Water-rich stratum ultra-short space earth pressure balance shield split launching method

Abstract

The invention provides a water-rich stratum ultra-short space earth pressure balance shield split launching method. The split launching method sequentially comprises the steps of trolley placement, launching tunnel end stratum reinforcement, launching bracket and counter-force frame installation, tunnel portal chiseling and sealing steel sleeve installation, negative ring upper half ring dismounting, negative ring upper part force transmission replacing with a steel support and the like, and the split launching method comprises the steps of trolley placement, launching tunnel end stratum reinforcement, launching bracket and counter-force frame installation, tunnel portal chiseling and sealing steel sleeve installation, negative ring upper half ring dismounting, negative ring upper part force transmission replacing with a steel support and the like. The problems of water gushing, sand gushing and excessive ground settlement occurring in water-rich stratum earth pressure balance shield split launching are solved, the earth pressure balance shield split launching process in the water-rich stratum ultra-short space is achieved, pipe pieces can be lowered from a shield hoisting opening in the launching process, soil excavation can be achieved, the soil excavation efficiency is improved, and the construction period is shortened. The problem that the shield construction advancing speed is low when the length of a shield launching well pit is far smaller than the overall size of a shield tunneling machine is smoothly solved.

Description

Technical Field

[0001] The invention relates to the technical field of shield tunnel construction, in particular to a split starting method for an ultra-short space earth pressure balance shield in a water-rich stratum. Background Art

[0002] With the development of urban subway construction, more and more underground tunnels are excavated by shield machines. The fully enclosed shield machines mainly include mud-water balance type and earth pressure balance type. The earth pressure balance shield occupies a small area and has strong applicability to the strata, so it is widely used in urban downtown areas. Due to the limitations of site and construction period, when the shield starting pit in the subway station cannot be constructed in time, the starting pit space length is much smaller than the size of the shield machine. In order to carry out shield tunnel construction simultaneously, it is necessary to adopt the shield split starting method, temporarily separate some trolleys from the main shield equipment, and after the shield excavation length reaches the condition that all trolleys can be connected to the well, all shield trolleys will be assembled together at one time to continue excavation as a whole.

[0003] During the split launching process of the existing earth pressure balance shield, due to the limited launching space, after the shield is hoisted to the launching shaft through the hoisting port, there is no extra space for movement, so it will stay at the position of the hoisting port. During the launching process of the shield, the negative ring will block the hoisting port. In order to ensure the normal excavation of the shield, a temporary excavation port will be constructed at the rear side of the launching port for excavation. If the launching space is too short, the construction space of the temporary excavation port is limited and cannot meet the normal excavation speed, thereby reducing the excavation efficiency. Moreover, due to the split launching process, the shield will not be able to move freely. The launching trolley is located on the ground. If the starting length meets the requirements, the negative ring does not block the hoisting port or the space of the temporary excavation port is large enough, after the starting excavation advances a certain length and the space meets the trolley's travel requirements, the trolley will be hoisted to the starting shaft for normal work; however, for the ultra-short starting space where the negative ring blocks the hoisting port and the temporary excavation port cannot meet the hoisting requirements, the trolley cannot be hoisted. In order to meet normal excavation, the only way is to extend the pipeline. Since the shield trolley has many pipelines, the pipeline extension process is more troublesome and the cost is relatively high.

[0004] In addition, when the earth pressure balance shield encounters water-rich strata such as sand and gravel, the shield split start needs further treatment to control the problem of water and sand gushing. If the stratum is not well reinforced, water leakage and ground subsidence are likely to occur during excavation, which can easily affect the excavation efficiency. However, the research on the reinforcement treatment of the shield start in the prior art is basically aimed at the split start of the slurry balance shield, and no research has been conducted on the reinforcement treatment of the split start end of the earth pressure balance shield. However, the slurry balance shield mainly uses mud as the main medium to balance the stratum pressure on the tunnel excavation surface. Compared with the construction method of the earth pressure balance shield, the slurry balance shield needs to set up a mud treatment site during the construction process, which has the disadvantages of large equipment footprint, high mud treatment cost, and unfriendly to the environment.

[0005] Therefore, it is necessary to propose a split starting method for an ultra-short space earth pressure balance shield in water-rich strata to address the above problems. Summary of the invention

[0006] The present invention mainly aims at the defects existing in the prior art and provides a split starting method of an ultra-short space earth pressure balance shield in water-rich strata. The method solves the problem of water and sand gushing when the earth pressure balance shield encounters water-rich strata such as sand and gravel by reinforcing and sealing the starting end, and removes and reinforces the negative ring during the starting process. At the same time, the excavation method is modified to solve the problem of low excavation efficiency of the ultra-short space shield, thereby improving the shield excavation efficiency.

[0007] In order to achieve the above technical purpose, the present invention provides a split starting method of an ultra-short space earth pressure balance shield in a water-rich stratum. The shield starting method is suitable for an earth pressure balance shield with a starting space length of 30 to 50 meters and a soil layer at the starting end being a water-rich stratum. Shield hoisting ports are reserved on the top plate and the middle plate of the starting shaft, and a temporary slag hoisting port is set at the end away from the tunnel entrance. The specific construction steps of the starting method are as follows:

[0008] S1. Determine the layout of the split starting equipment. The shield starting includes six sets of supporting trolleys, of which five sets of trolleys participate in the shield starting; separate the shield equipment between trolley No. 1 and trolley No. 2, and tilt the tail of trolley No. 1 toward the other side of the station floor. Move the grease pump of trolley No. 2 to trolley No. 1, and temporarily modify the driving wheel of the belt conveyor to the rear of the connecting bridge. The connecting bridge moves synchronously by installing a temporary bracket with rollers; the supporting trolleys No. 2 to No. 5 behind the shield machine are placed on the construction ground in sequence, and trolleys No. 2 to No. 5 are connected to the shield body, the connecting bridge, and trolley No. 1 through a temporarily extended connecting pipeline;

[0009] S2. Effectively reinforce the strata at the left and right ends of the starting tunnel. Double-tube jet grouting piles are used to reinforce water-rich strata. The slurry is cement and water glass double slurry with a concentration of 35-40 degrees Baume. Drainage wells are set up within the reinforcement range to reduce the groundwater level at the reinforced end to at least 1m below the bottom of the tunnel. Two weeks after the end is reinforced, the reinforcement effect of the tunnel portal is checked.

[0010] S3. The starting bracket is hoisted and installed in the well. The starting bracket is fixed on the station floor. After the bracket is positioned, the left and right sides are connected to the structural side wall and the bottom longitudinal beam pre-embedded steel plate through the horizontal steel. After the starting bracket is installed, the reaction frame and shield machine are hoisted and installed in the well. The axis of the starting bracket and the reaction frame coincides with the normal line of the tunnel gate.

[0011] S4. One week before the start of the shield machine, the tunnel portal is chiseled out for the first time. The concrete of the tunnel portal enclosure structure is first squeezed and cracked by static blasting, and then the broken concrete is chiseled out by a jackhammer. The inner layer of steel bars of the ground-connected wall is removed, and the outer layer of steel bars and the concrete protective layer of the continuous wall are retained. The outer layer of reinforced concrete is chiseled out one day before the shield machine is advanced, and the outer layer of steel bars is removed, and concrete is quickly sprayed to seal the entire face. Before the shield machine is driven, a sealing steel sleeve is installed outside the main structure of the tunnel portal, and a temporary sealing device is installed on the side of the steel sleeve close to the shield machine. The axis of the steel sleeve is in the same straight line as the axis of the tunnel portal.

[0012] S5. The first 0-33 meters trial excavation stage: After the shield split equipment is debugged, the negative ring is assembled using an assembling machine. In this stage, a small slag bucket is used to excavate the slag from the temporary slag lifting port behind the connecting bridge.

[0013] S6. After excavating 33 meters, trolley No. 1 is aligned and connected to the connecting bridge, the belt conveyor is moved to the rear of trolley No. 1, the grease pump on the connecting bridge is moved to trolley No. 1, and the segments are transported and excavated from the rear of trolley No. 1; the segments are transported and excavated by muck trucks, and after the rear of trolley No. 1 has completely entered the tunnel, the upper half of the segments from negative ring 1 to negative ring 7 are removed, and steel supports are used to replace the upper part of the negative ring for force transmission, so that the segments can be unloaded and excavated from the shield hoisting port;

[0014] S7. After excavating 67m, the pipe segments are unearthed and installed from the rear of the No. 1 trolley. When installing the pipe segments, the slag bucket is placed on the ground, and the pipe segments are lowered from the lifting port to the muck truck without a slag bucket. After the pipe segments are installed, the slag bucket is lifted to the muck truck by the gantry crane;

[0015] S8. After excavating 100 meters, the construction will be suspended, the previously temporarily extended pipeline will be dismantled, and the No. 2 to No. 6 trolleys will be lowered into the well in sequence for assembly with the shield, connecting bridge and No. 1 trolley. After the overall assembly and commissioning, normal excavation will be resumed. After this section is completed, the turnout will be installed and two trains of electric vehicles will be assembled to transport the slag at the same time.

[0016] The preferred technical solution of the present invention is that the shield tunneling starts in the earth pressure mode, and the earth bin pressure is 8% to 12% greater than the front water and soil pressure, that is, the initial setting value of the earth bin pressure is 1.43 kg / cm 2 When the soil pressure increases, first turn off the screw conveyor and stop discharging the soil. At the same time, observe the changes in the soil pressure in the soil bin through the pressure sensor. When the soil pressure in the soil bin reaches the set value of the soil pressure, turn on the screw conveyor and adjust the discharging speed of the screw conveyor according to the changes in the soil pressure reflected by the pressure sensor until the soil pressure remains unchanged at the set value of the soil pressure.

[0017] The preferred technical solution of the present invention is: the loose coefficient of the soil in the starting section of the shield is set to 1.3-1.5, and the amount of mucking per cycle is controlled at 60.4m 3 ~69.7m 3The excavation speed of the shield machine in the initial 0-33m trial excavation stage is preferably controlled at 2-30mm / min, the cutter head speed in the reinforced body in the initial section is controlled at 0.5-1.0rpm, and the total thrust of the shield machine is controlled within 800T before the shield tail enters the tunnel gate. Subsequently, the thrust of the shield machine is gradually increased, and the maximum thrust is controlled within 1200T.

[0018] The preferred technical solution of the present invention is as follows: the slurry for synchronous grouting during the shield starting process adopts cement mortar, the initial setting time is 7-9 hours, and the compressive strength is greater than 1.0Mpa; the secondary grouting adopts a separate grouting pump for manual grouting, and the grouting adopts a method of pressure control as the main and grouting volume control as the auxiliary, and the grouting pressure is greater than the groundwater pressure by 18%-22%, that is, the pressure at the grouting port of the starting section is controlled at 1.5-2.0Kg / cm 2 , control the ground settlement within +10㎜~-30㎜.

[0019] The preferred technical solution of the present invention is as follows: in the S1 step, trolley No. 1 is a synchronous grouting system, trolley No. 2 is mainly a hydraulic pump station, trolley No. 3 is an electrical control cabinet and a low-voltage compensation cabinet, trolley No. 4 is a box-type transformer, trolley No. 5 is a cable drum, belt conveyor drive, and belt conveyor slag discharge port, and trolley No. 6 is mainly a water pipe drum and a rail crane.

[0020] A preferred technical solution of the present invention: in the S2 step, the ratio of cement to water glass is 1:1, the jet grouting piles are arranged in a plum blossom shape and interlock with each other, the drilling starts from the side close to the starting end and gradually moves away from the end, each row is constructed with skip holes at intervals, and a precipitation well is set in the reinforcement range for precipitation; the inspection of the tunnel portal reinforcement effect includes the inspection of the strength, uniformity and permeability of the reinforcement body, specifically, 9 horizontal holes are evenly drilled at the edge of the tunnel portal, long wooden plugs are prepared before drilling the holes to prepare for plugging when water seepage is serious, and the water flow of the 9 holes is visually inspected. If the water output is large and brings out mud and sand, the ground needs to be re-grouted for reinforcement, and the drilling position is filled with long wooden plugs in time; in addition, the reinforcement body needs to be cored before starting.

[0021] The preferred technical solution of the present invention is as follows: in the S3 step, the starting bracket is installed by a gantry crane 7 days after the base plate is cast. The starting bracket adopts a finished steel structure, and the starting bracket is welded to the embedded steel plate of the station base plate; the elevation and plane position of the starting bracket are accurately located according to the measurement control points before installation; when the shield machine main unit is assembled, hard lubricating oil is applied to the track of the starting bracket; the longitudinal positioning of the reaction frame ensures that the casting tunnel door position meets the requirements after the negative 1 ring reinforced concrete segment is removed, and the lateral positioning ensures that the thrust of the shield machine transmitted by the negative ring segment acts accurately on the reaction frame; after the base of the reaction frame is connected to the lower beam on the ground, it is hoisted into the well as a whole and welded to the embedded steel plate of the base on the base plate. After the shield machine is assembled in the well, the columns and upper beams of the reaction frame are installed in place, and a diagonal brace is installed behind the reaction frame, and the diagonal brace is welded to the embedded steel plate on the base plate.

[0022] The preferred technical solution of the present invention is as follows: when chiseling for the first time in the S4 step, chisel in the order of first bottom then top, first middle then both sides; the steel sleeve in the S4 step is 800mm to 1000mm long, a rubber plate water stop and a tunnel portal embedded steel ring are arranged between the steel sleeve and the tunnel portal main structure embedded steel ring, and bolts are reserved in the steel ring; the temporary sealing device is composed of a curtain rubber, a fan-shaped pressure plate, a gasket and bolts, the sealing device is connected and fixed to the steel sleeve by bolts, and grease is applied to the edge of the shield cutter head and the sealing device before the split starts.

[0023] The preferred technical solution of the present invention is as follows: in the step S5, two segments of the segment car are first lowered, and a small slag bucket is placed between the two segments of the segment car. The segment car and the slag bucket car are towed by a winch. After this section of excavation is completed, the two segments of the segment car are all lifted to the ground, and then a slag truck is lowered; the negative ring segments are standard ring segments, which are assembled with staggered seams; the cutter disc is started and rotated slowly when the cutter disc is about to contact the tunnel face; when the pressure of the shield propulsion jack changes significantly, the cutter disc speed is accelerated to 0.8-1.0 rpm; after the shield tail enters the steel sleeve, quick-setting slurry is injected through the grouting holes reserved outside the steel sleeve to quickly block the shield tail, and then excavation is continued, and synchronous grouting is resumed; if there is a large water or sand leakage in the tunnel portal seal, slurry is replenished through the spare grouting holes; after each ring of negative ring segments is released from the shield tail, the gap between the bracket, the bracket triangle support and the segment is wedged tightly with a square wood with a triangular edge, and the segment is tightened and clamped with a wire rope and a basket screw.

[0024] A better technical solution of the present invention: while the shield machine is assembled as a whole in step S8, the track arrangement spacing is adjusted in the order from the blocking wall to the tunnel portal, and the track center spacing is adjusted from the original four P43 rails of 640mm-970mm-640mm to a symmetrical arrangement of four P43 rails with a center spacing of 970mm-930mm-970mm.

[0025] The beneficial effects of the present invention are:

[0026] (1) The split start in the present invention is mainly used for shield starting in an ultra-short area with a length of 30-50m. After the shield machine bridge is installed in this area, there is no extra space to place the first trolley normally. Therefore, the first trolley is placed at the tail of the shield machine in an inclined state in the present invention, which solves the problem of no placement space for the first trolley. Since the hoisting port of the shield machine is blocked at the initial stage of shield starting, a temporary slag hoisting port is set away from the tunnel gate. After a period of time after the shield starts, the first trolley is placed at the tail of the shield machine. The upper half of the negative ring is removed, the hoisting shaft is opened, and improvements are made to the excavation track. Excavation can be carried out through the hoisting shaft, which increases the excavation speed, thereby increasing the excavation speed. The earth pressure balance shield split machine can achieve an average efficiency of 9-12m / day (6-8 rings) for the initial 100m of excavation. The excavation efficiency is basically the same as the conventional overall excavation efficiency, which greatly improves the excavation efficiency. The disassembled hoisting shaft can also normally hoist the remaining trolleys, avoiding the problem of increased costs caused by pipeline extension.

[0027] (2) The present invention sets a reinforcement structure for the negative ring after the upper half ring is removed. The reinforcement structure ensures the stability of the negative ring and provides a reverse thrust for the shield tunneling process together with the negative ring after the half ring is removed, thereby avoiding the removal of the negative ring from affecting the shield tunneling. Moreover, the special setting of the reinforcement structure will not affect the shield excavation.

[0028] (3) Before excavation, the present invention reinforces the starting end and sets a steel sleeve seal to ensure the stratum reinforcement effect of the split start, solves the problems of water and sand gushing and excessive ground settlement in the split start of the earth pressure balance shield in water-rich strata, selects excavation parameters matching the stratum, and adjusts the split start mode of the shield machine in stages under ultra-short space conditions, further improving the shield excavation speed.

[0029] The present invention solves the problems of water and sand gushing and excessive ground settlement occurring in the split starting of an earth pressure balance shield in water-rich strata by reinforcing the starting end; at the same time, the split starting mode of the shield machine is adjusted in stages under ultra-short space conditions, thereby improving the excavation efficiency, so that the excavation efficiency can reach the excavation efficiency of normal excavation; combined with its own excavation parameter control and the cooperation of the screw conveyor, the problem that the shield construction is difficult to excavate effectively and quickly when the length of the shield starting pit is much smaller than the overall size of the shield machine is solved, and the split starting rate can be close to the normal overall starting efficiency, thereby greatly improving the excavation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the layout of the lifting port and the temporary unearthing port of the starting well in the present invention;

[0031] Figure 2It is a schematic plan view of the split-start shield machine of the present invention starting to assemble the negative ring segments by empty pushing;

[0032] Figure 3 This is a schematic plan view of the negative ring assembly of the shield machine in the split starting 0-33m stage of the present invention after excavation and excavation;

[0033] Figure 4 This is a schematic diagram of the excavation plan after the No. 1 trolley is connected to the shield body in the split starting 33-67m stage of the present invention;

[0034] Figure 5-1 and Figure 5-2 The front and rear parts of the schematic diagram of the tunneling plane after the shield machine is connected as a whole when the split start is 100m;

[0035] Figure 6 It is the layout diagram of two sets of battery car tracks in the present invention;

[0036] Figure 7-1 It is a front structural schematic diagram of the split initial reaction frame in the present invention;

[0037] Figure 7-2 It is a side structural schematic diagram of the split initial reaction frame in the present invention;

[0038] Figure 7-3 It is a top view of the split initial reaction frame in the present invention;

[0039] Figure 8 This is a schematic diagram of the reinforcement structure of the starting shield shaft of the water-rich stratum shield tunnel of the present invention;

[0040] Fig. 9 for Figure 8 Middle AA section;

[0041] Fig.10 A schematic diagram of a steel sleeve sealing structure installed in a water-rich formation according to the present invention;

[0042] Fig.11 It is a longitudinal cross-sectional view of the steel sleeve sealing structure in the present invention;

[0043] Fig.12 It is a schematic diagram of the sequence of chiseling out the tunnel portal in the water-rich stratum according to the present invention;

[0044] Fig.13 This is a schematic diagram of the location of the observation hole of the tunnel portal in the water-rich stratum of the present invention;

[0045] Figure 14-1 to Figure 14-4 It is a schematic diagram of the assembly position of the F block of the tunnel negative ring segment in the present invention;

[0046] Fig.15 It is a cross-sectional schematic diagram of the tunnel negative ring segments after assembly in the present invention;

[0047] Fig.16 It is a schematic diagram of the structure of the originating bracket in the present invention;

[0048] Fig.17 It is a cross-sectional schematic diagram of the tunnel after the upper part of the negative ring of the present invention is removed;

[0049] Fig.18 It is a schematic diagram of the reinforcement structure after the upper part of the negative ring of the tunnel in the present invention is removed;

[0050] Fig.19 for Fig.18 The middle BB section of

[0051] Figure numerals: 1—Trolley No. 1, 2—Starting shaft, 201—Temporary slag lifting port, 202—Shield lifting port, 203—Temporary blocking wall, 204—Ground-connected wall, 205—Structural lining wall, 206—Concrete floor, 3—End reinforcement structure, 4—Reaction frame, 401—Reaction frame square steel column, 402—Reaction frame lifting ear, 403—Reaction frame upper beam, 404—Reaction frame lower beam, 405—Bolt interface, 406—Reaction frame back horizontal support, 407—Reaction frame back oblique support, 5—Steel sleeve, 501—Steel sleeve longitudinal rib, 502—Steel sleeve ring plate, 503—Reaction frame upper beam, 404—Reaction frame lower beam, 405—Bolt interface, 406—Reaction frame back horizontal support, 407—Reaction frame back oblique support, 5—Steel sleeve, 501—Steel sleeve longitudinal rib, 502—Steel sleeve ring plate, 503—Reaction frame upper beam, 404—Reaction frame lower beam, 405—Bolt interface, 406—Reaction frame back horizontal support, 407—Reaction frame back oblique support, 5 3—Steel sleeve grouting hole, 504—Steel sleeve bolt connection hole, 505—Steel sleeve embedded part, 506—Steel sleeve sealing rubber pad, 6—Trolley No. 2, 7—Trolley No. 3, 8—Trolley No. 4, 9—Trolley No. 5, 10—Negative ring segment, 1001—Segment F block, 11—Steel support, 12—Triangle support, 13—Starting bracket, 14-I-beam, 15—Horizontal steel support, 16—Extension pipeline, 17—Connecting bridge, 18—Shield body, 19—Trolley No. 6, 20—Shield excavation area, 21—Steel wire rope, 22—Horizontal observation hole, 23—Rail, 24—Slot steel sleeper. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] If the specific conditions are not specified in the examples of the present invention, the conditions are carried out according to the conventional conditions in the art or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments used in the examples of the present invention are not specified, they are all conventional products that can be purchased commercially.

[0054] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0055] The embodiment is for a certain shield construction project, in which the main structure of the station is the second underground floor, and the shield starting shaft enclosure structure at the station end is an underground continuous wall. The space of the starting shaft 2 is extremely short, and the net length from the tunnel portal to the temporary blocking wall 203 at the other end does not exceed 30 meters, which is much smaller than the at least 120m working shaft length required for the overall starting of a conventional subway shield machine. The outer diameter of the shield tunnel segment is 6000mm, the thickness of the segment is 300mm, the shield method is earth pressure balance type, the maximum excavation diameter is 6280mm, including the shield body (mainly cutter head, earth pressure balance chamber, main drive, thrust cylinder, segment assembly machine, screw conveyor, etc.), connecting bridge (mainly screw machine slag outlet, belt conveyor, segment crane), 6 sets of rear supporting trolleys, trolley No. 1 is mainly a synchronous grouting system, trolley No. 2 is mainly a hydraulic pump station, trolley No. 3 is mainly an electrical control cabinet and a low-voltage compensation cabinet, trolley No. 4 is mainly a box-type transformer, trolley No. 5 is mainly a cable reel, belt conveyor drive, belt conveyor slag discharge port, and trolley No. 6 is mainly a water pipe reel and a rail crane. The shield tunneling passes through mainly <3-4> medium-coarse sand layer, <3-6> pebble layer, <6-2> hard plastic residual soil and <8-1> fully weathered metamorphic sandstone; the starting point of the shield tunnel is located in a water-rich stratum, which is prone to water and sand gushing.

[0056] In the embodiment, Figure 1 As shown, square wellheads are reserved on the top plate and the middle plate of the starting well 2 as shield hoisting ports 202 for the assembly of the shield machine and the supporting trolleys, material hoisting, etc., and a temporary slag hoisting port 201 is set far away from the tunnel gate. Since the overall space length does not exceed 30 meters, the length of the shield hoisting port 202 is more than ten meters, and the remaining space can only construct a temporary excavation port of about 7 meters; the length of the temporary slag hoisting port 201 can only be used for temporary excavation, and cannot meet the requirements of normal excavation and excavation and trolley hoisting; in order to enable the shield to start normally, and no water and sand gushing will occur during the starting process, and the excavation rate and the shield excavation and excavation process will not be affected, the construction project uses a water-rich stratum ultra-short space earth pressure balance shield split starting method of the present invention, and the specific construction process of the shield split starting method is as follows:

[0057] Starting preparation stage (including determining the layout of the split starting equipment, carrying out shield shaft end reinforcement, tunnel door inspection, installation of starting bracket and reaction frame, assembly of shield machine down to the shaft, installation of steel sleeve and seal, and removal of tunnel door) - the first 0-33m trial excavation stage (such as Figure 2 and Figure 3 As shown in the figure, negative ring segment assembly, excavation and transportation arrangement, and the relocation of the No. 1 trolley) - the first 33-100 meters of excavation stage (as shown in the figure Figure 4 As shown, negative ring segment removal and support conversion, excavation and transportation layout adjustment) - normal excavation stage after 100 meters (as shown in Figures 5 and Figure 6 As shown, the shield machine was assembled as a whole and lowered into the well to start normal excavation).

[0058] The specific construction steps of the split-start method of the ultra-short space earth pressure balance shield in the water-rich stratum of this project are as follows:

[0059] S1. Determine the layout of the split starting equipment according to the construction site conditions. Since the total length of the shield body 18, the connecting bridge 17 and the No. 1 trolley 1 of the conventional 6280mm diameter earth pressure balance shield machine exceeds the total length of the starting shaft 2, in principle, the No. 1 trolley needs to be separated from the connecting bridge. Considering that the No. 1 trolley is provided with a synchronous grouting system, in order to ensure the normal activation of the grouting system during the excavation process, the present invention proposes to separate the shield equipment from the No. 1 trolley 1 and the No. 2 trolley 6; Figure 2 As shown, the tail of trolley No. 1 is tilted toward the other side of the station floor, the grease pump of trolley No. 2 6 is moved to trolley No. 1, and the driving wheel of the belt conveyor is temporarily modified to the rear of the connecting bridge 17. The connecting bridge 17 moves synchronously by installing a temporary bracket with rollers, and the rear of the connecting bridge 17 is used as a transportation channel. The shield machine is equipped with trolleys No. 2 to 5 and placed on the construction ground in sequence. Trolley No. 6 is temporarily cancelled and does not participate in the split start. Trolleys No. 2 to 5 are connected to the shield body 18, the connecting bridge 17, and trolley No. 1 through a temporarily extended connecting pipeline, which can meet the shield split start installation requirements under ultra-short space conditions.

[0060] S2. Before the construction of water-rich stratum splitting begins, if Figure 8 and Fig. 9As shown, the stratum at the end of the starting tunnel is effectively reinforced, the square area of ​​the end reinforcement is at least 10m×12m, the length of the reinforcement body is at least 10m from the portal along the tunnel excavation direction, the width is at least 6m on both sides along the tunnel centerline, and the reinforcement depth is at least 3m below the tunnel bottom; double-tube rotary jet piles are used for reinforcement of water-rich strata, and the slurry is cement and water glass double liquid slurry. The concentration of water glass is 35-40 degrees Baume, and the ratio of cement: water glass is 1:1. The rotary jet pile reinforcement adopts a plum blossom-shaped arrangement and interlocks with each other. The drilling starts from the side close to the starting end and gradually moves away from the end. Each row is constructed with skip holes at intervals. At the same time, a dewatering well is set in the reinforcement range for dewatering, so that the groundwater level at the reinforced end will be at least 1m below the tunnel bottom.

[0061] S4. Before the start of the shield tunneling, the tunnel portal reinforcement effect should be checked to check the strength, uniformity and permeability of the reinforcement. The inspection time should be two weeks after the end reinforcement is completed. Fig.13 As shown in the figure, 9 horizontal observation holes 22 are drilled at the edge of the tunnel portal. The diameter of each horizontal observation hole 22 is 42mm and the depth is 1.5m. Long wooden plugs are prepared before drilling to plug the leaks when water seepage is serious. By visually inspecting the water flow of the 9 horizontal observation holes 22, if the water flow is large and carries mud and sand, the ground needs to be re-grouted and reinforced, and the drilling position needs to be filled with long wooden plugs in time. In addition, the reinforcement body needs to be cored before starting. If the unconfined compressive strength of the core body reinforced by jet grouting is less than 1MPa, the unconfined compressive strength of the core body reinforced by sleeve valve pipe is less than 0.8MPa, and the permeability coefficient is greater than 1×10 -6 cm / s, and the water inflow of the horizontal exploration hole is greater than 5L / h·hole, and it also needs to be supplemented and reinforced.

[0062] S5. Before the shield machine goes down the shaft, the starting bracket must be installed. Fig.16 As shown, the starting bracket 13 can be installed by a gantry crane 7 days after the bottom plate is poured. The bracket adopts a finished steel structure, and the bracket is welded to the embedded steel plate of the station bottom plate; before installation, the elevation and plane position of the starting bracket must be accurately located according to the measurement control points to ensure that the axis of the starting bracket and the reaction frame coincide with the normal line of the tunnel portal; after the bracket is positioned, the left and right sides of the bracket are connected to the embedded steel plates of the structural side walls and the bottom longitudinal beams through the top of the steel section; when the shield machine mainframe is assembled, hard lubricating oil is applied to the starting bracket track to reduce the resistance of the shield machine to start and move forward.

[0063] S6. The reaction frame provides the reaction force required for the shield machine to advance. The reaction frame must have sufficient rigidity and strength, such as Figure 7-1 to Figure 7-3The reaction frame is supported on the bottom plate and side walls. The longitudinal positioning of the reaction frame must ensure that the position of the pouring tunnel door meets the requirements after the negative first ring reinforced concrete segments are removed, and the horizontal positioning must ensure that the thrust of the shield machine transmitted by the negative ring segments accurately acts on the reaction frame. After the reaction frame base is connected to the lower beam on the ground, it is hoisted into the well as a whole and welded to the embedded steel plate on the bottom plate. After the shield machine is assembled in the well, the reaction frame columns and upper beams are installed in place. At the same time, two diagonal braces are set on the back of the reaction frame and welded to the embedded steel plate on the bottom plate.

[0064] S7. One week before the start of the shield machine, the tunnel portal is chiseled out for the first time. First, the concrete of the tunnel portal enclosure structure is squeezed and cracked by static blasting. Then, the broken concrete is chiseled out by a jackhammer. The inner layer of steel bars of the ground-connected wall is removed, and the outer layer of steel bars and concrete protective layer of the continuous wall are retained. Fig.12 As shown, the first chiseling should be done in the order of first bottom then top, first middle then sides. The second chiseling should be done one day before the shield machine advances, when the outer layer of reinforced concrete is chiseled out and the outer steel bars are cut off, and concrete is quickly sprayed to seal the entire face, so as to shorten the exposure time of the tunnel portal soil as much as possible.

[0065] S8. To prevent water and sand gushing during initial excavation, a sealing steel sleeve 5 is installed before excavation in water-rich strata. A 900mm long steel sleeve is added outside the main structure of the tunnel portal. Fig.10 and Fig.11 As shown, a rubber plate water stop is set between the steel sleeve 5 and the embedded steel ring of the main structure of the tunnel portal. The circumferential wing plate width of the embedded steel ring of the tunnel portal is 300mm, and the reserved bolt hole diameter is 22mm. The steel sleeve is divided into four pieces A, B, C, and D for on-site assembly. The axis of the steel sleeve must be in the same straight line with the axis of the tunnel portal. At the same time, in order to prevent the loss of soil, groundwater, and grouting slurry from the gap between the shield shell and the steel sleeve when the shield starts to advance, a temporary sealing device is installed on the side of the steel sleeve close to the shield machine. The temporary sealing device is composed of a curtain rubber, a fan-shaped pressure plate, a gasket, and bolts. The sealing device is connected and fixed to the steel sleeve by bolts. Grease is applied to the edge of the shield cutter head and the sealing device before the split starts to prevent the cutter head from damaging the tunnel portal sealing device.

[0066] After the initial preparation work is completed, shield tunneling begins. The first 0-33 meters trial tunneling stage specifically includes the following steps:

[0067] S9. Negative ring assembly and excavation: After the commissioning of the shield split equipment is completed, the negative ring is assembled using an assembling machine. First, two segments of the segment car are lowered. When assembling the negative 7 ring to the negative 5 ring, a forklift is used to transport the segments from the side of the connecting bridge. The shield machine does not need to excavate before the negative 5 ring is 1 meter out of the shield tail. At this time, the excavation is stopped, and a ring of segments is pre-stored on the segment car with a forklift. Then, during the excavation and excavation to the first 6m, the excavation port is modified from the rear of the connecting bridge. A 3.0m*1.5m*2.0m small soil bucket is used for excavation. The small soil bucket is placed in the middle of the two segments, and the segment car and the soil bucket car are towed by a 10T forklift. After this section is completed, both segments are hoisted to the ground, and then a soil truck is lowered.

[0068] S10. The negative ring segment is a standard ring segment, with a thickness of 300mm, an inner diameter of 5400mm, and an outer diameter of 6000mm. There are 7 negative ring segments, which are assembled with staggered seams. The negative 7 rings are assembled first with the lower segment. The first block is installed with the B2 block. A baffle is welded on the left side of the B2 block to position the segment. Then the segments are installed in the order of B2-B1-L1-B3-L2-F. When assembling the upper segment, L1, L2, and B3 should be fixed to the upper part of the shield tail with an L-shaped steel plate so that they cannot move up, down, left, or right after being stressed, so as to facilitate the assembly of the F block. The assembly points of the F blocks from the negative 7 ring to the negative 1 ring are 1 point (such as Figure 14-1 ), 8 o'clock (such as Figure 14-3 ), 11 o'clock (such as Figure 14-4 ), 4 points (such as Figure 14-2 ), 8 o'clock (such as Figure 14-3 ), 4 points (such as Figure 14-2 ), 11 o'clock (such as Figure 14-4 ), 1 point (such as Figure 14-1 ). After assembly, cut off the steel plate and use the thrust cylinder to push the negative 7 ring evenly until the segment is exposed 50mm from the shield tail. Use a 200mm high triangular steel wedge to adjust and insert it into the gap between the segment and the support rail. After tightening, weld the steel wedge to the starting bracket support rail, one on each side. Then push the negative 7 ring to the reference ring and connect it firmly. At the same time, weld a stopper on the outside of the reference ring to prevent the negative 7 ring from expanding outward. Then assemble the other negative rings. After each negative ring segment ring is out of the shield tail, insert a 200mm high triangular wooden wedge into the gap between the bracket, the bracket triangle support and the segment, one on each side of the starting base.

[0069] S11. Start the cutterhead when it is about to contact the face and rotate it slowly; when the pressure of the shield thrust jack changes obviously, speed up the cutterhead to 0.8-1.0rpm. After the shield tail enters the steel sleeve, quick-setting slurry is injected through the reserved grouting holes outside the steel sleeve to quickly seal the shield tail, and then continue to excavate and resume synchronous grouting. If there is a large water or sand leakage in the tunnel door seal, slurry is added again through the spare grouting holes. After the negative ring segment is out of the shield tail, the gap between the bracket, the bracket triangle support and the segment is wedged with a square wood with a triangular edge, and the segment is tightened with a steel wire rope and a 40mm diameter basket screw to prevent the segment from losing roundness.

[0070] When the split excavation starts, the following parameters are controlled:

[0071] (1) Earth pressure setting. The starting section adopts the earth pressure mode for excavation, and the earth bin pressure is about 10% greater than the front water and soil pressure, that is, the initial setting value of the earth bin pressure is 1.43kg / cm 2 , during construction, appropriate adjustments should be made according to other construction parameters and ground settlement monitoring data. As the tunnel depth and soil pressure change, the soil pressure setting value should be calculated every 10 rings of excavation. When the soil pressure increases, first turn off the screw conveyor and stop mucking. At the same time, observe the changes in soil pressure in the soil bin through the pressure sensor. When the soil pressure in the soil bin reaches the set value of the soil pressure, turn on the screw conveyor and adjust the excavation speed of the screw conveyor according to the changes in soil pressure reflected by the pressure sensor until the soil pressure remains unchanged at the set value of the soil pressure.

[0072] (2) Control of the mucking volume. Due to the special structure of the shield machine, it is impossible to directly observe the tunnel face conditions. The stability of the tunnel face can be estimated by the amount of mucking. If the mucking volume is too large, the tunnel face may collapse. If the mucking volume is too small, the tunnel face may have cavities or cracks. The mucking volume must be controlled. The loose coefficient of the soil is considered to be 1.3 to 1.5. The mucking volume per cycle = π / 4×D2×L×k=3.14 / 4×6.282×1.5×(1.3 to 1.5)=60.4m 3 ~69.7m 3 The amount of mucking produced by the shield machine in each excavation cycle should be controlled between the above values. The amount of mucking produced varies due to the different properties of the soil layer. If it exceeds this range, the cause should be found out. If necessary, the machine should be stopped immediately to find out the cause and take corresponding measures.

[0073] (3) Excavation speed. During trial excavation, the excavation speed in the first 30 meters should not be too high and should be controlled within 2-30 mm / min. Especially within the end reinforcement range, the speed should be adjusted at any time according to the surface monitoring situation. The cutter head speed in the reinforcement body of the starting section is controlled at 0.5-1.0 rpm. Before the shield tail enters the tunnel, the total thrust of the shield is controlled within 800 tons, and then the thrust of the shield is gradually increased, but it must be controlled within 1200 tons.

[0074] (4) Synchronous grouting and secondary grouting. The grouting material is selected according to different grouting methods and grouting locations. The grouting slurry for synchronous grouting can be cement mortar, with an initial setting time of about 8 hours and a compressive strength greater than 1.0Mpa. Secondary grouting uses a separate grouting pump for manual grouting. Grouting adopts a method of pressure control as the main method and grouting volume control as the auxiliary method. The grouting pressure is about 20% greater than the groundwater pressure, that is, the pressure at the grouting port of the starting section is controlled at 1.5-2.0Kg / cm 2 The shield machine axis shall not deviate from the design axis by more than ±50 mm, and the ground settlement shall be controlled within +10 mm to -30 mm.

[0075] The first 33-100 meters of excavation phase specifically includes the following steps:

[0076] S12. After 33 meters of excavation, if Figure 4 , put the No.1 trolley in the right position and connect it to the connecting bridge, move the belt conveyor to the rear of the No.1 trolley, move the grease pump on the connecting bridge to the No.1 trolley, and transport the pipe segments and excavate from the rear of the No.1 trolley. Use a slag truck to transport the pipe segments and excavate, and wait until the rear of the No.1 trolley is completely in the tunnel. Figures 17 to 19 As shown, the upper half of the negative ring segments are removed, and at the same time, a steel support 11 with a top diameter of 800mm is used to replace the upper part of the negative ring to transmit force, so as to realize the lowering of the segments and excavation from the shield lifting port. At this time, an electric vehicle is formed, which consists of 2 muck trucks, 1 mortar truck and 1 engine head, with a total length of 27.6 meters. The arrangement order is muck truck-muck truck-mortar truck-engine head.

[0077] S13. After excavating 67m, the pipe segments are excavated and installed from the rear of the No. 1 trolley. When installing the pipe segments, the slag bucket is placed on the ground, and the pipe segments are lowered from the lifting port by a gantry crane to the dump truck without a slag bucket. After the pipe segments are installed, the gantry crane is used to lift the slag bucket onto the dump truck.

[0078] S14. After 100 meters of trial excavation, construction was suspended, the previously temporarily extended pipeline was dismantled, and the No. 2-No. 6 trolleys were lowered into the well in sequence to be assembled with the shield, connecting bridge and No. 1 trolley. After the overall assembly and debugging, normal excavation was resumed. Figure 6 As shown, a switch is installed and two trains of electric cars are formed. The marshaling order of No. 1 electric car is muck truck-muck truck-muck truck-locomotive, with a total length of 29 meters. The marshaling order of No. 2 electric car is segment truck-segment truck-mortar truck-muck truck-locomotive, with a total length of 29.1 meters.

[0079] S15. While the shield machine is being assembled as a whole, the track spacing is adjusted in the order from the blocking wall to the tunnel portal. The track center spacing is adjusted from the original four P43 rails of 640mm-970mm-640mm to four P43 rails with a center spacing of 970mm-930mm-970mm, which are arranged symmetrically. The reaction frame is replaced with a 3400mm long sleeper within 18.5m to the left of the zero ring, and the turnout is installed on the sleeper within 18.5m to the left of the zero ring. The four P43 rails between the turnout and the blocking wall are arranged symmetrically, with a sleeper spacing of 1500mm, and the downhill section is 21 meters.

[0080] The method for split starting of an earth pressure balance shield in an ultra-short space in a water-rich stratum in the embodiment can solve the problems of water and sand gushing and excessive ground settlement occurring in the split starting of an earth pressure balance shield in a water-rich stratum by processing aspects such as end reinforcement, steel sleeve sealing, starting grouting, negative ring support conversion, and excavation speed control. At the same time, the split starting mode of the shield machine is adjusted in stages under ultra-short space conditions, which can smoothly solve the problem that the shield construction is difficult to effectively and quickly advance when the length of the shield starting pit is much smaller than the overall size of the shield machine. The split starting rate can be close to the normal overall starting efficiency, thereby greatly improving the excavation efficiency.

[0081] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for launching a split earth pressure balance shield in an ultra-short space in a water-rich stratum, characterized by: The shield starting method is suitable for earth pressure balance shields with a starting space length of 30 to 50 m and a water-rich stratum at the starting end. Shield hoisting ports are reserved on the top plate and middle plate of the starting shaft, and a temporary slag hoisting port is set at the end away from the tunnel entrance. The specific construction steps of the starting method are as follows: S1. Determine the layout of the split starting equipment. The shield starting includes six sets of supporting trolleys, of which five sets of trolleys participate in the shield starting; separate the shield equipment between trolley No. 1 and trolley No. 2, and tilt the tail of trolley No. 1 toward the other side of the station floor. Move the grease pump of trolley No. 2 to trolley No. 1, and temporarily modify the driving wheel of the belt conveyor to the rear of the connecting bridge. The connecting bridge moves synchronously by installing a temporary bracket with rollers; the supporting trolleys No. 2 to No. 5 behind the shield machine are placed on the construction ground in sequence, and trolleys No. 2 to No. 5 are connected to the shield body, the connecting bridge, and trolley No. 1 through a temporarily extended connecting pipeline; S2. Effectively reinforce the strata at the left and right ends of the starting tunnel. Double-tube jet grouting piles are used to reinforce water-rich strata. The slurry is cement and water glass double slurry with a concentration of 35-40 degrees Baume. Drainage wells are set up within the reinforcement range to reduce the groundwater level at the reinforced end to at least 1m below the bottom of the tunnel. Two weeks after the end is reinforced, the reinforcement effect of the tunnel portal is checked. S3. The starting bracket is hoisted and installed in the well. The starting bracket is fixed on the station floor. After the bracket is positioned, the left and right sides are connected to the structural side wall and the bottom longitudinal beam pre-embedded steel plate through the horizontal steel. After the starting bracket is installed, the reaction frame and shield machine are hoisted and installed in the well. The axis of the starting bracket and the reaction frame coincides with the normal line of the tunnel gate. S4. One week before the start of the shield machine, the tunnel portal is chiseled out for the first time. The concrete of the tunnel portal enclosure structure is first squeezed and cracked by static blasting, and then the broken concrete is chiseled out by a jackhammer. The inner layer of steel bars of the ground-connected wall is removed, and the outer layer of steel bars and the concrete protective layer of the continuous wall are retained. The outer layer of reinforced concrete is chiseled out one day before the shield machine is advanced, and the outer layer of steel bars is removed, and concrete is quickly sprayed to seal the entire face. Before the shield machine is driven, a sealing steel sleeve is installed outside the main structure of the tunnel portal, and a temporary sealing device is installed on the side of the steel sleeve close to the shield machine. The axis of the steel sleeve is in the same straight line as the axis of the tunnel portal. S5. The first 0-33 meters trial excavation stage: After the shield split equipment is debugged, the negative ring is assembled using an assembling machine. In this stage, a small slag bucket is used to excavate the slag from the temporary slag lifting port behind the connecting bridge. S6. After excavating 33 meters, trolley No. 1 is aligned and connected to the connecting bridge, the belt conveyor is moved to the rear of trolley No. 1, the grease pump on the connecting bridge is moved to trolley No. 1, and the segments are transported and excavated from the rear of trolley No. 1; the segments are transported and excavated by muck trucks, and after the rear of trolley No. 1 has completely entered the tunnel, the upper half of the segments from negative ring 1 to negative ring 7 are removed, and steel supports are used to replace the upper part of the negative ring for force transmission, so that the segments can be unloaded and excavated from the shield hoisting port; S7. After excavating 67m, the pipe segments are unearthed and installed from the rear of the No. 1 trolley. When installing the pipe segments, the slag bucket is placed on the ground, and the pipe segments are lowered from the lifting port to the muck truck without a slag bucket. After the pipe segments are installed, the slag bucket is lifted to the muck truck by the gantry crane; S8. After 100 meters of excavation, construction will be suspended, the previously temporarily extended pipeline will be dismantled, and the No. 2 to No. 6 trolleys will be lowered into the well in sequence to be assembled with the shield, connecting bridge and No. 1 trolley. After the overall assembly and commissioning, normal excavation will be resumed; After the completion of this section, the lower switch will be installed and two trains of electric cars will be formed to transport the slag at the same time.

2. The method for launching a split earth pressure balance shield in an ultra-short space in a water-rich stratum according to claim 1 is characterized by: The shield tunneling starts in the earth pressure mode, and the soil bin pressure is 8% to 12% greater than the front water and soil pressure, that is, the initial setting value of the soil bin pressure is 1.43 kg / cm 2 When the soil pressure increases, first turn off the screw conveyor and stop discharging the soil. At the same time, observe the changes in the soil pressure in the soil bin through the pressure sensor. When the soil pressure in the soil bin reaches the set value of the soil pressure, turn on the screw conveyor and adjust the discharging speed of the screw conveyor according to the changes in the soil pressure reflected by the pressure sensor until the soil pressure remains unchanged at the set value of the soil pressure.

3. A method for launching a split earth pressure balance shield in an ultra-short space in a water-rich stratum according to claim 1 or 2, characterized in that: The looseness coefficient of the shield starting section soil is set to 1.3-1.5, and the amount of mucking per cycle is controlled at 60.4m 3 ~69.7m 3 The excavation speed of the shield machine in the initial 0-33m trial excavation stage is preferably controlled at 2-30mm / min, the cutter head speed in the reinforced body in the initial section is controlled at 0.5-1.0rpm, and the total thrust of the shield machine is controlled within 800T before the shield tail enters the tunnel gate. Subsequently, the thrust of the shield machine is gradually increased, and the maximum thrust is controlled within 1200T.

4. A method for launching a split earth pressure balance shield in an ultra-short space in a water-rich stratum according to claim 1 or 2, characterized in that: The slurry for synchronous grouting during the shield starting process is cement mortar, with an initial setting time of 7 to 9 hours and a compressive strength greater than 1.0 MPa; the secondary grouting is manually operated by a separate grouting pump, and the grouting adopts a method of pressure control as the main and grouting volume control as the auxiliary. The grouting pressure is 18% to 22% greater than the groundwater pressure, that is, the pressure at the grouting port of the starting section is controlled at 1.5 to 2.0 Kg / cm 2 , control the ground settlement within +10㎜~-30㎜.

5. A method for launching a split earth pressure balance shield in an ultra-short space in a water-rich stratum according to claim 1 or 2, characterized in that: In the step S1, trolley No. 1 is the synchronous grouting system, trolley No. 2 is mainly a hydraulic pump station, trolley No. 3 is an electrical control cabinet and a low-voltage compensation cabinet, trolley No. 4 is a box-type transformer, trolley No. 5 is a cable drum, belt conveyor drive, and belt conveyor slag discharge port, and trolley No. 6 is mainly a water pipe drum and a rail crane.

6. A method for launching a split earth pressure balance shield in an ultra-short space in a water-rich stratum according to claim 1 or 2, characterized in that: In the step S2, the ratio of cement to water glass is 1:1, the jet grouting piles are arranged in a plum blossom shape and interlock with each other, the drilling starts from the side close to the starting end and gradually moves away from the end, each row is constructed with skip holes, and a dewatering well is set in the reinforcement range for dewatering; the inspection of the portal reinforcement effect includes the inspection of the strength, uniformity and permeability of the reinforcement body, specifically, 9 horizontal holes are evenly drilled at the edge of the tunnel portal, long wooden plugs are prepared before drilling the holes to prepare for plugging when water seepage is serious, and the water flow of the 9 holes is visually inspected. If the water output is large and brings out mud and sand, the ground needs to be re-grouted for reinforcement, and the drilling position needs to be filled with long wooden plugs in time; in addition, the reinforcement body needs to be cored before starting.

7. A method for launching a split earth pressure balance shield in an ultra-short space in a water-rich stratum according to claim 1 or 2, characterized in that: In the S3 step, the starting bracket is installed by a gantry crane 7 days after the bottom plate is cast. The starting bracket adopts a finished steel structure, and the starting bracket is welded to the embedded steel plate of the station bottom plate; the elevation and plane position of the starting bracket are accurately located according to the measurement control points before installation; when the shield machine main engine is assembled, hard lubricating oil is applied to the track of the starting bracket; the longitudinal positioning of the reaction frame ensures that the position of the casting tunnel door meets the requirements after the negative 1 ring reinforced concrete segment is removed, and the lateral positioning ensures that the thrust of the shield machine transmitted by the negative ring segment acts accurately on the reaction frame; after the base of the reaction frame is connected to the lower crossbeam on the ground, it is hoisted into the well as a whole and welded to the embedded steel plate of the base on the bottom plate. After the shield machine is assembled in the well, the columns and upper crossbeam of the reaction frame are installed in place, and the diagonal brace is installed behind the reaction frame, and the diagonal brace is welded to the embedded steel plate on the bottom plate.

8. A method for launching a split earth pressure balance shield in an ultra-short space in a water-rich stratum according to claim 1 or 2, characterized in that: When chiseling for the first time in step S4, chisel in the order of first bottom then top, first middle then sides; the steel sleeve in step S4 is 800mm to 1000mm long, and a rubber sheet water stop and a tunnel portal embedded steel ring are arranged between the steel sleeve and the tunnel portal main structure embedded steel ring, and bolts are reserved in the steel ring; the temporary sealing device is composed of curtain rubber, fan-shaped pressure plate, gasket and bolts, and the sealing device is connected and fixed to the steel sleeve by bolts, and grease is applied to the edge of the shield cutter head and the sealing device before the split starts.

9. A method for launching a split earth pressure balance shield in an ultra-short space in a water-rich stratum according to claim 1 or 2, characterized in that: In the step S5, two segments of the segment car are first lowered, and a small soil bucket is placed between the two segments of the segment car. The segment car and the soil bucket car are towed by a winch. After this section of excavation is completed, the two segments of the segment car are all lifted to the ground, and then a soil truck is lowered; the negative ring segment is a standard ring segment, which is assembled by staggered seams; the cutter head is started and rotated slowly when the cutter head is about to contact the tunnel face; when the pressure of the shield propulsion jack changes significantly, the cutter head speed is accelerated to 0.8-1.0 rpm; after the shield tail enters the steel sleeve, quick-setting slurry is injected through the reserved grouting holes outside the steel sleeve to quickly block the shield tail, and then excavation is continued, and synchronous grouting is resumed; if there is a large water or sand leakage in the tunnel gate seal, slurry is replenished again through the spare grouting holes; after each ring of negative ring segments is out of the shield tail, the gap between the bracket, the bracket triangle support and the segment is wedged tightly with a square wood with a triangular edge, and the segment is tightened and clamped with a wire rope and a basket screw.

10. A method for launching a split earth pressure balance shield in an ultra-short space in a water-rich stratum according to claim 1 or 2, characterized in that: While the shield machine is being assembled as a whole in step S8, the track arrangement spacing is adjusted in the order from the blocking wall to the tunnel portal, and the track center spacing is adjusted from the original four P43 tracks of 640mm-970mm-640mm to a symmetrical arrangement of four P43 tracks with center spacings of 970mm-930mm-970mm.

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