Method for evaluating rock energy release effect

Abstract

The application discloses a kind of rock energy release effect evaluation method, comprising: taking multiple rock samples in the region to be measured;Take one of them to obtain its internal fracture degree, obtain the fracture development characteristic value P1 before drop hammer test;Setting counterweight and contact speed carries out drop hammer test and is observed with high-speed camera;Obtain the fracture development characteristic value P2 of sample after drop hammer test, according to P2 and P1 obtains fracture development characteristic value variation ΔP;Replace sample and repeat the above steps, adjust counterweight, contact speed each time drop hammer test, and the relationship between release amount and release speed and ΔP is fitted;Uniaxial compression test is carried out on complete rock sample to calculate its energy release amount and release speed, according to energy release amount, release speed combines curved surface diagram to obtain fracture development characteristic value variation ΔP, and energy release effect is evaluated.The application fully considers the speed of energy release, so as to more accurately reflect the impact tendency of surrounding rock.

Description

Technical Field

[0001] This invention belongs to the technical field of water conservancy and hydropower engineering, and specifically relates to a method for evaluating the energy release effect of rocks. Background Technology

[0002] Rockburst is a dynamic instability phenomenon caused by excavation unloading under high ground stress conditions. Excavation disturbance transforms the stress state of the tunnel wall rock from three-dimensional to two-dimensional or one-dimensional, providing a free surface for rock ejection failure and leading to the propagation of internal cracks and weakening of rock strength. As one of the global challenges in underground engineering, rockburst has increasingly attracted the attention of domestic engineering geology and tunnel engineering communities. Its consequences range from affecting construction progress to endangering equipment safety and even posing a threat to personnel safety. In-depth research on rockburst phenomena can provide targeted information for the prevention and control of related tunnel disasters and has significant guiding significance for safe construction and design in my country's railway, mining, and water conservancy and hydropower projects.

[0003] From an energy perspective, rockburst is the result of the release of elastic strain energy stored within a rock mass, manifesting externally as the destruction of the surrounding rock. During deep rock excavation, the release of strain energy in brittle hard rock is widespread. In my country's existing hydropower projects, most rockbursts induced by deep rock excavation are strain-type rockbursts, primarily manifesting as localized deformation or small-amplitude rock fragment ejection. The cause of these rockbursts is mostly due to changes in the stress state of the surrounding rock caused by blasting excavation, leading to a decrease in the rock mass's energy storage limit and the accumulation and dissipation of energy. When the energy within the rock mass exceeds its storage limit, it causes rock mass failure, releasing the stored strain energy. The energy released from this failure leads to the destruction of nearby rock masses. Simultaneously, the failure and energy release of the rock mass generate stress waves. The energy carried by these stress waves becomes a source of energy for further rock masses in a state of equilibrium, disrupting their equilibrium and causing instability and destruction. Current research on the energy release patterns during rockbursts is insufficient, but there is still a consensus that energy release is a fundamental characteristic of rockbursts, and that the more energy released by the rock mass, the greater the tendency for rockbursts to occur.

[0004] Due to the complexity of the energy release process, existing energy release indicators often only consider the amount of energy released, failing to consider other indicators of energy release. However, from an engineering perspective, this is unreasonable. Therefore, it is necessary to develop indicators that consider other energy release indicators, such as release rate, to supplement and improve existing indicators that only consider the amount of energy released. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for evaluating the energy release effect of rocks. This method fully considers factors such as the rate of energy release, thereby enabling a more accurate reflection of the impact tendency of the surrounding rock.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for evaluating the energy release effect of rocks includes the following steps:

[0008] Step 1: Take multiple rock samples from the area to be tested;

[0009] Step 2: Take one of the samples and obtain its internal crack degree. Take the average crack degree at multiple cross-sectional locations of the sample as the crack development characteristic value P1 of the sample.

[0010] Step 3: Set the counterweight m and contact velocity v to conduct a drop hammer test and observe with a high-speed camera. Calculate the release amount ΔE and release velocity Ev of the sample based on the counterweight m, contact velocity v and high-speed camera observation data.

[0011] Step 4: Obtain the internal porosity of the sample again, and obtain the crack development characteristic value P2 of the sample after the drop hammer test according to the method in Step 2. Obtain the change in crack development characteristic value ΔP based on crack development characteristic value P2 and crack development characteristic value P1 in Step 2.

[0012] Step 5: Based on steps 3 and 4, obtain the relationship between the sample release amount ΔE and release rate Ev and the change in fracture development characteristic value ΔP.

[0013] Step 6: Replace the sample and repeat steps 2-5. Adjust the counterweight and contact speed during each drop hammer test to obtain a series of relationship points between the release amount ΔE, the release rate Ev and the change in the characteristic value of fracture development ΔP. Fit the relationship points to obtain the relationship between the three.

[0014] Step 7: Conduct a uniaxial compression test on the intact rock sample to obtain the full stress-strain curve. Combined with the loading rate, calculate the energy release amount and release rate. Based on the energy release amount and release rate and the correlation in Step 6, obtain the change in fracture development characteristic value ΔP, and evaluate the energy release effect based on the change in fracture development characteristic value ΔP.

[0015] Furthermore, the initial properties of the multiple rock samples taken from the area to be tested in step 1 are similar.

[0016] Furthermore, in step 3, a high-speed camera is used to observe and obtain the time difference Δt from the moment the falling hammer contacts the sample until its downward velocity reaches zero, as well as the maximum height h of the reverse motion after the falling hammer velocity reaches zero.

[0017] Furthermore, in step 3, the energy release ΔE is obtained from the contact velocity v, the mass m of the falling hammer, and the reverse motion height h, specifically as follows:

[0018] ΔE=mv 2 -mgh.

[0019] Furthermore, the release rate Ev is obtained from the time difference Δt and the release amount ΔE, specifically as follows:

[0020] Ev = ΔE / Δt.

[0021] Furthermore, in step 6, the counterweight adjustment range is from making the sample essentially undamaged to completely destroying the sample.

[0022] Furthermore, geotechnical CT visualization tests were used to obtain the internal porosity of the samples.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: Based on the prior art, the present invention fully considers the energy release rate, thereby enabling the understanding of the differences in release effects under the same energy release conditions, and can more accurately reflect the impact tendency of the surrounding rock, providing a basis for formulating corresponding measures for rockburst engineering, and also supplementing and improving the existing indicators that only consider the energy release amount. Attached Figure Description

[0024] Figure 1 This is a flowchart of a method for evaluating the energy release effect of rocks according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the internal porosity of the sample in an embodiment of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0028] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0029] like Figure 1 As shown in the figure, an embodiment of the present invention discloses a method for evaluating the energy release effect of rocks, including the following steps:

[0030] Step 1: Take multiple rock samples from the area to be tested;

[0031] Step 2: Take one of the samples and obtain its internal porosity. Specifically, perform a geotechnical CT visualization test on the sample to obtain the internal porosity of the rock sample, as shown below. Figure 2 As shown, the average value of the fissure degree at the upper, middle and lower cross-sections is taken as the fissure development characteristic value P1;

[0032] Step 3: Set the counterweight m and contact velocity v to conduct a drop hammer test, and observe the test with a high-speed camera to obtain the time difference Δt between the drop hammer contacting the sample and the point where the downward velocity reaches 0, as well as the maximum height h of the reverse motion after the drop hammer reaches 0. Calculate the energy release ΔE and release velocity Ev of the sample based on the obtained time difference Δt and the maximum height h of the reverse motion after the drop hammer reaches 0. Specifically, the energy release ΔE is obtained from the contact velocity v, the drop hammer mass m, and the reverse motion height h, specifically: ΔE = mv 2 -mgh;

[0033] The release rate Ev is obtained from the time difference Δt and the release amount ΔE, specifically: Ev=ΔE / Δt;

[0034] Step 4: Perform a geotechnical CT visualization test on the sample again to obtain its internal fissure degree, and take the average value of the fissure degree at the upper, middle and lower cross sections in Step 2 as the fissure development characteristic value P2. Based on the fissure development characteristic value P2 and the fissure development characteristic value P1 in Step 2, obtain the fissure development characteristic value change ΔP.

[0035] Step 5: Based on steps 3 and 4, obtain the relationship between the sample release amount ΔE, the release rate Ev, and the change in the characteristic value of fracture development ΔP.

[0036] Step 6: Take a new sample and repeat steps 2-5. Adjust the counterweight and contact speed during each drop hammer test. The counterweight adjustment range is from the sample with almost no damage to the sample with complete damage. That is, obtain a series of relationship points between the release amount ΔE, the release rate Ev and the change in the characteristic value of crack development ΔP. Fit the relationship points to obtain the relationship between the three ΔP = f(ΔE,v).

[0037] Step 7: Conduct a uniaxial compression test on the intact rock sample to obtain the full stress-strain curve. Combined with the loading rate, calculate the energy release amount and release rate. Then, based on the energy release amount and release rate and the correlation in Step 6, obtain the change in fracture development characteristic value ΔP. Evaluate the energy release effect based on the change in fracture development characteristic value ΔP.

[0038] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for evaluating the energy release effect of rocks, characterized in that, Includes the following steps: Step 1: Take multiple rock samples from the area to be tested; Step 2: Take one of the samples and obtain its internal crack degree. Take the average crack degree at multiple cross-sectional locations of the sample as the crack development characteristic value P1 of the sample. Step 3: Set the counterweight m and contact speed v A drop weight test was conducted and observed using a high-speed camera, based on the counterweight. m Contact speed v The release amount of the sample was calculated from data observed by a high-speed camera. ΔE and release rate Ev ; Step 4: Obtain the internal porosity of the sample again, and obtain the crack development characteristic value P2 of the sample after the drop hammer test according to the method in Step 2. Obtain the change in crack development characteristic value ΔP based on crack development characteristic value P2 and crack development characteristic value P1 in Step 2. Step 5: Based on steps 3 and 4, obtain the relationship between the sample release amount ΔE and release rate Ev and the change in fracture development characteristic value ΔP. Step 6: Replace the sample and repeat steps 2-5, adjusting the counterweight and contact speed for each drop hammer test to obtain a series of release amounts. ΔE Release speed Ev Changes in characteristic values ​​of fracture development ΔP The relationship between the three is obtained by fitting the relationship points; Step 7: Conduct uniaxial compression tests on intact rock samples to obtain full stress-strain curves. Combined with the loading rate, calculate the energy release amount and release rate. Based on the energy release amount and release rate, and the correlation from Step 6, obtain the change in fracture development characteristic values. ΔP And based on the change in the characteristic value of fracture development ΔP Evaluate the energy release effect; In step 3, a high-speed camera is used to observe the time difference between the falling hammer contacting the sample and the point at which the downward velocity reaches zero. Δ t And the maximum height of the reverse motion after the falling hammer's velocity reaches 0. h ; Energy release in step 3 ΔE From contact speed v Drop weight m and the height of the reverse movement h The result is as follows: ΔE=mv 2 -mgh ； Release speed Ev Due to time difference Δt and release amount ΔE The result is as follows: Ev=ΔE / Δt 。 2. The method for evaluating the energy release effect of rocks according to claim 1, characterized in that, The initial properties of the multiple rock samples taken from the area to be tested in step 1 are similar.

3. The method for evaluating the energy release effect of rocks according to claim 1, characterized in that, In step 6, the counterweight adjustment range is from minimally damaged sample to completely damaged sample.

4. The method for evaluating the energy release effect of rocks according to claim 1, characterized in that, Geotechnical CT visualization test was used to obtain the internal fracture degree of the sample.

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