Method for calculating shear strength index of rock mass structural plane

Abstract

The invention discloses a method for calculating shear strength index of rock mass structural plane. The rock mass structural plane undergoes multiple direct shear tests under different normal stresses; shear damage zone of the structural plane is scanned and effective area of the shear damage zone is calculated; according to a formula, effective average normal stress sigma n and effective average shear stress tau n under different normal stresses are calculated, and a scatter diagram of effective average shear stress under different effective average normal stresses is drawn in the rectangular coordinate system of sigma n-tau n; scatter data of the effective average shear stress undergoes linear fitting; according to a value of fitting straight slope, internal friction angle of the rock mass structural plane is calculated; and according to the point of intersection between the fitting line and vertical coordinate of the rectangular coordinate system, cohesion force of the rock mass structural plane is obtained. By measuring the shear strength index of the structural plane on the basis of the effective shear area, shear strength characteristic of the rock mass structural plane can be truly reflected. The design for geotechnical engineering construction and hidden danger management scheme has more reliable safety and economy.

Description

technical field [0001] The invention relates to the field of rock mass mechanics analysis, in particular to a method for calculating the shear strength index of a rock mass structural plane. Background technique [0002] Natural rock mass contains a large number of structural planes such as joints, fissures, and faults. Their existence destroys the continuity and integrity of the rock mass structure, deteriorates the engineering properties of the rock mass, and reduces the strength of the rock mass. The research results show that the strength and deformation characteristics of rock mass are mainly affected by the mechanical properties of structural surfaces, especially the shear strength, which is often the key factor for the stability of rock mass engineering such as slopes and dam foundations, while the internal friction angle φ and cohesion The force c is two important indicators to characterize the shear strength of the structural plane. The internal friction angle φ in...

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Problems solved by technology

At present, when calculating the shear stress of the structural surface and drawing the shear stress-shear displacement relationship curve, the calculation is based on the assumption that the structural surface fully exerts its shear resistance capacity, that is, the average shear stress of the entire structural surface is calculated. However, the observation after the test The damage pattern of the structural surface is found: when the structural surface slides, the friction traces do not spread all over the structural surface, but are distributed in a local area, and the distribution area increases with the increase of the normal stress of the structural surface, indicating that based on the structural surface The average shear stress calculated by using the shear capacity can not truly reflect the shear working state of the structural surface, which means that the shear strength index obtained by the direct shear test is not accurate by using the traditional processing method. Undoubtedly, Major geotechnical engineering designed based on these inaccurate shear strength indicators will inevitably have great safety hazards

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