Laboratory studies of some geotechnical properties of clayey sands of the ‘Continental terminal’ of the Ivory Coast (In French)

54A 892022 Borehole restoration methods and their evaluation by stepdrawdown tests: the case history, of a detailed study in Northern Italy Clark, L; Radini, M; Bison, P L Q J Engng Geoi V21, N4, 1988, P315-328 The effectiveness of borehole restoration techniques on recharge boreholes was assessed by repetitive step-drawdown tests. The step-drawdown tests were run with up to 10 steps and repeated up to 5 times on a single borehole. Borehole restorations after clogging with recharge show that chemical methods of acidization and polyphosphate dispersion are more effective than physical methods such as surging by pumping. Test analyses confirm that the squared relationship of well loss in the Jacob equation is valid in uniform aquifers where total drawdown is a small proportion of the saturated thickness. Auth.

Properties of Rocks and Soils See also: 892253. 892256 892023 Clays of eastern Canada and their contribution to the understanding of the behaviour of clay (In French) La Rochelle, P; Tavenas, F; Leroueil, S Can Geotech J V25, N3, Aug 1988, P413-427 A brief summary of much of the work done on clays in Canada over the past 25 years is presented, with emphasis on sensitive clays. The development of suitable sampling techniques for sensitive clays and the application of limit and critical state concepts to clays are discussed. Application to practical problems, slopes, embankments, and foundations, and effective stress analysis and consolidation of sensitive clays are examined. 81 refs. 892024 Laboratory studies of some geotechnical properties of clayey sands of the 'Continental terminal' of the Ivory Coast (In French) Guei, A; Ahoua Don Mello Proc Ninth Regional Conference for Africa on Soil Mechanics and Foundation Engineering, Lagos, Sept 1987 V1, P63-71. Publ Rotterdam." A A Balkema, 1987 Results of laboratory tests to determine geotechnical properties of a clayey sand, such as plastic and liquid limits, bearing capacity and dry density, are presented. Graphical presentation shows the sands are homogeneous, relatively compressible and permeable, have good shearing resistance, and that plasticity and percent fines seem to increase with depth. 892025 Investigating the problem soils of Nigeria Adesunloye, M O Proc Ninth Regional Conference for Africa on Soil Mechanics and Foundation Engineering, Lagos, Sept 1987 VI, P103-112. Publ Rotterdam: A A Balkema, 1987 Geotechnical data on problem soils in Nigeria are limited. Description, distribution and testing methods for 3 types of problem soils, high compressibility and low strength, expansive and collapsible, are discussed. Existing data from borehole logs are presented.

Composition, structure texture and density See also. 892342 892026 Method for evaluating the representative elementary volume based on a joint survey of rock masses Oda, M Can Geotech J V25, N3, Aug 1988, P440-447 To describe the hydromechanical properties of a statistically homogeneous rock mass as those of an equivalent continuum, it is necessary to determine the representative elementary volume, the minimum volume beyond which any submass behaves essentially like the whole rock mass. A simple general method to determine REV is presented, based on the crack tensor method of description of complicated joint systems. It is concluded that the size must be at least three times larger than a typical joint trace length. 892027 Density of granular materials derived from X-ray photographs: calibration,reliability, and recommended procedures Morin, P Can Geotech 1 1/25, N3, Aug 1988, P488-499 X ray photographs of sample cores are used to describe undisturbed sedimentary structures. The film density method of interpretation has been improved by including the effects of grain size, chemical composition and pore fluid present in the material. A simple procedure to interpret X ray radiographs is presented, and precision and limitations of the method discussed. 892028 Extraction and characterisation of organics from two Champlain Sea subsurface soils. Note Yong, g N; Mourato, D Can Geotech J V25, N3, Aug 1988, P599-607 To determine whether organic materials are present in subsurface soils in significant quantities, two Champlain Sea clay soils were studied. Organic contents of 0.5% were found at depths to 14.2m. Extraction, analysis, and classification of the organic content are described. Compositional and structural aspects of the extracts were investigated using infra-red spectroscopy and scanning electron microscopy. 892029 Minimum test specimen for gradation analysis. Technical note Howard, A K; Horz, R C Geotech Test J VII, N3, Sept 1988, P213-217 Minimum test specimen sizes are recommended on the basis of whether the absence or presence of one particle of maximum particle size present in the soil will affect the accuracy of the test by one percentage point. The minimum size should be at least 100 times the mass of an idealised maximum size particle. 892030 Conceptual model for soils containing large gas bubbles Wheeler, S J Geotechnique V38, N3, Sept 1988, P389-397 Offshore gas bearing sediments contain gas bubbles typically much larger than normal void spaces, so they cannot be considered simply as occluded bubbles in the pore water which affect pore fluid compressibility. A conceptual model of a matrix of saturated soil surrounding isolated gas filled cavities which are at fixed sites within the soil mass is described. Gas

.D 1989 Pergamon Press plc. Reproduction not permitted