土木工程岩土工程裂隙岩体毕业论文中英文资料对照外文翻译文献综(3)

土木工程岩土工程裂隙岩体毕业论文中英文资料对照外文翻译文献综述

This problem amounts to evaluating the ultimate load Q﹢ beyond which failure will occur, or equivalently within which its stability is ensured. Due to the strong heterogeneity of the jointed rock mass, insurmountable dif culties are likely to arise when trying to implement the above reasoning directly. As regards, for instance, the case where the strength properties of the joints are considerably lower than those of the rock matrix, the implementation of a kinematic approach would require the use of failure mechanisms involving velocity jumps across the joints, since the latter would constitute preferential zones for the occurrence of

failure. Indeed, such a direct approach which is applied in most classical design methods, is becoming rapidly complex as the density of joints increases, that is as the typical joint spacing l is becoming small in comparison with a characteristic length of the structure such as the foundation width B.

In such a situation, the use of an alternative approach based on the idea of homogenization and related concept of macroscopic equivalent continuum for the jointed rock mass, may be appropriate for dealing with such a problem. More details about this theory, applied in the context of reinforced soil and rock mechanics, will be found in (de Buhan et al. 1989; de Buhan and Salenc ,on 1990; Bernaud et al. 1995).

Macroscopic Failure Condition for Jointed Rock Mass

The formulation of the macroscopic failure condition of a jointed rock mass may be obtained from the solution of an auxiliary yield design boundary-value problem attached to a unit representative cell of jointed rock (Bekaert and Maghous 1996; Maghous et al.1998). It will now be explicitly formulated in the particular situation of two mutually orthogonal sets of joints under plane strain conditions. Referring to an orthonormal frame O 1 2whose axes are

placed along the joints directions, and introducing the following change of stress variables:

such a macroscopic failure condition simply becomes

where it will be assumed that

A convenient representation of the macroscopic criterion is to draw the strength envelope relating to an oriented facet of the homogenized material, whose unit normal n I is inclined by an angle a with respect to the joint direction. Denoting by n and nthe normal and shear components of the stress vector acting upon such a facet, it is possible to determine for any value of a the set of admissible stresses ( n , n) deduced from conditions (3) expressed in terms of ( 11, 22 , 12). The corresponding domain has been drawn in Fig. 2 in the

particular case where m .

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