A method for combined excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting

Abstract

This invention relates to the field of underground engineering construction technology for water conservancy and hydropower, specifically to a method for coordinated excavation of high sidewalls in underground powerhouses using layered pre-splitting and smooth blasting. The method includes layering along height and dividing along the plane; drilling pre-splitting holes and detonating them to form pre-splitting isolation joints; establishing a vibration velocity prediction model to determine the charge in the main blasting zone; detonating the main blasting zone and using smooth blasting for edge trimming; and updating the parameters of the vibration velocity prediction model. This invention improves excavation efficiency while protecting the supported surrounding rock and concrete structures of different ages through the combined use of three methods: advanced pre-splitting isolation joints, single-shot charge inversion with cross-splitting transmission coefficients, and measured recursive feedback.

Description

Technical Field

[0001] This invention relates to the field of underground engineering construction technology for water conservancy and hydropower, specifically to a method for the coordinated excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting. Background Technology

[0002] The underground powerhouse walls of large hydroelectric power stations and pumped storage power stations are generally excavated in layers from top to bottom: the middle layer is blasted with trenching, the outer contours of the protective layers on both sides are smoothed with blasting, and after the excavation of the upper layer is completed, anchor bolts, anchor cables, and shotcrete support are immediately installed, and concrete structures such as rock wall crane beams are poured at designated elevations. When the lower layers continue to be blasted, the supported surrounding rock and the poured concrete must repeatedly withstand dozens of blasting vibrations.

[0003] In current construction, the single-explosive charge is determined based on Sadovsky's empirical formula, while the site coefficient and attenuation index are taken from empirical values ​​of similar projects or a small amount of test blast data before construction begins, and are not updated with the actual response. For poured concrete, a single vibration velocity limit is usually applied, regardless of the age.

[0004] Furthermore, in existing processes, pre-splitting blasting is only used as a contouring method. The barrier effect of pre-splitting on blasting seismic waves has not been systematically designed and quantitatively utilized: the number of rows of splitting, the opening width, and the advance depth are not designed with the seismic isolation effect as the design goal. The attenuation contribution of the splitting is not taken into account when predicting vibrations. The actual vibration velocity inside the splitting is overestimated, and the amount of explosives available is underestimated.

[0005] The combination of these problems resulted in both cumulative damage to the retained rock mass and low excavation efficiency during the excavation of the high sidewalls of the underground powerhouse. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for the coordinated excavation of high sidewalls in underground powerhouses using layered pre-splitting and smooth blasting. By pre-forming pre-splitting isolation joints and incorporating their seismic isolation effect into the single-shot charge inversion, combined with the rolling feedback of measured vibration velocities, quantitative and differentiated coordinated protection is implemented for the supported surrounding rock and concrete structures of different ages.

[0007] This invention is achieved through the following technical solution:

[0008] A method for combined excavation of high sidewalls in underground powerhouses using layered pre-splitting and smooth blasting includes the following steps:

[0009] S1. Divide the sidewall excavation area into layers along the height and into partitions along the plane. Each layer is divided into a main blasting zone and a contour protection layer. The contour protection layer is close to the design contour line of the sidewall, and adjacent partitions maintain a staggered excavation sequence.

[0010] S2. Drill pre-splitting holes outside the design outline of the sidewall. The pre-splitting holes are drilled ahead of the current main blasting layer and detonated before the main blasting zone to form a pre-splitting isolation joint.

[0011] Unfilled anti-cracking holes are drilled at the lower end of the pre-cracked isolation joint along the joint direction.

[0012] S3. Establish a vibration velocity prediction model containing the transmission coefficient through the gap, invert the allowable single-shot charge amount according to the allowable vibration velocity of each protected object, and determine the charge in the main blasting zone by the minimum value among the allowable single-shot charges.

[0013] S4. After the main blasting zone is detonated, the outline protection layer is trimmed with smooth blasting.

[0014] S5. Measure the particle velocity at each protected object, update the parameters of the velocity prediction model, and use it for the inversion of the allowable single-effect charge in the next excavation cycle.

[0015] Optionally, the pre-cracked holes are arranged in a double row, including an inner row of pre-cracked holes and an outer row of pre-cracked holes;

[0016] The inner row of pre-cracked holes is arranged along the design outline of the sidewall;

[0017] The outer row of pre-splitting holes is offset relative to the inner row of pre-splitting holes towards the main blasting zone;

[0018] The positions of the inner row of pre-splitting holes and the outer row of pre-splitting holes are staggered along the direction of the crack, and are arranged in a staggered pattern.

[0019] Optionally, the diameter of the anti-cracking hole is larger than the diameter of the pre-cracking hole, the depth of the anti-cracking hole exceeds the bottom of the pre-cracking isolation joint, and the hole section exceeding the bottom of the joint constitutes an ultra-deep section.

[0020] The opening of the anti-crack hole is centered to form the pre-crack hole of the next layer, and is drilled axially along the ultra-deep section so that the pre-crack isolation seams of the upper and lower adjacent layers are collinear at the position of the anti-crack hole.

[0021] Optionally, adjacent zones shall maintain a vertical stagger of at least one layer, and the blasting time interval between adjacent zones at the same elevation shall be no less than one support follow-up cycle.

[0022] Optionally, the through-slit transmission coefficient Determine by the following formula: In the formula, The equivalent opening width of the pre-cracked isolation joint. For reference width, is the transmission attenuation coefficient.

[0023] Optionally, when the inversion allows for a single explosive charge, the number of times the propagation path from the detonation center to the protected object crosses the pre-splitting isolation joint is included, and the number of times is determined according to the following rules:

[0024] On the excavation plane, make a horizontal projection of the line connecting the blast center and the protected object. The number of intersections between this horizontal projection and the direction line of each pre-splitting isolation joint is counted as the number of crossings.

[0025] Among them, the intersection point is not counted when it is located on the extension line outside the crack arresting holes at both ends of the pre-cracked isolation joint;

[0026] When the elevation of the bursting core is lower than the bottom elevation of the pre-splitting isolation joint, a vertical section check is performed, and lines that pass through the projection of the joint surface below the bottom elevation are not counted.

[0027] Optionally, the protected object is a concrete structure, which allows for vibration velocities of [missing information]. Determine the concrete age according to the following formula: In the formula, The age of the concrete. The permissible vibration velocity for a 28-day-old age. , The coefficient of the intensity growth curve. The vibration velocity-intensity sensitivity index is used; periods when the age is below the preset lower limit are designated as explosion-proof windows.

[0028] Optionally, in S5, vibration velocity measurement points are set up at each protected object, the logarithm of the vibration velocity prediction model is taken to obtain a linear form, and the parameters of the vibration velocity prediction model are updated cyclically using a recursive weighted least squares method with a forgetting factor.

[0029] During parameter updates, the parameter update amount of a single excavation cycle is truncated when it exceeds the preset limit. No update is triggered when the prediction residuals of all measuring points in the excavation cycle fall within the preset threshold range. When the residual of a single measuring point exceeds the discrete criterion of the residuals of all measuring points, it is judged as an abnormal measuring point that needs to be removed.

[0030] Within the same excavation cycle, measuring points whose propagation paths do not cross the pre-cracked isolation joint are paired with measuring points whose propagation paths cross at least one pre-cracked isolation joint, and the transmission coefficient across the joint and the remaining parameters of the vibration velocity prediction model are identified separately.

[0031] Optionally, the linear charge density of the pre-cracked hole Determine by the following formula: In the formula, As the baseline charge density, This represents the initial in-situ stress perpendicular to the pre-splitting surface at the current stratification depth. For the tensile strength of rock, This is the influence coefficient of geostress;

[0032] Decoupling coefficient of peripheral holes in smooth blasting Adjust according to the layer depth using the following formula: In the formula, The first-layer decoupling coefficient, This represents the depth of the current layer's bottom surface from the top of the side wall. This is the total height of the side wall. These are the gradient coefficients.

[0033] Optionally, the pre-splitting holes and the crack-stopping holes are constructed by a tracked down-the-hole drill, the main blasting holes in the main blasting zone are constructed by a rock drilling rig, and the smooth blasting trimming holes are constructed by a hand-held rock drill.

[0034] The three types of drilling rigs operate in parallel with spatial misalignment, following the pre-splitting advance layer, the main blasting current layer, and the light blasting delayed trimming layer.

[0035] This invention improves excavation efficiency while protecting the supported surrounding rock and concrete structures of different ages by combining three methods: advanced pre-cracked isolation joints, single-effect charge inversion with transmission coefficient through the joint, and measured recursive feedback. Attached Figure Description

[0036] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, but do not constitute a limitation on the embodiments of the present invention.

[0037] Figure 1 A flowchart illustrating the overall process of a method for co-excavation of high sidewalls in underground powerhouses using layered pre-splitting and smooth blasting, as provided in an embodiment of the present invention.

[0038] Figure 2 This is a planar schematic diagram of the double-row staggered arrangement of pre-cracked isolation joints, the location of crack-stopping holes, and the determination of the number of times the joints are passed through in an embodiment of the present invention;

[0039] Figure 3 This is a schematic elevation sectional view of the relationship between the layered and staggered excavation of the high sidewall and the advance of the pre-splitting isolation joint in an embodiment of the present invention.

[0040] Figure 4 This is a data flow diagram of the monitoring, recursive regression, and dosage inversion closed-loop control in this embodiment of the invention.

[0041] Attached reference numerals: 1-Sidewall design outline; 2-Inner row of pre-splitting holes; 3-Outer row of pre-splitting holes; 4-Pre-splitting isolation joint; 5-Splitting stop hole; 6-Main blasting zone; 7-Transition zone; 8-Outline protection layer; 9-Rock wall crane beam; 10-Vibration velocity measuring point; 11-Current main blasting layer; 12-Advanced pre-splitting layer. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0043] It should also be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0044] The protected objects mentioned in this article include, but are not limited to, the supported surrounding rock, the rock wall crane beam 9, the machine nest and other poured concrete structures, as well as other existing structures within the blasting influence range that require limiting the vibration velocity of mass points.

[0045] The transmission coefficient mentioned in this article refers to the coefficient of the attenuation of the vibration amplitude of the blasted seismic wave after passing through a pre-cracked isolation joint 4. It includes, but is not limited to, the form determined exponentially according to the opening width of the joint, and the form calibrated by the measured vibration velocity ratio of paired measuring points on both sides of the joint.

[0046] The ultra-deep section mentioned in this article refers to the section of the crack-stopping hole 5 that extends beyond the bottom of the pre-cracked isolation joint 4.

[0047] Where there is no conflict, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0048] Example 1

[0049] This embodiment provides a method for the coordinated excavation of high sidewalls in underground powerhouses using layered pre-splitting and smooth blasting. The overall process is as follows: Figure 1 As shown, it includes steps S1 to S5.

[0050] S1. Divide the excavation area of ​​the sidewall into layers along the height and into partitions along the plane. Each layer is divided into a main blasting zone 6 and a contour protection layer 8 that is close to the design outline 1 of the sidewall. Adjacent partitions maintain a staggered excavation sequence.

[0051] The layer height can range from 3 to 5m, for example, 3m, 3.5m, 4.5m, and 5m. In addition to the main blasting zone 6 and the outline protection layer 8, a transition zone 7 can be set between the two in the plane of each layer; the width of the outline protection layer 8 can be 2 to 3m, for example, 2m, 2.5m, and 3m, and the width of the transition zone 7 can be 3 to 5m.

[0052] The purpose of staggered excavation sequence is to ensure that any protected object only experiences blasting vibrations from one zone within the same time period, preventing the superposition of vibrations from adjacent zones.

[0053] S2. Drill pre-splitting holes outside the design outline 1 of the sidewall. The pre-splitting holes are drilled ahead of the current main blasting layer 11 and detonated before the main blasting zone 6 to form a pre-splitting isolation joint 4. Drill unloaded anti-splitting holes 5 along the joint direction at the lower end of the pre-splitting isolation joint 4.

[0054] like Figure 3 As shown, the pre-splitting holes are arranged 0.3 to 0.5 m outside the design outline 1 of the sidewall, for example, 0.3 m, 0.4 m, or 0.5 m. The pre-splitting holes are drilled 111.5 to 2 layers ahead of the current main blasting layer to form an advanced pre-splitting layer segment 12, for example, 1.5 or 2 layers ahead.

[0055] The pre-splitting isolation joint 4 is formed before the main blast. Firstly, it controls the shape of the sidewall outline, and secondly, it forms a wave impedance abrupt change interface between the preserved rock mass and the blast source. When the seismic wave passes through the joint, it is reflected and attenuated, thus becoming a vibration reduction barrier.

[0056] The crack arresting hole 5 is set at the bottom elevation of each pre-splitting isolation joint 4 to prevent the joint tip from extending into the lower layer of retained rock mass under subsequent blasting disturbance.

[0057] S3. Establish a vibration velocity prediction model containing the transmission coefficient through the gap, invert the allowable single-shot charge amount according to the allowable vibration velocity of each protected object, and determine the charge amount of the main blasting zone 6 by the minimum value among the allowable single-shot charges.

[0058] The vibration velocity prediction model introduces a transmissivity through a slit based on the Sadovsky formula to predict the vibration velocity of the protected object. The vibration velocity prediction is as follows: In the formula, For a single-effect dose, From the center of the explosion to the protected object distance, For site coefficient, The decay exponent, The transmission coefficient through the slit is... From the center of the explosion to the protected object The number of times the propagation path crosses the pre-cracked isolation joint 4, correction term The seismic isolation benefits of pre-cracked isolation joint 4 are included in the forecast.

[0059] For each protected object, according to its permissible vibration velocity The inversion allows for the minimum charge per shot, taking the minimum value across the entire field: The allowable vibration velocity of the supported surrounding rock is taken as a fixed value.

[0060] S4. After the main blasting zone 6 is detonated, the outline protection layer 8 is trimmed with smooth blasting.

[0061] Main blasting zone 6 employs electronic detonators for sequential, time-delayed detonation, with inter-hole and inter-row delays ensuring that the amount of explosive charge detonated within any given time window does not exceed [a certain threshold]. Settings. The charge parameters for peripheral holes in smooth blasting can be adjusted according to the initial in-situ stress at the stratification depth.

[0062] S5. Measure the particle velocity at each protected object, update the parameters of the vibration velocity prediction model, and use it to invert the allowable single-effect charge in the next excavation cycle.

[0063] In each blasting cycle, peak vibration velocity and dominant frequency are collected at vibration velocity measuring point 10 at each protected object. The model parameters are updated according to recursive regression to form a closed loop of "pre-crack isolation - graded control - monitoring feedback": the pre-crack isolation joint 4 is the hardware of the vibration reduction barrier, and the prediction model containing the transmission coefficient of the joint is the software for quantitatively utilizing the barrier.

[0064] In a specific engineering example, the underground powerhouse of a pumped storage power station has an excavation dimension of 218m in length, 26.5m in width, and a maximum sidewall height of 66m. The surrounding rock is Class II to III granite, with a measured longitudinal wave velocity of 4200 to 4700m / s and a rock saturated tensile strength of 6.2MPa. The rock wall crane beam 9 is poured at the upper elevation of the sidewall layer by layer.

[0065] The sidewall section below the top arch layer and the rock wall beam layer is divided into 9 layers, with a layer height of 3.5m. Each layer is divided into a central main blasting zone 6 (width determined by the excavation cross-section), two side transition zones 7 (4m wide), and an outline protection layer 8 (2.5m wide). The main blasting holes have a diameter of 48mm, a depth of 3.3m, a hole grid of 1.6m × 1.4m, and a single hole charge of 3.6kg. The smooth blasting trimming holes have a diameter of 42mm, a hole spacing of 0.45m, and a smooth blasting layer thickness of 0.6m.

[0066] Furthermore, a multi-machine collaborative drilling method was used for excavation.

[0067] Adjacent zones should maintain a vertical offset of at least one layer. The blasting time interval between adjacent zones at the same elevation should be no less than one support follow-up cycle, ensuring that no protected object is subjected to superimposed vibrations from the two zones. Furthermore, support follow-up should be completed after the blasting of the previous zone before blasting of the adjacent zone. In a specific example, the vertical offset between adjacent zones is one layer, i.e., 3.5m.

[0068] Drilling operations are divided according to hole shape accuracy and hole depth requirements:

[0069] The pre-splitting holes and crack-stopping holes 5 are constructed by crawler-type down-the-hole drills. These holes are deep holes, and the opening and inclination angle accuracy requirements are the highest. The opening deviation is controlled within 5cm and the inclination angle deviation is controlled within 0.5°.

[0070] The main blasting hole in the main blasting zone 6 and the transition zone hole 7 were constructed using a rock drilling rig. These are medium-deep holes, and efficiency was the priority.

[0071] The smooth blasting trimming holes and local patching holes are constructed using hand-held pneumatic drills, which are short holes and allow for flexible and mobile operation.

[0072] The three types of drilling rigs operate in parallel with spatial staggered configurations within the same layer, with pre-splitting layer ahead, main blasting layer in front, and light blasting layer behind for trimming. Drilling, blasting, and slag removal processes are seamlessly connected.

[0073] Before detonation of explosives in any zone, drilling rigs on adjacent work faces are deployed according to a unified drilling and blasting sequence table, retreating to the supported section or withdrawing beyond the blasting warning line. Parallel operations resume after the warning is lifted. This ensures the geometric accuracy of the pre-splitting surface, controls the dispersion of the measured equivalent opening width, and in turn supports the stability of the estimated cross-splitting transmission coefficient.

[0074] Example 2

[0075] Based on Example 1, this embodiment describes the double-row staggered structure of the pre-cracked isolation joint 4 and the setting and guiding connection method of the crack-stopping hole 5.

[0076] like Figure 2 As shown, the pre-splitting holes are arranged in two rows, including an inner row of pre-splitting holes 2 and an outer row of pre-splitting holes 3. The inner row of pre-splitting holes 2 is arranged along the design outline 1 of the sidewall, and the outer row of pre-splitting holes 3 is offset relative to the inner row of pre-splitting holes 2 towards the main blasting zone 6. The offset amount, i.e., the row spacing, is in the range of 0.4 to 0.6 m, for example, 0.4 m, 0.5 m, or 0.6 m. The positions of the two rows of pre-splitting holes are staggered along the direction of the crack, and the offset amount is preferably half a hole spacing, arranged in a staggered quincunx pattern.

[0077] The inner row of seams controls the contour shaping, while the outer row of seams is superimposed with a wave impedance abrupt change interface. When seismic waves travel from the blast source to the preserved rock mass, they penetrate the seams twice and attenuate twice. The staggered arrangement ensures that the unconnected sections of the two seams are offset from each other, avoiding the formation of a continuous leakage channel. In a specific example, the pre-splitting holes have a diameter of 90 mm and a spacing of 0.8 m. The inner row is arranged 0.4 m outside the contour line, and the outer row is offset 0.5 m to the side of the main blast zone 6, and staggered 0.4 m along the strike.

[0078] Unloaded anti-cracking holes 5 are located at the lower end of each pre-cracking isolation joint 4, with 2 to 3 holes arranged along the joint direction. The diameter of the anti-cracking hole 5 is larger than that of the pre-cracking hole, preferably not less than 1.5 times the diameter of the pre-cracking hole; the hole depth exceeds the bottom of the joint by 0.5 to 1.0 m, for example, 0.5 m, 0.8 m, or 1.0 m, and the hole section exceeding the bottom of the joint constitutes an ultra-deep section; the distance between adjacent anti-cracking holes 5 is not greater than 0.5 times the distance between pre-cracking holes.

[0079] The pore forms a free surface in front of the fracture tip. After the fracture tip extends to the pore wall, the stress concentration is blunted by the curvature of the pore, and the fracture terminates in the pore and no longer extends to the lower layers of rock.

[0080] When constructing the pre-cracked holes in the next layer, the drilling rig aligns the opening of the crack arresting hole 5 with the hole, and the drilling tool guides the drilling along the already formed hole section in the ultra-deep section, with the coaxiality deviation controlled within 3cm; the ultra-deep section is the opening guide section for the lower layer pre-cracked holes, so that the pre-cracked isolation joints 4 of the upper and lower layers are forced to be collinear at the position of the crack arresting hole 5.

[0081] The lower-layer pre-splitting holes located between adjacent anti-splitting holes 5 are laid out by interpolating the hole positions in a straight line connecting the two anti-splitting holes 5 at both ends, ensuring a smooth connection between the upper and lower layers of the joint surface. The anti-splitting holes 5 thus serve two functions: they prevent the joint tip from extending across layers, and they also act as guide holes for the lower-layer pre-splitting holes to participate in the next cycle of joint formation, allowing the pre-splitting isolation joint 4 to extend layer by layer as the excavation proceeds.

[0082] Example 3

[0083] This embodiment, based on Embodiment 1, explains the method for determining the transmission coefficient through the seam and the rules for judging the number of seams.

[0084] Transmission coefficient through the slit Determine by the following formula: In the formula, The equivalent opening width of the pre-cracked isolation joint 4 is in mm; For reference width, take 10mm; The transmission attenuation coefficient has an initial value ranging from 0.6 to 1.2, such as 0.6, 0.8, or 1.2, and is subsequently updated by regression from measured data.

[0085] The equivalent opening width is obtained by sampling and measuring along the seam using a borehole inspection instrument to obtain the average value; when the seam surface is locally filled with debris, the equivalent width is calculated according to the sound wave attenuation ratio through the seam. In other embodiments, the transmission coefficient through the seam can also be determined directly by the measured vibration velocity ratio of paired measuring points on both the inner and outer sides of the seam, without considering the opening width.

[0086] For fracture segments where the measured opening width dispersion by the trocar exceeds 40% due to fault fracture zones or similar conditions, this segment... A conservative value of 1.0 is forced, meaning that the attenuation benefit of the seam is not considered, and the vibration velocity measurement points are increased by 10.

[0087] Number of seams The judgment rules are as follows Figure 2 As shown: A horizontal projection is made on the excavation plane connecting the blast center and the protected object. The number of intersections between this horizontal projection and the direction lines of each pre-splitting isolation joint 4 is counted as the number of crossings. Intersections located on the extension lines beyond the crack-stopping holes 5 at both ends of the pre-splitting isolation joint 4 are not counted. Inner and outer row joints are counted separately. When the connecting line crosses both rows of joints sequentially... When the elevation of the bursting core is lower than the bottom elevation of the pre-cracked isolation joint 4 in that section, a vertical section check is performed, and lines that pass through the projection of the joint surface below the bottom elevation are not counted.

[0088] Example 4

[0089] This embodiment, based on Embodiment 1, illustrates the graded control of permissible vibration velocity of the concrete object being protected.

[0090] The permissible vibration velocity of a protected object that is a concrete structure It is continuously determined by the following formula, which is linked to the age-related intensity growth curve: In the formula, The concrete age is expressed in days (d). The allowable vibration velocity at 28 days of age is determined according to the importance of the structure. For the rock wall crane beam 9, the value range is 4 to 6 cm / s, for example, 4 cm / s, 5 cm / s, or 6 cm / s can be used. , For ordinary Portland cement, the strength growth curve coefficient can be taken as... , When adding fly ash The value range is 6 to 9, for example, it can be 6, 8, or 9; It is the vibration velocity-intensity sensitivity index, with a value range of 0.6 to 1.0, for example, 0.6, 0.8, and 1.0.

[0091] The above formula can be used to generate a hierarchical control quick reference table. In a specific example, take... cm / s , , Take a conservative value based on the lower limit of the age range:

[0092] An age of less than 1 day is a prohibited explosion window;

[0093] For periods of 1 to 3 days, the permissible vibration velocity is no greater than 1.4 cm / s;

[0094] 3–7 days, not exceeding 2.7 cm / s;

[0095] 7–28 days, not exceeding 3.8 cm / s;

[0096] More than 28 days, not greater than 5.0 cm / s.

[0097] In actual inversion, the real-time age value is obtained using a continuous function. Periods with ages below a preset lower limit are designated as no-explosion windows. Blasting plans and concrete pouring plans are scheduled in conjunction with these no-explosion windows to ensure that pouring occurs during periods of high-intensity blasting. In other embodiments, a continuous function can be omitted, and stepped segmented limits can be set according to age intervals. The number of segments and the limit for each segment are calculated using the formula above, taking the lower limit age of each interval.

[0098] Example 5

[0099] This embodiment, based on Embodiment 1, illustrates the recursive updating of vibration velocity prediction model parameters and the pairing and identification of measurement points, corresponding to... Figure 4 Closed-loop control data flow.

[0100] After introducing the through-slit transmission coefficient, , , The three parameters cannot be based on empirical values, and a single blasting cycle can only obtain data from a few measurement points. Refitting cycle by cycle would result in severe oscillations due to the small sample size. Therefore, taking the logarithm of the vibration velocity prediction formula yields a linear form: ,by For the parameter vector, use a forgetting factor The recursive weighted least squares method is updated iteratively. The value range is 0.90 to 0.98. For example, it can be 0.90, 0.95, or 0.98, so that the weight of recent cyclic data is large and the weight of early data decays exponentially, which can adapt to the gradual change of surrounding rock conditions along the elevation.

[0101] The parameter update process is equipped with a triple stabilization mechanism.

[0102] One is the limit: when the parameter update amount of a single excavation cycle exceeds the preset limit, it is truncated. The limit can be set to... , , .

[0103] Secondly, there is hysteresis: updates are not triggered when the predicted residuals of all measuring points in the excavation cycle fall within the preset threshold band, thus avoiding parameter drift in measurement noise. The threshold band range is ±10% to ±20%, for example, ±10%, ±15%, and ±20%.

[0104] Thirdly, anomaly removal: when the residual of a single measuring point exceeds the discrete criterion of the residuals of all measuring points, it is judged as an abnormal measuring point (such as sensor detachment, near-field flying stone interference), and is removed before regression; the discrete criterion can be three times the standard deviation of the mean of the residuals of all measuring points.

[0105] In other embodiments, recursive weighted least squares can also be replaced by sliding window least squares, with the window length being the most recent 5 to 10 excavation cycles.

[0106] Vibration velocity measuring points 10 are arranged and paired as follows: the measuring points on the rock mass side are arranged on the sidewall of the pre-splitting isolation joint 4, and the measuring points on the concrete structure are arranged on the top surface of the structure near the blast source.

[0107] Within the same excavation cycle, the propagation path will not cross the measuring points of pre-cracked isolation joint 4. The path) and the propagation path pass through at least one pre-cracked isolation joint 4 measuring point ( (Path) pairing, separating and identifying the slit transmission coefficient from other model parameters, avoiding and , coupling.

[0108] In a specific inversion example, the initial values ​​of the model parameters are obtained from the regression of the first three cycles of test explosions. , ,Pick The equivalent opening width of the peephole was sampled. mm, get .

[0109] Object 1 is the surrounding rock with a supported sidewall, with an allowable vibration velocity of 10 cm / s. m, The inversion yielded an allowable single-effect charge of approximately 30 kg;

[0110] Object 2 is a 9-day-old concrete crane beam on a rock wall. According to the continuity function in Example 4, the allowable vibration velocity is approximately 4.0 cm / s. m, The inversion yields approximately 480 kg. Take the smaller value. kg, controlling the amount of detonating charge within any 50ms time window;

[0111] In this cycle of sequential detonation, a maximum of 8 holes can be detonated within any 50ms window, totaling 28.8kg, which satisfies the constraints.

[0112] In this example, the parameters are updated 4 times in the first 5 cycles. Starting from the 6th cycle, the residuals of all measurement points enter the threshold band, the hysteresis mechanism stops the update, and the model enters the stable phase.

[0113] Example 6

[0114] This embodiment, based on Embodiment 1, illustrates the adjustment of the pre-splitting hole linear charge density and the decoupling coefficient of the peripheral holes in smooth blasting with the depth of layering.

[0115] As the excavation face descends, the initial ground stress at the sidewall increases. The normal stress perpendicular to the pre-splitting surface tightens the joint surface and inhibits crack penetration. Fixed-value charges at deeper layers may result in incomplete pre-crack penetration and under-excavation of the blasted surface. Therefore, the linear charge density of the pre-splitting holes... Determine by the following formula: In the formula, This is the baseline charge density for the shallow lithology layer; The initial in-situ stress perpendicular to the pre-splitting surface at the current stratification depth is obtained by interpolation from measured in-situ stress data; This represents the saturated tensile strength of the rock. This is the geostress influence coefficient, with a value ranging from 0.4 to 1.0, for example, it can be 0.4, 0.6, or 1.0.

[0116] In a specific example, at the current layer depth =7.8MPa, =6.2MPa, take =300g / m³ =0.6, therefore g / m, using φ32mm explosive cartridges tied at intervals to the detonating cord for loading, and the 1.0m unloaded section at the orifice is blocked.

[0117] Decoupling coefficient of peripheral holes in smooth blasting The ratio of borehole diameter to propellant cartridge diameter is adjusted according to the stratification depth using the following formula: In the formula, This is the first-layer decoupling coefficient, with a value range of 2.0 to 2.5, for example, it can be 2.0, 2.1, or 2.5; This represents the depth of the current layer's bottom surface from the top of the side wall; This represents the total height of the sidewalls; This is the gradient coefficient, with a value range of 0.3 to 0.6, for example, 0.3, 0.4, and 0.6.

[0118] To increase borehole wall pressure and compensate for the clamping effect of in-situ stress on the fracture surface, the decoupling coefficient should be appropriately reduced at deeper depths. The value should be no less than 1.5 to ensure that no crushing rings are formed on the borehole wall.

[0119] In a specific example (Aperture 42mm, cartridge φ20mm) =0.4, 6th floor hour .

[0120] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0121] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above invention, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A method for co-excavation of high sidewalls in underground powerhouses using layered pre-splitting and smooth blasting, characterized in that, Includes the following steps: S1. Divide the sidewall excavation area into layers along the height and into partitions along the plane. Each layer is divided into a main blasting zone (6) and a contour protection layer (8). The contour protection layer (8) is close to the sidewall design contour line (1). Adjacent partitions maintain a staggered excavation sequence. S2. Drill pre-splitting holes outside the design outline (1) of the side wall. The pre-splitting holes are drilled ahead of the current main blasting layer (11) and detonated before the main blasting zone (6) to form a pre-splitting isolation joint (4). Unfilled anti-cracking holes (5) are drilled at the lower end of the pre-cracked isolation joint (4) along the joint direction. S3. Establish a vibration velocity prediction model containing the transmission coefficient through the gap, invert the allowable single-shot charge amount according to the allowable vibration velocity of each protected object, and determine the main blasting zone (6) charge by the minimum value among the allowable single-shot charges. S4. After the main blasting zone (6) is detonated, the outline protection layer (8) is subjected to smooth blasting trimming. S5. Measure the particle velocity at each protected object, update the parameters of the velocity prediction model, and use it for the inversion of the allowable single-effect charge in the next excavation cycle.

2. The method for combined excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting as described in claim 1, is characterized in that... The pre-cracked holes are arranged in two rows, including an inner row of pre-cracked holes (2) and an outer row of pre-cracked holes (3). The inner pre-cracked holes (2) are arranged along the design outline (1) of the side wall; The outer pre-splitting hole (3) is offset relative to the inner pre-splitting hole (2) towards the main blasting zone (6); The positions of the inner row of pre-cracked holes (2) and the outer row of pre-cracked holes (3) are staggered along the direction of the crack and are arranged in a staggered manner.

3. The method for combined excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting as described in claim 1, is characterized in that... The diameter of the anti-crack hole (5) is larger than the diameter of the pre-crack hole, the depth of the anti-crack hole (5) exceeds the bottom of the pre-crack isolation joint (4), and the hole segment exceeding the bottom of the joint constitutes an ultra-deep segment. The opening of the anti-crack hole (5) is centered to form the pre-crack hole of the next layer, and is drilled axially along the ultra-deep section so that the pre-crack isolation joints (4) of the upper and lower adjacent layers are collinear at the position of the anti-crack hole (5).

4. The method for combined excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting as described in claim 1, characterized in that, Adjacent zones should maintain a vertical stagger of at least one layer, and the blasting interval between adjacent zones at the same elevation should be no less than one support follow-up cycle.

5. The method for combined excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting as described in claim 1, characterized in that, Protected object The vibration velocity prediction model is as follows: In the formula, For a single-effect dose, From the center of the explosion to the protected object distance, For site coefficient, The decay exponent, The transmission coefficient through the slit is... From the center of the explosion to the protected object The number of times the propagation path crosses the pre-cracked isolation joint (4); The transmission coefficient through the gap Determine by the following formula: In the formula, The equivalent opening width of the pre-cracked isolation joint (4) is... For reference width, is the transmission attenuation coefficient.

6. The method for combined excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting as described in claim 1, characterized in that, When the inversion allows for a single explosive charge, the number of times the propagation path from the detonation center to the protected object crosses the pre-splitting isolation joint (4) is included, and the number of times is determined according to the following rules: Make a horizontal projection of the line connecting the blast center and the protected object on the excavation plane. The number of intersections between this horizontal projection and the direction line of each pre-splitting isolation joint (4) is counted as the number of crossings. Among them, the intersection point is not counted when it is located on the extension line outside the crack-stopping holes (5) at both ends of the pre-cracked isolation joint (4); When the core elevation is lower than the bottom elevation of the pre-cracked isolation joint (4) in that section, a vertical section check is performed, and the line that passes through the projection of the joint surface below the bottom elevation is not counted.

7. The method for combined excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting as described in claim 1, characterized in that, The protected object is a concrete structure, and its allowable vibration velocity is... Determine the concrete age according to the following formula: In the formula, The age of the concrete. The permissible vibration velocity for a 28-day-old age. , The coefficient of the intensity growth curve. The vibration velocity-intensity sensitivity index is used; periods when the age is below the preset lower limit are designated as explosion-proof windows.

8. The method for combined excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting as described in claim 1, characterized in that, In S5, vibration velocity measurement points (10) are set up at each protected object. The logarithm of the vibration velocity prediction model is taken to obtain a linear form. The parameters of the vibration velocity prediction model are updated cyclically using the recursive weighted least squares method with a forgetting factor. During parameter updates, the parameter update amount of a single excavation cycle is truncated when it exceeds the preset limit. No update is triggered when the prediction residuals of all measuring points in the excavation cycle fall within the preset threshold range. When the residual of a single measuring point exceeds the discrete criterion of the residuals of all measuring points, it is judged as an abnormal measuring point that needs to be removed. Within the same excavation cycle, the measuring points whose propagation path does not cross the pre-cracked isolation joint (4) are paired with the measuring points whose propagation path crosses at least one pre-cracked isolation joint (4) to separate and identify the transmission coefficient through the joint and the remaining parameters of the vibration velocity prediction model.

9. The method for coordinated excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting as described in claim 1, characterized in that, The linear charge density of the pre-cracked hole Determine by the following formula: In the formula, Baseline charge density, This represents the initial in-situ stress perpendicular to the pre-splitting surface at the current stratification depth. For the tensile strength of rock, This is the influence coefficient of geostress; Decoupling coefficient of peripheral holes in smooth blasting Adjust according to the layer depth using the following formula: In the formula, The first-layer decoupling coefficient. This represents the depth of the current layer's bottom surface from the top of the sidewall. This represents the total height of the sidewalls. These are the gradient coefficients.

10. The method for coordinated excavation of high sidewalls of underground powerhouses using layered pre-splitting and smooth blasting as described in claim 1, characterized in that, The pre-splitting holes and the crack-stopping holes (5) are constructed by tracked down-the-hole drills, the main blasting holes in the main blasting zone (6) are constructed by rock drilling rigs, and the smooth blasting trimming holes are constructed by hand drills. The three types of drilling rigs operate in parallel with spatial misalignment, following the pre-splitting advance layer, the main blasting current layer, and the light blasting delayed trimming layer.

Images