Shield lateral transverse moving launching and arc-shaped pilot tunnel deslagging construction method under narrow site condition in urban area

Abstract

The invention provides a shield lateral transverse movement launching and arc-shaped pilot tunnel deslagging construction method under the narrow site condition of an urban area, which comprises the following steps: step (1), preparation before launching: site selection of a launching vertical shaft, construction of the vertical shaft and a transverse channel, and preparation of transverse movement in the transverse channel; the construction method comprises the following steps of (1), shield tunneling machine assembly and lateral transverse movement, (2), shield tunneling machine debugging, (4), counter-force device installation, (5), zero-loop segment assembly, (6), tunnel portal blocking, (7), shield 100m starting section trial tunneling, and (8) horizontal transportation. The requirements for surface excavation and excavation are reduced, and the influence of noise, vibration, soil disturbance and the like on the surrounding environment is reduced. Therefore, the influence on the existing traffic and surrounding residents and buildings can be reduced, the environmental pollution is reduced, and good economic benefits and social benefits are achieved.

Description

Technical Field

[0001] The invention relates to the field of tunnel construction, and in particular to a shield lateral transverse starting and arc guide tunnel slag removal construction method under narrow site conditions in urban areas. Background Art

[0002] In recent years, the development speed of China's urbanization process has been upgraded to a higher level, resulting in a continuous increase in the number of urban population and motor vehicles, and the problem of ground space congestion has become more and more serious. Urban subways can alleviate the pressure of traffic congestion to a large extent, and have always been highly valued. At present, in the construction of urban subway tunnels in my country, the shield method has become the most widely used construction method in the construction of urban subways due to its advantages such as high degree of mechanization and low impact on the environment. As the primary process, the shield start is the premise and basis of the shield method construction. Conventional subway projects use the station end shaft or the section main line to set up a certain length of independent shaft to achieve shield start. However, subway stations are often built in areas with dense population, congested traffic, and high-rise buildings. Conventional shield start occupies the main roads of the city for a long time, which will make it difficult for ground vehicles to drive on both sides of the shaft construction site, which is very likely to cause traffic jams. Summary of the invention

[0003] The technical problem solved by the present invention is to provide a shield lateral transverse starting and arc guide tunnel slag removal construction method under narrow site conditions in urban areas, so as to solve the problems raised in the above-mentioned background technology.

[0004] The technical problem solved by the present invention is achieved by adopting the following technical solution: a shield lateral shift start and arc guide tunnel slag discharge construction method under narrow site conditions in urban areas, comprising the following steps:

[0005] Step (1) Preparation before departure, including: site selection of departure shaft, construction of shaft and transverse passage, and preparation for transverse movement in transverse passage;

[0006] Step (2) assembling and lateral movement of the shield machine, including: hoisting and lateral movement of the shield;

[0007] Step (3). Shield machine debugging, which includes: shield machine no-load debugging, electrical part operation debugging, hydraulic part operation debugging, shield machine load debugging;

[0008] Step (4). Install the reaction device. The specific installation steps are as follows:

[0009] 1) Pre-embed a steel plate at the upper part of the expanded end of the dark excavated tunnel, and weld a lifting lug on the steel plate with round steel;

[0010] 2) Use a fall chain to lift the two parts of the upper half of the reference ring, connect the two parts with high-strength bolts, and then install the two parts of the lower half of the reference ring to form a complete circle;

[0011] 3) The surveyor locates the elevation and position of the reference ring and places it at the designed position as required;

[0012] 4) Use diagonal braces and straight braces to connect and fix the reference ring to the embedded steel plate;

[0013] Step (5). Assemble the zero-ring segments. The zero-ring segments are assembled in front of the shield tail brush and then moved backward to the end face of the reaction reference ring.

[0014] Step (6). Tunnel door blocking, the specific installation steps are as follows:

[0015] 1) The lateral movement of the shield machine starts from inside the tunnel, and the waterproof curtain is not installed. The tunnel door is used to block the waterproof curtain;

[0016] 2) After the zero ring segment is installed, use the oil cylinder to push it to the end face of the reaction reference ring. The zero ring segment will be 70 cm out of the shield tail. Fix the zero ring segment on the reference ring to prevent deviation.

[0017] 3) The gap between the zero-ring segment and the primary lining of the tunnel is sealed by brickwork, and steel bars are implanted on the primary lining around the outside of the brick wall to ensure the stability of the brickwork structure. Four grouting pipes are reserved around the tunnel portal;

[0018] 4) The shield machine advances normally, and the tail of the shield moves to the end of the primary lining of the dark excavation. The gaps in the segments are first filled through the synchronous grouting pipe, and then secondary grouting is carried out through the reserved grouting pipe and the grouting holes of the segments to seal the tunnel entrance.

[0019] Step (7). Test excavation of the 100m initial section of the shield machine, including: 100m test excavation control of the shield machine, calculation of soil bin pressure, control of excavation volume, soil improvement of the initial excavation section, and control of the shield machine posture during initial excavation;

[0020] Step (8) Horizontal transportation: In the initial stage of lateral movement, the conditions for excavation by electric locomotive are not met. A transport belt is installed on the right side of the trolley, and the slag port of the trolley is modified to add an inclined chute; a transport belt is installed at the cross channel position, and the slag on the dark tunnel transport belt is transferred to the cross channel transport belt, which can ensure the continuous excavation of the shield machine. The slag bucket is placed at the hoisting wellhead, and moved to the bottom of the belt interface during construction to receive the slag; when the interval shield machine has completed 100 rings of shield excavation, the construction of the lateral arc guide tunnel is completed. At this time, a turnout can be laid in the guide tunnel to change the horizontal transportation method in the tunnel, and the excavation and segment transportation work can be completed through the lateral arc guide tunnel.

[0021] Furthermore, the preparation for transverse movement in the transverse channel in step (1) includes site leveling, rail laying, and starting frame installation. The starting bracket is placed on the track with its center position coinciding with the center position of the transverse channel. To prevent the starting bracket from moving during the assembly of the shield machine, the starting bracket is reinforced with I-beams in the axial and longitudinal directions, and the steel is fixed to the main structure of the station.

[0022] Furthermore, the shield body lateral movement in step (2) includes:

[0023] 1) After the shield body is assembled, push the shield machine forward as a whole on the bracket, and stop when the tail of the shield exceeds the tail of the bracket by 180mm;

[0024] 2) Cut off all the reinforcing supports of the starting bracket, apply butter on the transverse track, and start pushing horizontally using the track clamping cylinder;

[0025] 3) Use four rail clamping cylinders placed on the rails, and use the reverse thrust provided by the clamping rails to act on the starting bracket, so that the starting bracket and the shield body move horizontally as a whole, and stop when the horizontal channel moves horizontally to the right line positive hole position;

[0026] 4) The width of the transverse passage does not meet the installation conditions of the screw conveyor and equipment bridge wellhead. The screw conveyor and equipment bridge need to be moved obliquely through the transverse passage, and the rotary machine is pulled to the main line position.

[0027] Furthermore, the number of reaction supports required for the installation of the reaction device in step (4) is calculated. The actual normal thrust of the initial excavation does not exceed 1000t, and assuming that the steel ring plays a balancing role in stress, considering the uneven stress and safety factor, the total thrust can be calculated as 2000t; each force point P is calculated by an average distribution of 2000t, and the average distribution of the force points is 2000 / n. The stiffness of the reaction steel ring itself can meet the requirements and will not be deformed due to the thrust; the number of reaction supports is n, the angle of the diagonal support is α, and the effective cross-sectional area is βmm 2 , so the maximum compressive stress on the brace is:

[0028] F=2000 / n×cosα÷β≤Steel design strength 215N / mm 2 , so the number of reaction supports is calculated while meeting the stability requirements of the reaction supports.

[0029] Furthermore, in the step (7), the shield machine is controlled to conduct a 100-meter trial excavation. When the shield machine is installed and debugged and everything is normal, it enters the tunnel excavation state, and the 100-meter starting section of the shield machine is used as the shield machine advancement test section. During the construction of this experimental section, attention should be paid to the setting of the advancement parameters and the relationship between the ground deformation and the construction parameters, and various technical data during advancement should be collected, counted and analyzed.

[0030] Furthermore, in the soil bin pressure calculation method in step (7), 1) the soil pressure of the stratum, the horizontal lateral force of the stratum is: σ horizontal lateral force = k × γ × h where: h = 0.45 × 2 S-1 ω; S--surrounding rock grade, such as Grade IV surrounding rock, then S = 4; h--surrounding rock pressure calculation height; γ--surrounding rock weight; ω--width influence coefficient, and ω = 1 + i (B-5); B--tunnel net width, in meters;

[0031] i--Based on B=5m, when B<5m, take i=0.2, when B>5m, take i=0.1; k--Horizontal lateral pressure coefficient determined according to surrounding rock grade,

[0032] 2) Groundwater pressure

[0033] σw before cutter disc = qγh, where: q is an empirical value determined based on the permeability coefficient of the soil layer, q = 0.5~1.0 for sandy soil, q = 0.1~0.5 for clay soil, and q = 0~0.5 for weathered rock layer; γ is the bulk density of water; h is the height of the groundwater level from the top of the cutter disc.

[0034] 3) Preparation pressure

[0035] Due to many unforeseen factors in construction, the construction soil pressure is smaller than the static soil pressure in the original soil. According to construction experience, when calculating the soil pressure in areas with strict settlement requirements, a pressure of 0.01 to 0.02 MPa is usually considered as a reserve pressure on the basis of theoretical calculations.

[0036] 4) According to the tunnel burial depth, the upper soil bin pressure is set as: P = stratum soil pressure + groundwater pressure + reserve pressure.

[0037] Furthermore, in step (7), the excavation volume is controlled. During the excavation process, the excavation is carried out strictly in accordance with the soil bin pressure specified in the technical briefing, and the excavation and excavation speeds are controlled to avoid soil pressure fluctuations. During the excavation process, the shield driver records the cylinder stroke difference before and after each bucket of soil, and judges whether there is over-excavation based on this. During the excavation process, the shield driver judges whether there is over-excavation by communicating with the earthworker and observing the soil condition in the soil bin. During the excavation construction, ground monitoring is strengthened, and it is judged based on the monitoring data whether the setting of the soil bin pressure and the excavation volume meet the requirements. The engineer inspects each bucket of soil and takes soil samples, and analyzes and judges based on the soil condition. If there is any abnormality, reasonable measures are taken in time to ensure the control of the excavation volume.

[0038] Furthermore, the soil improvement at the initial excavation stage in step (7) includes:

[0039] 1) Grease at the tail of the shield: In order to prevent groundwater and synchronous grouting slurry from entering the tunnel from the tail of the shield when the shield is advancing, grease is injected at the wire brush position of the tail of the shield to achieve the sealing function of the shield. In order to safely and smoothly complete the excavation task of the interval tunnel, the pressure injection of grease at the tail of the shield must be done well. Grease should be injected frequently during construction, and the grease at the tail of the shield should follow the principle of small amounts and multiple times.

[0040] 2) Foaming agent: When the cutter head of the shield machine enters the reinforcement area, the torque of the cutter head increases, and foam or water needs to be injected into the front of the excavation chamber to improve the soil. In addition, when the soil layer is hard, it will affect the normal operation of the earth pressure sensor in the soil chamber, which will bring about a series of problems such as excessive surface heave and subsidence. At this time, foam or water needs to be added while advancing so that the earth pressure sensor can normally respond to the earth pressure of the excavation surface. The proportion of foaming agent used is generally composed of the foam solution: 3% foam additive, 97% water; Ⅰ. Foam composition: a mixture of 90-95% compressed air and 5-10% foam solution; Ⅱ. The amount of foam injected is calculated according to the excavation volume: 300L / m 3 .

[0041] Furthermore, the shield machine attitude control at the beginning of excavation in step (7) includes: ensuring that the shield machine is constructed at a balanced and uniform speed while ensuring good control of the front settlement of the shield machine, and the shield machine attitude changes should not be too large or too frequent; checking the advance amount of the pipe segment every 5 rings, not correcting it hastily or violently during advancement, paying more attention to measuring the shield tail gap, and the change in the relative regional oil pressure gradually changes with the slag discharge amount and the jack stroke to reduce the impact of the shield construction on the ground.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows: the shield lateral shifting starting construction can flexibly set the position of the shield starting shaft, thereby avoiding the instability of the shield section due to the instability of the station shield starting shaft plan, and also avoiding the work of traffic diversion and pipeline relocation, saving construction costs and construction period. This method can adopt different lateral shifting methods for different components to reduce the time used. At the same time, when the shield is shifted laterally, the internal pipelines between the platforms can be connected, shortening the starting time. The non-negative ring starting technology in the method can complete the starting with a simple starting reaction force device, and the zero-ring segment can be directly installed without removal in the later stage, saving construction materials. The excavation of the transport belt in the early stage of starting and the lateral arc guide tunnel in the later stage effectively solve the problem of difficulty in lateral shifting and horizontal transportation.

[0043] The shield lateral movement launch does not require an additional launch area and can be constructed in a limited site space. This method is particularly beneficial for urban construction with limited land resources, and can maximize the use of existing land. Compared with the traditional launch method, the shield lateral movement launch reduces the need for surface excavation and excavation, and reduces the impact of noise, vibration and soil disturbance on the surrounding environment. Therefore, it can reduce the impact on existing traffic and surrounding residents and buildings, reduce environmental pollution, and has good economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a structural schematic diagram of the present invention.

[0045] Figure 2 It is a plan view of the shield body lateral displacement of the present invention.

[0046] Figure 3 It is a cross-sectional view of the shield body of the present invention.

[0047] Figure 4 It is a schematic diagram of the transverse movement and rotation of the screw conveyor of the present invention.

[0048] Figure 5 It is a schematic diagram of the installation of the reaction frame of the present invention.

[0049] Figure 6 It is a schematic diagram of the installation position of the conveyor belt of the present invention.

[0050] Figure 7 It is a plan view of the lateral arc guide tunnel of the present invention. DETAILED DESCRIPTION

[0051] In order to make the technical means for realizing the present invention, the creative features, the objectives and effects to be achieved easy to understand, the present invention is further explained below in conjunction with specific diagrams. In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection, or an integral connection can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be internal communication between two elements.

[0052] like Figures 1 to 7 As shown in the figure, the shield lateral shift start and arc guide tunnel slag discharge construction method under the narrow site conditions in the urban area includes the following steps:

[0053] Step (1). Preparation before departure

[0054] 1. Location of the starting shaft:

[0055] The site selection is not restricted by location and space, but must meet the following requirements:

[0056] 1) The size of the starting shaft must meet the hoisting requirements to prevent the shield machine from being unable to be hoisted;

[0057] 2) The clearance of the transverse passage must meet the requirements of the lateral movement of the shield machine, and the height of the shield body + the starting frame must be less than the clearance of the transverse passage;

[0058] 3) Lateral movement needs to be simulated in advance to prevent lateral movement from being obstructed.

[0059] 2. Construction of vertical shaft and horizontal passage:

[0060] During the construction of vertical shafts and horizontal passages, attention should be paid to the fact that the strength of the secondary lining must meet the requirements, the ground elevation must be consistent without obvious bumps, and blasting should be avoided as much as possible to facilitate the subsequent horizontal movement of the shield.

[0061] 3. Preparation for horizontal movement in the horizontal channel:

[0062] 1) Site leveling

[0063] Check the dewatering wells and pump water to ensure that the water level is lower than the working area and that there is no water overflow on site. Since the horizontal movement of the shield machine requires a high degree of flatness in the casting of the horizontal channel plate, yellow sand is spread on the ground, and the steel plate is laid on the yellow sand after leveling; the height of the yellow sand should be 50mm. If the bedding layer is too thick, the foundation will be too soft, and the steel plate will be deformed due to heavy pressure during the horizontal movement of the shield. If it is too thin, the horizontality of the steel plate laying surface cannot be guaranteed.

[0064] 2) Laying rails

[0065] After the steel plate is laid, multiple steel rails are laid on the steel plate to serve as transverse tracks for the starting bracket to move horizontally.

[0066] The transverse width of the rails is determined based on the width of the transverse channel and the length of the starting bracket. The rails on both sides are laid to serve as the track for the trolleys to move transversely; the rails in the middle are located on the center line of the transverse channel, and the remaining rails are evenly spaced.

[0067] The rails are fixed on the steel plates by welding with L plates, with a spacing of 1 meter. The ends of the rails are pushed against the end wall of the transverse channel, and steel plates are placed between the rails and the side walls to prevent the rails from moving backwards during the transverse movement of the shield machine.

[0068] In order to reduce the friction during the lateral movement of the shield machine, butter is applied to the rail surface; the joints of the rails are polished to avoid jamming of the starting bracket.

[0069] 3) Installation of the launch frame

[0070] The starting bracket is placed on the track, with its center coinciding with the center of the transverse passage. To prevent the starting bracket from moving during the assembly of the shield machine, the starting bracket is reinforced with I-beams in both the axis and longitudinal direction, and the steel is fixed to the main structure of the station.

[0071] Step (2). Shield machine assembly and lateral movement

[0072] 1. Shield hoisting

[0073] The launching frame is hoisted down the well and placed at the wellhead. At the same time, the tail shield, middle shield, front shield and cutterhead are hoisted and connected in sequence; after the shield body is installed, the shield body is welded to the launching frame.

[0074] 2. Shield body lateral movement

[0075] 1) After the shield body is assembled, push the shield machine forward as a whole on the bracket, and stop when the shield tail exceeds the tail of the bracket by 180mm.

[0076] 2) Cut off all the reinforcing supports of the starting bracket, apply butter on the transverse track, and start pushing horizontally using the track clamping cylinder.

[0077] 3) Use 4 rail clamping cylinders placed on the rails, and use the reverse thrust provided by the clamping rails to act on the starting bracket, so that the starting bracket and the shield body move horizontally as a whole, and stop when the horizontal channel moves horizontally to the right line positive hole position. See the schematic diagram of the shield body horizontal movement plane and section for details. Figure 2 , Figure 3 .

[0078] 4) The width of the horizontal channel does not meet the installation conditions of the screw conveyor and equipment bridge wellhead. The screw conveyor and equipment bridge need to be moved diagonally through the horizontal channel and the rotating machine is pulled to the main line position. See the schematic diagram of the horizontal movement and rotation of the screw conveyor for details. Figure 4 .

[0079] Step (3) Shield machine debugging

[0080] 1. No-load debugging of shield machine

[0081] After the shield machine is assembled and connected, it can be debugged without load. The purpose of no-load debugging is to check whether the equipment can operate normally. The main debugging contents are: hydraulic system, lubrication system, cooling system, power distribution system, grouting system, mud and water treatment system, and calibration of various instruments.

[0082] Electrical part operation and debugging:

[0083] Check power supply → Check motor → Subsystem parameter setting and test run → Whole machine test run → Debug again.

[0084] Hydraulic part operation and debugging:

[0085] Propulsion and articulation system → screw conveyor → segment erector → segment crane and towing load commissioning.

[0086] 2. Shield machine load debugging

[0087] After the no-load debugging is completed and it is proved that the shield machine and its auxiliary equipment meet the preliminary requirements, the load debugging of the shield machine can be carried out. The main purpose of load debugging is to check the load capacity of various pipelines and sealing equipment, and to further improve the debugging items that cannot be completed by no-load debugging, so that the various working systems and auxiliary systems of the shield machine can reach the working state that meets the normal production requirements.

[0088] Step (4) Installation of reaction device

[0089] 1. After the trolley is hoisted and moved horizontally, the shield machine is pushed upward as a whole by the rail clamping cylinder until the shield body enters the dark excavation starting guide tunnel. The reaction frame is transported in parts for installation.

[0090] 2. Due to the narrow space of the dark excavated tunnel, the reaction device is a reference ring, which is divided into four parts and installed 15 cm away from the tunnel entrance.

[0091] 3. Calculation of the number of reaction supports required

[0092] The actual normal thrust of excavation is generally no more than 1000t, and assuming that the steel ring plays a balanced role in stress, considering the uneven force and safety factor, the total thrust can be calculated as 2000t. Each force point P is calculated by an average distribution of 2000t, and the average distribution of the force points is 2000 / n. The stiffness of the reaction steel ring itself can meet the requirements and will not be deformed due to the thrust.

[0093] The number of reaction braces is n, the angle of the brace is α, and the effective cross-sectional area is βmm 2 , so the maximum compressive stress on the brace is:

[0094] F=2000 / n×cosα÷β≤Steel design strength 215N / mm 2

[0095] Therefore, the number of reaction supports is calculated while meeting the stability requirements of the reaction supports.

[0096] 4. The specific installation steps are as follows:

[0097] 1) Pre-embed a steel plate at the upper part of the expanded end of the dark excavated tunnel, and weld a lifting lug on the steel plate with round steel;

[0098] 2) Use a fall chain to lift the two parts of the upper half of the reference ring, connect the two parts with high-strength bolts, and then install the two parts of the lower half of the reference ring to form a complete circle;

[0099] 3) The surveyor locates the elevation and position of the reference ring and places it at the designed position as required;

[0100] 4) Use diagonal braces and straight braces to connect and fix the reference ring to the embedded steel plate.

[0101] 5. Key points for controlling the installation of reaction support:

[0102] 1) When installing the reaction force reference ring, first use the theodolite to calibrate the verticality in both directions so that the plane formed by it is perpendicular to the propulsion axis of the shield machine;

[0103] 2) When installing the reaction force benchmark, the left and right deviation of the reaction force frame should be controlled within ±10mm, the elevation deviation should be controlled within ±5mm, and the up and down deviation should be controlled within ±10mm;

[0104] 3) After the zero ring touches the reference ring, observe whether it is tightly fitted.

[0105] Step (5) Zero ring segment assembly

[0106] 1. After the reaction reference ring is installed, the zero ring segment is installed. The zero ring segment is pushed to the end face of the reaction reference ring by moving the whole ring in front of the shield tail brush.

[0107] 2. To ensure uniform clearance between the inner diameter of the shield tail and the outer diameter of the segment, round steel should be welded inside the shield shell at the lower part of the shield tail when assembling the zero ring segment. One round steel should be welded at each end of the B1, B2, and B3 standard blocks when assembling the zero ring segment. The round steel should be placed along the excavation direction of the shield, with the tail near the brush of the shield tail. The round steel should be spot welded to the shield shell at two points near the support shoe to facilitate the removal of the zero ring segment after installation.

[0108] 3. The capping block F of the zero-ring segment is at the 16 o'clock direction, and the centerline of the bottom block B2 coincides with the plumb centerline of the tunnel. When measuring and positioning the zero-ring segment, the rear end face of the segment should be perpendicular to the centerline of the line. The centerline of the tunnel is determined at the location of the segment installation machine, and the centerline nut of the bottom block B2 corresponds to it to ensure that the installation angle of the segment meets the requirements in the later stage.

[0109] 4. B1 is on the left side of the shield tail, and B3 is on the right side of the shield tail. After each segment is installed, immediately insert the segment annular connection bolt into the connection hole, put on the nut and tighten it with a pneumatic wrench. After the segment is installed in place, the push jack shoe at the corresponding position should be extended in time to fix the segment to prevent the segment from overturning, and then the segment assembly machine can be removed.

[0110] 5. When installing the two adjacent blocks and one capping block on the top of the zero ring segment, the zero ring segment does not have longitudinal bolts to fix the segment, so first connect it with the circumferential bolts of the standard block. The adjacent blocks are lifted on site to facilitate the insertion of the capping block, and the upper part of the adjacent blocks is welded to the shield with an L-shaped steel plate. After the capping block is in place, it is connected with bolts, the L-shaped steel plate is cut off, and the two adjacent blocks fall down and overlap closely with the capping block.

[0111] 6. Use the assembly mode to push the zero ring segment backward, press it against the reaction reference ring, and connect it with the end face of the reaction reference ring. Since there is a certain gap at the bottom of the segment that has escaped from the shield tail, in order to prevent the zero ring segment from sinking after being completely pushed out of the shield tail, positioning blocks are welded on both sides of the zero ring segment and the bottom of the reference ring to hold up the zero ring segment.

[0112] 7. When the pipe segment passes through the tail brush, pay attention to inject grease into the tail brush in time to ensure that the tail brush is not damaged during the process.

[0113] Step (6) Sealing the tunnel door

[0114] 1. The lateral movement of the shield starts from inside the tunnel, and no water-stop curtain is installed. The tunnel door is used to seal the water-stop curtain instead.

[0115] 2. After the zero ring segment is installed, use the oil cylinder to push it as a whole to the end face of the reaction force reference ring. The zero ring segment will be 70 cm out of the shield tail and fixed on the reference ring to prevent deviation.

[0116] 3. The gap between the zero-ring segment and the primary lining of the tunnel is sealed with bricks. Steel bars are implanted on the primary lining around the outside of the brick wall to ensure the stability of the brick structure. Four grouting pipes are reserved around the tunnel portal.

[0117] 4. The shield machine advances normally, and the tail of the shield moves to the end of the initial lining of the dark excavation. The gaps in the segments are first filled through the synchronous grouting pipe, and then secondary grouting is carried out through the reserved grouting pipe and the grouting holes of the segments to seal the tunnel entrance.

[0118] Step (7) Shield tunneling test at the 100m starting section

[0119] 1. Shield 100m trial excavation control

[0120] When the shield is installed and debugged and everything is normal, it enters the tunnel excavation state. The 100-meter starting section of the shield is used as the shield advancement test section. During the construction of this experimental section, attention should be paid to the setting of advancement parameters and the relationship between ground deformation and construction parameters. Various technical data during advancement should be collected, counted and analyzed, and efforts should be made to master the operating performance of shield machinery and equipment in a relatively short period of time and determine the setting range of construction parameters for shield advancement. The key tasks of this stage of construction are to do the following:

[0121] 1) Master the operation method and mechanical properties of the shield machine in the shortest possible time and improve the imperfect parts of the shield.

[0122] 2) Understand and recognize the geological conditions of the soil layer that the tunnel passes through, and master the construction method of earth pressure balance shield under this geological condition.

[0123] 3) Through the construction of this section, strengthen the monitoring and analysis of ground deformation, master the shield advancement parameters and the amount of synchronous grouting. During the trial push period, ensure that the shield passes at a uniform speed as much as possible, reduce the shield correction amount and number of corrections, so as to control the shield posture well, while ensuring good control of the shield front settlement.

[0124] 2. Calculation method of soil bin pressure

[0125] 1) Soil pressure

[0126] In my country's railway tunnel design specifications, based on a large amount of construction experience and on the basis of Terzaghi's earth pressure theory, a comprehensive rock mass classification method based on comprehensive rock mass physical properties is proposed. Tunnels are divided into deep buried tunnels and shallow buried tunnels according to the different buried depths of the tunnels. Different calculation methods are then used to calculate the construction earth pressure according to the specific conditions of the tunnels.

[0127] For deep buried tunnels, the vertical distributed loosening pressure and horizontal loosening pressure of the surrounding rock are generally calculated according to the tunnel surrounding rock classification and tunnel structural parameters in accordance with the calculation formula of the "Railway Tunnel Design Code".

[0128] The horizontal lateral force of the formation is: σ horizontal lateral force = k × γ × h

[0129] Where: h = 0.45 × 2 S-1 ω

[0130] S--surrounding rock grade, such as Grade IV surrounding rock, then S = 4;

[0131] h--Calculation height of surrounding rock pressure;

[0132] γ--weight of surrounding rock;

[0133] ω--width influence coefficient, and ω=1+i(B-5);

[0134] B--net width of the tunnel, in meters;

[0135] i--Based on B=5m, when B<5m, take i=0.2, when B>5m, take i=0.1;

[0136] k--Horizontal lateral pressure coefficient determined according to the surrounding rock level, see the following table for details:

[0137]

[0138] 2) Groundwater pressure

[0139] σw before the cutter head = qγh

[0140] Where: q is an empirical value determined based on the permeability coefficient of the soil layer, sandy soil q = 0.5 ~ 1.0, clay soil q = 0.1 ~ 0.5, weathered rock layer q = 0 ~ 0.5;

[0141] γ--bulk density of water;

[0142] h--The height of the groundwater level from the top of the cutter disc.

[0143] 3) Preparation pressure

[0144] Due to many unforeseen factors in construction, the construction soil pressure is less than the static soil pressure in the original soil. According to construction experience, when calculating the soil pressure in areas with strict settlement requirements, a pressure of 0.01 to 0.02 MPa is usually considered as a preliminary pressure based on theoretical calculations.

[0145] 4) According to the tunnel burial depth, the upper soil bin pressure is set to

[0146] P = soil pressure + groundwater pressure + preparation pressure

[0147] 3. Control of excavated quantity

[0148] 1) The size of the excavation volume is the most intuitive basis for judging whether the shield machine has over-excavation or under-excavation. During construction, the deviation of the excavation volume of each ring should be strictly controlled to not exceed 5% of the theoretical value, and under-excavation is not allowed. In addition, according to the advancement speed of the shield machine, the speed of the screw conveyor, the gate opening rate and the excavation volume and other parameters should be reasonably selected to ensure that the excavation and excavation are synchronized during the process.

[0149] 2) During the construction process, a large amount of additives need to be added to improve the soil, so the theoretical value of the excavated volume should be the design value multiplied by a certain loose coefficient + the amount of bentonite additives. The loose coefficient is selected according to the different strata.

[0150] 3) Control measures:

[0151] ① During the excavation process, excavation shall be carried out strictly in accordance with the soil bin pressure specified in the technical briefing, and the excavation and excavation speed shall be well controlled to avoid soil pressure fluctuations;

[0152] ② The shield driver should record the difference in cylinder stroke before and after each bucket of soil during excavation, and use this to determine whether there is over-excavation;

[0153] ③ During the excavation process, the shield driver will make a judgment on whether there is over-excavation by communicating with the earthwork inspector and observing the soil condition in the soil bucket;

[0154] ④ Strengthen ground monitoring during excavation construction, and judge whether the setting of soil bin pressure and excavation volume meet the requirements based on monitoring data;

[0155] ⑤ The engineer shall inspect each bucket of soil and take samples of the excavated soil, and make analysis and judgment based on the excavated soil conditions. If there are any abnormal conditions, reasonable measures shall be taken in time to ensure the control of the amount of soil discharged.

[0156] 5. Soil improvement at the initial excavation stage

[0157] 1) Shield tail grease

[0158] In order to prevent groundwater and synchronous grouting slurry from entering the tunnel from the shield tail during shield advancement, shield tail grease is injected at the shield tail wire brush position to achieve the shield's sealing function. In order to safely and smoothly complete the tunneling task of the interval tunnel, the shield tail grease injection work must be done well. Grease should be injected frequently during construction, and the shield tail grease should follow the principle of small amounts and multiple times.

[0159] 2) Foaming agent

[0160] When the shield machine cutterhead enters the reinforcement area, the cutterhead torque increases, and foam or water needs to be injected into the front of the excavation chamber to improve the soil. In addition, when the soil layer is hard, it will affect the normal operation of the earth pressure sensor in the soil chamber, which will cause a series of problems such as excessive surface heave and subsidence. At this time, foam or water needs to be added while advancing so that the earth pressure sensor can normally respond to the earth pressure of the excavation surface. The proportion of foaming agent used is generally the composition of the foam solution: 3% foam additive and 97% water.

[0161] Ⅰ. Foam composition: a mixture of 90-95% compressed air and 5-10% foam solution.

[0162] Ⅱ. The amount of foam injected is calculated based on the excavation volume: 300L / m 3 .

[0163] 6. Shield machine attitude control during initial excavation

[0164] 1) Check the stability of the reaction frame of the shield machine, check whether the guide rails that prevent the shield machine from "falling" are firmly constructed and properly positioned, and check whether the anti-twist device on the shield tail shell is firmly welded.

[0165] 2) Maintain balanced thrust of the four thrust cylinders of the shield machine, ensure that the displacement of the cutter head center and the shield tail center is within the allowable deviation range, and use as few correction measures as possible during the initial excavation stage.

[0166] 3) Under the condition of ensuring good control of the front settlement of the shield, the shield should be constructed at a balanced and uniform speed, and the shield posture should not change too much or too frequently. Check the advance amount of the pipe segment every 5 rings, do not correct it urgently or violently when advancing, pay more attention to measuring the gap at the shield tail, and the change of the oil pressure in the relative area will gradually change with the slag discharge and the jack stroke to reduce the impact of the shield construction on the ground.

[0167] 5.2.8 Horizontal transport

[0168] 1. In the initial stage of lateral movement, the conditions for excavation with an electric locomotive are not met. A transport belt is installed on the right side of the trolley, the slag port of the trolley is modified, and an inclined chute is added; a transport belt is installed at the cross channel position, and the slag on the dark tunnel transport belt is transferred to the cross channel transport belt, which can ensure the continuous excavation of the shield machine. The slag bucket is placed at the hoisting wellhead, and moved to the bottom of the belt interface during construction to receive the slag. See the schematic diagram of the transport belt installation position for details. Figure 6 .

[0169] 2. When the shield tunneling of the interval tunnel is completed for about 100 rings, the construction of the lateral arc guide tunnel is completed. At this time, a turnout can be laid in the guide tunnel to change the horizontal transportation mode in the tunnel, and the excavation and segment transportation work can be completed through the lateral arc guide tunnel. See the plan layout of the lateral arc guide tunnel for details. Figure 7 .

[0170] The shield lateral shifting and starting construction method under complex strata under restricted conditions of the present invention is divided into three stages. The first stage is the preparation stage, including the site selection of the shaft, the construction of the shaft and the transverse channel, and the preparation for translation in the transverse channel. The second stage is the lateral shifting stage of the shield machine. The shield body is hoisted into the starting shaft for assembly. The shield body is pushed horizontally to the tunnel mainline position through the transverse channel, and then pushed as a whole to the starting position. The third stage is the starting stage of the shield. The reaction force device is installed, the tunnel door is blocked, and the range of 100m after the start is used as the trial excavation section to determine the setting range of the construction parameters for shield advancement.

[0171] The shield is hoisted into the shaft using the starting shaft on the side of the section, and the shield machine's lateral movement technology is used to push the entire shield through the cross channel to the tunnel mainline position. Screw conveyors, equipment bridges, and trolleys are installed at the cross channel and tunnel mainline positions. After completion, the entire shield is pushed to the starting position, and the negative-loop starting technology is used inside the tunnel. At the same time, a lateral arc guide tunnel is used for feeding and slag transportation, and finally the shield starting construction is completed.

[0172] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. The shield lateral shift start and arc guide tunnel slag discharge construction method under narrow site conditions in urban areas is characterized by: The following steps are involved: Step (1) Preparation before departure, including: site selection of departure shaft, construction of shaft and transverse passage, and preparation for transverse movement in transverse passage; Step (2) assembling and lateral movement of the shield machine, including: hoisting and lateral movement of the shield; Step (3). Shield machine debugging, which includes: shield machine no-load debugging, electrical part operation debugging, hydraulic part operation debugging, shield machine load debugging; Step (4). Install the reaction device. The specific installation steps are as follows: 1) Pre-embed a steel plate at the upper part of the expanded end of the dark excavated tunnel, and weld a lifting lug on the steel plate with round steel; 2) Use a fall chain to lift the two parts of the upper half of the reference ring, and connect the two parts with high-strength bolts. After completion, install the two parts of the lower half of the reference ring to form a complete circle; 3) The surveyor locates the elevation and position of the reference ring and places it at the designed position as required; 4) Use diagonal braces and straight braces to connect and fix the reference ring to the embedded steel plate; Step (5). Assemble the zero-ring segments. The zero-ring segments are pushed to the end face of the reaction reference ring by moving the whole ring in front of the shield tail brush and moving it backward; Step (6). Tunnel door blocking, the specific installation steps are as follows: 1) The lateral movement of the shield machine starts from inside the tunnel, and the waterproof curtain is not installed. The tunnel door is blocked to replace the waterproof curtain; 2) After the zero ring segment is installed, use the oil cylinder to push it to the end face of the reaction reference ring as a whole. The zero ring segment will be 70 cm out of the shield tail. Fix the zero ring segment on the reference ring to prevent deviation; 3) The gap between the zero-ring segment and the primary lining of the tunnel is sealed by brickwork, and steel bars are implanted on the primary lining around the outside of the brick wall to ensure the stability of the brickwork structure. Four grouting pipes are reserved around the tunnel portal; 4) The shield machine advances normally, and the shield tail moves to the end of the dark excavation primary lining. The gaps in the segments are first filled through the synchronous grouting pipe, and then secondary grouting is performed through the reserved grouting pipe and the segment grouting holes to seal the tunnel door; Step (7). Test excavation of the 100m initial section of the shield machine, including: 100m test excavation control of the shield machine, calculation of soil bin pressure, control of excavation volume, soil improvement of the initial excavation section, and control of the shield machine posture during initial excavation; Step (8). Horizontal transportation: In the initial stage of lateral movement, the conditions for excavation by electric locomotive are not met. A transport belt is installed on the right side of the trolley, the slag outlet of the trolley is modified, and an inclined chute is added; a transport belt is installed at the cross channel position, and the slag on the dark tunnel transport belt is transferred to the cross channel transport belt, which can ensure the continuous excavation of the shield machine; the slag bucket is placed at the hoisting wellhead, and moved to the bottom of the belt interface during construction to receive the slag; when the interval shield machine has completed 100 rings of shield excavation, the lateral arc guide tunnel construction is completed. At this time, a switch can be laid in the guide tunnel to change the horizontal transportation method in the tunnel, and the excavation and segment transportation work can be completed through the lateral arc guide tunnel.

2. The shield lateral shifting start and arc-shaped guide tunnel slag removal construction method under narrow urban site conditions according to claim 1 is characterized by: The preparation for transverse movement in the transverse channel in step (1) includes site leveling, rail laying, and starting frame installation. The starting bracket is placed on the track with its center position coincident with the center position of the transverse channel. To prevent the starting bracket from moving during the assembly of the shield machine, the starting bracket is reinforced with I-beams in the axial and longitudinal directions, and the steel is fixed to the main structure of the station.

3. The shield lateral shifting start and arc-shaped guide tunnel slag removal construction method under narrow urban site conditions according to claim 1 is characterized by: The shield body lateral movement in step (2) includes: 1) After the shield body is assembled, push the shield machine forward as a whole on the bracket, and stop when the tail of the shield exceeds the tail of the bracket by 180mm; 2) Cut off all the reinforcing supports of the starting bracket, apply butter on the transverse track, and start pushing horizontally using the track clamping cylinder; 3) Use four rail clamping cylinders placed on the rails, and use the reverse thrust provided by the clamping rails to act on the starting bracket, so that the starting bracket and the shield body move horizontally as a whole, and stop when the horizontal channel moves horizontally to the right line positive hole position; 4) The width of the transverse passage does not meet the installation conditions of the screw conveyor and equipment bridge wellhead. The screw conveyor and equipment bridge need to be moved obliquely through the transverse passage, and the rotary machine is pulled to the main line position.

4. The shield lateral shifting start and arc-shaped guide tunnel slag removal construction method under narrow urban site conditions according to claim 1 is characterized by: The number of reaction supports required for the installation of the reaction device in step (4) is calculated. The actual normal thrust of the initial excavation does not exceed 1000t. It is assumed that the steel ring plays a balancing role in stress. Considering the uneven stress and safety factor, the total thrust can be calculated as 2000t. Each stress point P is evenly distributed and calculated as 2000t, and the average distribution of the stress points is 2000 / n. The stiffness of the reaction steel ring itself can meet the requirements and will not be deformed due to the thrust. The number of reaction supports is n, the angle of the diagonal support is α, and the effective cross-sectional area is βmm. 2 Therefore, the maximum compressive stress of the diagonal brace is: F = 2000 / n × cosα÷β≤ steel design strength 215N / mm 2 , so the number of reaction supports is calculated while meeting the stability requirements of the reaction supports.

5. The shield lateral shifting start and arc-shaped guide tunnel slag removal construction method under narrow urban site conditions according to claim 1 is characterized by: In the step (7), the shield machine is controlled to conduct a 100-meter trial excavation. When the shield machine is installed and debugged and everything is normal, it enters the tunnel excavation state, and the 100-meter starting section of the shield machine is used as the shield machine advancement test section. During the construction of this test section, attention should be paid to the setting of the advancement parameters and the relationship between the ground deformation and the construction parameters, and various technical data during advancement should be collected, counted and analyzed.

6. The shield lateral shifting start and arc-shaped guide tunnel slag removal construction method under narrow urban site conditions according to claim 1 is characterized by: The soil bin pressure calculation method in step (7) is: 1) Soil pressure of the stratum, the horizontal lateral force of the stratum is: σ horizontal lateral force = k × γ × h where: h = 0.45 × 2 S-1 ω; S--surrounding rock grade, such as Grade IV surrounding rock, then S = 4; h--surrounding rock pressure calculation height; γ--surrounding rock weight; ω--width influence coefficient, and ω = 1 + i (B-5); B--tunnel net width, in meters; i--based on B = 5m, when B < 5m, take i = 0.2, when B > 5m, take i = 0.1; k--horizontal side pressure coefficient determined according to the surrounding rock grade; 2) Groundwater pressure, σw before the cutterhead = qγh, where: q is an empirical value determined based on the permeability coefficient of the soil layer, q = 0.5 to 1.0 for sandy soil, q = 0.1 to 0.5 for clay soil, and q = 0 to 0.5 for weathered rock layer; γ is the bulk density of water; h is the height of the groundwater level from the top of the cutterhead; 3) Preparation pressure. Due to many unforeseen factors in construction, the construction soil pressure is less than the static soil pressure in the original soil. According to construction experience, when calculating the soil pressure in areas with strict settlement requirements, a pressure of 0.01 to 0.02 MPa is usually considered as the preparation pressure on the basis of theoretical calculation. 4) According to the tunnel burial depth, the upper soil bin pressure is set as: P = stratum soil pressure + groundwater pressure + reserve pressure.

7. The shield lateral shifting start and arc guide tunnel slag removal construction method under narrow urban site conditions according to claim 1 is characterized by: In step (7), the excavation volume is controlled. During the excavation process, the excavation is carried out strictly in accordance with the soil bin pressure specified in the technical briefing, and the excavation and excavation speeds are controlled to avoid soil pressure fluctuations. The shield driver records the difference in cylinder stroke before and after each bucket of soil during the excavation process, and judges whether there is over-excavation based on this. The shield driver judges whether there is over-excavation by communicating with the earthworker and observing the soil condition in the soil bin during the excavation process. During the excavation construction, ground monitoring is strengthened, and it is judged whether the setting of the soil bin pressure and the excavation volume meet the requirements based on the monitoring data. The engineer inspects each bucket of soil and takes soil samples, and analyzes and judges based on the soil condition. If there is any abnormality, reasonable measures are taken in time to ensure the control of the excavation volume.

8. The shield lateral shifting start and arc-shaped guide tunnel slag removal construction method under narrow urban site conditions according to claim 1 is characterized by: The soil improvement of the initial excavation section in step (7) includes: 1) Grease at the tail of the shield: In order to prevent groundwater and synchronous grouting slurry from entering the tunnel from the tail of the shield when the shield is advancing, grease is injected at the wire brush position of the tail of the shield to achieve the sealing function of the shield; in order to safely and smoothly complete the excavation task of the interval tunnel, the pressure injection of grease at the tail of the shield must be done well; grease should be injected frequently during construction, and the grease at the tail of the shield should follow the principle of small amounts and multiple times; 2) Foaming agent: When the shield machine cutterhead enters the reinforcement area, the cutterhead torque increases, and foam or water needs to be injected into the front of the excavation chamber to improve the soil; in addition, when the soil layer is hard, it will affect the normal operation of the earth pressure sensor in the soil chamber, which will bring a series of problems such as excessive surface heave and subsidence. At this time, foam or water needs to be added while advancing so that the earth pressure sensor can normally respond to the earth pressure of the excavation surface; the proportion of foaming agent used is generally the composition of the foam solution: 3% foam additive, 97% water; Ⅰ. Foam composition: 90-95% compressed air and 5-10% foam solution; Ⅱ. The amount of foam injected is calculated according to the excavation volume: 300L / m 3 .

9. The shield lateral shift start and arc guide tunnel slag removal construction method under narrow urban site conditions according to claim 1, characterized in that: The shield machine attitude control at the beginning of excavation in step (7) includes: ensuring that the shield machine is constructed at a balanced and uniform speed while ensuring that the front settlement of the shield machine is well controlled, and the shield machine attitude changes should not be too large or too frequent; checking the advance amount of the pipe segment every 5 rings, not correcting it hastily or violently during advancement, paying more attention to measuring the shield tail gap, and the change in the relative area oil pressure gradually changes with the slag discharge amount and the jack stroke to reduce the impact of the shield construction on the ground.

Images