852043 Experimental test of P-wave anisotropy in stratified media Melia, P J; Carlson, R L Geophysics V49, N4, April 1984, P374-378 Laboratory measurements were carried out to measure the compressional wave velocities parallel and perpendicular to layering in fabricated samples consisting of varying proportions of glass and epoxy. Results suggest that the frequency dependence of anisotropy in layered media is a function of the proportions of the materials, as well as the thickness of the layers.
852044 Causes of compressional-wave anisotropy in carbonatebearing, deep-sea sediments Carlson, R L; Schaftenaar, C H; Moore, g P Geophysics V49, NS, May 1984, P525-532 Laboratory tests on sediment samples were performed to determine the principle mechanism causing acoustic anisotropy in carbonate bearing, deep sea sediments. It is concluded that: (1) these sediments may be regarded as transversely isotropic media, (2) there is a preferred orientation of calcite, but this does not contribute significantly to velocity anisotropy, and (3) the principal cause of the anisotropy is the bedding with anisotropy increasing markedly with depth.
852045 Capillary effects on dynamic modulus of sands and silts Shiming Wu; Gray, D H; Richart, F E J Geotech Engng Div ASCE VllO, NGTg, Sept 1984, Pl1881203 Resonant column tests of five fine-grained cohesionless soils showed the influence of capillary stresses on values of the lowamplitude shear modulus, G. This influence was found to be greatest for the soils having the smallest effective grain diameter, D, and for the lowest external confining pressure. The maximum capillary influence developed at degrees of saturation between 5% and 20% for the soils tested. For the soil with the smallest D, the maximum G was about two times G for a lowest external confining pressure of 98kN/m. This latter pressure would correspond roughly to 6.1m of overburden of incompletely saturated soils. Therefore, it would be expected that capillarity would affect in situ shear wave velocity measurements required for the dynamic design of shallow footings, runways, or other structures supported by soil near the ground surface. An empirical expression was developed which permits corrections of the value of G, measured at a particular degree of saturation, to the degree of saturation expected in prototype conditions. Auth.
852046 Liquefaction and fabric of sand Nemat-Nasser, S; Takahashi, K J Geotech Engng Div ASCE VllO. NGTg, Sept 1984, P12911306 It is shown for simple shearing that the liquefaction and densification potentials of a cohesionless sample of sand do not necessarily decrease because of preliquefaction or because of large amplitude (drained) prestraining. In fact, in simple shearing, the resistance to liquefaction (undrained) or densification (drained) of a preliquefied sample actually increases, as a result of the concomitant densification, if the preliquefaction is terminated at zero residual shear strain, whereas this resistance is reduced considerably if the preliquefaction is terminated at zero residual shear stress. The inherent anisotropy associated with dry pluviating and moist tamping sample preparation techniques is shown to affect the sample response to consolidation and to simple cyclic shearing. It is found that, within each cycle of simple shearing, the induced anisotropy is essentially wiped
out in the neighbourhood of the zero shear strain (but not at zero shear stress) and the anisotropy that remains at this state basically stems from the sample preparation technique. With the aid of the dilatancy-fabric relation proposed by NematNasser for simple shearing, the volumetric strain of the sample is estimated using a simple distribution function for illustration purposes, and the results are compared with the experimental data. Auth.
852047 Simplified procedures for assessing soil liquefaction during earthquakes lwasaki, T; Arakawa, T; Tokida, K Soil Dynam Eartlul Engng V3, N1. Jan 1984, P49-58 Two simplified methods based on a liquefaction resistance factor and a liquefaction potential index are proposed to evaluate the liquefaction potential of saturated sandy soils. To prove the effectiveness of the proposed methods, the values of liquefaction resistance factor and potential index at 64 liquefied sites and 23 non-liquefied sites during six past earthquakes are calculated. Shaking table tests on soil liquefaction are carried out for the saturated sandy model ground. Several application methods using the liquefaction resistance factor, the excessive pore water pressure induced in the saturated sandy soils and the effects of soil liquefaction on the resistance properties of ground surrounding structures are described.
Classification and identification 852048 Unified rock dassification for drilling and boring Adler, L; Krishnan, G V Proc 6th Rapid Excavation and Tunneling Conference, Chicago, 12-16 June 1983 V1. P157-174. Publ New York: AIME, 1983 Unified classification permits a quick and rough estimate of the key parameters for boring in a specified rock. Identification of rock, borehole and machine characteristics are made and then estimates of the drill thrust, rotation speed, penetration rate, bit life and power.
852049 Rock mass classification scheme for the planning of caving mine drift supports Kendorski, F S; Cummings, R A: Bieniawski, Z T; Skinner, E H Proc 6th Rapid Excavation and Tunneling Conference, Chicago, 12-16 June 1983 V1, P191-223. Publ New York. AIME, 1983 The development is described of a classification system to aid planning of drift support in mines using block, panel or mass caving mining, by generating an easily-obtained drift support requirement estimate on the basis of ordinary exploration data.
852050 Selection of heading machines for excavation in coal measure rocks - application of rock classification approach Ghose, A K Proc 6th Rapid Excavation and Tunneling Conference, Chicago, 12-16 June 1983 V1, P224. Pub/New York." AIME, 1983 Application of a rock mass rating system, with appropriate roadheading machine recommended for each rock mass class, and simple index tests for evaluating the classification parameters for brittleness and abrasiveness are described.