摘要:

A high-pressure, thick-walled hollow cylinder test device has been perfected to explore the consequences of stress paths which are typical of pressuremeter configurations, tunnelling, or shafting in soil materials. Several features have been incorporated to facilitate data gathering, and the device is readily adaptable toK0or standard compression and extension triaxial tests. It has been used on tests in artificially prepared dense sand specimens constructed by a freezing technique, and will be used in an extensive study of the behavior of oil sands. Typical results of tests on dense Ottawa sand (C-109) are presented.

ISSN:0008-3674    

DOI:10.1139/t81-001

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The adfreeze bond strengths of wood, concrete, and steel H-section piles embedded in fresh-water ice have been measured under constant rates of displacement for displacement rates varying between 10−4and 10−1 mm/min (loading rates between 10−3and 10 kN/min). Wood piles showed the highest adfreeze strength (0.6 and 1.8 MPa); that for concrete piles was independent of rate of displacement (average value 0.8 MPa); that for steel H-sections varied between 0.2 and 0.6 MPa. These results were used in estimating the contribution of ice adhesion to the total adfreeze strength of various piles in frozen sand.

ISSN:0008-3674    

DOI:10.1139/t81-002

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A simple numerical integration method has been developed for predicting growth of ice under snow cover where solar radiation does not play a dominant role. The method is capable of incorporating variations in snow conditions and physical properties of ice and snow during the growth period. Theoretical predictions compare favourably with field observations in Eclipse Sound, Baffin Island, for the winter seasons of 1977–78 and 1978–79.

ISSN:0008-3674    

DOI:10.1139/t81-003

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Excavation of underground openings in rock relieves theinsitustate of stresses, providing an initiating mechanism for time-dependent deformation in shaly rocks to occur. The construction of a permanent lining restrains the rock movement, resulting in an increase with time of pressure acting on the lining.Closed form solutions for this problem of rock structure – time interaction of circular tunnels have been developed, taking into account (a) the state of initial stresses, (b) the time-dependent properties of the lining as well as the rock, and (c) the time lapsed between excavation and lining. Expressions for lining pressures, stresses, thrusts, and moments are given for both "no slip" and "full slip" interface conditions.The effects of material parameters, lining flexibilities, and time lapse on quantities of engineering interest are studied and their implications on design illustrated.The results of analysis are compared with the field observations made in three tunnels. It is shown that the theoretical results are consistent with the observed extent and location of cracking in these tunnels.It is suggested that the methods proposed may be used for design considerations of permanent linings of tunnels in rock exhibiting significant time-dependent deformation.

ISSN:0008-3674    

DOI:10.1139/t81-004

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Certain simple problems in dynamic soil–structure interaction were investigated experimentally—in particular the rocking behaviour of rigid foundations on cohesionless soil. This was done using model tests in a geotechnical centrifuge, in order to preserve the correct level of stress in the soil.These tests observed the behaviour of model towers with rigid foundations of varying sizes and geometries. Perturbation of a tower allowed the dynamic properties to be measured and the stiffness of the foundation to be evaluated. Simple elastic theory satisfactorily predicted the observed behaviour, provided that appropriate assumptions were made about the soil stress under the foundation, and an empirical rule is suggested. The limitations of a more elaborate analysis are demonstrated. It was also possible to observe that the foundation stiffness for embedded foundations appeared to be overestimated theoretically and that the effect of dynamic interaction between adjacent towers appeared to be small.

ISSN:0008-3674    

DOI:10.1139/t81-005

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The behaviour of a clay element during the sampling operation is first analysed in the light of the limit state theory. The stress variation and the resulting distortion of the clay element during sampling is equivalent to a destructuration of the clay, and its mechanical properties are greatly affected. The causes of sampling disturbance are analysed and the principles which should govern the design of a good quality sampler are reviewed in the light of previous studies. It is shown how the reshaping of the sampling tubes can improve the sample quality. The new 200 mm sampler designed at Université Laval uses the overcoring technique to eliminate suction and to insure the recovery of large samples without a piston. The quality of these large samples has been proven to be equivalent to block samples. The advantages and limitations of the Laval sampler are discussed.

ISSN:0008-3674    

DOI:10.1139/t81-006

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A full scale investigation with six instrumented test piles has been carried out on the Saint-Alban test site in order to study the behaviour of friction piles in soft sensitive soils. The first part of this investigation, reported in this paper, deals essentially with the effects of pile driving on the induced pore pressures and their dissipation and on the disturbance of the clay around the pile.It is shown that the induced pore pressures at the pile tip ΔuT, and at the pile surface Δus, correspond to 1.6σvoand 0.8σvorespectively. If the failure pattern developed during driving is interpreted by means of the theories of expansion of cavities, it is shown that the induced pore pressures calculated at the pile–soil contact agree well with the measured values; these pore pressures are fully dissipated after 600 h.Immediately after driving, a decrease in the undrained shear strength varying between 0 and 30% was observed in a zone of 3 diameters around the pile. The strength in that zone was nearly fully recovered after the pore pressures had dissipated.The tip resistance measured during driving was quite in excess of the static zone penetration resistanceqc, indicating possible scale effects. The average unit skin friction was observed to decrease from a value in the order ofcuto about 0.10σvo′ and to be directly related to the pore pressures, i.e., to the effective stresses in the clay around the pile.

ISSN:0008-3674    

DOI:10.1139/t81-007

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Snow glide, slip of the entire snowpack over the ground, is not observed unless water reaches the ground interface. In this paper, snow gliding is approached from the point of view that a perfect slip condition is attained at the glide interface whereby a thin continuous water film is envisioned to exist between the snowpack and the ground. Two mechanisms are described by which the snowpack may move forward: (i) creep (defined as slow, viscous deformation) over roughness asperities under the condition that the snowpack conforms to the interface and (ii) rigid body sliding of the snowpack over the interface when it does not conform to the interface. Constitutive equations relating tangential drag on the snowpack to slip velocity are derived for these idealized cases, and the extension to the more realistic case where the processes compete is discussed.

ISSN:0008-3674    

DOI:10.1139/t81-008

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Slope instability along the banks of the South Saskatchewan River Valley has been a continual problem for Saskatoon's City Engineering Department since 1913. It has affected building and bridge foundations, damaged municipal roads and services, and interfered with park and playground development. Where the glacial till in the banks is overlain by lacustrine clays, silts, and sands, the lower portion of the slip surface invariably follows the stratigraphic contact between the till and the overlying materials. Piping of intertill stratified drift is the major cause of slope instability where the till is exposed at the surface. Groundwater from the natural infiltration and from lawn watering greatly affects the slope stability. Remedial techniques have consisted primarily of subsurface drainage systems.Increased pressure for development along the riverbank has led to the recent establishment of the Meewasin Valley Authority which has complete control of development within and along the river valley. Opposition to the Authority's establishment has been strong. Its success in controlling development near unstable slopes will only be proven with time.

ISSN:0008-3674    

DOI:10.1139/t81-009

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The accumulated experience on slope stability is reviewed with due consideration to the time-dependent behaviour of natural clays prior to failure. A consistent picture of the behaviour of both man-made and natural slopes is obtained, which applies to soft as well as stiff clays, in an intact or a fissured state. In all cases, creep deformations develop prior to failure, which can be used as an indicator of incipient failure. The strength mobilized at failure can be theoretically defined in a qualitative manner: it is intermediate to the critical state strength and the time-dependent limit state of the clay. Quantitatively, this strength is represented by thevalue corresponding to the critical state and by an empirical cohesive term in the order of 4–15 kPa in intact clays and of 0–2 kPa in fissured clays; these values apply to both cuttings and natural slopes.

ISSN:0008-3674    

DOI:10.1139/t81-010

出版商:NRC Research Press    

年代:1981

数据来源: NRC