Method for installing a shield foundation

Abstract

The application discloses a shield hoisting foundation construction method, which can reliably construct a hoisting foundation perpendicular to the axis of a starting shaft, and realizes hoisting and lowering of each shield block into the shaft by means of a gantry crane stably running on the hoisting foundation, thereby solving the technical problem that each shield block cannot be hoisted and lowered into the shaft by a crawler crane in a restricted environment such as an airport. The hoisting foundation is arranged perpendicularly to the axis of the shield starting shaft, so that the gantry crane can be safely, stably and reliably arranged perpendicularly to the shield starting shaft and above the starting shaft with a relatively loose height limit, thereby solving the height limit problem in the restricted construction environment such as an airport, and further enabling shield block hoisting and lowering into the shaft by the gantry crane meeting the height limit requirement.

Description

Technical Field

[0001] This invention application relates to the field of shield tunneling technology, specifically to a method for constructing a shield tunneling foundation. Background Technology

[0002] Currently, with the rapid development of cities in China, construction traffic pressure is gradually increasing, and public transportation based on traditional roads is no longer sufficient to meet the daily commuting needs of citizens. Along with the needs of modern urban construction, rail transit is gradually becoming a direction for urban planning, development, and construction. To promote regional economic development and improve the overall efficiency and service level of transportation, the construction of transportation hubs is crucial. These hubs integrate aviation, high-speed rail, intercity rail, and urban rail transit, achieving interconnectivity of transportation infrastructure through the construction of a multi-level, integrated transportation system.

[0003] Due to the large scale of integrated transportation hub planning, the variety of transportation modes, and the complex surrounding construction environment, the construction sites for rail transit projects face numerous limitations. Taking a reserved rail transit project at an airport's T3 transportation hub as an example, the tunnel boring machine (TBM) is used for excavation. Because the TBM has a large diameter and considerable weight, its launch requires disassembling and hoisting each section into the shaft. However, since the construction site is located within the existing airport area, there are stepped height restrictions above the TBM launch shaft, ranging from 15m to 32m from the main launch shaft, standard section, to the auxiliary launch shaft. This height restriction prevents even highly adaptable crawler cranes from accessing the site for hoisting, making it difficult to lower the TBM into the shaft. Similar TBM construction scenarios are becoming increasingly common in existing cities.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the background technology of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] In view of at least one of the above technical problems, this disclosure provides a method for constructing a shield tunneling machine (TBM) hoisting foundation. This method reliably constructs a hoisting foundation perpendicular to the axis of the launching shaft, and relies on a gantry crane that runs smoothly on the hoisting foundation to hoist and lower each section of the TBM into the shaft. This solves the technical problem that it is impossible to hoist and lower each section of the TBM into the shaft using a crawler crane in a site-constrained environment.

[0006] According to one aspect of this disclosure, a method for constructing a shield tunneling foundation is provided, comprising the following steps:

[0007] (1) On both sides of the starting wellhead that meets the height restriction requirements, the pile hole layout points that match the track spacing of the gantry crane to be installed are determined by total station, and the line connecting the pile holes on both sides is perpendicular to the axis of the starting well.

[0008] (2) After the casing is vertically installed at each of the pile hole locations, the drilling rig enters the site and is positioned, mud is prepared and the center line of the drilling rod of the drilling rig is adjusted to coincide with the center line of the casing, and the pile hole drilling operation is carried out.

[0009] (3) Fabricate a steel cage that matches the pile hole. The steel cage includes a main bar arranged in a circular array, a reinforcing stirrup perpendicular to the main bar and sleeved on the main bar, and a spiral stirrup corresponding to the main bar. A number of protective layer pads arranged in a circumferential quincunx pattern are also arranged along the axial direction of the steel cage.

[0010] (4) When a crane that meets the height limit requirements enters the site, after the pile hole is cleaned, the coaxially segmented steel cage is hoisted into the pile hole. When the top of each segment is lowered to the top of the casing, a spreader bar is inserted into the steel cage to hang the steel cage on the top of the casing. Then the next section of steel cage is hoisted. After welding the main bars of the two sections of steel cage, the spreader bar support is removed. This step is repeated until the steel cage is completely inserted into the pile.

[0011] (5) Install a guide pipe in the pile hole, clean the hole and carry out continuous concrete pouring operation until the pile hole is filled with concrete slurry and the cast-in-place pile is formed.

[0012] (6) Measure and lay out the centerline and foundation boundary of the gantry crane track to be installed. The gantry crane track is set on both sides of the well opening with a relatively loose height limit, perpendicular to the centerline of the starting well, and coincides with the line connecting the corresponding pile holes. According to the layout, excavate the gantry crane beam trench with a certain depth and width outside the well. After excavating to the design elevation, level and compact the bottom of the trench.

[0013] (7) Tie steel bars in the groove of the external portal crane beam and arrange several portal crane track embedded parts along the axial direction of the external portal crane beam groove. After verifying the position of the portal crane track embedded parts, construct and pour the external portal crane beam.

[0014] (8) Backfill clay in a trapezoidal shape above the top slab of the standard section of the launching shaft and between the retaining walls on the corresponding side of the launching shaft where the height limit is relatively loose, up to the bottom height of the gate beam outside the shaft;

[0015] (9) Triangular cross-section trenches are excavated on both sides of the gantry crane track along the backfill clay at the corresponding underground continuous wall of the starting shaft, and triangular reinforced concrete brackets are set in the trenches.

[0016] (10) Construct a well-side gantry crane beam that coincides with the centerline of the gantry crane track, cut the underground continuous walls on both sides of the starting well to expose the vertical main reinforcement of the underground continuous walls, tie the well-side gantry crane beam reinforcement between the vertical main reinforcement of the underground continuous walls on both sides, and then construct the formwork and pour the concrete, wherein the well-side gantry crane beam reinforcement intersects with the external gantry crane beam reinforcement.

[0017] (11) A groove is opened at the top of the underground continuous wall ring frame beam on the other side of the starting shaft where the height limit is relatively loose, which coincides with the center line of the gantry crane track. At the bottom of the groove, a number of gantry crane track embedded parts with the same elevation as the gantry crane track embedded parts at the outside of the shaft are arranged in an array with rebar.

[0018] (12) At a certain distance from the starting well opening, construct several foundation hidden beams perpendicular to the gantry crane track and anchored to the gantry crane beams on one side of the starting well, and apply force to the supporting shield block raft foundation at the foundation hidden beams.

[0019] In some embodiments of this disclosure, in step (2), the casing is 30-40cm above the ground, and at least one overflow port is provided at the corresponding position of the top edge of the casing.

[0020] In some embodiments of this disclosure, in step (3), the beginning and end portions of the spiral stirrups each include a horizontal segment perpendicular to the main reinforcement of the steel cage, and the length of the horizontal segment is not less than one and a half turns.

[0021] In some embodiments of this disclosure, in step (5), a trial assembly and water tightness test are performed before the guide pipe is installed into the pile, and after the guide pipe is installed into the pile, its bottom is 30-50cm away from the bottom of the pile hole; when pouring concrete, the depth of the guide pipe embedded in the concrete is not less than 2m.

[0022] In some embodiments of this disclosure, in step (7), the gantry rail embedded part includes a fixing screw rod symmetrically arranged on both sides of the gantry beam groove outside the well, and a horizontal plate sleeved between the two screw rods; the horizontal plate is arranged at a height lower than the ground elevation.

[0023] In some embodiments of this disclosure, in step (7), after the external gate beam is poured, a trapezoidal concrete anti-collision block is poured at the corresponding end of the external gate beam.

[0024] In some embodiments of this disclosure, in step (7), the pile hole is pre-treated before the well gate lifting beam is poured. After the pile hole is broken down to the top elevation position by a pneumatic pick, the top reinforcement of the pile is straightened and pre-bent, and the pre-bending angle is not greater than 15°.

[0025] In some embodiments of this disclosure, in step (8), the clay is backfilled and compacted in layers, and the layer thickness is no more than 500 mm; the slope of the trapezoidal backfill is 1:1.5.

[0026] In some embodiments of this disclosure, in step (9), the angle between the reinforced concrete corbel and the corresponding diaphragm wall is 45°, and the reinforcing bars are drilled and anchored into the corresponding diaphragm wall.

[0027] In some embodiments of this disclosure, in step (12), a cast-in-place pile is provided at the intersection of the foundation hidden beam and the external gate lifting beam.

[0028] One or more technical solutions provided in the embodiments of this application have at least one of the following technical effects or advantages:

[0029] 1. By using the hoisting foundation that is arranged perpendicular to the axis of the shield tunneling starting shaft, the gantry crane can be safely, stably and reliably installed perpendicular to the shield tunneling starting shaft, and is located above the starting shaft where the height restriction is relatively relaxed. This solves the height restriction problem in the restricted construction environment, and allows the shield body to be hoisted and lowered into the shaft in sections by using a gantry crane that meets the height restriction requirements.

[0030] 2. The cast-in-place piles and reinforced concrete structures on both sides of the launching shaft can effectively provide stable support for the gantry crane rails. The embedded parts of the gantry crane rails in the reinforced concrete structure can achieve force transmission between the gantry crane rails and the cast-in-place pile concrete foundation, ensuring the stability of the gantry crane during lifting and operation.

[0031] 3. Utilizing the existing ring beam at the top of the diaphragm wall at the launch shaft opening, where the height limit is relatively loose, as the gantry crane foundation strengthens the connection between the gantry crane foundation and the launch shaft structure. On the other hand, it reduces the amount of gantry crane foundation construction, saving materials and construction time.

[0032] 4. The foundation beams and reinforced concrete raft foundation on one side of the launching shaft can serve as the welding and lifting area for the extremely heavy cutterhead, effectively preventing stress and settlement in this area. Furthermore, since this area is a certain distance from the launching shaft, the structure at the launching shaft is protected from the influence of the cutterhead's gravity.

[0033] 5. The foundation of the hidden beam and the foundation of the external door lifting beam are mutually anchored, and bored piles are provided at the intersection of the two. This allows the raft foundation to effectively and reliably bear the load when the cutterhead is assembled and rotated down into the well. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the height restriction area above the launching well in one embodiment of this application.

[0035] Figure 2 This is a schematic diagram of the structure of the hoisting foundation in one embodiment of this application.

[0036] Figure 3 This is a schematic diagram of the spiral stirrups of a steel cage in one embodiment of this application.

[0037] Figure 4 This is a schematic diagram of the structure of the protective layer pad block in one embodiment of this application.

[0038] Figure 5 This is a schematic cross-sectional view of the manhole door lifting beam in one embodiment of this application.

[0039] Figure 6 This is a schematic diagram of clay backfilling in one embodiment of this application.

[0040] Figure 7 This is a schematic diagram of the arrangement structure of the triangular corbels in one embodiment of this application.

[0041] In the above figures, 11 is the main launching shaft, 12 is the standard section, 13 is the auxiliary launching shaft, 21 is the cast-in-place pile, 22 is the external portal beam, 23 is the side portal beam, 24 is the diaphragm wall ring frame beam, 25 is the foundation hidden beam, 26 is the raft foundation, 3 is the spiral stirrup, 31 is the horizontal section of the spiral stirrup, 4 is the main reinforcement of the steel cage, 41 is the protective layer pad, 5 is the excavation edge line of the external portal beam, 51 is the fixing screw, 52 is the horizontal plate, 53 is the portal crane track, 61 is the top plate of the standard section of the launching shaft, 62 is the retaining wall, 63 is the ring crown beam, 64 is the trapezoidal backfill clay, 65 is the side portal beam, 7 is the launching shaft, 71 is the triangular corbel, 72 is the diaphragm wall, and 73 is the diaphragm wall pile head. Detailed Implementation

[0042] To better understand the technical solution of this application, the above technical solution will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] The Baiyun Airport T3 Transportation Hub Rail Transit Reserved Project incorporates the Guangzhou-Zhuhai (Macau) High-Speed ​​Railway, the Guanghe High-Speed ​​Railway, and the Fangcun-Baiyun Airport Intercity Railway. This includes the main station structure and reserved civil engineering works for the sections at both ends of the station within the airport's boundary. This reserved civil engineering project is a fully underground structure. Except for the open-cut section connecting to the station's open-cut foundation pit, the rest will be constructed using the shield tunneling method. The shield tunneling site is adjacent to Baiyun Airport, with a complex surrounding environment. Furthermore, the construction area is adjacent to the airport's East Second Runway, and the installation site has a 16m-30m stepped height restriction. (See [link / reference]). Figure 1 This resulted in ordinary crawler cranes being unable to enter the site for hoisting due to height restrictions, making it difficult to lower the tunnel boring machine into the shaft in sections.

[0044] Therefore, this example discloses a method for constructing a shield tunneling machine (TBM) hoisting foundation. This method involves constructing gantry crane hoisting foundations perpendicular to the axis of the launching shaft on both sides of the secondary launching shaft, which is located in the opposite direction of the height restriction. This allows for the installation of gantry cranes that meet the height restriction requirements for the segmented hoisting and lowering of the TBM into the shaft. Specifically, the method includes the following steps:

[0045] (1) On both sides of the starting wellhead that meets the height limit requirements, the pile hole layout points that match the track spacing of the gantry crane to be installed are determined by total station, and the line connecting the pile holes on both sides is perpendicular to the axis of the starting well.

[0046] In this embodiment, see Figure 1 Because the height restriction above the main launching shaft is quite severe, the secondary launching shaft, which has a more lenient height restriction, was chosen as the shaft for the segmented hoisting of the tunnel boring machine. Considering that the main launching shaft has a stepped height restriction, in order to avoid the height restriction affecting the operation of the hoisting equipment, a gantry crane perpendicular to the axis of the main launching shaft was set up for hoisting in this case. Due to site limitations, the gantry crane intersects with the secondary launching shaft. To ensure the structural safety of the main launching shaft and the smooth and safe operation of the gantry crane, a gantry crane foundation was constructed to bear the load of the gantry crane and the segmented tunnel boring machine, thus ensuring construction safety.

[0047] Considering the weight of the gantry crane itself, coupled with the lifting components, the gantry crane track foundation bears a significant load. To prevent settlement and other issues affecting the normal operation of the gantry crane, in this embodiment, cast-in-place piles, perpendicular to the axis of the launching shaft and matching the spacing of the gantry crane tracks to be installed, are installed on both sides of the auxiliary launching shaft. These piles transfer the force on the gantry crane foundation to the ground for dispersion. See details below. Figure 2 A total station was used to determine the locations of each pile hole, and rebar ends were inserted for marking, ensuring that the line connecting the rebar ends on the same side coincided with the centerline of the track for the gantry crane to be installed. Additionally, see [link to other documentation]. Figure 2 Since the gantry crane needs to be hoisted above the secondary launching shaft, the gantry crane track needs to be extended to both sides of the secondary launching shaft so that the secondary launching shaft is within the lifting range of the gantry crane. In this embodiment, because the construction area on one side perpendicular to the axis of the secondary launching shaft is restricted, the storage area for the cutterhead and shield body is located on the other side of the secondary launching shaft perpendicular to its axis. Therefore, the length of the gantry crane foundation on one side is much greater than that on the other side. Furthermore, due to the stepped height restriction above the launching shaft, and the fact that the gantry crane is arranged perpendicular to the axis of the launching shaft, to avoid the gantry crane being restricted by the airport height restriction on one side when the span is too large, the span of the gantry crane is set to be consistent with the corresponding width of the secondary launching shaft. This results in the gantry crane track foundation intersecting with the structure of the secondary launching shaft. Therefore, the gantry crane track foundation is reinforced using the structure of the secondary launching shaft, and cast-in-place piles are only installed on both sides of the secondary launching shaft perpendicular to its axis.

[0048] (2) After the casing is vertically installed at each pile hole location, the drilling rig enters the site and is positioned. Mud is prepared and the center line of the drilling rig rod is adjusted to coincide with the center line of the casing before the pile hole drilling operation is carried out.

[0049] Before drilling the cast-in-place pile, a casing is installed to ensure the drilling rig can operate smoothly vertically along the pile location, while also protecting the borehole opening and increasing the mud head within the pile hole. In this embodiment, a steel casing with an inner diameter 100mm larger than the drill bit diameter is used, made of a 6m long and 10mm thick steel plate. During installation, the deviation between the center of the steel casing and the center of the pile location must be less than 20mm, and the top of the casing should be 30-40cm above the ground to maintain a higher water level inside the hole than the water level outside the hole or the ground level. Furthermore, in this embodiment, an overflow port is provided at the top edge of the casing to facilitate mud overflow and return to the mud pool for recycling. In other embodiments, a different number of overflow ports are provided. After installation, the casing is checked to ensure that the horizontal error at the top of the casing does not exceed 6mm. The top of the casing is reinforced with steel plates or angle steel and a lifting ring is installed. The gap between the casing and the pit wall is compacted in layers with clay to prevent leakage.

[0050] After the steel casing is installed, the drilling rig is brought in. In this example, a rotary drilling rig is used to excavate the pile hole. After the rotary drilling rig is moved near the pile position, its stability is calibrated to prevent it from tilting due to sinking. The pile driver positioning must be accurate, horizontal, vertical, and stable, ensuring that the center lines of the drill guide rod, rotary table, and casing are aligned. After the rotary drilling rig is in place, its verticality is adjusted using the automatic control system and manually checked. When placing the drilling rig, ensure that the base is flat, the tower is vertical, and the center of the rotary table (drill bit) is aligned with the center of the casing's crosshairs.

[0051] In addition, drilling mud required for the cast-in-place pile borehole needs to be prepared. In this example, a mud pit (including a sedimentation tank for mud return and a mud storage tank) is set up on site. The volume of the mud pit is 1.5 times the volume of the borehole to ensure a stable mud supply and avoid mud interruption. A spoil area is set up next to the sedimentation tank to ensure sufficient space for mud circulation and storage. Furthermore, to ensure the performance indicators of the mud during drilling, the mud specific gravity, viscosity, and sand content must be controlled during construction to ensure that the mud specific gravity in the borehole is controlled within the range of 1.0–1.05 and the viscosity within the range of 25s–30s. Gravity sedimentation is used for mud spoil removal, which utilizes the relative density difference between the mud and the soil spoil to cause the soil spoil to settle and be removed. After injecting the corresponding mud, drilling begins.

[0052] To ensure borehole stability, the drilling mud level must be maintained during drilling. As mud is consumed and the borehole depth increases, mud should be replenished promptly to maintain pressure balance within the borehole. When encountering soft layers, especially cohesive soil, use a longer bucket with a wider tooth spacing to prevent mud clogging. After retrieving the drill bit, promptly check the integrity of the bottom cutting teeth, clean the mud between the teeth, and replace any dulled teeth. If encountering hard soil, first use a smaller diameter bucket to drill a pilot hole, then use a bucket of appropriate diameter to drill an enlarged hole. If encountering moderately weathered rock, switch to a roller cone drill bit for drilling operations.

[0053] After the drilling rig is in place, check the level and alignment of the drilling platform to ensure that the alignment error is ≤10mm and the verticality of the square rod is ≤1 / 300. When drilling, apply light pressure and rotate slowly, gradually increasing the rotation speed after drilling to about 4m. In addition, when adding drill rods, first lift the drill bit slightly off the bottom of the hole, and wait for the mud to circulate for 2-3 minutes before unscrewing the added drill rods.

[0054] (3) Make a steel cage that matches the pile hole. The steel cage includes each main bar arranged in a circular array, a reinforcing stirrup perpendicular to each main bar and sleeved on the outside of each main bar, and a spiral stirrup corresponding to the main bar; and a number of protective layer pads arranged in a circumferential quincunx pattern along the axis of the steel cage.

[0055] To enhance the structural strength of the cast-in-place pile, a corresponding reinforcing cage needs to be placed inside the pile. In this embodiment, the reinforcing cage includes 18 circumferentially arranged Φ18 threaded steel bars, with reinforcing stirrups of Φ10@200mm arranged outside each main reinforcement bar. To further ensure the strength of the reinforcing cage, see [reference needed]. Figure 3 A Ф10@200mm spiral stirrup 3 is wrapped around the cage formed by the main reinforcement bars, and a horizontal section 31 is provided at the beginning and end of the spiral stirrup, with a length of not less than one and a half turns. Furthermore, considering the height restriction requirements above the auxiliary launching shaft, and the fact that the steel cage adapted to the cast-in-place pile has a certain length and cannot be directly driven into the pile, the steel cage is manufactured in sections, with spiral stirrups pre-installed during the manufacturing process, and the main reinforcement bars are welded together. In addition, a steel lifting ring is installed at the top of the steel cage, with φ20 round steel bars for the lifting ring, and a ring-shaped reinforcing stirrup welded at the bottom to reduce damage to the trench wall from the steel bar ends.

[0056] In addition, to ensure the protective thickness of the reinforcing cage, in this embodiment, four protective layer spacers are evenly arranged circumferentially every 4m around the reinforcing cage (in a quincunx pattern), see [link to relevant documentation]. Figure 4 During the hoisting and lowering of the reinforcing cage, each protective layer pad has a certain width, which ensures that the distance between the reinforcing cage and the pile hole wall is at least the width of the protective layer pad, thereby ensuring the thickness of the protective layer of the main reinforcement and ensuring that the reinforcing cage is successfully lowered into place.

[0057] (4) When a crane that meets the height limit requirements enters the site, after the pile hole is cleaned, the sectional steel cage is hoisted into the pile hole in a coaxial manner. When the top of each section is lowered to the top of the casing, a spreader bar is inserted into the steel cage to hang the steel cage on the top of the casing. Then the next section of steel cage is hoisted. After welding the main bars of the two sections of steel cage, the spreader bar support is removed. This step is repeated until the steel cage is completely inserted into the pile.

[0058] After the borehole reaches the design elevation, check that the depth of the pile hole is not less than the design value and that the mud parameters are: relative density 1.10–1.25, viscosity 18–28s, sand content ≤8%, and verticality not greater than 1 / 300. The thickness of the sediment at the bottom of the hole is measured and compared using a plumb bob. The difference between the actual hole depth after drilling and the hole depth before concrete pouring is the sediment thickness, ensuring that the sediment thickness is not greater than 5cm.

[0059] After the reinforcing cage is welded, it is hoisted. Due to height restrictions at the airport, the cage is installed in sections. In this case, before hoisting, lifting bars are welded to the main reinforcement bars of each section. These lifting bars are made of two Q235BΦ20 steel bars, welded to the main reinforcement bars on one side, with a weld length of not less than 10d. Furthermore, a 25t truck crane is used for hoisting, and the highest point of the crane boom meets the height restrictions.

[0060] Before lifting, install wire ropes and shackles on the reinforcing cage, and attach the main and auxiliary hooks of the 25t truck crane. After ensuring the wire rope connection is reliable, raise the main and auxiliary hooks simultaneously to lift the reinforcing cage horizontally. Once the reinforcing cage is 0.3m to 0.5m above the ground, confirm its stability, and then slowly lift the main hook. The auxiliary hook assists in lifting the cage based on the distance from the rear of the reinforcing cage to the ground. During this process, avoid touching the ground with the rear of the reinforcing cage, which could cause deformation and affect the pile driving effect. After the reinforcing cage is lifted, the main hook of the crane slowly lifts it, with the auxiliary hook assisting, maintaining the distance from the ground until the reinforcing cage is perpendicular to the ground. Then, align the center of the reinforcing cage with the center of the pile hole and lower the cage. When the cage has fallen to the point where the auxiliary hook is at the top of the steel casing, pause the lowering operation and remove the wire rope and shackles from the auxiliary hook's lifting point. Then, the main hook is lowered to allow the reinforcing cage to continue inserting downwards. When the main hook lifting point is at the top of the steel casing, the lowering is paused again, and a spreader beam is inserted perpendicularly to the reinforcing cage, with both ends resting on the top of the steel casing. This secures the reinforcing cage to the top of the casing. Then, the wire rope and shackles at the main hook lifting point are removed. The same process is then repeated for the next section of the reinforcing cage. Once the main reinforcement bars of the two sections of the reinforcing cage are securely welded together and have reached the required strength, the spreader beam support is removed, and the reinforcing cage is lowered again. This process continues until the reinforcing cage is completely inserted into the pile.

[0061] (5) Install a guide pipe in the pile hole, clean the hole and carry out continuous concrete pouring until the pile hole is filled with concrete slurry and the cast-in-place pile is formed.

[0062] In this example, the conduit is assembled using standard sections with a diameter of 250mm and adjusting sections. The standard section length is 2.5m, and the adjusting section lengths are 0.5m, 1m, and 1.5m. Before installation, the conduit length is calculated based on the hole depth. Furthermore, before the first installation, a trial assembly and watertightness test are required. The conduits are numbered and marked in ascending order, and the conduit body is checked for deformation, cracks, or other problems. During the watertightness test, one end of the water injection hole is sealed, and the other end is connected to an air compressor. The sealing at the conduit connection is checked. After passing the inspection, the air compressor is pressurized to 0.6MPa and maintained for 15 minutes. Overflow at the conduit joints is checked and recorded. For the pressure test, the conduit is rotated 180°, pressurized again, and maintained for 15 minutes. The results are recorded.

[0063] After confirming the quality and reliability of the guide pipe, install the guide pipe in the pile hole, ensuring that the bottom of the guide pipe is 30-50cm away from the bottom of the hole. When installing each section of the guide pipe, check whether the waterproof rubber ring at the connection thread is damaged or detached, and replace the damaged parts in time to ensure the stability of the guide pipe during grouting.

[0064] After the guide pipe is installed, a second cleaning of the hole is carried out. Before pouring concrete, ensure that the mud slurry within 500mm of the bottom of the hole has a specific gravity of less than 1.25 and greater than 1.10, a sand content of less than 8%, a viscosity of less than 28s and greater than 20s, and that the thickness of the sediment at the bottom of the hole is not greater than 5cm.

[0065] Within 0.5 hours of cleaning the borehole to the required conditions, C35 underwater concrete should be used for pile foundation pouring, with a slump of 180–220 mm. When pouring the first batch of concrete, the distance from the bottom of the tremie pipe to the bottom of the borehole should be controlled at 30–50 cm. Furthermore, the underwater concrete pouring in the pile hole must be continuous without interruption to avoid affecting the pile quality. During the concrete pouring process, the height of the concrete surface should be measured continuously to accurately control the depth of the tremie pipe embedded in the concrete; the minimum embedment depth should not be less than 2 m to ensure dense grouting and guarantee the quality of the concrete pouring. After the concrete pouring is completed, the tremie pipe should be removed only after the concrete has initially set.

[0066] (6) Measure and lay out the centerline and foundation boundary of the gantry crane track to be installed. The gantry crane track is set on both sides of the well opening where the height limit is relatively loose, perpendicular to the centerline of the starting well, and coincides with the line connecting the corresponding pile holes. According to the layout, excavate the gantry crane beam trench with a certain depth and width outside the well. After excavating to the design elevation, level and compact the bottom of the trench.

[0067] After the cast-in-place piles distributed on both sides of the launching shaft, perpendicular to the direction of the launching shaft, are completed, the external gantry crane beam at that location is poured. First, the centerline of the gantry crane track, i.e., the foundation boundary, is laid out, and the foundation edge line is marked with ink. Then, according to the laid-out lines and ink markings, a cutting machine is used to cut the joints, and then an excavator is used to break up the road surface. See [link to relevant documentation]. Figure 5 The foundation for the external gate lifting beam was excavated. After excavating to the design elevation, the bottom of the trench was leveled and compacted.

[0068] (7) Tie steel bars in the groove of the gantry crane beam outside the well and arrange several gantry crane track embedded parts along the axial direction of the gantry crane beam outside the well. After verifying the position of the gantry crane track embedded parts, construct and pour the gantry crane beam outside the well.

[0069] After the reinforcing steel bars in the external gantry crane beam channel are tied, to facilitate the subsequent installation of the gantry crane track, embedded parts for the gantry crane track are fixedly installed between the external gantry crane beam and its reinforcing steel bars before the external gantry crane beam is poured. See details below. Figure 5 The gantry crane track embedded component includes symmetrically arranged fixed screw rods 51 and horizontal plates 52 sleeved on the screw rods. The gantry crane track embedded component is arranged in an axial array along the gantry crane track in the gantry beam groove outside the well. The horizontal plates 53 are sleeved on the two fixed screw rods 51 through through holes symmetrically opened on both sides, and the distance between the two screw rods is consistent with the distance between the fixing holes of the gantry crane track. The fixed screw rods and the horizontal plates are welded firmly by through-hole plug welding, thereby realizing a reliable connection between the two. In addition, by being embedded in the gantry crane beam outside the well, the reliable installation of the gantry crane track is realized.

[0070] In this embodiment, see Figure 5 The ground elevation is 13.2m, the top elevation of the external portal beam is 13.05m, and the top elevation of the rails is 13.22m. Before pouring the external portal beam, the bored piles were pre-treated to ensure a reliable connection and load transfer between the piles and the external portal beam. Specifically, after manually breaking the piles to the top elevation using a hand-held pneumatic hammer, the top reinforcement bars were straightened and pre-bent. The pre-bending angle was no more than 15° with the vertical reinforcement bars. Furthermore, when tying the reinforcement bars for the external portal beam, it was ensured that the reinforcement bars passed through the top reinforcement bars of the bored piles along their entire length. Thus, a stable connection was achieved between the two through the top reinforcement bars of the bored piles inserted within the reinforcement bars of the external portal beam. In addition, the external portal beam was cast using C30 concrete.

[0071] After the gantry crane beam is installed, anti-collision measures are installed at the ends of the steel rails after the gantry crane track is designed and installed. The anti-collision measures are trapezoidal reinforced concrete anti-collision blocks with a top width of 500mm, a bottom width of 1000mm, a height of 1000mm, and a thickness of 500mm.

[0072] (8) Backfill clay in a trapezoidal shape above the top slab of the standard section of the launching shaft and between the retaining walls on the corresponding side of the launching shaft where the height limit is relatively loose, up to the bottom height of the gate beam outside the shaft.

[0073] Since the gantry crane tracks are arranged perpendicular to the axis of the launching shaft on both sides of the auxiliary launching shaft, and to further avoid height restrictions, the span of the gantry crane is chosen to be consistent with the width of the auxiliary launching shaft opening. This results in an intersection between the gantry crane tracks and the auxiliary launching shaft. In order to save construction time and costs, and to ensure the structural strength of the gantry crane track foundation, the gantry crane foundation is combined with the launching shaft structure to share the load and increase the load-bearing strength of the gantry crane foundation.

[0074] See details Figure 2 Since the gantry crane track passes through the underground continuous wall at the auxiliary launching shaft and the standard section of the launching shaft, and since the gantry crane track cannot be perfectly matched with the width of the auxiliary launching shaft, the gantry crane beam 23 on the shaft side is constructed at this location after the construction of the top slab of the standard section and the underground retaining wall at the auxiliary launching shaft is completed.

[0075] In this embodiment, since the gantry crane beam spans the launching shaft and is close to the ring frame beam at the auxiliary launching shaft, while having a certain distance below it from the top slab of the standard section, to ensure reliable stress support when the gantry crane lifts and runs to the area where the gantry crane beam is located, and to facilitate the pouring and support of the gantry crane beam, in this embodiment, clay is backfilled between the top slab of the standard section structure of the launching shaft and the retaining wall of the auxiliary launching shaft up to the bottom of the gantry crane beam at its designed position to provide reliable stress support. For details, see [link to details]. Figure 6 Clay was backfilled in layers between the top slab 61 and the retaining wall 62 of the standard section. The backfilled clay was trapezoidal in shape, with a top width of 6.5m, a bottom width of 18.35m, and a height of 7.9m. The slope was 1:1.5. The clay was backfilled and compacted in layers, with each layer not exceeding 500mm in thickness. A rammer and a PC60 mini excavator were used for compaction.

[0076] (9) Triangular cross-section trenches are excavated on both sides of the gantry crane track along the backfill clay at the corresponding underground continuous wall of the starting shaft, and triangular reinforced concrete brackets are set in the trenches.

[0077] Because the load-bearing strength of the trapezoidal backfill clay is limited, in order to further increase the load-bearing strength of the well-side gantry crane beam and strengthen the structural connection between the gantry crane foundation and the launching shaft, in this embodiment, a triangular area parallel to the axis of the launching shaft is excavated at the backfill clay location below the intersection of the well-side gantry crane beam and the launching shaft. See details below. Figure 7 The excavated slopes on both sides are compacted, and the outer skin of the diaphragm walls on both sides is roughened. Reinforcing bars are tied and installed in the triangular trench and then embedded into the corresponding diaphragm wall. Clay backfill slope and diaphragm wall are used as corbel templates, and concrete is poured to form a reinforced concrete corbel. The corbel and the manhole side door lifting beam are supported by the force to ensure the reliable force of the manhole side door lifting beam.

[0078] (10) Construct a well-side gantry crane beam that coincides with the centerline of the gantry crane track. Cut the underground continuous walls on both sides of the starting well to expose the vertical main reinforcement of the underground continuous walls. Tie the reinforcement of the well-side gantry crane beam between the vertical main reinforcement of the underground continuous walls on both sides and then construct the formwork and pour the concrete. The reinforcement of the well-side gantry crane beam intersects with the reinforcement of the external gantry crane beam.

[0079] To achieve the connection between the side portal crane beam and the external portal crane beam and ensure shared load-bearing, in this embodiment, the side portal crane beam and the external portal crane beam are connected at the underground continuous walls on both sides of the launching shaft. Furthermore, to further connect the portal crane foundation with the launching shaft structure and improve structural strength, see [reference needed]. Figure 7 Therefore, the concrete of the diaphragm wall pile heads 73 on both sides was first cut using a cutting machine and broken with a hand-held pneumatic hammer to expose the vertical main reinforcement of the diaphragm wall. After cleaning up the concrete debris, the reinforcement of the well-side portal beam was then tied. To ensure the structural strength of the well-side portal beam, its reinforcement was anchored to the reinforcement of the external portal beam on both sides of the diaphragm wall pile head, and the diaphragm wall pile head reinforcement was passed through the anchorage, thus achieving the connection between the well-side portal beam, the external portal beam, and the diaphragm wall of the starting shaft. After the reinforcement of the well-side portal beam was tied, the formwork was poured.

[0080] (11) A groove is opened at the top of the underground continuous wall ring beam on the other side of the starting shaft where the height limit is relatively loose, which coincides with the center line of the gantry crane track. At the bottom of the groove, a number of gantry crane track embedded parts with the same elevation as the gantry crane track embedded parts at the outside of the shaft are arranged in an array with rebar.

[0081] The other side of the gantry crane track passes directly above the underground continuous wall ring beam on the other side of the auxiliary launching shaft. Therefore, in order to save time and construction costs, see... Figure 2 The underground continuous wall ring frame beam 24 was directly used as the foundation for the gantry crane. To ensure a smooth connection between the gantry crane track at the underground continuous wall ring frame beam and the track at the external gantry crane beam, a cutting machine was used to cut the grooves, and a handheld pneumatic hammer was used to break them up. A groove 500mm wide and 150mm high was opened on each side of the center line of the gantry crane track on the top of the underground continuous wall ring frame beam, corresponding to the center line of the gantry crane track. The ring frame beam and the underground continuous wall reinforcement within the groove area were cut off. Then, along the gantry crane track layout direction, holes were drilled at 0.6m intervals in the grooves to install the gantry crane track embedded parts. The diameter of the holes was not less than 30mm and the depth was 45cm. After drilling to the design depth, high-pressure air was used to blow away the dust in the air, and then the anchoring adhesive was injected into the holes to a depth of not less than 2 / 3 of the hole depth.

[0082] (12) At a certain distance from the starting well opening, construct several foundation hidden beams that are perpendicular to the gantry crane track and anchored to the gantry crane beams on the side of the starting well, and apply force to the supporting shield block raft foundation at the foundation hidden beams.

[0083] Because the cutterhead has a certain weight, its individual sections need to be assembled and welded on the side of the launching shaft after arriving on site, and then hoisted into the shaft as a whole. Therefore, the welding of the cutterhead requires high precision. If ground subsidence occurs in the load-bearing area of ​​the cutterhead, it will have a very serious adverse impact on the welding accuracy and operation of the cutterhead. Therefore, in this embodiment, a cutterhead hoisting foundation is set on one side of the launching shaft to achieve stable load-bearing of the cutterhead. Furthermore, this cutterhead hoisting foundation is located at a certain distance from the launching shaft to avoid adverse effects of the load on the launching shaft structure. In this embodiment, see... Figure 2 The cutterhead hoisting foundation includes a reinforced concrete raft foundation measuring 30.5m in length, 17m in width, and 50cm in thickness. It also features three 500*500mm reinforced concrete foundation beams perpendicular to the gantry crane track. The reinforcing bars of these foundation beams are anchored to the reinforcing bars of the gantry crane beams outside the well to share the load and enhance the strength. Furthermore, six bored piles are installed at the intersection of the foundations to bear the loads during the welding, assembly, and hoisting of the cutterhead into the well, further improving the strength.

[0084] Although some preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0085] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of the invention. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for constructing a shield tunneling foundation, characterized in that, Includes the following steps: (1) On both sides of the starting wellhead that meets the height restriction requirements, the pile hole layout points that match the track spacing of the gantry crane to be installed are determined by total station, and the line connecting the pile holes on both sides is perpendicular to the axis of the starting well. (2) After the casing is vertically installed at each of the pile hole locations, the drilling rig enters the site and is positioned, mud is prepared and the center line of the drilling rod of the drilling rig is adjusted to coincide with the center line of the casing, and the pile hole drilling operation is carried out. (3) Fabricate a steel cage that matches the pile hole. The steel cage includes a main bar arranged in a circular array, a reinforcing stirrup perpendicular to the main bar and sleeved on the main bar, and a spiral stirrup corresponding to the main bar. A number of protective layer pads arranged in a circumferential quincunx pattern are also arranged along the axial direction of the steel cage. (4) When a crane that meets the height limit requirements enters the site, after the pile hole is cleaned, the coaxially segmented steel cage is hoisted into the pile hole. When the top of each segment is lowered to the top of the casing, a spreader bar is inserted into the steel cage to hang the steel cage on the top of the casing. Then the next section of steel cage is hoisted. After welding the main bars of the two sections of steel cage, the spreader bar is removed. This step is repeated until the steel cage is completely inserted into the pile. (5) Install a guide pipe in the pile hole, clean the hole and carry out continuous concrete pouring operation until the pile hole is filled with concrete slurry and the cast-in-place pile is formed. (6) Measure and lay out the centerline and foundation boundary of the gantry crane track to be installed. The gantry crane track is set on both sides of the well opening with a relatively loose height limit, perpendicular to the centerline of the starting well, and coincides with the line connecting the corresponding pile holes. According to the layout, excavate the gantry crane beam trench with a certain depth and width outside the well. After excavating to the design elevation, level and compact the bottom of the trench. (7) Tie steel bars in the groove of the external portal crane beam and arrange several portal crane track embedded parts along the axial direction of the external portal crane beam groove. After verifying the position of the portal crane track embedded parts, construct and pour the external portal crane beam. (8) Backfill clay in a trapezoidal shape above the top slab of the standard section of the launching shaft and between the retaining walls on the corresponding side of the launching shaft where the height limit is relatively loose, up to the bottom height of the gate beam outside the shaft; (9) Triangular cross-section trenches are excavated on both sides of the gantry crane track along the backfill clay at the corresponding underground continuous wall of the starting shaft, and triangular reinforced concrete brackets are set in the trenches. (10) Construct a well-side gantry crane beam that coincides with the centerline of the gantry crane track, cut the underground continuous walls on both sides of the starting well to expose the vertical main reinforcement of the underground continuous walls, tie the well-side gantry crane beam reinforcement between the vertical main reinforcement of the underground continuous walls on both sides, and then construct the formwork and pour the concrete, wherein the well-side gantry crane beam reinforcement intersects with the external gantry crane beam reinforcement. (11) A groove is opened at the top of the underground continuous wall ring frame beam on the other side of the starting shaft where the height limit is relatively loose, which coincides with the center line of the gantry crane track. At the bottom of the groove, a number of gantry crane track embedded parts with the same elevation as the gantry crane track embedded parts at the outside of the shaft are arranged in an array with rebar. (12) At a certain distance from the starting well opening, construct several foundation hidden beams perpendicular to the gantry crane track and anchored to the gantry crane beams on one side of the starting well, and apply force to the supporting shield block raft foundation at the foundation hidden beams.

2. The method for constructing a shield tunneling foundation according to claim 1, characterized in that, In step (2), the casing is 30-40cm above the ground, and at least one overflow port is provided at the corresponding position of the top edge of the casing.

3. The method for constructing a shield tunneling foundation according to claim 1, characterized in that, In step (3), the beginning and end of the spiral stirrup each include a horizontal section perpendicular to the main reinforcement of the steel cage, and the length of the horizontal section is not less than one and a half turns.

4. The method for constructing a shield tunneling foundation according to claim 1, characterized in that, In step (5), a trial assembly and water tightness test are carried out before the guide pipe is installed into the pile, and the bottom of the guide pipe is 30-50cm away from the bottom of the pile hole after it is installed into the pile; the depth of the guide pipe embedded in the concrete during concrete pouring is not less than 2m.

5. The method for constructing a shield tunneling foundation according to claim 1, characterized in that, In step (7), the gantry rail embedded part includes a fixing screw rod symmetrically arranged on both sides of the gantry beam groove outside the well, and a horizontal plate sleeved between the two fixing screw rods; the horizontal plate is arranged at a height lower than the ground elevation.

6. The method for constructing a shield tunneling foundation according to claim 1, characterized in that, In step (7), after the external gate lifting beam is poured, a trapezoidal concrete anti-collision block is poured at the corresponding end of the external gate lifting beam.

7. The method for constructing a shield tunneling foundation according to claim 1, characterized in that, In step (7), the pile hole is pre-treated before the well gate lifting beam is poured. After the pile hole is broken down to the top elevation position by a pneumatic pick, the top reinforcement of the pile is straightened and pre-bent, and the pre-bending angle is not greater than 15°.

8. The method for constructing a shield tunneling foundation according to claim 1, characterized in that, In step (8), the clay is backfilled and compacted in layers, and the layer thickness is no more than 500 mm; the slope of the trapezoidal backfill is 1:1.

5.

9. The method for constructing a shield tunneling foundation according to claim 1, characterized in that, In step (9), the angle between the reinforced concrete corbel and the corresponding diaphragm wall is 45°, and the drilled rebar is anchored into the corresponding diaphragm wall.

10. The method for constructing a shield tunneling foundation according to claim 1, characterized in that, In step (12), a cast-in-place pile is provided at the intersection of the foundation hidden beam and the well gate lifting beam.

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