CN107916935A - A kind of soil body composite reinforcing structure and construction method of the existing subway of weak soil shield crossing - Google Patents

Abstract

The invention relates to a soil composite reinforcement structure for a soft soil shield passing through an existing subway, comprising: a shield tunnel outline, an angle-adjustable pipe shed and a horizontal rotary grouting pile; There is a row of adjustable-angle pipe sheds, the adjustable-angle pipe sheds include pipe shed steel pipes, and horizontal jet grouting piles are arranged between the adjacent pipe shed steel pipes, and the horizontal jet grouting piles wrap the adjustable-angle pipe sheds The horizontal jet grouting piles are overlapped with the adjacent horizontal jet grouting piles; the horizontal jet jetting piles include jetting drill pipes and drill pipe casings, and the pipe shed steel pipes are connected alternately with the jet jetting drilling pipes. The beneficial effects of the present invention are: the present invention uses the adjustable angle pipe shed and the horizontal rotary spraying in combination, combining rigidity and softness, both soft and hard, not only giving full play to their respective characteristics, but also working well together, and achieving good overall support It can well adapt to the environment of soft soil areas, strengthen the soil, and can well control the deformation of the existing subway.

Description

A Soil Composite Reinforcement Structure and Construction Method for Soft Soil Shield Crossing Existing Subway

technical field

The invention relates to the field of soil compound reinforcement construction in which a shield machine passes through an existing subway in a soft soil area, in particular to a soil compound reinforcement structure and a construction method for a shield machine to pass through an existing subway in a soft soil area.

Background technique

With the continuous advancement of the urbanization process, urban underground rail transit is becoming more and more important. To build a complete subway network, there must be intersections of subway lines. In shield construction of subway tunnels, the number of new shield tunnels crossing existing subway tunnels is increasing day by day. Newly built shield tunnels will have many adverse effects on existing subway tunnels, such as segment cracking, joint opening, bolt failure, uneven longitudinal settlement, and excessive horizontal displacement, especially in existing tunnels in soft soil areas. Deformation and segment damage will affect the comfort and smoothness of the locomotive running, aggravate the wear and tear of the train, and seriously cause major accidents such as locomotive derailment. Therefore, before crossing, it is necessary to reinforce the soil within the scope of the existing subway to strengthen the ability of the existing subway to resist deformation and ensure the normal operation of the existing subway.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a soil composite reinforcement structure and construction method for soft soil shield tunneling through the existing subway.

Another object of the present invention is to provide a soil composite reinforcement structure for soft soil shield tunneling through existing subways. The purpose of the present invention is achieved through the following technical solutions:

This kind of soft soil shield crosses the soil composite reinforcement structure of the existing subway, including: the outline of the shield tunnel, the adjustable angle pipe shed and the horizontal jet grouting pile; Adjustable angle pipe shed, said adjustable angle pipe shed includes pipe shed steel pipes, horizontal jet spray piles are arranged between said adjacent pipe shed steel pipes, said horizontal jet spray piles wrap the adjustable angle pipe sheds and The adjacent horizontal jet grouting piles are occluded and overlapped; the horizontal jet grouting piles include jet grouting drill pipes and drill pipe jackets, the pipe shed steel pipes are connected alternately with the jet grouting drill pipes, and the outer side of the pipe shed steel pipes is provided with a limit track, the outer surface of the jet-jet drill pipe is provided with a drill pipe jacket, and the limit rail and the drill pipe jacket form an integral arch shell through limit welding.

As a preference: the angle-adjustable pipe shed is divided into multiple sections from back to front along the longitudinal extension direction of the tunnel.

As a preference: the pipe shed steel pipe is made of hot-rolled seamless steel pipe, and both ends of the pipe shed steel pipe are pre-processed into external threaded buckles.

As a preference: through the center of the shield tunnel to make two tangents of the existing subway tunnel, the angle between the two tangents is α, and the angle formed by the center of the shield tunnel and the two edges of the adjustable angle pipe shed 8 is β, β = 2α.

A construction method for a soft soil shield passing through an existing subway soil composite reinforcement structure, comprising the following steps:

S1. Spiral unearthed adjustable angle pipe shed arch support;

S1.1. Set up a drilling platform and a shared platform for horizontal rotary spraying construction;

S1.2. Install the drilling rig. After the construction of the adjustable angle pipe shed is completed, the drilling rig continues to carry out the horizontal rotary spraying construction;

S1.3. Remove the plain concrete obstacles on the tunnel surface and the entrance section of the formation: the structural wall of the tunnel surface uses high-speed water drilling to drill holes according to the design position, and the opening angle is drilled according to the design and construction angle of the adjustable angle pipe shed; the submerged hole is used The hammer drills into the plain concrete barrier at the entrance section of the broken formation along the face opening;

S1.4. Insert the auger unearthed drilling tool into the processed pipe shed steel pipe, male and female threaded fasteners at both ends of the pipe shed steel pipe, install a reaming auger wedge drill bit at the end of the auger drilling tool, and install an angle detection instrument inside the drilling tool;

S1.5. Check the mechanical condition of the drilling rig and the working status of the instrument before jacking the steel pipe in the pipe shed; when the rig is in place for drilling, the rig is fixed to the face of the operation; after the steel pipe in the pipe shed is jacked into the soil layer, start the rig to rotate and measure the pipe shed into the soil Steel pipe angle change;

S1.6. After the jacking of the first pipe shed steel pipe is completed, disassemble the drilling rig and the angle-adjustable pipe shed joint, return to the original position along the guide rail, manually install the second pipe shed steel pipe, install the auger in the pipe shed steel pipe, and The first pipe shed steel pipe is buckled and connected into one, jacking and rotating to unearth;

S1.7. When the inclination deviation occurs in the angle of the steel pipe in the pipe shed, start the deviation correction program, stop the rotation of the drilling tool, and operate the jacking of the steel pipe in the pipe shed according to the design method: the steel pipe in the pipe shed deviates upwards, reduce the inclination of the steel pipe in the shed, and adjust the auger downward The angle position of the wedge drill bit; the downward deviation of the pipe shed steel pipe, adjust the inclination angle of the pipe shed steel pipe upward, and adjust the angle position of the auger wedge drill bit upward; The steel pipe of the pipe shed is corrected;

S1.8. The steel pipes under construction must be numbered hole by hole and root by root before installation, and the pipes are jacked in the order of numbering;

S1.9, Adjustable angle pipe shed grouting: check the pipeline and mechanical conditions before grouting, do a grouting test after confirming that it is normal, and determine reasonable grouting parameters; check the orifice, adjacent holes, Whether there is grouting in the thinner part of the covering layer; send a special person to be responsible for the grouting process, record the grouting time, grout consumption and grouting pressure and other data; after the grouting, clean the pump and pipeline to complete the adjustable angle The construction technology of the pipe shed;

S2, horizontal jet grouting soil reinforcement and improvement;

S2.1. Install the rotary spray drilling tool and the limit rail;

S2.2. Drilling: opening holes, preparing circulating slurry, and drilling;

S2.3. High-pressure rotary grouting: Check the high-pressure grouting pump, and start grouting when the pump pressure meets the design requirements; check the sealing of the drilling rig before grouting, and spray grouting after the pressure reaches the design value; arrange special personnel to operate the high-pressure grouting and observe the change of pump pressure; the drill pipe is sprayed to the design end hole position to stop grouting, and the pipeline is washed with clean water under high pressure;

S2.4. Hole sealing: After spraying grout to the designed final hole position, stop spraying, pull out the drill pipe and drill bit, and use woven bags or cotton silk to seal the hole;

S2.5. Clean the pipeline and equipment, and complete the construction process of horizontal rotary spraying.

The beneficial effects of the present invention are: the present invention uses the adjustable angle pipe shed and the horizontal rotary spraying in combination, combining rigidity and softness, both soft and hard, not only giving full play to their respective characteristics, but also working well together, and achieving good overall support It can well adapt to the environment of soft soil areas, strengthen the soil, and can well control the deformation of the existing subway.

Description of drawings

Fig. 1 is the construction process flow chart of spiral unearthed adjustable angle pipe shed;

Figure 2 is a flow chart of the horizontal rotary spraying construction process;

Figure 3 is a plan view of Hangzhou Metro Line 2 passing through Line 1;

Figure 4 is a construction layout diagram of the adjustable angle pipe shed;

Figure 5 is a layout diagram of the horizontal jet grouting pile and the adjustable angle pipe shed;

Fig. 6 is a schematic diagram of the direction of the wedge-shaped drill bit when the steel pipe deviates upward;

Fig. 7 is a schematic diagram of the direction of the wedge-shaped drill bit when the steel pipe is deflected downward;

Figure 8 is a schematic diagram of the position of the wedge-shaped drill bit when the angle of the steel pipe is normal;

Fig. 9 is a construction layout diagram of horizontal rotary spraying;

Explanation of Reference Signs: Downlink Line 1 of Hangzhou Metro Line 2, Uplink Line 2 of Hangzhou Metro Line 2, Uplink Line 3 of Hangzhou Metro Line 1, Downlink Line 4 of Hangzhou Metro Line 1, Fengqi Road Station of Hangzhou Metro Line 2 5. Fengqi Road Station of Hangzhou Metro Line 1 6. Shield tunnel outline 7. Angle-adjustable pipe shed 8. Horizontal rotary grouting pile 9. Face 10. Spiral drill wedge bit 11. Pipe shed steel pipe 12. Position welding 13, rotary spraying drill pipe 14, drill pipe jacket 15, limit rail 16.

Detailed ways

The present invention will be further described below in conjunction with the examples. The description of the following examples is provided only to aid the understanding of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

As shown in Figures 1 to 9, the soft soil shield passing through the soil composite reinforcement structure of the existing subway can effectively control the settlement and segment damage of the existing subway, thereby enabling the shield to advance smoothly. The soil composite reinforcement structure of the soft soil shield passing through the existing subway includes: Hangzhou Metro Line 2 Down Line 1, Hangzhou Metro Line 2 Up Line 2, Hangzhou Metro Line 1 Up Line 3, Hangzhou Metro Line 1 Downline 4, Hangzhou Metro Line 2 Fengqi Road Station 5, Hangzhou Metro Line 1 Fengqi Road Station 6, shield tunnel contour line 7, angle-adjustable pipe shed 8, horizontal jet spray pile 9, tunnel face 10 , Spiral drill wedge-shaped drill bit 11, pipe shed steel pipe 12, limit welding 13, rotary spraying drill pipe 14, drill pipe jacket 15 and limit track 16.

As shown in Figure 3, the downlink 1 of Hangzhou Metro Line 2 at Fengqi Road Station 5 of Hangzhou Metro Line 2 and the uplink 2 of Hangzhou Metro Line 2 pass through Fengqi Road Station 6 of Hangzhou Metro Line 1. Line 3 of Hangzhou Metro Line 1 and Line 4 of Hangzhou Metro Line 1. As shown in Figure 4, in the new shield tunnel No. 2 line passing under the existing subway tunnel No. 1 line, a row of advanced support adjustable angle pipe sheds 8 is set outside the contour line 7 of the shield tunnel to be excavated. Along the longitudinal extension direction of the tunnel, it is divided into multiple sections from the back to the front to carry out the adjustable angle pipe shed 8 advance support construction for the shield tunneling through the existing subway soil, and the adjustable angle pipe shed 8 advance support construction of multiple sections The methods are the same. As shown in Figures 5 and 9, the adjustable-angle pipe shed 8 includes pipe shed steel pipes 12, and horizontal jet grouting piles 9 are arranged between said adjacent pipe shed steel pipes 12, and said horizontal jet grouting piles 9 will be adjustable The angled pipe shed 8 is wrapped and overlapped with the adjacent horizontal jet grouting pile 9 to form a support structure with high load bearing and curtain partition effect, and jointly bear the external load. The distance between adjacent horizontal jet grouting piles 9 is 300mm, the adjacent horizontal jet grouting piles 9 interlock each other by 200mm, the diameter of horizontal jet grouting piles 9 is 500mm, and the single construction length is 45m. As shown in Figure 9, the horizontal jet grouting pile 9 includes a jet grouting drill pipe 14 and a drill pipe jacket 15. There is a limiting track 16, and the outer surface of the jet-jet drill pipe 14 is provided with a drill pipe jacket 15, and the limiting rail 16 and the drill pipe jacket 15 form an integral arch shell through limiting welding 13. The pipe shed steel pipe 12 is made of hot-rolled seamless steel pipe with an outer diameter of 159mm and a wall thickness of 8mm. The length of each steel pipe is 6m, and both ends are pre-processed into outer threads. The angle-adjustable pipe shed 8 and the horizontal jet grouting pile 9 work together to reinforce the soil, so as to prevent the existing subway from subsidence or other damages.

The shield tunnel in the soft soil area passes through the existing subway tunnel, and the working condition that the clear distance between the outer edges of the two tunnels is less than (equal to) 12m. The construction range of the adjustable angle pipe shed 8 is determined by the clear distance between the outer edges of the two tunnels. The larger the clear distance, the smaller the construction scope, and the smaller the net distance, the larger the construction scope. As shown in Figures 4 and 5, two tangent lines of the existing subway tunnel are made through the center of the shield tunnel to form an angle α, and the angle of the construction range of the adjustable angle pipe shed 8 is β, so that β=2α, β is exactly the range that the angle-adjustable pipe shed 8 is used for construction.

The first phase of the new Hangzhou Metro Line 2, Zhonghe Road Station to Fengqi Road Station, under the section of the No. It is divided into two parts: spiral unearthed pipe shed vault support, and horizontal jet grouting soil reinforcement and improvement.

(1) Spiral unearthed pipe shed vault support

"Spiral unearthed directional pipe shed" uses pipe shed steel pipe 12 with a diameter of 159mm as the outer casing, and auger drilling tools are installed in the pipe. After installing the measurement probe, the pipe shed steel pipe 12 is pushed into the soil with a pipe jacking rig, and at the same time, the helical drilling tool is turned clockwise. The soil that enters the pipe is crushed and transported out of the pipe; when the angle of the steel pipe 12 of the pipe shed is deflected, the wedge plate installed at the end of the drilling tool is used to correct the angle according to the probe measurement and surface settlement monitoring. During the construction of the adjustable-angle pipe shed 8, the installation of the adjustable-angle pipe shed 8 must be carried out completely under the monitoring of the guiding instrument, and optical measurement must be carried out to ensure that the adjustable-angle pipe shed 8 cannot invade the shield below and remain in the designed position. within range. The construction of the horizontal jet grouting pile 9 needs to be carried out under the monitoring of guiding instruments, and a certain consistency must be ensured so as to form an arch support structure. The LED measuring light is installed in the auger tool of the pipe shed, and the elevation and angle of the LED light point are measured from the mouth of the pipe by the theodolite, and the trajectory of the steel pipe 12 of the pipe shed is jointly measured and calculated by cooperating with the measurement data of the probe instrument. The pipe shed steel pipe 12 is made of hot-rolled seamless steel pipe, with an outer diameter of 159mm and a wall thickness of 8mm. The length of each pipe shed steel pipe 12 is 6m. There are 25 vertically arranged, and the construction length of each single root is 45m, totaling 1260m. The extrapolation angle is 1.5%-2%, measured with a 0.1% precision probe, the grouting material is P.O42.5 cement, the water-cement ratio is 0.8:1, and the grouting pressure is 0.5-1.0MPa. The grouting amount of a single pipe shed steel pipe 12 is estimated by the following formula: Q=πR _k ² Lηξ, where R _k is the slurry diffusion radius, R _k =1.2r, r is the steel pipe radius; L is the steel pipe length; ξ is taken as 0.85 is the fullness coefficient of grouting; η is the void ratio (%).

1. Construction points of adjustable angle pipe shed 8:

(1) The steel pipe 12 of the pipe shed does not have grouting florets, but a grouting hole with a diameter of about 4cm per meter is used as a pressure relief hole for grouting and horizontal rotary spraying;

(2) The angle-adjustable pipe shed is constructed with 8 spaced jump holes to avoid excessive disturbance range of continuous construction;

(3) The entrance section of the angle-adjustable pipe shed 8 has a plain concrete structure in the strata, and it is first broken into holes with a down-the-hole hammer, and then sent to the pipe shed steel pipe 12 after completion, using a spiral excavation construction process;

(4) The actual unearthed volume of the spiral inside the pipe should be less than the theoretical unearthed volume, so as to avoid settlement caused by excess unearthed;

(5) The construction of the adjustable-angle pipe shed 8 should be planned or adjusted according to the monitoring and measurement data, and construction without data is strictly prohibited.

2. The construction process flow chart of the spiral unearthed pipe shed is shown in Figure 1, and the specific implementation is as follows:

(1) Set up a drilling platform and a shared platform for horizontal rotary spraying construction;

(2) The drilling rig is installed, and after the construction of the angle-adjustable pipe shed 8 is completed, the drilling rig continues to carry out the horizontal rotary spraying construction;

(3) Get rid of plain concrete obstacles on the face 10 and the entry section of the formation:

①The structural wall of the operation face 10 adopts high-speed water drill to open holes according to the design position, the hole diameter is 180mm, and the opening angle is drilled according to the design and construction angle of the adjustable angle pipe shed 8;

②There are plain concrete obstacles in the stratum 6-10m away from the face 10, and the Φ170mm down-the-hole hammer is used to drill and break along the opening of the face 10.

(4) Put the Φ138mm helical unearthed drilling tool into the processed pipe shed steel pipe 12, the two ends of the pipe shed steel pipe 12 have male and female threads, install the reaming wedge drill bit 11 at the end of the helical drilling tool, and install the angle detection instrument inside the drill tool ;

(5) Check the mechanical status of the drilling rig and the working status of the instrument before the steel pipe 12 of the pipe shed is jacked;

(6) When the drilling rig is in place for drilling, the drilling rig and the face 10 are fixed to improve the construction accuracy; after the pipe shed steel pipe 12 is pushed into the soil layer 1m, the rig is started to rotate, and the angle change of the pipe shed steel pipe 12 is measured;

(7) After the jacking of the first pipe shed steel pipe 12 is completed, disassemble the joint between the drilling rig and the angle-adjustable pipe shed 8, return to the original position along the guide rail, and manually install the second pipe shed steel pipe 12, and install a screw in the pipe shed steel pipe 12. Drilling, buckled and connected with the first pipe shed steel pipe 12 to form a whole, jacking and rotating to unearth;

(8) When there is an inclination deviation in the angle of the steel pipe 12 in the pipe shed, when the deviation exceeds the design value ±0.5%, start the deviation correction program, stop the rotation of the drilling tool, and operate the jacking steel pipe 12 in the pipe shed according to the design method:

① The upward deviation of the pipe shed steel pipe 12 requires reducing the inclination angle of the pipe shed steel pipe 12 and adjusting the angular position of the auger wedge bit 11 downward, as shown in the direction of the wedge bit 11 in Fig. 6 .

② The downward deviation of the pipe shed steel pipe 12 requires upward adjustment of the inclination angle of the pipe shed steel pipe 12 and upward adjustment of the angular position of the auger wedge bit 11, as shown in the direction of the wedge bit 11 in FIG. 7 .

③ The angle of the steel pipe 12 in the pipe shed is normal and no adjustment is required, as shown in Figure 8.

④ When the steel pipe 12 of the pipe shed deviates to the left and right, refer to the inclination adjustment method, adjust the wedge-shaped plate to adjust the deviation correction position, and push the steel pipe 12 into the pipe shed to perform the deviation correction operation.

(9) The pipe shed steel pipes 12 under construction must be numbered hole by hole and root by root before installation, and take over and jack them in the order of numbering;

(10) Adjustable angle pipe shed 8 grouting:

① Check the pipeline and mechanical condition before grouting, and do a grouting test after confirming that it is normal, and determine the reasonable grouting parameters before construction can be carried out;

② During the grouting process, check at any time whether there is any grouting at the orifice, adjacent holes, and the thinner parts of the covering layer, and take quick-setting measures such as adding water glass if necessary; if the pressure suddenly rises during the grouting process, pipe blockage may occur , should be stopped for inspection;

③The grouting pressure reaches the design pressure value;

④ The grouting process should be assigned special personnel to record in detail the grouting time, grout consumption and grouting pressure and other data;

⑤ After the grouting is finished, clean the holes of the pump and pipeline;

⑥ Grouting sequence: from bottom to top, skip hole grouting.

(2) Improvement of horizontal jet grouting soil reinforcement

"Horizontal rotary grouting pile curtain wrapping partition" refers to the construction of horizontal rotary grouting piles 9 between adjacent adjustable angle pipe sheds 8, and the use of ultra-high pressure cutting and stirring of cement slurry to separate the soil around the adjustable angle pipe sheds 8. The body is disturbed and consolidated, and the angle-adjustable pipe shed 8 is wrapped and overlapped with the adjacent horizontal jet grouted pile 9 after jet spraying into piles to form a support structure with high load bearing and curtain partition effect. The construction of the horizontal rotary grouting pile 9 utilizes the limit track 16 arranged outside the pipe shed steel pipe 12 of the existing angle-adjustable pipe shed 8 to achieve construction accuracy through the limit welding 13 . The horizontal jet grouting piles 9 are arranged on the upper side of the shield tunnel outline 7 170 mm outside the shield steel ring, the distance between adjacent horizontal jet grouting piles 9 is 300 mm, and the diameter of horizontal jet grouting piles 9 is 500 mm. Interlocking 200mm, the construction length of a single horizontal jet grouting pile 9 is 45m, the consolidation material of the horizontal jet grouting pile 9 is P.O42.5 cement, and the water-cement ratio is 1:1; the construction track of the horizontal jet grouting pile 9 is adjacent to The angle-adjustable pipe shed 8 is the same. Generally, the construction speed is required to be 5-15 r/min, and the pull-back speed is 15-25 cm/min.

1. Technical requirements for horizontal jet grouting pile 9:

(1) The horizontal jet grouting pile 9 adopts alloy drill bit and circulating fluid drilling to control the loss of sediment, and the length of the pile is set in one time according to the actual situation on site to complete the predetermined pile length;

(2) The accuracy of horizontal drilling is kept consistent with the 8 rails of the adjustable angle pipe shed through the limit installed on the drill bit, and the appropriate limit device is determined through the construction of test piles according to the tunnel angle and construction experience;

(3) The horizontal rotary grouting pile 9 adopts cement single-fluid slurry, and the water-cement ratio of the grouting slurry is controlled to be 1:1;

(4) The drilling pressure is 3-5MPa, and the drill-exiting pressure is controlled at 35MPa±5MPa. When spraying grout, it is necessary to control the amount of grout return and the settlement of the arch; the grouting flow rate is 80L/min-90L/min;

(5) The position deviation of the horizontal jet grouting pile 9 is ±50mm; the inclination angle and the design error are ±1%;

(6) The length of the horizontal jet grouting pile 9 shall not be less than the design pile length; the 28-day unconfined compressive strength of the cement-soil consolidation body shall be greater than 3MPa, and the pile body shall ensure continuous and uniform support effect;

(7) Make the following records for each horizontal jet grouting pile 9 from drilling to pile formation: construction date, drilling time, end time, jet jet pressure, jet jet lifting speed, pile length, grouting volume;

(8) The construction process of the pile body should be continuous and cannot be interrupted to prevent the phenomenon of broken piles and short piles. If the machine stops for 30-120 minutes due to mechanical failure or other reasons, the rotary spraying should be repeated for 1m, and if it exceeds 2 hours, it should be treated as a broken pile and the pile should be re-drilled.

2. The flow chart of the horizontal rotary spraying construction process is shown in Figure 2, and the specific implementation is as follows:

(1) Install rotary spray drilling tools and limit rails;

(2) Drilling:

① opening;

② Preparation of circulating slurry;

③Drilling and drilling.

(3) High-pressure rotary spraying:

① Check the high-pressure grouting pump, the grouting can only be started when the pump pressure meets the design requirements;

② Check the tightness of the drilling rig before spraying, and slowly pressurize to the design value to stabilize the spraying;

③ Arrange special personnel to operate and observe pump pressure changes in high-pressure spraying, and notify and solve problems in time if any problems are found;

④ Spray the drill pipe to the design end hole position to stop grouting, and clean the pipeline with clean water under high pressure;

⑤ Strictly follow the design requirements for construction pressure and grout ratio.

(4) Sealing:

After spraying to the designed final hole position, stop spraying, quickly pull out the drill pipe and drill bit, and use woven bags or cotton silk to seal the hole.

(5) Clean pipes and equipment.

After the construction is completed, the pipeline and equipment should be flushed with clean water and high pressure in time, and moved to the next pile position after completion.

Claims (5)

1. A soil composite reinforcement structure for a soft soil shield passing through an existing subway, characterized in that it includes: a shield tunnel outline (7), an adjustable angle pipe shed (8) and a horizontal jet grouting pile (9) ; The outer side of the outline (7) of the shield tunnel to be excavated is provided with a row of adjustable angle pipe sheds (8), the adjustable angle pipe sheds (8) include pipe shed steel pipes (12), and the adjacent pipe sheds Horizontal jet grouting piles (9) are arranged between the steel pipes (12) in the shed, and the horizontal jet grouting piles (9) wrap the angle-adjustable pipe shed (8) and engage with the adjacent horizontal jet grouting piles (9) connected; the horizontal jet grouting pile (9) comprises a jet grouting drill pipe (14) and a drill pipe overcoat (15), and the pipe shed steel pipe (12) is connected alternately with the jet jet drilling pipe (14), and the The outside of the pipe shed steel pipe (12) is provided with a limit track (16), and the outer surface of the rotary jet drill pipe (14) is provided with a drill pipe jacket (15), and the limit track (16) and the drill pipe jacket (15) The integral arch shell is formed by limit welding (13). 2. The soil composite reinforcement structure for soft soil shield passing through the existing subway according to claim 1, characterized in that: the angle-adjustable pipe shed (8) is divided into multiple sections from back to front along the longitudinal extension direction of the tunnel Segments. 3. The soft soil shield according to claim 1 passes through the soil composite reinforcement structure of the existing subway, characterized in that: the pipe shed steel pipe (12) uses hot-rolled seamless steel pipes, and the pipe shed steel pipes (12) are two Both ends are pre-processed into outer threaded buckles. 4. according to claim 1, the soft soil shield passing through the soil composite reinforcement structure of the existing subway is characterized in that: two tangents of the existing subway tunnel are made through the center of the shield tunnel, and the angle between the two tangents is is α, and the angle formed by the center of the shield tunnel and the two edges of the adjustable angle pipe shed (8) is β, and β=2α. 5. A construction method for the soft soil shield passing through the soil composite reinforcement structure of the existing subway as claimed in claim 1, characterized in that, comprising the following steps: S1, spiral unearthed adjustable angle pipe shed (8) vault support; S1.1. Set up a drilling platform and a shared platform for horizontal rotary spraying construction; S1.2, install the drilling rig, after the construction of the adjustable angle pipe shed (8) is completed, the drilling rig continues to carry out the horizontal rotary spraying construction; S1.3. Remove plain concrete obstacles on the tunnel surface (10) and the entrance section of the formation: the structural wall of the tunnel surface (10) uses high-speed water drills to open holes according to the design position, and the opening angle is adjusted according to the angle of the pipe shed (8) Drilling at the design and construction angle; using a down-the-hole hammer to drill into the plain concrete obstacle at the entrance section of the broken stratum along the opening of the face (10); S1.4. Insert the auger unearthed drilling tool into the processed pipe shed steel pipe (12), the male and female threads at both ends of the pipe shed steel pipe (12), and install the reaming auger wedge-shaped drill bit (11) at the end of the auger drilling tool , the angle detection instrument is installed inside the drilling tool; S1.5. Check the mechanical status of the drilling rig and the working status of the instrument before jacking the pipe shed steel pipe (12); After starting the drilling rig to rotate, measure the angle change of the pipe shed steel pipe (12) into the soil; S1.6. After the jacking of the first pipe shed steel pipe (12) is completed, disassemble the joint between the drilling rig and the angle-adjustable pipe shed (8), return to the original position along the guide rail, and manually install the second pipe shed steel pipe (12). An auger is installed in the pipe shed steel pipe (12), and is buckled and connected with the first pipe shed steel pipe (12) to form a whole, and is pushed in and rotated to be unearthed; S1.7. When the inclination angle of the pipe shed steel pipe (12) deviates, start the deviation correction program, stop the drilling tool rotation, and operate the jacking pipe shed steel pipe (12) according to the design method: the pipe shed steel pipe (12) deviates upward, lower the pipe shed The inclination angle of the shed steel pipe (12) is to adjust the angular position of the auger wedge bit (11) downward; the downward deviation of the shed steel pipe (12) is to adjust the inclination angle of the shed steel pipe (12) upward, and the angle of the auger wedge bit (11) is adjusted upward position; when the pipe shed steel pipe (12) deviates to the left and right, refer to the inclination angle adjustment method to adjust the wedge-shaped plate to adjust the deviation correction position, and push into the pipe shed steel pipe (12) to perform the deviation correction operation; S1.8. The steel pipes (12) under construction must be numbered hole by hole and root by root before installation, and take over and jack in the order of numbering; S1.9, Adjustable angle pipe shed (8) grouting: check the pipeline and mechanical condition before grouting, do a grouting test after confirming normal, and determine reasonable grouting parameters; check the orifice, Whether there is any grouting phenomenon in the adjacent holes and the thinner part of the covering layer; assign a special person to be responsible for the grouting process, record the grouting time, grout consumption and grouting pressure and other data; after the grouting, clean the pump and pipeline to complete The construction technique of the angle-adjustable pipe shed (8); S2, horizontal jet grouting soil reinforcement improvement; S2.1. Install the rotary spray drilling tool and the limit rail; S2.2. Drilling: opening holes, preparing circulating slurry, and drilling; S2.3. High-pressure rotary grouting: Check the high-pressure grouting pump, and start grouting when the pump pressure meets the design requirements; check the sealing of the drilling rig before grouting, and spray grouting after the pressure reaches the design value; arrange special personnel to operate the high-pressure grouting and observe the change of pump pressure; the drill pipe is sprayed to the design end hole position to stop grouting, and the pipeline is washed with clean water under high pressure; S2.4. Hole sealing: After spraying grout to the designed final hole position, stop spraying, pull out the drill pipe and drill bit, and use woven bags or cotton silk to seal the hole; S2.5. Clean the pipeline and equipment, and complete the construction process of horizontal rotary spraying.