An anchor plate structure for underground powerhouses and its construction method

Abstract

This invention belongs to the field of water conservancy and hydropower engineering technology, and discloses an anchor plate structure for underground powerhouses and its construction method. The construction method includes S1, support construction: S1.1 mortar anchor bolt construction, S1.2 prestressed anchor cable construction, S1.3 anchor pile construction; S2, rock wall treatment; S3, anchor plate concrete construction: S3.1 base surface cleaning and acceptance, S3.2 surveying and setting out, S3.3 scaffolding erection, S3.4 reinforcement construction, S3.5 formwork installation, S3.6 cleanup and acceptance, S3.7 concrete transportation, S3.8 concrete pouring, S3.9 finishing and smoothing, S3.10 concrete curing and demolding, S3.11 protection of the formed concrete. This invention involves pouring a concrete sprayed layer on the crane beam formed by excavation of the rock wall, and connecting the anchor plate to the outside of the concrete sprayed layer through anchor piles and prestressed anchor cables. The resulting support structure has good stability, can be completed in one go, and has a simple construction process.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower engineering technology, specifically to an anchor plate structure for underground powerhouses and its construction method. Background Technology

[0002] The most critical issue in the construction of water conservancy and hydropower projects is the rational layout of major hydraulic structures based on actual hydrological, topographical, and geological conditions, while also considering structural safety and economic efficiency. Among these, the hydropower plant is one of the most important hydraulic structures in water conservancy and hydropower projects, and its design and construction require careful consideration of various factors to ensure its safe, stable, and efficient operation. Currently, due to limitations imposed by the dam site's topography or the overall layout requirements of the project, some hydropower plants need to be located far from the riverbed. Therefore, a riverbed-type hydropower plant structure cannot be used, and in areas with open ground and good foundation bearing capacity, a surface-mounted power plant structure is typically adopted. However, in high mountain and canyon areas where the terrain is steep and surface structures are difficult to arrange, underground power plants are often used, forming an underground hydropower plant structure.

[0003] Currently, existing underground hydropower station powerhouse structures face the following problems during construction:

[0004] 1) The surrounding rock at the plant site has poor integrity, with weak connections between different rock layers and voids and cracks between them, introducing certain uncertainties to the construction of the underground plant. Therefore, the risk of rock collapse and slippage increases during excavation, highlighting safety issues and placing higher demands on the support engineering of the underground plant.

[0005] 2) The formation of the crane beams on the rock face of the underground powerhouse is difficult, and there is no rock platform foundation. Furthermore, the uneven bedrock surface after excavation results in uneven distribution of the anchor plate thickness, which in turn leads to uneven stress distribution throughout the structure. These problems cause the underground powerhouse structure to frequently require adjustments and multiple reinforcements during construction, making the construction process difficult and costly. Summary of the Invention

[0006] This invention aims to provide an anchor plate structure for underground powerhouses and its construction method. A concrete sprayed layer is poured on the excavated rock wall crane beam. An anchor plate is connected to the outside of the concrete sprayed layer by anchor piles and prestressed anchor cables. The anchor rods of the anchor piles are exposed, and multiple anchor rods are evenly arranged alternately. The resulting support structure has good stability and can be completed in one go. The construction process is simple and solves the problems described in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A construction method for an anchored plate structure used in an underground powerhouse includes the following steps:

[0009] S1, Support Construction

[0010] S1.1 Mortar Anchor Construction

[0011] Mortar anchors are added to the anchor plate. The side wall anchors adopt the construction process of grouting first and then inserting reinforcement bars. The construction process is as follows: setting up a working platform, surveying and setting out, drilling, flushing the hole, mechanical grouting, inserting reinforcement bars, backfilling the hole with mortar, fixing the hole, and waiting for curing protection.

[0012] S1.2 Prestressed Anchor Cable Construction

[0013] Prestressed anchor cables are added to the anchor plate, and steel anchor piers are located outside the anchor plate. After tensioning, concrete is used to seal the anchor. The construction process is as follows: construction preparation, surveying and setting out, drilling, anchor cable installation, grouting of the anchoring and tensioning sections, installation of steel anchor piers, tensioning, sealing and grouting, and anchor head protection treatment.

[0014] S1.3 Anchor Pile Construction

[0015] Anchor piles are added to the anchor plate and arranged at intervals with the system anchor rods and anchor cables. The construction process is as follows: measurement and positioning: drilling rig positioning, hole drilling, hole flushing or hole washing, installation of anchor piles, and grouting of cement mortar.

[0016] S2, Rock Wall Treatment

[0017] The minimum thickness of the anchor plate is required to be no less than 30cm. If the local anchor plate thickness is less than 30cm, the shotcrete and rock wall should be manually removed according to the actual situation to ensure that the anchor plate concrete is 30cm thick and meets the structural edge line.

[0018] S3, Anchor Plate Concrete Construction

[0019] S3.1 Base surface cleaning and acceptance

[0020] Remove loose stones, wall base debris, and accumulated materials from the concrete pouring area of ​​the anchor plate to ensure that the rock surface is clean and moist, without under-excavation or loose rock before foundation acceptance.

[0021] S3.2 Measurement and Setting Out

[0022] Use a total station or level to conduct precise measurement and layout, mark the station number and elevation control points of the anchor plate shape of the lower part of the rock wall crane beam in a clear and fixed position, and mark the elevation points in a place that is easy to measure, determine the reinforcement binding, formwork edge line and beam top elevation, and make conspicuous marks and protective measures.

[0023] S3.3 scaffolding erection

[0024] The construction scaffolding is erected using standard socket-type disc-lock steel pipe supports, with all anchor plates deployed at once, and the entire working surface is erected in one go.

[0025] S3.4 Reinforcing Steel Construction

[0026] After the anchor plate reinforcement is fabricated off-site, it is tied and installed according to the compartmentalization diagram of the underground plant and the planned segmented and compartmentalized construction sequence.

[0027] S3.5 Template Installation

[0028] Before installing the formwork, set concrete pads on the inside of the formwork at intervals according to the position of the structural line, and clean the formwork surface and apply release agent;

[0029] S3.6 Clearance Inspection

[0030] Before pouring concrete, clean up the debris in the sump, rinse it clean, remove any accumulated water, and inspect the reinforcing bars and embedded parts. The surface of the construction joint and the keyway should be roughened and rinsed clean with water before pouring concrete. After passing self-inspection, re-inspection, and final inspection, the concrete should be put into the sump.

[0031] S3.7 Concrete Transportation

[0032] Concrete is transported horizontally to the work site using concrete mixer trucks, and vertically transported using concrete pumps and compacted using immersion vibrators.

[0033] S3.8 concrete pouring

[0034] Normal concrete was used. For the anchor plate concrete under the rock wall crane beam, a concrete pump was used as the main means of placement, with a crane bucket used as an auxiliary means. The concrete was poured in thin layers using a flat-laying method. The anchor plate concrete was poured in sections according to the segmented and compartmentalized plan. Each section was poured in layers from bottom to top, with each layer being 30-40cm thick. A self-made sheet metal chute was used to extend into the compartment for loading and unloading, controlling the concrete pouring height and preventing segregation.

[0035] S3.9 Finishing and Finishing

[0036] After the concrete is poured, level the surface in a timely manner. After leveling, the top of the anchor plate should be flat and the elevation should be accurate. Before the initial setting of the concrete after the elevation is completed, insert reinforcing bars into the joint surface as required.

[0037] S3.10 Concrete Curing and Demolding

[0038] Water curing should begin 12 to 18 hours after concrete pouring and placement; after the side and end forms are removed, the lower anchor plate of the rock wall crane beam should be continuously sprayed with water and cured to ensure that the concrete of the anchor plate remains continuously moist.

[0039] The head formwork is removed after the concrete has set, the side formwork is removed after the concrete has reached 75% strength, and the bottom formwork is removed after the concrete has reached 100% of its design strength according to specifications.

[0040] S3.11 Concrete Protection

[0041] When the anchor plate is being poured, the surrounding rock must not be excavated or blasted; the excavation of the surrounding rock can only be carried out after the concrete strength of the anchor plate has reached the design strength at 28 days, and the vibration velocity of the blasting safe mass point is less than 7 cm / s.

[0042] After the formwork is removed, wooden formwork, bamboo planks, and old tires are used to cover and protect it. After the blasting, the damaged bamboo planks are repaired in time to ensure that the concrete of the anchor plate is not damaged.

[0043] Furthermore, in S1.1, the construction steps for mortar anchor bolts are as follows:

[0044] S1.1.1 Materials to be prepared: Anchor rods are threaded steel bars; cement is ordinary Portland cement with a strength grade of not less than 42.5; sand with a maximum particle size of less than 2.5mm and a fineness modulus between 2.4 and 2.8 is medium-fine sand, which should be sieved before use; the strength grade of cement mortar is not less than M25; the strength grade of cement mortar for prestressed anchor rods is not less than M30.

[0045] S1.1.2 Drilling: Anchor bolt holes are drilled by erecting scaffolding and using a construction platform filled with slag for elevation. The hole position deviation is no more than 10cm. The angle between the hole axis of the fault-reinforced anchor bolt and the possible sliding surface is greater than 45°. After drilling to the specified depth, the hole is blown out with high-pressure air to remove debris. Before grouting, the rock powder in the hole is blown out and the accumulated water is drained.

[0046] S1.1.3 Anchor bolt installation and grouting: Cement mortar is mixed on site and the construction is carried out by "grouting first and then inserting anchor bolts";

[0047] S1.1.4 Maintenance: After grouting, the anchor rod shall be protected from being hit, collided, pulled out and damaged by blasting vibration before the mortar strength reaches 70% of the design strength.

[0048] S1.1.5 Anchor bolt quality inspection: 7 days after anchor bolt grouting, non-destructive testing methods are used to inspect the mortar density and anchor bolt length.

[0049] S1.1.6 Non-conformance handling: The length ratio of anchor bolts shall be tested using non-destructive testing methods. The testing ratio of permanent anchor bolts in conventional locations shall not be less than 10% of the total number of constructions. The length of the bolt inside the hole shall be greater than or equal to 95% of the design length to be considered qualified.

[0050] Specifically, in S1.1.3, the method of "grouting first and then inserting anchor bolts" is as follows:

[0051] Before grouting, the end of the grouting pipe is cut into an oblique shape, and a mark is made on the grouting pipe according to the rock penetration depth of the anchor rod to check whether the grouting pipe has been sent to the bottom of the hole. During grouting, the grouting pipe is inserted to the bottom of the hole, and then pulled out 50-100mm to start grouting. The grouting pipe is slowly and evenly pulled out as the mortar is injected to fill the hole with grout.

[0052] During the fabrication of the anchor rods, the designed anchorage length is marked on the rod body with spray paint, and a centering ring made of steel bars is installed at 1 / 3 of the rod body to ensure the protective layer of the anchor rod. Permanent support anchor rods with pre-grouting are used. After the mortar in the hole is filled, the rod is inserted immediately. The insertion hole is temporarily sealed during the insertion to prevent excessive mortar overflow. When the rod body depth reaches the designed anchorage length, the anchor rod is fixed. If no mortar overflows from the hole after the rod body is inserted, the cause should be found and replenished in time.

[0053] In S1.1.6, if the pass rate of the spot check is greater than 90%, the spot check of the anchor bolts in the work area is qualified, and the anchor bolts that are found to be unqualified are re-laid; if the pass rate is less than 90%, the spot check ratio is increased first. If the pass rate is still less than 90%, all are checked, and the unqualified ones are re-laid.

[0054] Furthermore, in S1.2, the anchor cable holes are constructed by erecting scaffolding and filling the construction platform with slag for climbing, and a hydraulic crawler anchor cable drilling rig is used for drilling. For areas with severe geological collapse and where drilling is impossible, a pipe-assisted drilling process without pipe removal is adopted.

[0055] Furthermore, in S1.3, the construction steps for anchor piles are as follows:

[0056] S1.3.1 Fabrication of anchor piles: Anchor piles are composed of multiple hot-rolled steel bars, grout inlet pipes, and grout return pipes;

[0057] S1.3.2 Drilling and cleaning: Drilling is carried out using an anchor drilling machine; after drilling is completed, pressurized air is used to blow the rock cuttings out of the hole and the hole opening is temporarily sealed to prevent foreign objects from falling into the hole;

[0058] S1.3.3 Anchor pile installation and grouting

[0059] The construction method involves first inserting anchor piles and grouting system, and then immediately grouting. Truck cranes and truck-mounted cranes are used in conjunction with manual installation. After drilling, one pile is installed and grouted at a time.

[0060] Specifically, in S1.3.1, the method for fabricating anchor piles is as follows:

[0061] Before fabricating the anchor piles, the reinforcing bars are straightened, rusted, and cleaned. The anchor piles are spliced ​​using threaded sleeves. Adjacent reinforcing bars of the anchor piles are connected by electric welding at 150cm intervals. The grout inlet and outlet pipes of the anchor piles are made of steel pipes, which are connected to adjacent reinforcing bars by electric welding at 150cm intervals. To ensure that the anchor piles are centered in the hole, a ring of centering reinforcing bars is set every 200cm on the anchor pile body and welded to the reinforcing bars of the anchor pile body.

[0062] In S1.3.2, the drilling of anchor piles is carried out by erecting scaffolding and constructing a platform for filling with slag; the diameter of the drill bit is more than 2.5cm larger than the diameter of the anchor pile, the hole diameter is not less than 90mm, the allowable deviation is 100cm, and the allowable deviation of the hole depth is ±50mm; the hole axis is perpendicular to the bedrock surface. When the angle between the drilling direction and the obvious structural surface decreases, the direction of some anchor piles is adjusted to increase the angle between them. For rock masses with developed fissures, special combination drilling tools are used to ensure hole formation.

[0063] Before installing anchor piles, check the cleaning of the anchor pile holes to remove accumulated water and rock powder; before grouting, blow away the rock powder in the holes and drain the accumulated water; after grouting, do not knock, bump or pull the anchor rods before the mortar solidifies; anchor piles that have not been grouted or that are only sealed with mortar at the hole opening are considered waste anchor piles.

[0064] The cement mortar used for anchor pile grouting has a cement-to-sand weight ratio of 1:1 to 1:2 and a cement-to-water weight ratio of 1:0.38 to 1:0.45. The aggregate is medium and fine sand with a maximum particle size of less than 2.5 mm. It is screened and cleaned before use. The cement mortar is mixed evenly to prevent stones or other impurities from being mixed in. It is mixed and used immediately and used up before initial setting.

[0065] The method for grouting anchor piles is as follows: the grouting pipe is firmly fixed on the anchor pile and kept unobstructed, and inserted into the hole along with the reinforcing bar. The grouting pipe is 20cm away from the bottom of the hole. For anchor piles with a depression angle of less than 30°, an exhaust pipe needs to be installed and the hole opening needs to be sealed before grouting. Grouting must be stopped when the exhaust pipe exits the grouting pipe or when no more exhaust is required.

[0066] Furthermore, in S3.3, the scaffolding is constructed using a customized product assembly method on-site. The scaffolding serves as a concrete pouring platform, with its surface fully covered by double-layered bamboo planks. The bamboo planks are then tied to the steel pipe scaffolding with wire to prevent slippage. The spacing between uprights is 120cm x 120cm, and the step distance is 150cm. A standard safety rotating ladder is installed every 50m on the outside of the scaffolding for personnel to ascend and descend. Safety nets are hung on the exposed surfaces of the scaffolding and ladders to ensure the safety of construction workers.

[0067] Furthermore, in S3.4, the steps for rebar installation are as follows:

[0068] S3.4.1 Rebar processing and transportation: The rebar processing process is as follows: rebar identification, layout, inspection, cutting, bending, finished sample, numbering; the surface of the rebar after processing is clean and undamaged, and paint pollution and rust are cleaned before use. Rebar with granular or flaky old rust shall not be used.

[0069] The pre-processed steel bars are loaded and unloaded by crane, transported to the construction site by flatbed truck, and then manually moved to the work surface and neatly arranged according to the type and model of the steel bars.

[0070] S3.4.2 Reinforcing Steel Installation: The welding of the reinforcing steel is completed off-site, and it is transported to the site for direct installation. Before the reinforcing steel is tied and installed, the positions of each embedded part are marked on the rock platform by surveying and marking. The reinforcing steel is staggered from the positions of the embedded parts at this point. The installation of the reinforcing steel follows the principles of "bottom to top, i.e., bottom first and then top; inside to outside, i.e., tie the reinforcing steel on the side closest to the rock wall first, and then tie the reinforcing steel on the side furthest from the rock wall; bend first and then straighten, with clear layers and mutual coordination."

[0071] The joints of welded steel bars shall meet the requirement that the joint area within the same connection section does not exceed 50%, and the lap length shall be constructed according to the design requirements and relevant specifications. Among them, when welding the joints of longitudinal steel bars and circumferential steel bars, the joints shall be staggered and the steel bars shall pass through the construction joint. The steel mesh on the outer side of the anchor plate shall be firmly welded to the exposed ends of the system anchor rods and anchor piles using L-shaped connecting hook steel bars. When the connecting hook steel bars are welded to the exposed ends of the steel mesh on the outer side of the anchor plate and the anchor rods and anchor piles, the length of the weld on both sides shall not be less than 15cm. The cutting length of the L-shaped connecting hook steel bars shall meet the anchoring welding length of the anchor rods and anchor piles, and shall be cut and processed according to the actual thickness of the existing anchor plate before installation.

[0072] Furthermore, in S3.5, the formwork includes wooden formwork and timber; the formwork is fixed by internal bracing and external tensioning during casting, with steel pipes used as main beams on the outside and steel bars welded to the structural steel bars for internal support. The longitudinal small beams of the formwork are made of timber with a spacing of no more than 150mm; the transverse main beams are made of steel pipes with a spacing of 500mm. The main beams are connected to the formwork anchor rods by butterfly clips to ensure that the formwork is installed stably.

[0073] Furthermore, in S3.8, during the concrete pouring process, after manual leveling, an immersion vibrator is used for compaction. Several vibrators are inserted in a staggered, quincunx pattern, with quick insertion and slow withdrawal. The spacing between vibrators inserted into the concrete should not exceed 1.5 times the effective radius of the vibrator, and the distance from the formwork should not be less than 1 / 2 times the effective radius of the vibrator. Vibration is performed vertically in sequence: the vibration time for a single location is 15-30 seconds, until the concrete no longer settles, and layer by layer is vibrated until no air bubbles appear and the surface begins to rise. Under-vibration, under-vibration, and over-vibration are prevented to ensure the concrete is dense. The upper layer is laid and poured before the lower layer initially sets. During vibration, the immersion vibrator is inserted 5cm into the lower layer.

[0074] Furthermore, in S3.10, the concrete curing time shall not be less than 28 days; during curing, the top of the anchor plate shall be covered with geotextile, and automatic sprinkler system shall be set up in combination with manual watering to ensure that the concrete of the anchor plate is always in a continuously moist state.

[0075] The side formwork removal only involves removing the vertical wooden formwork; the tie rods and anchor rods remain on the concrete surface for use as wall ties to fix the load-bearing supports during the concrete pouring of the rock anchor beam.

[0076] The above-mentioned construction method for an anchored plate structure in an underground powerhouse results in an anchored plate structure for an underground powerhouse.

[0077] The beneficial effects of the technical solution are:

[0078] 1. The present invention provides a construction method for an anchor plate structure for an underground powerhouse, wherein the support construction adopts a combination of mortar anchor rods, prestressed anchor cables and anchor piles, which can effectively enhance the overall stability and seismic performance of the underground powerhouse;

[0079] 2. The present invention provides a construction method for an anchor plate structure for an underground powerhouse. During the rock wall treatment process, by chiseling away the local rock wall thickness that does not meet the requirements, the concrete thickness of the anchor plate is ensured to be not less than 30cm, effectively meeting the requirements of the structural edge line.

[0080] 3. The present invention provides a construction method for an anchor plate structure for an underground powerhouse, wherein the concrete construction of the anchor plate employs precise measurement and layout and formwork installation techniques to ensure that the shape and size of the anchor plate meet the design requirements;

[0081] 4. The present invention provides a construction method for an anchor plate structure for an underground plant, wherein the silo is cleaned and inspected before concrete pouring to ensure that there are no debris or water accumulation inside the silo, and the reinforcing bars and embedded parts are also inspected to ensure the quality of concrete pouring.

[0082] 5. The present invention provides a construction method for an anchor plate structure for an underground powerhouse, wherein the curing and demolding work after concrete pouring includes water curing and continuous water spraying to keep the anchor plate concrete moist, and the end formwork is removed in a timely manner after the concrete has set, and the side formwork and bottom formwork are removed after the concrete has reached the specified strength, so as to protect and maintain the integrity of the anchor plate concrete.

[0083] 6. The present invention provides a construction method for an anchor plate structure for an underground powerhouse. After the anchor plate concrete is poured, it provides a rock platform foundation for the concrete construction of the upper rock wall crane beam, which is beneficial to the quality of the rock wall crane beam and the stability of its later operation.

[0084] In summary, the construction method provided by this invention ensures the stability, strength, and durability of the anchor plate structure for underground powerhouses built under conditions of "poor overall integrity of the surrounding rock at the factory location, weak connection between different rock layers, gaps and cracks between rock layers, and unevenness of the bedrock surface after excavation," thus guaranteeing the safety and reliability of the entire project. Attached Figure Description

[0085] Figure 1 This is a side view of the rock wall crane beam support system in an embodiment of the present invention;

[0086] Figure 2 for Figure 1 A magnified view of a portion of point A in the middle;

[0087] Figure 3 for Figure 1 A magnified view of a portion of point B in the middle;

[0088] Figure 4 This is a side view of the scaffolding erection in an embodiment of the present invention;

[0089] Figure 5 for Figure 4 A magnified view of a portion of point C in the middle;

[0090] Figure 6 This is a construction drawing of the concrete scaffolding for anchoring plates in an embodiment of the present invention;

[0091] Figure 7 This is a schematic diagram of the installation of the anchor plate casting template in an embodiment of the present invention;

[0092] The names of the corresponding labels in the attached diagram are:

[0093] Frame 1, Anchor piles 2, Anchor rods 3, Anchor plates 4, Rock wall crane beams 5, Wooden formwork 6, Templates 7, Scaffolding 8, Horizontal beams 9, Vertical beams 10, Butterfly buckles 11. Detailed Implementation

[0094] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0095] This invention uses the construction of the anchor plate of the underground powerhouse of the Jinchuan Hydropower Station on the Dadu River as a specific implementation example:

[0096] Regarding the Jinchuan Hydropower Station on the Dadu River:

[0097] The Jinchuan Hydropower Station on the Dadu River has its water diversion and power generation system located within the steep mountainside of the left bank, in a high mountain canyon area. This necessitates an underground powerhouse structure. Hydrological and meteorological statistics reveal that floods upstream of Jinchuan on the Dadu River are primarily caused by rainfall. Due to the influence of elevation, topography, and geographical location, the area upstream of Jinchuan has generally not experienced torrential rains, resulting in relatively small flood volumes. The multi-year average flood peak modulus is 0.063m. 3 / (s.km 2 The resulting flood at the dam site can be either a single-peak or double-peak process, often with a rapid rise and a slow receding process. A single flood event typically lasts 10 to 15 days, with the largest floods occurring between June and September, with July having the highest probability of occurrence, accounting for nearly half. June and September follow, with roughly equal proportions. August has the lowest probability of experiencing the largest flood due to less rainfall, far less than June. In addition, geological exploration of the plant area revealed that the rock mass is entirely composed of slightly new rock, with poor integrity and uniformity of the surrounding rock, resulting in an uneven bedrock surface after excavation.

[0098] like Figures 1 to 7 As shown, the specific construction process is as follows:

[0099] 1. Support construction

[0100] 1.1 Mortar Anchor Bolt 3

[0101] (I) Construction Procedure

[0102] A new mortar anchor rod 3 is added to the anchor plate 4. The side wall anchor rod 3 adopts the construction process of grouting first and then inserting the reinforcing bar, ensuring that the grouting density of the anchor rod 3 meets the design and specification quality requirements. The construction process is as follows:

[0103] The process involves: setting up a work platform, measuring and setting out, drilling holes, flushing (washing) holes, mechanical grouting, inserting reinforcing bars, backfilling the hole opening with mortar, fixing the hole opening, and waiting for curing protection.

[0104] (II) Construction Method

[0105] (1) Materials

[0106] ① Anchor 3: According to the requirements of the construction drawings, threaded steel bars are selected as anchor 3;

[0107] ② Cement: Ordinary Portland cement with a strength grade of not less than 42.5 shall be used;

[0108] ③ Sand: Use medium to fine sand with a maximum particle size of less than 2.5 mm and a fineness modulus between 2.4 and 2.8, and sieve it before use;

[0109] ④ Cement mortar: The mortar grade meets the requirements of the construction drawings. The strength grade of the cement mortar for grouting anchor 3 is not lower than M25; the strength grade of the cement mortar for prestressed anchor 3 is not lower than M30.

[0110] (2) Drilling

[0111] Anchor bolt hole 3 was constructed using scaffolding and a raised platform with backfill material. The spacing of anchor bolts 3, as per the construction drawings, was accurately laid out by surveyors and marked with paint on the rock surface. After the site supervisor checked that the spacing met the design requirements, they notified the workers to begin drilling. The borehole axis direction of the anchor bolts met the requirements of the construction drawings. If not specified in the drawings, the borehole axis direction of the system anchor bolts 3 was perpendicular to the excavation face, with a deviation of no more than 10cm. The angle between the borehole axis direction of the fault-reinforced anchor bolts 3 and the possible sliding surface was greater than 45°. The borehole diameter for grouting anchor bolts 3 was larger than the diameter of the anchor bolt 3, and the drill bit diameter was at least 1.5cm larger. Before grouting, the rock powder inside the hole was blown away, and any accumulated water was drained. For abandoned holes, non-shrink, dry-hard mortar was used for filling. To ensure accurate drilling angles, a light-impact, slow-drilling method was used at the beginning of drilling, repeatedly checking the drilling angles until they were accurate before proceeding at full speed. After drilling to the specified depth, use high-pressure air to blow out the debris from the hole.

[0112] (3) Installation and grouting of anchor bolt 3

[0113] Cement mortar is mixed on-site. Weighing equipment is provided on-site before grouting, and the mortar mix ratio label is placed in a conspicuous position next to the grouting machine. The mortar is mixed strictly according to the mix ratio. The mortar is mixed evenly and used immediately after mixing. The mortar mixed at one time is used up before initial setting to avoid mixing in stones and debris. Before grouting, the performance of the grouting machine is carefully checked, and the grouting pipeline is lubricated with water or thin cement slurry.

[0114] The specific steps for "grouting first and then inserting anchor bolt 3" are as follows:

[0115] A. Before grouting, cut the end of the grouting pipe into an oblique shape and mark the rock penetration depth of anchor rod 3 on the grouting pipe to check whether the grouting pipe has been sent to the bottom of the hole. When grouting, insert the grouting pipe to the bottom of the hole and then pull it out 50-100mm to start grouting. Pull out the grouting pipe slowly and evenly as the mortar is injected, so that the hole is filled with grout.

[0116] B. Rod insertion: During the processing of the insertion rod, mark the rod body with spray painting according to the designed anchorage length, and install a centering ring made of steel bars at 1 / 3 of the rod body to ensure the protection layer 3 for the anchor rod; for the permanent support anchor rod 3 with grouting first, insert the rod immediately after the hole is filled with mortar, and temporarily block the jack when inserting the rod to avoid excessive mortar overflow. When the depth of the rod body reaches the designed anchorage length (subject to the mark on the rod body), fix the anchor rod 3 with wooden wedges or other components; after the rod body is inserted, if no mortar overflows from the orifice, the cause shall be found out in time and supplementary grouting shall be carried out.

[0117] (4) Curing

[0118] For the anchor rod 3 after grouting, before the mortar strength reaches 70% of the designed strength, protect the anchor rod 3 from being knocked, collided, pulled and damaged by blasting vibration.

[0119] (III) Quality inspection of anchor rod 3

[0120] The quality of the anchor rod 3 shall be inspected 7 days after the anchor rod 3 is grouted; non-destructive testing method is adopted to detect the mortar compactness and the length of the anchor rod 3. The inspection operation zones are specified for spot inspection by the supervising engineer according to the actual site conditions, and the spot inspection proportion is as follows: for common anchor rods 3 (excluding the part at the wall crane beam 57) and prestressed anchor rods 3, spot inspection shall be carried out by operation zones, and the number of inspected anchor rods accounts for 10% of the total number of anchor rods 3.

[0121] (IV) Treatment of unqualified products

[0122] When the non-destructive testing method is adopted for anchor rod 3 length testing, the testing proportion of permanent anchor rods 3 at conventional parts shall not be less than 10% of the total number of constructed anchor rods, and no less than 10 anchor rods per single item or unit project; the testing proportion of anchor rods 3 in temporary projects is 3% of the total number of constructed anchor rods, and no less than 5 anchor rods per single item or unit project. The rod body is qualified when its length in the hole is greater than or equal to 95% of the designed length. When the spot inspection qualification rate is greater than 90%, the anchor rods 3 in the spot-inspected operation zone are considered qualified, and the unqualified anchor rods 3 detected shall be re-arranged; when the qualification rate is less than 90%, the spot inspection proportion shall be increased to 6%. If the qualification rate is still less than 90%, all anchor rods shall be detected, and the unqualified ones shall be re-arranged.

[0123] 1.2 Prestressed anchor cable

[0124] A new row of prestressed anchor cables is added on the anchor pulling plate 4, the steel anchor pier is located outside the anchor pulling plate 4, and after tensioning, end anchorage is carried out with concrete in accordance with the end anchorage design for the tail water outlet slope.

[0125] Anchor cable holes are constructed by erecting construction scaffolds and using a construction platform filled with dregs for ascending. A full-hydraulic crawler anchor cable drilling rig is adopted for hole drilling. For areas with severe hole collapse caused by broken geological zones that cannot form holes, the process of auxiliary hole forming with casing (perforated steel pipe) without pulling out the pipe is adopted. The lowering and installation of anchor cables are carried out by manual cooperation with the operation platform, and tensioning is performed by electric oil pumps and center-penetrating jacks. The technological process is as follows:

[0126] Construction preparation (anchor cable preparation, drilling rig positioning) → surveying and setting out → drilling → anchor cable installation → grouting of anchorage and tensioning sections → steel anchor pier installation → tensioning → sealing grouting → anchor head protection treatment.

[0127] Each of the above processes must pass the intermediate "three-inspection system" before proceeding to the next process.

[0128] 1.3 Anchor pile 2

[0129] (I) Fabrication of Anchor Pile 2

[0130] Anchor piles 2 are newly added to anchor plate 4, and are arranged at intervals with the system anchor rods 3 and anchor cables. Anchor piles 2 consist of 3 hot-rolled steel bars, a grout inlet pipe, and a grout return pipe, and their length meets the requirements of the design drawings.

[0131] (1) The anchor pile 2 is extended by using a threaded sleeve connection;

[0132] (2) The adjacent steel bars of anchor pile 2 are connected by electric welding with a spacing of 150cm, and the weld height meets the specification requirements;

[0133] (3) If steel pipes are used for the grouting pipes of anchor pile 2, the steel pipes shall be welded to the adjacent reinforcing bars every 150cm.

[0134] (4) To ensure that the anchor pile 2 is centered in the hole, a ring of centering steel bars (φ10, 10cm long) is set on the anchor pile body every 200cm, and is welded to the anchor pile body steel bars.

[0135] (II) Construction of Anchor Pile 2

[0136] Anchor pile 2 is constructed using a process of inserting the anchor rod first and then grouting. The process flow is as follows:

[0137] Measurement and positioning → Drilling rig positioning → Hole drilling → Hole washing (flush) → Installation of anchor pile 2 → Cement mortar pouring.

[0138] (1) Drilling and cleaning the hole

[0139] 1) The anchor pile 2 is constructed by erecting a construction scaffold and filling the construction platform with slag for climbing. The anchor pile 2 is drilled by an anchor drilling machine with a hole diameter of not less than 90mm.

[0140] 2) The allowable deviation for the spacing of anchor pile 2 holes is 100cm, and the allowable deviation for the hole depth is ±50mm. The hole axis direction of anchor pile 2 should be perpendicular to the bedrock surface. When the angle between the drilling direction and the obviously existing structural surface is small, adjust the direction of some anchor piles 2 to make the angle between them larger;

[0141] 3) The diameter of the drill bit for grouting anchor pile 2 should be at least 2.5 cm larger than the diameter of anchor pile 2;

[0142] 4) Special combination drilling tools (eccentric drill bits, etc.) are used for rock masses with developed fractures to ensure hole formation;

[0143] 5) After drilling is completed, use compressed air to blow the rock cuttings out of the hole and temporarily seal the hole opening to prevent foreign objects from falling into the hole.

[0144] (2) Installation procedure for anchor pile 2

[0145] 1) Before the anchor pile 2 is manufactured and processed, the steel bars are straightened, rust removed and dirt removed;

[0146] 2) Before installation, check the cleaning of the anchor pile holes to remove accumulated water and rock powder;

[0147] 3) The anchor piles 2 are installed using a combination of truck crane and truck-mounted crane, and manually; one pile is installed and grouted after drilling is completed.

[0148] (III) Installation and Grouting of Anchor Pile 2

[0149] (1) The cement mortar mix ratio for grouting anchor pile 2 shall be selected by test within the following specified range:

[0150] Cement:Sand, 1:1 to 1:2 (by weight); Cement:Water, 1:0.38 to 1:0.45 (by weight);

[0151] The aggregate in the cement mortar for anchor bolt 3 is medium and fine sand with a maximum particle size of less than 2.5mm. It should be screened and cleaned before use. The cement mortar should be mixed evenly to prevent stones or other impurities from being mixed in. It should be used immediately after mixing and should be used up before initial setting.

[0152] (2) The installation and grouting of anchor pile 2 shall be carried out in the presence of the supervisor. The anchor pile 2 shall be cleaned and grouting shall be carried out only after inspection by the supervisor.

[0153] (3) For anchor pile 2, the anchor pile 2 and grouting system should be installed first, and grouting should be carried out immediately. The grouting system must meet the design requirements. Before grouting, the rock powder in the hole should be blown clean and the accumulated water should be drained.

[0154] (4) The grouting pipe of anchor pile 2 is firmly fixed to anchor pile 2 and kept unobstructed. It is inserted into the hole along with the reinforcing bar, with the grouting pipe 20cm away from the bottom of the hole. For anchor pile 2 with a depression angle of less than 30°, an exhaust pipe needs to be installed and the hole opening needs to be sealed before grouting. Grouting can only be stopped when the exhaust pipe discharges grout or no longer discharges grout.

[0155] (5) After the anchor pile 2 is grouted, the anchor rod 3 shall not be knocked, bumped or pulled before the mortar solidifies.

[0156] (6) Anchor piles 2 that are not grouted or are only sealed with mortar at the borehole opening are considered as waste anchor piles 2.

[0157] 2. Rock wall treatment

[0158] Due to the poor overall condition of the surrounding rock of the underground powerhouse, the measured data of the rock platform of the rock wall crane beam 5 and the vertical wall below the lower inflection point show that the geological over-excavation is large. The minimum thickness of the anchor plate 4 shall not be less than 30cm. If the thickness of the anchor plate 4 in some areas is ≤30cm, the shotcrete and rock wall shall be manually removed according to the actual situation to ensure that the concrete thickness of the anchor plate 4 is 30cm and meets the structural boundary line.

[0159] 3 Anchor plate 4 Concrete construction

[0160] 3.1 Base surface cleaning and acceptance

[0161] Manually remove loose stones, wall base debris, and accumulated materials within the concrete pouring area of ​​the anchor plate 4. For areas with insufficient excavation, use manual labor in conjunction with pneumatic picks to treat them until they meet the requirements. Use a high-pressure water gun to wash the rock surface to ensure that the rock surface is clean and moist, without any under-excavation or loose rocks before the foundation can be accepted.

[0162] 3.2 Measurement and Setting Out

[0163] Accurate measurement and layout were carried out using total station and level instruments. The control points such as the station number and elevation of the lower anchor plate 4 of the rock wall crane beam 5 were marked in obvious fixed positions. Elevation points were also marked in places that were easy to measure to determine the reinforcement binding, formwork edge line and beam top elevation. Conspicuous markings and protective measures were also taken.

[0164] 3.3 Frame 1 Erection

[0165] The construction scaffolding is erected using standard socket-type disc-lock steel pipe supports, arranged in two rows; the entire anchor plate is deployed at once, and the entire working face is erected in one go.

[0166] Construction scaffold 1 serves as a concrete pouring platform, with a row spacing of 120cm x 120cm and a step distance of 150cm. A standard safety rotating ladder, custom-made and assembled on-site, is installed every 50m along the outer side of construction scaffold 12 for personnel access.

[0167] To ensure the safety and operation of construction workers, the construction platform is fully covered with double-layered bamboo planks 8, which are then tied to the steel pipe scaffolding with wire to prevent slippage. Safety netting is installed on the exposed surfaces of the scaffolding 1 and ladders to guarantee the safety of construction workers.

[0168] 3.4 Reinforcement Engineering

[0169] (I) Reinforcing steel fabrication and transportation

[0170] The steel bar processing procedure is as follows: steel bar identification → layout → inspection → cutting → bending → finished sample → numbering.

[0171] The steel bars are cut according to the construction drawings by on-site technicians, and the processing plant cuts and processes them according to the steel bar material list, and stacks them according to their numbers and labels. The surface of the steel bars should be clean and undamaged. Paint contamination and rust should be removed before use. Steel bars with granular or flaky old rust should not be used. The semi-finished steel bars are loaded and unloaded by crane, transported to the construction site by flatbed truck, and then manually moved to the work area, and neatly arranged according to the type and model of the steel bars.

[0172] (II) Reinforcing Steel Installation

[0173] The anchor plate reinforcement bars are tied and installed according to the compartmentalization diagram and the planned segmented and compartmentalized construction sequence.

[0174] The welding of the reinforcing bars is completed off-site, and they are then transported to the site for direct installation. Reinforcing bar connections are made by welding, and the joint area within the same connection section should not exceed 50%. The lap length is constructed according to design requirements and relevant specifications. The construction of the anchor plate concrete reinforcement includes reinforcing bar processing, transportation, and installation. Before binding the reinforcing bars, the positions of each embedded part are first surveyed and marked on the rock platform. The reinforcing bars should be staggered from the positions of the embedded parts as much as possible at these locations.

[0175] The installation of reinforcing bars follows the principles of "bottom to top (i.e., bottom first, then top), inside to outside (i.e., first tie the reinforcing bars on the side closest to the rock wall, then tie the reinforcing bars on the side furthest from the rock wall), bending first, then straightening, with clear layers and mutual coordination." Construction scaffolding is used for tying and welding the concrete reinforcing bars of the anchor plates; the joints of the stressed reinforcing bars are staggered; and the reinforcement is strung, spaced, placed, tied, and spot-welded according to the design drawings and survey points.

[0176] When welding longitudinal and circumferential reinforcing bars, the joints should be staggered, and the reinforcing bars should pass through construction joints. If the reinforcing bars are welded and lapped, the lap length should not be less than 5d when welding on both sides, and not less than 10d when welding on one side. The stagger between adjacent welds should not be less than 35d. The outer reinforcing mesh of the anchor plate 4 and the exposed ends of the system anchor rods 3 and anchor piles 2 (60cm of exposed end has been reserved) are firmly welded with L-shaped connecting hook reinforcing bars. When the connecting hook reinforcing bars are welded to the outer mesh of the anchor plate 4 and the exposed ends of the anchor rods 3 and anchor piles 2, the length of the weld on both sides should not be less than 15cm. The cutting length of the L-shaped connecting hook reinforcing bars should be sufficient to meet the anchoring welding length of the anchor rods 3 and anchor piles. The bars should be cut and processed according to the actual thickness of the anchor plate 4 before installation. If the thickness of the anchor plate 4 is less than 60cm but greater than 30cm, the excess exposed portion of the anchor rods 3 and anchor piles 2 should be cut off before connecting with the outer reinforcing mesh of the anchor plate 4 using L-shaped connecting hook reinforcing bars.

[0177] 3.5 Template 7 Installation

[0178] For the concrete pouring of anchor plate 4, use wooden formwork 6 + timber. Before installing formwork 7, set concrete pads on the inside of formwork 7 at intervals of 1-2m according to the position of the structural line, and clean the surface of formwork 7 and apply release agent.

[0179] The formwork 7 is fixed by internal bracing and external tensioning during pouring. Steel pipes are used as horizontal beams 9 on the outside, and steel bars are welded to the structural steel bars for internal support. The longitudinal direction of the formwork 7 is vertical beams 10 made of square timber with a spacing of no more than 150mm. The transverse horizontal beams 9 are made of steel pipes with a spacing of 500mm. The horizontal beams 9 are connected to the formwork anchor rods by butterfly clips 11 to ensure that the formwork 7 is installed firmly.

[0180] 3.6 Inventory Clearance and Acceptance

[0181] Before pouring concrete, clean up the debris in the sump, rinse it clean, remove any accumulated water, and check whether the reinforcing bars and embedded parts meet the design and specification requirements. The construction joint surface and keyway surface should be roughened and rinsed clean with water before pouring concrete. After passing self-inspection, re-inspection, and final inspection, apply for supervision and acceptance. After the site supervision engineer approves the application, prepare for concrete placement.

[0182] 3.7 Concrete Transportation

[0183] The concrete for the rock wall crane beam 5 is produced and supplied by the concrete mixing system located at Deshengtai on the left bank. If the Deshengtai concrete mixing system suddenly malfunctions and cannot supply normally, the concrete for the rock wall crane beam 5 will be temporarily supplied by the mixing plant in the temporary construction area on the left bank or the mixing plant at the flood discharge point to ensure continuous operation of the lining concrete pouring and the completion of continuous pouring of the same section. Horizontal transportation of concrete is carried out by concrete mixer trucks to the working face, and vertical transportation is carried out by concrete pumping units (sky pumps) to the formwork, followed by compaction with immersion vibrators.

[0184] 3.8 Concrete Pouring

[0185] To reduce heat of hydration and minimize concrete cracking, normal-state concrete was used. For the lower anchor plate of the rock wall crane beam 5, a concrete pump was used as the primary means of placement, supplemented by a crane-lifted container. Concrete placement avoided the system support structure and structural reinforcement as much as possible. The placement process was cyclical, and a medium-thin layer method was used for layered pouring. The anchor plate 4 concrete was poured according to a segmented and compartmentalized plan, with each segment poured in layers from bottom to top. The layer thickness was controlled between 30 and 40 cm. A self-made sheet metal chute was used for loading and unloading, controlling the concrete placement height and preventing segregation. After manual leveling, immersion vibrators were used for compaction. Two vibrators were inserted twice in a staggered, quincunx pattern, with quick insertion and slow withdrawal. The spacing between vibrators should not exceed 1.5 times the effective radius of the vibrator, and the distance from the formwork 7 should not be less than 1 / 2 times the effective radius of the vibrator. Minimum contact with reinforcement and embedded parts was avoided; manual compaction was used when necessary. Vibration should be performed vertically and sequentially in the concrete. The vibration time for a single location should be 15–30 seconds, continuing until the concrete stops settling. Vibrate layer by layer until no air bubbles appear and the surface begins to show signs of cement paste. Avoid under-vibration, insufficient vibration, or over-vibration to ensure the concrete is dense. The next layer should be laid and poured before the initial setting of the layer below. When vibrating, the immersion vibrator should be inserted 5 cm into the layer below.

[0186] 3.9 Closing and smoothing

[0187] After the concrete pouring is completed, organize manual leveling in a timely manner. After leveling, the anchor plate should be flat and the elevation should be accurate. Before the initial setting of the concrete after the elevation is completed, embed reinforcing bars in the joint surface according to the drawings.

[0188] 3.10 Concrete curing and demolding

[0189] Water curing begins 12-18 hours after concrete pouring and placement. After the side and end forms are removed, the lower anchor plate 4 of the rock wall crane beam 5 is continuously sprayed with water for curing, ensuring the concrete of the anchor plate 4 remains constantly moist. The curing time is generally no less than 28 days. During curing, the top of the anchor plate 4 is covered with geotextile fabric, and automatic sprinklers are used in conjunction with manual watering to ensure the concrete of the anchor plate 4 remains continuously moist.

[0190] The head formwork 7 can be removed after the concrete has set. The side formwork should be removed after the concrete has reached 75% strength, and the bottom formwork should be removed after it has reached 100% of the concrete design strength according to specifications. Only the vertical wooden formwork 6 is removed when removing the side formwork. The tie rods and anchor rods are left on the concrete surface for fixing the load-bearing support during the concrete pouring of the rock anchor beam.

[0191] 3.11 Protection of Molded Concrete

[0192] (1) Protection against flying debris from blasting

[0193] To prevent damage to the concrete of the anchor plate 4 from impacts by flying rocks from the blasting of the lower layer, after the formwork 7 is removed, wooden formwork 6, bamboo planks, and waste tires are used for covering and protection. The bamboo planks are connected by wire to the exposed steel bars at the top and bottom of the anchor plate 4. A steel reinforcement frame is installed every 1.5m on the outside to prevent the bamboo planks 8 and waste tires from slipping. To prevent damage to the concrete of the anchor plate 4 from the swaying steel bars, rubber gaskets are placed between the wire and the edges of the anchor plate 4. After the blasting, any damaged bamboo planks are promptly repaired to ensure that the concrete of the anchor plate 4 is not damaged.

[0194] (2) Control of vibration velocity of blasting particles

[0195] To control the damage caused by blasting vibration to the newly poured anchor plate 4 concrete, no excavation or blasting of the surrounding rock is allowed during the pouring of anchor plate 4. Excavation of the surrounding rock can only be carried out after the concrete of anchor plate 4 has reached its design strength at 28 days of age, and the vibration velocity during excavation should be less than 7 cm / s, as detailed in Table 1.

[0196] Table 1 Safety particle vibration velocity on freshly poured concrete foundation surface

[0197] Safe particle vibration velocity (cm / s) Cannot be shaken 3.0 7.0

[0198] The above method was used to complete the construction of the underground powerhouse anchor plate of the Jinchuan Hydropower Station on the Dadu River. The resulting underground powerhouse anchor plate structure is stable, provides good support for the powerhouse, and is beneficial to the quality and load-bearing capacity of the rock wall crane beam.

[0199] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A construction method for an anchored plate structure used in an underground powerhouse, characterized in that, Includes the following steps: S1, Support Construction S1.1 Mortar Anchor Bolt Construction Mortar anchors are added to the anchor plate. The side wall anchors adopt the construction process of grouting first and then inserting reinforcement bars. The construction process is as follows: setting up a working platform, surveying and setting out, drilling, flushing the hole, mechanical grouting, inserting reinforcement bars, backfilling the hole with mortar, fixing the hole, and waiting for curing protection. S1.2 Prestressed Anchor Cable Construction Prestressed anchor cables are added to the anchor plate, and steel anchor piers are located outside the anchor plate. After tensioning, concrete is used to seal the anchor. The construction process is as follows: construction preparation, surveying and setting out, drilling, anchor cable installation, grouting of the anchoring and tensioning sections, installation of steel anchor piers, tensioning, sealing and grouting, and anchor head protection treatment. S1.3 Anchor Pile Construction Anchor piles are added to the anchor plate and arranged at intervals with the system anchor rods and anchor cables. The construction process is as follows: measurement and positioning: drilling rig positioning, hole drilling, hole flushing or hole washing, installation of anchor piles, and grouting of cement mortar. S2, Rock Wall Treatment The minimum thickness of the anchor plate is required to be no less than 30cm. If the local anchor plate thickness is less than 30cm, the shotcrete and rock wall should be manually removed according to the actual situation to ensure that the anchor plate concrete is 30cm thick and meets the structural edge line. S3, Anchor Plate Concrete Construction S3.1 Base surface cleaning and acceptance Remove loose stones, wall base debris, and accumulated materials from the concrete pouring area of ​​the anchor plate to ensure that the rock surface is clean and moist, without under-excavation or loose rock before foundation acceptance. S3.2 Measurement and Setting Out Use a total station or level to conduct precise measurement and layout, mark the station number and elevation control points of the anchor plate shape of the lower part of the rock wall crane beam in a clear and fixed position, and mark the elevation points in a place that is easy to measure, determine the reinforcement binding, formwork edge line and beam top elevation, and make conspicuous marks and protective measures. S3.3 Frame Erection The construction scaffolding is erected using standard socket-type disc-lock steel pipe supports, with all anchor plates deployed at once, and the entire working surface is erected in one go. S3.4 Reinforcement Construction After the anchor plate reinforcement is fabricated off-site, it is tied and installed according to the compartmentalization diagram of the underground plant and the planned segmented and compartmentalized construction sequence. S3.5 Template Installation Before installing the formwork, set concrete pads on the inside of the formwork at intervals according to the position of the structural line, and clean the formwork surface and apply release agent; S3.6 Clearance Inspection Before pouring concrete, clean up the debris in the sump, rinse it clean, remove any accumulated water, and inspect the reinforcing bars and embedded parts. The surface of the construction joint and the keyway should be roughened and rinsed clean with water before pouring concrete. After passing self-inspection, re-inspection, and final inspection, the concrete should be put into the sump. S3.7 Concrete Transportation Concrete is transported horizontally to the work site using concrete mixer trucks, and vertically transported using concrete pumps and compacted using immersion vibrators. S3.8 Concrete Pouring Normal concrete was used. For the anchor plate concrete under the rock wall crane beam, a concrete pump was used as the main means of placement, with a crane bucket used as an auxiliary means. The concrete was poured in thin layers using a flat-laying method. The anchor plate concrete was poured in sections according to the segmented and compartmentalized plan. Each section was poured in layers from bottom to top, with each layer being 30-40cm thick. A self-made sheet metal chute was used to extend into the compartment for loading and unloading, controlling the concrete pouring height and preventing segregation. S3.9 Finishing and smoothing After the concrete is poured, level the surface in a timely manner. After leveling, the top of the anchor plate should be flat and the elevation should be accurate. Before the initial setting of the concrete after the elevation is completed, insert reinforcing bars into the joint surface as required. S3.10 Concrete curing and demolding Water curing should begin 12 to 18 hours after concrete pouring and placement; after the side and end forms are removed, the lower anchor plate of the rock wall crane beam should be continuously sprayed with water and cured to ensure that the concrete of the anchor plate remains continuously moist. The head formwork is removed after the concrete has set, the side formwork is removed after the concrete has reached 75% strength, and the bottom formwork is removed after the concrete has reached 100% of its design strength according to specifications. S3.11 Protection of Molded Concrete When the anchor plate is being poured, the surrounding rock must not be excavated or blasted; the excavation of the surrounding rock can only be carried out after the concrete strength of the anchor plate has reached the design strength at 28 days, and the vibration velocity of the blasting safe mass point is less than 7 cm / s. After the formwork is removed, wooden formwork, bamboo planks, and waste tires are used to cover and protect it. After the blasting, the damaged bamboo planks are repaired in time to ensure that the concrete of the anchor plate is not damaged. In S1.1, the construction steps for mortar anchor bolts are as follows: S1.1.1 Material preparation: Anchor rods are threaded steel bars; cement is ordinary Portland cement with a strength grade of not less than 42.5; sand has a maximum particle size of less than 2.5mm and a fineness modulus between 2.4 and 2.8, and is sieved before use; cement mortar has a strength grade of not less than M25; the cement mortar for prestressed anchor rods has a strength grade of not less than M30. S1.1.2 Drilling: Anchor bolt holes are drilled by erecting scaffolding and using a construction platform with slag filling. The hole position deviation is no more than 10cm. The angle between the hole axis of the fault-reinforced anchor bolt and the possible sliding surface is greater than 45°. After drilling to the specified depth, the hole is blown with high-pressure air to remove debris. Before grouting, the rock powder in the hole is blown clean and the accumulated water is drained. S1.1.3 Anchor bolt installation and grouting: Cement mortar is mixed on site, and the construction is carried out by "grouting first and then inserting anchor bolts"; S1.1.4 Maintenance: After grouting, the anchor rod shall be protected from being hit, collided, pulled out and damaged by blasting vibration before the mortar strength reaches 70% of the design strength. S1.1.5 Anchor bolt quality inspection: 7 days after anchor bolt grouting, non-destructive testing methods are used to inspect the mortar density and anchor bolt length. S1.1.6 Handling of non-conformities: The length ratio of anchor bolts shall be tested using non-destructive testing methods. The testing ratio of permanent anchor bolts in conventional locations shall not be less than 10% of the total number of anchor bolts constructed. The length of the bolt inside the hole shall be greater than or equal to 95% of the design length to be considered qualified. Specifically, in S1.1.3, the method of "grouting first and then inserting anchor bolts" is as follows: Before grouting, the end of the grouting pipe is cut into an oblique shape, and a mark is made on the grouting pipe according to the rock penetration depth of the anchor rod to check whether the grouting pipe has been sent to the bottom of the hole; during grouting, the grouting pipe is inserted to the bottom of the hole, and then pulled out 50-100mm to start grouting; the grouting pipe is slowly and evenly pulled out as the mortar is injected, so that the hole is filled with grout. During the fabrication of the anchor rods, the designed anchorage length is marked on the rod body with spray paint, and a centering ring made of steel bars is installed at 1 / 3 of the rod body to ensure the protective layer of the anchor rod. Permanent support anchor rods with pre-grouting are used. After the mortar in the hole is filled, the rod is inserted immediately. The insertion hole is temporarily sealed during insertion to prevent excessive mortar overflow. When the rod body depth reaches the designed anchorage length, the anchor rod is fixed. If no mortar overflows from the hole after the rod body is inserted, the cause should be found and replenished in time. In S1.1.6, when the pass rate of the spot check is greater than 90%, the anchor bolts in the spot check work area are qualified, and the anchor bolts that are found to be unqualified are re-laid; when the pass rate is less than 90%, the spot check ratio is increased first. If the pass rate is still less than 90%, all anchor bolts are checked and the unqualified anchor bolts are re-laid. In S1.3, the construction steps for anchor piles are as follows: S1.3.1 Fabrication of anchor piles: Anchor piles are composed of multiple hot-rolled steel bars, grout inlet pipes, and grout return pipes; S1.3.2 Drilling and cleaning: Anchor drilling rigs are used for drilling; after drilling is completed, pressurized air is used to blow out the rock cuttings from the hole, and the hole opening is temporarily sealed to prevent foreign objects from falling into the hole; S1.3.3 Anchor pile installation and grouting The construction method involves first inserting anchor piles and grouting system, and then immediately grouting. Truck cranes and truck-mounted cranes are used in conjunction with manual installation. After drilling, one pile is installed and grouted at a time. Specifically, in S1.3.1, the specific method for fabricating anchor piles is as follows: Before fabricating the anchor piles, the reinforcing bars are straightened, rusted, and cleaned. The anchor piles are spliced ​​using threaded sleeves. Adjacent reinforcing bars of the anchor piles are connected by electric welding at 150cm intervals. The grout inlet and outlet pipes of the anchor piles are made of steel pipes, which are connected to adjacent reinforcing bars by electric welding at 150cm intervals. To ensure that the anchor piles are centered in the hole, a ring of centering reinforcing bars is set every 200cm on the anchor pile body and welded to the reinforcing bars of the anchor pile body. In S1.3.2, the drilling of anchor piles is carried out by erecting scaffolding and constructing a platform for filling with slag; the diameter of the drill bit is more than 2.5cm larger than the diameter of the anchor pile, the hole diameter is not less than 90mm, the allowable deviation is 100cm, and the allowable deviation of the hole depth is ±50mm; the hole axis is perpendicular to the bedrock surface. When the angle between the drilling direction and the obvious structural surface decreases, the direction of some anchor piles is adjusted to increase the angle between them. For rock masses with developed fissures, special combination drilling tools are used to ensure hole formation. Before installing anchor piles, check the cleaning of the anchor pile holes to remove accumulated water and rock powder; before grouting, blow away the rock powder in the holes and drain the accumulated water; after grouting, do not knock, bump or pull the anchor rods before the mortar solidifies; anchor piles that have not been grouted or that are only sealed with mortar at the hole opening are considered waste anchor piles. The cement mortar used for anchor pile grouting has a cement-to-sand weight ratio of 1:1 to 1:2 and a cement-to-water weight ratio of 1:0.38 to 1:0.

45. The aggregate is medium and fine sand with a maximum particle size of less than 2.5 mm. It is screened and cleaned before use. The cement mortar is mixed evenly to prevent stones or other impurities from being mixed in. It is mixed and used immediately and used up before initial setting. The method for grouting anchor piles is as follows: the grouting pipe is firmly fixed on the anchor pile and kept unobstructed, and is inserted into the hole along with the reinforcing bar. The grouting pipe is 20cm away from the bottom of the hole. For anchor piles with a depression angle of less than 30°, an exhaust pipe needs to be installed, and the hole opening needs to be sealed before grouting.

2. The construction method for an anchored plate structure for an underground powerhouse according to claim 1, characterized in that, In S1.2, the anchor cable holes are constructed by erecting scaffolding and filling the construction platform with slag for climbing, and the hydraulic crawler anchor cable drilling rig is used for drilling. For areas with severe geological collapse and where drilling is impossible, the pipe-assisted drilling process without pipe removal is adopted.

3. The construction method for an anchored plate structure for an underground powerhouse according to claim 1, characterized in that, In S3.3, the scaffolding is constructed using a custom-made product assembly method on-site. The scaffolding serves as a platform for concrete pouring, with its surface fully covered by double-layered bamboo planks. The bamboo planks are then tied to the steel pipe scaffolding with wire to prevent slippage. The spacing between uprights is 120cm x 120cm, and the step distance is 150cm. A standard safety rotating ladder is installed every 50m on the outside of the scaffolding for personnel to access the site. Safety nets are hung on the exposed surfaces of the scaffolding and ladders to ensure the safety of construction workers.

4. The construction method for an anchored plate structure for an underground powerhouse according to claim 1, characterized in that, In S3.4, the steps for rebar installation are as follows: S3.4.1 Rebar processing and transportation: The rebar processing process is as follows: rebar identification, layout, inspection, cutting, bending, finished sample, numbering; the surface of the rebar after processing is clean and undamaged, and paint pollution and rust are cleaned before use. Rebar with granular or flaky old rust shall not be used. The pre-processed steel bars are loaded and unloaded by crane, transported to the construction site by flatbed truck, and then manually moved to the work surface and neatly arranged according to the type and model of the steel bars. S3.4.2 Reinforcing bar installation: Welding of the reinforcing bars is completed off-site, and they are transported to the site for direct installation. Before binding and installing the reinforcing bars, the positions of each embedded part are marked on the rock platform by surveying and marking. The reinforcing bars are staggered from the positions of the embedded parts at this point. The installation of the reinforcing bars follows the principles of "bottom to top, i.e., bottom first and then top; inside to outside, i.e., binding the reinforcing bars on the side closest to the rock wall first and then binding the reinforcing bars on the side furthest from the rock wall; bending first and then straightening, with clear layers and mutual coordination." The joints of welded steel bars shall meet the requirement that the joint area within the same connection section does not exceed 50%, and the lap length shall be constructed according to the design requirements and relevant specifications. Among them, when welding the joints of longitudinal steel bars and circumferential steel bars, the joints shall be staggered and the steel bars shall pass through the construction joint. The steel mesh on the outer side of the anchor plate shall be firmly welded to the exposed ends of the system anchor rods and anchor piles using L-shaped connecting hook steel bars. When the connecting hook steel bars are welded to the exposed ends of the steel mesh on the outer side of the anchor plate and the anchor rods and anchor piles, the length of the weld on both sides shall not be less than 15cm. The cutting length of the L-shaped connecting hook steel bars shall meet the anchoring welding length of the anchor rods and anchor piles, and shall be cut and processed according to the actual thickness of the existing anchor plate before installation.

5. A construction method for an anchored plate structure for an underground powerhouse according to claim 1, characterized in that, In S3.5, the formwork includes wooden formwork and timber. The formwork is fixed by internal bracing and external tensioning. Steel pipes are used as main beams on the outside, and steel bars are welded to the structural steel bars for internal support. The longitudinal small beams of the formwork are made of timber with a spacing of no more than 150mm. The transverse main beams are made of steel pipes with a spacing of 500mm. The main beams are connected to the formwork anchor rods by butterfly clips to ensure that the formwork is installed firmly.

6. The construction method for an anchored plate structure for an underground powerhouse according to claim 1, characterized in that, In S3.8, during concrete pouring, after manual leveling, an immersion vibrator is used for compaction. Several vibrators are inserted in a staggered, quincunx pattern, with quick insertion and slow withdrawal. The spacing between vibrators inserted into the concrete should not exceed 1.5 times the effective radius of the vibrator, and the distance from the formwork should not be less than 1 / 2 times the effective radius of the vibrator. Vibration should be performed vertically in sequence: the vibration time for a single location should be 15-30 seconds, until the concrete stops settling, and layer by layer should be vibrated until no air bubbles appear and the surface begins to rise. Under-vibration, under-vibration, and over-vibration should be avoided to ensure the concrete is dense. The upper layer is poured before the lower layer initially sets. During vibration, the immersion vibrator should be inserted 5cm into the lower layer.

7. A construction method for an anchored plate structure for an underground powerhouse according to claim 1, characterized in that, In S3.10, the concrete curing time shall not be less than 28 days. During curing, the top of the anchor plate shall be covered with geotextile, and automatic sprinkler system shall be set up in combination with manual watering to ensure that the concrete of the anchor plate is always in a continuously moist state. The side formwork shall be removed only when the vertical wooden formwork is removed. The anchor rods and tie rods shall be left on the concrete surface for the wall connection and fixation of the load-bearing support when the rock anchor beam concrete is poured.

8. The underground powerhouse anchor plate structure obtained by the construction method of the anchor plate structure for underground powerhouse according to any one of claims 1 to 7.

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