Rock mass longitudinal wave velocity inversion method based on measurement of detonation velocity in blast hole

Abstract

The invention relates to the technical field of blasting, and discloses a rock mass longitudinal wave velocity inversion method based on blast hole detonation velocity measurement, which comprises the following steps: drilling a blast hole; explosive and a monitoring probe of monitoring equipment are arranged in the blast hole; detonating the explosive, monitoring and outputting a curve chart that the propagation distance of the detonation wave changes along with the propagation time through monitoring equipment, the longitudinal coordinate of the curve chart being the propagation distance of the detonation wave, and the horizontal coordinate of the curve chart being the propagation time of the detonation wave; according to the distribution condition of each rock stratum in the blast hole, the curve graph is divided into a plurality of curve segments, and each curve segment corresponds to the propagation process of detonation waves in the corresponding rock stratum; the slope of each curve section is calculated, and actually measured explosive detonation velocities of different rock stratums are obtained; and substituting the actually measured explosive detonation velocity into the theoretical formula of the explosive detonation velocity and the longitudinal wave velocity of the rock, and inverting the longitudinal wave velocity of the corresponding rock stratum. Through the inversion method provided by the invention, detonation wave monitoring and longitudinal wave velocity inversion of different rock stratums through which the blast hole passes can be completed through one-time blasting.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of blasting technology, in particular to a rock mass P-wave velocity inversion method based on blast hole internal detonation velocity measurement. BACKGROUND

[0002] The P-wave velocity of rock mass is an important parameter reflecting the physical and mechanical properties of rock mass and engineering index, and has a wide application in evaluating the quality of rock mass and assessing site conditions. According to the P-wave velocity test technology, the physical parameters of rock in underground engineering, water conservancy and hydropower engineering, tunnel engineering and building foundation can be quickly and accurately obtained, and it can also be used for engineering geological survey and engineering quality detection.

[0003] The existing rock mass P-wave velocity test mostly adopts the direct wave method, which is to place an artificial vibration source such as explosive or vibration exciter in the drilled hole, and set vibration sensors on the surface of the surrounding rock near the drilled hole, record the direct wave first arrival signal after the vibration source is excited, and calculate the P-wave velocity of rock mass combined with the propagation distance and propagation time of P-wave. After the calculation is completed, the position of the vibration source is changed to calculate the P-wave velocity of rock mass in different areas.

[0004] The test principle and process of the direct wave method are relatively simple, but it can only measure the average P-wave velocity in a certain area. In actual engineering, the geological conditions are complex, the same measurement area may include different types of rock layers, and the P-wave propagation velocity of rock mass is very fast, so direct measurement of rock mass P-wave velocity has the problems of large error and low accuracy; and in the data acquisition process, the direct wave generated by the vibration source will quickly attenuate with the increase of distance, and when the distance exceeds a certain distance, the vibration sensor will not be able to collect the direct wave form, so the direct wave method has the problem of small applicable range. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a rock mass P-wave velocity inversion method based on blast hole internal detonation velocity measurement.

[0006] The present application provides a rock mass P-wave velocity inversion method based on blast hole internal detonation velocity measurement, comprising: Drilling a blast hole at a position to be tested; Arranging explosive and monitoring probes of monitoring equipment in the blast hole; Detonating the explosive, monitoring and outputting the curve graph of the propagation distance of detonation wave changing with the propagation time by the monitoring equipment, the vertical coordinate of the curve graph is the propagation distance of detonation wave, and the horizontal coordinate of the curve graph is the propagation time of detonation wave; According to the distribution of each rock layer in the blast hole, the curve graph is divided into a plurality of curve segments, and each curve segment corresponds to the propagation process of detonation wave in the corresponding rock layer; Calculating the slope of each curve segment to obtain the measured detonation velocity of different rock layers; The measured explosive detonation velocity is substituted into the theoretical formula of explosive detonation velocity and rock longitudinal wave velocity to inversely calculate the longitudinal wave velocity of the corresponding rock stratum.

[0007] Optionally, the theoretical formula is a theoretical formula under a constraint condition: In the formula, is the measured explosive detonation velocity, , is a constant, and is 4.563 and 0.688, respectively; is an impedance ratio of the explosive and the constraint medium, ; is a density of the constraint medium, is a longitudinal wave velocity of the constraint medium, is a density of the explosive in the blast hole; is a velocity of an ideal detonation wave propagating in the explosive; is a detonation velocity of the explosive of a given diameter under an unconstrained condition.

[0008] Optionally, the calculation formula of the detonation velocity of the explosive of a given diameter under the unconstrained condition is as follows: In the formula, , is a fitting parameter, is the diameter of the explosive.

[0009] Optionally, after the explosive and the monitoring probe of the monitoring device are arranged in the blast hole, before the explosive is detonated, the method further comprises connecting the detonator on the explosive cartridge to the initiator, and plugging the blast hole with the crushed stone.

[0010] Optionally, the monitoring device is a Micro Trap detonation velocity tester.

[0011] Optionally, the Micro Trap detonation velocity tester comprises a VOD probe line, and a weight connected to a free end of the VOD probe line.

[0012] Optionally, when the VOD probe line of the Micro Trap detonation velocity tester is arranged in the blast hole, the weight is first connected to the free end of the VOD probe line, and then the VOD probe line is lowered to the bottom of the blast hole under the traction of the weight.

[0013] Optionally, drilling the blast hole at the position to be tested comprises: removing dust and loose broken rock mass on the surface of the area to be tested; selecting a drilling position, and drilling a blast hole with a depth of 10 m and a diameter of 90 mm.

[0014] ​The technical scheme provided by the embodiment of the present application has the following advantages compared with the prior art. 1. By arranging the monitoring probe of the monitoring device in the blast hole, the propagation process of the detonation wave in different rock layers in the blast hole is monitored, a curve graph of the propagation distance changing with time is drawn, the slope of the curve segment corresponding to different rock layers is calculated to obtain the measured detonation velocity of each rock layer, and finally the longitudinal wave velocity of each rock layer is obtained by inversion, so that the inversion method of the present application not only realizes the layered and accurate measurement of the longitudinal wave velocities of different rock layers, but also completes the detonation wave monitoring and longitudinal wave velocity inversion of different rock layers through one blasting, without the need for multiple adjustment of the vibration source position as in the direct wave method, so that the test process is simplified, the operation steps are reduced, and the test efficiency is significantly improved.

[0015] 2. The detonation wave propagates in the blast hole, and the monitoring probe is directly arranged in the blast hole, so that the propagation signal of the detonation wave in different rock layers can be effectively captured, and the propagation signal is little affected by the propagation distance, so that the propagation signal can cover all kinds of rock layer regions through which the blast hole passes, and the application range of the test is greatly expanded. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A flowchart of a rock mass longitudinal wave velocity inversion method based on blast hole detonation velocity measurement is provided for the first embodiment of the present application.

[0017] Figure 2 A structural schematic diagram of the blasting device is provided for the first embodiment of the present application.

[0018] Figure 3 A curve graph of the propagation distance of the detonation wave changing with the propagation time is provided for the first embodiment of the present application.

[0019] Explanation of reference numerals: 1, initiator; 2, signal line; 3, explosive; 4, detonator; 5, blast hole; 6, monitoring device; 7, probe line; 8, counterweight. DETAILED DESCRIPTION

[0020] The specific embodiment of the present application will be described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present application is not limited by the specific embodiment.

[0021] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the technical solutions of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation of the present application.

[0022] Embodiment one: As shown in Figure 1 and Figure 2 , the present embodiment provides a rock mass longitudinal wave velocity inversion method based on borehole detonation velocity measurement, comprising: Step one, drill a blast hole 5 at the position to be tested; In this embodiment, the test area near the explosion source is investigated, and the dust and loose broken rock on the surface of the test area is removed. A blast hole with a depth of 10m and a diameter of 90mm is drilled at a suitable position.

[0023] Step two, arrange explosives 3 and monitoring probes of monitoring equipment 6 in the blast hole 5; In this embodiment, the monitoring equipment 6 is a Micro Trap detonation velocity tester, and the bottom of the VOD probe line 7 (the VOD probe line is the monitoring probe of the monitoring equipment 6) of the Micro Trap detonation velocity tester is connected with a counterweight 8, which can lower the probe line 7 to the bottom of the blast hole.

[0024] In this embodiment, after the drilling is completed, the counterweight 8 is connected at the bottom of the VOD probe line 7, the probe line 7 is lowered to the bottom of the blast hole 5, and then the explosive charge is installed in the blast hole 5; the probe line 7 is connected to the Micro Trap detonation data recorder so that it is in a sampling state.

[0025] Step three, detonate the explosives 3, monitor and output the curve of the propagation distance of the detonation wave changing with the propagation time by the monitoring equipment 6, the ordinate of the curve is the propagation distance of the detonation wave, and the abscissa of the curve is the propagation time of the detonation wave; In this embodiment, after arranging the explosives 3 and the monitoring probes of the monitoring equipment 6 in the blast hole 5, before detonating the explosives 3, it further includes connecting the detonator 4 on the explosive charge with the initiator 1, and blocking the blast hole 5 with gravel.

[0026] In this embodiment, the detonator 4 is connected with the initiator 1 through a signal line; the ordinate takes the bottom of the probe line as the coordinate origin.

[0027] Step four, according to the distribution of each stratum in the blast hole, the curve is divided into multiple curve segments, and each curve segment corresponds to the propagation process of the blast wave in the corresponding stratum; The test principle of the Micro Trap detonation velocity data logger is as follows: a VOD resistance probe is placed in the blast hole, and as the blast wave front advances, the speed probe gradually shortens. When the length shortens by ΔL, the voltage drop per unit time is ΔV / Δt=I×R0(ΔL) / Δt; the length of the resistance probe reduced per unit time is ΔL / Δt=(1 / I×R0)×(ΔV / Δt), and ΔL / Δt is the speed of the propagation of the blast wave, that is, the detonation velocity D=ΔL / Δt=(1 / I×R0)×(ΔV / Δt)=k×dV / dt. In the formula, ΔL is the length of the speed probe shortened, ΔV is the voltage drop per unit time Δt, R0 is the resistance value of the probe per meter of length, D is the detonation velocity of the explosive, k is a constant, and the Micro Trap detonation velocity data logger can convert the voltage-time curve (ΔV / Δt) into the curve of the length of the probe changing with time (ΔL / Δt), wherein the slope of the L-t curve is the measured detonation velocity of the explosive. The Micro Trap in-hole detonation velocity test system directly measures the detonation velocity of the explosive from the hole, so that the result is more accurate.

[0028] Step five, the slope of each curve segment is calculated to obtain the measured detonation velocity of the explosive in different strata; As shown in Figure 3 In this embodiment, the strata in the blast hole are, in order from deep to shallow, medium-hard rock, soft rock, and hard rock, and the measured detonation velocities of the explosive are, in order, 1333.3 m / s, 4375 m / s, and 5000 m / s, as can be seen from the figure.

[0029] When calculating the slope, since the propagation speed of the detonation velocity in the same stratum is constant in the theoretical state, when processing the curve segment, the part close to a straight line is used to calculate the slope, as shown in Figure 3 The corresponding stratum deviates from this rule at the initial and terminal stages, and therefore should be excluded.

[0030] Step six, the measured detonation velocity of the explosive is substituted into the theoretical formula of the detonation velocity of the explosive and the longitudinal wave velocity of the rock to inversely calculate the longitudinal wave velocity of the corresponding stratum.

[0031] In this embodiment, the theoretical formula is the theoretical formula under the constraint condition: In the formula, is the impedance ratio of the explosive and the constraint medium, ; , is a constant, and is 4.563 and 0.688, respectively; is the density of the constraint medium, to constrain the P-wave velocity of the medium (i.e. to calculate the P-wave velocity of the rock mass by inversion), to the density of the explosive in the blast hole; to the detonation velocity of the explosive of a given diameter under unconstrained conditions: wherein, to the velocity of the ideal detonation wave propagating in the explosive, to the fitting parameters, to the diameter of the explosive 3.

[0032] According to the field test, the P-wave velocity of the rock at the bottom of the blast hole is 2230 m / s, and since the explosive parameters are known, the measured detonation velocity of the explosive 4375 m / s (i.e. ) is substituted into the formula, and the inverted P-wave velocity of the rock = 2101 m / s, which is 5.8% different from the measured result in the field. Therefore, the rock mass P-wave velocity inversion method based on the measurement of the detonation velocity in the blast hole is reasonable.

[0033] The above is only a few specific embodiments of the present application, but the embodiments of the present application are not limited thereto, and any changes that can be thought of by those skilled in the art shall fall within the protection scope of the present application.​

Claims

1. A rock mass P-wave velocity inversion method based on borehole detonation velocity measurement, characterized in that, The application relates to a method for measuring the longitudinal wave velocity of rock. The method comprises the following steps: drilling a blast hole (5) at a position to be tested; arranging an explosive (3) and a monitoring probe of a monitoring device (6) in the blast hole (5); detonating the explosive (3) and monitoring and outputting a curve of the propagation distance of a detonation wave changing with the propagation time of the detonation wave by the monitoring device (6), wherein the ordinate of the curve is the propagation distance of the detonation wave, and the abscissa of the curve is the propagation time of the detonation wave; dividing the curve into a plurality of curve segments according to the distribution of each rock layer in the blast hole, and each curve segment corresponds to the propagation process of the detonation wave in the corresponding rock layer; calculating the slope of each curve segment to obtain the measured detonation velocity of the explosive in different rock layers; 2. The borehole detonation velocity measurement based rock mass P-wave velocity inversion method according to claim 1, characterized in that, substituting the measured detonation velocity of the explosive into a theoretical formula of the detonation velocity of the explosive and the longitudinal wave velocity of rock to inversely calculate the longitudinal wave velocity of the corresponding rock layer. where D is the measured detonation velocity of the explosive, , are constants, 4.563 and 0.688, respectively; Z is the impedance ratio of the explosive to the confinement medium, ; p is the density of the confinement medium, c is the longitudinal wave velocity of the confinement medium, p is the density of the explosive in the borehole; D is the velocity of the ideal detonation wave propagating in the explosive; D is the detonation velocity of the explosive in the given diameter under unconfined conditions.

3. The borehole-detonation-velocity-measurement-based rock mass P-wave velocity inversion method according to claim 2, characterized in that, The detonation velocity of given diameter explosive under the condition of no constraint The formula is: wherein , are fitting parameters, is the diameter of the explosive (3).

4. The borehole detonation velocity measurement based rock mass P-wave velocity inversion method according to claim 1, characterized in that, The theoretical formula is a theoretical formula under a constraint condition.

5. The borehole detonation velocity measurement based rock mass P-wave velocity inversion method according to claim 1, characterized in that, Before detonating the explosive (3) after arranging the explosive (3) and the monitoring probe of the monitoring device (6) in the blast hole (5), the method further comprises the steps of connecting a detonator (4) on the explosive cartridge (3) to a detonator (1) and blocking the blast hole (5) by using gravel.

6. The borehole detonation velocity measurement based rock mass P-wave velocity inversion method according to claim 5, characterized in that, The monitoring device (6) is a Micro Trap detonation velocity tester.

7. The borehole-detonation-velocity-measurement-based rock mass P-wave velocity inversion method according to claim 6, characterized in that, The Micro Trap detonation velocity tester comprises a VOD probe line (7) and a counterweight (8) connected to the free end of the VOD probe line (7).

8. The borehole detonation velocity measurement based rock mass P-wave velocity inversion method according to claim 1, characterized in that, When arranging the VOD probe line (7) of the Micro Trap detonation velocity tester in the blast hole (5), the counterweight (8) is first connected to the free end of the VOD probe line (7), and then the VOD probe line (7) is lowered to the bottom of the blast hole under the traction of the counterweight (8). Drilling a blast hole (5) at a position to be tested comprises the following steps: removing dust and loose broken rock on the surface of the region to be tested; selecting a drilling position and drilling a blast hole with a depth of 10 m and a diameter of 90 mm.

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