily be unfavourable, at least not when relatively high prices are being paid, as may be expected when generally low yields are found on other soils. On the contrary, in a year when average yields are high, prices tend to be lower. Then, in spite of higher yield, the amount of cash received for the crop may be lower as well, whereas costs of management will be simular. Prices, however,, not only vary as a function of the amount of supply but also because of differences in quality.Cost figures are governed by the system of management of the farmer. Certain costs are inevitable, like those for seeding or planting and those for fertilization. The procedure followed in practice and its efficiency will determine its magnitude. Others, seem less inevitable. Some tillage practices for example are subject to discussion in this regard.Each farmer will judge the quality of his land considering these factors. He will call a soil suitable when a regular and high production, both in volume and quality, is possible, especially in years when the general productivity level is low.Besides, each crop to be grown is one from a cycle of different crops grown in a specific pattern of rota-lion. His final opinion on suitability will therefore be based on a judgment, considering the degree of financial succes by which certain crops can be grown during the years as a part of a rotation, that seems most lucrative.A farmer will thus be able to give a description of the quality of each of his fields, based on experience of many years and on his own system of management that he considers to be the best.The question of suitability of certain soil types as shown on a soil map will be posed to the soil surveyer, whether he likes it or not. Access to the experience of farmers is then indispensable. A soil scientist however, will have to realize that his pattern of thinking may differ from that of the farmer. He primarly thinks in terms of well described and classified soil types, as expressed on soil maps, that have been formed in a certain parent material under influence of the soil forming factors. He digs a pit and considers one of its vertical walls. The picture obtained then is considered representative for the type of soil. A farmer thinks more in terms of management and economy. and above that in fields of landuse. A certain field will normally be covered by several soil units of the map. This is certainly true when relatively large fields are present, to enable efficient use of machinery. To get a suitability concept for a certain soil type, occurring on different farms, the soil scientist has to normalize as good as possible all factors not directly related to his object of study, the soil profile itself (Vink & van Zuilen, 1967). These factors are: the capability of the farmer, expressed by his management; landshape and accessibility of the land and the type and size of farm, as well as the usual system of crop rotation.Except for these factors it should be realized that each judgement is a clear function of the general economic situation, changing with time. Yields obtain on a certain type of soil usually vary considerably among years on the same field and also in the same year on different farms. Differences in weather during the growing season contribute to the first phenomenon, differences in soil management to the second.Modern agriculture shows many points of agreement with industry, emphasizing an increase in production for each worker. Therefore mechanization developed. In a relatively short period of time concepts of soil productivity and management have changed. Practical problems, often concerning soil structure and soil stability, are submitted ever more frequently to specialists. Their judgment, based on an analysis of farmers experience, can only be given in a rather static agricultural system. When this system changes, as is the case with the present general drive to mechanization, the answers of the past no longer satisfy. Therefore an independant analysis should be made of the soil profile and its soil material only, describing its range of variable properties as a function of soil management. This will be attempted in the next chapters for the two pedons of discussion.

M.S.

Studies of landslides in the Ottawa area have indicated that the clay involved in the failure was not an intact clay, but one containing a system of fissures. This paper deals with one of the cases studied, in which a 35-ft cut slope for a roadway failed five years after construction. Good agreement was achieved between the strength derived from the field study and the strength measured in the laboratory using the triaxial apparatus with low confining stresses.

Steep Rock Lake, in Western Ontario, was drained in 1943-44 by means of a large pumping operation. As the water line dropped, serious movements of the exposed soil occurred. Study of these, in connection with the development of the open pit from which the valuable iron ore was to be mined, led to an extensive soil investigation. The varved "clays" revealed by the mining operations with a total thickness of over 100 feet were studied first with engineering objectives in view. These "soil mechanics" investigations led to a detailed study of the soil in individual varves. Results confirm several features of the well-known seasonal theory of deposition but raise some questions which suggest the desirability of carrying still further this laboratory soil research.

A desorption technique was employed to evaluate chemisorption of ammonia by clays under moist conditions. In equilibria involving ammonia, all factors favoring volatilization losses of gaseous ammonia would undoubtedly exert an influence on the ultimate equilibria which are reached. Investigation of the relationship between pH and ammonia equilibria in soils revealed that an increase in the concentration of ammonium ions, applied as ammonium sulfate, stimulated ammonia losses from fine-textured soils at pH's ranging from 4.5 to 7.1. Ammonia volatilization was directly related to the initial pH of the soil and increased with an increase in pH. It was postulated that ammonia may be volatilized, even from acid soils, due to the equilibrium NH₄⁺ + OH⁻ ⇌ NH₃ + H₂O. By using initial concentrations of ammonium ions from ammonium sulfate applied, initial pH of an aqueous suspension of the soil and a value Kb = 1.80 x 10⁻⁵, values of ammonia losses were predicted. The linear relationship found between predicted and measured amounts of ammonia losses from acid as well as neutral soils, was interpreted as evidence of the existence of the proposed volatilization mechanism in soils. In attempting to evaluate the characteristics of ammonia retention by homo-ionic bentonites and kaolinites under moist conditions, it was found that base-saturated clays did not chemisorb ammonia in a fashion which could be described by Langmuir's adsorption isotherms. The S-shaped curves did not necessarily reflect polymolecular sorption. In strong contrast, chemisorption of ammonia by Al-saturated clays, followed Langmuir's equation almost perfectly. Evaluation of the inverse values of the differential slopes of two straight line segments obtained in the desorption isotherms corresponded closely to values obtained for the permanent charge (CEC) and the total charge (total CEC) developed at a specific pH higher than 6 respectively. It was shown that if sufficient ammonia is applied, exchangeable Al⁺⁺⁺ of Al-compounds may be precipitated as Al(OH)₃. An attempt to evaluate pseudo-equilibrium constants for aluminum-clay ammonia equilibria by using Langmuir's adsorption equation, was unsatisfactory. Chemical kinetic studies indicated that ammonia volatilization reactions could be described by a fast reaction and a slow reaction. The slow reaction represented chemisorption of ammonia on the permanent charge exchange sites. Extrapolation of the slow reaction to zero time yielded values corresponding closely to the CEC permanent charge. Investigation of the effects of CO₂, the NH₄⁺ concentration is increased, resulting in more effective replacement of basic cations for "permanent charge" exchange spots. The lower pH and higher effective NH₄⁺ concentration resulted in higher retention of NH₄⁺ in Na⁺- and K⁺-clays. The most striking retention of NH₄⁺ was obtained in Mg- and particularly in Ca-bentonites. It is believed that the Ca and Mg ions, exchanged by NH₄⁺ ions, are effectively removed from the soil solution as a result of the precipitation of these compounds which are sufficiently insoluble to ensure conservation of ammonia as chemisorbed ammonium ions. Ph. D.

As part of an over-all study of the performance of building foundations in highly plastic soil areas of western Canada, the Division of Building Research has been measuring ground movements and changes in soil moisture conditions in grass-covered, undisturbed soil profiles under climatic conditions ranging from sub-humid to semi-arid. Results of measurements begun in 1951 in Winnipeg, Manitoba, and more recently those in Regina, Eston, and Tisdale, Saskatchewan, are reported. Results of a theoretical soil moisture depletion calculation, based on Thornthwaite's potential evapo-transpiration concept, are presented. It is proposed as a more rational way of measuring the vegetation-climate factor in humid to sub-humid climates than simply comparing air temperature and precipitation with long-term averages. Empirical relationships are suggested between calculated soil moisture depletion, the depth of free water table, and the depth of frost penetration under similar thermal conditions but different soil moisture conditions. Shrinkage in situ of undisturbed, unsaturated soils at temperatures well below 32° F has been observed and is attributed to thermal air-void volume change.

A practical problem initiated this study. In the Haarlemmermeer, a former lake reclaimed about 1850, several farmers had difficulties with soil structure. Land, plowed in autumn, was very wet in spring. Free water was sometimes present on the soil surface. Planting and seeding were long delayed in spring and yields were unsatisfactory because of irregular crop development.Some farmers ascribed it to pressure from the back wheel of the tractor in the open furrow during plowing, compacting the subsoil and severely reducing permeability. Plowing practices were therefore changed. Equipment was used that could be moved by driving the tractor with all four wheels over the normal soil surface. This sometimes needed very old horse ploughs, adapted to tractors. Other farmers tried to improve drainage by laying more tile drains alongside existing systems, but usually the drains did not conduct water.The problems occurred on several soil types, but especially on the somewhat lighter textured sandy loams of the Hoofddorp Complex (Pgb) (Haans, 1954).The Agricultural extension service helped in the selection of two farms, where a pedon was selected. In one, henceforth called G, no problems occurred. In the other, called B, soil structure had deteriorated. Morphological and physical properties of each pedon were frequently investigated for about 18 months. Soil management was left to each farmer. Profile descriptions, particle size distributions and routine analytical data of each pedon are in Appendix I. Differences in these values between the two profiles are mainly a result of soil management.Originally the carbonate content of Pedon G was very low throughout. The content of 1%, as found now in the surface soil only, results from the application of lime for 30 years. The subsoil still contains no free carbonates. On Pedon B, decalcification during the formation of the profile, caused by a vegetation (Haans, 1954) was less pronounced. At about 50 cm the profile has much lime deposited as shells and small fragments. The surface soil, however, has been decalcified. It has not been limed as much as Pedon G as is shown by the difference in pH value (Appendix I). Pedon G has been green-manured and dunged for at least 25 years. During the last 10 years every field of the farm has been used for the growth of grass during three years, to be followed by use as arable land for the next three years. When wheat is grown, the soil is always green-manured. The field where Pedon G is found was notoriously bad about 1930. The surface soil had a weak unstable structure. Continued investment in lime and careful management has converted it into a productive soil.Pedon B, however, is on a field whose ownership has changed several times over the last thirty years. It was never green-manured until 1966. The surface soil therefore contains less organic matter and lime than that of Pedon G.The particle size distribution of the two pedons is identical. Average yields, as roughly estimated by the farmers from varying data of several years, were different for both farms. For sugar beet a yield of 50 tons, for wheat of 5.0 tons per ha was considered normal for farm G. For farm B this was 40 and 4.5 tons respectively. Such uncontrollable yield values, however, are not satisfying for describing soil quality and suitability. More important therefore was the opinion of the farmers that in general, soil B seemed more susceptible to structure deterioration and offered more problems than soil G. The suitability for agriculture of soil B was therefore considered inferior to that of soil G.The aim of this study is to investigate this general statement and to describe it in quantitative terms. Before discussing the results of the fieldwork and a series of model experiments, the term suitability, as used when comparing both soils, must be explained.The soil is used by the farmer to produce agricultural crops. His profit is determined by a difference between crop value and costs. A low yield may not necessarily be unfavourable, at least not when relatively high prices are being paid, as may be expected when generally low yields are found on other soils. On the contrary, in a year when average yields are high, prices tend to be lower. Then, in spite of higher yield, the amount of cash received for the crop may be lower as well, whereas costs of management will be simular. Prices, however,, not only vary as a function of the amount of supply but also because of differences in quality.Cost figures are governed by the system of management of the farmer. Certain costs are inevitable, like those for seeding or planting and those for fertilization. The procedure followed in practice and its efficiency will determine its magnitude. Others, seem less inevitable. Some tillage practices for example are subject to discussion in this regard.Each farmer will judge the quality of his land considering these factors. He will call a soil suitable when a regular and high production, both in volume and quality, is possible, especially in years when the general productivity level is low.Besides, each crop to be grown is one from a cycle of different crops grown in a specific pattern of rota-lion. His final opinion on suitability will therefore be based on a judgment, considering the degree of financial succes by which certain crops can be grown during the years as a part of a rotation, that seems most lucrative.A farmer will thus be able to give a description of the quality of each of his fields, based on experience of many years and on his own system of management that he considers to be the best.The question of suitability of certain soil types as shown on a soil map will be posed to the soil surveyer, whether he likes it or not. Access to the experience of farmers is then indispensable. A soil scientist however, will have to realize that his pattern of thinking may differ from that of the farmer. He primarly thinks in terms of well described and classified soil types, as expressed on soil maps, that have been formed in a certain parent material under influence of the soil forming factors. He digs a pit and considers one of its vertical walls. The picture obtained then is considered representative for the type of soil. A farmer thinks more in terms of management and economy. and above that in fields of landuse. A certain field will normally be covered by several soil units of the map. This is certainly true when relatively large fields are present, to enable efficient use of machinery. To get a suitability concept for a certain soil type, occurring on different farms, the soil scientist has to normalize as good as possible all factors not directly related to his object of study, the soil profile itself (Vink & van Zuilen, 1967). These factors are: the capability of the farmer, expressed by his management; landshape and accessibility of the land and the type and size of farm, as well as the usual system of crop rotation.Except for these factors it should be realized that each judgement is a clear function of the general economic situation, changing with time. Yields obtain on a certain type of soil usually vary considerably among years on the same field and also in the same year on different farms. Differences in weather during the growing season contribute to the first phenomenon, differences in soil management to the second.Modern agriculture shows many points of agreement with industry, emphasizing an increase in production for each worker. Therefore mechanization developed. In a relatively short period of time concepts of soil productivity and management have changed. Practical problems, often concerning soil structure and soil stability, are submitted ever more frequently to specialists. Their judgment, based on an analysis of farmers experience, can only be given in a rather static agricultural system. When this system changes, as is the case with the present general drive to mechanization, the answers of the past no longer satisfy. Therefore an independant analysis should be made of the soil profile and its soil material only, describing its range of variable properties as a function of soil management. This will be attempted in the next chapters for the two pedons of discussion.

To test whether flocculation is a prerequisite for granulation and a waterstable structure or whether drying (close contact) is sufficient, homoionic suspensions were prepared from pure sodium, potassium, calcium or magnesium montmorillonite, illite or kaolinite and from the respective soil clays. Forms other than Na were prepared from Na suspensions without drying; the ultimate salt concentration was below flocculation value.Suction-moisture curves were established and reswelling (pF 1 after positive pressure) was studied. Sodium clays except latosol swelled again completely after drying; potassium clays, except pure montmorillonite, swelled again completely up to high suctions; calcium and magnesium clays showed partial reswelling; latosol none, except with Na at high pH; pure illites swelled again but the soil clays behaved like soil montmorillonite. Inversion shaking was used to estimate the stability of granules formed by complete or partial water desorption. The stability of calcium and magnesium clays, and soil clays depended slightly on salt concentration; with Na or K, stability depended strongly on salt concentration, except in potassium illite soil clay; stability of all latosols decreased with salt concentration. The stability test was also employed to estimate the destruction caused by working the soil at different water contents. The phenomena observed could be explained by MADELUNG forces between parallel planes of clay minerals at short distance and by edge to plane attraction.

The construction of a 360-mile railroad to reach the iron- ore deposits in Quebec-Labrador in terrain virtually unknown could be expected to raise serious problems with respect to soil conditions. The climate of the region imposed another set of difficulties because the winters are severe and the short summer season is cool with frequent rainfall. This paper points out the difficulties that were caused by soil conditions and sets forth some of the measures taken to remedy the situation. Slope stability in banded clays was a serious problem in the first 30 miles. Because of the climate, frost action was a major consideration throughout the length of the line. Construction problems were mainly caused by loose, saturated soils with very poor natural drainage, and frequent rainfall in the summer months.

Movements in shallow foundations may occur due to volume changes in underlying clay that result from drying or wetting of the clay. With proper appreciation of the causes of these problems, foundations can be designed to eliminate damage resulting from differential movements.

In many countries there are problems resulting from building on clays that undergo differential movements due to seasonal shrinking or swelling. In South Africa, for instance, the problems are mainly caused by swelling whereas in England they are more often due to shrinking of the clay. Both problems exist in Canada. If the natural precipitation or evaporation at the ground surface is disturbed, as is the case when the ground surface is covered by a structure, the water content of the soil will be affected causing the clay to shrink or swell depending on its initial condition. Ground movements are also related to seasonal climatic conditions, such as precipitation, evapo-transpiration and temperatures which affect the water content of the soil. In Canada the problem of soil movement has been observed in British Columbia throughout the Prairies and in the Ottawa- St Lawrence lowland. Detailed studies are being carried out at Winnipeg and Ottawa where ground movements are being measured to depths of 8 ft. or more, using multi-rod gauges and concentric telescopic ground movement gauges. Readings have been collected at locations near trees, under flat slabs, in grass plots and on water-mains. Results from these measurements and the correlation of the variables are presented.

In addition to its structural role, the foundation usually separates the man-made indoor climate from the actual environment of the ground. The implications of this secondary role are sometimes not fully appreciated by the designer, with serious consequences. The structural success of shallow foundations on volume-changing clays may be governed by their net effects on the subsoil environment. The significance of changes from natural ground conditions by construction must be appreciated at least qualitatively by the foundation designer. Natural and artificial changes in the thermal, the moisture, and the stress environments of subsoils are discussed in this paper, with particular emphasis on the clay soils and the climatic conditions of Western Canada.

It is the purpose of this Digest to direct attention to the slope stability problem as it relates to clays and to present information on the factors that affect the stability of slopes. Recommendations are given as to the precautions that should be taken to prevent tragedies. Although the clays of the St. Lawrence valley are emphasized, the method of analysis and the corrective measures described can be applied to clays in general.

Stiboka research

Quantitative analysis of soil elay minerals after X-ray, differential thermal, infrared, cation exchange and chemica! analysis is treated. Partiele size, crystallite size, the grade of structural ordening in the minerals, and the surface being covered by an amorphous (Beilby) layer, have large influence on the results. Examples are given.

To test whether flocculation is a prerequisite for granulation and a waterstable structure or whether drying (close contact) is sufficient, homoionic suspensions were prepared from pure sodium, potassium, calcium or magnesium montmorillonite, illite or kaolinite and from the respective soil clays. Forms other than Na were prepared from Na suspensions without drying; the ultimate salt concentration was below flocculation value.Suction-moisture curves were established and reswelling (pF 1 after positive pressure) was studied. Sodium clays except latosol swelled again completely after drying; potassium clays, except pure montmorillonite, swelled again completely up to high suctions; calcium and magnesium clays showed partial reswelling; latosol none, except with Na at high pH; pure illites swelled again but the soil clays behaved like soil montmorillonite. Inversion shaking was used to estimate the stability of granules formed by complete or partial water desorption. The stability of calcium and magnesium clays, and soil clays depended slightly on salt concentration; with Na or K, stability depended strongly on salt concentration, except in potassium illite soil clay; stability of all latosols decreased with salt concentration. The stability test was also employed to estimate the destruction caused by working the soil at different water contents. The phenomena observed could be explained by MADELUNG forces between parallel planes of clay minerals at short distance and by edge to plane attraction.

Natural degradation of slopes is normally considered to involve surficial displacements resulting mainly from frost action, erosion, and downhill creep. Measurements from inclinometer installations in a variety of slope profiles in the Ottawa area show that significant deep-seated movements may occur in these slopes. These movements are associated with seasonal peaks in ground water pressures within the slope and may contribute to the long term degradation of the slope. While the factor of safety against catastrophic failure of a slope is of prime importance, the possible effects of deep-seated slope movements should not be disregarded when considering adjacent land use.

This paper describes the design and use of deep bench marks by the Division of Building Research of the National Research Council of Canada. The bench marks consist of an inner pipe protected by an outer casing from the effects of seasonal ground movements and frost action. In sensitive clays the bench mark is installed by jacking or driving the outer casing with relatively simple equipment. In stiffer clays it is inserted in an augered hole and then turned and pushed to refusal with a drill rig. In permafrost areas, the bench mark is placed in a drilled or steamed hole to a depth at which the lower portion of the inner rod is securely anchored in the perennially frozen ground. Details of bench mark assemblies and installation techniques for soft clays, stiff clays, and frozen ground are described.