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Slope movements of the deep-seated Campo Vallemaggia landslide in the southern Swiss Alps have been reported for over 200 years. Surface and borehole investigations of the unstable mass reveal an up to 300 m deep complex structure incorporating 800 million cubic metres of disturbed metamorphic rocks divided into blocks along primary fault zones. An average slide velocity of approximately 5 cm/year can be calculated from various monitoring data recorded between 1892 and 1995. Block movements primarily involve mechanisms relating to multiple shear surfaces, but in cases where slide blocks are constrained by other blocks, creep deformations are observed. Borehole investigations revealed the presence of artesian water pressures, which when integrated with inclinometer and surface geodetic data, helped to provide key insights into the underlying instability mechanisms. This paper reports the findings of an extensive mapping, geophysical, and monitoring investigation carried out over a 20 year period. Results from the analysis are presented with respect to the hydromechanical factors controlling the unstable mass, the significance of which were instrumental in resolving conflicts with regards to the slope mitigation measures required to stabilize the slope. In Part II (see companion paper, this issue), the stabilization works performed at Campo Vallemaggia and their effectiveness are presented.

This paper presents a series of flume-scale experiments to investigate suffusion at the bottom of a cutoff wall in an internally unstable sandy gravel alluvium. The initiation, progression, and potential failure of suffusion and the interactive effects of geomechanical and hydraulic conditions with the evolution of suffusion were investigated in this particular application. Temporal and spatial development of pore pressure, earth pressure, and settlement demonstrated suffusion was a multi-phase (involving pore water, fine and coarse fractions) and multi-field (involving seepage, seepage-induced fine-fraction variation, and stress–deformation) coupling phenomenon. Suffusion initiated at the downstream side of the tip of the cutoff wall and then generally progressed backward to the upstream side. The monitored earth pressure provided an evidence of the heterogeneous stress distribution in internally unstable soil. Two linear empirical formulas for average hydraulic gradients at the initiation of suffusion and at blowout were derived based on the flume-scale model experiments.

The paper presents hydrogeologic properties for a leaky till–mantled fractured bedrock aquifer system based on geophysical and hydraulic tests performed at a drumlin located in northeastern Massachusetts, USA. The site profile consists of a fractured bedrock aquifer overlain by a 30 m thick unweathered, coarse-grained till aquitard. Steady state, decadal scale, hydraulics varied little until seasonal irrigation pumping was initiated in recent years, causing a substantial annual drawdown in the aquifer and leakage from the overlying till. High frequency hydraulic head data sets collected in monitoring wells record the hydraulic response to the irrigation pumping. These data sets, together with results from small scale slug and purge tests performed in monitoring wells, are used to characterize the hydrogeologic behavior of this groundwater system. Geophysical logging performed in bedrock wells confirmed the presence of numerous flowing fractures. The large-scale continuum analysis of the fractured bedrock aquifer response to the irrigation pumping yields transmissivity values consistent with those determined from the small-scale, short-term purge test results. The low hydraulic conductivity till has a significant impact on the drawdown behavior of the fractured bedrock aquifer. Calibrated values from the collective data sets and analyses result in the following properties for the 30 m thick unweathered till: hydraulic conductivity K′ = 7.2 × 10−9m/s, transmissivity T′ = 2.3 × 10−8m2/s, and storativity S′ = 2.7 × 10−4, and for the underlying fractured bedrock aquifer: T = 6.5 × 10−6m2/s with an average fracture aperture of 46 μm and hydraulic conductivity Kf= 1.3 × 10−3m/s. These results should describe similar unweathered coarse-grained till–mantled fractured bedrock aquifer systems and provide useful data for preliminary analyses prior to any site-specific investigations.

The Champlain Sea Basin in eastern Canada is known for its sensitive clay and associated engineering problems through this much-developed area along the St Lawrence River. Geologically, the surface of the Champlain clay has been subjected to desiccation, frost action, and weathering. This has resulted in the reduction of the water content and sensitivity of the surficial crust layer of this very wet clay deposit sufficiently to enable it to be used as an earthworks material. However, the material is still much wetter than its optimum moisture content. By co-operative value engineering, the team on the Nouvelle Autoroute 30 project in Montréal, Quebec, investigated and achieved moisture content and degree of compaction derogations to the Ministry of Transport, Quebec specification. This allowed the successful construction of many low and high road embankments using an unprecedented 2.3 × 106 m3 of this weathered Champlain clay crust material. This paper describes how the design and construction issues associated with using this material for earthworks were evaluated and addressed.

Every environmental site investigation aims at delineating near-surface (hydro-) stratigraphic units and their characterization. To determine the type and hydraulic properties of sedimentary deposits, direct push (DP) sensor probes and tools are promising methods and are therefore frequently applied to measure high-resolution vertical profiles of soil properties. Given the variety of these tools, the objective of this paper is to compare selected DP tools for the (hydro-) stratigraphic subsurface characterization in a heterogeneous unconsolidated sedimentary aquifer. An overview of current DP applications is given and selected DP tools were tested for reproducibility, as well as their ability to reflect soil variability and to estimate hydraulic conductivity, K. Although resolution differences exist, all of the applied methods captured the main aquifer structure. Correlations of the DP-based K estimates or proxies with DP slug tests (DPST) show that it is possible to describe the aquifer hydraulic structure on less than a metre scale by combining DPST data and continuous DP measurements. Although correlations are site-specific and appropriate DP tools must be chosen, DP is a reliable and efficient alternative for characterizing even strongly heterogeneous sites with complex sedimentary architectures.

Earthquake observations at different sites within alluvial soil deposits have demonstrated that the motion of buried underground structures closely follows that of the surrounding soil. Therefore, it is usual in a seismic design process to apply free-field ground displacements through Winkler-type soil springs to an underground structure to evaluate stress patterns induced within its structural members. Using a simplified approach, this paper provides a clear understanding of resonant horizontal ground displacement of and strain in a surface soil deposit with a radical change of depth and of where they occur.Key words: simple approach, seismic design, earthquake, resonance, underground structures.

This paper presents an analysis of hydraulic head data measured every 2 h for 2 years in the leading edge of a drumlin that consists of weathered, brown clayey sand till and underlying unweathered gray clayey sand till. The brown till responds as an unconfined aquifer and acts as a boundary condition for the confined gray till aquifer. Analytical models are presented for interpretation of the hydraulic head data using annual, monthly, and daily timescales, for estimation of drumlin (landform) hydraulics and till (formation) properties. The annual average head data from open-standpipe piezometers calibrate drumlin hydraulics that feature steady radial flow in the brown till, because of its higher permeability (1.1 × 10–13 m2) and the finite radius of the drumlin. The lower permeability (1.4 × 10–15 m2) gray till has steady cylindrical flow with an appreciable downward gradient. Open-standpipe piezometer data are modeled at the monthly timescale to confirm the landform hydraulics and calibrate a brown till macroporosity of 0.016. The amplitude of periodic monthly head fluctuations increases towards the edge of the drumlin. Hydraulic head response to aperiodic storm events is significantly magnified by this macroporosity as measured by precipitation gages and buried pressure transducers. The storm data are modeled on a daily timescale to confirm the brown till macroporosity value estimated from the monthly data and to further elucidate gray till hydraulics. Compressibility delays and attenuates the groundwater mound, with a calibrated gray till compressibility of 3 × 10–9 Pa–1. The calibrated models accurately recover drumlin flow fields with plausible property values of the clayey sand till, and accordingly should describe other sites with similar landforms and deposits.Key words: drumlins, till, hydraulics, compressibility, permeability, macroporosity, piezometer.

The paper proposes a new elastic-plastic framework for unsaturated, high-plasticity, clayey soils and sand- clay mixtures. The framework considers possible coupling of stress- and suction-induced hardening, leading to a yield surface that is closed or "capped" as suctions increase. This produces a stress state boundary surface in three- dimensional p-q-s stress space (where p is the net mean stress, q is the deviator stress, and s is the matric suction) which differs from that of other conceptual models of its kind. Yielding, a hardening law, and failure criteria for satu - rated soils are incorporated into the stress state boundary surface. Two parameters, equivalent pressure pe and stress ra- tio η s, are introduced to form the basis of the proposed elastic-plastic framework for highly plastic soils with high suctions. This provides an alternative for the stress variables net mean stress and matric suction that are commonly used in modeling unsaturated soils with lower plasticity and lower suctions. This framework has allowed results of ex- periments on an unsaturated sand-bentonite mixture to be successfully described using elastoplasticity. Yield and fail - ure envelopes associated with the proposed state boundary surface in p-q-s space can be normalized using pe and η s in such a way that they agree with a comparable envelope for saturated specimens. Resume : L'article propose un nouveau cadre de travail elasto-plastique pour des sols argileux non satures fortement plastiques et des melanges sable-argile. Le cadre de travail considere le couplage possible du durcissement induit par la contrainte et de celui induit par la succion, ce qui conduit a une surface de limite elastique fermee, ou « enveloppe », lorsque la succion augmente. Ceci produit une surface d'etat de contraintes frontiere dans l'espace de contraintes tridi- mensionnelles p-q-s qui differe de celle des autres modeles conceptuels de la sorte. On a incorpore dans la surface frontiere de l'etat de contraintes, la limite elastique, une loi de durcissement, et un critere de rupture pour les sols satu- res. On a introduit deux parametres, la pression equivalente pe et le rapport de contraintes s, afin de constituer la base du cadre de travail elasto-plastique pour les sols fortement plastiques avec des succions elevees. Ceci fournit une alter- native pour les variables de contrainte, la contrainte mediane nette et la matrice de succion, qui sont communement uti- lisees dans la modelisation des sols non satures avec une plasticite et des succions plus faibles. Ce cadre de travail a permis de decrire avec succes, au moyen de l'elasto-plasticite, les resultats des experiences sur un melange sable-ben - tonite non sature. Les enveloppes de limite elastique et de rupture associees a la surface d'etat frontiere proposee dans l'espace p-q-s peuvent etre normalisees par rapport a pe et s de facon telle qu'elles concordent avec une enveloppe comparable pour les specimens satures. Mots cles : non sature, elasto-plastique, triaxial, matrice de succion, surface frontiere d'etat, sable-bentonite. (Traduit par la Redaction) Tang and Graham 907

An experimental apparatus was developed at The University of British Columbia, Vancouver, Canada, to investigate model pile dynamic response and soilnpile interaction. The model test apparatus comprised a container of soil in which piles were inserted. The container was then mounted on a shake table and subjected to simulated earthquake shaking. High stresses were obtained in the soil model by subjecting it to very high downward hydraulic gradients, a technique called hydraulic gradient similitude (HGS). In this way, stresses simulating field conditions were obtained. This is very important in soil because the behaviour of soil is highly dependent on stress levels. This paper presents the study carried out on the effect of the soil container boundary conditions on the response of the soil within the box. The effectiveness and limitation of placing soft material on the vertical boundaries of the model, averting wave reflections, are examined and discussed. This was examined directly in the model by placing soft material adjacent to the boundaries. It was also examined analytically using the FLUSH computer code. Both experimental and analytical results indicate that response of the soil within the HGS device without soft material on the side walls (rigid boundaries) is closer to that in the free field conditions, and the HGS apparatus reasonably provides a high stress level that matches the field conditions. Resume : Un apppareil expOrimental a OtO dOveloppO ‡ liUniversitO de Colombie Britannique, Vancouver, Canada, pour Otudier la rOponse dynamique de pieux modles et liinteraction solnpieu. Liappareil diessai sur modle comprend un contenant de sol dans lequel les pieux sont insOrOs. Le contenant est alors montO sur une table oscillante et soumise ‡ des oscillations sismiques simulOes. Des contraintes OlevOes ont OtO obtenues dans le modle de sol en le soumettant ‡ de trs forts gradients hydrauliques vers le bas, ce qui est appelO la technique de similitude de gradient hydraulique (HGS). De cette faAon, des contraintes simulant les conditions de terrain sont obtenues. Ceci est trs important dans le sol parce que le comportement du sol est fortement dOpendant des niveaux de contraintes. Cet article prOsente liOtude de lieffet des conditions aux frontires du contenant sur la rOponse du sol ‡ liintOrieur de la boOte. Lion examine et discute liefficacitO et la limitation de la mise en place diun matOriau mou sur les frontires verticales du modle, Ovitant ainsi les rOflexions des ondes. Ceci a OtO examinO directement dans le modle en plaAant un matOriau mou adjacent aux frontires, et de faAon analytique au moyen du code diordinateur FLUSH. Tant les rOsultats expOrimentaux quianalytiques ont indiquO que la rOponse du sol ‡ liintOrieur de liappareil HGS sans matOriau mou sur les cUtOs des murs (frontires rigides) se rapprochent plus de celle observOe dans les conditions de terrain, et que liappareil HGS fournit de faAon raisonnable un niveau OlevO de contrainte qui Ogale les conditions de terrain. Mots clOs : gradient hydraulique, modOlisation, rOponse dynamique, frontire. (Traduit par la rOdaction)

Design of deflectors or barriers to slow or stop snow avalanche debris in the runout zone requires estimates of runup height. In this paper, experimental data on runup of dense, dry granular flows in a flume are presented. The data are then compared with two one-dimensional theoretical equations for runup estimation: (1) a formulation based on following the leading edge of the flow up the barrier and (2) the traditional method adapted from equations presented by A. Voellmy for describing the centre of mass of the avalanche. The results show that the leading-edge model more closely matches the experimental results and, in field applications, the leading-edge model is expected to provide higher and, therefore, more conservative runup estimates. Key words : avalanche run-up, granular flows, avalanche defences, runout zone.

This paper describes the regional geology, dimensions, morphology, sedimentology, and age relations of the Holocene "Carlson landslide," a large moist landslide composed of basalt breccia located on the eastern margin of the Lost River Range, Idaho. These data are combined to deduce the factors that prompted the slope failure, the kinematics of initiation, travel, and stopping of the landslide, as well as its postemplacement degradation. The landslide is compared with other terrestrial mass movements on the basis of morphology, sedimentology, log(volume) versus fall height –runout length (H/L) relations and estimated Bingham plastic yield strength. Morphology and sedimentology distinguish dry landslides from moist and water-saturated deposits. However, moist and water-saturated landslides plot well within the log(volume) versus H/L envelope for dry terrestrial landslides and exhibit overlapping ranges of estimated Bingham plastic yield strength values with dry landslides, indicating that moist and water-saturated landslides must travel much like dry rock avalanches of similar volume. Thus the mechanism(s) responsible for causing anomalous runout in large dry landslides could operate in moist and water-saturated landslides as well. Morphological comparison of the Carlson landslide with lobate martian landslides suggests a role for water in the martian landslides. Key words: landslides, debris flows, long runout, morphology, water, Mars.

Three types of evidence of deep seated creep of steep natural slopes are considered: surface manifestations such as fissures and depressions; inclinometer measurements on three slopes in the Ottawa area; and movements of a bridge superstructure spanning a steep sided ravine. Results of measurements show that the movements are not continuous but occur in response to seasonal high levels of the groundwater table. The implications of the movements are discussed in relation to the stability of clay slopes., Paper Prepared for Presentation at the 29th Canadian Geotechnical Conference, Vancouver, B.C., October 1976

The EOL (Eastmain – Opinaca – La Grande) diversion scheme of the La Grande Complex (phase I) for the James Bay Hydroelectric development in northern Québec diverts the waters of the Eastmain, Opinaca, and Petite Opinaca Rivers into the LG 2 reservoir. The EOL diversion consists of four dams and seven dykes about half of which are founded for part of their length on overburden foundations of variable thickness and consisting of heterogeneous deposits of glacial till or sandy and silty alluvia. The till core of these zoned embankments is either placed directly on the till strata or extended through the alluvia to the underlying till by a core trench. The construction of these embankments was completed in 1979 and the maximum reservoir level achieved in November 1980.This paper deals with the seepage and pore pressure behaviour in the overburden foundations, namely, dams OA-10B and OA-11 and the dyke OA-8B, during and subsequent to the reservoir filling. The results of the parametric seepage analyses carried out by finite element methods are compared with the observations. Special attempts are made to resolve the long-existing speculations regarding the anisotropy of natural deposits. Comments are made regarding the effective anisotropy of such deposits in the James Bay region and its effect on exit gradients and uplift forces, which influence the design and safety of dams and dykes. Keywords: seepage, pore pressure, hydraulic conductivity, anisotropy, foundation treatment, cutoff.

'Paper by Mackay, J . R. Can. Geotech. J . 11(2), p p 230-237. In these soils horizontal ice lenses are rarely observed by themselves except as sub-horizontal lenses in the active layer. The discussers would like to expand upon one theory noted by the author, by suggesting two mechanisms for reticulate ice vein growth that cause cracking in the unfrozen soil ahead of the advancing freezing front. Water is drawn into, or forced into, these cracks where, in time, it is frozen by the 0 O C isotherm. It is to be noted that while the writers agree with Maskay

This paper presents a case history of a multiblock landslide where the blocks move at varying rates along a common horizontal slip surface which follows the contact between stratified drift and underlying till. Movement measurements indicate that the blocks towards the toe move at a higher rate than blocks towards the scarp. Stability analyses show that the entire slide mass can be analyzed as a single unit as opposed to considering each block separately. This finding is compared with the analysis of other multiblock slides. The friction angle mobilized along the horizontal slip surface falls within the range of residual values measured in the laboratory. Key words: landslides, stability, analysis, translational slides, residual strength.

This paper reports on observations of frost penetration into glacial till in a region of high freezing indices. The frost penetration measurements were carried out in borrow areas and in exposed dyke crests. The locations are far enough apart to be representative of regional frost penetrations. The frost susceptibility of the till is evaluated, and the effect of frost penetration on the design of freeboard and crest detail requirements for the dams and dykes is discussed. The geotechnical properties of the till are given along with the results of a series of surcharged cyclic freeze–thaw and thermal conductivity tests.The use of standard frost susceptibility criteria indicates that the till is classified as being highly frost susceptible; however, if surcharge pressure is considered and recognized as being a factor in reducing frost heave, then the till under field conditions may behave like a material of low frost susceptibility.