A shaft high water, broken ground pre-grouting and freezing combined construction method

Abstract

The present application relates to the technical field of mine construction, and provides a vertical shaft high water-rich and broken section ground pre-grouting and freezing combined construction method, which constructs a composite bearing structure of grouting reinforced layer and frozen water sealing curtain through pre-grouting and freezing, sectional grouting and special reinforcement, and reserves the position of the horsehead door in the early design and construction and specially reinforces the surrounding rock thereof, realizes seamless connection of broken surrounding rock reinforcement, aquifer plugging, shaft lining and horsehead door construction, and realizes triple promotion of quality, efficiency and safety of the vertical shaft construction of the high water-rich and broken section.

Description

Technical Field

[0001] This invention relates to the field of mining construction technology, and in particular to a combined construction method for pre-grouting and freezing of the ground surface in a vertical shaft with high water content and fractured sections. Background Technology

[0002] During the construction of vertical shafts, highly water-rich and strongly fractured strata, due to the development of rock fissures and the strong water-richness of aquifers, become the core bottleneck for construction safety and efficiency. Construction in such sections is prone to accidents such as shaft collapse and water inrush, which directly determine the progress of mine construction, production safety and operational efficiency.

[0003] In existing technologies, traditional shaft construction processes typically include single freezing, single grouting, and conventional combined processes.

[0004] However, traditional shaft construction techniques often have many problems for the above-mentioned strata. Among them, the single freezing process, which uses a one-time freezing to freeze to the bottom, makes the frozen wall susceptible to water erosion, resulting in melting and cracking. The freezing period is long, and the opening of the shaft is interfered with by the freezing pipe, resulting in a high rate of construction rectification.

[0005] The water-sealing and reinforcement effect of a single grouting process is limited, the water inflow control rate is low, the risk of surrounding rock collapse remains high, and it is difficult to meet the safety management requirements of high water-rich fractured sections.

[0006] Conventional combined processes typically involve freezing followed by grouting or a sequential grouting-freezing operation, resulting in disjointed process connections, high waiting time, insufficient resource utilization, failure to form a synergistic bearing system for grouting and freezing, and lack of specific reserved construction space for the masthead, leading to insufficient reinforcement of the surrounding rock at the masthead.

[0007] The traditional shaft construction techniques described above cannot solve the problems of construction interference at the head gate, insufficient stability of the frozen wall, long construction period, and inadequate reinforcement of the surrounding rock at the head gate. Summary of the Invention

[0008] This invention provides a combined construction method for vertical shafts with high water content, fractured ground pre-grouting and freezing, to solve the problems of construction interference at the head gate, insufficient stability of the frozen wall, long construction period and insufficient reinforcement of the surrounding rock at the head gate in the prior art.

[0009] This invention provides a method for combined construction of pre-grouting and freezing of the ground surface in a vertical shaft with high water content and fractured sections, comprising: S1. Based on the shaft engineering survey data, divide the replacement section, grouting reinforcement section and freezing construction section, and mark and reserve the construction position of the vertical shaft gate in advance; S2. Perform replacement treatment on the replacement section to form a stable construction foundation, complete the positioning and layout of grouting holes and freezing holes, and set up densified grouting holes in the Matoumen area. S3. Implement ground-retreating segmented pre-grouting operations on the grouting reinforcement section, and carry out special grouting reinforcement of the surrounding rock of Matoumen to achieve the filling of stratum fissures and sealing of aquifers; S4. After the grouting is accepted, carry out the segmented freezing operation. The freezing holes are arranged to avoid the construction area reserved by the horse head gate, forming a composite load-bearing structure with the grouting reinforcement layer superimposed on the freezing curtain. Check that all indicators of the frozen wall meet the design requirements. S5. After the frozen wall passes the acceptance inspection, the shaft excavation and lining operation shall be carried out. The excavation of the head gate shall be carried out at the reserved position of the head gate that has been specially reinforced by grouting. The excavation process shall follow the construction process of first supporting and then expanding. S6. After the permanent support construction of the well shaft is completed, the freezing operation is stopped in sections, the freezing pipe is filled and sealed, and the entire process is completed and accepted.

[0010] According to the present invention, a combined construction method for pre-grouting and freezing of ground in a vertical shaft with high water content and fractured section is provided. In step S2, the replacement treatment adopts graded sand and gravel backfilling and compaction in layers. The mud content of the replacement material is ≤3%, the loose layer thickness is not greater than 30cm, and the backfill compaction degree is ≥95%. After the replacement is completed, a 5-10cm thick cement mortar protective surface layer is set on the replacement surface.

[0011] According to the present invention, in a method for combined construction of ground pre-grouting and freezing in a vertical shaft with high water content and fractured section, in step S3, the grouting holes adopt a hole layout of annular main holes plus denser holes in the head gate area; the grouting section length of the stratum is set to 5m, and the grouting section in the head gate area is densified to 3m; the grouting holes are constructed using a dual-sequence drilling method.

[0012] According to the present invention, a method for combined construction of pre-grouting and freezing of ground in a vertical shaft with high water content and fractured section is provided. In step S3, the grouting slurry is mainly composed of ultrafine cement with a water-cement ratio of 1:1. When encountering water inrush, water glass quick-setting agent is compounded, and the volume ratio of cement slurry to water glass slurry is controlled at 1:0.5~1:1. The grouting pressure stabilization pressure in the Matoumen area is increased to 6-8MPa.

[0013] According to the present invention, in a method for combined construction of pre-grouting and freezing of ground in a vertical shaft with high water content and fractured section, the grouting end conditions for a single hole in step S3 are: after reaching the design final pressure, the pressure is stabilized for 10-15 minutes, the pressure stabilization time in the Matoumen area is extended to 15-20 minutes, and the unit grouting volume is less than 5L / min.

[0014] According to the present invention, a combined construction method for pre-grouting and freezing of ground in a vertical shaft with high water content and fractured sections is provided. In step S4, the sectional freezing is carried out segment by segment, with each segment being 30m. The brine temperature is controlled at -27℃ to -31℃ during the active freezing period and at -23℃ to -27℃ during the maintenance freezing period. The acceptance conditions for the frozen wall include complete closure of the frozen wall, sand temperature dropping below -8℃, frozen wall thickness ≥2.0m, and uniaxial compressive strength of the frozen wall around the gate ≥12MPa.

[0015] According to the present invention, a method for combined construction of ground pre-grouting and freezing of a vertical shaft with high water content and fractured section is provided. In step S5, the shaft excavation and lining adopts a short-section excavation and lining process from top to bottom, the exposed height of the surrounding rock is ≤1.5m, and the exposed time of the surrounding rock is ≤8h. During blasting operations, the distance between the blast hole and the freezing pipe is not less than 1.2m. Before blasting, the brine circulation is suspended. After the blasting is completed, the freezing pipe is checked for damage and the freezing circulation is resumed.

[0016] According to the present invention, a method for combined construction of ground pre-grouting and freezing of a vertical shaft with high water content and fractured section is provided. The entire process of steps S1-S6 is monitored in real time with multiple parameters, including the compaction degree of replacement, grouting pressure, grout absorption, freezing temperature, groundwater level, surrounding rock settlement, and well wall displacement. Monitoring points are densely deployed in the Matoumen area, and the abnormal early warning response time is ≤10min.

[0017] According to the present invention, a method for combined construction of ground pre-grouting and freezing of a vertical shaft with high water content and fractured section is provided. In step S6, freezing is stopped in a segmented shutdown mode. The inside of the freezing pipe is filled with 1:1 cement slurry with a filling density of ≥98%, which avoids the risk of well wall cracking caused by rapid melting and settling of the frozen wall.

[0018] According to the present invention, a method for combined ground pre-grouting and freezing of a vertical shaft with high water content and fractured sections is provided. The method is applicable to mine vertical shaft projects with high water content and strong fractured Class V surrounding rock at a burial depth of 72.20-117.70m. The grouting reinforcement section covers the bedrock weathering fissure aquifer section where the shaft entrance is located.

[0019] This invention provides a combined construction method for pre-grouting and freezing of the ground surface in a vertical shaft with high water content and fractured sections. By grouting before freezing, segmented grouting, and specialized reinforcement, a composite load-bearing structure of grouting reinforcement layer and freezing water-sealing curtain is constructed. Furthermore, the location of the gate is reserved in the early design and construction phase, and the surrounding rock is specially reinforced. This achieves seamless connection between fractured surrounding rock reinforcement, aquifer sealing, shaft lining, and gate construction, resulting in a triple improvement in quality, efficiency, and safety in the construction of vertical shafts in high water content and fractured sections. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a layout diagram of the drilling plane provided by the present invention; Figure 2 This is a diagram showing the expected diffusion range of grouting provided by the present invention; Figure 3 This invention provides Figure 1 Structural diagram of holes 1-12; Figure 4 This invention provides Figure 1 Structural diagram of holes 13-24 in the middle; Figure 5 This is a schematic diagram of the segmented grouting structure provided by the present invention; Figure 6 This is a schematic diagram of the completed sealing structure provided by the present invention.

[0022] Figure label: 1. Freezing hole; 2. Casing; 3. Sealing device; 4. Grouting pipe. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] In the description of the embodiments of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] The following is combined with Figures 1-6This invention describes a combined construction method for pre-grouting and freezing of the ground surface in a vertical shaft with high water content and fractured sections, comprising the following steps: S1. Based on the same-city exploration data of the shaft, divide it into replacement section, grouting reinforcement section and freezing construction section, and mark and reserve the construction position of the shaft gate in advance.

[0026] The replacement section is selected from the wellbore surface at +46.5 to +43m; the grouting section is determined to be the bedrock weathering and fissure aquifer section at 72.20 to 117.70m; the freezing section is the well neck section above -100m, with a freezing depth of 136m and a lining depth of 129m; the construction position of the -100m gate is reserved in advance during the design stage.

[0027] In the above steps, the construction of each process is conveniently defined, the working space of the gate is locked in advance, and the risk of subsequent freezing pipes encroaching on the gate working area is avoided.

[0028] At the same time, the equipment such as the full hydraulic drilling rig, hydraulic grouting pump, refrigeration unit, total station, and gyro inclinometer are calibrated to ensure the accuracy of equipment operation.

[0029] S2. Implement replacement treatment for the replacement section to form a stable construction foundation, complete the positioning and layout of grouting holes and freezing holes 1, and set up additional grouting holes in the Matoumen area.

[0030] In the above steps, for the unfavorable strata in the surface section of the wellbore (+46.5~+43m, thickness 3.5m), pre-treatment with replacement was implemented to provide a stable foundation for the subsequent construction of grouting holes and freezing hole 1. Specific steps are as follows: Surveying and Excavation: Mark out the center of the well shaft, the replacement area (extend the frozen area of ​​the well shaft by ≥2.5m), and the boundary of the reserved area for the horse head gate. Excavate in layers and slope at 1:0.5 to 1:2. Reserve 20 to 30cm for manual cleaning of the bottom. Set up drainage ditches and water collection wells to dewater and keep the base dry.

[0031] Foundation treatment and trench inspection: Remove debris, weak layers, and accumulated water. If there are karst caves or cavities, fill them with gravel or sand first. Backfilling can only be carried out after the trench has passed inspection.

[0032] Layered paving and compaction: Graded sand and gravel are used as replacement filler, with a loose paving thickness of ≤30cm. Vibratory rollers are used for compaction, with a compaction degree of ≥95% and a moisture content controlled at the optimum moisture content ±2%.

[0033] Quality inspection: After each layer is compacted, the compaction degree is tested using the ring cutter / sand filling method, the surface flatness and elevation are checked, and the overall bearing capacity test (static load / dynamic penetration test) is completed.

[0034] Protective measures: Apply a 5-10cm cement mortar layer to the replacement surface to prevent rainwater erosion. Then, complete the positioning and marking of the grouting holes and freezing holes 1 and ensure proper protection.

[0035] S3. Implement inward retreating segmented pre-grouting operation for the grouting reinforcement section, and carry out special grouting reinforcement for the surrounding rock of Matoumen to achieve the filling of stratum fissures and sealing of aquifer.

[0036] For the bedrock weathering and fissure aquifer section from 72.20 to 117.70 m and the -100 m horizontal horse-head gate opening section, ground pre-grouting reinforcement was implemented. The horse-head gate location was clearly reserved in the early design and construction. By special densification of the hole layout and optimization of grout parameters, the surrounding rock of the horse-head gate was specially reinforced. Ultimately, multiple objectives were achieved, including targeted filling of fissures, sealing of the aquifer, overall reinforcement of the surrounding rock, and strengthening of the horse-head gate area.

[0037] Next, the drilling layout was carried out, with the center of the well as the reference, 24 grouting holes were laid out in a ring 14.1m outward, and 8 additional grouting holes were specially laid out in the double-sided gate area, with the hole spacing controlled at 2.8m. The total station was used for precise positioning, with the hole position deviation ≤50mm, the drilling inclination angle 90° (perpendicular to the surrounding rock of the well), the inclination angle deviation ≤1°, and the deviation rate ≤1%. Among them, the designed depth of boreholes 1-12 is 130m, and the designed depth of boreholes 13-24 is 160m, with a total drilling volume of 3480m, to ensure that the surrounding rock within the gate opening area is fully covered by grouting.

[0038] Drilling operations will prioritize drilling holes 13-24. If fracture water is found within the 130-160m range based on the actual hydrogeological conditions revealed by the boreholes, all boreholes will be adjusted to a depth of 160m.

[0039] A dual-sequence construction method was adopted. Odd-numbered holes were constructed first, and whether to construct even-numbered holes was determined based on the actual grouting expansion range and grout intake. Special attention was paid to the drilling quality in the Matoumen area.

[0040] The drilling structure is a two-stage structure, with coreless drilling throughout the hole: a Φ108mm drill bit is used to open the hole, and after drilling to 2m in the bedrock, a Φ89mm casing 2 is installed. The hole is cemented to 2m in the bedrock, and then a Φ73mm drill bit is used to drill corelessly to the final hole. Mud slurry is used for wall protection in unstable strata above the bedrock. Guiding measures are taken during drilling, and rock samples are collected every 1m of drilling, with a focus on recording the lithology and fracture development of the Matoumen area.

[0041] The backward segmented grouting process is adopted, with each grouting segment being 5m from bottom to top. The grouting segment sealing device 3 is lowered to a position 5m from the bottom of the hole. After the lower grouting is completed, it is moved to the next grouting segment until the design elevation is reached. In the Matoumen area, the grouting segments are densified to one every 3m to ensure the reinforcement density.

[0042] In the above steps, an equipment grouting test is conducted before formal grouting to verify the rationality of raw materials, grout ratio, and construction process.

[0043] Initially, 42.5 grade ordinary Portland cement grout with a water-cement ratio of 1:1 was used for full-fill pressure grouting. Based on monitoring and analysis of the actual engineering geological conditions, the grouting material was ultimately dynamically optimized to 800-mesh ultrafine cement as the core material to ensure effective filling of micro-cracks. When the grout volume was too small or rapid water plugging was required, water glass accelerator (cement grout to water glass grout volume ratio 1:0.5~1:1) was added, with the setting time controlled between 30 seconds and 5 minutes, to enhance the rapid reinforcement effect of the surrounding rock at Matoumen.

[0044] The pressure is dynamically adjusted according to 1.5-2.0 times the static water pressure. The initial pressure is 50% of the design final pressure, and the pressure is gradually increased. The stabilizing pressure in the Matoumen area is increased to 6-8 MPa to ensure the strength of the surrounding rock reinforcement.

[0045] The grouting system consists of a material yard, a mixing tank, a water supply system, a metering system, a grouting pump (2ZBYSB type, maximum pressure 26MPa; BW-250 type, maximum pressure 7MPa), grouting pipes, and a sealing device. The high-pressure hose can withstand 1.5 to 2.0 times the maximum design grouting pressure.

[0046] The standard for the end of single-hole grouting is: after reaching the design final pressure, stabilize the grouting for 10-15 minutes, and the unit grout intake is <5L / min; if cross-grouting occurs, seal the cross-grouting hole in time, and use linkage grouting if necessary. The pressure stabilization time in the Matoumen area needs to be extended to 15-20 minutes.

[0047] Grouting effect testing and sealing: The grouting effect is tested by a combination of core sampling and water pressure test. The core sampling qualification rate is ≥95%, the core sampling qualification rate in the Matoumen area is ≥98%, the water pressure test permeability is ≤0.5Lu, and the water sealing rate reaches 100%.

[0048] After grouting is completed, thick cement grout with a water-cement ratio of 0.5:1 is used to seal the holes and block the gap between the grouting pipe and the hole wall; unqualified areas are immediately supplemented with grouting, with a focus on checking the grouting quality of the horse head gate area.

[0049] S4. After the grouting is accepted, the sectional freezing operation is carried out. The freezing hole 1 is set up to avoid the construction area reserved for the horse head gate, forming a composite load-bearing structure with the grouting reinforcement layer superimposed on the freezing curtain. The various indicators of the frozen wall are checked to ensure that they meet the design requirements.

[0050] Specifically, freezing holes 1 are arranged in a single ring with a ring diameter of 11.3m, totaling 35 holes with a hole spacing of 1.013m and a hole depth of 136m. Two temperature measurement holes (136m) and two hydrological holes (27m and 88m) are also laid out simultaneously. The total amount of freezing drilling is 5147m. The layout of freezing holes 1 avoids the reserved construction area of ​​the horse-head gate to avoid interfering with subsequent operations.

[0051] The construction of freezing hole 1 was carried out using a TSJ-300E drilling rig with mud wall protection. The borehole deviation was strictly controlled: the maximum distance between adjacent holes was ≤2.00m, the inward deviation was no more than 0.3m, and the deviation rate of the temperature measuring hole was ≤3‰.

[0052] The freezing pipe is made of Φ133×5mm low carbon seamless steel pipe, and is connected by butt welding with Φ146×5mm external coupling. After the pipe is installed, a water pressure resistance test is carried out. The test pressure is 1.90Mpa. The pressure drop value within 30 minutes is <0.05MPa to be qualified.

[0053] Freezing station installation and commissioning: A freezing and refrigeration station is set up, using 5 W-YSLGF1000Ⅲ type refrigeration units and 5 DBNL3-200 type cooling towers, along with supporting equipment such as brine pumps and clean water pumps, to complete the installation of the fluorine system, brine system, and cooling water system.

[0054] Brine preparation: Use 74% calcium chloride solution. During the active freezing period, the brine temperature should be controlled at -27~-31℃, and during the maintenance freezing period, it should be controlled at -23~-27℃.

[0055] The three major refrigeration circulation systems undergo pressure testing and vacuum leak testing according to specifications. After passing the tests, the low-temperature pipelines and equipment are insulated and wrapped to ensure that the cooling loss is ≤15%.

[0056] Turn on the refrigeration unit and cool it down at a rate of ≤3℃ every 24 hours. Monitor the brine temperature, the temperature difference between the brine and the return loop, and the expansion status of the frozen wall in real time. The temperature difference between the brine and the return loop should be ≤2℃.

[0057] A segmented freezing mode was adopted, with each 30m segment being a freezing section, and the process was carried out step by step. A grouting reinforcement layer was used to block water flow and prevent the frozen wall from melting, settling, and cracking. The development of the frozen wall in the Matoumen area was monitored in detail.

[0058] Real-time monitoring of temperature and hydrological data was conducted to analyze the freezing wall formation. The freezing wall formation time of the main aquifer was approximately 53 days, and the trial excavation stage began after 7 days of stable water level rise.

[0059] Acceptance of frozen walls: When the temperature of the sand and soil drops to -8℃, the uniaxial compressive strength of the frozen wall must be ≥10.78MPa, the thickness of the frozen wall must be ≥2.0m and completely enclosed, and the strength of the frozen wall around the gate must be ≥12MPa. Only after the acceptance rate is 100% can the well shaft excavation and construction process begin.

[0060] S5. After the frozen wall passes the acceptance inspection, the well shaft excavation and lining operation shall be carried out. The excavation of the head gate shall be carried out at the reserved position of the head gate that has been specially reinforced by grouting. The excavation process shall follow the construction process of first supporting and then expanding.

[0061] The top-down short-section excavation and masonry method was adopted, and the exposed height of the surrounding rock was strictly controlled to be ≤1.5m and the exposure time to be ≤8h. Reinforced concrete support was carried out in a timely manner, and the support strength compliance rate was 100%.

[0062] During the excavation and lining process, the settlement of the surrounding rock and the displacement of the well wall are monitored in real time. The settlement amount is ≤3mm / d and the displacement amount is ≤2mm / d. If any abnormality occurs, work is stopped immediately for handling.

[0063] If blasting is required in the bedrock section, the distance between the blast hole and the freezing pipe should be ≥1.2m, the blast hole depth should be ≤1.8m, millisecond delay detonators should be used for smooth blasting, the charge amount should be strictly controlled, the freezing station should be notified to stop brine circulation 1 hour before blasting, and the brine tank water level and well wall condition should be checked after blasting. Circulation should be resumed after confirming that there is no damage.

[0064] Uninterrupted construction of the gate: Relying on the pre-reserved construction space and specially reinforced surrounding rock, the gate opening is constructed within the grouting reinforcement area, completely avoiding the freezing pipe laying area, thus avoiding construction interference; The process of first supporting and then expanding the grouting is adopted. The temporary support structure is poured first, and the expansion grouting operation is carried out after the support strength reaches the standard. This ensures that the regularity of the horse head gate is ≥98%, with no water leakage or collapse, and fully utilizes the effect of the special grouting reinforcement in the early stage.

[0065] S6. After the permanent support construction of the well shaft is completed, the freezing operation is stopped in sections, the freezing pipe is filled and sealed, and the entire process is completed and accepted.

[0066] After the permanent support of the well is completed, the refrigeration unit is shut down in an orderly manner in a segmented shutdown mode to avoid rapid thawing and settling of the frozen wall, which could cause cracks in the well wall. The freeze-thaw deformation in the Matoumen area is monitored. The frozen pipe is filled with 1:1 cement grout with a filling density of ≥98% to prevent groundwater infiltration in the later stage.

[0067] In a specific embodiment of the present invention, the replacement treatment adopts layered backfilling and compaction of graded sand and gravel. The graded sand and gravel particles are reasonably matched, which can improve the overall compaction performance and deformation resistance of the fill material and reduce uneven settlement of the foundation in the later stage.

[0068] The mud content of the replacement fill is ≤3%, which can avoid the problem of the mud softening when it comes into contact with water, causing the fill strength to decrease and the foundation to creep and deform. The loose layer thickness is not more than 30cm, which can ensure that each layer of fill is fully compacted and prevent the lower layer from being insufficiently compacted and dead corners from appearing due to excessively thick layers. The backfill compaction degree is ≥95%, which can improve the overall bearing capacity of the replaced foundation and enhance the foundation's ability to resist the action of the upper load.

[0069] After the replacement is completed, a 5-10cm thick cement mortar protective layer is set on the replacement surface. This layer can isolate external rainwater and surface water from seeping into the interior of the graded sand and gravel replacement layer, prevent the replacement material from being disturbed by water immersion, and protect the surface of the sand and gravel replacement layer from external disturbance and damage, thus maintaining the long-term structural stability of the replacement foundation.

[0070] In a specific embodiment of the present invention, in step S3, the grouting holes adopt a hole arrangement of annular main holes plus denser holes in the horse-head gate area. The annular main holes can form an outer closed grouting curtain to achieve the delineation and reinforcement of the entire stratum. The denser holes in the horse-head gate area can specifically strengthen the weak parts of the horse-head gate where stress is concentrated and the stress is complex, and avoid the occurrence of grouting blind spots at the horse-head gate position.

[0071] The grouting segment length is set to 5m. This segment length can control the grouting range in a single operation in conventional strata, which is conducive to stable control of grouting pressure, ensures uniform grout diffusion, and improves the overall integrity of strata reinforcement in ordinary areas.

[0072] The grouting in the Matoumen area is divided into 3m sections, shortening the grouting section length in this critical area. This reduces the volume of grout in a single section, improves the density of grout filling at Matoumen, and effectively addresses the high-risk conditions and large-scale geological disturbance in the Matoumen area. The grouting holes are constructed using a dual-sequence drilling method, which allows for alternating and staggered drilling operations. This avoids the problems of grout cross-cutting and leakage caused by single-sequence drilling, improves the coordination between drilling and grouting operations, and further ensures the overall grouting reinforcement effect of the strata.

[0073] In a specific embodiment of the present invention, the grouting slurry is mainly composed of ultrafine cement. The ultrafine cement particles have a small particle size and can penetrate into the interior of tiny fissures in the formation, thereby increasing the fissure filling rate and enhancing the overall strength of the formation consolidation.

[0074] The water-cement ratio is set to 1:1. This ratio can balance the fluidity of the slurry and the strength of the solidified body, ensuring smooth delivery and diffusion of the slurry, while avoiding the defect of insufficient solidified body strength caused by an excessively high water-cement ratio. When encountering water inrush conditions, water glass accelerator is added to accelerate the gel solidification speed of the slurry, inhibit the scouring and dilution effect of the water inrush on the slurry, and reduce slurry loss.

[0075] The volume ratio of cement grout to water glass grout is controlled at 1:0.5 to 1:1. This ratio range allows for flexible adjustment of the grout setting time, adapting to different water inflow conditions and ensuring rapid grout formation and sealing at the water inflow location.

[0076] The grouting pressure in the Matoumen area is increased to 6-8 MPa. The higher pressure can promote the grout to be fully squeezed into the strata fissures around Matoumen, improve the grout filling density in this stress concentration area, enhance the strata reinforcement effect in the Matoumen area, and reduce the risk of water instability during excavation.

[0077] In a specific embodiment of the present invention, in step S3, the single-hole grouting ends when the design final pressure is reached and then stabilized for 10-15 minutes. This stabilization time allows the grout to be fully squeezed and filled in the formation fractures, reducing the shrinkage voids in the later stage of the grout and ensuring the compactness of the grouting reinforcement area.

[0078] The pressure stabilization time in the Matoumen area is extended to 15-20 minutes. For key areas with concentrated stress and large stratum disturbance in Matoumen, extending the pressure stabilization time can promote the full penetration and filling of complex fissures by the grout, and avoid the hidden danger of incomplete local grouting.

[0079] Meanwhile, the unit grout intake is less than 5L / min. This is used as an auxiliary termination indicator, which can intuitively reflect that the formation fractures have been basically filled with grout. This avoids the illusion of high pressure but insufficient grouting in the actual formation, and ensures that the quality of single-hole grouting reinforcement meets the design requirements.

[0080] In a specific embodiment of the present invention, in step S4, the segmented freezing is carried out segment by segment with each freezing segment being 30m. Segmented operation can reduce the scale of a single freezing operation, facilitate precise control of the freezing conditions of each segment, reduce the overall frost heave deformation of the stratum, and avoid the risk of frost heave stress concentration caused by long-distance one-time freezing.

[0081] During the active freezing period, the brine temperature is controlled between -27℃ and -31℃. This low-temperature range provides sufficient cooling capacity, accelerates the cooling rate of the soil, shortens the formation cycle of the frozen wall, and ensures that the soil quickly forms a continuous frozen structure.

[0082] During the freezing period, the brine temperature should be controlled between -23℃ and -27℃. While maintaining the stability of the frozen wall, the brine temperature should be appropriately increased to reduce the consumption of cold energy, avoid excessive freezing and excessive soil frost heave, and balance engineering safety and construction energy consumption.

[0083] The acceptance criteria for frozen walls include: the frozen walls must be completely enclosed to ensure the formation of a closed and waterproof frozen soil retaining structure that blocks the seepage of external groundwater; the temperature of the sand must be reduced to below -8℃ to ensure that the sand is fully frozen, reduce the content of unfrozen water inside the sand, and improve the waterproof performance of the frozen soil itself.

[0084] The thickness of the frozen wall is ≥2.0m. Sufficient frozen wall thickness can improve the overall structure's resistance to deformation, resist external water and soil pressure, and prevent the frozen wall from cracking.

[0085] The uniaxial compressive strength of the frozen wall around the horse-head gate is ≥12MPa. This ensures that the frozen soil has a high mechanical bearing capacity, resists load disturbances during excavation, and prevents the horse-head gate from becoming unstable and causing water and sand inrush accidents, especially in the critical areas where the horse-head gate is subjected to complex stress and stress concentration.

[0086] In a specific embodiment of the present invention, the real-time monitoring of multiple parameters throughout the entire process of steps S1-S6 enables dynamic tracking of key working conditions throughout the construction process, thereby achieving controllable and traceable construction process.

[0087] Monitoring parameters include: compaction degree of the replacement fill, which provides direct feedback on the construction quality of the replacement foundation and allows for timely identification of potential problems such as substandard foundation compaction; grouting pressure, which allows real-time monitoring of the grouting construction status and prevents overpressure from fracturing the strata or insufficient pressure from causing incomplete grouting; grout absorption, which helps determine the filling of stratum fissures and assists in assessing the effectiveness of the grouting construction; freezing temperature, which monitors the development of the frozen wall and promptly identifies problems such as insufficient cooling of localized frozen soil; groundwater level, which allows for monitoring of groundwater dynamics and predicting the risk of sudden water inrush; surrounding rock settlement, which reflects the overall deformation of the strata and captures early signs of surrounding rock instability; and wellbore displacement, which monitors the stress and deformation of the wellbore structure in real time and avoids the risk of wellbore cracking and damage.

[0088] Monitoring points are densely deployed in the gate area, increasing the density of monitoring data for key areas with concentrated stress and high risk levels. This allows for the detection of subtle local deformations and parameter fluctuations, preventing missed risk assessments due to monitoring blind spots. The anomaly warning response time is ≤10 minutes, shortening the waiting time for risk handling, enabling rapid identification and timely intervention of hazards, and effectively reducing the probability of construction accidents.

[0089] In a specific embodiment of the present invention, in step S6, the freezing is stopped in a segmented shutdown mode, which can achieve orderly and slow thawing of frozen soil, avoid the synchronous and rapid melting of the frozen wall caused by a one-time overall shutdown, slow down the stratum thawing rate, and reduce the concentration of thawing stress.

[0090] The inside of the freezing pipe is filled with 1:1 cement grout. The cement grout with the above ratio has good flow and filling performance and later consolidation strength, which can replace the residual brine in the freezing pipe and consolidate and fill the internal space of the freezing pipe.

[0091] With a filling density of ≥98%, the frozen pipe is free of voids and gaps, forming a high-strength solidified body. This can transform the frozen pipe into an internal reinforcement component, preventing the formation of weak channels after the frozen pipe melts and sinks. It also avoids the risk of well wall cracking caused by rapid melting and settling of the frozen wall, and improves the long-term service stability of the formation and well wall structure.

[0092] The present invention provides a method for combined surface pre-grouting and freezing construction of high water-rich and fractured sections of vertical shafts. Targeting the bedrock fracture zone and weathered fissure aquifer at the foundation of the vertical shaft wall, the method first performs pre-filling treatment on the surface section of the shaft, then performs targeted segmented pre-grouting reinforcement on the high water-rich fractured section from 72.20 to 117.70m (the design and construction reserved a -100m gate position, and the surrounding rock of the gate was reinforced by increasing the density of holes and optimizing the grout parameters), and finally performs segmented freezing construction on the shaft neck section above -100m, forming a three-level synergistic bearing system of surface replacement, grouting reinforcement, and freezing water sealing.

[0093] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.

[0094] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "method," "specific method," or "some methods," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or method is included in at least one embodiment or method of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or method. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or methods. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or methods described in this specification, as well as the features of different embodiments or methods.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for combined construction of ground pre-grouting and freezing in a vertical shaft with high water content and fractured sections, characterized in that, include: S1. Based on the shaft engineering survey data, divide the replacement section, grouting reinforcement section and freezing construction section, and mark and reserve the construction position of the vertical shaft gate in advance; S2. The replacement section is replaced to form a stable construction foundation. The positioning and layout of the grouting holes and freezing holes (1) are completed. The grouting holes are densified for the Matoumen area. S3. Implement ground-retreating segmented pre-grouting operations on the grouting reinforcement section to carry out special grouting reinforcement of the surrounding rock of Matoumen, so as to achieve the filling of stratum fissures and sealing of aquifers. S4. After the grouting is accepted, the sectional freezing operation is carried out. The freezing holes (1) are arranged to avoid the construction area reserved by the horse head gate, forming a composite load-bearing structure with the grouting reinforcement layer superimposed on the freezing curtain. The various indicators of the freezing wall are checked to ensure they meet the design requirements. S5. After the frozen wall passes the acceptance inspection, the well shaft excavation and lining operation shall be carried out. The excavation of the head gate shall be carried out at the reserved position of the head gate that has been specially reinforced by grouting. The excavation process shall follow the construction process of first supporting and then expanding. S6. After the permanent support construction of the well shaft is completed, the freezing operation is stopped in sections, the freezing pipe is filled and sealed, and the entire process is completed and accepted.

2. The combined construction method of ground pre-grouting and freezing for high water-rich and fractured sections of vertical shafts according to claim 1, characterized in that, In step S2, the replacement treatment adopts graded sand and gravel layered backfilling and compaction, the mud content of the replacement material is ≤3%, the loose layer thickness is not greater than 30cm, and the backfill compaction degree is ≥95%; after the replacement is completed, a 5-10cm thick cement mortar protective surface layer is set on the replacement surface.

3. The combined construction method of ground pre-grouting and freezing for high water-rich and fractured sections of vertical shafts according to claim 1, characterized in that, In step S3, the grouting holes adopt a hole layout of annular main holes plus additional holes in the horse-head gate area; the grouting segment length of the formation is set to 5m, and the grouting segment in the horse-head gate area is densified to 3m; the grouting holes are constructed using a dual-sequence drilling method.

4. The combined construction method of ground pre-grouting and freezing for high water-rich and fractured sections of vertical shafts according to claim 1, characterized in that, In step S3, the grouting slurry is mainly made of ultrafine cement, and the water-cement ratio is set to 1:1; when encountering water inrush conditions, water glass quick-setting agent is added, and the volume ratio of cement slurry to water glass slurry is controlled at 1:0.5~1:1; the grouting pressure stabilization pressure in the Matoumen area is increased to 6-8MPa.

5. The method for combined construction of high water-rich vertical shafts, fractured sections, and ground pre-grouting and freezing as described in claim 1, is characterized in that... In step S3, the conditions for ending single-hole grouting are: after reaching the designed final pressure, stabilize the pressure for 10-15 minutes, extend the stabilization time in the Matoumen area to 15-20 minutes, and at the same time, the unit grout intake is less than 5L / min.

6. The combined construction method of ground pre-grouting and freezing for high water-rich and fractured sections of vertical shafts according to claim 1, characterized in that, In step S4, the sectional freezing is carried out segment by segment, with each segment being 30m long. During the active freezing period, the brine temperature is controlled at -27℃ to -31℃, and during the maintenance freezing period, the brine temperature is controlled at -23℃ to -27℃. The acceptance conditions for the frozen wall include that the frozen wall is completely enclosed, the sand temperature drops below -8℃, the frozen wall thickness is ≥2.0m, and the uniaxial compressive strength of the frozen wall around the gate is ≥12MPa.

7. The method for combined construction of high water-rich vertical shaft, fractured section ground pre-grouting and freezing as described in claim 1, is characterized in that, In step S5, the well casing is excavated and lined using a top-down short-section excavation and lining process, with the surrounding rock exposure height ≤1.5m and the surrounding rock exposure time ≤8h; during blasting operations, the distance between the blast hole and the freezing pipe is not less than 1.2m, the brine circulation is suspended before blasting, and the freezing circulation is resumed after the freezing pipe is checked for damage after the blasting is completed.

8. The method for combined construction of high water-rich and fractured section ground pre-grouting and freezing in vertical shafts according to claim 1, characterized in that, Steps S1-S6 involve real-time monitoring of multiple parameters throughout the entire process. The monitored parameters include the compaction degree of the replacement fill, grouting pressure, grout intake, freezing temperature, groundwater level, surrounding rock settlement, and well wall displacement. Monitoring points are densely deployed in the Matoumen area, and the abnormal early warning response time is ≤10min.

9. The combined construction method of ground pre-grouting and freezing for high water-rich and fractured sections of vertical shafts according to claim 1, characterized in that, In step S6, the freezing is stopped in a segmented shutdown mode. The inside of the freezing pipe is filled with 1:1 cement slurry with a filling density of ≥98% to avoid the risk of well wall cracking caused by rapid melting and settling of the frozen wall.

10. The combined construction method of ground pre-grouting and freezing for high water-rich and fractured sections of vertical shafts according to claim 1, characterized in that, The method is applicable to mine shaft engineering with high water content and strong fractured Class V surrounding rock at a burial depth of 72.20-117.70m. The grouting reinforcement section covers the bedrock weathering fissure aquifer section where the shaft gate is located.

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