The effect of low temperature (77 K) deformation by drawing (80%) on the superconducting properties and structure of vanadium is studied. The structural elements (fragment boundaries) responsible for the observed changes of critical parameters are isolated. The electron-phonon coupling constant and the electron mean free path undergo most significant changes in these regions of rotational deformation localization, which have a high density of defects and are powerful sources of internal stresses. The dislocation density at the fragment boundaries is estimated.
One of the principal trends in rock mechanics is experimental assessment of the stress--strain state of a rock mass.Most of the present methods of stress measurement in a rock mass are based on the assumption of elastic behavior of the rocks. This is not always true, particularly for sedimentary strata.In such formations the rocks may exhibit both elastic and inelastic behavior, their ratio varying over a wide range and making the final result incorrect to some extent. Therefore in each individual case the experimental investigator must have a clear picture of the deformation properties of the rock mass in order to formulate the fundamental principles concerning the selection (or construction) of the most suitable model of the rock.To obtain additional information on the deformability of rocks we need special procedures and equipment.Furthermore, the properties must be assessed under field conditions and preferably at the same point at which the stresses are measured.The stresses and properties of the rocks in a rock mass may be determined either separately or simultaneously.For this purpose, instruments of the dilatometer type are used.a
The absolute stresses in rocks am determined by relief of an element of the rock mass with measuring instruments. Various types of relief are known: .the end face of a borehole, a core with a central borehole, a large-diameter borehole, or para!lel slots. Swain, magnetostrictior~ optical, hydraulic, and other gauges are used as the sensitive elements reacting to borehole deformations. To assess the stressed state in rocks of low or average strength. borehole hydraulic gauges are used in most vemions of the relief method. We shall examine the interaction of these instruments with a rock mass in a perturbed stress field formed when a slot is made.A borehole is driven from a mine working to the required depth and hydraulic gauges are installed in it. observing the requirements discussed in [1]. A slot is then made and the gauge located in its zone of influence records the change in pressure. The data is used to calculate the stresses in the rock mass. Note that if R is the borehole radius the distance between the borehobs and the slot must be at least 8R, The value of the principal stresses in the rock mass may then be obtained by solving the pflma~ T basis problem of elasticity theory for an infinite plane with an eUiptical orifice.Let the plane at infinity be subjected to forces q and p (Fig. 1) After formation of an elliptical cavity with center at the origin, the stressed state in its vicinity varies and each normal component will be the sum of the components in the principal and secondary stress field, for example, in polar coordinates:
%Since hydraulic gauges react only to the half-sum of the normal stresses, and o~ + o~ --o x~ + o~ then Institute of Mining, Siberian Branch, /(cademy of Sciences of the USSK Novosibirsk.
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