Multi-fractal evaluation method for three-dimensional rock structure surface shear mechanical behavior

Abstract

The invention provides a three-dimensional rock structure surface shear strength evaluation method. The method comprises the following steps of (1) acquiring three-dimensional topography data of a rock structure surface; (2) calculating multi-fractal characteristic parameters delta D (q) and delta a (q) of the structure surface according to a multi-fractal calculation formula, and representing the roughness of the three-dimensional rock structure surface by using the delta D (q) and the delta a (q); (3) carrying out a shear mechanics test on the rock structure surfaces with different roughness degrees to obtain shear mechanics parameters, and calculating the values of the delta D (q) and the delta a (q) of all the structure surfaces according to the step (1) and the step (2); and (4) testing a Barton shear formula improved by calculation data fitting by the step (3) to obtain the three-dimensional rock structure surface shear strength formula expressed by the delta D (q) or the delta a (q). Therefore, the rock structure surface shear strength can be evaluated by the three-dimensional rock structure surface shear strength formula in the engineering practice. The formula overcomes the defect that the Barton formula only considers about the two-dimensional characteristic and artificial estimation of joint roughness coefficient (JRC) of the structure surface, so that a method for comprehensively evaluating the shear strength characteristic of the rock structure surface is provided.

Description

technical field [0001] The invention provides a method for evaluating the shear strength of a three-dimensional rock structure plane, which belongs to the field of rock mechanics. Background technique [0002] The study on the shear strength of rock structural planes has a history of nearly half a century. Up to now, no less than ten influential shear strength models have been proposed, and the typical ones are shown in Table 1. [0003] Table 1 Representative shear strength models [0004] [0005] Remarks: Repeated letters and symbols in the above formulas will not be noted. [0006] The above shear strength models play an important role in rock engineering practice, but due to the complexity of the mechanical properties of the rock structural plane itself, the existing shear strength formulas are either too simplified and ignore some important influencing factors, or the parameters are relatively complex. Many and difficult to determine, so it is difficult to be ...

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Problems solved by technology

[0006] The above shear strength models play an important role in rock engineering practice, but due to the complexity of the mechanical properties of the rock structural plane itself, the existing shear strength formulas are either too simplified and ignore some important influencing factors, or the parameters are relatively complex. Many and difficult to determine, so it is difficult to be widely used in engineering practice

At present, the shear strength formula proposed by Barton in 1977 is commonly used in practical engineering , but the main defect of this formula is that ① the roughness coefficient JRC It must be estimated artificially, which has a lot of subjectivity; ②The characterization of roughness is limited to the two-dimensional outline of joints, which is not comprehensive enough compared with the structural surface

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