U.S. patent application number 17/225983 was filed with the patent office on 2021-07-22 for inner and outer framework combined variable stiffness rock mechanics tester and testing method.
The applicant listed for this patent is SHANDONG UNIVERSITY OF SCIENCE AND TECHNOLOGY. Invention is credited to Yue QIU, Yunliang TAN, Xinyuan WANG, Minglu XING, Yanchun YIN, Tongbin ZHAO, Wuwei ZHENG.
Application Number | 20210223152 17/225983 |
Document ID | / |
Family ID | 1000005693012 |
Filed Date | 2021-07-22 |
United States Patent
Application |
20210223152 |
Kind Code |
A1 |
ZHAO; Tongbin ; et
al. |
July 22, 2021 |
INNER AND OUTER FRAMEWORK COMBINED VARIABLE STIFFNESS ROCK
MECHANICS TESTER AND TESTING METHOD
Abstract
The present disclosure provides an inner and outer framework
combined variable stiffness rock mechanics tester and a testing
method, relating to the technical field of rock mechanics. The
tester includes a stiffness adjusting apparatus, a test loading
apparatus, a monitoring system, and a control system. During a
test, according to monitoring data, the load of the stiffness
adjusting cylinder is controlled through the control system, and
the displacement of the inner top beam is adjusted in real time, to
ensure that the loading stiffness reaches a design value and
remains constant, which solves the technical problem that the
loading stiffness of the rock mechanics tester cannot be
quantitatively adjusted, and is easy to operate.
Inventors: |
ZHAO; Tongbin; (Qingdao,
CN) ; YIN; Yanchun; (Qingdao, CN) ; TAN;
Yunliang; (Qingdao, CN) ; XING; Minglu;
(Qingdao, CN) ; QIU; Yue; (Qingdao, CN) ;
ZHENG; Wuwei; (Qingdao, CN) ; WANG; Xinyuan;
(Qingdao, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHANDONG UNIVERSITY OF SCIENCE AND TECHNOLOGY |
Qingdao |
|
CN |
|
|
Family ID: |
1000005693012 |
Appl. No.: |
17/225983 |
Filed: |
April 8, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/CN2019/104835 |
Sep 9, 2019 |
|
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17225983 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 2203/0069 20130101;
G01N 3/12 20130101; G01N 2203/0019 20130101; G01N 33/24
20130101 |
International
Class: |
G01N 3/12 20060101
G01N003/12; G01N 33/24 20060101 G01N033/24 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2019 |
CN |
201910291663.6 |
Claims
1. An inner and outer framework combined variable stiffness rock
mechanics tester, comprising a stiffness adjusting apparatus, a
test loading apparatus, a monitoring system, and a control system,
the stiffness adjusting apparatus comprising an outer framework top
beam, an outer column, a stiffness adjusting cylinder, and a base,
the outer column being fixedly connected between the outer
framework top beam and the base, and the stiffness adjusting
cylinder being fixed to the outer framework top beam; the test
loading apparatus comprising an inner top beam, an inner column, a
loading cylinder, a pressure bearing column, and a high-pressure
spring, the inner top beam being fixedly connected below the
stiffness adjusting cylinder, the inner column being connected
between the inner top beam and the base, the loading cylinder being
fixed to the base, and the pressure bearing column being fixed
below the inner top beam; the high-pressure spring sleeving an
upper end of the inner column, and the upper end of the inner
column and the high-pressure spring being embedded in the inner top
beam together and telescopic along a mating hole on the inner top
beam; the monitoring system comprising a first pressure sensor and
a second pressure sensor, the first pressure sensor being disposed
between the stiffness adjusting cylinder and the inner top beam,
and the second pressure sensor being disposed between the inner top
beam and the pressure bearing column; the monitoring system further
comprising a displacement sensor, a vertical guide rod, and a
horizontal guide rod, the vertical guide rod being fixed to the
base; one end of the horizontal guide rod sliding along the
vertical guide rod, and the other end being connected to the inner
top beam; and a short bracket being fixedly disposed on the
vertical guide rod below the horizontal guide rod, and the short
bracket being provided with the displacement sensor.
2. The inner and outer framework combined variable stiffness rock
mechanics tester according to claim 1, wherein stiffness of the
inner top beam is greater than that of the inner column.
3. The inner and outer framework combined variable stiffness rock
mechanics tester according to claim 2, wherein 4 outer columns are
provided, stiffness of the outer column being greater than that of
the inner column; 4 inner columns are provided, and a cross section
of the upper end of the inner column is T-shaped.
4. The inner and outer framework combined variable stiffness rock
mechanics tester according to claim 1, wherein the control system
controls the stiffness adjusting cylinder and the loading cylinder
to load, and the control system receives and records monitoring
data of the monitoring system in real time.
5. A method for adjusting loading stiffness of an inner and outer
framework combined rock mechanics tester, using the inner and outer
framework combined variable stiffness rock mechanics tester
according to claim 1, wherein the method comprises the following
steps: step 1: setting a loading stiffness value, and determining a
function relationship between a load value of a rock specimen and
designed displacement of the inner top beam; step 2: transmitting,
by the second pressure sensor, the load value of the rock specimen
to the control system in real time, transmitting, by the
displacement sensor, an actual displacement value of the inner top
beam to the control system in real time, and comparing, by the
control system, the actual displacement with the designed
displacement; step 3: when the actual displacement is greater than
the designed displacement, controlling, by the control system, the
stiffness adjusting cylinder to load to increase the load; when the
actual displacement is less than the designed displacement,
controlling, by the control system, the stiffness adjusting
cylinder to unload to reduce the load; and repeating this step
until the actual displacement value is equal to the designed
displacement value; and step 4: repeating, by the control system,
the operation of step 3 to ensure that a relationship between the
load value of the rock specimen and the actual displacement value
during a test satisfies the function relationship between the load
value of the rock specimen and the designed displacement of the
inner top beam.
6. An inner and outer framework combined variable stiffness rock
mechanics testing method, using the inner and outer framework
combined variable stiffness rock mechanics tester according to
claim 1, wherein the method comprises the following steps: step A)
setting a stiffness value of the tester; step B) placing a rock
specimen, and transmitting, by the monitoring system, monitoring
data of the first pressure sensor, the second pressure sensor, and
the displacement sensor to the control system; step C) adjusting,
by the control system, loading stiffness in real time according to
a feedback from the monitoring system, to make a load value of the
rock specimen and an actual displacement value of the inner top
beam satisfy a function relationship between the load value of the
rock specimen and designed displacement of the inner top beam; and
step D) continuously loading the rock specimen through the loading
cylinder till instable failure of the rock specimen.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/CN2019/104835 with a filling date of Sep. 9,
2019, designating the United states, now pending, and further
claims to the benefit of priority from Chinese Application No.
201910291663.6 with a filing date of Apr. 12, 2019. The content of
the aforementioned applications, including any intervening
amendments thereto, are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to the technical field of
rock mechanics, in particular to an inner and outer framework
combined variable stiffness rock mechanics tester, a method for
adjusting loading stiffness of the tester, and a method for rock
mechanics testing using the tester.
BACKGROUND
[0003] Rock mechanics testing is a main technical means to obtain
formation character parameters in underground engineering such as
geotechnical engineering, mining, and tunnel construction. In 1970,
Saramon first comprehensively discussed the influence of different
stiffness of a tester on deformation characteristics of rock, and
proposed to use a tester with higher stiffness to reduce the
additional energy acting on the rock, so as to obtain a
stress-strain curve after the peak stress. This point of view was
later confirmed by researchers and engineers engaged in rock
mechanics in rock mechanics testing, so as to obtain a full
stress-strain curve of the rock. The method can also be used to
analyze a post-peak instability failure process. By analyzing the
full stress-strain curve of the rock, mechanical parameters such as
deformation modulus, peak strength, residual strength, and impact
energy of the rock can be calculated, which provides a basis for
the design of rock engineering excavation schemes and stability
analysis.
[0004] In actual engineering formation, a lithological structure is
diverse, and the combination of rock formations often changes. It
can be seen that the stiffness of the rock formations is an
indeterminate constant. Laboratory tests show that for the same
kind of rock, when testers with different stiffness are used for
loading, deformation and failure characteristics of the rock show
obvious differences, especially the post-peak deformation and
failure behaviors. According to the above research, in order to
more accurately study real mechanical response characteristics of
rock in an underground engineering environment, a rock mechanics
tester matching the roof stiffness needs to be selected for rock
mechanical property testing of roof with different lithologies.
Therefore, it is necessary to provide a rock mechanics tester whose
loading stiffness can be quantitatively adjusted and controlled.
However, the loading stiffness of an existing rock mechanics tester
is generally constant. In order to solve the problem, it is
necessary to further improve the existing rock mechanics tester, so
that the loading stiffness is adjustable and mechanics-related
parameters in line with rock engineering characteristics can be
tested.
SUMMARY OF THE INVENTION
[0005] In order to solve the technical problem that the loading
stiffness cannot be quantitatively adjusted in rock mechanics
testing, the present disclosure provides an inner and outer
framework combined variable stiffness rock mechanics tester and a
testing method. Specific technical solutions are as follows:
[0006] An inner and outer framework combined variable stiffness
rock mechanics tester includes a stiffness adjusting apparatus, a
test loading apparatus, a monitoring system, and a control system,
the stiffness adjusting apparatus comprising an outer framework top
beam, an outer column, a stiffness adjusting cylinder, and a base,
the outer column being fixedly connected between the outer
framework top beam and the base, and the stiffness adjusting
cylinder being fixed to the outer framework top beam; the test
loading apparatus comprising an inner top beam, an inner column, a
loading cylinder, a pressure bearing column, and a high-pressure
spring, the inner top beam being fixedly connected below the
stiffness adjusting cylinder, the inner column being connected
between the inner top beam and the base, the loading cylinder being
fixed to the base, and the pressure bearing column being fixed
below the inner top beam.
[0007] Preferably, stiffness of the inner top beam is greater than
that of the inner column, an upper end of the inner column passes
through the inner top beam, and the high-pressure spring sleeves
the upper end of the inner column. Under a load, the inner column
of the tester may produce greater tensile deformation. The
high-pressure spring is made of a flexible material, and the
deformation under an external load is greater than that of a
low-stiffness inner column. Superposition of the deformation of the
high-pressure spring and the deformation of the low-stiffness inner
column further increases an upper limit of elastic deformation and
the amount of elastic energy storage of an inner test loading
apparatus, thereby further reducing a lower limit of the loading
stiffness of the tester.
[0008] Preferably, the outer columns are provided with 4, stiffness
of the outer column being greater than that of the inner column;
the inner column are provided with 4, and a cross section of the
upper end of the inner column is T-shaped.
[0009] Preferably, the monitoring system comprising a first
pressure sensor and a second pressure sensor, the first pressure
sensor being disposed between the stiffness adjusting cylinder and
the inner top beam, and the second pressure sensor being disposed
between the inner top beam and the pressure bearing column.
[0010] Preferably, the monitoring system further comprising a
displacement sensor, a vertical guide rod, and a horizontal guide
rod, the vertical guide rod being fixed to the base; one end of the
horizontal guide rod sliding along the vertical guide rod, and the
other end being connected to the inner top beam; a short bracket
being fixedly disposed on the vertical guide rod below the
horizontal guide rod, and the short bracket being provided with the
displacement sensor.
[0011] Preferably, the control system controls the stiffness
adjusting cylinder and the loading cylinder to load, and the
control system receives and records monitoring data of the
monitoring system in real time.
[0012] A method for adjusting loading stiffness of an inner and
outer framework combined rock mechanics tester, using the inner and
outer framework combined variable stiffness rock mechanics tester
described above, includes the following steps:
[0013] Step 1: setting a loading stiffness value, and determining a
function relationship between a load value of a rock specimen and
designed displacement of the inner top beam;
[0014] Step 2: transmitting, by the second pressure sensor, the
load value of the rock specimen to the control system in real time,
transmitting, by the displacement sensor, an actual displacement
value of the inner top beam to the control system in real time, and
comparing, by the control system, the actual displacement with the
designed displacement;
[0015] Step 3: when the actual displacement is greater than the
designed displacement, controlling, by the control system, the
stiffness adjusting cylinder to load to increase the load; when the
actual displacement is less than the designed displacement,
controlling, by the control system, the stiffness adjusting
cylinder to unload to reduce the load; and repeating this step
until the actual displacement value is equal to the designed
displacement value; and
[0016] Step 4: repeating, by the control system, the operation of
step 3 to ensure that a relationship between the load value of the
rock specimen and the actual displacement value during a test
satisfies the function relationship between the load value of the
rock specimen and the designed displacement of the inner top
beam.
[0017] An inner and outer framework combined variable stiffness
rock mechanics testing method, using the above-mentioned inner and
outer framework combined variable stiffness rock mechanics tester,
which includes the following steps:
[0018] Step A. setting a stiffness value of the tester;
[0019] Step B. placing a rock specimen, and transmitting, by the
monitoring system, monitoring data of the first pressure sensor,
the second pressure sensor, and the displacement sensor to the
control system;
[0020] Step C. adjusting, by the control system, loading stiffness
in real time according to a feedback from the monitoring system, to
make a load value of the rock specimen and an actual displacement
value of the inner top beam satisfy a function relationship between
the load value of the rock specimen and designed displacement of
the inner top beam; and
[0021] Step D. continuously loading the rock specimen through the
loading cylinder till instable failure of the rock specimen.
[0022] The present disclosure has the following advantageous
effects:
[0023] (1) The inner and outer framework combined variable
stiffness rock mechanics tester provided in the present disclosure
realizes loading stiffness adjustment of the rock mechanics tester
by the loading of the stiffness adjusting cylinder and the loading
cylinder and the deformation of the high-pressure spring and the
inner column; and the loading stiffness can be adjusted in real
time according to the displacement of the inner top beam and
loading stress fed back by the monitoring system, so as to ensure
that the stiffness of the tester remains unchanged during the
loading.
[0024] (2) The first pressure sensor is disposed between the
stiffness adjusting cylinder and the inner top beam to monitor and
acquire the magnitude of a load applied by the stiffness adjusting
cylinder to the inner top beam in real time. The second pressure
sensor is disposed between the inner top beam and the pressure
bearing column, for monitoring an actual load value of the rock
specimen. The displacement sensor is used for monitoring the
magnitude of the displacement of the inner top beam in real
time.
[0025] (3) The method for adjusting loading stiffness of the tester
is based on joint action of two cylinders. Firstly, the loading
cylinder loads a rock specimen, the rigid inner top beam may move
upward under a load, drive the inner column with less stiffness to
undergo tensile deformation at the same time, and drive the
high-pressure spring to undergo compression deformation at the same
time, and elastic energy is stored. Then, the stiffness adjusting
cylinder is used to apply a load to limit the displacement of the
inner top beam, the tensile deformation of the inner column and the
compression deformation of the high-pressure spring. The load
applied by the stiffness adjusting cylinder is adjusted by using a
monitoring feedback value of the monitoring system, so as to
control the displacement of the rigid inner top beam, achieving the
purpose of automatic adjustment and control of the loading
stiffness of the tester.
[0026] (4) The method for rock mechanics testing using the tester
can more accurately study real mechanical response characteristics
of rock in underground engineering environments.
[0027] In addition, the tester also has the advantages of strong
reformability, simple operation, and flexible adjustment.
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1 is a schematic structural diagram of an inner and
outer framework combined variable stiffness rock mechanics
tester.
[0029] FIG. 2 is a schematic structural diagram of an A-A cross
section in FIG. 1.
[0030] FIG. 3 is a schematic structural diagram of a B-B cross
section in FIG. 1.
[0031] FIG. 4 is a flowchart of a method for adjusting loading
stiffness.
[0032] FIG. 5 is a diagram of a function relationship between a
load value of a rock specimen and displacement of an inner top
beam.
[0033] Reference numerals in the drawings are as follows: 1. outer
framework top beam; 2. outer column; 3 stiffness adjusting
cylinder; 4. base; 5. inner top beam; 6. inner column; 7. loading
cylinder; 8. pressure bearing column; 9. high-pressure spring; 10.
first pressure sensor; 11. second pressure sensor; 12. displacement
sensor; 13. vertical guide rod; 14. horizontal guide rod; 15.
control system; 16. mating hole; 17. short bracket.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0034] As shown in FIGS. 1 to 5, an inner and outer framework
combined variable stiffness rock mechanics tester and a testing
method provided in the present disclosure include the following
specific implementations.
[0035] An inner and outer framework combined variable stiffness
rock mechanics tester specifically includes a stiffness adjusting
apparatus, a test loading apparatus, a monitoring system, and a
control system. The stiffness adjusting apparatus and the test
loading apparatus cooperate with each other to adjust the stiffness
of the tester. The monitoring system monitors the displacement of
an inner top beam and the magnitude of a load applied by a cylinder
in real time. The control system controls the operation of the
stiffness adjusting cylinder and a loading cylinder to realize
automatic adjustment of the loading stiffness of the tester. In
addition, the tester also has the advantages of strong
reformability, simple operation, and flexible adjustment.
[0036] The stiffness adjusting apparatus includes an outer
framework top beam 1, an outer column 2, a stiffness adjusting
cylinder 3, and a base 4. The outer framework top beam 1 and the
outer column 2 are made of high-stiffness materials, and the
stiffness of the materials used is greater than 10 N/m, so as to
ensure the overall stability of the tester. The outer column 2 is
disposed between the outer framework top beam 1 and the base 4. 4
outer columns 2 are provided. Stiffness of the outer column 2 is
greater than that of the inner column 6. An overall top view of the
outer column 2 of the stiffness adjusting apparatus and the inner
column 6 of the test loading apparatus is arranged in a square
shape. The stiffness adjusting cylinder is disposed on the outer
framework top beam 1. Specifically, the stiffness adjusting
cylinder 3 is disposed at a central position of the outer framework
top beam 1. The stiffness adjusting cylinder 3 is placed upside
down to load downward, thereby limiting the displacement of the
inner top beam of the test loading apparatus.
[0037] The test loading apparatus specifically includes an inner
top beam 5, an inner column 6, a loading cylinder 7, a pressure
bearing column 8, and a high-pressure spring 9. The inner top beam
5 is disposed below the stiffness adjusting cylinder 3. The inner
column 6 is disposed between the inner top beam 5 and the base 4.
The loading cylinder 7 is disposed on the base 4. The loading
cylinder 7 loads vertically upward. The pressure bearing column 8
is disposed below the inner top beam 5, for transmitting the
loading force and fixing the rock specimen. Stiffness of the inner
top beam 5 is greater than that of the inner column. The inner top
beam 5 is made of a material with higher stiffness, and the
deformation of the inner top beam 5 within the loading range of the
stiffness adjusting cylinder 3 is negligible. An upper end of the
inner column 6 passes through the inner top beam 5. The
high-pressure spring 9 sleeves the upper end of the inner column 6,
for adjusting and controlling the displacement of the inner top
beam 5. In addition, specifically, 4 inner columns 6 are also
provided. The upper end of the inner column 6 and the high-pressure
spring are embedded in the inner top beam 5 together and telescopic
along a mating hole 16 on the inner top beam 5. A cross section of
the upper end of the inner column 6 is T-shaped.
[0038] When the tester is in use, if the test loading apparatus is
removed, the inner and outer framework combined variable stiffness
rock mechanics tester as a whole can be used as a rock mechanics
tester with fixed stiffness, and an existing rock mechanics testing
machines with fixed stiffness can also be modified.
[0039] The monitoring system includes a first pressure sensor 10
and a second pressure sensor 11. The first pressure sensor 10 is
disposed between the stiffness adjusting cylinder 3 and the inner
top beam 5, for monitoring and acquiring the magnitude of a load
applied by the stiffness adjusting cylinder 3 to the inner top beam
5 in real time. The second pressure sensor 11 is disposed between
the inner top beam 5 and the pressure bearing column 8, for
monitoring an actual load value of the rock specimen. The
monitoring system further includes a displacement sensor 12, a
vertical guide rod 13, and a horizontal guide rod 14. The vertical
guide rod 13 is fixed to the outer framework top beam 1 and the
base 4. One end of the horizontal guide rod 14 slides along the
vertical guide rod 13, and the other end is connected to the inner
top beam 5 and moves with the inner top beam 5. The vertical guide
rod 13 below the horizontal guide rod 14 is further fixedly
provided with a short bracket 17. The short bracket 17 is provided
with the displacement sensor 12. The displacement sensor 12 is used
for monitoring the magnitude of the displacement of the inner top
beam 5 in real time.
[0040] The control system 15 controls the stiffness adjusting
cylinder 3 and the loading cylinder 7 to load, the control system
15 receives and records monitoring data of the monitoring system,
and the control system adjusts the stiffness adjusting cylinder to
load or unload in real time according to a feedback from the
monitoring system, so as to ensure that the monitoring data
satisfies a function relationship between a load value of the rock
specimen and designed displacement of the inner top beam during the
test.
[0041] Through the research on laboratory tests of rock mechanics,
it is found that for the same kind of rock, when testers with
different stiffness are used for loading, deformation and failure
characteristics of the rock show obvious differences, especially
the post-peak deformation and failure behaviors. It can be seen
from the above research that in order to more accurately study the
real mechanical response characteristics of the rock in the
underground engineering environment, the stiffness of the tester
needs to be adjusted during the test to avoid a test error caused
by the different loading stiffness.
[0042] The present disclosure provides a method for adjusting
loading stiffness of an inner and outer framework combined rock
mechanics tester, using the inner and outer framework combined
variable stiffness rock mechanics tester described above. As shown
in FIG. 4, the adjusting step specifically includes the following
steps:
[0043] Step 1: A loading stiffness value is set, and a function
relationship between a load value of a rock specimen and designed
displacement of the inner top beam is determined, as shown by the
straight line in FIG. 5.
[0044] Step 2: The second pressure sensor transmits the load value
of the rock specimen to the control system in real time, the
displacement sensor transmits an actual displacement value of the
inner top beam to the control system, and the control system
compares the actual displacement with the designed
displacement.
[0045] Step 3: When the actual displacement is greater than the
designed displacement, the control system controls the stiffness
adjusting cylinder to load to increase the load, so as to reduce
the actual displacement; when the actual displacement is less than
the designed displacement, the control system controls the
stiffness adjusting cylinder to unload to reduce the load, so as to
increase the actual displacement; and this step is repeated until
the actual displacement value is equal to the designed displacement
value.
[0046] Step 4: The control system repeats the operation of step 3
to ensure that a relationship between the load value of the rock
specimen and the actual displacement value during a test satisfies
the function relationship between the load value of the rock
specimen and the designed displacement of the inner top beam. An
actual relation curve during the test is as shown by the curve in
FIG. 5.
[0047] An adjustment principle of the method is based on joint
action of two cylinders. Firstly, the loading cylinder loads a rock
specimen, the rigid inner top beam may move upward under a load,
drive the inner column with less stiffness to undergo tensile
deformation at the same time, and drive the high-pressure spring to
undergo compression deformation at the same time, and elastic
energy is stored. Then, the stiffness adjusting cylinder is used to
apply a load to limit the displacement of the inner top beam, the
tensile deformation of the inner column and the compression
deformation of the high-pressure spring. When the rock specimen is
subjected to the same load value, the greater the load applied by
the stiffness adjusting cylinder, the smaller the displacement of
the rigid inner top beam, the smaller the energy stored in the
inner column with low stiffness, the smaller the impact load when
the specimen is destroyed, the greater the loading stiffness of the
tester. In the above process, the displacement sensor monitors a
displacement value in real time, and the control system adjusts the
load applied by the stiffness adjusting cylinder, so as to realize
real-time control over the displacement of the inner top beam,
which ensures that the loading stiffness reaches a design value and
remains constant during test loading and achieves the purpose of
automatic adjustment and control of the loading stiffness of the
tester.
[0048] More specifically, before the test, a loading stiffness
value is set according to a specific structure of the tester, to
obtain a function relationship between a load value Fr(t) of the
rock specimen and a designed displacement value Dr(t) of the inner
top beam. During the test, the second pressure sensor of the
monitoring system monitors the load value Fr(t) of the rock
specimen in real time, the control system determines the designed
displacement value Dr(t) of the inner top beam correspond to a
certain time, and the displacement sensor measures an actual
displacement value Da(t) of the inner top beam at the time. The
control system compares the designed displacement value Dr(t) with
the actual displacement value Da(t). When the actual displacement
value Da(t) of the inner top beam is greater than the designed
displacement value Dr(t), the control system controls the stiffness
adjusting cylinder to load to increase a load value Fa(t) of the
stiffness adjusting cylinder, so as to limit the displacement of
the inner top beam, till the actual displacement Da(t) is equal to
the allowable displacement value Dr(t). When the actual
displacement value Da(t) is less than the designed displacement
value Dr(t), the control system controls the stiffness adjusting
cylinder to unload to reduce the load value Fa(t) of the stiffness
adjusting cylinder, so as to increase the actual displacement value
Da(t) to make the actual displacement value Da(t) equal to the
allowable displacement value Dr(t). The control system makes the
actual displacement value Da(t) of the inner top beam 5 equal to
the designed displacement value Dr(t) through constant feedback and
adjustment of the displacement information and load information
described above, so that the load value Fr(t) of the rock specimen
and the actual displacement value Da(t) of the inner top beam
satisfy a corresponding function relationship in real time. This
ensures that the loading stiffness is a set value and remains
constant. During the continuous loading of the loading cylinder,
the loading stiffness is maintained constant through adjustment,
and the test is ended till failure and instability of the rock
specimen.
[0049] In addition, the present disclosure further provides an
inner and outer framework combined variable stiffness rock
mechanics testing method, using the inner and outer framework
combined variable stiffness rock mechanics tester and the method
for adjusting loading stiffness, specifically including the
following steps:
[0050] Step A) A specific loading stiffness value of the tester is
set according to a test scheme or a loading stiffness value of the
tester is set according to a test requirement.
[0051] Step B) A rock specimen is placed, the monitoring system
transmits monitoring data of the first pressure sensor, the second
pressure sensor, and the displacement sensor to the control system,
and the control system adjusts the loading of the stiffness
adjusting cylinder according to a control principle, so as to
adjust the loading stiffness to the set value.
[0052] Step C) The control system adjusts the loading stiffness
according to a feedback from the monitoring system, to make a load
value of the rock specimen and an actual displacement value of the
inner top beam satisfy a function relationship between the load
value of the rock specimen and designed displacement of the inner
top beam.
[0053] Step D) The rock specimen is continuously loaded through the
loading cylinder till instable failure of the rock specimen.
[0054] The method for rock mechanics testing using the tester
further reduces an error between a laboratory test and actual
engineering by controlling the loading stiffness during the test,
and thus can better study real mechanical response characteristics
of rock in underground engineering environments.
[0055] It should be appreciated that the foregoing is only
preferred embodiments of the invention and is not for use in
limiting the invention. Although this invention is described in
detail based on the foregoing preferred embodiments, it is apparent
for those skilled in the art that modification of technical
proposals or equivalent substitution of part or all of the
technical features can be made. Any modification, equivalent
substitution, and improvement without departing from the spirit and
principle of this invention should be covered in the protection
scope of the invention.
* * * * *