Clayey Slopes Research Articles

A hydrochemical study of urban landslides caused by heavy rain: Scarborough Bluffs, Ontario, Canada

Scarborough Bluffs is a 15 km long stretch of the Lake Ontario shoreline east of downtown Toronto. This heavily urbanized area currently represents Canada's most serious erosion problem. The worst affected zone is 1.5 km long and lies along South Marine Drive where 50 m high bluffs are failing by shallow retrogressive failures of jointed glacial clays over underlying deltaic sands and clays. The erosion rate is about four times that for the coastline as a whole.Heavy rains in the Toronto area in August and September 1986 produced a spate of slope failures and mud flows. Particularly heavy storms on September 10 and 29 triggered extensive retrogressive slope failures at South Marine Drive. Hydrochemical investigations of discharge waters suggest that slope failure was caused by surface runoff on the bluff top recharging lower slope areas by infiltration through joints in the upper clay capping. Discharge of water from the lower slope is impeded by less permeable barriers in the deltaic stratigraphy at the site and by a cover of clayey slope debris. Data suggest that provision for adequate drainage of the bluff top, by interceptor drains, is a prerequisite for controlling slope behaviour in the area. Key words: slopes, erosion, groundwater, hydrochemical, recharge, drainage.

Correction of clayey slopes by means of underground drainage curtains (in Spanish) : Eraso, A In: Proc World Congress on Water in Mining and Underground Works (SIAMOS-78), Granada, Spain, 18–22 Sept 1978, V2, P1323–1329. Publ Granada: Asociacion Nacional de Ingenieros de Minas, 1978

Correction of clayey slopes by means of underground drainage curtains (in Spanish) : Eraso, A In: Proc World Congress on Water in Mining and Underground Works (SIAMOS-78), Granada, Spain, 18–22 Sept 1978, V2, P1323–1329. Publ Granada: Asociacion Nacional de Ingenieros de Minas, 1978

Effect of wellpoints on stability of soft clay slopes in the process of excavation

In the past, it was generally considered that the wellpoint method was suitable only for sands and not for cohesive soils. This article introduces two case histories of dock foundation pits in which the excavation work of a clayey soil slope was stabilized by the wellpoint method. The effects of the wellpoint method in clayey soil may be summarized as follows: the total stress on the whole has not been changed, the pore water pressure has been dissipated constantly, and then yields a consolidation process in which the effective stress will increase correspondingly. In this work, the method of measuring shear strength during excavation and wellpoint pumping and the stability analysis method are also introduced. A large amount of observational data of pore water pressure, settlements and internal horizontal displacements and the vane shear strength indicated that the effect of wellpoint method is prominent, if the coefficient of permeability of a clayey soil is not less than 1 × 10−6 cm/sec.

Macro-Invertebrate Assemblages as Indicators of Sedimentary Environments in East Mississippi Delta Region

As a result of a study based on three years of biological sampling in the east Mississippi Delta region, eight macro-invertebrate assemblages are recognized, each characteristic of a specific sedimentary environment ranging from the Mississippi Delta marshes to the edge of the continental shelf northeast of the Delta proper. The eight assemblages and their corresponding environments are: (I) the delta marshes, (II) delta front and lower distributaries, (III) lower Breton Sound and lower pro-delta clayey slopes, (IV) upper Breton Sound, (V) inlets, or areas of strong currents, (VI) the shallow continental shelf of the Gulf of Mexico from 0 to 12 fathoms, (VII) the deeper part of the continental shelf from approximately 13 fathoms to 60 fathoms, and (VIII) the living oyster reefs of the shallow protected bays of the Delta region. The boundaries of these environments were established by plotting the distributions of both living and dead representatives of species of invertebrates furnishing hard parts plus the distributions of living soft-bodied animals which were so abundant as to characterize regions where animals with hard parts were scarce though present. Comparison of the distribution of the hydrographic factors with the physiography of the land-masses in this area with the macro-organism distributions made it possible to formulate criteria for the interpretation of ancient environments as far back as the Miocene on the Gulf and Atlantic coasts. Paleontologic literature shows that most of the present-day delta species have been found in the Pliocene, and most of the diagnostic forms have existed since the lower Miocene. The primary factors influencing distributions of these organisms are bottom type, salinity and temperature (especially the degree of variability), turbidity of the water, and currents. It was also found that comparative rates of deposition could be estimated by the ratio of the number of living to the number of dead, i equal-size samples. A series of marine bottom communities based on the community concept of European marine ecologists is recognized on the basis of the most abundant and widespread animals.