Method for enabling tunnel to pass through building based on drilling and blasting method

Abstract

The invention belongs to the technical field of tunnel construction, and particularly relates to a method for enabling a tunnel to penetrate through a building based on a drilling and blasting method. The method mainly comprises the following steps: carrying out advanced geological forecast through a seismic wave method to predict changes of geological conditions and rock characteristics in a certain range in front; a monitoring position is arranged in a tunnel, and manual observation, a convergence gauge, a total station and a level gauge are used for monitoring changes inside and outside the tunnel, clearance changes and vault sinking conditions; seepage monitoring is carried out; excavation is carried out step by step according to the construction sequence of a step method and a three-step seven-step method; the excavated tunnel is subjected to anchor rod supporting and advance supporting, when the buried depth of the tunnel is within a preset threshold value, ground surface grouting is adopted, and when the buried depth is larger than the preset threshold value, a curtain grouting and radial grouting method after excavation is adopted for water plugging. When the underground water volume is large and is confined water, a primary support and a secondary lining structure should be reinforced, ground surface settlement is reduced, and construction safety is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of tunnel construction, and in particular relates to a method for tunneling through a building based on the drill-and-blast method. Background Art

[0002] The drill-and-blast method, a construction method that excavates rock by blasting and charging explosives through drill holes, is widely used in rock excavation projects for underground structures. The drill-and-blast method offers advantages such as strong adaptability, operational flexibility, and cost-effectiveness. It is suitable for a variety of tunnel cross-sections, including single-track, double-track, and multi-track stations. The construction cross-section can be adjusted as needed, thus reducing space waste.

[0003] When drilling and blasting through buildings, the construction requirements vary due to different rock hardness and stratum structure requirements. To ensure that the tunnel can safely pass through the building, surface subsidence must be strictly monitored during construction and the tunnel must be safely supported.

[0004] Therefore, how to accurately and effectively monitor and support tunnels constructed using the drill and blast method to improve the safety of tunnel construction has become an urgent problem that needs to be solved. Summary of the Invention

[0005] The present application provides a method for tunneling through buildings based on the drill and blast method, which accurately and effectively monitors and supports tunnels constructed using the drill and blast method, thereby improving the safety of tunnel construction.

[0006] In the first aspect, an embodiment of the present application provides a method for tunnel crossing a building based on the drilling and blasting method, the method comprising: predicting the rock formation characteristics within a preset range in front of the tunnel; setting a monitoring position in the tunnel, and monitoring the vault subsidence data inside and outside the tunnel by means of a convergence meter, a total station and a level; using a piezometer to determine the seepage rate based on the flow rate and a preset method; supporting the outside of the tunnel by grouting and anchor rods; before excavation, performing advance support by means of an advance small guide tube combined with small guide tube grouting; determining the excavation method based on the rock formation characteristics, excavating the tunnel, and crossing the building.

[0007] In one possible implementation, when a water-rich tunnel section is encountered during tunnel excavation, the method further includes: when the tunnel burial depth is within 20m, surface grouting is adopted; when the burial depth is greater than 20m, curtain grouting and radial grouting after excavation are adopted; when a broken tunnel section is encountered during tunnel excavation, the method further includes: determining the installation position of the grouting steel flower pipe; grouting is performed based on the installation position of the grouting steel flower pipe, using pure cement slurry for grouting, and grouting is performed in two times, the initial grouting pressure is 1MPa, and the final pressure should be stable at 2MPa.

[0008] In one possible implementation, before the excavation, advance support is performed by using an advance small catheter combined with small catheter grouting, including: the advance small catheter is evenly arranged along the excavation line of the tunnel arch, with a spacing of 30-50 cm; the grouting sequence is from bottom to top, and when string holes occur, a grouting device is used for multi-hole grouting or blocking the string holes for grouting; when the pressure reaches the preset grouting final pressure and stabilizes for 10-15 minutes, and the grouting volume reaches more than 80% of the preset grouting volume, the grouting is terminated; when the grouting pressure fails to reach the preset final pressure, but the grouting volume has reached the preset grouting volume and there is no leakage, the grouting is terminated.

[0009] In one possible implementation, the method for predicting the rock formation characteristics within a preset range in front of the tunnel includes a seismic wave method and an advance horizontal drilling method; the seismic wave method predicts the rock formation characteristics within a preset range in front of the tunnel by determining the position of the impact point and the sensor of the position of the impact point; the advance horizontal drilling method obtains the front rock core through drilling; and determines the rock formation characteristics within the preset range in front based on the front rock core.

[0010] In one possible implementation, monitoring positions are set in the tunnel to monitor the vault subsidence data inside and outside the tunnel using a convergence meter, a total station, and a level, including: the spacing between the monitoring positions is determined according to the rock formation characteristics, the tunnel burial depth, and the excavation method; the spacing between the monitoring positions and the tunnel face meets a preset distance;

[0011] The reading of the vault subsidence data is completed within 3 to 6 hours when the data occurs.

[0012] In one possible implementation, the preset method includes a volumetric method, a weir method, and a flow rate method. The piezometer is used to determine the seepage rate based on the flow rate and the preset method, including: using the volumetric method when the flow rate is less than 1 L / s; using the weir method when the flow rate is between 1 and 300 L / s; when the flow rate is greater than 300 L / s or the weir cannot be set, the leakage water is introduced into the drainage ditch and the flow rate method is used.

[0013] In one possible implementation, the supporting outside the cave by grouting and anchor rods includes: drilling holes in the rock surface using an anchor drill or a handheld pneumatic rock drill, with the hole positions being perpendicular to the rock surface; supporting the outside of the cave based on the hole positions and a preset support sequence, and the support sequence includes grouting first and then inserting anchor rods, and inserting rods first and then grouting.

[0014] In a possible implementation, the excavation method includes an up-and-down step method and a three-step seven-step method.

[0015] In a possible implementation, the curtain grouting includes: arranging holes in the water-rich tunnel section; drilling holes first and then grouting at the hole arrangement positions using a segmented forward method, drilling and grouting one section at a time.

[0016] In one possible implementation, when a tunnel has been excavated and the support is damaged, reinforcement is carried out inside the tunnel. The reinforcement method includes: installing locking anchor rods to reinforce steel supports, adding concrete arches, installing φ40 steel flower pipes for grouting reinforcement in a circumferential direction, and installing self-drilling long anchor rods for grouting.

[0017] This application predicts the rock formation characteristics within a preset range in front of the tunnel; sets up monitoring positions in the tunnel, and monitors the vault subsidence data inside and outside the tunnel using convergence meters, total stations, and levels; uses a piezometer to determine the seepage rate based on the flow rate and a preset method; supports the outside of the tunnel through grouting and anchors; before excavation, performs advance support through a combination of a small lead pipe and small lead grouting; determines the excavation method based on the rock formation characteristics, excavates the tunnel, and passes through the building. A method for tunneling through a building using the drill and blast method is systematically designed. Compared with the prior art of tunnel excavation and passing through buildings based on experience, this application sets up multiple monitoring positions inside and outside the tunnel based on the rock formation characteristics, and then performs advance support through a combination of a small lead pipe and small lead grouting, thereby improving the safety of construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 A flowchart of a method for tunneling through a building based on the drill-and-blast method provided in one embodiment of the present application;

[0020] Figure 2 A layout diagram of the vault subsidence measurement points proposed in this application;

[0021] Figure 3 A layout of the land subsidence monitoring points proposed for this application;

[0022] Figure 4 This is a schematic diagram of the buried piezometer proposed in this application;

[0023] Figure 5 Cross-sectional view of the advanced support pipe shed proposed for this application;

[0024] Figure 6 A schematic diagram of an excavation method provided in an embodiment of the present application;

[0025] Figure 7 Schematic diagram of radial grouting construction proposed for this application;

[0026] Figure 8Schematic diagram of the long anchor rod joint anchor reinforcement proposed in this application. DETAILED DESCRIPTION

[0027] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0028] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0029] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0030] As used in this specification and the appended claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0031] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0032] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0033] Figure 1 A flowchart of a method for tunneling through a building based on the drill and blast method is provided in accordance with an embodiment of the present application.

[0034] S110, predicting rock formation characteristics within a preset range in front of the tunnel.

[0035] In one possible implementation, the method for predicting the rock formation characteristics within a preset range in front of the tunnel includes a seismic wave method and an advance horizontal drilling method; the seismic wave method predicts the rock formation characteristics within a preset range in front of the tunnel by determining the position of the impact point and the sensor of the position of the impact point; the advance horizontal drilling method obtains the front rock core through drilling; and determines the rock formation characteristics within the preset range in front based on the front rock core.

[0036] The True Reflection Tomography (TRT) geological advance prediction system is capable of providing medium- and long-term forecasts for tunnel construction. Based on the reception and processing of reflected seismic wave signals, the system can accurately predict changes in geological conditions and rock properties within a certain range ahead of tunnel construction, providing direct guidance for ensuring the smooth progress of tunnel construction.

[0037] The basic principle of TRT technology is that when seismic waves encounter an interface with a difference in acoustic impedance (the product of density and wave velocity), a portion of the signal is reflected back, while a portion is transmitted into the medium ahead. This change in acoustic impedance typically occurs at the interface of geological rock layers or discontinuities within the rock mass. The reflected seismic signal is received by highly sensitive seismic sensors and analyzed to determine the nature (weak zones, fractured zones, faults, water content, etc.), location, and size of the geological body ahead of the tunnel working face.

[0038] In the seismic wave method, the vibration points should be selected on the primary support behind the tunnel face, where the shotcrete strength has reached at least 100%, avoiding the arch. Twelve vibration points are arranged on each side wall, two rows of three points each. The first row begins 1 meter from the tunnel face and consists of 2 x 3 points spaced 0.5 meters apart. The second row, 2 meters from the first row, also consists of 2 x 3 points spaced 0.5 meters apart.

[0039] Begin installing sensors 10 to 20 meters back from the last impact point. Ten sensors should be arranged in four rows, spaced 5 meters apart. Rows 1, 2, 3, 2, and 3 sensors should be installed, respectively. The two sensors in the first and third rows should be symmetrically mounted on the left and right side walls, 1.5 meters above the tunnel floor. In the second and fourth rows, one of the three sensors should be mounted on the centerline of the arch, and the other two should be symmetrically mounted on the left and right side walls, 0.5 meters above the tunnel floor. The sensors should be installed on primary support with 100% shotcrete strength, avoiding the arch support. During installation, first chisel the primary support surface flat, drill a 60mm-deep hole with an 8mm drill bit, and attach mounting blocks to the arch or side walls with quick-drying expansive cement. The sensors should be mounted on the mounting blocks, ensuring close coupling between the sensors and the rock mass. When installing the sensor, its wiring should be left on the opposite side of the tunnel's forward direction. Data collection can only be carried out after the quick-drying cement used to stick the sensor fixing block has completely solidified.

[0040] Check whether the displays of the 11 sensors in the receiving software are all green (the extra sensor is the receiving base station), and ensure that all sensors and the triggers on the hammer head are working properly. Use an 8-pound hammer (the hammer handle is 1.0m long, and an ordinary strong laborer can use the hammer to hit) to hit the vibration points, and hammer each vibration point 3 times. The requirements for the hammer frequency and the vibration amplitude generated by the hammer are based on the quality of the received waveform, whether there is obvious distortion of the first wave, or the strength of the signal to judge the vibration effect. The frequency is 3 hits per vibration point. After each vibration, wait until the instrument has finished receiving the signal before the next hit. Hit each of the 12 vibration points 3 times, and collect a total of 36 signals → data acquisition → record the signal number.

[0041] The collected data is processed using O-RV3D software. The TRT data processing process consists of the following eight steps:

[0042] 1. Download seismic wave data and the coordinates of the source and sensor locations;

[0043] 2. Set the size of the formation imaging area and the optimal accuracy (number of nodes);

[0044] 3. Set the filter, select the direct wave of each record, and calculate the average velocity of the seismic wave;

[0045] 4. Construct a seismic wave velocity model for the selected block;

[0046] 5. Set filtering parameters for data processing;

[0047] 6. Repeat steps 1, 4, and 5 to process the data until the processing results reach equilibrium and the noise interference is attenuated to a sufficiently small level;

[0048] 7. Set the background (scale, color code) to display the results;

[0049] 8. Review and analyze plan (two-dimensional) and stereo (three-dimensional) plots of anomalies detected in rock formations.

[0050] Advanced horizontal core drilling can be considered a miniature pilot pit in a tunnel, allowing for the exploration of surrounding rock geology within tens or even hundreds of meters ahead of the tunnel excavation face. During drilling, drill bit deviation, which can lead to errors in the detection results, should be minimized. The drill speed and drilling pressure should be adjusted according to the rock hardness. For hard rock, a lower speed and higher drilling pressure are used; for softer rock, a higher speed and lower drilling pressure are used. Alternatively, drilling blastholes, deepwater boreholes, or sonic boreholes in the excavation face can be used to explore surrounding rock geology.

[0051] The advance drilling distance is generally 30 meters, with a 10-meter overlap to ensure sufficient safety rock pillars. Down-the-hole drills or geological drills are used. Advance drilling is conducted in sections with geophysical anomalies, sections with unfavorable geological bodies in the design, sections with complex geology requiring further exploration, and other sections with the risk of water and mud inrush. In general tunnel sections, a 30-meter exploration hole is drilled in the middle of the tunnel face, perpendicular to the tunnel face. In key tunnel sections, 3-5 30-meter exploration holes are drilled, perpendicular to or outwardly to the tunnel face.

[0052] By analyzing the intuitive records of water return and weak layers during the drilling process, the following information can be obtained:

[0053] 1. The integrity of the rock mass and the development of fractures in front of the tunnel face;

[0054] 2. The surrounding rock grade, lithologic changes, and lithologic interfaces in front of the tunnel face;

[0055] 3. The specific location of the dissolution cavity in front of the face and the filling condition of the dissolution cavity;

[0056] 4. Rock mechanical parameters of key tunnel sections;

[0057] 5. Water content and water inflow in front of the face;

[0058] 6. Determine the danger of sudden water and mud in the tunnel.

[0059] By comparing the drilling results with the geophysical conclusions and the geological conditions revealed during the construction excavation process, we can further analyze the geological factors that affect construction safety, such as the softness, hardness, integrity, and stability of the stratum, and continuously correct the preliminary drilling conclusions and adjust construction measures.

[0060] According to the seismic wave method and advanced horizontal core drilling, the surrounding rock can be divided into Class III surrounding rock, general Class IV to V surrounding rock and Class V surrounding rock fault fracture zone.

[0061] S120, set up monitoring positions in the tunnel and monitor the vault subsidence data inside and outside the tunnel using convergence meters, total stations and levels.

[0062] In one possible implementation, monitoring positions are set in the tunnel, and the vault subsidence data inside and outside the tunnel are monitored using a convergence meter, a total station, and a level, including: the spacing between the monitoring positions is determined based on the rock formation characteristics, the tunnel burial depth, and the excavation method; the spacing between the monitoring positions and the tunnel face meets a preset distance; and the vault subsidence data reading is completed within 3 to 6 hours when the data occurs.

[0063] The spacing between measurement sections and the measuring points, types, locations, and numbers on each section should be determined based on the tunnel depth, surrounding rock grade, tunnel section size, excavation method, support type, etc. The number of measuring points for surface subsidence measurement should be appropriately larger, and the complete longitudinal and transverse settlement curves should be measured to analyze the longitudinal and transverse impact range and degree of tunnel construction. Items such as clearance changes, vault subsidence, and surface subsidence (underpassing road tunnel sections) should be set on the same section. When there are buildings on the surface, additional surface subsidence observation points should be set around the buildings. The spacing between measurement sections should be determined according to Table 1 based on the surrounding rock grade, tunnel depth, and excavation method. Figure 2 This is a layout diagram of the arch subsidence measurement points proposed in this application. 2, 3, or 5 monitoring points can be arranged as shown. Each measurement point is buried close to the working face (tunnel face), generally 1.0m away from the tunnel face. Initial readings are completed before the next excavation cycle, and initial deformation value readings are completed within 24 hours:

[0064] Table 1: Measurement section spacing and number of measurement points per section

[0065]

[0066] Surface subsidence (shallow buried tunnel sections, tunnel sections under highways) observation points should be arranged along the center line of the line, with a spacing of 5 to 30 m. If necessary, 1 to 2 cross sections should be set up, with 7 to 11 points in each section. The monitoring range should be within the influence range of tunnel excavation.

[0067] The measuring points should be buried as soon as possible within 1m of the excavation surface. The burial form of the measuring points should be determined in combination with the specific measurement method. If a total station is used to observe the clearance changes, a reflector should be fixed on the anchor rod driven into the surrounding rock as an observation point. If a convergence meter and level instrument observation method is used to observe the clearance changes, a steel hook should be fixed on the anchor rod driven into the surrounding rock as an observation point.

[0068] Observation of measurement items:

[0069] 1. Observation inside and outside the cave

[0070] In-tunnel observation can be divided into two parts: observation of the excavation face and observation of the constructed section. Observation of the excavation face should be conducted after each excavation. If deterioration of the surrounding rock conditions is observed during observation, appropriate measures should be taken immediately. Following the observation, a geological sketch of the excavation face should be drawn, and a geological status record sheet and construction phase surrounding rock grade determination card should be completed. Observation of the constructed section should be conducted at least once a day, primarily to monitor the working conditions of shotcrete, anchor bolts, steel frames, and secondary lining.

[0071] The focus of observation outside the tunnel should be on the tunnel entrance and the area where the tunnel body is buried at a shallow depth. The observation content should include surface cracks, surface subsidence, stability of the slopes and back slopes, surface water infiltration, etc.

[0072] 2. Initial readings of vault settlement and convergence measurements should be completed within 3 to 6 hours. Other measurements should be taken within 12 hours of each excavation, and no later than 24 hours after each excavation. These readings must be completed before the next excavation cycle. Initial readings are crucial for monitoring and measuring data analysis, and initial observations must be made at the observation points within the specified timeframe. Vault settlement can be observed using a level and a suspended steel ruler, or using a non-contact target total station for alignment measurement. Convergence can be observed using a convergence meter or a non-contact target total station for alignment measurement.

[0073] 3. The measurement base points of arch subsidence and ground subsidence should be linked to the leveling base points inside and outside the tunnel.

[0074] 4. Collect measurement data in a timely manner according to the observation frequency of each measurement item.

[0075] Furthermore, in order to ensure that the tunnel passes safely through buildings, it is necessary to set up settlement points on the ground to observe ground settlement.

[0076] Specifically, 5 monitoring sections are set up in each underpass section, with a section spacing of 5m. Three settlement monitoring points are set up in each section. At the same time, a settlement monitoring point is set up every 10m along the line direction on the center line of the tunnel.

[0077] At least three ground base points should be buried in a relatively stable location that is not affected by tunnel construction. Figure 3 This is the layout of the ground settlement monitoring points proposed for this application. The base points are deep-buried reinforced pile leveling points, buried at a depth of at least 1 meter, using coarse rebar and poured with concrete. The monitoring points are constructed by digging 20-30 cm deep pits on the ground surface and pouring concrete. Specialized stainless steel settlement probes are inserted into the concrete. The probes are hemispherical and protrude approximately 2-3 cm above the concrete.

[0078] S130, using an osmometer, determining the seepage amount according to the passing flow rate and a preset method.

[0079] Tunnels near or crossing reservoirs experience significant water seepage. This not only impacts tunnel construction but also the surrounding groundwater environment. Therefore, groundwater seepage in tunnels is monitored. This primarily involves monitoring external water seepage and external water pressure, using piezometers. Figure 4 This is a schematic diagram of the buried piezometer proposed in this application, as shown in Figure 4 As shown in the figure, the piezometer is buried in the borehole, surrounded by sandbags and medium-coarse sand. The arrangement of the piezometer is mainly determined by the hydrological and engineering geological conditions. It is usually arranged at the top, waist and bottom of the tunnel surrounding rock close to the concrete lining.

[0080] Tunnel seepage monitoring begins when the tunnel section nears or crosses a reservoir and continues until water begins to flow through the tunnel. After a single seepage point is discovered, observations are generally conducted daily. After the leakage has stabilized, observations are conducted every 3-7 days. After the seepage point has been grouting, observations are generally conducted daily. After the leakage has stabilized, observations are conducted every 3-7 days. If abnormal seepage occurs, observations are increased.

[0081] Specifically, the osmometer can be a steel string osmometer or a differential resistance osmometer.

[0082] Calculation formula for water pressure P of steel string piezometer:

[0083] Pt=K×(R0-Rt)+C×(Tt-T0)

[0084] Where: P - seepage pressure measured at time t (MPa); K - instrument coefficient (MPa / digitl); Rt - instrument reading at time t (digitl); R0 - initial instrument reading (digitl); C - temperature coefficient (MPa / ℃); Tt - temperature reading at time t (℃); T0 - initial temperature reading (℃);

[0085] Calculation formula of water pressure P of differential resistance piezometer:

[0086] P=fΔZ-bΔt

[0087] In the formula: P is the permeate pressure (MPa), which is negative when under pressure; f is the minimum reading of the piezometer (10-6 / 0.01%); b is the temperature correction coefficient of the piezometer (MPa / ℃); ΔZ is the change in resistance ratio relative to the reference value. When the instrument pressure increases, ΔZ is negative; Δt is the change in temperature relative to the reference value. It is positive when the temperature increases and negative when the temperature decreases. The unit is ℃.

[0088] In one possible implementation, the preset methods include the volumetric method, the weir method and the flow rate method. An osmometer is used to determine the seepage rate based on the flow rate and the preset method, including: using the volumetric method when the flow rate is less than 1 L / s; using the weir method when the flow rate is between 1 and 300 L / s; when the flow rate is greater than 300 L / s or the weir cannot be set, the leakage water is introduced into the drainage ditch and the flow rate method is used.

[0089] Specifically, the volumetric method: When observing flow, the seepage water needs to be introduced into a container (such as a graduated cylinder, etc.), and the seepage water volume and water filling time (generally 1 minute, and not less than 10 seconds) are measured to obtain the seepage flow. The commonly used weir method is triangular weir, trapezoidal weir and rectangular weir, with triangular weir being the most commonly used. The weir plates of various water measuring weirs are generally made of stainless steel plates. The velocity method: The velocity measuring trench for observing seepage flow should be a straight segment of not less than 15 meters in length, with a consistent cross-section, maintaining a certain longitudinal slope, and not being disturbed by other water.

[0090] The method used in this application is the water-measuring weir method, which first needs to be installed and buried. The specific method is as follows: (1) The water-measuring weir is generally set on the straight section of the drainage ditch, the weir body adopts a rectangular cross-section, and the weir plate should be made of stainless steel; (2) The size of the weir trough section and its relative relationship with the weir plate should meet the following requirements: the total length of the weir trough section should be greater than 7 times the weir head, but not less than 2m, of which the upstream of the weir plate should be greater than 5 times the weir head, but not less than 1.5m, and the weir trough width should be no less than 3 times the maximum width of the weir. times; (3) The weir plate should be flat, and the local unevenness should not exceed ±3mm, and the local unevenness of the weir mouth should not exceed ±1mm; (4) The top of the weir plate should be horizontal, and the height difference on both sides should not exceed 1 / 500 of the weir width. The right angle error of the right-angle triangular weir should not exceed 30; (5) The weir plate and the side wall should be vertical, and the error should not exceed 30; (6) The two side walls should be parallel, and the local spacing error should not exceed 10mm; (7) The water gauge or water level meter should be installed 3 to 5 times the water head of the weir mouth upstream of the weir plate.

[0091] The calculation method of the water measuring weir method is as follows:

[0092] 1. Right triangle water measuring weir

[0093] Q=1.4H 5 / 2

[0094] Where: H - water head above weir (m)

[0095] 2. Trapezoidal water measuring weir

[0096] The weir should be kept strictly horizontal. The flow rate Q of the 1:0.25 trapezoidal weir is calculated as follows:

[0097] Q=1.86bH 3 / 2

[0098] 3. Rectangular water measuring weir

[0099] The calculation of rectangular water-measuring weir is relatively complicated. The calculation formula of flow Q of rectangular water-measuring weir without lateral contraction is:

[0100]

[0101] Where: m = (0.402 + 0.054H / P).

[0102] S140, support the outside of the cave by grouting and anchor rods.

[0103] In one possible implementation, the supporting outside the cave by grouting and anchor rods includes: drilling holes in the rock surface using an anchor drill or a handheld pneumatic rock drill, with the hole positions being perpendicular to the rock surface; supporting the outside of the cave based on the hole positions and a preset support sequence, and the support sequence includes grouting first and then inserting anchor rods, and inserting rods first and then grouting.

[0104] Anchor bolts are prefabricated outside the tunnel and must be clean of oil, rust, and other impurities. During construction, the anchor holes must be precisely drilled and deep. Anchor holes are drilled and installed using an anchor drill rig or a YT-28 pneumatic rock drill. Different construction techniques are used depending on the relative position of the mortar anchor bolts to the tunnel rock face: Sidewall system anchor bolts and locking foot anchor bolts face upward, using grouting first and then bolt insertion. Arch system anchor bolts face downward, using bolt insertion first and then grouting. After the anchor bolts are formed, the anchor bolt heads are securely welded to the steel arch frame.

[0105] Use an anchor drill or handheld pneumatic rock drill to drill holes. Maintain the anchor hole perpendicular to the rock surface, with a depth tolerance of no more than 5 cm and a diameter of φ50 mm. After drilling to the designed depth, use high-pressure air to blow away any debris, level the rock at the hole opening, and align the rock surface perpendicular to the drilling direction. Use M30 cement mortar with a water-cement ratio of 0.4-0.45 and a cement-sand ratio of 0.5-1.

[0106] Grouting and anchor rods are used to support the outside of the cave, which includes two forms: grouting first and then inserting anchor rods, and inserting rods first and then grouting.

[0107] Grouting first and then anchor rod insertion

[0108] First, inject water into the grouting pump and add a small amount of mortar. Initially pressurize the pipe with water and mortar to wet the pipe. Then, pour the prepared mortar into the pump. Insert the grouting pipe into the anchor eye and tighten the pump cover to seal it. Once everything is ready, slowly open the valve and begin grouting. Driven by air pressure, the mortar is continuously pressed into the eye. The grouting pipe then slowly withdraws from the eye. Always keep the grouting pipe mouth buried in the mortar to prevent cavities in the mortar. If the hole overflows, completely withdraw the grouting pipe.

[0109] After grouting is complete, quickly insert the anchor rod into the hole manually or with a pneumatic rock drill. Gently hammer the rod into the hole until it penetrates deeply. Then, plug the hole with a wooden wedge to prevent mortar loss. The length of the anchor rod inserted into the hole must not be less than 95% of the designed length. If no mortar overflows from the hole during insertion, remove the rod and re-grout.

[0110] Insert rod first and then grout

[0111] Before installing the anchor rod, mark the rod body with paint according to the designed exposed length, and weld the positioning steel bars at the same time. The positioning steel bars are made of φ8 smooth round steel bars into Ω shape, and are evenly spot welded on the rod body in groups of 3, with a spacing of 2m between each group.

[0112] After the anchor is positioned, the hole is sealed with quick-hardening cement mortar. The grouting pipe and exhaust pipe are installed simultaneously. The grouting pipe uses a φ20mm hard PVC pipe, with the tail extending 10-20cm into the anchor hole. A DN25 gate valve is installed at the head of the grouting pipe. The gate valve's steel pipe is connected to the PVC pipe with a threaded connection. The exhaust pipe uses a φ15mm plastic hose, which is tied to the rod body with fine wire and inserted into the hole flush with the tail of the anchor, with about 15cm exposed.

[0113] Once the orifice is sealed with cement mortar that meets the requirements, grouting can begin. Grouting should not be performed if the orifice is not tightly sealed. If grouting does not return, remove the rod and rework immediately. Connect the grouting hose provided with the grouting pump to the grouting gate valve, tighten the pump cover to seal it, and when everything is ready, slowly open the valve to begin grouting. Driven by air pressure, continuously press the mortar into the hole. When continuous mortar flows out of the vent hole, stop grouting immediately, close the grouting gate valve, and fold and tie the vent hose to prevent leakage.

[0114] The grouting pressure is controlled at 0.2MPa. The pressure can be increased appropriately to ensure that the slurry can flow into the hole evenly and slowly, but it should not be too high.

[0115] After the grouting is completed, remove the grouting valve and exhaust pipe in time, and seal the grouting port and exhaust port with fast-hardening cement mortar.

[0116] After mortar anchor grouting, the anchor pull-out force test is carried out when the mortar strength reaches 20MPa or 75% of the design strength.

[0117] In order to further enhance the strength, it is necessary to add steel mesh and steel arch frame, and then spray concrete.

[0118] The steel mesh uses φ8 round steel bars with a mesh size of 150mm x 150mm. The mesh is processed in 1.2m x 1.5m blocks at a rebar processing plant outside the tunnel. The blocks are then transported to the tunnel and manually laid, following the undulations of the spraying surface. They are securely connected to the mortar anchor heads. The overlap between adjacent meshes must be no less than one mesh length, and can be tied or welded. The gap between the mesh and the sprayed surface is approximately 5cm.

[0119] The steel arch frame is made of I18 I-steel, which is centrally processed by a steel cold bending machine in the processing plant, and manually installed and formed on site with mechanical coordination.

[0120] Steel arch processing: The steel arch is pre-fabricated in a processing room outside the tunnel according to design requirements. The processing site is first hardened with concrete, and the processing template is laid out according to the design. During layout, welding shrinkage allowance and cutting are reserved according to process requirements. The steel sections are cold-bent to form, requiring accurate dimensions and smooth arcs. After processing, the steel arch is trial-assembled. The allowable error along the tunnel perimeter is no more than 3cm. The steel arch is assembled from the arch and side wall steel units. The units are connected with bolts. The error between the bolt hole centers does not exceed ±0.5cm. When the steel arch is laid flat, the plane warping should be less than ±2cm.

[0121] Steel arch erection: The steel arch should be placed on a stable foundation. During the erection of the steel arch, a groove should be dug into place, and channel steel should be installed at the arch footing to increase the bearing capacity of the base. The plane of the steel arch should be perpendicular to the tunnel centerline, with an allowable vertical deviation of ±2°. The longitudinal spacing of the steel arches should not exceed ±10cm. The lateral deviation should not exceed ±5cm. The elevation deviation should not exceed ±5cm. To ensure the accurate placement of the steel arch, grooves for the steel arch connecting plates should be reserved at each of the steel arch connecting plates during tunnel excavation. Grooves for the steel arch channel steel should also be reserved at both arch feet and at the base of the two side walls. Wooden wedges should be driven into these grooves during the initial spraying of concrete. To enhance the overall stability of the steel arch, the steel arch should be welded to anchor rods, and longitudinal connecting steel bars should be installed along the length of the steel arch. Where anchor rods are available at the steel arch erection site, they should be used for positioning. The ends of the anchor rods should be bent 90° at a distance of 10-15cm in the locking mortar and welded to the steel arch. After the steel arch frame is erected, spray concrete as soon as possible and cover the entire steel arch frame so that the steel arch frame and the sprayed concrete bear the force together.

[0122] Before spraying concrete, the excavation section must be inspected. C25 shotcrete is mixed centrally at the concrete mixing station. The wet spraying process is as follows:

[0123] 1. Shotcrete shall be mixed strictly according to the designed mix ratio, and the mix ratio and mixing uniformity shall be checked at least twice per shift.

[0124] 2. Carefully check the tunnel section before spraying, clean and treat the under-excavated part and all cracked, broken, water-outlet, and collapsed loose rocks, remove pumice and corner debris, and flush the rock surface with high-pressure water or wind.

[0125] 3. Before spraying concrete, steel anchors should be driven into the sprayed surface at intervals of 0.5m to 1.0m to control the thickness of the sprayed concrete accordingly.

[0126] 4. The distance between the nozzle and the rock surface should be 0.6m to 1.0m. The nozzle should be perpendicular to the sprayed surface. When spraying the arch frame and steel mesh in the early stage, the nozzle can be slightly tilted to an angle greater than 70°. The spraying route should first hit the side wall and then the arch, and move in an "S" shape in sections and segments. The nozzle should make continuous circular motion, with the last circle pressing 1 / 3 of the previous circle, and spraying in a spiral shape.

[0127] 5. Shotcrete operations should be carried out in sections and blocks, starting with the wall and then the arch, and proceeding from bottom to top. The nozzle should make repeated, slow spiral movements with a spiral diameter of approximately 20 to 30 cm to ensure dense spraying of the concrete. At the same time, the wind pressure and spraying distance should be controlled to reduce rebound. After the shotcrete has finally set for 2 hours, it should be sprayed and cured for at least 7 days. When spraying concrete, the interval between the completion of the shotcrete spraying and the next blasting time must not be less than 4 hours. If the shotcrete is locally uneven and the flatness is greater than 10 cm, additional spraying should be performed.

[0128] 6. Take the following measures for shotcrete spraying in water tunnel sections:

[0129] When there are not many water gushing points, a conduit can be installed to drain the water before spraying concrete; when the water gushing range is large, a tree-like drainage conduit can be installed before spraying concrete; when the water gushing is serious, a drainage hole can be set to drain the water while spraying concrete.

[0130] Increase the amount of cement, change the mix ratio, spray concrete from far to near gradually approaching the water gushing point, install a conduit at the water gushing point, lead the water out, and then spray concrete near the conduit.

[0131] When the rock surface is generally seeping, mortar can be sprayed first, and the amount of accelerator can be increased. After the initial spraying, construction can be carried out according to the original mix ratio. When the local water outflow is large, measures such as buried pipes, grooves, and dendritic drainage ditches can be used to guide the water out before spraying concrete.

[0132] S150, before excavation, advance support is carried out through advance small pipes combined with small pipe grouting.

[0133] In one possible implementation, before excavation, advance support is carried out by using advance small pipes combined with small pipe grouting, including: the advance small pipes are evenly arranged along the excavation line of the tunnel arch, with a spacing of 30-50 cm; the grouting sequence is from bottom to top, and when string holes occur, a grouting device is used for multi-hole grouting or the string holes are blocked for grouting; when the pressure reaches the preset grouting final pressure and stabilizes for 10-15 minutes, and the grouting volume reaches more than 80% of the preset grouting volume, the grouting is terminated; when the grouting pressure fails to reach the preset final pressure, but the grouting volume has reached the preset grouting volume and there is no leakage, the grouting is terminated.

[0134] The drill-and-blast tunnel in this application adopts advanced small guide tubes as an advance support method for Class V surrounding rock. The small guide tubes are made of φ50mm steel pipes, with a single length of 4.5m, two adjacent rows overlapped by 1.5m, the circumferential spacing is 30cm, and the external insertion angle is 10~15°.

[0135] The advance small guide tubes are evenly arranged along the tunnel arch excavation line with a design spacing of 30 cm. The specific spacing can be adjusted appropriately according to the geological conditions and self-stabilization capacity in front of the excavation working face, but the maximum spacing should not exceed 50 cm.

[0136] After the hole is drilled, a small conduit is driven directly into the middle of the steel frame using a rock drill or manually, with 20 cm of the small conduit exposed. After the grouting is completed, it is welded to the steel frame and supported on the steel frame behind the excavation surface or forms a pre-support system together with the steel frame.

[0137] Use cement water glass mortar or fast-hardening cement mortar to seal the gap between the small tube and the rock hole.

[0138] Install grouting valves and pipelines, and connect the grouting pipe and the small guide tube steel pipe with a flexible joint to ensure quick assembly and disassembly.

[0139] When the tunnel surrounding rock is relatively broken, in order to effectively advance reinforce the surrounding rock in front, it is necessary to adopt a double-layer advance small conduit reinforcement method. The inner small conduit is arranged according to the general small conduit parameters, and the outer small conduit and the inner small conduit are alternately arranged. Generally, the external insertion angle should be greater than the external insertion angle of the inner small conduit, which can increase the range of the surrounding rock reinforcement circle and ensure the stability of the surrounding rock.

[0140] After the ultra-small conduit is installed, grouting is required. The grouting process is as follows:

[0141] 1. Grouting is done by injecting cement slurry with a grouting pump. The water-cement ratio of the cement slurry is 1:0.5 to 1:1. If the groundwater in the grouting section is large, 5% water glass can be added to the cement slurry.

[0142] 2. After the small pipe is installed, a water pressure test should be carried out. The pressure is generally not greater than 1.0 MPa. The grouting parameters are determined based on the design and test results. The grouting pressure is generally 0.5-1.0 MPa. The slurry is configured according to the designed ratio and must fill the gaps around the steel pipe and the surrounding area.

[0143] 3. Cement slurry is prepared in a mixing drum. When preparing cement slurry, foreign matter should be prevented from mixing in. The prepared slurry must be filtered before use.

[0144] 4. The prepared slurry should be injected within the specified time and used immediately after preparation.

[0145] 5. The grouting order is from bottom to top, the slurry is thin at first and then thick, the grouting volume is large at first and then small, and the grouting pressure is from small to large.

[0146] 6. When cross-holes occur, use a grout divider to inject multiple holes or plug the cross-holes and inject grout in separate holes. If the grouting pressure suddenly increases, the machine should be stopped to investigate the cause. If the cement slurry inlet pressure is very high and the pressure remains unchanged, the slurry concentration and mix ratio should be adjusted, the gel time should be shortened, and low-flow, low-pressure grouting or intermittent grouting should be used.

[0147] 7. Grouting end standard: During the grouting process, the pressure gradually increases and the grouting flow rate decreases. When the pressure reaches the designed grouting final pressure and stabilizes for 10-15 minutes, and the grouting volume reaches more than 80% of the designed grouting volume, the grouting of the hole can be ended. When the grouting pressure fails to reach the designed final pressure, but the grouting volume has reached the designed grouting volume and there is no leakage, the grouting of the hole can be ended.

[0148] 8. After the single-hole grouting is completed and the flexible joint is removed, a slurry stopper is used to quickly seal the steel pipe opening to prevent the unsolidified slurry from flowing out.

[0149] 9. Grouting records should be filled in during the grouting process, and the grouting effect should be inspected after completion. If it is unqualified, additional grouting should be carried out.

[0150] 10. When single-liquid cement slurry is used for grouting, the excavation time is 8 hours after grouting, and when cement-water glass double-liquid slurry is used, it is 4 hours.

[0151] Another possible implementation involves, in addition to the use of advanced small-diameter pipes combined with small-diameter grouting, advanced anchor bolting. Specifically, for Class IV surrounding rock, advanced anchor bolts are used as an advanced support method. The holes of the advanced anchor bolts face downward, and the process of inserting the bolts first and then grouting is used. The advanced anchor bolts are used in conjunction with steel arch frames.

[0152] The anchor rods are made of φ22 threaded steel bars and are 4.5m long. The anchor rods are arranged at a spacing of 30cm along the arch ring, with an external insertion angle of 10-15°, which can be adjusted according to actual conditions. The longitudinal spacing is 3.0m per ring, and the overlap length is not less than 1.5m. The process flow of advanced anchor support is as follows:

[0153] 1. After the anchor is positioned, seal the hole with quick-hardening cement mortar. Simultaneously, install the grouting pipe and exhaust pipe. Use a φ20mm hard PVC pipe for the grouting pipe, with the tail extending 10-20cm into the anchor hole. Install a DN25 gate valve at the head of the grouting pipe. The gate valve's steel pipe is threadedly connected to the PVC pipe. Use a φ15mm plastic hose for the exhaust pipe, tied to the rod with fine wire, extending into the hole flush with the tail of the anchor, with approximately 15cm exposed.

[0154] 2. Grouting can begin once the orifice is sealed with cement mortar that meets the requirements. Grouting should not be performed if the orifice is not tightly sealed. If grouting does not return, remove the rod and rework immediately. Connect the grouting pipe provided with the grouting pump to the grouting gate valve, tighten the pump cover to seal it, and when everything is ready, slowly open the valve to begin grouting. Driven by air pressure, continuously press the mortar into the hole. When continuous mortar flows out of the vent hole, stop grouting immediately, close the grouting gate valve, and fold and tie the vent hose to prevent leakage.

[0155] 3. The grouting pressure is controlled at 0.2MPa. The pressure can be increased appropriately to ensure that the slurry can flow into the hole evenly and slowly, but it should not be too high.

[0156] 4. After grouting is completed, remove the grouting gate valve and exhaust pipe in time, and seal the grouting port and exhaust port with fast-hardening cement mortar.

[0157] In order to further improve the safety performance, pipe shed support can be further adopted. Figure 5 Cross-sectional view of the advanced support pipe shed proposed for this application.

[0158] The pipe-roof support structure consists of four I18 I-beam arches, spaced 500mm apart. Adjacent arches are connected with Φ22 ribbed steel bars, with circumferential spacing of 1.0m. The pipe-roof casings consist of 44 Φ146×7.5mm steel pipes, each 2.0m long. These are arranged in an arc within an 180° arc, with 300mm spacing and an external insertion angle of 1-3°. The casings are welded to the steel arches using Φ16Ω ribbed steel bars. The distance from the center of the inner end of the casing to the tunnel excavation outline is controlled to be 20cm.

[0159] The pipe roof steel pipes are φ108×10mm hot-rolled seamless steel pipes, each 35m long (with segments 4-6m long) and 300mm spacing. Adjacent segments of a single pipe are connected with 300mm threaded connections. A reinforced cage is built into the pipe roof to enhance its bending resistance. The cage uses five φ16 ribbed steel bars as longitudinal main reinforcement. φ30×3mm steel pipes serve as longitudinal reinforcement retaining rings, each 50mm long and 1500mm apart. The retaining rings are spot welded to the longitudinal reinforcement. Adjacent cage segments are connected using double-sided lap welds with an 80mm overlap. The grouting slurry is a cement slurry with a water-cement ratio of 1:0.5 to 1:1. If the groundwater volume in the pipe roof construction section is high, 5% water glass may be added to the slurry. The pipe roof grouting is performed using a skip-hole grouting method, with an initial grouting pressure of 0.5-1.0MPa and a final pressure of 2.0MPa.

[0160] During the installation of the arch steel frame, a total station was used to mark out the arch foot positions of the pipe-roof guide frame I-beam arch frames. The steel frames were then installed according to the marked positions. Each steel frame consists of three arc-shaped sections and is installed in two stages. The first and fourth steel frames were installed first, followed by the two intermediate steel frames. The steel frames were longitudinally connected with Φ22 ribbed steel bars, with a circumferential spacing of 1.0m. The steel arches were welded to the connecting steel plates, and the connecting steel plates were bolted together. The steel frames were perpendicular to the tunnel centerline, with each steel frame spaced 0.5m apart longitudinally.

[0161] After the guide frame steel arch is installed, the casing is precisely positioned at the outer edge of the steel arch using a total station. The position of the φ146×7.5mm casing is marked on the wall of the 118 I-beams at a designed 30cm circumferential spacing from the center of the arch. When installing the casing, an external insertion angle of 1 to 3° (excluding the longitudinal slope of the line) must be set. The specific method is as follows: the spacing from the innermost to the outermost steel arch within the arch is designed to be 1.5m. Based on the angle, the height to which the three inner arches must be raised (the heights from the outside to the inside are 19mm, 36mm, and 54mm, respectively) are calculated. When installing the casing, a steel plate is placed at each marked point on the three inner arches (i.e., between the casing and the arch). The casing is then fixed outside the steel plate to form the required external insertion angle. The upper end is fixed with Φ16 ribbed steel bars welded to the I-beam.

[0162] Pipe roof installation precautions:

[0163] 1. The diameter of the long pipe roof is φ108×10mm seamless steel pipe. φ15mm overflow holes are drilled on the pipe wall of the pipe roof and arranged in a plum blossom shape with a longitudinal and transverse spacing of 15 to 20 cm. The tail is a grouting stop section without drilling holes that is not less than 300 cm.

[0164] 2. Steel pipe joints utilize threaded connections with a thread length of 30 cm. To prevent staggered pipe connections, the first section of each hole uses 4m and 6m steel pipes for odd and even holes, respectively. Each subsequent section uses 6m long steel pipes. The top of the steel pipe must penetrate at least 2m into the well-drilled surrounding rock. The pipe shed is 22m long, so extensions are necessary. To extend the shed pipe, first push the preceding steel pipe into the drilled hole and connect it with an inner casing. The front end of the first steel pipe is sealed and pointed to prevent bending or splitting. A φ10 stiffening hoop is welded to the rear end, and two rows of 10mm grouting holes are drilled into the pipe wall. Steel pipe joints are staggered in odd and even numbers, with the number of joints within the same longitudinal section not exceeding 50%. Joints between adjacent steel pipes must be staggered by at least 1m.

[0165] 3. The pipe rack is installed using a down-the-hole drill rig in conjunction with manual installation. After placing the steel pipe on the drill boom, the drill rig is aligned with the casing. Using the drill's impact and thrust (the drill does not use rotary pressure or generate torque during pipe jacking), the steel pipe, equipped with the working pipe head, is advanced along the casing at a low speed. When the first steel pipe is pushed into the hole, with 30-40 cm remaining outside, the rock drill is reversed to disengage the jacking sleeve from the steel pipe. The drill rig returns to its original position, the boom is lowered, and the second section of steel pipe is manually installed. The boom is realigned, and the drill rig is slowly advanced at a low speed to align with the end of the first section (strictly controlling the angle). A chain clamp is used to manually connect the steel pipes, connecting the two sections at the sleeve. The drill rig then continues to jack the steel pipe at a low speed using impact and thrust pressure. Depending on the designed length of the pipe rack, the steel pipe is extended section by section using the same method until the bottom of the hole is reached. The impact pressure during pipe jacking should be controlled between 1.8 and 2.0 MPa, and the thrust pressure between 4 and 6 MPa.

[0166] 4. In order to improve the bending resistance of the pipe-roof steel pipe, a steel cage is inserted into the steel pipe. The steel cage consists of 5 main bars and a fixed ring. The main bars are Φ16 ribbed steel bars, and the fixed rings are φ30×3 short pipe sections. They are welded to the main bars and set at intervals of 1.5m. The installation method of the steel cage is similar to that of the pipe-roof steel pipe. It is installed in sections into the steel pipe. The longitudinal steel bars are double-sided lap welded with a welding length of 80mm. The steel bar lap joints and steel pipe joints are staggered by at least 1m.

[0167] After the pipe roof is installed, the orifice needs to be sealed. The specific process is as follows:

[0168] A 1.5mm thick circular steel plate is welded to the rear end of the steel pipe to seal the pipe opening. The contact surface between the edge of the steel plate and the pipe wall at the rear end of the steel pipe is fully sealed and welded to prevent leakage during grouting. At the same time, grouting holes and exhaust holes are reserved on the steel plate. The exhaust hole also serves as a grouting hole. DN25 gate valves are installed on the grouting holes and exhaust holes respectively. The grouting valve is installed in the center of the steel plate. The grouting pipe penetrates at least 20cm into the steel pipe of the pipe shed. The exhaust valve is installed near the top edge of the steel plate. The exhaust pipe is tied to the outside of the pipe shed steel cage with fine wire and fed into the hole together with the steel cage. The exhaust pipe head is 10cm away from the head of the pipe shed steel pipe. After grouting is completed, the steel plate and gate valve are removed, and quick-drying cement mortar is used to seal the steel pipe opening and the gap between the steel pipe opening and the casing.

[0169] Finally, grouting is required. Before grouting, the excavation face should be sealed using sprayed concrete and grouting or other methods to form a grout stop wall to prevent slurry backflow and affect the grouting effect. The principle of pipe-roof grouting is to "first the two sides, then the center," "skip-hole grouting," and "from dilute to concentrated." Grouting begins at the ends of the pipe-roof steel pipes, proceeding in a skip-hole manner toward the tunnel vault steel pipes. The slurry concentration should be low at the beginning and gradually increased to the designed concentration. This method facilitates the diffusion of the grouting slurry toward the vault and promotes slurry density, which is beneficial for anti-seepage requirements. After the pipe-roof with an even number of holes is completed, this section of the pipe-roof is grouted. The pipe-roof grouting is designed to consolidate the soil and rock within a limited area around the pipe-roof. The slurry diffusion radius should be no less than 0.5m, and grouting is performed in sections.

[0170] Grouting end standard

[0171] The termination criteria for single-hole grouting are primarily based on the control of the single-hole grouting volume, supplemented by the control of the grouting pressure. As long as one of the following two conditions is met during the grouting process, the single-hole grouting is considered to have met the design requirements and the grouting construction can be terminated. Single-hole grouting termination criteria: The grouting pressure reaches 1.0 MPa and is maintained for more than 10 minutes, or the grouting volume in the soil layer reaches 120 kg / m3 to 150 kg / m3, and the grouting volume in the rock layer reaches 10 kg / m3.

[0172] S160, based on the rock formation characteristics, determine the excavation method and excavate the tunnel to pass through the building.

[0173] In a possible implementation, the excavation method includes an up-and-down step method and a three-step seven-step method.

[0174] Figure 6 Schematic diagram of the excavation method provided in the embodiment of the present application, Figure 6 (a) Excavation is done using the up-and-down step method. Figure 6 (b) Excavation is done using the three-step seven-step method. Figure 6 As shown in Figure (a), the specific steps of the upper and lower steps method are as follows: 1. Excavation of the upper step (①): After the arch advance support is constructed, the upper step is excavated in a circular manner along the tunnel excavation contour. Immediately after excavation, an initial 3-5 cm concrete seal is sprayed, and a steel arch frame is installed. The step length should not exceed 1.5 times the tunnel width. 2. Excavation of the lower step (②): After the upper step (①) is constructed to the appropriate distance and support is completed, and the shotcrete strength reaches 70% of the design strength, the lower step (②) is excavated. The excavation advance is controlled to a spacing of two arch frames per cycle. Immediately after excavation, a 3-5 cm concrete seal is sprayed, and a steel arch frame is installed.

[0175] The specific method of the three-step seven-step method is as follows: Figure 6 (b) shows:

[0176] 1. Step 1: Excavation of the Upper Curved Pilot Tunnel: This is carried out after the arch is advanced supported. The upper curved pilot tunnel is excavated in a circular manner, reserving core soil. The core soil should be 3-5 meters long and 1 / 3-1 / 2 the tunnel excavation width. The excavation cycle advance should be determined based on the initial support steel frame spacing, with a maximum of no more than 15 meters. Immediately after excavation, an initial 3-5 cm of concrete is sprayed. The rise-span ratio of the upper step excavation should be greater than 0.3. After excavation, a spraying, anchoring, and mesh support system should be promptly implemented. The steel frame should be erected. At a height of 30 cm above the steel frame arch foot, lock-foot anchors should be installed close to the steel frame's edges at a 30° inclination angle. The arch foot anchors should be securely welded to the steel frame. Concrete should then be sprayed again to the required thickness.

[0177] 2. Steps ② and ③, excavation of the middle steps on the left and right sides: the excavation advance should be determined according to the initial support steel frame spacing, and the maximum shall not exceed 1.5m. The excavation height is generally 3 to 3.5m, and the left and right steps are staggered by 2 to 3m. Immediately after excavation, spray 3 to 5cm of concrete, and promptly carry out spraying, anchoring, and net system support. Extend the steel frame, and at a height of 30cm above the arch foot of the steel frame, set up locking anchor rods close to the edges of the steel frame on both sides with an inclination angle of 30°. The arch foot anchor rods and the steel frame are firmly welded, and the concrete is sprayed again to the required thickness.

[0178] 3. Steps ④ and ⑤, excavation of the lower steps on the left and right sides: the excavation advance should be determined according to the initial support steel frame spacing, and the maximum shall not exceed 15m. The excavation height is generally 3 to 3.5m, and the left and right steps are staggered by 2 to 3m. Immediately after excavation, spray 3 to 5cm of concrete, and promptly carry out spraying, anchoring, and net system support. Extend the steel frame, and install locking anchor rods at a height of 30cm above the arch foot of the steel frame, close to the edges of both sides of the steel frame and at an inclination angle of 30°. The arch foot anchor rods and the steel frame are firmly welded, and the concrete is sprayed again to the required thickness.

[0179] 4. Step 6: Excavation of reserved core soil for upper, middle and lower steps: After excavation of each step, initial support of the inverted arch is promptly implemented to complete tunnel excavation.

[0180] 5. Step 7, excavation of the tunnel bottom: the excavation advance length of each cycle should be 2 to 3 meters. After excavation, the initial support of the tunnel bottom or pouring of the tunnel bottom concrete should be carried out in time. The segmented length of the tunnel bottom should be 4 to 6 meters.

[0181] In one possible implementation, when a water-rich tunnel section is encountered during tunnel excavation, the method further includes: when the tunnel depth is within 20 m, surface grouting is used; when the tunnel depth is greater than 20 m, curtain grouting and post-excavation radial grouting are used;

[0182] Specifically, curtain grouting involves drilling holes in the water-rich tunnel section and then grouting the holes in a segmented, progressive manner, with each section drilled and grouted. Curtain grouting offers high water-blocking efficiency, long-term durability, and the ability to reinforce the ground, making it an essential method for tunnel construction in water-rich, weak formations.

[0183] Grouting is performed using a staged, progressive grouting method, with drilling followed by grouting, progressing from one section to the desired depth. For difficult-to-drill strata, a pipe tamping hammer should be available. To prevent groundwater from ungrouted sections from surging toward the work surface and preventing grout from escaping during grouting, grouting begins at the tunnel face with a shotcrete stop wall at least 20 cm thick. Each grouting section terminates with a waterstop plate at least 3 m thick. Upon completion of a grouting section and after inspection of the inspection hole, the next grouting section is moved on, and this cycle repeats until all grouting is complete.

[0184] Figure 7 The radial grouting construction diagram proposed for this application, the specific process is as follows:

[0185] 1. Measure the hole layout

[0186] Determine the longitudinal and circumferential spacing. Accurately measure the grouting hole locations along the tunnel perimeter and mark them with paint. Arrange the grouting holes in a plum blossom pattern. The circumferential spacing at the hole openings is 180 cm, the circumferential spacing at the hole bottom is approximately 250 cm, and the longitudinal spacing is approximately 250 cm.

[0187] 2. Drilling

[0188] Use an air gun to drill holes with a diameter of 52mm and a depth of 5m. After drilling to the required depth, remove any stone chips and rock dust from the hole. Check and record the hole spacing, depth, and direction. The allowable deviation for hole spacing is ±5mm, and the allowable deviation for hole depth is within +5mm.

[0189] 3. Install the orifice pipe

[0190] The orifice pipes are hot-rolled seamless steel pipes with a diameter of 50 mm and a wall thickness of 3.5 mm, each 1.0 m long. They are hammered in and must be securely installed. To prevent slurry leakage, the surrounding area is sealed with waterproof mortar, plastic cement, or epoxy resin.

[0191] 4. Connect the grouting pipe

[0192] Connect the grouting pipe and grouting pump as required, and check whether the grouting pump and grouting pipeline are connected correctly and whether the pipeline is unobstructed. After passing the test, prepare for grouting.

[0193] 5. Grouting

[0194] Grouting is performed using a single-liquid cement slurry with a water-cement ratio of 1:0.5 to 1:1 and an accelerator dosage of 5% of the cement dosage. Grouting pressure is 0.5 to 2.0 MPa, and the slurry is expected to spread within a radius of approximately 2 meters. Grouting can be completed in one go throughout the entire hole, or segmented, forward or backward grouting can be employed depending on the degree of fracture development in the rock mass.

[0195] 6. Grouting completion criteria

[0196] The following two methods are usually used as the criteria for the end of grouting: after the grouting pressure continues to rise and reaches the designed final pressure value, grouting can be ended after 2 minutes of continuous grouting; it can be ended when the grouting volume is less than 20L / min.

[0197] During the entire grouting construction process, detailed records should be made of the grouting conditions of each hole. If the grouting effect does not meet the design requirements, additional grouting should be carried out by drilling.

[0198] In one possible implementation, when encountering a broken tunnel section during tunnel excavation, the method further includes: determining an installation position of a grouting steel pipe; performing grouting based on the installation position of the grouting steel pipe, using cement slurry for grouting, in two grouting steps, with an initial grouting pressure of 1 MPa and a final pressure that should be stabilized at 2 MPa.

[0199] The specific construction process is as follows:

[0200] 1. Determination of the scope of reinforcement: Through engineering analogy and the terrain and geological conditions of the tunnel, the scope of surface vertical grouting pre-reinforcement is determined.

[0201] 2. Drilling, surveying, and setting out holes to accurately locate the steel pipe holes and determine the hole depth. The overall drilling process is "from top to bottom, from both ends toward the center." After drilling to the designed elevation, the hole must be flushed with mud before the steel pipe is lowered. Drilling depth control: Outside the tunnel excavation contour, drill to 100 cm below the invert excavation line. The pipe bottom should penetrate 100 cm into the slightly weathered rock stratum, but the maximum depth should not exceed 450 cm below the invert excavation line. Within the tunnel excavation contour, drill to the horizontal line of the tunnel center.

[0202] 3. For grouting steel pipe installation, the diameter is generally 70-120 mm, with a wall thickness of 5 mm. The pipes are arranged in a 150 × 150 cm, quincunx-shaped pattern. C20 concrete grouting plugs measuring 60 × 60 × 30 cm are installed at the pipe ends. The pipe ends are 30 cm above the top of the grouting plugs. No holes are drilled in the pipe within 150 cm below the bottom of the grouting plugs. Holes are drilled in the grouting section, with a 6 mm diameter and a spacing of 30 cm.

[0203] 4. Grouting method and sequence: Cement grouting is used in two injections. The initial grouting pressure is 1MPa, and the final pressure should be stabilized at 2MPa. A water-cement ratio of 0.45 to 1.2 is used. When the steel pipe is inserted into the hole, a PVC hose is extended into the hole bottom along with the steel pipe. Once the steel pipe reaches the bottom of the hole, the first grouting is carried out. Because there is residue and water at the bottom of the hole during drilling, cement slurry is reversely grouted from the bottom of the hole upward to squeeze the residue and water out of the hole, completely filling the space between the steel pipe and the hole wall with clean cement slurry, thereby ensuring a layer of cement slurry protective layer around the steel pipe. After the cement slurry solidifies, a steel pipe cement composite pile group is formed. After the first grouting, a stopper is installed at the pipe opening to prevent slurry from escaping from the pipe opening. Ten to fourteen hours after the first grouting, a second splitting grouting is performed to further expand the volume of the cement slurry around the borehole and fill the shrinkage voids created by the first grouting, further increasing the soil strength. Once the splitting grouting reaches the design pressure, the hole is sealed. Grouting is performed in the order of "peripheral first, then center," and "interval grouting."

[0204] 5. Grouting pressure: The primary grouting is at normal pressure, and the secondary splitting grouting pressure is approximately 1 MPa. Grouting pressure and grouting volume usually change inversely. That is, when the grouting pressure is high, it indicates that the formation is dense and the grouting volume is small. Conversely, when the formation is loose, the grouting pressure is low and the grouting volume is large. When the grouting pressure is always below 0.5 MPa and the grouting volume is abnormal, grouting should be suspended to determine the cause before deciding whether to continue grouting.

[0205] In one possible implementation, when a tunnel has been excavated and the support is damaged, reinforcement is carried out inside the tunnel. The reinforcement method includes: installing locking anchor rods to reinforce steel supports, adding concrete arches, installing φ40 steel flower pipes for grouting reinforcement in a circumferential direction, and installing self-drilling long anchor rods for grouting.

[0206] Specifically, Figure 8 This is a schematic diagram of the long anchor rod joint reinforcement proposed in this application. When the tunnel has been excavated and supported, and the arch has obviously sunk or the initial support has been damaged, measures must also be taken to reinforce the inside of the tunnel. This forms a comprehensive treatment that takes both internal and external factors into consideration. The specific process is as follows:

[0207] 1. Install locking anchors to reinforce the steel supports. Locking anchors are typically φ22 threaded steel mortar anchors, at least 3 meters in length. Each steel support should have at least 12 anchors, located at the arch haunch, arch foot, and sidewalls. The locking anchors must be welded to the steel supports.

[0208] 2. Add a concrete arch. The arch can use a steel frame, steel mesh, or a combination of steel frame and steel mesh as the load-bearing framework. Use cast-in-place concrete or sprayed concrete. The choice depends on the extent of damage. The thickness of the concrete arch should be such that it does not encroach on the secondary lining.

[0209] 3. Install φ40 steel pipes for grouting reinforcement in the annular direction. The grouting steel pipes should be arranged in a plum blossom pattern with a spacing of 1.5m x 1.5m. The length should be no less than 3m.

[0210] 4. Install self-drilling long anchor rods for grouting reinforcement. Long anchor rods are connected in pairs.

[0211] The technical solution provided by this application predicts the rock formation characteristics within a preset range in front of the tunnel; sets up monitoring positions in the tunnel, and monitors the vault subsidence data inside and outside the tunnel using convergence meters, total stations, and levels; uses a piezometer to determine the seepage rate based on the flow rate and a preset method; supports the outside of the tunnel through grouting and anchors; before excavation, performs advance support through a combination of a small lead pipe and small lead grouting; determines the excavation method based on the rock formation characteristics, excavates the tunnel, and passes through buildings. A method for tunneling through buildings using the drill and blast method is systematically designed. Compared with the prior art of tunnel excavation and passing through buildings based on experience, this application sets up multiple monitoring positions inside and outside the tunnel based on the rock formation characteristics, and then performs advance support through a combination of a small lead pipe and small lead grouting, thereby improving the safety of construction.

[0212] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0213] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0214] In the embodiments provided in this application, it should be understood that the disclosed devices / network equipment and methods can be implemented in other ways. For example, the device / network equipment embodiments described above are merely illustrative. For example, the division of the modules or units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0215] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0216] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for tunneling through a building based on the drill and blast method, characterized in that: The method comprises: Predict the rock formation characteristics within a preset range ahead of the tunnel; Set up monitoring locations in the tunnel and use convergence meters, total stations, and levels to monitor the vault subsidence data inside and outside the tunnel; Use an osmometer to determine the seepage rate based on the flow rate and the preset method; Support the outside of the cave by grouting and anchoring; Before excavation, advance support is carried out by using advance small pipes combined with small pipe grouting; According to the rock formation characteristics, the excavation method is determined, and the tunnel is excavated to pass through the building.

2. The method according to claim 1, characterized in that During tunnel excavation, when a water-rich tunnel section is encountered, the method further comprises: When the tunnel depth is less than 20m, surface grouting is used; when the depth is greater than 20m, curtain grouting and radial grouting after excavation are used. When a broken tunnel section is encountered during tunnel excavation, the method further comprises: Determine the installation location of the grouting steel flower pipe; Based on the installation position of the grouting steel flower pipe, grouting is carried out. Cement slurry is used for grouting, and the grouting is carried out in two times. The initial grouting pressure is 1MPa, and the final pressure should be stable at 2MPa.

3. The method according to claim 1, characterized in that Before excavation, advance support is performed by using an advance small pipe combined with small pipe grouting, including: The advance small guide tubes are evenly laid out along the tunnel arch excavation line, with a spacing of 30-50cm; The grouting sequence is from bottom to top. When a hole is drilled through, a grouting device is used to grout multiple holes or to plug the hole and grout the holes separately. When the pressure reaches the preset final grouting pressure and stabilizes for 10-15 minutes, and the grouting volume reaches more than 80% of the preset grouting volume, the grouting is terminated; when the grouting pressure fails to reach the preset final pressure, but the grouting volume has reached the preset grouting volume and there is no leakage, the grouting is terminated.

4. The method according to claim 1, wherein The method for predicting the rock formation characteristics within a preset range in front of the tunnel includes a seismic wave method and an advanced horizontal drilling method; The seismic wave method predicts the rock formation characteristics within a preset range in front of the tunnel by determining the location of the impact point and the sensor of the location of the impact point; The advanced horizontal drilling method obtains the front core by drilling; The rock formation characteristics within a preset range ahead are determined based on the ahead rock core.

5. The method according to claim 1, wherein The monitoring position is set up in the tunnel, and the tunnel vault subsidence data are monitored by using a convergence meter, a total station and a level, including: The monitoring position spacing is determined based on the rock formation characteristics, tunnel burial depth and excavation method; The distance between the monitoring position and the tunnel face meets the preset distance; The reading of the vault subsidence data is completed within 3 to 6 hours when the data occurs.

6. The method according to claim 1, characterized in that The preset methods include the volumetric method, the water weir method and the flow rate method. The osmometer is used to determine the seepage amount according to the flow rate and the preset method, including: When the flow rate is less than 1L / s, the volumetric method is used; when the flow rate is between 1 and 300L / s, the water measuring weir method is used; when the flow rate is greater than 300L / s or a water measuring weir cannot be set up, the leakage water is introduced into the drainage ditch and the flow velocity method is used.

7. The method according to claim 1, characterized in that The support outside the cave by grouting and anchoring includes: Use an anchor drill or handheld pneumatic rock drill to drill holes in the rock surface, with the hole position perpendicular to the rock surface; Based on the hole position and the preset support sequence, support is performed outside the hole, and the support sequence includes grouting first and then inserting anchor rods or inserting rods first and then grouting.

8. The method according to claim 1, characterized in that The excavation methods include an up-and-down step method and a three-step seven-step method.

9. The method according to claim 2, characterized in that The curtain grouting comprises: Arranging holes in the water-rich tunnel section; Use segmented forward method to drill holes first and then grout, drilling and grouting one section at a time.

10. The method according to claim 1, characterized in that When the tunnel has been excavated and the support is damaged, reinforcement is carried out inside the tunnel. The reinforcement methods include: installing locking anchor rods to reinforce steel supports, adding concrete arches, installing φ40 steel flower pipes in a circular direction for grouting reinforcement, and installing self-drilling long anchor rods for grouting.

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