摘要:

We have studied the field behaviour of the abutments of 15 bridges which abutments have experienced horizontal movements. These abutments were founded on piles through a soft layer. For all these structures, the piles have been installed before the approach embankments were built or as soon as they were built.Considering the structural characteristics of the piles and the compressibility and geometry of the soft layer, the conditions for which such movements of the abutments are likely to occur are given. When the abutments are of the type built at mid-height of the embankment, an upper limit for the horizontal movement of the abutment is proposed. Several solutions are suggested to avoid the movements of abutments.

ISSN:0008-3674    

DOI:10.1139/t72-001

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

This paper deals with the bending of slender precast concrete piles which are driven in segments 10 to 14 m in length and spliced in the field by means of rigid steel couplings. The requirements of the Swedish Building Code for allowable bending of these piles are reviewed and the method of inspecting the bending is described. The inspection is performed by lowering a slope inclinometer through a pipe, which is cast centrically in the pile and attached to special couplings by which access all through the pile is obtained.By the inclinometer the inclination and the direction of the inclination is measured. The results are used for determining the location of the pile in the ground and the bending of the pile. Mathematical expressions for this are derived.In Swedish practice, when judging a pile, the bending of the pile segments is treated separately from the bending of the pile over the pile splices, as the latter involves the question of squareness of the joint couplings in casting. The bending of a segment is judged in terms of change of inclination per metre of pile and of bending radius over the length of the segment. A typical example is given on how to present and evaluate the measuring results.

ISSN:0008-3674    

DOI:10.1139/t72-002

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A short review of the complexities in the specification of physical properties for the solution of thermal problems in freezing and thawing soils is presented. The differential equations governing the conduction of heat, in which latent heat is considered as a heat source, are stated. An equivalent convolution variational theorem is used to construct a two-dimensional finite element model with linear variation of temperature within the element. Two time step idealizations of the equations are described and alternative forms of the latent heat matrix are derived. Some results obtained with the simplest latent heat matrix are presented, which include a problem of complex geometry, to illustrate the versatility of the technique.

ISSN:0008-3674    

DOI:10.1139/t72-003

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

It has often been shown by previous investigators that the existing pile driving formulas yield bearing capacities which usually do not stand in good correlation to the actual bearing capacities of piles in sand. These poor correlations have always been attributed to the formulation of the equations.Based on the observations made on a very large foundation built in an homogeneous sand deposit it is shown in the present paper, that the poor quality of the usual pile driving formulas originates essentially in the estimate of the driving energy; while it is assumed that each blow delivers a constant energy equal toW × Hfor drop hammers, it appears actually that the energy delivered by a given equipment varies systematically from blow to blow. This conclusion, drawn from a statistical analysis of 478 driving records, is confirmed by the driving tests made on four instrumented piles.The results of 45 load tests also confirm this conclusion in showing no correlation between the actual bearing capacities and the estimated driving energy or the bearing capacities computed from five different formulas. The observations also show a possible time effect on the bearing capacities of concrete piles in sand.

ISSN:0008-3674    

DOI:10.1139/t72-004

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Most of the existing theories of creep have been developed from two different viewpoints: micromechanistic and macroanalytical. The former deal with events occurring at the atomic level and provide knowledge of the processes that control creep. The latter are based on certain macroscopic experimental findings and represent, in fact, an extension of the theory of plasticity to include time and ltemperature effects. Both the micromechanistic and macroanalytical approaches lead to fruitful resuts and each can benefit from the other. However, although the former has the advantage of being derived from physical concepts, the use of the latter is often preferred in practice if it provides basic relations that are broad in scope and can lead to improved procedures for designing structures.In this paper, a macroanalytical view of the problem of creep of frozen soils is presented. The proposed theory of creep has been developed mainly with the purpose of being used as a basis for solving a specific soil engineering problem, i.e., the bearing capacity of buried footings and anchors.Since the problem is itself rather complex, it was endeavoured to present the creep information in a relatively simple mathematical form. The theory, while using certain concepts and data from the frozen soils literature, follows more closely, nevertheless, the methods usual in certain engineering theories of creep of metals.

ISSN:0008-3674    

DOI:10.1139/t72-005

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

This study summarizes the information given in the literature as well as observations made by the author. The effects of driving piles on remolding, stresses, and properties of the clay are considered. It is concluded that timber piles cause strong remolding of a zone extending to 10–15 cm from the pile surface. Strength and deformation properties will undergo changes beyond this zone as well. Pile type, pile density, soil properties, and driving conditions influence the results. There seems to be very small changes in the average water content, since the reduction adjacent to the pile is counter-balanced by an increase between the piles. The undrained shear strength adjacent to the pile is in one case found to be much higher than the skin friction at failure.

ISSN:0008-3674    

DOI:10.1139/t72-006

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A number of uplift tests have been conducted on anchors proposed for use to support high voltage transmission line towers both for the conventional four legged structure and for the guyed-type structure with a single central footing. Tests were carried out at seven sites, six in the Toronto-Barrie Area and one at Thunder Bay, Ontario. The soil conditions included very dense till, soft clay up to 130 ft (39.62 m) in depth, dense sand and gravel and loose to compact silty sand. The test installations included both power installed multi-helix anchors and grouted anchors with a single reinforcing rod. These were installed at various depths. In the very deep clay only multi-helix anchors were tested. Most of the tests were in uplift on anchors installed vertically. A few group tests were conducted both in uplift and compression. The results of all of the tests are presented along with fairly detailed information on the properties of the soil at each site. An attempt to analyze the results of the helix anchor tests using simplified bearing theory was made. The grouted anchor tests were analyzed using either frictional or adhesive bond theory depending on the soil type. The results indicate that the theories using conventional soil properties provide reasonable design parameters for initial planning. Further confirmation by fullscale testing, however, is essential.

ISSN:0008-3674    

DOI:10.1139/t72-007

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Deep sockets into bedrock are often used to achieve large capacities for caissons. Most of the available design methods are mainly empirical with little or no relationship to thein situquality of rock. Bearing pressures and socket skin friction values adopted seem to be conservative in the absence of reliable field information. This paper deals with the problems associated with the design of deep socketed caissons.A concise review of the regional case histories and available design methods involving deep sockets into bedrock are presented. Various methods of testing rock in the laboratory and in the field for obtaining the desired design parameters are discussed. The application of laboratory and field test results in design are given. Problems associated with the construction and inspection of the caissons are summarized.

ISSN:0008-3674    

DOI:10.1139/t72-008

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A seal of bentonite, water, and methanol is shown to possess suitable properties for sealing piezometers in frozen soil. The methanol additive depresses the freezing temperature of the bentonite seal without significantly altering its swelling characteristics.

ISSN:0008-3674    

DOI:10.1139/t72-009

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A unique characteristic of many naturally cemented sensitive soils is that they are made up of finely ground fresh rock debris, "rock flour", much of which is very susceptable to chemical weathering or decomposition. Many of these minerals can be identified by X-ray diffraction. The decomposition of these minerals produces secondary products which can act as effective natural cements. A process is outlined whereby the sequence of deposition, weathering and cementation can account for the observed mechanical behaviour of naturally cemented soils.

ISSN:0008-3674    

DOI:10.1139/t72-010

出版商:NRC Research Press    

年代:1972

数据来源: NRC