Method for obtaining rock mechanical-geometric parameters and holographic scanning system

A method for obtaining rock mechanical and geometric parameters of rock samples, the steps being as follows:

• S1, acquiring an image of an upper surface of a rock sample by one of two cameras symmetrically and obliquely arranged above the rock sample;
• S2, dividing the upper surface of the rock sample into N1×N1 grids with high resolution by laser, and then using a Berkovich indenter for indentation test in each grid according to a preset loading rate w1 and an indentation depth L1, so as to obtain a dynamic signal of displacement changing with time D1(t) by a displacement measurement system during each indentation process, and a dynamic signal of load changing with time F1(t) by a pressure sensor which is sitting at a bottom of the rock sample, and then obtaining a three-dimensional mechanical parameter lattice of a corresponding rock sample including an elastic modulus E and a Poisson's ratio μ1 by processing obtained parameters;
• and/or, dividing the upper surface of the same rock sample into N2×N2 grids with low resolution by laser, and then using a twist drill for rotary cutting penetration test in each grid according to a preset drilling rate w2 and a drilling depth L2, so as to obtain a dynamic signal of feed force P(t) changing with time by a feed force sensor connected with the twist drill during each cutting process, a dynamic signal of torque M(t) changing with time by a torque sensor set at an adjacent side of the twist drill during each cutting process, and a dynamic signal of displacement D2(t) changing with time by a displacement measurement system during each cutting process, and then obtaining three-dimensional mechanical parameters including an elastic modulus E, a cohesive force C and an internal friction angle φ and a compressive strength Rp;
• S3, acquiring a pulse echo signal of the rock sample by an ultrasonic sensor excitation device and an ultrasonic sensor receiving device which are symmetrically arranged on both sides of the rock sample, so as to obtain a longitudinal wave velocity Vp and a transverse wave velocity Vs of an ultrasonic wave passing through the rock sample and a density ρ of the rock sample, and then calculating a dynamic elastic modulus Ed and a dynamic Poisson's ratio μd of the rock sample;
• E
• d
• =
• ρ
• ⁢
• V
• s
• 2
• (
• 3
• ⁢
• V
• p
• 2
• -
• 4
• ⁢
• V
• s
• 2
• )
• V
• p
• 2
• -
• V
• s
• 2
• ,
• μ
• d
• =
• V
• p
• 2
• -
• 2
• ⁢
• V
• s
• 2
• 2
• ⁢
• (
• V
• p
• 2
• -
• V
• s
• 2
• )
• ;
• S4, moving the rock sample to a position identical to step S1 again, and then projecting a structured light coding pattern on the upper surface of the rock sample, so as to collect images of the upper surface of the rock sample by the two cameras which are symmetrically and obliquely arranged above the rock sample, and reconstruct a three-dimensional morphology of the upper surface of the rock sample further;
• S5, polishing the upper surface of the rock sample, and lubricating and cooling by running water until the upper surface of the rock sample returning to a smooth plane;
• S6, repeating steps S1˜S5 to grind the rock sample layer by layer and carrying out identical parameter acquisition experiment until the rock sample reaches a last layer of a preset depth, so as to acquire a geometry of a complete rock sample and a 3D parameter lattice of mechanical parameters from an accumulation of parameters of several layers of single-layer rock;
• S7, using an IDW spatial interpolation algorithm to process the 3D lattice of mechanical parameters obtained from step S6:
• R
• ⁡
• (
• x
• )
• =
• ∑
• i
• =
• 0
• n
• ω
• i
• (
• x
• )
• ⁢
• u
• i
• S
• ,
• wherein,
• ω
• i
• (
• x
• )
• =
• 1
• ln
• ⁢
• (
• d
• ⁡
• (
• x
• ,
• x
• i
• )
• )
• ;
• S
• =
• ∑
• j
• =
• 0
• N
• ω
• j
• (
• x
• )
• ;
• xi is an ith sample point;
• x is an unsolved point;
• ωi(x) is a weight of xi;
• ui is an actual value of the ith sample point;
• R(x) is mechanical parameters of rock obtained from different mechanical tests (indentation test, rotary cutting penetration test);
• d(x,xi) is a distance between the sample point and the unsolved point:
• d(x,xi)=√{square root over ((x−xi)2+(y−yi)2+(z−zi)2)},
• wherein, xi, yi, zi are coordinates of the ith sample point on X, Y, and Z axes, respectively;
• obtaining a virtual lattice of mechanical parameters by weighted averages using distances between interpolation points and the sample points as weight, and then obtaining three-dimensional mechanical parameter fields of the complete rock sample, including a compressive strength field, a cohesive force field, an internal friction angle field, an elastic modulus field and a Poisson's ratio field.