934389 Interactive slope analysis using Spencer's method Sharma, S; Moudud, A Proc Conference Stability and Performance of Slopes and Embankments II, Berkeley, 29 June-1 July 1992 V1, P506- 520. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31)

Since the advent of the PC, analytical methods have been rou- tinely applied to slope analysis. The methods used are usually based on discretization of the potential failure mass into a series of slices. The method of Spencer (1973) is presented and critically examined. Some recommendations are made con- cerning its use, bearing in mind its very sensitive nature. Details discussed include: location of effective thrust line; mag- nitude of inter-slice forces; inclination of side forces; shape of failure surfaces; and introduction of a water-filled crack.

934390 Application of centrifuge modeling technique to slopes and embankments Znidarcic, D Proc Conference Stability and Performance of Slopes and Embankments !I, Berkeley, 29 June-1 July 1992 VI, P521- 537. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31)

Centrifuge modelling has found a niche as an alternative and complement to numerical techniques in geotechnical engineer- ing. A short review of the basics is presented, including scaling relations for slope stability and the principles of modelling of models. The philosophy and advantages of centrifuge model- ling and its principal difficulties are discussed. An example of the use of centrifuge modelling to study the effects of horizon- tal drainage on slope stability is illustrated.

Earth retaining structures

See also: 934082

934391 Ground settlements and drawdown of water table around an excavation Hsi, J P; Small, J C Can Geotech J V29, N5, Oct 1992, P740-756

Stress release and drawdown adjacent to excavations in satu- rated soils may lead to ground settlement. A case history where this was monitored in a congested urban area is described. A fully coupled finite element numerical model (Hsi and Small, 1992) has been used to simulate the displacements and changes in pore pressure. Comparisons are made between measured and predicted results.

934392 Retaining structures: displacement and design Simpson, B Geotechnique 1/42, N4, Dec 1992, P541-576

The 32nd Rankine Lecture. In the search for better methods of design for retaining structures, a variety of approaches has been used. Current trends towards using the partial factor method to estimate safety and serviceability and traditional methods are described. Many excavations have been moni- tored during this work. This has revealed the small strain stiff- ness of soils to be much greater than indicated by standard laboratory tests. This feature can be represented by the S- shaped curve and has been implemented in a new soil model. Finite element analysis using this soil model is used to study deep excavations for the British Library, London, and in soft clay in Singapore.

256A

934393 Deep basement in Aldersgate Street, London. Part !: Contractor's design and planning Marchand, S P lnst Civ Engrs Proc (?iv Engng V97, NI, Feb 1993, P19-26

Construction of a 24m deep basement in a severely restricted area is described. The geological profile is made ground over gravel then London Clay. Differential movements between the diaphragm wall and bearing piles during construction and their effects on construction and adjacent buildings were of primary concern. To stiffen the clay in front of the diaphragm wall and prevent long term softening, 5 rows of tensioned pin piles were installed, rather than a substantial ground slab. Instrumentation to be installed is discussed.

934394 Controlling the safety of geotechnical structures: a proposed approach Oliphant, J lnt J Geotech Geol Engng VIO, N4, Dec 1992, P273-289

Safety of geotechnical structures is usually assessed by theoret- ical analysis. Several design philosophies are outlined: global factor of safety; design using worst credible values; design using extreme values; limit state design with partial factors; and reliability theory. Parameter and system uncertainty are discussed. Each method should be considered as part of a design process, not an end in itself. In some cases it is not clear whether a design parameter is an upper or a lower bound on the parameter value. A limit state design method to overcome this problem is proposed and illustrated for a retaining wall.

934395 Influence of construction technique on the performance of a braced excavation in marine clay Smith, I M; Ho, D K H int J Num Anal Meth Geomech VI6, N12, Dec 1992, P845- 867

Finite element analysis with a simple linear elastic-perfectly plastic soil model has been used to study the performance of a braced excavation through working depths to collapse. A case study of a site with stratified deposits of marine clay and sand is illustrated. Influence of construction technique on strut loads and deformations is examined. Computed and observed behaviours are similar for the flexible construction used, rela- tively late installed low stiffness support. Computations sug- gest even a much 'stiffer' construction could not prevent large deformations under certain circumstances.

934396 Retaining wall with reinforced cohesionless backfill Saran, S; Garg, K G; Bhandari, R K J Geoteeh Engng Die ASCE Vl18, N12, Dec 1992, P1869- 1888

Limit equilibrium analysis is presented for a rigid wall retain- ing cohesionless fill under uniform surcharge loading and rein- forced by horizontal strips or mats not connected to the wall. Stability of an element of the failure wedge which forms along the back face of the wall is examined. Dimensionless charts are presented for estimation of lateral earth pressure on the wall and the height of its point of application. Model test results verify theoretical predictions. Practical design guidelines are given.

© 1993 Pergamon Press Ltd. Reproduction not permitted