摘要:

An experimental study is presented on the point bearing capacity of piles in rock. The bearing capacity for granite, limestone, and sandstone was found to be approximately four to six times the unconfined compressive strength of the rock material when the load was applied perpendicular to the rock surface. The ultimate bearing capacity was affected by the inclination of the applied load and by the penetration depth. The ultimate strength decreased rapidly when the inclination exceeded 45°. The strength increased with increasing penetration depth. The increase for granite and sandstone was 25 to 50% when the depth increased from 0 to 1.0 times the point diameter. The corresponding increase for limestone was 60 to 70%.The point bearing capacity was calculated by the Coulomb–Mohr and by the Griffith failure theories. The test results indicated that the effect of the inclination of the rock surface and of the penetration depth for granite and sandstone was less than calculated. Satisfactory agreement was found for the limestone between measured and calculated values. Comparisons with the Griffith failure theory indicated that the measured failure loads were approximately twice the calculated failure loads.

ISSN:0008-3674    

DOI:10.1139/t71-016

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Observations are reported on the stress–strain behavior at −9.5 ± 0.5 °C of four types of ice obtained from the St. Lawrence River. The ice was subject to nominal rates of strain covering the range 2.1 × 10−5 min−1to 5.8 × 10−2 min−1. A ductile-to-brittle transition was observed for strain rate of about 10−2 min−1. In the ductile range the four types had an upper yield stress that increased with strain rate according to a power law.

ISSN:0008-3674    

DOI:10.1139/t71-017

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Observations are reported on the failure and use of freshwater ice covers for vehicular traffic. The study showed that good quality ice covers can support loads of up toP = 250 h2, wherePis the total load in pounds andhis the thickness of the ice in inches. Failures were reported, however, for loadings as low asP = 50 h2. Factors contributing to the failure of covers for loading less thanP = 250 h2were: vehicle speed, thermal stress due to drop in temperature, and fatigue and quality of the cover. The results are discussed with reference to Westergaard's equations for the maximum stress due to circular loads on an elastic plate resting on an elastic foundation. Information is presented on the elastic and strength properties of ice covers required for theoretical calculations. Experience in the construction and use of ice roads and parking areas is described.

ISSN:0008-3674    

DOI:10.1139/t71-018

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A theory is given which enables variable permeability and compressibility, large strain, and non-Newtonian viscous effects in the soil skeleton to be considered in the one-dimensional consolidation of saturated soil. The first three of these are fairly well understood phenomena and their influence on field behavior is predictable. The last, however, is much more open to interpretation and has been included to cover laboratory testing of thin samples where viscous effects are often known to be important. The rheological model used for the soil skeleton is of the same general form as that used by Gibson and Lo in their investigation of linear behavior in clays. However, in the present case nonlinear physical laws of a form known to fit the experimental data more closely have been used. This makes the governing equations nonlinear and they are correspondingly more difficult to solve. The principal theoretical results for settlement and pore pressure are given in a form convenient for practical use and a procedure is given whereby the basic soil parameters can be determined from a laboratory settlement curve. By using the parameters so obtained the theoretical midplane pore pressure can be computed and when compared with the experimental curve this gives a stringent test of the adequacy of the theory. Experimental results for three different clays are given, and the theory shows encouraging agreement with these.

ISSN:0008-3674    

DOI:10.1139/t71-019

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Settlement observations have been taken over a period of about 6 years for two multistory buildings on a clay till. The CN Tower is founded on spread footings and the Avord Armson on Franki expanded base concrete piles; both buildings have settled a maximum of about 3 cm (). The settlement measurements showed a rapid response to loading during the construction period. Analysis of the foundations by elastic theory is shown to account satisfactorily for the overall settlement pattern during the construction period. The modulus of elasticity derived from the observations is stress dependent, decreasing with increasing load intensity. A small amount of long-term settlement has occurred at the end of construction; after 6 years it is less than about 20% of the total. Predictions of settlement using parameters obtained from soil samples taken at the sites are unrealistically high when compared with measured settlements.

ISSN:0008-3674    

DOI:10.1139/t71-020

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Permafrost, or perennially frozen ground, occurs widely throughout the northern half of Canada. Experience has shown that special design and construction techniques are required for building on permafrost in order to avoid disturbing the delicate thermal balance that preserves the frozen ground. The state of knowledge is reviewed with respect to site investigations, foundation designs, water supply and sewage disposal, the construction of transportation facilities, and the influence of surface flooding, drainage and other disturbances on the ground thermal regime. Attention is drawn to an extensive literature and research needs are outlined.

ISSN:0008-3674    

DOI:10.1139/t71-021

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The Burlington Bay Skyway is founded on a deep baymouth bar which is believed to be about 10 000 years old and to be normally loaded with respect to present ground level. Beneath the northern half of the bar there is a considerable depth of clay, which is also believed to be normally loaded under the weight of the bar. Bedrock occurs directly beneath the southern half.The skyway is symmetrical about Burlington channel, which is approximately centrally located along the length of the bar. Foundations include 74 piers and the abutments. Two main piers are carried on steel H-piles acting in friction, while 20 other piers on the north side are founded on short timber piles. All other piers, and the abutments, are founded on spread footings. The superstructure is of steel construction incorporating plate girder and rolled steel beam spans with continuity in units of three and four spans, respectively. Computations carried out during design indicated that differential settlements could exceed tolerable limits for continuous spans. Provision for shimming was therefore made, and settlement observations taken to provide the necessary control.The results of the settlement readings are presented primarily as a case history, along with a number of unusual features in the foundation subsoil arising out of its origin as a deep bar deposit.

ISSN:0008-3674    

DOI:10.1139/t71-022

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Most previous studies of frost heave and associated frost heaving pressures have been concerned with the process of ice lensing and ice segregation, and the primary mechanism used to explain the related phenomena of heave and pressure is seen to be consistent with the process of formation of ice lenses. Thus, while certain investigators may disagree on various details, there appears to be general agreement on the mechanisms which form the basis for the so-called capillary model for the prediction of frost heaving and associated pressures. In addition, various criteria used for the assessment of frost susceptibility rely implicitly on the admissibility of this model as their rationale.This study questions the advisability of using a singular capillary model, in view of the wide range of conditions and constraints prevailing at any one time. Since soil freezing involves moisture movement and associated resultant volumetric expansion at both the macroscopic and microscopic scale arising from temperature and osmotic gradients, it is clear that a comprehensive theory to rationally explain heave and (or) heaving pressures is needed to account for all major factors which influence the total response of the frozen soil system. In this respect, the results of a critical examination of recent field and laboratory tests performed at McGill University and elsewhere are used to show that the available theories may be too restricted in scope to explain all facets of the observed behavior of frozen natural soils. To overcome the shortcomings noted above, an extended generative mechanism is developed and procedures for the examination of actual results are presented.

ISSN:0008-3674    

DOI:10.1139/t71-023

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Results of an instrumented test excavation in Welland clay are presented with analysis, discussion, and conclusions. The field investigation includes an observation of a deep vertical slope failure as well as an inclined stable slope, and measurements of pore pressure and surface strain. The averagein situundrained strength indicates that the soil deposit excavated in the area is not soft.

ISSN:0008-3674    

DOI:10.1139/t71-024

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The Townline road–rail tunnel is being constructed beneath the relocation of the Welland canal to the east of the city of Welland. Construction is by opencut and cut-and-cover through up to 80 ft (24 m) of lacustrine clays and clay tills. The lower stratified zone in the lacustrine clays has a minimum shear strength parallel to the bedding in some critical layers. Slope stability studies involved detailed sampling and testing, including block samples and 5-in.(13-cm) tube samples, and correlations with previous landslides in the area. These studies demonstrate that the mechanism of landslides in this stratigraphy involves a long flat portion of failure surface in the lower stratified zone, and that the shear strength available along this portion of the failure surface is consistent with the minimum shear strengths measured parallel to the bedding. Slopes as flat as 8.5:1 are required in areas which combine the deepest cuts and deepest overburden deposits.The concrete tunnel structure is being founded on bedrock consisting of a gypsiferous dolomite containing thick layers and lenses of essentially pure gypsum. Within the upper broken zone of the bedrock and some thin pervious lenses of sand and gravel immediately overlying the bedrock is an aquifer zone which is a major source of groundwater. Prior to construction, the piezometric level in this aquifer was approximately at the ground surface. The groundwater level in the aquifer zone had to be drawn down during construction and must be controlled throughout the life of the structure to provide for the stability of the overburden slopes. At the same time, the gypsum beneath the tunnel structure will be maintained intact by a drainage scheme which essentially isolates the rock beneath the structure from future groundwater flow, thereby precluding any significant solutioning of the gypsum.

ISSN:0008-3674    

DOI:10.1139/t71-025

出版商:NRC Research Press    

年代:1971

数据来源: NRC