Secondary stress isolation method for underground excavation space based on static rock breaking

Abstract

The application discloses a secondary stress isolation method for underground excavation space based on static rock breaking. The method comprises the following steps: arranging a drill hole array composed of rows of drill holes with equal diameters in auxiliary roadways such as through-vein roadways and connecting roadways of the underground excavation space; the drill holes comprise drill holes filled with static expanding agent and hollow drill holes; the drill hole array is located between the space to be excavated and the roadway to be maintained, and the projection direction of the drill hole array in a horizontal plane is consistent with the direction of the roadway to be maintained, so that a secondary stress isolation zone along the direction of the roadway to be maintained is formed, and then the secondary stress isolation is realized. The method uses the static rock breaking means, avoids the re-damage of the blasting impulse wave and vibration to the roadway in the blasting pressure relief process, is economical and practical, and is particularly suitable for the stability control of the roadway with large-range broken surrounding rock.

Description

Technical Field

[0001] This invention belongs to the field of underground excavation space surrounding rock stability control technology, and particularly relates to the technical field of secondary stress isolation methods in the underground space excavation process. Background Technology

[0002] Maintaining tunnel stability is crucial for ensuring normal production operations during underground excavation processes such as metal mining and tunnel construction. Existing research indicates that tunnel stability is not only related to intrinsic factors such as tunnel cross-sectional size and shape, the magnitude and distribution of ground stress, lithology, and adverse geological structures, but also closely related to the excavation activities in the space to be excavated. This is because secondary stresses induced by excavation disturbance disrupt the existing stress balance of the surrounding rock, causing localized stress concentrations and leading to tunnel deformation, which in turn exacerbates tunnel damage. Therefore, minimizing the adverse effects of excavation-induced secondary stresses on the tunnel, while keeping intrinsic factors such as tunnel cross-sectional shape, lithology, and adverse geological structures constant, is a vital means of maintaining tunnel stability.

[0003] Currently, from the perspective of stress control, existing technologies mainly employ two methods: drilling and blasting to reduce the impact of secondary stress induced by excavation on roadway stability.

[0004] The borehole stress relief method involves drilling horizontal or inclined boreholes of a certain depth and diameter from the roadway wall to the deeper surrounding rock, thereby transferring the stress concentration zone or high stress zone of the roadway surrounding rock to the deeper surrounding rock, and thus reducing the adverse effects of secondary stress on the roadway. It has the following limitations: (1) This method cannot completely isolate the influence of secondary stress induced by excavation on the roadway. Its stress relief effect depends to a large extent on the depth, diameter and spacing of the stress relief boreholes, and is limited by the engineering geological conditions of the underground excavation space, the shape and size of the roadway cross section, the magnitude and distribution of ground stress, etc. Even if the same project is carried out in different areas for borehole stress relief, the depth, diameter and spacing of the stress relief boreholes will not be the same; (2) This method has good applicability for local stress relief of the roadway, but when stress relief is carried out on the entire cross section of a certain area of ​​the roadway, it is necessary to carry out full-section stress relief borehole arrangement again along the roadway axis at a certain spacing, which has the problems of large workload and uneconomic.

[0005] The blasting decompression method is essentially to drill a certain number of blasting holes into the surrounding rock of the roadway, and then blast the bottom of the hole with concentrated explosives to form a broken "isolation zone", thereby separating the surrounding rock of the roadway from the deep surrounding rock, and thus achieving the purpose of isolating the secondary stress induced by excavation from the roadway. It has the following limitations: (1) Using traditional blasting methods to decompress the roadway can easily cause further damage and destruction to the surrounding rock of the roadway. The premise of this method is to avoid disturbing the shallow surrounding rock of the roadway as much as possible under the condition of ensuring the formation of a broken "isolation zone". However, in practice, facing different engineering geological conditions, especially for roadways with broken surrounding rock, unreasonable drilling layout, drilling depth and diameter, as well as unreasonable charge amount, detonation method and other blasting parameters, will significantly disturb the shallow surrounding rock of the roadway, thereby aggravating the damage to the roadway; (2) Similar to the drilling decompression method, this method has good applicability to local decompression of the roadway, but when carrying out full blast decompression of a certain area of ​​the roadway, there are problems of large engineering workload and uneconomicalness. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to propose a method for secondary stress isolation in underground excavation spaces based on static rock breaking. This method uses static rock breaking to avoid further damage to the roadway caused by blasting shock waves and vibrations generated during the blasting decompression process. It is economical and practical, and is particularly suitable for stability control of roadways with large-scale fractured surrounding rock.

[0007] The technical solution of the present invention is as follows:

[0008] A method for isolating secondary stress in underground excavation spaces based on static rock breaking includes: setting up a borehole array on one or more cross-sections in an auxiliary roadway of the underground excavation space; the borehole array consists of a row of boreholes of equal diameter; the boreholes include boreholes filled with static expanding agent (charge holes) and hollow boreholes (empty holes); the borehole array is located between the space to be excavated and the roadway to be maintained; the projection direction of the borehole array on the horizontal plane is consistent with the direction of the roadway to be maintained, so as to form a secondary stress isolation zone along the direction of the roadway to be maintained; wherein, the auxiliary roadway is connected to the roadway to be maintained, including one or more of the following: a cross-cutting roadway, a connecting roadway, and a return airway; the minimum horizontal distance between the borehole array and the roadway to be maintained is not less than 3 times the width of the roadway to be maintained, and the horizontal distance L2 from the starting position of the borehole to the boundary of the space to be excavated is greater than or equal to 0.5 times the average horizontal thickness L of the space to be excavated, i.e., L2 ≥ 0.5L.

[0009] According to some preferred embodiments of the present invention, the charging hole includes a horizontal charging hole and a downward charging hole inclined towards the roadway floor, wherein the hole is a horizontal hole, i.e., a horizontal void; the horizontal charging holes and the horizontal voids are arranged alternately and at equal intervals, and the depth is greater than the length of the area to be maintained along the roadway direction; the downward charging hole is located below the last horizontal void in the alternating arrangement; the depth of the downward charging hole is greater than that of the horizontal charging hole or the horizontal void, but its projected depth in the horizontal direction is equal to the depth of the horizontal charging hole or the horizontal void.

[0010] According to some preferred embodiments of the present invention, the distance between the opening of the horizontal charging hole and the horizontal empty hole is 5 to 8 times the borehole diameter; the distance between the opening of the downward charging hole and the adjacent horizontal empty hole is 5 to 8 times the borehole diameter; and the distance between the bottom of the downward charging hole and the adjacent horizontal empty hole is 10 to 20 times the borehole diameter.

[0011] According to some preferred embodiments of the present invention, the arrangement of the borehole array includes:

[0012] S1 selects the static expanding agent;

[0013] S2 selects the starting position of the drilling array;

[0014] S3 performs the layout and construction of the borehole array;

[0015] S4 fills the static expansion agent into the charging holes in the borehole array;

[0016] Wherein, S3 further includes:

[0017] Construction of the topmost horizontal charging hole is carried out along the direction of the roadway to be maintained, starting from the arching line of the auxiliary roadway where the borehole array is set.

[0018] Based on the distance between the opening and bottom of the downward charging hole and the horizontal hole, and ensuring that the distance between the opening of the downward charging hole and the floor of the auxiliary roadway is 20-40cm, the construction of the bottommost downward charging hole is carried out.

[0019] Based on the difference between the distance from the tunnel arching line to the tunnel floor and the distance from the opening position of the downward charging hole to the tunnel floor, combined with the hole opening distance between each horizontal charging hole and the adjacent horizontal empty hole, and the range of values ​​for the hole bottom distance between the downward charging hole and the adjacent horizontal empty hole, the remaining horizontal charging holes and horizontal empty holes are constructed sequentially and at equal intervals from top to top or from top to bottom.

[0020] According to some preferred embodiments of the present invention, the static expansion agent filling length of the horizontal charging hole satisfies:

[0021] L SY=L Z -(2~3)R J (3)

[0022] The static expansion agent filling length of the downward charging orifice satisfies:

[0023]

[0024] Among them, L SY L is the effective charge length of the horizontal charge hole. Z R is the drilling depth. J L is the borehole diameter. XY θ represents the effective charge length of the downward charging orifice, and θ is the inclination angle of the downward charging orifice.

[0025] According to some preferred embodiments of the present invention, the starting position of the borehole array on the auxiliary roadway where the borehole array is set satisfies the following:

[0026] When the horizontal distance L1 from the starting point of the hole to the roadway to be maintained is greater than or equal to 3 times the width a of the roadway to be maintained, i.e., L1≥3a; and the horizontal distance L2 from the starting point of the hole to the boundary of the space to be excavated is greater than or equal to 0.5 times the average horizontal thickness L of the space to be excavated, i.e., L2≥0.5L:

[0027] If the horizontal distance D between the boundary of the space to be excavated and the roadway to be maintained is greater than 3 times the sum of the width of the roadway to be maintained and 0.5 times the average thickness of the space to be excavated, i.e. D > 3a + 0.5L, then the horizontal distance d between the starting point and the roadway to be maintained is: 3a ≤ d ≤ D - 0.5L.

[0028] According to some preferred embodiments of the present invention, the static expanding agent is selected such that the circumferential tensile stress on the inner wall of the charging hole after the application of the static expanding agent is 1.5 to 2.0 times the tensile strength of the rock.

[0029] According to some preferred embodiments of the present invention, the selection of the static expanding agent includes:

[0030] The tensile strength σ of the rock in the area to be fractured was obtained through splitting tests. t Based on the stable circumferential tensile stress σ at the inner wall of the borehole θ0 Equal to 1.5 to 2.0 times the tensile strength σ of the rock in the area to be broken. t , i.e. σ θ0 =1.5~2.0σ t Determine the target circumferential tensile stress σ θ0 According to the target circumferential tensile stress σ θ0 The selection of a static expansion agent is determined by a combination of the target circumferential tensile stress and other selection conditions, including:

[0031] (1) Determine the borehole diameter R based on the rock drilling equipment. J ;

[0032] (2) Determine the water-cement ratio of the static expansion agent that can be selected based on the slurry fluidity, i.e., the water-cement ratio α0;

[0033] (3) Based on the determined borehole diameter R J With an optional water-cement ratio α0, the expansion pressure is tested using the external tube method. Based on the expansion pressure-time curve plotted by the test, the stable expansion pressure P0 corresponding to the flat section of the curve is obtained.

[0034] (4) Based on the obtained stable expansion pressure P0, the stable circumferential tensile stress σ at the borehole inner wall is calculated using the following formula. θ0 , i.e. σ θ0 Calculated value:

[0035] σ θ0 =p0(R 2 / r 2 +1)(R 2 / r 2 )-1 (2)

[0036] Where R and r are the outer and inner diameters of the borehole, respectively;

[0037] σ obtained from different static expanding agents θ0 Calculated value and target circumferential tensile stress σ θ0 Based on the approximate conditions, determine the selected static expansion agent;

[0038] The other selection criteria include cost and validity period.

[0039] According to some preferred embodiments of the present invention, the borehole diameter R J It is 60-90mm.

[0040] According to some preferred embodiments of the present invention, the optional water-cement ratio α0 is 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, or 0.50.

[0041] This invention can apply static expansion agents to the stability maintenance of underground excavated space tunnels. This method of isolating secondary stress in excavated space based on static rock breaking not only effectively overcomes the limitation of traditional blasting decompression which easily causes re-damage to the surrounding rock of the tunnel, but also fundamentally blocks the adverse effects of secondary stress induced by excavation on tunnel stability. It can greatly reduce tunnel maintenance costs and increase the service life of the tunnel, and is particularly suitable for stability control of tunnels with large-scale fractured surrounding rock. Attached Figure Description

[0042] Figure 1It is the underground excavation space model with stress isolation measures in Example 1.

[0043] Figure 2 It is the swelling pressure-time curve obtained in Example 2.

[0044] Figure 3 It is the schematic diagram of the starting hole position of the borehole in Example 3.

[0045] Figure 4 It is the schematic diagram of the specific layout structure of the borehole in Example 4.

[0046] Figure 5 It is the schematic diagram of pouring static fracture agent into the horizontal charging hole and the downward charging hole in Example 6. Specific implementation manners

[0047] The present invention will be described in detail below in conjunction with the embodiments and the drawings. However, it should be understood that the embodiments and the drawings are only used for exemplary description of the present invention, and cannot constitute any limitation to the protection scope of the present invention. All reasonable transformations and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0048] The following embodiments take the underground mining of a metal mine as an example.

[0049] Example 1

[0050] Referring to the underground excavation space model shown in the attached Figure 1 In the underground mining of a metal mine, a main roadway 1 and three crosshead roadways or connecting roadways 2, 3, and 4 communicating with the main roadway 1 are provided, that is, the second to fourth branch roadways; among them, the floor elevation of the main roadway 1 is +Hm, the roadway width is am, and the height is b m, that is, its cross-section is a×b m 2 ; There is an ore body k to be mined from bottom to top south of the main roadway 1. The occurrence elevation of the ore body k is +h~+Xm (h < H < X), and the average horizontal thickness is L m.

[0051] Theory and production practice show that: when the horizontal distance between the main roadway 1 and the ore body k is relatively close, the secondary stress induced during the upward mining of the ore body will surely affect the stability or damage degree of the main roadway 1. Further, in this underground excavation space model, the engineering geological conditions in the area between the third branch roadway 3 and the fourth branch roadway 4 of the main roadway 1 are poor, significantly affected by secondary stress, and difficult to maintain, which is the area w to be maintained.

[0052] To isolate the impact of secondary stresses generated during mining on the maintenance area w, this embodiment designs a row of boreholes 5 with the same orientation as the main roadway 1 in either the third or fourth branch roadway 3. Based on this, a static fracturing agent is used to fracture the boreholes 5, creating a fractured zone with the same orientation as the main roadway 1 and existing within a certain elevation range. This achieves the purpose of isolating secondary stresses and maintaining the stability of the roadway.

[0053] Example 2

[0054] In the underground excavation space model with stress isolation measures in Example 1, Q235 cold-worked steel pipes were used as the material to test the expansion pressure and circumferential tensile stress of the expansion agent, so as to select an expansion agent that matches the tensile strength of the ore rock.

[0055] Considering the wide variety of static fracturing agents, different types and specifications of static fracturing agents have different expansion pressures. Even for the same static fracturing agent, the actual expansion pressure generated is closely related to the borehole diameter, water-cement ratio, etc. This embodiment establishes the selection of static fracturing agent under the following conditions: under a certain borehole diameter and water-cement ratio, the circumferential tensile stress on the inner wall of the Q235 cold-worked steel pipe after applying the static fracturing agent is between 1.5 and 2.0 times the tensile strength of the rock.

[0056] The specific selection steps are as follows:

[0057] (1) Determine the borehole diameter R J

[0058] Based on the existing rock drilling equipment in the mine, if rock drilling equipment capable of drilling holes with a depth of not less than 10m and a maximum downward inclination angle of not less than 45° is selected, then the corresponding hole diameter R for horizontal and downward inclined drilling during static rock breaking should be chosen. J The maximum drilling diameter that the equipment can drill is preferably controlled between 60 and 90 mm.

[0059] (2) Determine the appropriate water-cement ratio α0 for the static expansion agent.

[0060] To facilitate the injection of static expanding agent into boreholes, the slurry should possess a certain degree of fluidity. This can be achieved by quantitatively or qualitatively testing the fluidity of expanding agents from different manufacturers and of different models under varying water-cement ratios. Specifically, qualitative testing can be used when relevant testing equipment is unavailable in the mine; it directly measures the minimum water-cement ratio α corresponding to the slurry in a fluid state. min As an expansive agent, the water-cement ratio α0 can be used for quantitative testing, such as by conducting slump tests according to the "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" (GB / T50080-2016), and taking the minimum water-cement ratio α corresponding to a slump H ≥ 16cm. minThe water-cement ratio α0 is suitable for the expansion agent used in static rock breaking on site; in this embodiment, slurries with water-cement ratios α of 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, and 0.50 are preferred.

[0061] (3) Determine the stable expansion pressure P0 of the inner wall of the Q235 cold-worked steel pipe.

[0062] Based on the determined borehole diameter R J With a water-cement ratio α0, the expansion pressure was tested using the external tube method according to standard JC506-2008 "Silent Debris", and the stable expansion pressure P0 was obtained as follows:

[0063] A. Calculate the inner wall expansion pressure P of the Q235 cold-worked steel pipe as follows:

[0064] p = E S (K 2 -1)[ε θ / (2-μ)] (1)

[0065] Where P is the expansion pressure, MPa; E S The elastic modulus of Q235 cold-worked steel pipe is taken as 2.060 × 10⁻⁶. 5 MPa; K is the ratio of the inner and outer diameters of the Q235 cold-worked steel pipe; μ is the Poisson's ratio of the Q235 cold-worked steel pipe, taken as 0.3; ε θ The radial strain of the Q235 cold-worked steel pipe was obtained by strain gauge monitoring.

[0066] B. Plot the time curve of the inner wall expansion pressure P of Q235 cold-worked steel pipe, and determine the steady expansion pressure P0 based on the curve, including:

[0067] Based on the radial strain ε of Q235 cold-worked steel pipe obtained from monitoring at different times θ The value is calculated to obtain different times t. i The corresponding different expansion pressures P i , in time t i The horizontal axis represents the expansion pressure P. i Plot the expansion pressure P-time curve with the vertical axis as the ordinate, as shown in the attached figure. Figure 2 As shown; the expansion pressure P corresponding to the horizontal segment in the expansion pressure-time curve is taken as the stable expansion pressure P0 of the inner wall of the Q235 cold-worked steel pipe.

[0068] (4) Determine the stable circumferential tensile stress σ on the inner wall of the Q235 cold-worked steel pipe. θ0 ,as follows:

[0069] Based on the obtained stable expansion pressure P0, the stable circumferential tensile stress σ at the borehole wall is calculated according to equation (2). θ0 :

[0070] σ θ0 =p0(R 2 / r 2 +1)(R 2 / r 2 )-1 (2)

[0071] Where: σ θ0 The circumferential tensile stress on the inner wall of the Q235 cold-worked steel pipe is MPa; R and r are the outer and inner diameters of the Q235 cold-worked steel pipe, respectively, in mm.

[0072] (5) Selection of static fracturing agent, as follows:

[0073] Determining the borehole diameter R J Water-cement ratio α0 and stable circumferential tensile stress σ θ0 Based on this, Figure 1 The rocks in the maintenance area w were subjected to Brazilian splitting tests according to the "Standard for Test Methods of Engineering Rock Mass" (GB / T50266-2013) to obtain the tensile strength σ of the rocks in the maintenance area. t And make a selection of static fracturing agent, specifically including:

[0074] A. Initial selection of static fracturing agent

[0075] According to the stable circumferential tensile stress σ on the inner wall of Q235 cold-worked steel pipe θ0 Equal to 1.5 to 2.0 times the tensile strength σ of the rock in the area to be broken. t , i.e. σ θ0 =1.5~2.0σ t The type and model of the expanding agent were initially selected based on its mechanical properties.

[0076] B. Determine the final static fracturing agent.

[0077] Based on the initial selection of static fracturing agents, the type of static fracturing agent suitable for the actual mining conditions was determined from aspects such as unit price, shelf life, and transportation cost.

[0078] Example 3

[0079] Furthermore, in the underground excavation space model with stress isolation measures in Example 1, the starting position 501 of borehole 5 is determined, referring to the attached... Figure 3, where: the main roadway 1 has a width of a m, a height of b m, and a floor elevation of +H m; the maximum distance from the area w to be maintained to the fourth roadway 4 is X4 m, and the maximum distance to the third roadway 3 is X3 m; the occurrence elevation of the ore body k to be mined is +h to +X m (h < H < X), the average horizontal thickness of the ore body is L m, the distance from the ore body boundary to the main roadway 1 is D m, and the ore body is mined from bottom to top. The starting position 501 of the borehole 5 can be selected in the third roadway 3 or the fourth roadway 4. In this embodiment, the case of selecting in the fourth roadway 4 is taken as an example.

[0080] To avoid disturbing the surrounding rock of the main roadway 1 during the borehole fracturing process, which will further exacerbate the damage of the main roadway 1. At the same time, to ensure the effect of secondary stress isolation, the distance from the boundary of the ore body to be mined to the main roadway 1 should not be too small. The starting position 501 of the borehole 5 satisfies the following conditions:

[0081] (1) According to the width of the main roadway 1, the distance L1 from the starting position 501 to the main roadway 1 is greater than or equal to 3 times the width a of the main roadway 1, that is, L1 ≥ 3a;

[0082] (2) According to the average horizontal thickness of the ore body to be mined, the distance L2 from the starting position 501 to the boundary of the ore body to be mined is greater than or equal to 0.5 times the average horizontal thickness L of the ore body to be mined, that is, L2 ≥ 0.5L;

[0083] Under the above conditions, let the distance from the selectable starting position 501 of the borehole to the main roadway 1 be d, then:

[0084] If the distance from the ore body boundary to the main roadway 1 is greater than the sum of 3 times the width of the main roadway 1 and 0.5 times the average horizontal thickness of the ore body to be mined, that is, D > 3a + 0.5L, then the value range of d is 3a to D - 0.5L, that is, 3a ≤ d ≤ D - 0.5L

[0085] Example 4

[0086] Refer to the appendix Figure 4 , on the basis of Example 3, the specific layout design of the borehole 5 is carried out. Among them, it is set that the cross-sectional dimensions such as the width, height, and the height of the springing line from the floor of the fourth roadway 4 are the same as the parameters of the main roadway 1, and the distance from the position of the springing line 401 to the roadway floor 402 is h1 m. According to whether the static fracturing agent is injected into the borehole, the boreholes are divided into two types: charged holes 51 and horizontal empty holes 52. Among them, the charged holes 51 need to be injected with static fracturing agent and are further divided into horizontal charged holes 511 and downward charged holes 512; the empty holes are horizontal holes and do not inject static fracturing agent, only providing the space required for rock fragmentation. The specific layout design parameters are as follows:

[0087] (1) The aperture of the charged hole 51 and the horizontal empty hole 52 is determined by the mine rock drilling equipment, that is, R J mm;

[0088] (2) Horizontal charging holes 511 and horizontal empty holes 52 are arranged alternately and at equal intervals, with a drilling depth of L. Z m, and L Z The distance from the maintenance area w to the fourth branch roadway is greater than X4, i.e., L Z ≥X4;

[0089] (3) The distance H3 between the openings of the horizontal charging hole 511 and the horizontal empty hole 52 is set to 5 to 8 times the borehole diameter, i.e., H3 = (5 to 8)R. J mm;

[0090] (4) The downward charging hole 512 is located below the last horizontal hole 52 in the alternating arrangement, and its projection depth in the direction of the horizontal charging hole 511 or the horizontal head hole 52 is L. Z m, and the distance H2 from the opening position to the bottom plate 402 of the roadway is set to 20-40cm;

[0091] (5) The distance H4 between the bottom charging hole 512 and the adjacent horizontal hole 52 is set to 5 to 8 times the borehole diameter, which is the same as the distance H3 between the horizontal charging hole 511 and the horizontal hole 52, i.e., H4 = H3 = (5 to 8)R. J mm;

[0092] (6) The bottom distance H5 between the downward charging hole 512 and the adjacent horizontal hole 52 is set to 10 to 20 times the borehole diameter, i.e., H5 = (10 to 20)R. J mm.

[0093] Example 5

[0094] Based on Example 4, both the charging hole 51 and the horizontal empty hole 52 are common drilling types in underground metal mining. Construction can be carried out according to the actual mining production process. To ensure construction quality, the charging hole 51 and the horizontal empty hole 52 should be kept as close to the same vertical plane as possible, with a maximum error of less than twice the borehole diameter. To ensure static rock breaking effect, this example is constructed in the following order:

[0095] (1) Construction of the top horizontal charging hole 511 is carried out along the direction of the main roadway 1 from the arch line 401 of the roadway.

[0096] (2) Based on the hole opening distance H4 and hole bottom distance H5 between the downward charging hole 512 and the horizontal hole 52, the construction of the bottommost downward charging hole 512 is carried out.

[0097] (3) Based on the difference between the distance h1 between the tunnel arching line 401 and the tunnel floor 402 and the distance H2 between the opening position of the downward charging hole 512 and the tunnel floor 402, and combined with the range of the hole opening distance H3 between each horizontal charging hole 511 and the adjacent horizontal empty hole 52, and the hole bottom distance H5 between the downward charging hole 512 and the adjacent horizontal empty hole 52, the remaining horizontal charging holes 511 and horizontal empty holes 52 are constructed sequentially and at equal intervals from top to top or from top to bottom.

[0098] Example 6

[0099] Based on Example 4, refer to Appendix Figure 5 The horizontal charging hole 511 and the downward charging hole 512, which require the injection of static fracturing agent, are charged, including:

[0100] (1) Obtain the charge length of the horizontal charge hole 511 according to formula (3):

[0101] L SY =L Z -(2~3)R J (3)

[0102] Among them, L SY L represents the effective charge length of the horizontal charge hole, in meters (m). Z R represents the drilling depth, in meters (m). J The borehole diameter is in meters (m).

[0103] (2) Obtain the charge length of the downward charging hole 512 according to equation (4):

[0104]

[0105] Among them, L XY θ represents the effective charge length of the downward charging orifice, in meters; θ represents the inclination angle of the downward charging orifice in degrees.

[0106] (3) Prepare the slurry in batches according to the number of boreholes. Tap water can be used for the slurry, but acidic water with a pH value less than 7 is preferred. The preparation steps are as follows:

[0107] A. Determine the density of the slurry: Based on the determined water-cement ratio α0, follow the "Standard for Geotechnical Testing Methods".

[0108] (GB / T50123-2019) The slurry density of the static crushing agent is tested to obtain the slurry density ρ;

[0109] B. Based on the effective charge length L of the horizontal charging hole SY Effective charge length L of downward charging port XY and the diameter R of the charging hole J Calculate the slurry consumption for the horizontal charging hole and the downward charging hole according to formulas (5) to (7) respectively:

[0110] Q SY =ρ×L SY ×S SY (5)

[0111] Q XY =ρ×L XY ×S XY (6)

[0112]

[0113] Among them, Q SY The amount of slurry used in the horizontal charging hole is expressed in kg; Q XY ρ is the slurry dosage for the downward charging hole, in kg; ρ is the slurry density, in kg / m³. 3 ;

[0114] C. Calculate the static expansion agent according to formulas (8) and (9) based on the slurry density ρ and the slurry water-cement ratio α0.

[0115] Water usage:

[0116]

[0117]

[0118] Among them, M P M W The figures represent the amounts of static expanding agent and water, respectively, in kg; Q represents the amount of drilling slurry, i.e., Q0. SY Or Q XY ;

[0119] D. Based on the amount of static expansion agent M used in drilling P Water consumption M W The preparation of slurry homogenization is carried out using mass measuring equipment, mixing equipment, and containers, including: accurately measuring the water for slurry preparation using mass measuring equipment and placing it in a container; accurately measuring the static expanding agent using mass measuring equipment and mixing the water in the container; and mixing the water and static expanding agent in the container using mixing equipment.

[0120] If the static expansion agent has specific requirements for stirring speed and stirring time, the operation should be strictly carried out according to the relevant instructions. If there are no special requirements, it is preferred that the stirring speed be no less than 200 r / min and the stirring time be no less than 10 min.

[0121] (4) Grouting. If the grout has good fluidity, it is preferable to use a grouting machine to grout it; if the grout has poor fluidity, it is preferable to roll the grout into strips and stuff them into the borehole, and then use a wooden stick or the like to tamp the grout.

[0122] (5) To ensure the static rock breaking effect, the preferred grouting time should meet the following conditions: after the grout preparation is completed, the grouting of a single borehole should be completed within 20 minutes; the grouting time of all boreholes should be within 4 hours.

[0123] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for isolating secondary stress in underground excavation spaces based on static rock breaking, characterized in that, It includes: in A borehole array is set on one or more cross sections of the auxiliary tunnels in the underground excavation space; The borehole array is located between the space to be excavated and the roadway to be maintained, and consists of several boreholes of equal diameter arranged in rows. The projection direction of the borehole array on the horizontal plane is consistent with the direction of the roadway to be maintained, so as to form a secondary stress isolation zone along the direction of the roadway to be maintained. The boreholes include boreholes filled with static expansion agent (charge holes) and hollow boreholes (empty holes). The auxiliary roadway is connected to the roadway to be maintained, and the auxiliary roadway includes one or more of the following: through roadway, connecting roadway, and return air roadway. The minimum horizontal distance between the borehole array and the roadway to be maintained is not less than 3 times the width of the roadway to be maintained, and the horizontal distance L2 from the starting position of the borehole to the boundary of the space to be excavated is greater than or equal to 0.5 times the average horizontal thickness L of the space to be excavated, i.e., L2 ≥ 0.5L. Among them, the charge holes... The system includes horizontal charging holes and downward charging holes inclined towards the roadway floor. The holes are horizontal, i.e., horizontal voids. The horizontal charging holes and horizontal voids are arranged alternately and equidistantly, with a depth greater than the length of the area to be maintained along the roadway direction. The downward charging hole is located below the last horizontal void in the alternating arrangement. The depth of the downward charging hole is greater than the depth of either the horizontal charging hole or the horizontal void, and its horizontal projection depth is equal to the depth of either the horizontal charging hole or the horizontal void. The distance between the openings of the horizontal charging holes and the horizontal voids is 5 to 8 times the borehole diameter. The distance between the openings of the downward charging holes and their adjacent horizontal voids is 5 to 8 times the borehole diameter, and the distance between the bottoms of the downward charging holes and their adjacent horizontal voids is 10 to 20 times the borehole diameter. The arrangement of the borehole array includes: S1 selects the static expanding agent; S2 selects the starting position of the drilling array; S3 performs the layout and construction of the borehole array; S4 fills the static expansion agent into the charging holes in the borehole array; Wherein, S3 further includes: Construction of the topmost horizontal charging hole is carried out along the direction of the roadway to be maintained, starting from the arching line of the auxiliary roadway where the borehole array is set. Based on the distance between the opening and the bottom of the downward charging hole and the horizontal hole, and ensuring that the distance between the opening of the downward charging hole and the bottom of the auxiliary roadway is 20-40cm, the construction of the bottommost downward charging hole is carried out. Based on the difference between the distance from the tunnel arching line to the tunnel floor and the distance from the opening position of the downward charging hole to the tunnel floor, combined with the hole opening distance between each horizontal charging hole and the adjacent horizontal empty hole, and the range of values ​​for the hole bottom distance between the downward charging hole and the adjacent horizontal empty hole, the remaining horizontal charging holes and horizontal empty holes are constructed sequentially and at equal intervals from top to top or from top to bottom.

2. The secondary stress isolation method according to claim 1, characterized in that, in, The static expansion agent filling length of the horizontal charging hole satisfies: L SY =L Z -(2~3)R J (3) The static expansion agent filling length of the downward charging orifice satisfies: Among them, L SY L is the effective charge length of the horizontal charge hole. Z R is the drilling depth. J L is the borehole diameter. XY θ represents the effective charge length of the downward charging orifice, and θ is the inclination angle of the downward charging orifice.

3. The secondary stress isolation method according to claim 1, characterized in that, The starting position of the borehole array on the auxiliary roadway where the borehole array is set satisfies the following: When the vertical distance L1 from the starting point of the hole to the roadway to be maintained is greater than or equal to 3 times the width a of the roadway to be maintained, i.e., L1≥3a; and the horizontal distance L2 from the starting point of the hole to the boundary of the space to be excavated is greater than or equal to 0.5 times the average horizontal thickness L of the ore body to be excavated, i.e., L2≥0.5L: If the horizontal distance D from the boundary of the ore body to the roadway to be maintained is greater than 3 times the sum of the width of the roadway to be maintained and 0.5 times the horizontal thickness of the space to be excavated, i.e., D > 3a + 0.5L, then the horizontal distance d from the starting point of the hole to the roadway to be maintained is: 3a ≤ d ≤ D - 0.5L.

4. The secondary stress isolation method according to claim 1, characterized in that, The static expansion agent is selected such that the circumferential tensile stress on the inner wall of the charging hole after the static expansion agent is applied is 1.5 to 2.0 times the tensile strength of the rock.

5. The secondary stress isolation method according to claim 4, characterized in that, The selection of the static expanding agent includes: The tensile strength σ of the rock in the area to be fractured was obtained through splitting tests. t Based on the stable circumferential tensile stress σ at the borehole wall θ0 Equal to 1.5 to 2.0 times the tensile strength σ of the rock in the area to be broken. t , i.e. σ θ0 =1.5~2.0σ t Determine the target circumferential tensile stress σ θ0 According to the target circumferential tensile stress σ θ0 The selection of a static expansion agent is determined by a combination of the target circumferential tensile stress and other selection conditions, including: (1) Determine the borehole diameter R based on the rock drilling equipment. J ; (2) Determine the water-cement ratio of the static expansion agent that can be selected based on the slurry fluidity, i.e., the water-cement ratio α0; (3) Based on the determined borehole diameter R J With an optional water-cement ratio α0, the expansion pressure is tested using the external tube method. Based on the expansion pressure-time curve plotted by the test, the stable expansion pressure P0 corresponding to the flat section of the curve is obtained. (4) Based on the obtained stable expansion pressure P0, the stable circumferential tensile stress σ at the borehole wall is calculated using the following formula. θ0 , i.e. σ θ0 Calculated value: σ θ0 =p0(R 2 / r 2 +1)(R 2 / r 2 )-1 (2) Where R and r are the outer and inner diameters of the borehole, respectively; σ obtained from different static expanding agents θ0 Calculated value and target circumferential tensile stress σ θ0 Based on the approximate conditions, determine the selected static expansion agent; The other selection criteria include cost and / or validity period.

6. The secondary stress isolation method according to claim 5, characterized in that, in, The borehole diameter R J The thickness is 60-90 mm; the optional water-cement ratio α0 is 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, or 0.50.

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