摘要:

In the design of two 7 m high road cuttings in an overconsolidated sensitive clay in the Lachute region in Quebec, a slope inclination of 2.5:1 was retained for long-term stability. The minimum anticipated factor of safety against long-term failure was equal to 1.28 and was based on the postpeak strength parametersc′ = 7 kPa and, which are typical of the Champlain Sea clays. Following a series of failures in the southern slope of one of the cuttings, only 1.5 years after their construction, a postslide analysis was performed using the critical stress curve method. The results of the analysis yielded the shear strength parametersand. It is believed that the surprisingly small cohesion intercept at the time of failure found in this study is due to the fissured nature of the clay, the spreading of the discontinuities caused by stress relief following excavation, and subsequent desiccation of the exposed clay mass.

ISSN:0008-3674    

DOI:10.1139/t80-041

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A previously developed model is used to provide a probabilistic seismic stability analysis for a natural slope located near Slingerlands, New York. The safety of the slope is measured in terms of its probability of failure rather than the customary factor of safety.Three types of possible earthquake sources are investigated, namely, a point, a line, and an area source. The dependence on significant seismic parameters of the probability of failure of the slope is examined and the results are presented in a number of graphs and tables.On the basis of the results obtained in this study, it is concluded that (a) the present model is useful in assessing the reliability of soil slopes under both static and seismic conditions; and (b) the probability of failure of a soil slope is greatly affected by the type of earthquake source involved and the values of the seismic parameters that are associated with it.

ISSN:0008-3674    

DOI:10.1139/t80-042

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Very few data are available on the sediment yield of Alberta watersheds especially in the northern portion of the province. In the 175 000 km2Peace River basin, which covers about 25% of Alberta, sediment data are collected regularly at only four stations. One of these is the 112.7 km2Spring Creek watershed. In 1977 a pipeline was installed near the mouth of Spring Creek, disturbing an area of about 5000 m2near the stream channel. The effects of this were to increase local sediment yields by over 1600 Mg in a 4 month period. This compares with regional averages for the Peace River basin of 18–88 Mg∙km−2∙year−1. The study indicates the magnitude of spatial variation of sediment production and shows some effects of geotechnical activities on sediment yie

ISSN:0008-3674    

DOI:10.1139/t80-043

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The Cambridge self-boring pressuremeter and the Norwegian Geotechnical Institute field vane apparatus have been used at three sites of different subsoils. Two of the sites, South Gloucester and National Research Council of Canada grounds, are located in Leda clay in the Ottawa area. The third site features a highly plastic lacustrine clay in northwestern Quebec. At this site tests were conducted beside and under a fill that had undergone 1 m of surface settlement. At all three sites, the pressuremeter yields higher strengths than the field vane apparatus.Conventional and special laboratory tests were conducted on large diameter tube or block samples from South Gloucester. It is found that the conventional triaxial compressive strength is intermediate between the pressuremeter and field vane strengths. In accounting for the strength discrepancy, factors such as anisotropy, stress path, and disturbance have been studied in the light of the results of the special tests.

ISSN:0008-3674    

DOI:10.1139/t80-044

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

An analysis is presented to estimate the forces mobilized in reinforced earth retaining walls when subjected to a surcharge strip load. An estimate of the maximum traction force in a rein forcing element is deduced by a modification of Terzaghi’s formula for the computation of the lateral pressure against a conventional rigid retaining wall. Furthermore, a simple distribution is proposed for the traction force in a reinforcing element, and in consequence, the force transmitted to the facing of the wall. Tests on a wall model substantiate and verify the theoretical results. A worked example on the analysis of a reinforced earth retaining wall subjected to a surcharge strip load is given.

ISSN:0008-3674    

DOI:10.1139/t80-045

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The concept of pore pressure parameters has been found convenient to visualize the pore pressure response of saturated soils for various applied stress changes. This paper derives pore pressure parameters that can be utilized in determining the pore pressure response of unsaturated soils. The expressions derived for the estimation of pore-air and pore-water pressures under undrained, isotropic loading are called theBaandBwpore pressure parameters. Measured pore pressures are compared with predicted values. Various factors influencing the proposed pore pressure parameters are discussed.Pore pressure parameter expressions are also derived for the pore-air and pore-water pressures induced as a result of deviator stress changes during undrained loading (i.e.,AaandAw).

ISSN:0008-3674    

DOI:10.1139/t80-046

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A comprehensive review of long-term creep tests on ice has been undertaken and a flow law for ice has been proposed. Creep tests on ice-rich soils have also been reviewed, and it is concluded that the flow law for ice constitutes an upper bound to these test data. Using this flow law, pile velocities in ice and ice-rich soils have been predicted and the predictions are shown to be in good agreement with available long-term creep data for piles in ice and ice-rich soils.

ISSN:0008-3674    

DOI:10.1139/t80-047

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The results of various index tests and standard and scanning electron microscope examinations ofSphagnumand sedge peats form the basis for an investigation of peat fabric and structure.The volumetric and gravimetric relationships of a moderately humifiedSphagnumpeat are examined in detail, and phase diagrams are constructed for twoSphagnumpeats with different degrees of humification. Tentative phase diagrams for a sedge peat are also presented.A brief examination is made of existing classification systems and of some aspects of the formation of peats.

ISSN:0008-3674    

DOI:10.1139/t80-048

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A pneumatic seal has been developed to convert 50.8 mm standpipes to closed-system piezometers utilizing commercially available pneumatic transducer piezometers. This sealing system permits retrieval of the piezometers for recalibration or reuse elsewhere. A nonreinforced inflated rubber membrane seal was found to be satisfactory in soils of medium to high permeability and moderate piezometer pressures. A mesh-reinforced rubber membrane seal was found to be much superior and reduced the reaction of the seal to changed hydraulic pressures to unmeasurably small movements. This gave the piezometer better compliance characteristics making the system suitable for measuring relatively small pressure changes in soils of low permeability. Design and construction details of the nonreinforced membrane seal and mesh-reinforced membrane seal are presented. Field response times and operating pressures are discussed.

ISSN:0008-3674    

DOI:10.1139/t80-049

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The presence and the importance of amorphous material are becoming recognized in sensitive soils and have been documented in previous studies. In order to further appreciate the specific contributions and influences of the varying composition of amorphous material to a sensitive soil, it is necessary to obtain a soil system where the individual components can be rigorously controlled and subjected to proper scrutiny. To achieve this, the laboratory-prepared soils were obtained by mixing synthesized amorphous iron–silica mixed hydroxides of varying composition with silt-sized particles of primary materials such as quartz, feldspar, or hornblende.In this study the influence of water content and the amount and composition of amorphous material mixed with nonclay minerals on the resultant sensitivity and basic engineering parameters is investigated.The results indicate that Atterberg limits of the laboratory-prepared sensitive soils are dependent upon the composition of amorphous material and that the trends established are similar to those obtained in similar tests on natural sensitive clays obtained from St. Alban, Outardes, and Gatineau. Similarly, the increase in shear strength and soil suction upon aging of the prepared sensitive soil is dependent upon the composition or molar ratio Fe2O3/(Fe2O3 + SiO2) of amorphous material.

ISSN:0008-3674    

DOI:10.1139/t80-050

出版商:NRC Research Press    

年代:1980

数据来源: NRC