245A

934303 Rheological behaviour of silicate-formamide grouted sand Shah, D L; Shroff, A V Proc Ninth Asian Regional Conference on Soil Mechanics and Foundation Engineering, Bangkok, 9-13 December 1991 V1, P167-170. Publ Thailand." Southeast Asian Geotechnical Society, 1991

High penetrability chemical grouts are often used to reduce permeability and seepage in sandy subsoils. The time-viscosity and time-strength relations for a two component sodium sili- cate-formamide grout and its mixtures with sand have been examined. Initial low viscosity permits injection into cracks and voids impenetrable to cement grouts. Rate of reaction and strength are directly proportional to concentration of accelera- tor (calcium chloride) and formamide respectively. The raw gel is initially Newtonian, changing through viscous non- Newtonian, viscoelastic,to plastic.

Reinforced earth

See also: 934330, 934366

934304 Strain-based design method for the collapse limit state of reinforced soil walls or slopes Lo, SC R; Xu, D W Can Geotech J V29, N5, Oct 1992, P832-842

A method is presented to predict failure of reinforced earth walls or slopes as a result of reinforcement failure. The rupture surface is modelled by a generalised log spiral selected by numerical optimisation. The limit equilibrium equations are established by examining equilibrium of soil slices parallel to the reinforcing element. Reinforcement with depth-dependent nonlinear load-extension response, nonuniform reinforcement layout, and soil dilatancy can be accommodated. The method is validated by comparisons with finite element simulations and field data on failures.

934305 Use of reinforcement geotextiles to support road embankments over areas subjected to mining subsidence Kempton, G T Highways Transp V39, NI2, Dec 1992, P21-31

Large areas of the UK are underlain by mines for which no records exist. The risk of subsidence is real but difficult to quantify. The use of geotextile reinforcement of foundations for roadway embankments where subsidence hazards are pos- sible is described. The geotextile acts as a tension membrane in the event of crownhole formation. Design formulae are presented and choice of suitable geotextiles discussed. A typi- cal reinforced embankment design is illustrated.

934307 Treatment of expansive soils for reducing swell potential and increasing strength Stamatapoulos, A C; Christodoulias, J C; Giannaros, H C Q J Engng Geol V25, N4, 1992, P301-312

Development is underway of the plane north and north east of Thebes, Greece. Surface soils are mostly of the expansive 'terra rossa' type. Mineralogy and swelling behaviour have been characterised. Mechanical stabilisation, treatment with lime-rich water, and use of additives were investigated as methods to alleviate seasonal shrink-swell movements. Surcharge and/or excavation and recompaction proved a suc- cessful treatment. The most effective additives were (in decreasing order): 4% cement plus 2% lime; 6% lime; 6% cement; 6 0 polybutadiene; and lime in free water.

934308 Slope stabilisation using lime Rogers, C D F; Bruce, C J Proc Conference on Slope Stability Engineering: Developments and Applications, Isle of Wight, 15-18 April 1991 P395-402. Publ London: Thomas Telford, 1991

The principles and practices of stabilisation of clay slopes by lime slurry pressure injection, lime columns, and lime piles are described. Laboratory data on the strengthening effects of lime are presented for the latter two techniques. Applications to new, failing, or failed slopes are discussed. These techniques have many possible uses, but good understanding of the processes involved is necessary for their proper application.

934309 Design concept of treated ground by premixing method Umehara, Y; Zen, K; Yoshizawa, H Proc International Conference on Geotechnical Engineering for Coastal Development, GEO-COAST'91, Yokahama, 3-6 September 1991 VI, P519-524. Publ Japan: Coastal Development Institute of Technology, 1991

In the premixing method, sandy backfill material is treated first with cement then with a chemical stabiliser to prevent cement dispersion in water, prior to backfilling. Cyclic triaxial tests have been used to determine minimum cement content to prevent liquefaction. About 20% excess above the laboratory determined value is recommended for field applications. Seis- mic response of treated ground has been evaluated using the computer code FLUSH. Triaxial and unconfined strength parameters after curing have been determined for design purposes.

Soil compaction

Soil stabilisation

934306 Use of rice husk ash to enhance lime treatment of soils Ali, F H; Adnan, A; Choy, C K Can Geotech J V29, N5, Oct 1992, P843-852

Rice husk ash is readily available and cheap in many coun- tries. Its application with lime to improve compaction, strength and durability characteristics of a local residual gran- ite soil in Malaysia is described. Reaction products responsible for the improvement were examined at various stages of cur- ing by X-ray diffraction. RHA enhances both strength devel- opment and durability of the lime stabilised residual soil.

934310 Design of dynamic compaction Porain, C J; Rodriguez, J A Can Geotech J V29, N5, Oct 1992, P796-802

Determination of number of tamper drops, grid spacing, and layout of passes for dynamic compaction treatment is difficult where subsurface conditions are irregular and not easily quan- tifiable. Simple empirical design procedures may be inade- quate. A new rational and improved D C design method is presented, which is based on extensive model testing of impact response of dry sands. Field data from several sites of unsatu- rated sandy soils confirm the validity of the method. With suitable calibration, extension to other types of soil is possible.

© 1993 Pergamon Press Ltd. Reproduction not permitted