916111 Degradation model for rock armour in coastal engineering Latham, J P Q J Engng Geol V24, N1, 1991, P101-118. (paper to the conference on Geological Materials in Construction, London, November 1989)

Quarried blocks from 1 to 20 tonnes are used in coastal engi- neering. Armourstone resistance to the agressive marine envi- ronment is a function of intrinsic, geometrical, and environmental factors. A degradation model is presented. Rock samples are first tested in an abrasion mill to simulate the wear process. Laboratory time is converted to site years using an equivalent wear time function derived from a combi- nation of 9 weighted parameters: block size, grading, initial shape, incident wave energy, zone of structure, climatic effects, water-borne attrition agents,concentration of wave attack, and mobility within the design concept. Examples are illustrated.

916112 Behaviour of soil-structure interfaces: experimental and numerical aspects (In French) Boulon, M Rev Fr Geotech N54, 1991, P27-37

Experimental data on pile friction are first presented, then results of direct shear tests between sand and constructional materials over a range of initial conditions, including constant normal stress, constant volume, and pseudo-odometric. A mathematical model is developed to describe interface beha- viour, which includes effect of shear direction and rheological interpolation. Predictions of the model are compared to exper- imental results. Finite element analysis using several interface models indicates the influence of dilatancy rate. A simple method is proposed for evaluation of mobilised friction along piles or reinforcing or support elements.

916113 Temperature effects on electrical resistivity of intact sandstones Kate, J M; Aggarwal, P K Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6-10 August 1990 V2, P987-994. Publ Rotterdam: A A Balkema, 1990

Electrical resistivity of materials is a temperature dependent parameter. Resistivity surveys should take into account tem- perature changes related to depth or proximity of natural or man-made heat sources. Equipment has been developed to measure resistivity of rocks over a range of temperatures. Measured and interpolated data for 3 sandstones are illus- trated in the range 30-150 deg C.

Physico-chemical properties

See also: 916014, 916027

916114 Electronsmotic strengthening of soft sensitive clays Lo, K Y; Inculet, I I; Ho, K S Can Geotech J V28, N1, Feb 1991, P62-73

The mechanism and effectiveness of electroosmotic strengthen- ing was examined in the laboratory using a purpose designed apparatus. Two soil types were used, overconsolidated Wal- laceberg clay and slightly overconsolidated soft sensitive Leda clay. Results demonstrate the efficiency of the apparatus. The electroosmotic consolidation curve is similar to the conven- tional consolidation curve. Preconsolidation pressure was increased by 51-88% with an applied voltage of 6V.

345A

Undrained shear strength increase of up to 172% and water content decrease up to 30% were possible. Using the technique of electrode reversal, a relatively uniform improvement in properties was achieved.

916115 Field test of electroosmotic strengthening of soft sensitive clay Lo, K Y; Ho, K S; Inculet, I I Can Geotech J V28, N1, Feb 1991, P74-83

A field test in Leda clay at the Gloucester test fill site is described. The specially designed equipment prevents gas accumulation around the electrodes and facilitates pore water removal without pumping. Settlement,shear strength, and voltage distribution were monitored during the experiment. Field vane tests showed uniform shear strength gain through- out the depth of the electrodes of 50% after 32 days, with surface settlement of 50ram. The treatment is effective and economic, meriting wider application.

916116 Mechanistic evaluation of mitigation of petroleum hydrocarbon contamination by soil medium Yong, R N; Rao, S M Can Geotech J V28, N1, Feb 1991, P84-91

The ability of soils to attenuate the transport of petroleum hydrocarbon (PHC) molecules has been studied. The nature of the PHCs, soil-contaminant interaction, changes in soil physi- cal properties due to contamination, and the possibility of enhancing ability to retard migration have been examined. It is proposed to coat soil surfaces with heavy organic polymers, which may change the clay minerals from highly hydrophilic to organophilic, such that the PHC molecules can be attenu- ated by van der Waals forces, hydrogen bonding, or adsorp- tion into interlayer space.

916117 Correspondence between membrane potential and conductivity Sen, P N Geophysics V56, N4, April 1991, P461-471

A model independent relation between the membrane poten- tial and conductivity is developed and tested against data from 27 rocks over a wide range of salinity. Corrections for clay platelet conductivity are included.

916118 Chemical and mineralogical controls upon the residual strength of pure and natural clays Moore, R Geoteclmique V41, N1, March 1991, P35-47

Results of laboratory shear tests are presented which demon- strate the separate effects of mineralogy and pore fluid chemis- try on the residual strength of clays. An attempt is made to identify the controls on residual strength of these parameters, following a brief review of shear strength and physicochemical behaviour of clays. Results suggest that residual strength of clays be considered as a changing property which alters according to the environmental conditions.

916119 Liquid limit and surface area of clays. Technical note Muhunthan, B Geoteclmiqne V41, N1, March 1991, P135-138

Atterberg limits are widely used in soil classification and have been empirically correlated with several engineering proper- ties. These correlations could be rationalised if the mecha- nisms controlling Atterberg limits were better understood. Low (1987) suggested that surface hydration is important to the behaviour of clays. An attempt is presented to develop a

© 1991 Pergamon Press pie. Reproduction not permitted