Method for determining sleeve size parameter based on surrounding rock borehole radial stiffness damage evaluation

Abstract

The application provides a sleeve size parameter determination method based on surrounding rock borehole radial stiffness damage evaluation, and relates to the field of mechanics and test technology.The method comprises the following steps: according to the mining stress condition of the engineering site roadway surrounding rock, the basic mechanics parameters of the surrounding rock and the actual situation of the anchor rod support, the sleeve material selection and length parameters of the anchoring base body are determined in combination with the indoor test; the thickness parameters of the sleeve are determined on the basis of the engineering site, the anchoring borehole damage is judged, the stiffness damage of the anchoring hole is closely related to the plastic deformation and the rock modulus damage law, therefore, the plastic zone radius of the anchoring borehole is analyzed in combination with the engineering stress and the lithology condition, the modulus damage degree of the surrounding rock around the borehole is evaluated on the basis of the rock elastic modulus damage evolution law test and the theoretical analysis, and then the radial stiffness damage coefficient of the anchoring borehole is given, and finally, the thickness parameters of the anchoring base body sleeve are determined according to the equivalent mechanics of the engineering surrounding rock borehole and the sleeve radial stiffness, so that the scientificity of the sleeve parameter determination is ensured.

Claims

1. A method for determining sleeve size parameters based on radial stiffness damage assessment of surrounding rock boreholes, characterized in that the steps include... include: S1. Calculate the radial stiffness of the borehole without damage to the surrounding rock; S2. Perform borehole deformation plasticity analysis to obtain the relationship between the radius of the plastic zone of the surrounding rock borehole and the mining stress; S3. Calculate the elastic modulus of the undamaged surrounding rock; S4. Calculate the radial stiffness of the borehole in the surrounding rock considering stiffness damage, and the damage variable of the borehole radial stiffness in the damaged surrounding rock. S5. Determine the radial stiffness of the sleeve and calculate the thickness of the sleeve; The intact surrounding rock conforms to the initial Mohr-Coulomb strength criterion, while the surrounding rock in the plastic zone conforms to the residual Mohr-Coulomb strength criterion; damage to the surrounding rock of the anchored borehole is considered as a reduction in the elastic modulus of the surrounding rock. The borehole deformation satisfies the assumptions of plane strain and small deformation. The radial stiffness of the non-damaging surrounding rock borehole k nr The calculation method is as follows: in, E r The elastic modulus of the surrounding rock; μ r The Poisson's ratio of the surrounding rock; a The radius of the surrounding rock anchoring borehole; The radius of the plastic zone of the surrounding rock borehole c With mining stress P a0 The relationship between them is expressed as follows: in, c The radius of the plastic zone of the surrounding rock anchoring borehole; Initial friction angle with the rock ϕ and cohesion C Related functions; Initial friction angle with the rock ϕ and cohesion C Related functions; A function related to the residual friction angle and cohesion within the rock; To the residual friction angle within the rock ϕ' and cohesion C' Related functions; P a0 To anchor the surrounding rock of the borehole to reduce mining stress; The elastic modulus E of the undamaged surrounding rock r ' The calculation method is as follows: in, D E E is the damage variable representing the elastic modulus of the surrounding rock. r ' The elastic modulus of the surrounding rock after damage; The radial stiffness of the surrounding rock borehole considering stiffness damage. k nr ' The calculation method is as follows: in, k nr = , Indicates the radial stiffness of the borehole without damaging the surrounding rock; definition D k The damage variable, representing the radial stiffness of the borehole in relation to the surrounding rock, is calculated as follows: The radial stiffness of the sleeve k mn The calculation method is as follows: in, E m The elastic modulus of the sleeve; μ m The Poisson's ratio of the sleeve; b The outer radius of the sleeve; The thickness of the sleeve t The calculation method is as follows: in, t The wall thickness of the sleeve; D k The damage variable is the radial stiffness of the borehole in the surrounding rock.

2. The method for determining sleeve size parameters based on radial stiffness damage assessment of surrounding rock boreholes according to claim 1, characterized in that, The sleeve can be made of PVC plastic, steel, or aluminum alloy.

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