Stress gradient loading test apparatus and method of accurately determining loading energy

Patent metadata

Field	Value
Publication number	US-11041790-B2
Application number	US-202117156545-A
Country	US
Kind code	B2
Filing date	Jan 23, 2021
Priority date	Nov 27, 2019
Publication date	Jun 22, 2021
Grant date	Jun 22, 2021

Abstract

The present disclosure provides a stress gradient loading test apparatus and a method of accurately determining loading energy, relating to the technical field of a rock mechanical test. The apparatus includes an upper pressure-bearing plate, a specimen fixing device, a stress transfer device, and a simulation specimen. A computer processes stress and strain monitoring data. The stress transfer device includes a plurality of plate-like high strength materials in combination. A simulation roadway is opened in the simulation specimen, and a strain gauge and a stress sensor are disposed on the simulation specimen. In a test using the apparatus, stress gradient loading is realized and elastic strain energy is calculated by the plate-like high strength materials with different stiffnesses of the stress transfer device, and loading energy acting on the simulation specimen is calculated in combination with energy applied by a tester.

First claim

We claim:

1. A stress gradient loading test apparatus comprising a rock mechanical tester, an upper pressure bearing plate, a specimen fixing device, a stress transfer device, and a simulation specimen, in which the specimen fixing device is disposed on a test bench of the rock mechanical tester, wherein the simulation specimen is placed between side baffle plates of the specimen fixing device, the stress transfer device is pressed on an upper surface of the simulation specimen, and the upper pressure bearing plate is pressed above the stress transfer device; the specimen fixing device is in a U shape, including a bottom baffle plate and two side baffle plates; the stress transfer device includes a plurality of plate-like high strength materials which are arranged in combination according to magnitude of stiffness, and the plurality of plate-like high strength materials together transfer a loading pressure of the upper pressure bearing plate; a simulation roadway is opened in the simulation specimen, a plurality of strain gauges are disposed on top and bottom plates and a side wall of the simulation roadway, and a stress sensor is disposed on an upper part of the simulation specimen; a loading system of the rock mechanical tester, the strain gauge, and the stress sensor are connected with a computer separately; the stress transfer device is mounted by fitting the side baffle plates of the fixing device, and a contact surface between the stress transfer device and the side baffle plate is smooth, and an indenter of the rock mechanical tester is pressed on the upper pressure bearing plate; and the upper pressure bearing plate is a solid steel plate with a thickness smaller than a thickness of the side baffle plate of the specimen fixing device.

2. A method of accurately determining loading energy in a stress gradient loading test using the stress gradient loading test apparatus according to claim 1 , comprising the following steps:
step 1. producing a simulation specimen in which a simulation roadway is opened and a strain gauge and a stress sensor are arranged;
step 2. placing a well-cured simulation specimen between the side baffle plates of the specimen fixing device;
step 3. placing the stress transfer device formed of a plurality of well-arranged plate-like high strength materials above the simulation specimen, the plurality of plate-like high strength materials are uniformly pressed on the simulation specimen, and load is applied in strip-shaped regions, in which σ i is a stress of each plate-like high strength material, E i is an elastic modulus of each plate-like high strength material, ε is a strain of the plate-like high strength material, and i is a serial number of the plate-like high strength material which is a positive integer;
step 4. placing the upper pressure bearing plate above the stress transfer device and loading the upper pressure bearing plate by a rock mechanical tester, during the loading process:
σ i /E i =ε is satisfied, and the larger the elastic modulus of the plate-like high strength material, the larger the stress transferred by the material;
step 5. calculating energy applied to the simulation specimen in a separate region, and calculating and displaying elastic strain energy of each plate-like high strength material and loading energy of the rock mechanical tester by a computer; the loading energy is converted into the elastic strain energy and the energy applied to the simulation specimen, in which
the elastic strain energy can be calculated according to a formula

U
=

∫
L

Δ
⁢

⁢
1

⁢

Pd
⁡

(

Δ
⁢

⁢
1

)

,

wherein P is a stress applied by the stress transfer device and monitored by the stress sensor, Δl is a deformation amount of the simulation specimen monitored by the strain gauge; the loading energy is calculated according to a loading force F and a displacement Δx of the indenter; and
step 6. recording an energy change in a process from loading of the rock mechanical tester to failure of the simulation specimen.

Assignees

• Univ Shandong Science & Tech

Inventors

• Guo Weiyao
• Gu Xuebin
• Zhao Tongbin
• Tan Yunliang

Classifications

• G01N3/08 Primary

  by applying steady tensile or compressive forces (G01N3/28 takes precedence) · CPC title

• G01N2203/0067

  Fracture or rupture · CPC title

• G01N2203/0019

  Compressive · CPC title

• G01N2203/0676

  Force, weight, load, energy, speed or acceleration · CPC title

• G01N3/02

  Details · CPC title