A device and method for measuring rock expansion coefficient on site

Abstract

The present invention discloses a device and method for measuring rock expansion coefficient on site. The device comprises a supporting bracket, a crushed stone compacting device and a volume measuring device. The crushed stone compacting device and the volume measuring device are connected by a pipeline, an oil pump is arranged on the pipeline, and special oil is contained in the volume measuring device; the crushed stone compacting device comprises a steel cylinder and a cover plate, a volume measuring scale is arranged on the outer wall of the steel cylinder, the outer diameter of the cover plate matches the inner diameter of the steel cylinder, the cover plate covers the steel cylinder from the inside of the steel cylinder, the cover plate can be raised and lowered in the steel cylinder, a pressure box is arranged at the inner bottom of the steel cylinder, a receiver is arranged on the outside of the steel cylinder, and the pressure box and the receiver communicate wirelessly; the supporting bracket has a safe and closed working space that can accommodate the crushed stone compacting device. The device and method can realize the measurement of the real crushed stone expansion coefficient of the goaf area rock, so as to make a preparatory prediction of the movement of the overlying rock layer, the surface subsidence and the deformation of the surrounding rock of the top cutting and retaining lane, which is of great significance to the prevention and control of the top cutting and retaining lane and surface subsidence disasters.

Description

Technical Field

[0001] The invention relates to the field of rock mechanics, and in particular to an on-site measurement device and method suitable for rock expansion coefficient in goaf areas. Background Art

[0002] After coal mining in my country, most of the goafs are treated by the full caving method, which leads to a huge area of ​​goafs in my country. The broken rocks in the goafs are in a long-term bearing state. Under the pressure of the overburden, the broken rocks produce compression deformation, which will directly affect the movement of the overburden and the surface subsidence. In the top cutting and tunneling engineering, the compression of the broken rocks in the goaf will affect the deformation of the surrounding rock of the top cutting and tunneling. The rock expansion coefficient of the goaf is one of the main factors that directly affect its compression deformation, which in turn affects the movement of the overburden, the surface subsidence and the deformation of the surrounding rock of the top cutting and tunneling. The larger the rock expansion coefficient, the larger the volume of the broken rock in the goaf, which can slow down the movement of the overburden. On the contrary, the smaller the rock expansion coefficient, the smaller the volume of the broken rock in the goaf, thus creating space for the movement of the overburden. The rock expansion coefficient is generally measured by laboratory tests, but due to the influence of the size effect, the rock expansion coefficient measured in the laboratory often deviates from the actual rock expansion coefficient, resulting in inaccurate prediction results of rock movement and surface subsidence. Therefore, there is an urgent need for a device that can perform on-site measurement of the rock expansion coefficient, so as to realize the measurement of the true expansion coefficient of rock in the goaf, so as to make a preparatory prediction of the movement of the overlying rock strata, surface subsidence and deformation of the surrounding rock of the top cutting and tunnel retention, which is of great significance for the prevention and control of top cutting and tunnel retention and surface subsidence disasters. Summary of the invention

[0003] In view of the problems existing in the prior art and in order to measure the true crushing expansion coefficient of rock in the goaf, the present invention provides an on-site measurement device and method for rock crushing expansion coefficient, which can realize the measurement of the true crushing expansion coefficient of rock in the goaf, thereby making accurate predictions on the movement of overlying rock strata and surface subsidence.

[0004] The technical solution adopted by the present invention is:

[0005] A rock expansion coefficient field measurement device comprises a rock crushing compaction device and a volume measurement device, wherein the rock crushing compaction device and the volume measurement device are connected via a pipeline, an oil pump is arranged on the pipeline, special oil is contained in the volume measurement device, and the rock crushing compaction device is placed in a goaf; the rock crushing compaction device comprises a steel cylinder and a cover plate, a volume measurement scale is arranged on the outer wall of the steel cylinder, the outer diameter of the cover plate matches the inner diameter of the steel cylinder, the cover plate covers the steel cylinder from the inside, the cover plate can be raised and lowered in the steel cylinder, a pressure box is arranged at the inner bottom of the steel cylinder, a receiver is arranged on the outside of the steel cylinder, and the pressure box and the receiver communicate wirelessly.

[0006] Furthermore, the on-site measuring device also includes a matching bracket, which includes a top beam, a base, a column, and four protective plates. The four protective plates are located below the tail of the top beam. The four protective plates all have a lifting function. The top beam and the four protective plates form a safe and enclosed working space that can accommodate the steel cylinder.

[0007] Furthermore, a plurality of convex grooves are evenly spaced on the inner cylinder wall of the steel cylinder, a plurality of protrusions are correspondingly arranged on the cover plate, a pulley is installed on each protrusion, and a protrusion and a matching pulley are embedded in a corresponding convex groove.

[0008] Furthermore, the volume measurement scale is a long strip of high-strength transparent glass, and the volume measurement scale is arranged on the outer wall of a convex groove of the steel cylinder.

[0009] Furthermore, a pipe joint is provided at the bottom of the steel cylinder. The pipe joint is located directly below the volume measuring scale. The pipe joint is connected to the pipeline. A filter is provided at the connection between the pipe joint and the steel cylinder. A valve is provided on the pipe joint.

[0010] A method for measuring rock expansion coefficient on site, using the above-mentioned measuring device, comprises the following steps:

[0011] S1, arrange the supporting support on the side of the mining working face close to the roadway, so that the edge of the supporting support coincides with the cutting top line, and the safe and closed working space at the tail of the supporting support is close to the goaf. As the working face moves forward, arrange the metal mesh and the rock-blocking support closely along the supporting support to prevent the broken rock in the goaf from flowing into the roadway;

[0012] S2, lift the outer baffle at the rear of the supporting bracket, lay the steel cylinder of the crushed stone compacting device flat into the safe and closed working space at the rear of the supporting bracket, and arrange the convex groove surface with the volume measuring scale and the pipe joint facing outwards to the roadway;

[0013] S3, lower the outer baffle to the pipe joint, raise the rear baffle to a certain height, so that part of the crushed rock in the goaf flows into the confined space, load the crushed rock into the steel cylinder to about 3 / 4 of its height, and level the top surface of the crushed rock. Read the total volume V0 at this time using the volume measuring ruler;

[0014] S4, use the oil pump to pump the special oil in the volume measuring device into the steel cylinder. When the gravel in the steel cylinder has just completely invaded the oil surface, close the oil pump and valve, and read the reduced volume V of the special oil in the volume measuring device. w , calculate the volume V of the crushed stone in the steel cylinder s =V0-V w , calculate the initial expansion coefficient of rock K 0=V s / V0;

[0015] S5, open the valve, pump the special oil in the steel cylinder into the volume measuring device, then close the valve, put the cover plate on the steel cylinder and let it fall freely, then fully raise the rear baffle, move the supporting bracket forward, so that the crushed stone compacting device is completely in the goaf, and the overlying rock layer gradually collapses and compacts the crushed stone compacting device;

[0016] S6, under the pressure of the overlying rock, the crushed rock in the steel cylinder will produce compression deformation, and the cover plate will gradually move downward. After a period of time t1, the vertical pressure σ1 borne by the crushed rock in the steel cylinder is measured by the receiver, and the total volume V1 is measured by the volume measuring scale. The crushing expansion coefficient of the crushed rock at this time is K1 = V s / V1; Similarly, after a period of time t2, the vertical pressure σ2 borne by the broken rock is read out, and the total volume V2 and the rock expansion coefficient K2 are calculated, and so on, until the expansion coefficient no longer changes significantly;

[0017] S7, drawing a crushing expansion coefficient-time curve and a crushing expansion coefficient-pressure curve according to the data in step S6.

[0018] Beneficial effect: The present invention specially designs the structure of the supporting bracket, so that in addition to the supporting function of the conventional hydraulic bracket, four liftable protective plates are designed at the rear thereof. The four protective plates and the top beam form a safe and enclosed working space of a steel cylinder that can accommodate a crushed rock compacting device. By loading a certain amount of crushed rock into the steel cylinder and filling it with special oil, the initial crushing expansion coefficient of the crushed rock can be obtained, and then the supporting bracket is removed to expose the crushed rock compacting device to the goaf. The collapse of the overlying rock stratum squeezes the cover plate to compress the volume of the crushed rock in the steel cylinder. The crushing expansion coefficient and the vertical pressure are measured and recorded at regular intervals, and the crushing expansion coefficient-time curve and the crushing expansion coefficient-pressure curve can be drawn, thereby realizing the on-site measurement of the real crushing expansion coefficient of the rock in the goaf, thereby making accurate predictions of the movement of the overlying rock strata and the surface subsidence. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the three-dimensional structure of the supporting bracket.

[0020] Figure 2 This is a schematic diagram of the placement and arrangement of the supporting bracket.

[0021] Figure 3 This is a schematic diagram of the structure of the broken rock expansion coefficient measuring device.

[0022] Figure 4 for Figure 3 Schematic diagram of the AA section.

[0023] Figure 5 for Figure 3Schematic diagram of another direction of the crushed rock compaction device.

[0024] Figure 6 Schematic diagram of the cover structure from top view.

[0025] Figure 7 Cross-sectional view of the installation of the device for measuring the coefficient of expansion.

[0026] Figure 8 Side view of the installation of the expansion coefficient measurement device.

[0027] Fig. 9 This is the expansion coefficient-time curve.

[0028] Fig.10 This is the expansion coefficient-pressure curve.

[0029] In the figure, 1-matching bracket, 11-top beam, 12-base, 13-column, 14-left baffle, 15-right baffle, 16-front baffle, 17-rear baffle; 2-crushed rock compacting device, 20 steel cylinder, 21-convex groove, 22-pipe joint, 23-filter screen, 24-pressure box, 25-volume measuring scale, 26-cover plate, 261-cover plate pulley, 262 protrusion; 3-pipeline, 4-valve, 5-oil pump, 6-volume measuring device, 7-receiver, 8-conventional hydraulic support. DETAILED DESCRIPTION

[0030] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings:

[0031] A rock expansion coefficient field measurement device and a supporting bracket therewith, wherein the supporting bracket 1 is mainly used to provide space for installing the rock expansion coefficient measurement device. Figure 1-2 As shown, the supporting bracket 1 is slightly longer than the ordinary conventional hydraulic bracket 8. When arranged, the bracket edge coincides with the top cutting line. The supporting bracket 1 is composed of a top beam 11, a base 12, a column 13 and four protective plates. The supporting bracket 1 has the same conventional supporting function as the conventional hydraulic bracket 8, but the difference lies in the structure of the four protective plates. The four protective plates are located at the rear of the bracket, including a left baffle 14, a right baffle 15 ( Figure 1 The front baffle 16 and the rear baffle 17 are blocked in the middle, and the four protective plates form a closed safe working space, and the four protective plates all have the function of lifting.

[0032] like Figure 3-6As shown, the crushing expansion coefficient field measurement device is mainly composed of a crushed rock compacting device 2, a pipeline 3, an oil pump 5, a volume measuring device 6 and a valve 4. When used on site, the crushed rock compacting device 2 is arranged in the goaf, and the volume measuring device 6 is arranged in the tunnel. The volume measuring device is a graduated container filled with special oil. The crushed rock compacting device 2 is composed of a steel cylinder 20, a convex groove 21, a cover plate 26, a volume measuring scale 25, a pipe joint 22 and a pressure box 24. The steel cylinder is a cylindrical cylinder made of high-strength steel. The outer diameter of the cover plate matches the inner diameter of the steel cylinder. The cover plate covers the steel cylinder from the inside of the steel cylinder, and the cover plate can be raised and lowered in the steel cylinder. In order to prevent the cover plate from rotating and tilting during the compression process, four convex grooves 21 are evenly designed around the steel cylinder 20 to fix the cover plate 26. The cover plate 26 is a steel plate of a certain thickness, and four square protrusions 262 are evenly arranged around it, so as to match the four convex grooves of the steel cylinder. Six pulleys 261 are arranged on each square protrusion 262, and two pulleys form a group. The arrangement of the pulleys and the convex grooves can prevent the cover plate from getting stuck during the descent process, thereby ensuring the smooth descent of the cover plate. The volume measurement scale 25 and the pipe joint 22 are designed on one of the convex grooves 21. The volume measurement scale 25 is a long strip of high-strength transparent glass. The convex groove has a gap of approximately the same area as the volume measurement scale. The volume measurement scale is connected and sealed with the convex groove by high-strength sealant. There are pre-calibrated volume markings on the volume measurement scale. The gravel condition in the steel cylinder can be observed through the glass scale. The pipe joint is located directly below the volume measurement scale. The pipe joint 22 is connected to the pipeline 3 outside the goaf. The connection between the pipe joint and the steel cylinder is also provided with a filter screen 23, and a valve 4 is provided on the pipe joint. The pressure box 24 is arranged at the bottom of the steel cylinder, and can monitor the vertical pressure on the crushed rocks in the device in real time and transmit it wirelessly to the receiver 7.

[0033] The following takes the top cutting and lane retaining project as an example to illustrate the on-site measurement method and steps of rock expansion coefficient:

[0034] 1. As Figure 2 , Figure 7 , Figure 8 As shown, directional blasting is carried out along the edge of the mining side of the tunnel on the advance working face to form a complete through-cutting line in the roof, and the working face advances forward. As the working face advances forward, a matching support 1 is arranged on the side of the mining working face close to the tunnel so that the edge of the matching support 1 coincides with the cutting line. A plurality of conventional hydraulic supports 8 are arranged side by side on the inner side of the matching support 1. The safe and enclosed working space at the tail of the matching support 1 is close to the goaf, and metal mesh and gangue retaining pillars are arranged closely along the matching support to prevent broken rocks from the goaf from flowing into the tunnel.

[0035] 2. In the enclosed safe working space formed by the four protective plates of the matching bracket, level the bottom plate to prevent the steel cylinder 20 of the gravel compacting device 2 from tilting during installation, raise the left baffle 14, and place the gravel compacting device 2 on the leveled bottom plate close to the left baffle 14, and arrange the convex groove with the volume measuring scale 25 and the pipe joint 22 to face outward toward the lane, so that people standing in the lane can observe the reading of the volume measuring scale.

[0036] 3. Lower the left baffle 14 and keep a certain distance between it and the bottom plate to prevent the pipe joint 22 from being crushed. Then raise the rear baffle 17 to a certain height to allow part of the crushed rocks in the goaf to flow into the enclosed space. Load the crushed rocks in the goaf into the steel cylinder 20 of the crushed rock compacting device 2. Stop when the steel cylinder is about 3 / 4 of the height. Smooth the top surface of the crushed rocks and read the total volume V0 at this time using the volume measuring scale 25.

[0037] 4. Connect the steel cylinder 20 to the pipeline 3 and the oil pump 5 in the tunnel through the pipeline joint 22, open the valve 4, and pump the special oil (this type of oil will not penetrate into the rock) stored in the volume measuring device 6 into the steel cylinder 20. The filter 23 can prevent the broken rocks from blocking the pipeline during back pumping. When the broken rocks in the steel cylinder 20 just completely penetrate the oil surface, close the valve 4 to stop the oil pump, and measure the reduced volume V of the special oil in the volume measuring device 6. w , and then the volume V of the crushed rock in the crushing and compacting device 2 is obtained s =V s =V0-V w , then the initial expansion coefficient of the rock is K 0 is: K 0=V s / V0.

[0038] 5. Open the valve 4, and completely pump the special oil in the crushed rock compacting device 2 into the volume measuring device 6 in reverse, then close the valve 4, and put the cover plate 26 into the steel cylinder 20 along the convex groove 21 to make it fall freely. At this time, the personnel completely evacuate the enclosed space formed by the four baffles, fully raise the rear baffle 17, and move the supporting bracket 1 forward, so that the crushed rock compacting device 2 is completely exposed in the goaf, and the overlying rock layer gradually collapses and compacts the cover plate 26 of the crushed rock compacting device 2.

[0039] 6. Under the pressure of the overlying rock, the crushed rock in the crushing and compacting device 2 will be compressed and deformed, and the cover plate will gradually move downward. Assuming that the crushing and compacting device 2 enters the goaf for a period of time t1, the vertical pressure σ1 of the crushed rock in the crushing and compacting device 2 is measured by the receiver, and the total volume V1 at this time is measured by the volume measuring scale 25. Then the crushing expansion coefficient of the crushed rock at this time is K 1 is: K1= V s / V1; Similarly, the vertical pressure σ2, the total volume V2 and the rock expansion coefficient at this time can be obtained after the rock compaction device 2 enters the goaf for a period of time t2. K 2, and so on, until the measured expansion coefficient stops changing.

[0040] 7. Through the above measurements, a series of time, pressure and expansion coefficient data can be obtained, (t0=0, K 0,σ0=0),(t1, K 1,σ1)(t2, K 2,σ2)···(t n , K n , σ n ), so that the expansion coefficient-time curve and the expansion coefficient-pressure curve can be made, such as Fig. 9 and Fig.10 As shown in the figure, this type of curve can make scientific predictions for the surrounding rock deformation and surface subsidence of the top cutting and tunnel retention.

[0041] Therefore, the above-mentioned rock expansion coefficient on-site measurement device can realize the measurement of the real rock expansion coefficient at the goaf site, so as to make a preparatory prediction of the movement of overlying rock strata, surface subsidence and deformation of surrounding rock of top cutting and tunnel retention, which is of great significance for the prevention and control of top cutting and tunnel retention and surface subsidence disasters.

Claims

1. A device for measuring rock expansion coefficient on site, characterized in that: It comprises a matching bracket, a crushed stone compacting device and a volume measuring device, wherein the crushed stone compacting device and the volume measuring device are connected through a pipeline, an oil pump is arranged on the pipeline, and special oil is contained in the volume measuring device; the crushed stone compacting device comprises a steel cylinder and a cover plate, a volume measuring scale is arranged on the outer wall of the steel cylinder, the outer diameter of the cover plate matches the inner diameter of the steel cylinder, the cover plate covers the steel cylinder from the inside, the cover plate can be raised and lowered in the steel cylinder, a pressure box is arranged at the inner bottom of the steel cylinder, a receiver is arranged on the outside of the steel cylinder, and the pressure box and the receiver communicate wirelessly; the matching bracket has a safe and closed working space that can accommodate the crushed stone compacting device; The supporting bracket includes a top beam, a base, a column, and four protective plates. The four protective plates are located below the tail of the top beam. The four protective plates have a lifting function. The top beam and the four protective plates form the safe and enclosed working space. The supporting bracket is initially arranged on a side of the mining working surface close to the tunnel, the edge of the supporting bracket coincides with the top cutting line, the safe and enclosed working space is close to the goaf, and the steel cylinder is placed in the safe and enclosed working space; A plurality of convex grooves are evenly spaced on the inner cylinder wall of the steel cylinder, a plurality of protrusions are correspondingly arranged on the cover plate, a pulley is installed on each protrusion, and a protrusion and a matching pulley can be embedded in a corresponding convex groove; The volume measurement scale is a long strip of high-strength transparent glass, which is arranged on the outer wall of a convex groove of the steel cylinder; A pipe joint is also provided at the bottom of the steel cylinder. The pipe joint is located directly below the volume measuring scale. The pipe joint is connected to the pipeline. A filter is also provided at the connection between the pipe joint and the steel cylinder. A valve is provided on the pipe joint.

2. A method for measuring the rock expansion coefficient on site, using the measuring device according to claim 1, comprising the following steps: S1, arrange the supporting support on the side of the mining working face close to the roadway, so that the edge of the supporting support coincides with the cutting top line, and the safe and closed working space at the tail of the supporting support is close to the goaf. As the working face moves forward, arrange the metal mesh and the rock-blocking support closely along the supporting support to prevent the broken rock in the goaf from flowing into the roadway; S2, lift the outer baffle at the rear of the supporting bracket, lay the steel cylinder of the crushed stone compacting device flat into the safe and closed working space at the rear of the supporting bracket, and arrange the convex groove surface with the volume measuring scale and the pipe joint facing outwards to the roadway; S3, lower the outer baffle to the pipe joint, raise the rear baffle to a certain height, so that part of the crushed rock in the goaf flows into the confined space, load the crushed rock into the steel cylinder to about 3 / 4 of its height, and stop, level the top surface of the crushed rock, and read the total volume V0 at this time by the volume measuring ruler; S4, use the oil pump to pump the special oil in the volume measuring device into the steel cylinder. When the gravel in the steel cylinder has just completely invaded the oil surface, close the oil pump and valve, and read the reduced volume V of the special oil in the volume measuring device. w , calculate the volume V of the crushed stone in the steel cylinder s =V0-V w , calculate the initial expansion coefficient of rock K 0=V s / V0; S5, open the valve, pump the special oil in the steel cylinder into the volume measuring device, then close the valve, put the cover plate on the steel cylinder and let it fall freely, then fully raise the rear baffle, move the supporting bracket forward, so that the crushed stone compacting device is completely in the goaf, and the overlying rock layer gradually collapses and compacts the crushed stone compacting device; S6, under the pressure of the overlying rock, the crushed rock in the steel cylinder will produce compression deformation, and the cover plate will gradually move downward. After a period of time t1, the vertical pressure σ1 borne by the crushed rock in the steel cylinder is measured by the receiver, and the total volume V1 is measured by the volume measuring scale. The crushing expansion coefficient of the crushed rock at this time is K1 = V s / V1; Similarly, after a period of time t2, the vertical pressure σ2 borne by the broken rock is read out, and the total volume V2 and the rock expansion coefficient K2 are calculated, and so on, until the expansion coefficient no longer changes significantly; S7, drawing a crushing expansion coefficient-time curve and a crushing expansion coefficient-pressure curve according to the data in step S6.

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