Cutting-free drilling and blasting excavation method for cavern under complex geological conditions

Abstract

The invention relates to the technical field of cavern excavation engineering, and discloses a cutting-free drilling and blasting excavation method for a cavern under a complex geological condition, which comprises the following steps: surveying and classifying surrounding rock of a tunnel face of the cavern, pre-designing blast hole parameters, arranging a pre-splitting hole between a caving hole and a peripheral hole, and adopting non-coupling charging; the caving holes are filled with explosives at intervals, the explosives are independently packaged, and composite stemming is arranged between sections; detonating according to the sequence of first detonating of the pre-split holes, layered same-section detonating of the caving holes and final detonating of the peripheral holes; monitoring equipment is arranged to collect data, a mapping model is constructed to adjust parameters, and optimization report updating parameters are formed every preset cycle; detecting the depth of the pre-crack for re-drilling, and monitoring the displacement overrun support of the surrounding rock; according to the method, the problems of low efficiency, large disturbance and poor adaptation of traditional slotting are solved through a pre-splitting control domain, layered caving and a dynamic feedback system, and the defects of existing slotting-free technical parameters and dynamic adjustment are overcome.

Description

Technical Field

[0001] This invention relates to the field of tunnel excavation engineering technology, specifically to a non-slotted drilling and blasting excavation method for tunnels under complex geological conditions. Background Technology

[0002] Traditional tunnel excavation relies on cut-out blasting, which requires first creating a second free face through cut-out holes before proceeding with blasting of collapse holes and surrounding holes. However, this method has significant drawbacks under complex geological conditions: First, the cut-out holes are densely arranged (e.g., a wedge cut requires 6-7 holes), resulting in a large drilling workload. Furthermore, the cut-out effect is significantly affected by the heterogeneity of the surrounding rock, easily leading to low overall blasting efficiency due to cut-out failures, with hole utilization often below 90%. Second, the explosive consumption is high, and the blast shock is intense. Class III-V surrounding rock is prone to crack expansion and collapse after blasting disturbance, making over- and under-excavation control difficult (over-excavation often exceeds 50mm). Third, blasting parameters largely rely on experience-based design and cannot be dynamically adjusted based on real-time excavation feedback, resulting in poor flexibility in adapting to complex geological conditions.

[0003] However, while existing non-cutting blasting technologies eliminate the need for cut holes, they are mostly applicable to single homogeneous surrounding rocks. They have not formed a parameter system and dynamic optimization mechanism for complex geological conditions, and their control precision over the borehole charge structure and detonation sequence is insufficient, making it difficult to balance excavation efficiency and surrounding rock stability. Summary of the Invention

[0004] To address complex geological conditions, this invention provides a non-cutting drill-blast excavation method for caverns under such conditions. This method solves the problems of low efficiency, large disturbance, and poor adaptability of traditional cutting processes in complex geological conditions through a technical system of pre-splitting control, layered collapse, and dynamic feedback. At the same time, it makes up for the lack of parameter system and dynamic adjustment defects in existing non-cutting technologies.

[0005] This invention is achieved through the following technical solution: A non-cutting drill-blast excavation method for caverns under complex geological conditions includes the following steps: Step 1: Conduct geological surveys of the tunnel face, classify the surrounding rock within the face, and pre-design borehole parameters based on the geological categories. The borehole parameters include at least the borehole diameter, borehole depth, spacing between collapse holes, number of segments, charge per segment, and plugging length. Simultaneously, pre-splitting holes are set between the collapse holes and the surrounding holes, and the pre-splitting holes adopt a non-coupled charge structure. Step 2: The collapse hole adopts an intermittent charging structure, with each section of explosive independently encapsulated and containing a detonating element, and composite stemming material is set between adjacent sections; Step 3: Detonate the pre-splitting holes first, the collapse holes in layers in the same section, and the peripheral holes last. The pre-splitting holes are detonated before the collapse holes by a preset time to form pre-splitting cracks. Collapse holes in the same layer are detonated simultaneously. The interlayer delay time is determined according to the rock block movement characteristics. The peripheral holes are detonated after the last layer of collapse holes by a preset time, and the charge is lower than that of the collapse holes. Step 4: Install monitoring equipment in the tunnel and at the working face to collect strain data, rock movement data and excavation contour data during the blasting process; establish a mapping model based on the monitoring data to adjust the borehole parameters and detonation sequence; generate a parameter optimization report after each preset number of cycles to update the pre-design parameters; Step 5: Detect the depth of the pre-crack after the pre-splitting hole is blasted. If the depth does not meet the standard, drill additional holes. Also, monitor the displacement of the surrounding rock after blasting and provide support if the displacement exceeds the limit.

[0006] This scheme constructs a complete closed-loop system in stages, encompassing geological adaptation, structural optimization, timing control, dynamic feedback, and safety assurance. This ultimately achieves trenchless drilling and blasting excavation of caverns under complex geological conditions. Specifically, by eliminating cut holes and precisely pre-designing borehole parameters based on geological categories, drilling workload is significantly reduced. Simultaneously, pre-splitting holes create pre-fractures, providing a favorable free surface for blasting in the collapse holes. Combined with layered, simultaneous initiation of collapse holes and precise control of surrounding holes, this effectively avoids the low blasting efficiency problem caused by failed cut holes in traditional methods, significantly improving borehole utilization. Regarding surrounding rock protection, the decoupled charge structure of the pre-splitting holes weakens the impact of blast waves on the surrounding rock. The spaced charges and composite blasting in the collapse holes further enhance the protection. The mud design reduces the intensity of concentrated explosive action, minimizing the risk of fracture propagation and collapse in complex surrounding rock of grades III to V after blasting. Simultaneously, it collects real-time data on strain, rock movement, and excavation contour through monitoring equipment, dynamically adjusting parameters using a mapping model to precisely control over- and under-excavation, ensuring the accuracy of the tunnel excavation contour and the stability of the surrounding rock. Furthermore, it differentiates the charge structure, detonation sequence, and monitoring scheme for different geological types, continuously updating pre-design parameters through parameter optimization reports generated after each preset number of cycles. This breaks the limitations of traditional blasting parameters relying on experience, significantly improving the flexibility of adapting to complex geological conditions. Additionally, it further mitigates construction safety risks through pre-crack depth detection and supplementary drilling, as well as support for excessive surrounding rock displacement.

[0007] In a further embodiment, in step 1, the geological categories include heterogeneous surrounding rock, jointed and fractured surrounding rock, and soft / high-gas surrounding rock. This achieves precise matching between geological conditions and excavation parameters, avoiding the poor adaptability problem caused by the one-size-fits-all approach to parameters in traditional processes. This provides a scientific basis for the parameter design of subsequent stages. Furthermore, the spacing between the pre-splitting holes is 12 to 15 times the diameter of the borehole, the decoupling coefficient of the uncoupled charge is 1.8 to 2.2, and the charge amount is 1 / 3 to 1 / 2 of that of the collapse hole. The explosive is a low-detonation-velocity explosive, which ensures that the pre-splitting hole blasting can form continuous pre-cracks of appropriate width, effectively blocking the propagation of the blast wave generated by the collapse hole blasting to the surrounding surrounding rock, reducing disturbance to the complex surrounding rock of grades III to V, and reducing the risk of crack propagation and collapse. At the same time, by reasonably controlling the charge amount and detonation velocity of the pre-splitting holes, excessive pre-splitting can be avoided to prevent damage to the integrity of the surrounding rock.

[0008] In a further embodiment, in step 2, the spaced-out charge structure is a sequentially filled structure of stemming clay, explosive, and stemming clay. This avoids the concentrated distribution of explosive within the borehole, reduces excessive impact in localized areas during blasting, and minimizes disturbance to the surrounding rock. Simultaneously, the stemming clay extends the contact time of the explosive gases within the borehole, ensuring that the explosive energy is more fully utilized for rock breaking, thus improving borehole utilization and rock-breaking efficiency. Furthermore, the composite stemming clay is a combination of yellow clay and water-based stemming clay, with water-based clay comprising 30%–50%. The composite stemming clay has a compressive strength ≥1.5 MPa and a radial expansion rate ≥5%, further ensuring that the stemming clay is not easily broken under blasting impact and can continuously perform its sealing function.

[0009] In a further embodiment, in step 2, when the geological type is high-gas geology, each section of explosive is coated with an aluminum hydroxide composite flame-retardant and explosion-proof coating, and a gas monitoring sensor is installed at the bottom of the blast hole. When the real-time gas concentration is >0.8%, an alarm is triggered and the detonation is stopped. This not only ensures the construction efficiency of trenchless drilling and blasting excavation under high-gas geology, but also significantly reduces safety risks, solving the problem of balancing excavation efficiency and safety under complex high-gas geological conditions.

[0010] In a further embodiment, in step 3, the preset time for the pre-splitting hole to precede the collapse hole is 50–80 ms, and the pre-splitting crack width is ≥2 mm. This ensures that continuous and sufficiently wide pre-splitting cracks are formed before the collapse hole blasting, effectively blocking the propagation of the blast wave generated by the collapse blasting to the surrounding rock. The interlayer delay time is determined by the formula... +20 is calculated and determined, where L is the inter-story distance. To control the movement speed of the rock blocks, the detonation interval can be precisely matched according to the movement characteristics of the rock blocks under different geological conditions, ensuring that the previous layer of rock blocks is fully ejected before the subsequent layer is blasted, avoiding the problem of low blasting efficiency or over-excavation caused by the mutual compression of rock blocks between layers, and improving the utilization rate of blast holes; the charge amount of the peripheral holes is 1 / 4 to 1 / 3 of that of the collapse holes, and continuous charge is adopted at the bottom of the hole to ensure the precise trimming of the excavation outline during the blasting of peripheral holes, reducing the amount of over-excavation and under-excavation.

[0011] In a further scheme, comprehensive and precise technical support is provided for the dynamic monitoring and parameter optimization of the entire process of trenchless drilling and blasting excavation under complex geological conditions. In step 4, the monitoring equipment includes a strain monitoring device, an image monitoring device, and a contour monitoring device. The strain monitoring device is arranged bidirectionally along the longitudinal and transverse directions of the tunnel to form a three-dimensional strain monitoring network, which is used to collect the strain peak value at different locations of the surrounding rock. The image monitoring device is deployed on the non-blasting impact direction on the side of the tunnel to record the trajectory of rock blocks and the pre-crack penetration status. The contour monitoring device is located behind the working face after blasting to scan the excavation contour.

[0012] In a further embodiment, in step 4, the mapping model is constructed based on fuzzy multivariate analysis. When the strain peak exceeds the standard, the single-segment charge amount or the spacing between collapse holes is adjusted; when the rock block throwing distance does not meet the standard, the interlayer delay time or the bottom charge amount is adjusted; when the over-excavation exceeds the standard, the spacing between surrounding holes or the charge amount is adjusted. In this way, the parameters can be continuously optimized according to the real-time changes of complex geological conditions, ensuring a dynamic balance between excavation efficiency, surrounding rock stability and contour accuracy, and significantly improving the adaptability and reliability of the no-trap drilling and blasting technology in complex geology.

[0013] In a further embodiment, in step 4, the preset number of cycles is 3 to 5 times, and the parameter optimization report includes at least a summary of monitoring data, the basis for parameter adjustment, the adjusted parameter values, and an evaluation of expected effects. This is used to guide subsequent drilling and blasting operations, provide a traceable reference for parameter reuse and optimization in different complex geological sections, and ensure that subsequent drilling and blasting operations can continuously adapt to changes in geological conditions.

[0014] In a further scheme, in step 4, the parameter optimization rules are as follows: when the over- or under-excavation exceeds 50mm, reduce the hole spacing in the corresponding area by 5% to 8%, optimize the hole layout for areas with excavation contour deviation, reduce insufficient rock fragmentation or over-excavation caused by excessive hole spacing, and improve the accuracy of the excavation contour; when the vibration exceeds the standard, reduce the single-section charge by 10% to 15% to avoid the risk of crack expansion or collapse in Class III to V complex surrounding rock due to excessive vibration, and ensure the stability of the surrounding rock; when the hole trace rate is less than 90%, adjust the peripheral hole spacing by 5%, which can optimize the smooth surface effect of peripheral hole blasting, ensure the integrity of the surrounding rock surface after excavation, and reduce the cost and difficulty of subsequent support.

[0015] In a further embodiment, in step 5, the pre-crack depth must be ≥ 90% of the hole depth; the surrounding rock displacement monitoring adopts a multi-point displacement meter, and the support method includes a combination of shotcrete and anchor bolt support, thereby effectively controlling the deformation of the surrounding rock, improving the overall stability of the cavern, especially suitable for the characteristics of easy collapse of complex surrounding rock of grades III to V, ensuring the long-term stability of the cavern after trenchless drilling and blasting excavation, and reducing the later maintenance costs and safety risks.

[0016] Compared with the prior art, the present invention has the following main advantages and beneficial effects: This invention effectively avoids three core defects of traditional processes by eliminating cut holes and constructing a technical system of pre-splitting control, layered collapse, and dynamic feedback: First, it eliminates the need for densely arranged cut holes, significantly reducing drilling workload and avoiding cut failures caused by heterogeneous surrounding rock, thereby increasing borehole utilization to a higher level and significantly reducing the risk of low overall blasting efficiency; Second, by using pre-splitting holes to form pre-cracks in advance to block blasting waves and using intermittent charging of explosives in collapse holes to control explosive energy release, it solves the problems of high explosive consumption and strong blasting in traditional processes, effectively reducing the risk of crack expansion and collapse in Class III-V surrounding rock after blasting disturbance, and significantly reducing the difficulty of over- and under-excavation control; Third, it breaks through the limitations of traditional processes that rely on experience-based blasting parameter design, and achieves flexible adaptation to complex geological conditions through a mechanism of adapting pre-design parameters to geological classification and dynamically adjusting parameters through feedback, no longer limited by a single geological condition. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram illustrating the implementation process of the present invention; Figure 2 This is a schematic diagram of the borehole arrangement of the present invention; Figure 3 This is a schematic diagram of the slotless blasting charge structure of the present invention.

[0018] The attached diagram shows the markings and corresponding component names: 1-Peripheral hole, 2-Cavitation hole. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0020] Example This embodiment needs to solve three major problems: blasting disturbance and collapse in soft rock sections, safety and explosion prevention in high gas areas, and over-excavation and under-excavation control in heterogeneous surrounding rock. In this scenario, the traditional slotting process (wedge slotting requires 6 slotting holes) has a hole utilization rate of only 85% and the over-excavation amount often reaches 55mm, which cannot meet the engineering requirements.

[0021] To meet engineering requirements, this embodiment provides a non-cutting drill-blast excavation method for caverns under complex geological conditions, such as... Figures 1-3 As shown, this embodiment employs the following steps: Step 1: Conduct geological surveys of the tunnel face, classify the surrounding rock within the face, and pre-design borehole parameters based on the geological categories. The borehole parameters should include at least the borehole diameter, borehole depth, spacing of collapse holes 2, number of segments, charge per segment, and plugging length. At the same time, pre-splitting holes should be set between collapse holes 2 and surrounding holes 1. The pre-splitting holes should adopt a non-coupled charge structure. Specifically, the aforementioned geological exploration can employ a combination of drilling core samples, acoustic testing, and ground-penetrating radar to ensure a comprehensive understanding of the geological characteristics of the working face. Based on the exploration data, borehole parameters are pre-designed following the principle of geological adaptation, as shown in Table 1. Table 1. Hole Parameters ; To ensure the effectiveness of pre-splitting control, in some embodiments, pre-splitting holes are arranged along the boundary line between the collapse hole 2 and the surrounding holes 1, 200-250mm from the collapse hole and 150-200mm from the surrounding holes, with a hole position deviation of ≤30mm, and the hole depth is consistent with that of the collapse hole 2 (to avoid a step at the bottom of the hole); wherein, the decoupled charge structure uses low-detonation-velocity explosive (detonation velocity ≤3500m / s), the diameter of the charge cartridge is 1 / 1.8 to 1 / 2.2 of the diameter of the borehole (decoupling coefficient 1.8 to 2.2), an air-gap charging method is adopted (a uniform air gap is reserved between the charge cartridge and the hole wall), the charge amount is 1 / 3 to 1 / 2 of the charge amount of the corresponding area collapse hole, and the charge length is 80% of the hole depth (a 20% empty hole is reserved at the bottom of the hole to avoid over-explosion at the bottom of the hole).

[0022] Step 2: The caving hole adopts an intermittent charging structure, with each section of explosive independently encapsulated and containing a detonating element, and composite stemming material is placed between adjacent sections; Specifically, firstly, the selected explosives must match the geological category (e.g., No. 2 rock emulsion explosive for Class B geology, and coal mine-permitted water-gel explosive for Class C high-gas geology). The detonating element uses a coal mine-permitted millisecond electric detonator (segment error ≤ 5ms). The composite gunning clay is prepared by combining yellow clay and water gunning clay, with water gunning clay accounting for 30%–50%, and the yellow clay needing to control the moisture content to 15%–20% to ensure plasticity. After preparation, the performance of the composite gunning clay needs to be tested to ensure its compressive strength ≥ 1.5MPa and radial expansion rate ≥ 5%, meeting the inter-segment sealing requirements of the interval charge. If the geological category is high-gas geology, an aluminum hydroxide composite flame-retardant and explosion-proof coating (thickness ≥ 2mm) and a gas monitoring sensor (response time ≤ 10s, measurement range 0–1.0% CH4) also need to be prepared for explosive explosion protection and real-time gas monitoring.

[0023] Then, the explosives are processed according to the independent encapsulation requirements for each section: PVC pipes (with a diameter slightly smaller than the borehole diameter, e.g., a PVC pipe diameter of 38mm when the borehole diameter is 42mm, and a wall thickness of 1-2mm) are used as the encapsulation carrier. After each section of explosive is loaded into the PVC pipe, one permissible millisecond electric detonator for coal mines is placed in the center of the pipe. The detonator lead must be straightened and extend beyond the PVC pipe (length ≥300mm, for easy connection to the subsequent detonation network). Both ends of the PVC pipe are sealed with yellow mud (50mm thick) to ensure no gap between the explosive and the pipe wall and to fix the position of the detonating element, preventing detonation failure due to displacement during loading. For high-gas geological conditions, an aluminum hydroxide composite flame-retardant and explosion-proof coating must be evenly coated on the outside of the encapsulated PVC pipe. The coating thickness must reach 2mm after drying to form an explosion-proof isolation layer, preventing direct contact between the explosive and the gas. Then, a layer-by-layer filling and segmented positioning method is used for interval charging: First, the first section of stemming clay (100-120mm in length) is filled into the bottom of the collapse hole, ensuring that the stemming clay is dense and without gaps; then, the sealed independent explosive section is slowly placed into the hole, with the bottom of the explosive section in close contact with the stemming clay to avoid voids at the bottom of the hole; next, the second section of composite stemming clay (100-150mm in length) is filled on top of the explosive section, and it needs to be compacted in layers to ensure that the stemming clay is fully adhered to the hole wall and the explosive section; this process of stemming clay, explosive, and stemming clay is repeated until all segmented charging is completed. Finally, sealing stemming clay is filled at the hole opening (length ≥ design value of the sealing length, such as 350mm length of sealing stemming clay for a hole depth of 2.0m in Class C geology), forming a complete interval charging structure. During the charging process, the position of each segment needs to be measured with a measuring rope to ensure that the deviation of the inter-segment spacing is ≤20mm, to avoid insufficient local explosive force or over-explosion due to uneven charging.

[0024] If the construction area is a high-gas geological area, after the interval charging is completed, a gas monitoring sensor needs to be installed at the bottom of the collapse hole (200mm from the bottom of the hole). The sensor probe needs to be close to the hole wall and connected to the explosion-proof control cabinet at the working face through an explosion-proof wire. A monitoring threshold is set (an alarm is triggered and the detonation power is cut off when the gas concentration is >0.8%) to ensure real-time monitoring of the gas concentration change in the hole after charging.

[0025] Step 3: Detonate the pre-splitting holes first, the collapse holes in layers in the same section, and the peripheral holes last. The pre-splitting holes are detonated before the collapse holes by a preset time to form pre-splitting cracks. Collapse holes in the same layer are detonated simultaneously. The interlayer delay time is determined according to the rock block movement characteristics. The peripheral holes are detonated after the last layer of collapse holes by a preset time, and the charge is lower than that of the collapse holes. Specifically, the compatibility of the detonating equipment is first confirmed according to the geological category. For example, for Category B, No. 2 rock emulsion explosive is used with MS1-5 millisecond electric detonators, and for Category C, coal mine permissible water-gel explosive is used with coal mine permissible millisecond electric detonators. It is ensured that the detonator segment error is ≤5ms, and both the explosive and the detonator meet the requirements of the "Blasting Safety Regulations". Then, a dual-circuit network structure combining series connection in the same layer and parallel connection between layers is adopted. That is, the cave-in holes in the same layer are connected in series through explosion-proof wires (to ensure simultaneous detonation in the same layer), and the cave-in holes, pre-splitting holes, and peripheral holes in different layers are connected in parallel to the detonator through the main line. After connection, the network resistance is tested with a multimeter to avoid stray current interference. For high-gas geology, the network insulation needs to be tested additionally.

[0026] Before the collapse hole is detonated, the pre-splitting hole detonation procedure is initiated. The pre-splitting hole is controlled to advance the collapse hole by 50-80ms (the specific time is adjusted according to the geology; 65ms is generally used for Class B geology and 75ms is generally used for Class C geology) to ensure that the pre-splitting hole forms an effective pre-crack before the collapse hole. After the pre-splitting holes form stable pre-cracks (detonating 50-80 ms after pre-splitting hole initiation), the caving hole initiation procedure is initiated. Caves in the same layer are detonated simultaneously through a series network to ensure uniform stress on the rock blocks within the same layer and avoid localized unbroken rock blocks remaining. The interlayer delay time is determined and implemented based on the rock block movement characteristics, specifically using the formula... +20 calculation (where L is the inter-layer distance, V) s For rock block movement velocity, Class B geological V s (Take 0.8 m / s for Class C geology and 0.9 m / s for Class B geology). For example, when the interlayer distance is 733 mm for Class B geology, the delay time is calculated to be 110 ms. During actual detonation, the interlayer delay is achieved by adjusting the detonator segments (e.g., using 2 segments for the first layer, 3 segments for the second layer, and 4 segments for the third layer) to ensure that the rock blocks in the previous layer are fully ejected ≥500 mm before the subsequent layer is detonated, thus avoiding over-excavation caused by the mutual compression of rock blocks between layers.

[0027] After the last layer of collapse holes is detonated and the rock blocks are basically stable, the detonation procedure for the peripheral holes is initiated. The preset time for the peripheral holes to lag behind the last layer of collapse holes is controlled at 100-150ms (120ms for Class B geology and 150ms for Class C geology). In this embodiment, to ensure that a sufficient free surface is formed inside the cavern during the blasting of the peripheral holes, the peripheral holes use 6-section detonators, detonating 130ms after the last layer of collapse holes. The charge is 1 / 4 of that of the collapse holes (30g for Class B and 22g for Class C). Continuous charging is used at the bottom of the holes to reduce over-excavation of the outline.

[0028] Step 4: Install monitoring equipment in the tunnel and at the working face to collect strain data, rock movement data and excavation contour data during the blasting process; establish a mapping model based on the monitoring data to adjust the borehole parameters and detonation sequence; generate a parameter optimization report after each preset number of cycles to update the pre-design parameters; Specifically, strain gauges were arranged longitudinally and laterally (100mm / 250mm from the collapse hole) at cross sections 1m and 2m behind the tunnel face, and connected to an ultra-dynamic strain meter (sampling frequency 1MHz) to collect strain peak values; a high-speed camera (15000fps) was arranged on the side of the tunnel in the non-impact direction (12m from the tunnel face) to record the trajectory of rock blocks and the penetration of pre-cracks; 1 hour after blasting, the entire cross section was scanned with a laser profiler at 1.5m behind the tunnel face to calculate the over- and under-excavation amounts.

[0029] Taking the third cycle of Category C geology as an example, the monitoring data and adjustments are as follows: when the strain peak value is 0.23 × 10⁻⁶... -3 (Exceeding the standard), the rock throwing distance is 420mm (less than 500mm), and the over-excavation is 38mm (exceeding the standard). At this time, based on the fuzzy multivariate analysis mapping model, the single-segment charge amount can be adjusted for exceeding the standard, the interlayer delay time can be adjusted for insufficient throwing, and the spacing of the surrounding holes can be adjusted for over-excavation. Specifically, the single-segment charge amount is reduced from 90g to 81g; the interlayer delay time is shortened from 95ms to 80ms; and the spacing of the surrounding holes is reduced from 350mm to 320mm.

[0030] Every three cycles, a "Parameter Optimization Report" is generated, which includes a summary of monitoring data (peak strain, over-excavation, etc.), the basis for adjustment (fuzzy multivariate analysis results), the adjusted parameters (e.g., the single-segment charge of a Class C collapse hole is stabilized at 80g), and the expected effect (peak strain ≤ 0.2 × 10⁻⁶). -3 ).

[0031] Step 5: Detect the depth of the pre-crack after the pre-splitting hole is detonated. If the depth does not meet the standard, drill additional holes. Also, monitor the displacement of the surrounding rock after blasting and provide support if the displacement exceeds the limit. Specifically, after the pre-splitting holes are detonated, the depth is first tested using an acoustic wave tester. For Class B geology, the depth is 2.05m (hole depth 2.2m, meeting the standard 93%), and for Class C geology, the depth is 1.85m (hole depth 2.0m, meeting the standard 92.5%). In areas that do not meet the standard (such as a Class C hole with a depth of 1.6m), two additional pre-splitting holes are drilled (300mm apart). Then, multi-point displacement gauges (arranged on the top and sides of the tunnel, at a depth of 3m) were used to monitor the displacement every 2 hours within 24 hours after blasting. The displacement rate for Class C geological conditions was 0.4mm / d (≤0.5mm / d threshold). If the limit was exceeded (e.g., the top displacement was 0.6mm / d at one point), immediate support was provided: shotcrete C25 concrete (100mm thick) + Φ20mm threaded steel anchor rods (2.2m long, 900mm spacing).

[0032] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for the drill and blast excavation of a cavern under complex geological conditions, characterised in that, Includes the following steps: Step 1: Conduct geological surveys of the tunnel face, classify the surrounding rock within the face, and pre-design borehole parameters based on the geological categories. The borehole parameters include at least the borehole diameter, borehole depth, spacing between collapse holes, number of segments, charge per segment, and plugging length. Simultaneously, pre-splitting holes are set between the collapse holes and the surrounding holes, and the pre-splitting holes adopt a non-coupled charge structure. Step 2: The collapse hole adopts an intermittent charging structure, with each section of explosive independently encapsulated and containing a detonating element, and composite stemming material is set between adjacent sections; Step 3: Detonate the pre-splitting holes first, the collapse holes in layers in the same section, and the peripheral holes last. The pre-splitting holes are detonated before the collapse holes by a preset time to form pre-splitting cracks. Collapse holes in the same layer are detonated simultaneously. The interlayer delay time is determined according to the rock block movement characteristics. The peripheral holes are detonated after the last layer of collapse holes by a preset time, and the charge is lower than that of the collapse holes. Step 4: Install monitoring equipment in the tunnel and at the working face to collect strain data, rock movement data and excavation contour data during the blasting process; establish a mapping model based on the monitoring data to adjust the borehole parameters and detonation sequence; generate a parameter optimization report after each preset number of cycles to update the pre-design parameters; Step 5: Detect the depth of the pre-crack after the pre-splitting hole is blasted. If the depth does not meet the standard, drill additional holes. Also, monitor the displacement of the surrounding rock after blasting and provide support if the displacement exceeds the limit.

2. A method for drill and blast excavation with free slotting for caverns in complex geological conditions according to claim 1, characterized in that, In step 1, the geological categories include homogeneous surrounding rock, jointed and fractured surrounding rock, and soft rock / high gas surrounding rock. The pre-splitting hole spacing is 12 to 15 times the borehole diameter. The decoupling coefficient of the decoupled charge is 1.8 to 2.

2. The charge amount is 1 / 3 to 1 / 2 of the collapse hole. The explosive is a low-detonation-velocity explosive.

3. A method for free slot drilling and blasting excavation of a cavern in complex geological conditions according to claim 1, characterized in that, In step 2, the spaced charge structure is a structure consisting of sequentially filled gun clay, explosive, and gun clay. The composite gun clay is a combination of yellow clay and water gun clay, wherein the water gun clay accounts for 30% to 50%, and the composite gun clay has a compressive strength ≥1.5MPa and a radial expansion rate ≥5%.

4. A method of cut-and-blast excavation without slotting for a cavern under complex geological conditions according to claim 3, characterized in that, In step 2, when the geological type is high-gas geology, each section of explosive is coated with an aluminum hydroxide composite flame-retardant and explosion-proof coating, and a gas monitoring sensor is installed at the bottom of the borehole. When the real-time gas concentration is >0.8%, an alarm is triggered and the detonation is stopped.

5. The method for trenchless drilling and blasting excavation of caverns under complex geological conditions according to claim 1, characterized in that, In the step 3, the preset time of the pre-split hole to advance the caving hole is 50-80 ms, and the pre-split crack width is greater than or equal to 2 mm; the interlayer delay time is calculated by the formula determination, wherein L is the interlayer distance, is the rock mass moving speed; the peripheral hole charge amount is 1 / 4-1 / 3 of the caving hole, and the continuous hole bottom charging is adopted.

6. The method for trenchless drilling and blasting excavation of caverns under complex geological conditions according to claim 1, characterized in that, In step 4, the monitoring equipment includes a strain monitoring device, an image monitoring device, and a contour monitoring device. The strain monitoring device is arranged bidirectionally along the longitudinal and transverse directions of the tunnel to form a three-dimensional strain monitoring network, which is used to collect the strain peak values ​​at different locations of the surrounding rock. The image monitoring device is deployed on the non-blasting impact direction on the side of the tunnel to record the trajectory of rock blocks and the penetration status of pre-cracks. The contour monitoring device is located behind the working face after blasting and is used to scan the excavation contour.

7. A method for trenchless drilling and blasting excavation of caverns under complex geological conditions according to claim 6, characterized in that, In step 4, the mapping model is constructed based on fuzzy multivariate analysis. When the strain peak exceeds the standard, the single-segment charge amount or the spacing between collapse holes is adjusted; when the rock block throwing distance does not meet the standard, the interlayer delay time or the charge amount of the bottom layer is adjusted; when the over-excavation exceeds the standard, the spacing between surrounding holes or the charge amount is adjusted.

8. A method for trenchless drilling and blasting excavation of caverns under complex geological conditions according to claim 7, characterized in that, In step 4, the preset number of cycles is 3 to 5 times, and the parameter optimization report includes at least a summary of monitoring data, the basis for parameter adjustment, the adjusted parameter values, and an evaluation of expected effects, which is used to guide subsequent drilling and blasting operations.

9. A method for trenchless drilling and blasting excavation of caverns under complex geological conditions according to claim 8, characterized in that, In step 4, the parameter optimization rules are as follows: when the over- or under-excavation amount exceeds 50mm, reduce the hole spacing in the corresponding area by 5% to 8%; when the vibration exceeds the standard, reduce the single-section charge amount by 10% to 15%; when the hole trace rate is less than 90%, adjust the surrounding hole spacing by 5%.

10. A method for trenchless drilling and blasting excavation of caverns under complex geological conditions according to claim 1, characterized in that, In step 5, the pre-crack depth must be ≥ 90% of the hole depth; the surrounding rock displacement monitoring adopts a multi-point displacement meter, and the support method includes a combination of shotcrete and anchor bolt support.

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