Construction method for simultaneously breaking through double-hole portal of assembled vertical shaft in water-rich soft soil layer

Abstract

The application provides a construction method for simultaneously breaking two holes of an assembled vertical shaft in a water-rich soft soil layer, and relates to the technical field of shield tunnels. The method comprises the following steps: 1, drilling and coring in two to-be-broken areas and inspecting the water-stopping effect of the reinforcing body; 2, after the water-stopping effect is qualified, the two to-be-broken areas are divided into multiple layers, and each layer is divided into multiple blocks; 3, the layers of the two to-be-broken areas are cut in units of blocks, and after the blocks are taken out, concrete is sprayed on the working face; 4, after the breaking of the layers at the same height in the two to-be-broken areas is completed and the concrete is solidified, the sand is backfilled to the height of the upper edge of the concrete; 5, steps 3 to 4 are repeated until the breaking of the two to-be-broken areas is completed and the concrete is solidified, the sand is filled to a first predetermined height, and clean water is poured to a second predetermined height; the concrete is sprayed to close the working face and form a supporting effect; the sand is backfilled to form lateral counterpressure, and the risks of water and sand gushing and soil instability in the stratum are inhibited.

Description

Technical Field

[0001] This application relates to the field of shield tunnel technology, and in particular to a construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata. Background Technology

[0002] When constructing shield tunnels using prefabricated shafts in water-rich soft soil strata, it is often necessary to break through the sidewalls of the shaft to create portals formed by the shaft segments in order to connect the tunnel sections with the shaft. For large-diameter shield tunnels, the portal segments are typically thick and have high concrete strength. Under conditions of high water pressure and weak strata, the tunnel face is highly susceptible to engineering hazards such as water inrush, sand inrush, and soil instability during the portal breaking process. Currently, the breaking of portals in large-diameter deep shafts is generally carried out using mechanical impact chiseling or manual pneumatic picks. This involves directly breaking the concrete segments within the portal area and removing them piece by piece. After the segments are broken, a thin layer of cement mortar is used for filling. This method is applicable to small portals with small diameter and thin segments, but for large diameter shield tunnel segments with large thickness and high strength, the compressive and shear strength of the thin cement mortar layer is much lower than that of the original segments. It cannot effectively replace the circumferential support of the original segments and is difficult to balance the huge lateral water and soil pressure around the portal. This can easily lead to stress concentration and structural cracking of the segments around the portal. In addition, the existing demolition process has low construction efficiency, resulting in the tunnel face being exposed to the open for a long time. The soil's self-stabilizing ability continues to deteriorate with the extension of exposure time. Once the tunnel face shows signs of instability, it cannot effectively suppress the risk of water inrush, sand inrush and soil instability in the water-rich soft soil strata. Summary of the Invention

[0003] The purpose of this application is to address the above problems by providing a construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata. The vertical shaft is equipped with shaft segments, and portals are symmetrically arranged inside the shaft about its central axis. The two portals are distributed along the tunneling direction of the tunnel boring machine. A reinforcing body is provided on the outer side of the vertical shaft near the portals, and the side of the reinforcing body near the portals has a working face. The construction method includes: Step 1: Mark multiple first core sampling points in two areas to be demolished, drill and extract cores from the first core sampling points in the two areas to be demolished, and check the water-stopping effect of the reinforced body; the areas to be demolished are the areas on the vertical shaft segments corresponding to the tunnel portal along the tunneling direction of the tunnel boring machine. Step 2: If the water-stopping effect of the solidified body is qualified, the two areas to be broken are divided into multiple layers in the vertical direction, and each layer is divided into multiple blocks in the horizontal direction. Step 3: Using the blocks as units, cut the bottommost and unbroken layers of the two areas to be broken in a predetermined order, and remove the blocks of the layers; after each block is removed, spray concrete of a predetermined thickness onto the area on the working face corresponding to the block; the predetermined order is from the middle of the layers to both sides. Step 4: After the bottommost layers of the two areas to be demolished have been demolished and the concrete of the demolished layers has solidified, backfill sand between the two openings to the height of the upper edge of the concrete. Step 5: Repeat steps 3 to 4 until all layers in the two areas to be demolished are demolished and the concrete of each layer has solidified. Backfill the shaft with sand to a first predetermined height and pour clean water to a second predetermined height. The height of the shaft opening is greater than the second predetermined height, the second predetermined height is greater than the first predetermined height, and the first predetermined height is greater than the height of the upper edge of the portal.

[0004] According to the technical solutions provided in certain embodiments of this application, the step of simultaneously cutting the lowermost and unbroken layers of the two regions to be broken in a predetermined order includes: A wire saw is used to cut the lowest, unbroken layer of blocks located at the edge of the area to be broken; a water drill is used to drill and core the lowest, unbroken layer of blocks located inside the area to be broken, thereby separating each block from the surrounding shaft segments.

[0005] According to the technical solutions provided in certain embodiments of this application, the step of spraying concrete of a predetermined thickness onto the area corresponding to the segment on the working face includes: Clean the area to be sprayed and mix, and set a template on the interface between the shaft segment and the area to be sprayed and mix; the area to be sprayed and mix is ​​the area exposed on the working face after each segment is removed; Concrete is sprayed layer by layer onto the area to be sprayed, and the next layer of concrete is sprayed after each layer of concrete has solidified, until the concrete thickness of the area to be sprayed reaches the predetermined thickness.

[0006] According to the technical solutions provided in certain embodiments of this application, the step of extracting the layered blocks includes: A transport platform is laid at the bottom of the shaft using steel plates, and a transport track is erected on the transport platform. The block is dragged along the transport track from the area to be demolished to the hoisting area inside the shaft.

[0007] According to the technical solutions provided in certain embodiments of this application, the step of marking multiple first core sampling points in two areas to be broken, drilling and core sampling at the first core sampling points in the two areas to be broken, and verifying the water-stopping effect of the reinforced body includes: Multiple first core extraction points are evenly marked in the two areas to be broken; A water drill is used to drill holes and extract cores sequentially at each of the first core sampling points along the radial direction of the vertical shaft. After the core sampling is completed, a sealing steel plate and a ball valve switch are installed at the drilled hole. The ball valve switch is used to check whether the borehole is leaking. If there is no leakage in any borehole, the water-stopping effect of the solidification body is deemed to be qualified. If any borehole is leaking, the borehole is sealed. After sealing, a new core is drilled around the sealing position and the borehole is checked for leakage. This process is repeated until there is no leakage in any borehole, at which point the water-stopping effect of the solidification body is deemed to be qualified.

[0008] According to the technical solutions provided in certain embodiments of this application, the step of using a water drill to drill and core samples from the lowest, unbroken layer within the area to be broken includes: If the boundary of the segment is located between two adjacent shaft segments, the second core sampling point is marked according to the position of the connection point between the two adjacent shaft segments; if the boundary of the segment is located on the shaft segment, the second core sampling point is marked sequentially along the boundary of the segment. Water drills are used to sequentially drill and extract cores from each of the second core sampling points along the tunneling direction of the tunnel boring machine. At the same time, lifting lugs are anchored on the blocks so that the blocks can be lifted through the lifting lugs after the blocks are cut.

[0009] According to the technical solutions provided in certain embodiments of this application, after the block is dragged along the transport track from the area to be demolished to the hoisting area in the shaft, the method further includes: The block is flipped so that its inner arc surface faces upward, and then lifted vertically out of the shaft by a crane.

[0010] According to the technical solutions provided in certain embodiments of this application, after the blocks are removed and before spraying concrete of a predetermined thickness onto the area corresponding to the blocks, the process further includes: Clean the interface between the shaft segment and the area to be sprayed to make the interface smooth.

[0011] According to the technical solutions provided in certain embodiments of this application, the spraying pressure of the sprayed concrete is 0.3~0.7MPa, the distance between the nozzle and the sprayed surface is 1.5~2.0m, and the angle between the axis of the nozzle and the sprayed surface is greater than or equal to 70°.

[0012] Compared with the prior art, the beneficial effects of this application are as follows: This application provides a construction method for the simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata. Vertical shaft segments are laid inside the shaft, and portals are symmetrically arranged about its central axis inside the shaft. The two portals are distributed along the tunneling direction of the tunnel boring machine (TBM). A reinforcement body is provided on the outer side of the shaft near the portal, and the side of the reinforcement body near the portal has a working face. The construction method includes: 1. Marking multiple first core sampling points in two areas to be demolished, drilling and core sampling at the first core sampling points in each of the two areas to be demolished, and verifying the water-stopping effect of the reinforcement body; the areas to be demolished are the areas on the vertical shaft segments corresponding to the portals along the tunneling direction of the TBM; 2. If the water-stopping effect of the reinforcement body is qualified, the two areas to be demolished are divided into multiple layers vertically, and each layer is divided into multiple blocks horizontally; 3. Using blocks as units, the bottommost unbroken layers of two areas to be demolished are simultaneously cut in a predetermined order, and the blocks of that layer are removed. After each block is removed, concrete of a predetermined thickness is sprayed onto the area on the working face corresponding to that block. The predetermined order is from the middle of the layer to both sides. Fourth, after all the layers near the bottom of the shaft in both areas to be demolished are demolished and the concrete of the demolished layers has solidified, sand is backfilled between the two portals to the height of the upper edge of the concrete. Fifth, repeat steps three and four until all layers in both areas to be demolished are demolished and the concrete of each layer has solidified. Sand is backfilled into the shaft to the first predetermined height and clean water is poured in to the second predetermined height. The height of the shaft opening is greater than the second predetermined height, the second predetermined height is greater than the first predetermined height, and the first predetermined height is greater than the height of the upper edge of the portal. By simultaneously breaking down the two tunnel portals and operating in a layered and segmented manner, the breaking efficiency was greatly improved. At the same time, the exposed area of ​​the tunnel face was controlled within a small area of ​​a single segment, which solved the problems of low breaking efficiency and long-term large-area exposure of the tunnel face leading to deterioration of the soil's self-stabilizing ability. By spraying a predetermined thickness of concrete after each segment is removed, the tunnel face can be quickly sealed and the broken area can be supported, replacing the original circumferential support function of the tunnel segment, balancing the lateral water and soil pressure around the large-diameter vertical shaft, and solving the problem that the existing technology has insufficient strength of thin-layer cement mortar and cannot be adapted to large-diameter thick tunnel segments. After the first layer at the same height as the two tunnel portals is demolished, sand is backfilled between the two portals to the height of the upper edge of the concrete. This backfilled sand creates continuous lateral active counterpressure on both sides of the demolished sections. This solves the problem of the lack of emergency measures when the existing technology faces signs of instability. It constructs a graded counterpressure system, which effectively suppresses the risks of water inrush, sand inrush, and soil instability in water-rich soft soil strata.

[0013] It should be understood that the descriptions of technical features, technical solutions, beneficial effects, or similar language in this application do not imply that all features and advantages can be achieved in any single embodiment. Rather, it is understood that the description of a feature or beneficial effect means that a specific technical feature, technical solution, or beneficial effect is included in at least one embodiment. Therefore, the descriptions of technical features, technical solutions, or beneficial effects in this specification do not necessarily refer to the same embodiment. Furthermore, the technical features, technical solutions, and beneficial effects described in this embodiment can be combined in any suitable manner. Those skilled in the art will understand that embodiments can be implemented without one or more specific technical features, technical solutions, or beneficial effects of a particular embodiment. In other embodiments, additional technical features and beneficial effects may be identified in specific embodiments that do not embody all embodiments. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 A schematic diagram of the construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata provided in this application; Figure 2 This is a schematic diagram of the vertical shaft and the reinforced structure; Figure 3 This is a schematic diagram of the area to be cleared. Figure 4 A schematic diagram of the vertical shaft after the portal portal has been breached; Figure 5 This is a schematic diagram showing the segmentation of the area to be broken down.

[0016] The text labels in the image represent: 1. Shaft; 2. Shaft segment; 3. Area to be demolished; 4. First core sampling point; 5. Layering; 6. Portal; 7. Reinforced body; 8. Portal steel ring; 9. RJP reinforced body; 10. TRD cement wall; 11. MJS reinforced body; 12. Segmentation. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The descriptions in this section are merely illustrative and explanatory, and should not be construed as limiting the scope of protection of this application. Specifically, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort should fall within the scope of protection of this invention.

[0018] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or apparatus.

[0019] Please refer to Figure 2 Shaft 1 is constructed vertically, and the shield tunnel passes through it. Shaft segments 2 are laid inside shaft 1. Two portals 6 are located at the bottom of shaft 1, distributed along the tunneling direction of the shield machine. The two portals 6 are symmetrically arranged about the central axis of shaft 1, and portal steel rings 8 are installed on the portals 6. On the outer side of shaft 1, near the two portals 6, there are reinforcement bodies 7. The reinforcement bodies 7 adopt a composite reinforcement system, including RJP reinforcement body 9, TRD cement wall 10, and MJS reinforcement body 11 arranged sequentially from the side away from portal 6 to the side closer to portal 6. The side of MJS reinforcement body 11 closest to shaft segments 2 has a working face. In addition, since shaft 1 is a prefabricated shaft, during the construction of shaft 1, it needs to be coordinated with the shaft excavation device. The pipe segments formed by splicing shaft segments 2 are simultaneously lowered into shaft 1 through the pipe segment lifting device. The pipe segment lifting device is connected to the pipe segments through steel strands. After the construction of shaft 1 is completed, the steel strands are located between shaft segments 2 and reinforcement bodies 7.

[0020] Please refer to Figure 1 This embodiment provides a flowchart of a construction method for the simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata. Vertical shaft segments 2 are laid inside the shaft 1. Two portals 6 are symmetrically arranged inside the shaft 1 about its central axis, distributed along the tunneling direction of the tunnel boring machine. A reinforcing body 7 is provided on the outer side of the shaft 1 near the portals 6. The side of the reinforcing body 7 near the portals 6 has a working face. The construction method includes: Step 1: Mark multiple first core sampling points 4 in the two areas to be broken 3, drill and core samples from the first core sampling points 4 in the two areas to be broken 3 respectively, and check the water-stopping effect of the reinforcement 7; the area to be broken 3 is the area on the vertical shaft segment 2 that corresponds to the tunnel portal 6 along the tunneling direction of the shield machine.

[0021] Specifically, after the reinforcement of the solidification body 7 is completed, the reinforcement effect of the portal 6 is first preliminarily inspected through the grouting holes on the vertical shaft segment 2. A ball valve switch is installed at the grouting hole, the ball valve switch is opened, and an electric drill is used to dredge the inside of the grouting hole through the ball valve hole to a depth of 1.5m, and it is observed whether water flows out. When the water outflow from the grouting hole is less than 0.1L / h and there are no abnormal phenomena such as mud and sand flowing out of the hole, the next step can be carried out. If the water outflow from the grouting hole is large, grouting is used to seal it. 30 minutes after the grouting is completed, the sealing effect is checked through 1 to 2 nearby grouting holes. When all the grouting holes with water seepage are sealed and the adjacent grouting holes meet the standard of water outflow less than 0.1L / h, the next step can be carried out.

[0022] Furthermore, the step of marking multiple first core sampling points 4 within the two areas to be broken 3, drilling and core sampling at the first core sampling points 4 within the two areas to be broken 3, and verifying the water-stopping effect of the reinforced body 7 includes: Multiple first core extraction points 4 are evenly marked within the two areas to be broken 3; Water drills were used to drill and extract cores at each of the first core sampling points 4 in the radial direction of the vertical shaft 1. After the cores were extracted, a sealing steel plate and a ball valve switch were installed at the drilled holes. Check for water leakage in the boreholes by switching on and off the ball valve. If there is no water leakage in any borehole, the water-stopping effect of the solidification body 7 is deemed to be qualified. If any borehole leaks water, the borehole is sealed. After sealing, re-drill holes around the sealing location to obtain core samples and check for water leakage. Continue until there is no water leakage in any borehole, then the water-stopping effect of the solidification body 7 is deemed to be qualified.

[0023] For details, please refer to Figure 3Multiple first core sampling points 4 are evenly marked within the two areas 3 to be demolished. The number of first core sampling points 4 can be selected according to actual needs. In this embodiment, there are 9 first core sampling points 4, selected at the center of the area 3 to be demolished and on two circles concentric with the area 3 but with different radii, to ensure that the first core sampling points 4 are evenly distributed within the area 3 to be demolished. After the positions of the first core sampling points 4 are determined, water drills are used to drill holes for core sampling at the first core sampling points 4. The drilling is carried out radially along the shaft 1 with a hole diameter of 75mm. One first core sampling point 4 is selected in each of the two areas 3 to be demolished, and the drilling depth is 15m. The drilling depth of the remaining first core sampling points 4 is 3m. All first core sampling points 4 should not penetrate the TRD cement wall during drilling. 10. After core drilling is completed, install a sealing steel plate and a 50mm diameter ball valve at the drilled hole. Check for water seepage in the drilled hole using the ball valve. If there is a small amount of water seepage, observe the hole further to check if the seepage contains sand and whether the seepage increases or decreases. If the seepage gradually increases, use a two-component grout to seal the hole. After grouting, re-drill and core the hole near the original hole until there is no water seepage. If the seepage gradually decreases, seal the hole with cement after all cores at the first core point 4 are drilled. If a large amount of sand or water is found during core drilling, drilling should be stopped immediately, the hole should be temporarily sealed, and a sealing steel plate should be installed for grouting and reinforcement. If there is no water seepage in any of the drilled holes, there is no need to seal the holes.

[0024] Step 2: If the water-stopping effect of the solidified body 7 is satisfactory, then the two areas to be broken 3 are divided into multiple layers 5 in the vertical direction, and each layer 5 is divided into multiple blocks 12 in the horizontal direction.

[0025] For details, please refer to Figure 5 After the water-stopping effect of the reinforced solid is qualified, the area to be demolished 3 is divided into twelve layers 5 from bottom to top according to the circumferential joint of the shaft segment 2 and the scaffolding height during the demolition of the portal 6. According to the longitudinal joint of the shaft segment 2 and the load-bearing range of the crane during hoisting, each layer 5 is divided into multiple blocks 12 to ensure that a single block 12 can be lifted and transported out of the shaft 1 by a crane after demolition. The edges of the area to be demolished 3 and the boundaries of each block 12 are marked with red paint.

[0026] Step 3: Using blocks 12 as units, cut the bottommost and unbroken layers 5 of the two areas to be broken 3 in a predetermined order and remove the blocks 12 of the layer 5. After each block 12 is removed, spray concrete of a predetermined thickness onto the area on the working face corresponding to the block 12. The predetermined order is from the middle of the layer 5 to both sides.

[0027] Specifically, when breaking down region 3, the process begins with the layer 5 (the first layer), which is currently the lowest layer of region 3. The block 12 located at the vertical center line of region 3 is broken down as the first block of the layer. After the first block is broken down, the block 12 to the left of the first block is broken down as the second block, and then the block 12 to the right of the first block is broken down as the third block. After the first layer is broken down, the process continues from bottom to top. If there are two blocks 12 in layer 5 near the center line of region 3, the block 12 to the left of the center line is broken down as the first block, and then the block 12 to the right of the center line is broken down. After the two blocks 12 at the center line are broken down, the remaining two blocks 12 are broken down from left to right in the same order.

[0028] Furthermore, the step of simultaneously cutting the bottommost and unbroken layers 5 of the two regions to be broken 3 in a predetermined order includes: A wire saw is used to cut the bottommost unbroken layer 5 at the edge of the area to be broken 3; a water drill is used to drill and core the bottommost unbroken layer 5 at the inside of the area to be broken 3, thereby separating each section 12 from the surrounding shaft segments 2.

[0029] Specifically, during the production of shaft segment 2, PVC pipes are pre-embedded inside shaft segment 2, with iron wires pre-installed inside the PVC pipes. Marks are made on the inner arc surface of shaft segment 2 corresponding to the pipe openings of the PVC pipes. During demolition, the concrete of shaft segment 2 is chiseled away to expose the pipe openings of the PVC pipes. The chain of the wire saw is then threaded through the iron wire inside the PVC pipe and led out. The chain is then installed on the drive wheel of the wire saw. The guide wheel of the wire saw is aligned with the center line of the PVC pipe, and the boundary of segment 12 is cut along the edge of the area to be demolished 3 from bottom to top. During cutting, the linear speed of the wire saw is 18~22m / s, and the feed speed is 1.0~1.5m / h to ensure that the cutting surface of segment 12 is parallel to the tunneling direction of the tunnel boring machine. This avoids the situation where the volume of segment 12 near the working face is too large after cutting, making it impossible to remove segment 12. If the wire saw malfunctions and cannot cut, a water drill is used to drill holes to replace the wire saw cutting.

[0030] Furthermore, the step of using a water drill to drill and core the lowermost, unbroken layer 5, segment 12, located within the area to be broken, includes: If the boundary of segment 12 is located between two adjacent shaft segments 2, then the second core sampling point is marked according to the position of the connection point between the two adjacent shaft segments 2; if the boundary of segment 12 is located on shaft segment 2, then the second core sampling point is marked sequentially along the boundary of segment 12. Water drills were used to drill and extract cores at each of the second core sampling points along the tunnel boring machine's excavation direction. At the same time, lifting lugs were anchored on block 12 so that block 12 could be lifted and installed after it was cut.

[0031] Specifically, the second core sampling point is marked by drawing cross lines on the boundary of segment 12. When the boundary of segment 12 is located at the splice joint of two adjacent shaft segments 2, the second core sampling point is marked according to the position of the connector between the two segments. When the boundary of segment 12 is located on shaft segment 2, the second core sampling point is marked sequentially according to the diameter of the water drill hole, so that the drill holes can be interconnected after water drilling. Similarly, to avoid the situation where the volume of segment 12 near the working face is too large after cutting, making it impossible to remove segment 12, the drilling direction of the water drill should extend along the tunnel boring machine's excavation direction. The base of the water drill is fixed on the shaft segment 2, and shims are set between the water drill base and the inner arc surface of the shaft segment 2 to ensure that the drill bit of the water drill extends along the tunnel boring machine's excavation direction. After fixing, the water drill is started. First, grind a 2-3cm deep positioning groove on the inner arc surface of the vertical shaft segment 2. After confirming that the drill bit does not slip or deviate, adjust it to the normal speed and apply the feed force evenly. Every 10cm of drilling, use a spirit level to check the levelness of the drill rod of the water drill and check the hole position deviation. If there is a deviation, make a fine adjustment immediately. When the drilling depth reaches 85cm, keep the water drill running idle and continue to supply water for 10 seconds to flush away the debris in the drill hole. Then slowly stop the feed and check whether the core sample in the drill hole is loose. If the core sample is loose, take out the drill rod, drill bit and core sample together. After drilling each second core sampling point, check whether the hole position, hole diameter, hole depth and levelness are qualified, and whether there is water seepage in the drill hole. After all are qualified, turn off the water drill and move to the next second core sampling point to continue drilling and core sampling until the boundary of the current segment 12 is completely drilled.

[0032] Further, the step of extracting block 12 of layer 5 includes: A transport platform is laid at the bottom of shaft 1 using steel plates, and a transport track is erected on the transport platform; The block 12 is dragged along the transport track from the area to be demolished 3 to the hoisting area inside the shaft 1; Flip segment 12 so that its inner arc surface faces upward, and use a crane to lift segment 12 vertically out of shaft 1.

[0033] Specifically, since the connecting parts between segment 12 and the surrounding shaft segments 2 were severed during the demolition process, to prevent segment 12 from sinking after demolition, the lifting lugs were simultaneously fixed to the center of gravity of segment 12 using chemical anchors, and segment 12 was suspended using a hand-operated hoist. A transport platform was laid at the bottom of shaft 1 using 2cm thick steel plates, and a transport track was erected on the transport platform. After the transport track was erected, excavators and other utility vehicles were used to connect to the lifting lugs anchored on segment 12 via steel wire ropes, and segment 12 was dragged along the transport track to the shaft. The hoisting area at the center of shaft 1; after segment 12 arrives at the hoisting area, segment 12 is rotated 90° so that the inner arc surface of segment 12 faces upward. When the weight of segment 12 is 3 tons or more, use slings to connect the lifting lugs on segment 12 to the crane. When the weight of segment 12 is less than 3 tons, use wire ropes to connect the lifting lugs on segment 12 to the crane. After the connection is completed, a trial hoisting is carried out, lifting segment 12 to a height of 0.2~0.3m for more than 10 minutes. If no abnormal situation occurs during the hoisting, the formal hoisting can be carried out, and segment 12 is vertically hoisted out of shaft 1.

[0034] Furthermore, the process of spraying concrete of a predetermined thickness onto the area corresponding to block 12 on the working face includes: Clean the area to be sprayed and set a template on the interface between the shaft segment 2 and the area to be sprayed; the area to be sprayed is the area exposed on the working face after each segment 12 is removed; Apply concrete layer by layer to the area to be sprayed, and after each layer of concrete has solidified, apply the next layer of concrete until the concrete thickness of the area to be sprayed reaches the predetermined thickness.

[0035] Specifically, after segment 12 is removed, the residual concrete between the two drill holes on the interface is cleaned using a pneumatic hammer or by injecting an expansion fracturing agent. Simultaneously, exposed steel strands are removed using a cutting machine. High-pressure air is used to clean the area to be sprayed, and a template is set on the interface to isolate the concrete from the undamaged shaft segment 2. After the template is installed, the spraying robot is positioned, ready to spray concrete onto the area to be sprayed. Concrete spraying is carried out layer by layer. The spraying robot is started, and spraying begins when its spraying pressure reaches 0.5 MPa. First, the pitted areas on the working face are leveled by spraying concrete, then the first layer of concrete is sprayed. The spraying pressure is 0.3~0.7 MPa, the distance between the nozzle and the sprayed surface is 1.5~2.0 m, the nozzle axis is kept as perpendicular to the sprayed surface as possible, and the included angle should be greater than or equal to 70°. The nozzle moves laterally in a circular motion, and the thickness of each layer of concrete is 10~15 cm. Each layer of concrete is sprayed after it has solidified. Before spraying the next layer, the surface of the solidified previous layer is cleaned. Then, spraying continues as described above until the concrete thickness in the area to be sprayed reaches the predetermined thickness, which is the same as the thickness of shaft segment 2. After the concrete spraying is completed and solidified for 2 hours, the concrete is sprayed for curing. Preferably, a fiberglass mesh can be placed between the two layers of concrete to enhance the connection strength between the two layers. When spraying, a low-grade concrete, such as C20 concrete, is selected. Since shaft segment 2 is made of C60 concrete, using a low-grade concrete for spraying serves two purposes: firstly, it can replace the circumferential support function of the broken segment after shaft segment 2 is broken; secondly, the strength of the sprayed concrete is lower than that of the original segment, so it only provides temporary support and does not affect the subsequent shield tunneling. The thickness of the concrete spraying can also be adjusted according to the actual situation, such as a spraying thickness of 30~50cm.

[0036] Step 4: After the bottommost layer 5 of both areas to be demolished 3 has been demolished and the concrete of the demolished layer 5 has solidified, backfill sand between the two openings 6 to the height of the upper edge of the concrete.

[0037] Specifically, after the bottommost layer 5 of both areas to be demolished 3 has been demolished and the concrete of the demolished layer 5 has solidified, sand is transported into the shaft 1 through a bucket to backfill the bottom of the shaft 1. The sand is backfilled between the two portals 6, so that the sand covers the upper edge of the demolished layer 5, thereby forming a lateral counterpressure on the demolished layer 5 and preventing water inrush, sand inrush and soil instability at the working face.

[0038] Step 5: Repeat steps 3 to 4 until all layers 5 of the two areas to be demolished 3 are demolished and the concrete of each layer 5 has solidified. Backfill sand into the shaft 1 to the first predetermined height and pour clean water to the second predetermined height. The height of the shaft opening of the shaft 1 is greater than the second predetermined height, the second predetermined height is greater than the first predetermined height, and the first predetermined height is greater than the height of the upper edge of the portal 6.

[0039] For details, please refer to Figure 4 After the sand backfilling is completed in step four, continue to break down the bottom layer 5 of the two areas to be broken down that have not been broken down in the current two areas to be broken down 3, and spray concrete. After the concrete solidifies, backfill sand to the upper edge of the layer 5, until all layers of the two areas to be broken down 3 are broken down and the concrete solidifies. Backfill sand into the shaft 1 to 2m above the upper edge of the portal steel ring 8 (first predetermined height), and then pour clean water back into the shaft 1 to 1m below the shaft opening (second predetermined height). At this point, the construction of breaking down the portal 6 is completed.

[0040] Working principle: Multiple first core sampling points 4 are marked within the two areas 3 to be demolished. Core samples are taken from these first core sampling points 4, and the water-stopping effect of the reinforced body 7 is tested. After the water-stopping effect of the reinforced body 7 is deemed satisfactory, the two areas 3 to be demolished are divided vertically into twelve layers 5, and each layer 5 is further divided horizontally into multiple blocks 12. Using blocks 12 as units, the blocks 12 within the first layer of the two areas 3 to be demolished are cut using a combination of wire saw and water drill. The middle block 12 of the first layer is cut first, followed by cuts from left to right. After each block 12 is cut, it is dragged to the hoisting area and placed on the working face corresponding to the block 12. After the concrete is sprayed to the same thickness as the shaft segment 2 and has solidified and the segment 12 in the hoisting area has been hoisted out of the shaft 1, sand is backfilled between the two portals 6 to the upper edge of the first layer. Then, the second layer of the two areas to be demolished 3 is demolished. After the second layer is demolished and the concrete in the second layer has solidified, sand is backfilled between the two portals 6 to the upper edge of the second layer. The above process is repeated until the twelfth layer of the two areas to be demolished 3 is demolished and the concrete in the twelfth layer has solidified. Sand is backfilled into the shaft 1 to 2m above the upper edge of the portal steel ring 8, and then clean water is poured back in to 1m below the shaft opening of the shaft 1. At this point, the demolition of portal 6 is completed.

[0041] By pre-embedding PVC pipes and threading iron wires into the shaft segment 2 during the manufacturing stage, the pre-embedded PVC pipes guide the wire saw cutting path, avoiding large-scale drilling operations on site and ensuring cutting accuracy and structural smoothness. By precisely breaking the connecting parts between the shaft segments 2 with a water drill, the overall stress inside the shaft segment 2 is released in advance. Combined with the wire saw, full-range static pre-cutting is achieved without the need for large-scale impact chiseling. The workload of breaking individual segments 12 is significantly reduced, the operation speed is greatly improved, and the exposure time of the working face is reduced, thus shortening the time window for risk accumulation from the root.

[0042] The entire operation process was free from strong impact and vibration, which neither disturbed the structure of the reinforced body 7, maintained the soil's self-stabilizing ability, and avoided the dangers of collapse and sand inrush; nor did it generate impact loads on the assembly joints of the adjacent shaft segments 2, avoiding problems such as excessive opening of the assembly joints, failure of the waterstop strip, and misalignment and deformation of the shaft segments 2, thus ensuring the structural stability and waterproof integrity of the shaft 1 lining.

[0043] By dividing the large-diameter area to be demolished 3 into multiple blocks 12 for unitized operation, the exposed area of ​​the tunnel face is always controlled within a small range of a single block 12. At the same time, a symmetrical demolition sequence is executed to ensure that the circumferential structure of the tunnel portal 6 is subjected to balanced forces. This achieves dynamic force balance between the tunnel portal 6 and the surrounding soil during the demolition process, avoiding the risk of instability caused by a large area of ​​the tunnel face being exposed.

[0044] By spraying concrete of the same thickness as shaft segment 2 onto the working face for replacement support, the solidified concrete support structure can effectively replace the circumferential support function of shaft segment 2, balance the lateral water and soil pressure around the portal 6, and avoid stress concentration and structural cracking of shaft segment 2 around portal 6. This breaks through the limitation of traditional thin-layer cement mortar being only suitable for small-diameter thin segments, and can be adapted to the portal breaking conditions of prefabricated shaft segments with ultra-large diameter, thick walls, and high-strength concrete.

[0045] The method of simultaneously breaking up two tunnel portals (6) was adopted. After each layer of the tunnel segment (5) was broken up and concrete sprayed, sand of the corresponding height was immediately backfilled into the shaft (1). The backfilled sand created continuous lateral counterpressure on both tunnel portals (6). Finally, the pressure was supplemented by water in the shaft, thus constructing a graded internal counterpressure system and active safety redundancy. On the one hand, the simultaneous operation of the two tunnels significantly improved the overall construction efficiency and shortened the total construction period. On the other hand, the layered backfilled sand could quickly suppress dangers when signs of instability appeared at the tunnel face, effectively reducing the risks of water inrush, sand inrush, and soil instability in water-rich soft soil strata. This provided a safe and efficient solution for breaking up large-diameter shield tunnel portals in large prefabricated shafts.

[0046] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are merely preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make multiple improvements, modifications, or variations without departing from the principles of this invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata, wherein vertical shaft segments (2) are laid inside the vertical shaft (1), and portals (6) are symmetrically arranged inside the vertical shaft (1) about its central axis, the two portals (6) are distributed along the tunneling direction of the tunnel boring machine, and a reinforcing body (7) is provided on the outside of the vertical shaft (1) near the portals (6), the reinforcing body (7) having a working face on the side near the portals (6), characterized in that, The construction method includes: Step 1: Mark multiple first core sampling points (4) in the two areas to be broken (3), drill and core the first core sampling points (4) in the two areas to be broken (3) respectively, and check the water-stopping effect of the reinforcement (7); the area to be broken (3) is the area on the vertical shaft segment (2) corresponding to the tunnel portal (6) along the tunneling direction of the shield machine; Step 2: If the water-stopping effect of the solidified body (7) is qualified, the two areas to be broken (3) are divided into multiple layers (5) in the vertical direction, and each layer (5) is divided into multiple blocks (12) in the horizontal direction. Step 3: Using the block (12) as a unit, cut the bottommost and unbroken layer (5) of the two areas to be broken (3) in a predetermined order, and take out the block (12) of the layer (5); after each block (12) is taken out, spray concrete of a predetermined thickness on the area of ​​the working face corresponding to the block (12); the predetermined order is from the middle of the layer (5) to both sides; Step 4: After the bottommost layer (5) of both areas to be demolished (3) has been demolished and the concrete of the demolished layer (5) has solidified, backfill sand between the two openings (6) to the height of the upper edge of the concrete. Step 5, repeat steps 3 to 4 until all layers (5) of the two areas to be demolished (3) are demolished and the concrete of each layer (5) is solidified. Backfill sand into the shaft (1) to a first predetermined height and inject clean water to a second predetermined height. The height of the shaft (1) opening is greater than the second predetermined height, the second predetermined height is greater than the first predetermined height, and the first predetermined height is greater than the height of the upper edge of the portal (6).

2. The construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata according to claim 1, characterized in that, The step of simultaneously cutting the bottommost and unbroken layers (5) of the two regions to be broken (3) in a predetermined order includes: A wire saw is used to cut the section (12) in the bottommost unbroken layer (5) at the edge of the area to be broken (3); a water drill is used to drill and core the section (12) in the bottommost unbroken layer (5) inside the area to be broken (3), thereby separating each section (12) from the surrounding shaft segments (2).

3. The construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata according to claim 1, characterized in that, The process of spraying a predetermined thickness of concrete onto the area corresponding to the segment (12) on the working face includes: Clean the area to be sprayed and mix, and set a template on the interface between the vertical shaft segment (2) and the area to be sprayed and mix; the area to be sprayed and mix is ​​the area exposed on the working face after each segment (12) is taken out; Concrete is sprayed layer by layer onto the area to be sprayed, and the next layer of concrete is sprayed after each layer of concrete has solidified, until the concrete thickness of the area to be sprayed reaches the predetermined thickness.

4. The construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata according to claim 1, characterized in that, The step of extracting the blocks (12) of the layer (5) includes: A transport platform is laid at the bottom of the vertical shaft (1) using steel plates, and a transport track is erected on the transport platform; The block (12) is dragged along the transport track from the area to be demolished (3) to the hoisting area in the shaft (1).

5. The construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata according to claim 1, characterized in that, The process of marking multiple first core sampling points (4) within two areas to be broken (3), drilling and core sampling at the first core sampling points (4) within the two areas to be broken (3), and verifying the water-stopping effect of the reinforced body (7) includes: Multiple first core extraction points (4) are evenly marked within the two areas to be broken (3); Water drills are used to drill and core the first core sampling point (4) in sequence along the radial direction of the vertical shaft (1). After the core sampling is completed, a sealing steel plate and a ball valve switch are installed at the drilled hole. Check whether the borehole is leaking by switching the ball valve. If there is no leakage in any borehole, the water-stopping effect of the solidification body (7) is deemed to be qualified. If any borehole leaks, the borehole is sealed. After sealing, re-drill holes around the sealing position to obtain cores and check whether the borehole leaks. Continue until there is no leakage in any borehole, and then the water-stopping effect of the solidification body (7) is deemed to be qualified.

6. The construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata according to claim 2, characterized in that, The process of using a water drill to drill and core samples from the lowest, unbroken layer (5) within the area to be broken (3) includes: If the boundary of the block (12) is located between two adjacent shaft segments (2), the second core sampling point is marked according to the position of the connection point between the two adjacent shaft segments (2); if the boundary of the block (12) is located on the shaft segment (2), the second core sampling point is marked sequentially along the boundary of the block (12). Water drills are used to drill and extract cores at each of the second core sampling points in sequence along the tunneling direction of the shield machine. At the same time, lifting lugs are anchored on the segment (12) so that the segment (12) can be lifted through the lifting lugs after the segment (12) is cut.

7. The construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata according to claim 4, characterized in that, After the block (12) is dragged along the transport track from the area to be demolished (3) to the hoisting area in the shaft (1), the method further includes: The block (12) is flipped so that the inner arc surface of the block (12) faces upward, and the block (12) is lifted out of the vertical shaft (1) by a crane.

8. The construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata according to claim 3, characterized in that, After the block (12) is removed, and before the area corresponding to the block (12) is sprayed with concrete of a predetermined thickness, the process also includes: Clean the interface between the vertical shaft segment (2) and the area to be sprayed and mixed, so that the interface is flat.

9. The construction method for simultaneous demolition of a prefabricated vertical shaft with two portals in water-rich soft soil strata according to claim 1, characterized in that, The spraying pressure for sprayed concrete is 0.3~0.7MPa, the distance between the nozzle and the sprayed surface is 1.5~2.0m, and the angle between the axis of the nozzle and the sprayed surface is greater than or equal to 70°.

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