Elastic air spacer for deep hole charging and interval height calculation method of elastic air spacer

Abstract

The invention discloses an elastic air spacer for deep hole charging and a spacing height calculation method of the elastic air spacer in the technical field of mine blasting, the elastic air spacer comprises an elastic pipe and an air spacer, elastic buffering is conducted through the elastic pipe, the air spacer is used for spacing explosives, and the interval height of the explosives is calculated. The impact pressure of a blast hole filling cartridge bag on the air spacer can be effectively buffered, gas in the elastic pipe is pressed out from the gas outlet when subjected to the impact pressure, much impact energy is leaked in the form of discharging gas kinetic energy, the impact energy is obviously relieved from being continuously spread downwards to the air spacer, and the air spacer is prevented from being damaged. The shock resistance of the air spacer is greatly improved; according to the invention, the impact pressure of the filling cartridge bag on the air spacer is relieved through dynamic calculation and by utilizing the energy release mechanism of the plastic spring structure of the elastic tube, so that other solid spacer equipment can be effectively replaced, the blasting energy utilization rate and the operation efficiency are improved, and the explosive loading operation intensity and the spacer equipment cost can be reduced.

Description

Technical Field

[0001] This invention relates to the field of mining blasting technology, and in particular to an elastic air spacer for deep-hole charging and a method for calculating the spacer height. Background Technology

[0002] Deep-hole blasting technology plays a dominant role in mining. Under certain rock and explosive conditions, segmented interval charging can effectively reduce the peak impact pressure on the borehole wall, increase the stress wave duration, reduce blasting vibration, and improve blasting results. Simultaneously, air gaps can reduce the amount of explosive charged into the borehole, saving blasting costs. Therefore, using air gaps instead of traditional solid spacers such as PVC pipes, sand, and bamboo tubes can better improve the utilization rate of explosive energy, mitigate the problem of large fragments caused by poor blasting effects, and offer advantages such as convenient storage and transportation, low transportation costs, and reduced labor.

[0003] Deep-hole blasting requires pre-calculation of the required borehole depth in the mine, placement of explosives in the borehole, and then filling of air spacers. Based on the air spacer requirements of the explosives, explosives of appropriate equivalent amount and air spacers of appropriate length are placed in sequence at intervals. After placement, the explosive blasting is initiated.

[0004] As the required blasting depth of the mountain increases, the depth of the blast holes also increases. The time interval between loading explosives in the same blast hole will also be extended accordingly. When the explosives are loaded into the blast hole, the impact force on the air spacer also increases. When the air spacer is subjected to heavy impact, it may be squeezed and damaged due to insufficient bearing capacity, resulting in reduced or no air spacer function.

[0005] Air spacers are expensive, and the loss of one not only increases costs but also prevents the achievement of the required air gap distance for blasting, resulting in reduced blasting effectiveness. When an air spacer is damaged inside the borehole, it is difficult to remove. During the blasting process, the top air gap distance inside the borehole can only be determined after all the explosives have been loaded. By the time the air spacer is discovered to be damaged, it cannot be removed, and explosives cannot be reloaded. This prevents the blasting from proceeding as designed, resulting in a continuous charge structure inside the borehole, which leads to increased explosive consumption, higher pyrotechnic costs, and a deterioration in blasting effectiveness.

[0006] Based on this, the present invention designs an elastic air spacer for deep-hole loading and a method for calculating the spacer height, in order to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide an elastic air spacer for deep-hole blasting and a method for calculating its spacing height. This device incorporates an air spacer with a buffering function, specifically by adding an elastic tube at the upper end of the air spacer to facilitate buffering, thus forming an elastic inflatable spacer. The upper elastic tube weakens the impact kinetic energy, providing a buffering effect and improving the overall impact resistance of the elastic air spacer. Simultaneously, it is low in cost and simple in structure, making it widely applicable to deep-hole blasting in mines, achieving cost reduction and efficiency improvement. Furthermore, this method allows for the adaptation of elastic tubes of different heights at different depths within the blast hole to provide sufficient buffering, effectively protecting the structural stability of the air spacer and providing a reliable air gap distance for deep-hole blasting, thereby effectively improving the design success rate of blasting.

[0008] This invention is implemented as follows: an elastic air spacer for deep-hole explosive charging and a method for calculating its spacing height, comprising: A flexible air gap consists of a flexible tube and an air gap. The elastic tube is a hollow elastic corrugated tube, and a pressure relief hole is also provided on the elastic tube, which connects the inner and outer spaces of the elastic tube. The air gap is a closed hollow straight tube. An air inlet is opened at the lower end of the air gap. The air gap is connected to the outside through the air inlet. A sealing plug is provided on the air inlet. The elastic tube is fixedly installed at the upper end of the air separator; The elastic tubes of different heights and the air gaps of fixed heights are prefabricated into multiple integral elastic air gaps; The elastic tubes of different heights c are adapted to different blast hole depths; The method for calculating the height c of the elastic tube adapted to different blast hole depths includes the following steps: Step S1: When installing the explosive, the explosive is pressed vertically downwards along the blast hole onto the elastic air gap. The force and velocity changes during the impact process are analyzed, and an impulse equation is established for the normal direction along the upper surface of the elastic air gap during the impact. Based on the law of conservation of kinetic energy and the formula for the coefficient of restitution, the formula for the normal coefficient of restitution of the upper surface of the elastic air gap adapted to this device is:

[0009] in, This is the normal restitution coefficient, with a value of 0.1. The normal component of the incident velocity along the upper surface before the collision between the weight and the elastic air gap is given, in m·s. -1 ; The rebound velocity after the collision is the normal component along the upper surface, in m·s. -1 ; Step S2: Obtain the impulse formula for this device according to the impulse theorem:

[0010] Where m is the mass of the object, in tons (t); It is the normal impact force of the heavy object during the impact process, which varies with time. It is 0 at the beginning of the impact and reaches its maximum value when the falling speed of the heavy object is 0. The unit is kN. It is the normal component of the weight of the object, in kN; Step S3: Calculate each value in the impulse formula as follows:

[0011] In the formula, g is the acceleration due to gravity, taken as 9.81 m / s². -2 ;

[0012] In the formula, F1 is the pressure borne by the elastic tube; P0 is the initial pressure in Pa; and V1 is the internal volume of the elastic tube. It is the volume discharged under pressure, in liters (L); S is the top bearing area of ​​the elastic tube; k is the stiffness coefficient. Step S4, calculate the average pressure. If we assume the maximum impact pressure is k times the average pressure, then:

[0013] In the formula, is the average impact pressure, in kN; k is the impact force amplification factor, which is a constant. The impact force amplification factor varies under different conditions. In this study, a 120 mm diameter borehole is used as an example, and k is taken as 5.1. Step S5, calculate the specific impact force, then:

[0014] Simplifying the above formulas, we get:

[0015] The method for calculating the duration of the impact process is as follows:

[0016] In the formula, h is the thickness of the buffer layer.

[0017] According to classical free fall motion:

[0018] In the formula, H is the height of free fall, in meters (m).

[0019] Step S6: Compare whether the calculated impact force has damaged the air gap. Air gaps of different materials and diameters have different load-bearing capacities, and the load-bearing limit of the prefabricated air gap is a fixed value F. Therefore, calculate the specific impact force that the air gap will bear:

[0020] Compare the actual impact force on the air gap with the maximum impact force it can withstand. If Q is greater than F, it indicates that the air gap has been damaged. If Q equals F, it means that the air gap can just withstand the impact force; If Q is less than F, it means that the air gap can fully withstand the impact of heavy objects; This allows us to obtain the load-bearing limit of the air gap at different heights H, and adapt the elastic tubes with different inner cavity volumes V1. By using the inner cavity volume V1 and the load-bearing area S of the elastic tube, we can calculate the appropriate elastic tube buffer height c.

[0021] Furthermore, the air separator is a hollow straight tube made of resin material, and the elastic tube is a corrugated tube made of elastic PVC plastic.

[0022] Furthermore, the elastic tube has multiple replacement parts of different heights c; each elastic tube of different heights is connected to an air gap as an integral structure, and each air gap and elastic tube are prefabricated as an integral structure.

[0023] Furthermore, a one-way valve is provided on the inflation port, and a sealing plug is provided on the one-way valve of the inflation port.

[0024] Furthermore, the stiffness of the elastic tube is lower than the material stiffness of the air gap.

[0025] Furthermore, the maximum diameter of the elastic tube is the same as the diameter of the air spacer, and the length of the air spacer is the same as the spacing required for the explosive charge; the diameter of the air spacer is smaller than the diameter of the borehole, and the difference is no more than 2 cm.

[0026] The beneficial effects of this invention are: 1. The elastic tube of this device can effectively alleviate the downward impact pressure generated during the loading of explosives and prevent the air spacer from being squeezed and burst. 2. The size of the pressure relief hole is adapted to the internal volume of the plastic spring air pump and the impact pressure, which can play a good role in energy release. The pressure relief hole can protect the elastic tube and further increase the overall structural impact resistance of the elastic air gap. 3. The number and height of corrugated folds of the flexible tubes at different depths can be designed according to the actual site conditions or the design depth of the blast hole, thereby prefabricating matching flexible tubes and air gaps, and forming flexible air gaps of different lengths. The use is completely set in sequence, making the use more standardized and the application of medicine and air gaps more accurate. 4. During construction, this device can be installed simply by filling the elastic air gap from the borehole and spacing it with the explosive charge. The structure is simple, the cost is lower, and the operation is convenient. The elastic air gap has strong compressive strength and is easy to store and transport. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Figure 1 This is a schematic diagram of the structure of a single elastic air gap of the present invention; Figure 2 This is a schematic diagram of the arrangement of multiple elastic air spacers inside the borehole according to the present invention.

[0029] The attached diagram lists the components represented by each number as follows: 1-Elastic tube, 11-Pressure relief hole, 2-Air gap tube, 21-Inflation port. Detailed Implementation

[0030] Please see Figures 1 to 2 As shown, the present invention provides an elastic air spacer for deep-hole charging and a method for calculating the spacer height. To better understand the above technical solution, the following will describe the above technical solution in detail with reference to the accompanying drawings and specific embodiments.

[0031] In a specific embodiment of the technical solution of the present invention: The flexible air spacer is a prefabricated integral structure. The flexible air spacer has multiple models with different heights. According to different borehole depths, flexible air spacers of different heights are placed. That is, after filling explosives at different borehole depths, flexible air spacers are filled again to complete the intermittent distribution of explosives and achieve the purpose of intermittently distributing explosives for blasting. The flexible air gap includes a flexible tube 1 and an air gap 2; The elastic tube 1 is a hollow elastic bellows, and a pressure relief hole 11 is also provided on the elastic tube 1, which connects the inner and outer spaces of the elastic tube 1. Air gap 2 is a closed, hollow straight tube. An inflation port 21 is located at the lower end of air gap 2, connecting it to the outside. A sealing plug is installed on the inflation port 21. A one-way valve is also installed on the inflation port 21, and a sealing plug is installed on the one-way valve. The inflation port 21 allows for appropriate release of internal pressure, thus providing some resistance to impact forces. The elastic tube 1 is not connected to the inner cavity of air gap 2.

[0032] Air gap 2 is a hollow straight tube made of resin material, and elastic tube 1 is a corrugated tube made of elastic PVC plastic. The stiffness of elastic tube 1 is lower than that of air gap 2. By using different materials, the structure of air gap 2 is protected. In extreme cases, the structure of elastic tube 1 is discarded to maintain the integrity of air gap 2.

[0033] It should be noted that commercially available air gaps are expensive because they mainly rely on chemical reactions to generate air, requiring chemical substances and gaps that are corrosion-resistant and resistant to reactants, hence the high price. In contrast, the air gap 2 in this device is made of resin material and air is pumped in through an air inlet. It does not require corrosion resistance or resistance to chemical substances, only structural requirements. Furthermore, it does not require the filling of expensive chemical substances. Therefore, the cost of this device is much lower than that of existing chemically filled gaps.

[0034] The elastic tube 1 is fixedly installed at the upper end of the air gap 2; Multiple elastic air gaps with different heights and fixed heights are prefabricated as an integral structure. The maximum diameter of the elastic tube 1 is the same as the diameter of the air gap 2, and the length of the air gap 2 is the same as the spacing required for the blasting explosive. The diameter of the air gap 2 is smaller than the diameter of the blast hole, and the difference is no more than 2 cm, which makes it easy to install the elastic air gap of this device in the blast hole.

[0035] The flexible tube 1 has multiple replacement parts of different heights c; each flexible tube 1 of different heights is connected to an air gap 2 as an integral structure, and each air gap 2 and a flexible tube 1 are prefabricated as an integral structure. Based on different blast hole depths, elastic tubes 1 of different heights c are adapted; The calculation method for the height c of the elastic tube 1 adapted to different blast hole depths is as follows: Step S1: When installing the explosive, the explosive is pressed vertically downwards along the blast hole onto the elastic air gap. The force and velocity changes during the impact process are analyzed, and an impulse equation is established for the normal direction along the upper surface of the elastic air gap during the impact. Based on the law of conservation of kinetic energy and the formula for the coefficient of restitution, the formula for the normal coefficient of restitution of the upper surface of the elastic air gap adapted to this device is:

[0036] in, This is the normal restitution coefficient, with a value of 0.1. The normal component of the incident velocity along the upper surface before the collision between the weight and the elastic air gap is given, in m·s. -1 ; The rebound velocity after the collision is the normal component along the upper surface, in m·s. -1 ; Step S2: Obtain the impulse formula for this device according to the impulse theorem:

[0037] Where m is the mass of the object, in tons (t); It is the normal impact force of the heavy object during the impact process, which varies with time. It is 0 at the beginning of the impact and reaches its maximum value when the falling speed of the heavy object is 0. The unit is kN. It is the normal component of the weight of the object, in kN; Step S3: Calculate each value in the impulse formula as follows:

[0038] In the formula, g is the acceleration due to gravity, taken as 9.81 m / s². -2 ;

[0039] In the formula, F1 is the pressure borne by the elastic tube 1; P0 is the initial pressure in Pa; and V1 is the internal volume of the elastic tube 1. It is the volume discharged under pressure, in liters (L); S is the top bearing area of ​​elastic tube 1; k is the stiffness coefficient. Step S4, calculate the average pressure. If we assume the maximum impact pressure is k times the average pressure, then:

[0040] In the formula, is the average impact pressure, in kN; k is the impact force amplification factor, which is a constant. The impact force amplification factor varies under different conditions. In this study, a 120 mm cannon borehole is used as an example, and k is taken as 5.1. Step S5, calculate the specific impact force, then:

[0041] Simplifying the above formulas, we get:

[0042] The method for calculating the duration of the impact process is as follows:

[0043] In the formula, h is the thickness of the buffer layer.

[0044] According to classical free fall motion:

[0045] In the formula, H is the height of free fall, in meters (m).

[0046] Step S6: Compare whether the calculated impact force has damaged the air gap 2; Air gaps 2 made of different materials and with different diameters have different load-bearing capacities, and the load-bearing limit of a prefabricated air gap 2 is a fixed value F. Calculate the specific impact force that the air gap 2 will bear:

[0047] Compare the actual impact force on air gap 2 with the maximum impact force it can withstand. If Q is greater than F, it indicates that air gap 2 has been damaged. If Q equals F, it means that the air gap 2 can just withstand the impact force; If Q is less than F, it means that the air gap 2 can fully withstand the impact of heavy objects; Thus, the bearing limit of the air gap 2 at different heights H is obtained, and the elastic tube 1 with different inner cavity volumes V1 is adapted. The buffer height c of the adapted elastic tube 1 is calculated by using the inner cavity volume V1 of the elastic tube 1 and the bearing area S.

[0048] It should be noted that: 1. Engineering geological conditions For example, pyrite-type copper and zinc polymetallic large deposits are formed by volcanic eruption and sedimentation. The overall characteristics of the ore body are short strike length, deep burial, large horizontal thickness, and large reserves. The main products are copper concentrate and zinc concentrate.

[0049] The results of geological borehole core sampling show that the rock mass in deep mining areas is generally of poor quality. Due to the vibration disturbance caused by blasting in the mining areas on both sides, the integrity of the rock mass in the mining area has deteriorated, and joints and fissures have developed. At the same time, the mining area contains tuff, and the joint surfaces are flat and smooth. When drilling, the drill rod is prone to deflection along the joint direction. The inclined blast hole can easily reduce the falling speed of explosives and elastic air spacers. Therefore, the height c of the elastic tube 1 calculated by this method fully meets the actual impact force requirements and leaves a large margin.

[0050] 2. Based on the existing conditions of the mining area, some deep-hole sections with large diameters are mined using the open-cut and subsequent backfilling method. For example, in a 37-meter vertical borehole with a 2-meter bottom plug, the borehole diameter is 120mm. A 4-kilogram emulsion explosive is selected as the standard weight. According to the classical free-fall equation, 26.20 m / s² is obtained. -1 .

[0051] In reality, the heavy object will collide and rub against the borehole wall during its descent, significantly reducing the explosive velocity and thus the maximum impact force. However, to ensure a reasonable selection of the spacer thickness, considering the maximum impact velocity is more appropriate. A buffer thickness of 1.18m is chosen, including the buffer extension length of the elastic tube 1 and the buffer length of the lower air spacer 2. The pressure of the elastic tube 1 is then taken as F1 = 6KN. Substituting the above data into the formula yields 11.65KN. Based on the selected material, length, and diameter, the static load of the bottom air spacer 2 can be calculated as F = 10KN.

[0052] According to the formula, Q = 6.7KN, which is less than F. Therefore, the elastic air gap with a design buffer thickness of 0.18m for elastic tube 1 fully meets the impact resistance requirements. By using an elastic tube for elastic buffering, the air spacer effectively buffers the impact pressure of the explosive charge on the air spacer. Furthermore, when subjected to impact pressure, the gas inside the elastic tube is forced out through the outlet, causing a significant amount of impact energy to leak out as the kinetic energy of the expelled gas. This significantly reduces the downward propagation of impact energy to the air spacer, thus greatly improving its impact resistance. This invention utilizes the energy dissipation mechanism of the plastic spring structure of the elastic tube to reduce the impact pressure of the explosive charge on the air spacer. Through dynamic calculations, the spring length is scientifically and rationally selected to ensure the air spacer's impact resistance. This invention can effectively replace other spacer materials, improving blasting energy utilization and operational efficiency, while also reducing the intensity of charging operations and the cost of spacer materials.

[0053] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A flexible air spacer for deep hole charge and a method for calculating the spacer height thereof, characterized in that, The utility model relates to a kind of elastic air spacer, including: Elastic air spacer includes an elastic tube (1) and an air spacer (2); The elastic tube (1) is hollow elastic bellows, and the elastic tube (1) is further provided with a pressure relief hole (11), and the pressure relief hole (11) is communicated with the inside and outside of the elastic tube (1); The air spacer (2) is a closed hollow straight tube, and the lower end of the air spacer (2) is provided with an inflation port (21), and the air spacer (2) is communicated with the outside through the inflation port (21), and the inflation port (21) is provided with a sealing plug; The elastic tube (1) is fixedly arranged at the upper end of the air spacer (2); The elastic tube (1) of different heights and the air spacer (2) of fixed height are prefabricated into a plurality of elastic air spacers of integral structure. According to different blasting hole depths, the elastic tube (1) of different height c is adapted. The height c of the elastic tube (1) adapted to different blasting hole depths is calculated by the following steps: Step S1, when installing explosives, the explosives are vertically pressed downward along the blasting hole to compress the elastic air spacer, and the force and speed change during the impact of the weight are established, the normal impulse equation of the weight along the upper surface of the elastic air spacer is established, and the normal recovery coefficient formula of the upper surface of the elastic air spacer of the device is adapted according to the recovery coefficient formula of the law of conservation of kinetic energy: wherein, is the normal restitution coefficient, taking the value 0.1, is the normal component of the incident velocity of the weight and the elastic air spacer before the impact along the upper surface, with units m·s -1 ; is the normal component of the rebound velocity after the impact along the upper surface, with units m·s -1 ; Step S2, according to the impulse theorem, the formula of the impulse received by the device is obtained: Wherein, m is the mass of the weight, unit t; is the normal impact force of the weight during the impact process, which changes with time, and is 0 at the beginning of the impact action, and the value is the largest when the falling speed of the weight is 0, unit KN; is the normal component of the weight of the weight, unit KN; Step S3, calculate the values in the impulse formula as follows: In the formula, g is the acceleration of gravity, taken 9.81 m·s -2 ; In the formula, F1 is the pressure borne by the elastic tube (1); P0 is the pressure in the initial state, unit Pa; V1 is the inner cavity volume of the elastic tube (1); is the volume discharged after being subjected to pressure, unit L; S is the top bearing area of the elastic tube (1); k is the stiffness coefficient; Step S4, calculate the average pressure, if the maximum impact pressure is assumed to be k times the average pressure, then: In the formula, is the average impact pressure, unit KN; k is the impact force amplification coefficient, k is a constant, the impact force amplification coefficient is different under different conditions, k is 5.1; Step S5, calculating the specific impact force, then there are: The above formula is arranged as: The calculation method of the impact process duration is: In the formula, h is the thickness of the buffer layer. According to the classical free fall motion: In the formula, H is the free fall height, unit m. Step S6, comparing whether the specific impact force calculated causes damage to the air spacer (2); The bearing capacity of the air spacer (2) with different materials and diameters is different, and the limit of the bearing capacity of the air spacer (2) which has been prefabricated is a fixed value F, so the specific impact force borne by the air spacer (2) is calculated: By comparing the actual impact force borne by the air spacer (2) with the limit impact force that can be borne, if Q is greater than F, it indicates that the air spacer (2) is damaged. If Q is equal to F, it indicates that the air spacer (2) can just bear the impact force; If Q is less than F, it indicates that the air spacer (2) can completely bear the impact force of the weight; Thus, the bearing limit of the air spacer (2) at different height H positions is obtained, and the elastic tube (1) of different internal cavity volume V1 is adapted, and the adapted elastic tube (1) buffer height c is calculated by the internal cavity volume V1 and the bearing area S of the elastic tube (1).

2. The elastic air spacer of a deep hole charge and a method for calculating the spacer height thereof according to claim 1, wherein: The air spacer (2) is a hollow straight tube made of resin material, and the elastic tube (1) is a corrugated tube made of elastic PVC plastic.

3. The elastic air spacer of a deep hole charge and a method for calculating the spacer height thereof according to claim 1, wherein: The elastic tube (1) has a plurality of replacement parts of different height c, each elastic tube (1) of different height is connected with an air spacer (2) to form an integral structure, and each air spacer (2) is prefabricated with an elastic tube (1) to form an integral structure.

4. The elastic air spacer of a deep hole charge and a method for calculating the spacer height thereof according to claim 1, wherein: The inflation port (21) is provided with a one-way valve, and the one-way valve of the inflation port (21) is provided with a sealing plug.

5. The elastic air spacer of a deep hole charge and a method for calculating the spacer height thereof according to claim 1, wherein: The stiffness of the elastic tube (1) is lower than the material stiffness of the air spacer (2), and the internal cavities of the elastic tube (1) and the air spacer (2) are not communicated with each other.

6. The elastic air spacer of a deep hole charge and a method for calculating the spacer height thereof according to claim 1, wherein: The maximum diameter of the elastic tube (1) is the same as the diameter of the air spacer (2), and the length of the air spacer (2) is the same as the required spacing of blasting explosives; the diameter of the air spacer (2) is less than the diameter of the blast hole, and the difference is not more than 2 cm.

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