CN111206937A

CN111206937A - Pile group construction method for removing intruding main body structure in shield interval

Info

Publication number: CN111206937A
Application number: CN202010089129.XA
Authority: CN
Inventors: 罗宁宁; 罗凛; 龙秀堂
Original assignee: China Railway No 5 Engineering Group Co Ltd; Chengdu Engineering Co Ltd of China Railway No 5 Engineering Group Co Ltd
Current assignee: China Railway No 5 Engineering Group Co Ltd; Chengdu Engineering Co Ltd of China Railway No 5 Engineering Group Co Ltd
Priority date: 2020-02-12
Filing date: 2020-02-12
Publication date: 2020-05-29

Abstract

The invention discloses a pile group construction method for removing an intruding main body structure in a shield area.A temporary construction vertical shaft and a transverse passage are arranged at an exit of a slow-walking street-crossing passage in a mining method underground excavation tunnel section of a subway station area, and a scheme of tunneling from the transverse passage to a large mileage downslope is adopted, namely, the temporary construction vertical shaft is used as a hoisting-out vertical shaft, and the transverse passage is used as a construction passage and a tunnel entrance door; and a dewatering well is arranged in the underpass tunnel along the right side of the underground excavated tunnel, so that the influence of the right-side underground water on the underground excavated tunnel is reduced. In the underpass pedestrian passageway, a precipitation well is arranged by utilizing the manual hole digging, so that the influence of the left-side underground water on the underground excavated tunnel is reduced; a drainage open ditch or blind pipe and a water collecting well are arranged in the excavated tunnel, so that underground water flows into the water collecting well along the open ditch or blind pipe, and then water is pumped out of the tunnel by a water pump, thereby ensuring waterless construction. The advanced anchor rod can be used for reinforcing the stable stratum of the surrounding rock.

Description

Pile group construction method for removing intruding main body structure in shield interval

Technical Field

The invention belongs to the technical field of subway construction, and particularly relates to a pile group construction method for removing intruding main structures in a shield region.

Background

The mine method has the advantages that the tunnel is located below the urban main road and the underpass tunnel, the traffic flow is large, the condition that no construction ground precipitation well is arranged on the left side of the underground excavation tunnel to pump and drain underground water is avoided, and how to organize precipitation construction and reduce the influence of the underground water on the tunnel construction is a serious difficulty of the project; meanwhile, the bedrock in the field is mudstone and has a medium-thickness layered structure, local joints and cracks in the moderately weathered bedrock are developed, and under the action of underground water, the phenomena of differential weathering, softening and disintegration are easy to occur along the structural surface of the mudstone to form a soft and weak mudstone interlayer, the local part of the soft and weak interlayer is seriously influenced by the underground water, and the mud phenomenon is caused in the soft and weak interlayer. The interval tunnel is exposed that the weak intermediate layer is mainly located the vault, and the part is located arch bottom and lateral wall. When the tunnel is positioned at the vault, the tunnel excavation is easy to roof and collapse, and the stability of the tunnel face is influenced; when positioned on the soffit, affects the substrate stability.

Disclosure of Invention

The invention provides a pile group construction method for removing an intruding main body structure in a shield interval, and aims to solve the existing problems.

The invention is realized in this way, a shield interval demolishs the pile group construction method which invades the major structure, in the underground excavation tunnel section of the subway station interval mining method, near the exit of the slow-walking crossing tunnel, sets up a temporary construction vertical shaft and cross passage, adopt and tunnel the scheme to the great mileage downslope from the cross passage, namely utilize the temporary construction vertical shaft as hanging out the vertical shaft, the cross passage is regarded as constructing the passage and entering the cave door; the method comprises the following steps:

s1: constructing a vertical shaft, wherein the construction vertical shaft is constructed by adopting an open cut method;

s2: precipitation construction, wherein 5 precipitation wells are respectively arranged on the south and north sides of the underground excavated tunnel by a mining method, and 4 precipitation wells are arranged at the end heads of the small mileage; the well pipe is made of reinforced concrete pipe, and a nylon net is coated outside each section of filter pipe in the sand-gravel layer; the strainer is a reinforced concrete pipe with a strip-shaped hole, a sand settling pipe is arranged below the strainer, and a solid pipe is arranged above the strainer to a wellhead; clean pebbles are adopted as filter materials, and clay is adopted for sealing holes when the pebbles are filled to 2m below the ground;

s3: adopting an advanced pipe shed to support and reinforce the top of the transverse passage before the transverse passage enters the tunnel and the vertical shaft breaks the wall; three steel frames are adopted at the connection position of the rear tunnel after the wall breaking of the vertical shaft for parallel close arrangement and strengthening treatment;

s4: excavating and supporting a transverse channel, wherein the transverse channel is constructed by a step method and a temporary transverse bracing method, and the primary support adopts 35 cm-thick C25 early strength injection concrete, a full-ring double-layer reinforcing mesh, a grid steel frame and a self-advancing type foot locking anchor rod;

s5: before secondary lining of the transverse passage, reinforcing the front line hole opening of the underground excavated tunnel by a mining method by adopting an advanced pipe shed; the secondary lining of the transverse channel adopts C35 reinforced concrete, the position of a reserved main tunnel is not subjected to secondary lining, a bottom plate and an arch wall are cast in a whole section by times, a ring frame beam and the lining are constructed synchronously, the bottom plate and part of side walls are cast firstly, then the side walls and the arch crown are cast, and steel arch frames and supports are adopted for construction;

s6: primary support of the transverse channel is broken, and three steel frames are connected in parallel and densely arranged at the hole-broken connection position of the transverse channel;

s7: breaking tunnel enclosure group piles, and breaking by adopting a mode of combining rope sawing and manual chiseling;

s8: the mining method is characterized in that a 'CD' method is adopted for construction, C25 early strength spraying concrete, a full-ring double-layer reinforcing mesh, a profile steel frame and a self-advancing type locking anchor rod are adopted for primary support, profile steel is adopted for temporary vertical support, the temporary vertical support is installed one by one, C15 plain concrete is adopted for bottom plate construction, and C15 concrete is adopted for front hole backfilling; the municipal tunnel pile foundation of the large road passing through the brocade city is broken by a wire saw and a manual chisel, and is broken by sections and trusses.

Further, in step S2, the method specifically includes:

s21, forming a hole, namely, adopting a 280 rotary drilling rig to ensure that the aperture is not less than 600mm and ensure that the drilling hole is circular and vertical;

s22, cleaning the hole, replacing by injecting clean water, pumping out sediments by using a sand pump, and measuring the well depth;

s23, lower well pipes, wherein the well pipes are made of reinforced concrete pipes, the well pipes are concentric and welded tightly, the top of each well pipe is 20cm lower than the ground, and the ground is protected by steel plate covers of 1m x 20 mm;

s24, filling filter materials, diluting slurry in the well after the well pipe reaches the designed depth, filling the filter materials around the well pipe, uniformly and continuously filling the filter materials around the well pipe by adopting manual work, filling the filter materials to the position of 2m of an average well mouth, filling the rest with plain soil, and adopting homogeneous non-angular pebbles which are less than or equal to 10mm as the filter materials;

s25, after filling of the filter material, washing the well according to the regulations, and within 8 hours after completion of the well, putting a sewage pump into the well bottom for repeated pumping and washing to ensure the water seepage effect, and observing the change conditions of the water level and the water yield in the well washing process;

s26, installing a submersible pump and a pipeline system, connecting the pipeline below the buried surface of the dewatering well with a nearby drainage ditch, taking the water part pumped out by the dewatering well as construction water, collecting the rest water through the drainage ditch at the side of the foundation pit, and draining the water into a municipal drainage system.

Further, in step S4, the step excavation is a construction process in which the upper half of the cross section is excavated first, the lower part is excavated at the same time after the excavation reaches a certain length, and the upper and lower parts are moved in parallel, and a temporary cross brace is applied to the upper step to reduce the deformation of the arch structure under the condition of poor geological conditions of the cross channel; excavating a construction flow: construction measurement → ventilation → artificial excavation → initial spraying → mucking → setting of a net suspension → vertical frame (temporary support) → re-spraying → next cycle.

Further, the step excavation specifically comprises:

a, excavating 1 upper step, and constructing 2 primary supports and temporary cross braces of the tunnel body structure;

b, after the upper step is constructed to a proper distance, 3m later than 1 part of the upper step excavates the left side of 3 lower steps, and performs primary support of 4 hole body structures; excavating 5 lower steps on the right side by 3 and 2 grilles, and performing primary support of 6 hole body structures;

c, delaying by 5 parts and 3 trusses of grids, and performing primary support of 7 parts of bottom plate structures;

d, after the excavation and support of the transverse channel are finished, pouring 8 bottom plates and partial side walls of the transverse channel for one time;

and e, pouring 9 arch walls of the transverse channel and partial side walls for lining at one time by using the simple steel arch frames and the supports.

Further, in step S7, the method specifically includes:

s71, before pile cutting, the steel arch supports the tunnel face, and C25 early strength concrete 8-10 cm is sprayed on the closed tunnel face and the excavation face;

s72, arranging 2 steel floral tubes with the length of 3.5m and the diameter of 42 mm at the middle part of the fender post and the upper part of the excavation contour line, and firmly welding the rear end of each floral tube with the constructed arch center;

s73, breaking rock mass within a range of 50cm around the pile by using an artificial air pick, and spraying concrete to seal; cutting the pile body section by using a rope saw from bottom to top, controlling the length of each section within 1.5m, transporting the whole pile body section outside, and crushing;

s74, after pile cutting is finished, drilling a fracture of the primary support outer pile body along the primary support outer contour by using a manual pneumatic pick to be smooth and flat;

s75, excavating and erecting a steel frame in time after pile cutting, and sealing sprayed concrete; after primary support, radial grouting is carried out on the primary support in the vault range by adopting a steel perforated pipe with the length of 3.5m and the diameter of 42 mm, the grouting interval is 1.0m multiplied by 0.8m, and the arrangement is in a quincunx shape.

Compared with the prior art, the invention has the beneficial effects that: and a dewatering well is arranged in the underpass tunnel along the right side of the underground excavated tunnel, so that the influence of the right-side underground water on the underground excavated tunnel is reduced. In the underpass pedestrian passageway, a precipitation well is arranged by utilizing the manual hole digging, so that the influence of the left-side underground water on the underground excavated tunnel is reduced; a drainage open ditch or blind pipe and a water collecting well are arranged in the excavated tunnel, so that underground water flows into the water collecting well along the open ditch or blind pipe, and then water is pumped out of the tunnel by a water pump, thereby ensuring waterless construction. The advanced anchor rod (advanced small conduit) is utilized, and the function of reinforcing the stable stratum of the surrounding rock can be achieved.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the underground excavation tunnel section of the subway station interval mining method, a temporary construction vertical shaft and a transverse passage are arranged near the exit of a slow-speed street crossing passage, and a scheme of tunneling from the transverse passage to a large-mileage downslope is adopted, namely the temporary construction vertical shaft is used as a hoisting-out vertical shaft, and the transverse passage is used as a construction passage and a tunnel entrance door;

the earthwork is hoisted out by adopting a 10t row hoisting steel plate bucket; the construction shaft is constructed by adopting an open cut method; the transverse channel and the left line mine tunnel are constructed by adopting a spray anchor construction method, and the structure adopts a composite lining. The top of the transverse channel is supported and reinforced by a phi 108 advanced pipe shed before the wall breaking of the vertical shaft, and the joint of the hole after wall breaking is reinforced by three steel frames in parallel and densely arranged;

the transverse channel is constructed by a step method and a temporary transverse bracing method, the primary support is formed by C25 early strength injection concrete with the thickness of 35cm, full-ring double-layer phi 8@150 x 150 steel mesh, grid steel frame @500mm and self-advancing type foot locking anchor rods (L is 3m), the secondary lining is formed by C35 reinforced concrete (no secondary lining is arranged at the position of a reserved main line tunnel), the bottom plate and the arch wall are poured in whole sections in times, the ring frame beam and the lining are constructed synchronously, the bottom plate and part of the side wall are poured firstly, then the side wall and the arch crown are poured, and the steel arch frame and the support are constructed.

Construction of the mine method tunnel advanced pipe shed is completed before the lining of the transverse passage, and three steel frames are adopted for parallel close arrangement strengthening treatment at the hole connection position after wall breaking; the tunnel main line is constructed by a 'CD' method, phi 108 advanced large-pipe shed supports are arranged, the pipe sheds L are 20m @0.4m (rings) × 18m (longitudinal) vault are arranged within 150 degrees, the initial supports are formed by C25 early strength injection concrete with the thickness of 35cm, full-ring double-layer phi 8@150 × 150 reinforcing mesh, I22a section steel frames @500mm and R32S self-advancing foot-locking anchor rods (L is 3m), the temporary vertical supports are formed by I20a section steel (installed one by one), the bottom plate is formed by C15 plain concrete with the thickness of 0.6m, and C15 concrete is backfilled in a main hole;

and the municipal tunnel pile foundation penetrating downwards is broken by a wire saw and manual chiseling, and is broken by sections and trusses. This regional full-line ground precipitation of undercut adopts the tube well precipitation, falls groundwater to excavation face below 1 meter during the construction, combines the interior light drainage mode of hole to handle simultaneously, ensures the anhydrous construction of tunnel.

The south and north sides of the mine method passage are respectively provided with 5 dewatering wells, the end head of the small mileage is provided with 1 dewatering well, and 3 constructed shaft dewatering wells are utilized; wherein: the north dewatering well is arranged in the underpass tunnel, the diameter of the dewatering well is 600mm, the well depth is 15m (at least 5m is guaranteed to penetrate into mudstone), the distance is 16m, and the distance from the excavation contour line is 9-12 m. The south dewatering well is arranged in the ground road; the diameter of the precipitation diameter is 600mm, the well depth is 22m (ensuring that the precipitation diameter is deep into mudstone for at least 5m),

the well pipe is a reinforced concrete pipe with the inner diameter phi of 300, and each section of filter pipe in the sandy gravel layer is coated with a 50-mesh nylon net; the strainer is a reinforced concrete pipe with a strip-shaped hole, each length is 2.5m, the total length of the strainer is 10.0m, a sand settling pipe with the length of 2.5m is arranged below the strainer, and the strainer is a solid pipe from the upper part of the strainer to the position of a well mouth. Clean pebbles are adopted as filter materials, the specification is 5-10 mm, the non-uniformity coefficient is less than 2, and the impurity content is not more than 3%; when the soil is filled to 2m below the ground, clay is adopted to seal holes,

the precipitation construction method adopts a 280 rotary drilling rig to ensure that the aperture is not less than 600mm and the depth is greater than the designed depth so as to consider the influence generated by the deposition height which can be reached by sediments during pumping and ensure that the drilling hole is circular and vertical. And (3) performing hole cleaning operation before the well pipe is lowered, wherein hole cleaning is replaced by injecting clean water, sediment is pumped out by using a sand pump, and the well depth is measured. The well pipe is made of reinforced concrete pipes, each section is 2.5m long, and the well pipe is hoisted and placed in sections by truck cranes. The well pipes are concentric and welded tightly, the top of the well pipes is 20cm lower than the ground to the designed depth, and the ground is protected by a steel plate cover with the thickness of 1m by 20 mm. When a well pipe is lowered, the adjustment is strictly carried out according to the actual geological condition of a drilling hole position, and when a sand layer is encountered, the corresponding pipe section of the sand layer adopts a real pipe. After the well pipe reaches the designed depth, the mud in the well is diluted properly, and then the filter material is filled around the well pipe immediately. The filter material is filled along the periphery of the well hole by manual work, the filter material is filled to the position of 2m of the well mouth, and the rest is filled with plain soil. Homogeneous non-angular pebbles with a size less than or equal to 10mm are used as filter materials. And after the filling of the filter material is finished, washing the well according to the regulations. And (3) within 8 hours after the well is formed, a sewage pump is placed into the bottom of the well for repeated pumping and washing, the water seepage effect is ensured, and the change conditions of the water level and the water yield are observed in the well washing process. Mounting a submersible pump and a pipeline system, connecting the pipeline below the buried surface of the dewatering well with a nearby drainage ditch, taking part of water pumped by the dewatering well as construction water, gathering the rest water through the drainage ditch at the side of the foundation pit, and discharging the water into a municipal drainage system; and after flushing, performing single-well test pumping on the well pipe, flushing the well again if abnormal conditions exist, and performing a pumping test again.

The construction of the advanced large pipe shed is characterized in that the 150-degree range of the tunnel arch of the mine method tunnel is reinforced by grouting in the tunnel of the advanced large pipe shed, large steel pipes are inserted according to a certain external insertion angle in a design range outside an excavation contour line before the tunnel is excavated, cement paste is injected, and then the tail parts of the steel pipes and steel frames are welded to form an integral arch pre-supporting structure. Because the arch part is positioned in the pebble bed within the range of about 1.5m, the traditional construction process is difficult to form holes, and the pipe following drilling method is adopted for construction.

Self-advancing hollow anchor rod construction

When the surrounding rock is broken or the underground water is much, the self-advancing hollow anchor rod advanced support is applied to the arch part of the tunnel in the transverse channel and the mine method. The construction parameters of the advanced anchor rod of the mine tunnel are as follows: R32N self-advancing type advance hollow anchor rod, L is 3m, hoop interval 0.3m, vertical interval 1.0m, and arch 150 degree scope is arranged, and the angle of inserting outward is 10 ~ 15. This horizontal passage advance stock construction parameter: R32N self-advancing type advance hollow anchor rod, L is 3m, hoop interval 0.3m, vertical interval 1.5m, and arch 150 degree scope is arranged, and the angle of inserting outward is 10 ~ 15.

Lofting the hole site of the anchor rod according to a design drawing, drilling holes by using an anchor rod drilling machine (or manual operation), installing a connecting sleeve, installing the anchor rod with the length of 3m and a drill bit, and drilling the holes to the designed depth; the drill hole should be round and straight, the diameter of the anchor rod hole is 50mm, and the allowable depth error is +/-5 cm. Drilling to the designed depth, adopting high-pressure air to wash the hole, dismounting the connecting sleeve, and enabling the exposed length of the anchor rod head to be 10-15 cm. After the anchor rod body is drilled to the designed depth, before the self-propelled anchor rod is installed, whether a hole in the anchor rod body and a water hole of a drill bit are smooth or not is checked, the hole is washed by water or air until water or air returns to an orifice, the drilling machine and the drill bit tail can be detached, and a grout stop plug is installed in time.

The upward hole is provided with an exhaust pipe and a grout stop plug, the exhaust pipe is inserted into the bottom of the hole and fixed, and the outer leakage end penetrates through a reserved hole position on the grout stop plug; and (3) injecting the grout stop plug into the hole opening by about 300mm through the exposed end of the anchor rod by using a steel pipe as a hole sealing for grouting, wherein if the grouting pressure is high or the surrounding rock is broken, the hole sealing by using an anchoring agent can be adopted. Connecting a grouting pipe, injecting grout from the self-advancing anchor rod pipe, returning grout from the gap between the outside of the hole bottom pipe and the surrounding rock, wherein the grouting pressure is 0.4-0.7 MPa, when the hole opening is full of grout, grouting is carried out in a staggered and spaced mode, the effect of grouting is checked after grouting is finished, and grout is supplemented for unqualified people. The mortar in the anchor rod hole is required to be full and compact. The advanced anchor rods are driven into the steel frame from the upper part of the section steel frame, the exposed ends are supported on the steel frame behind the excavation face, and the advanced anchor rods and the steel frame form a pre-supporting system together.

The shaft wall of a shaft is broken, a transverse passage and the north side wall of the shaft form a 90-degree angle to be vertically connected, 3 surrounding piles in total of No. 13, No. 14 and No. 15 in the range of a tunnel door need to be broken before excavation construction, and the surrounding piles are broken after the reinforcement of the advanced pipe shed is completed according to the arrangement of the construction progress. Dividing according to the height of the horizontal channel construction steps, breaking the fender post into an upper part and a lower part, wherein the breaking sequence is carried out from the upper part to the lower part and from two sides to the middle part, and manually breaking by adopting small machinery; in the process of breaking and entering the transverse channel into the hole, the monitoring and measurement of the stability of the vertical shaft foundation pit should be enhanced.

Firstly, breaking 1 part of internal enclosure piles and a well wall, mounting 2 parts of 3 densely-arranged parallel grids and I22b temporary transverse supports after the breaking is finished, and anchoring the grid arch on the enclosure piles at two sides in a mode of implanting phi 25 steel bars, wherein the anchoring depth is not less than 50 cm; meanwhile, phi 22 longitudinal connecting steel bars are adopted to connect the grid arches into a whole at the circumferential distance of 1m, and C25 early strength concrete is sprayed immediately. After the 1 part of pilot tunnel is advanced to 3m, the surrounding piles and the well wall within 3 parts are broken, 3 pieces of densely-arranged parallel grids of IV parts are extended after the breaking is finished, and C25 early strength concrete is sprayed immediately. 3 parts behind the grating, 3 parts in VI part close-packed parallel grating after the breaking of the surrounding piles and the well wall within 5 parts, and C25 early strength concrete is sprayed immediately. 3 inverted arch close-spaced parallel grids with 3 holes are additionally arranged and firmly connected with a side wall steel frame, C25 early strength concrete is immediately sprayed, and the holes are initially supported and sealed into a ring as soon as possible.

Excavating a transverse channel, wherein the design length of the transverse channel is 12.789m, the transverse channel is of a curved-top straight wall structure, the excavation size is 7.25 multiplied by 4.7m, construction is performed by adopting a step method and a temporary cross brace method according to the section size, the geology and the condition of peripheral structures, the height of an upper step is 3.85m, and the height of a lower step is 3.40 m; the method comprises the following steps of (1) manually excavating mainly, assisting by mechanical excavating, manually excavating the periphery of a contour line and an upper step by small machines and tools such as an air pick, and mainly excavating the lower step and a local position by the mechanical excavating; and conveying the human tooling slag in the tunnel to a vertical shaft bottom, vertically lifting the human tooling slag to a ground temporary slag disposal site through a gantry crane, and discarding the soil to a permanent slag site when the soil to be crushed can be transported outwards.

The step excavation is a construction process that the upper half part of a section is excavated firstly, the lower part is excavated after the section is excavated to a certain length, the upper part and the lower part are simultaneously moved in parallel, and meanwhile, a temporary cross brace is applied to the upper step under the condition of poor geological conditions of a cross passage so as to reduce the structural deformation of the arch part; excavating a construction flow: construction measurement → ventilation → artificial excavation → initial spraying → mucking → setting of a net suspension → vertical frame (temporary support) → re-spraying → next cycle.

Excavating 1 upper step, constructing primary supports and temporary cross braces of 2 hole body structures, excavating 3 lower step left sides after 1 part by 3m after the upper step is constructed to a proper distance, and constructing primary supports of 4 hole body structures; after 3 parts and 2 parts of grids, 5 parts of the right side of the lower step is excavated, and 6 parts of preliminary support of the hole body structure is performed. After 5 parts of the grating, 3 parts of grating are used for performing preliminary bracing of 7 parts of bottom plate structures. And after the excavation and supporting of the transverse channel are finished, pouring 8 bottom plates and partial side wall linings of the transverse channel at one time. And (3) pouring 9 arch walls of the transverse channel and partial side walls for lining at one time by using the simple steel arch frames and the supports.

The method comprises the following steps of (1) constructing a transverse channel initial support, constructing an R32S (32/6.0) self-advancing hollow anchor rod by adopting an YT-28 air drill pushing method, and performing pressure grouting by using a grouting machine; the R32S lock pin anchor rod is directly drilled in by an air drill, and grouting is carried out by an exhaust method; the grid steel frame is processed outside the hole in sections and is assembled in the hole; processing the outside of the reinforced bar net hole into a net sheet, and paving the net sheet in the hole; the sprayed concrete is sprayed with C25 concrete by a sprayer.

The reinforcing mesh adopts phi 8 reinforcing steel bars, the mesh spacing is 150mm multiplied by 150mm, the mesh outside the hole is processed into 0.65 multiplied by 1.0m mesh sheets in a slicing mode, the mesh sheets are transported to the site after being inspected to be qualified, and the mesh sheets are manually installed in the hole. After the excavation of the tunnel body is finished, firstly, primarily spraying concrete for 4cm on the surface of the surrounding rock, ensuring the excavation surface to be sprayed smoothly, then paving a first layer of reinforcing mesh on the spraying surface, and reasonably arranging positioning reinforcing steel bars and the reinforcing mesh to be welded and fixed. After the steel frame is installed and fixed, a second layer of steel bar mesh is laid on the inner side of the steel frame and is welded with the connecting bars and the steel frame firmly. The lapping length of each layer of reinforcing mesh is not less than 1 mesh size, and the lapping nodes among the meshes must be welded.

The transverse channel arch centering is two kinds of grid steelframes and interim shaped steel steelframes, the arch centering is according to design dimension and handing over the concentrated preparation of segmentation outside the hole in the processing factory, deliver to the scene after examining and trying to piece together qualified before leaving the factory, the manual work is installed in the hole, the arch centering is assembled by each unit, connect with the bolt through the angle steel of hookup between each unit, the arch centering is welded together with phi 22 twisted steel longitudinally, the circumferential interval is 1m, inside and outside staggered arrangement.

And (3) installing an arch frame, namely installing the arch frame in time after the first layer of mesh is laid, accurately hanging a central line and fixing the elevation of an arch part before installing the arch frame, and controlling the center, half-width size and height of the arch frame. The arch center is installed by utilizing the simple support platform, the arch center is assembled from the center to two sides, all units are connected by adopting 4 bolts, and the connecting plates are closely attached. After the arch centering is installed in place according to the designed lofting point position, a positioning anchor rod is used for fixing, and 2 long foot locking anchor rods with the length of 3m are required to be arranged at the arch foot position of each arch centering for locking. The arch frame is a main reinforcing body for the weak surrounding rock of the primary support, the arch frame is longitudinally welded into a stressed whole by phi 22 thread reinforcing steel bars, the annular distance is 1m, and the inner side and the outer side are arranged in a staggered mode. The arch frame should be installed according to the design position, should set up the saddle piece along the outer fringe of arch frame every 2m when having great clearance between steelframe and the layer of spouting. According to the design, the number of the cushion blocks at each position is counted according to one cushion block No. 1 and two cushion blocks No. 2. After the steel frame is erected, the sprayed concrete should be applied as soon as possible, and the steel frame is completely covered, so that the steel frame and the sprayed concrete are stressed together. The concrete spraying should be carried out in layers, and the thickness of each layer is as follows: the arch part is 50-100 mm; the side wall is 70-150 mm, and the material is sprayed from the arch springing or upwards to prevent the arch springing (wall springing) from being hidden by the upper spraying material but not compact, and the strength is not enough, so that the instability of the arch springing (wall springing) is caused. The thickness of the steel frame protective layer is not less than 3.5 cm. When the partial excavation is carried out, the lower half part of the steel frame is excavated, the steel frame falls to the bottom in time and is lengthened, and the steel frame is closed into a ring.

And (3) spraying concrete, and spraying C25 early strength concrete on an unstable face by adopting a wet spraying process according to design requirements and tunnel excavation conditions to seal in time.

Wet spraying operation, namely spraying concrete twice; initial concrete spraying: after the tunnel is excavated, the initial concrete spraying is carried out in time to close the excavated surface, and the concrete spraying is carried out to close the tunnel face when necessary, so as to prevent the rock stratum from weathering and collapsing. Before spraying, the spraying concrete thickness control mark is embedded in the excavated surface. Re-spraying concrete: and after the construction of the arch frame, the R32S self-advancing foot-locking anchor rod, the reinforcing mesh, the embedded grouting pipe and the like is finished, re-spraying concrete to the designed thickness. And (5) after the sprayed concrete is finally set for 2 hours, spraying water for curing, wherein the curing time is not less than 7 days. Firstly, supplying air, then starting up and then feeding; meanwhile, the high-pressure air is used for blowing the sprayed surface to remove dust on the sprayed surface. When the spraying is finished, the machine is stopped firstly and then is shut down. The spray head is controlled manually and operated by two persons. The spraying route is from top to bottom and takes an S-shaped motion; when spraying, the nozzle makes continuous circular motion and forms spiral forward, and the latter circle presses one third of the former circle. The air pressure required by the jet machine is 0.3-0.5 Mpa, and the distance between the spray head and the sprayed surface is preferably controlled to be 1.5-2.5 m. The nozzle is vertical to the spraying surface, and if the spraying surface is covered by the steel bar net sheet and the grating, the nozzle can be slightly inclined by 10-20 degrees. The spraying thickness is influenced by the slump of concrete entering the spraying machine, the effect of the accelerator and the air temperature, when the wall part is sprayed by the wet spraying machine, the spraying thickness is not more than 10cm at one time, and when the arch part is sprayed, the spraying thickness is not more than 7cm at one time.

And backfilling and grouting the primary support, wherein the grouting pipe behind the primary support is a phi 42 steel flower pipe, the wall thickness is 3.5mm, the length is 1.0m, the grouting pipe is manufactured into a small conduit type, the interval between the grouting pipes is 1.0m multiplied by 0.8m, and the grouting pipes are arranged in a quincunx manner. And (3) injecting cement slurry to the backs of the arch of the primary support after the primary support is closed into a ring for a certain length. The pipes are generally distributed in a pre-buried manner, namely, are buried before the concrete is sprayed.

Constructing a secondary lining, wherein the secondary lining of a transverse channel for construction adopts a curved top straight wall type section form, the clearance size is 3.2m multiplied by 5.752m (width multiplied by height), and the thickness of C35 reinforced concrete is 400 mm; the arch part and the side wall main reinforcement are made of phi 22 deformed steel, the designed distance is 10cm, and the horizontally distributed reinforcement is made of phi 20 deformed steel, the distance is 20 cm; the bottom plate main reinforcement adopts phi 25 glass fiber reinforced steel bars, the distance is 10cm, the horizontally distributed reinforcement adopts phi 20 glass fiber reinforced steel bars, the distance is 20cm, the lacing wires adopt phi 10 round steel, and each intersection point needs to be arranged.

After the primary support of the transverse channel is completely finished, secondary lining construction is carried out, the construction is carried out from the bottom plate to the arch part twice, the secondary lining of the part I (the bottom plate and part of side walls) is constructed for the first time, in order to facilitate the operation of workers, a construction joint is arranged at a position 1500mm below a temporary cross brace, after the strength of concrete reaches 80% of the designed strength, the temporary cross brace of the primary support is dismantled, the secondary lining of the part II (the rest side walls and the vault) is constructed, construction is carried out according to the arrangement of construction organization by adopting a combination form of an I18 type steel arch frame and a 50mm thick wood template, and the I18 type steel arch frame is used as a main stressed framework with the; and (5) synchronously constructing the ring frame beam and the lining.

And backfilling and grouting after two backing, reserving a grouting pipe and an exhaust pipe at the vault of each ring, wherein the grouting pipes are phi 32 steel pipes, are arranged in a quincunx manner above the arch forming line, and are circumferentially spaced by 2m and longitudinally spaced by 2-3 m. The technological process of the secondary backing post-backfill grouting is the same as the technological process of the primary support backfill grouting, and the grout adopts cement paste.

The construction of the front line tunnel, the minimum depth of the tunnel earthing by the interval mining method is about 14.8m, the maximum depth is 16.7m, the longitudinal slope of the tunnel from the large mileage to the small mileage is 21.774 per mill, and the top strata are sequentially as follows: the soil covering layer above the tunnel is sequentially filled with miscellaneous fill, clay and pebble soil from top to bottom and is designed into V-level surrounding rock. The clear height of the tunnel excavation is 4.16m, and the clear width is 8.32 m. The engineering in this interval adopts semicircular section, anchor spraying type lining structure, and the interval is single-hole single-line tunnel.

The method comprises the following steps of advanced support construction, wherein a first ring advanced large pipe shed and a self-advancing advanced hollow anchor rod (when surrounding rocks are broken and underground precipitation is more) at the opening of a main tunnel are constructed after primary support of a transverse channel is completed, the surrounding strata of the opening of the main tunnel are reinforced, and the safety of tunnel entering construction is ensured; and constructing the tunnel body section by cooperating the advanced large pipe shed, the self-advancing advanced hollow anchor rod support and the excavation circulating footage.

And (3) primary support of the transverse channel is broken, after the advance support construction of the opening is finished, primary support of the transverse channel in the range of the main tunnel is broken before the main tunnel enters the tunnel, the primary support of the transverse channel is broken from two sides to the middle one by one, and the primary support stability of the transverse channel and the monitoring and measurement of the ground surface are enhanced in the breaking process by adopting an artificial pneumatic pick. The concrete construction steps are as follows: and (6) measuring and setting out, and measuring and marking the excavation contour line position of the main hole. And (3) applying foot-locking anchor rods, reinforcing the grid steel frames within the range of the broken hole, applying 2R 32S self-advancing foot-locking anchor rods to each grid, wherein the length of each foot-locking anchor rod is 3m, and the foot-locking anchor rods and the grid steel frames are welded firmly. And 4 pieces of phi 25 deformed steel bars are adopted for grid connection, and two adjacent grid steel frames are connected into a whole outside the excavation contour line and are welded firmly. And D, removing the grating from two sides to the middle one by one. And installing a front-hole type steel arch, immediately installing a front-hole I22a type steel arch after the grid arch is completely broken, ensuring that the type steel arch is closely attached to the grid arch, and timely applying a locking anchor rod and C25 early strength sprayed concrete.

Excavating by a 'CD' method, wherein the designed length of a tunnel by a front-opening mine method is 69.304m, the tunnel is in a semicircular structure, the excavation size is 8.32 multiplied by 4.16m, and the construction is carried out by the 'CD' method according to the section size, geology and the condition of surrounding structures; the method comprises the following steps of (1) manually excavating mainly, mechanically excavating secondarily, manually excavating the periphery of a contour line by using small machines such as an air pick and the like, and mainly excavating core soil and local positions by using the machines; and (3) carrying out muck removal and transportation on the man-made tool in the tunnel to the bottom of the vertical shaft, vertically lifting the muck to a ground temporary muck yard through a gantry crane, and abandoning the muck to a permanent muck yard when the muck can be transported outwards.

The 'CD' method divides an excavation section into a left pilot tunnel and a right pilot tunnel for construction, wherein the left pilot tunnel is constructed firstly, and the right pilot tunnel is constructed synchronously 3-5 m behind the left pilot tunnel. If the geological condition is poor, a bottom plate is constructed timely according to monitoring measurement, so that the support system forms a ring to reduce structural deformation; the construction steps of the CD method are as follows: 1. firstly, excavating 1 part of arc guide pit, constructing primary support of I and II part of tunnel body structures, spraying concrete to seal the tunnel face if necessary, and constructing III part of bottom plate in due time according to monitoring and measuring conditions. 2. After 1 arc pilot tunnel is excavated to a proper distance, 2 arc pilot tunnels are excavated after 3-5 m lags behind 1 arc pilot tunnel, primary support of the IV part is performed, concrete is sprayed to seal the tunnel face if necessary, and a V part bottom plate is performed at proper time according to monitoring and measuring conditions, so that a supporting structure forms a ring.

The method comprises the steps of annular excavation reserved core soil and temporary vertical bracing, and under the premise of ensuring safety and quality, in order to accelerate construction progress, construction is carried out by adopting the annular excavation reserved core soil and temporary vertical bracing method; the method for excavating the reserved core soil annularly is a method for excavating the core soil in the middle part by leading an arc-shaped guide pit on the upper section. Firstly, excavating an arc pilot tunnel of a section, excavating core soil after the arc pilot tunnel is constructed to a certain length, and simultaneously performing temporary vertical bracing under the condition of poor geological conditions to reduce the structural deformation of an arch part; excavating a construction flow: construction measurement → ventilation → arc pit excavation → initial spraying (spraying concrete to close the tunnel face if necessary) → mucking → setting up a hanging net → vertical frame → secondary spraying → excavation of core soil → temporary vertical support → next cycle. The construction steps of the annular excavation reserved core soil method and the temporary vertical bracing method are as follows: 1. excavating 1 part of arc pilot tunnel, constructing primary support of II part of tunnel body structure, and spraying concrete to seal tunnel face if necessary. 2. After the arc guide pit is excavated to a proper distance, 3 parts of core soil are excavated after 1 part of the arc guide pit is excavated by 3m, temporary supports of the IV part I20a are constructed, and temporary vertical support arch foot pad concrete cushion blocks (0.6 x 0.5 x 0.3m) are constructed. 3. And (3) delaying for 5m, constructing the V-shaped bottom plate concrete, and constructing the bottom plate in a staggered manner in two steps according to the construction progress and the field condition.

Constructing a tunnel primary support by a main-hole mine method, constructing an R32S (32/6.0) self-advancing hollow anchor rod by adopting an YT-28 air drill pushing method, and performing pressure grouting by a grouting machine; the R32S lock pin anchor rod is directly drilled in by an air drill, and grouting is carried out by an exhaust method; the steel frame is processed outside the tunnel in sections, and is spliced inside the tunnel, and the arch centering of the tunnel is I22a type steel arch centering and I20a temporary vertical support; processing the outside of the reinforced bar net hole into a net sheet, and paving the net sheet in the hole; the sprayed concrete is sprayed with C25 concrete by a sprayer.

The reinforcing mesh adopts phi 8 reinforcing steel bars, the mesh spacing is 150mm multiplied by 150mm, the mesh outside the hole is processed into 0.8 multiplied by 1.2m mesh sheets in a slicing mode, the mesh sheets are transported to the site after being inspected to be qualified, and the mesh sheets are manually installed in the hole. After the excavation of the tunnel body is finished, firstly, primarily spraying concrete for 4cm on the surface of the surrounding rock, ensuring the excavation surface to be sprayed smoothly, then paving a first layer of reinforcing mesh on the spraying surface, and reasonably arranging positioning reinforcing steel bars and the reinforcing mesh to be welded and fixed. After the steel frame is installed and fixed, a second layer of steel bar mesh is laid on the inner side of the steel frame and is welded with the connecting bars and the steel frame firmly. The lapping length of each layer of reinforcing mesh is not less than 1 mesh size, and the lapping nodes among the meshes must be welded.

The steel frame of the interval tunnel is an I22a steel arch frame and an I20a temporary vertical support, the arch frame is manufactured in a centralized mode outside a tunnel according to design size and sectional sections, the arch frame is transported to the site after being inspected and assembled in a trial mode before leaving a factory, the arch frame is manually installed in the tunnel, the arch frame is formed by assembling units, the units are connected through connecting steel plates and bolts, the arch frame (including the vertical supports) is welded together longitudinally through phi 22 threaded steel bars, the annular distance is 1m, and the inner side and the outer side of the arch frame are arranged in a staggered mode. And (3) installing an arch frame in time after the first layer of meshes is laid, accurately hanging a central line and fixing the elevation of an arch part before the arch frame is installed, and controlling the center, half-width size and height of the arch frame. The arch frame is installed by using a core soil platform (simple support), the arch frame is assembled from the center to two sides, 4 bolts are adopted for connecting all units, and the connecting plates are closely attached. After the arch centering is installed in place according to the designed lofting point position, a positioning anchor rod is used for fixing, and 2 long foot locking anchor rods with the length of 3m are required to be arranged at the arch foot position of each arch centering for locking. The arch frame is the main reinforcing body of the primary support for the weak surrounding rock, the longitudinal space of the arch frame (vertical support) is welded into a stress whole by phi 22 thread reinforcing steel bars, the circumferential distance is 1m, and the inner side and the outer side are arranged in a staggered mode. After the steel frame is erected, the sprayed concrete should be applied as soon as possible, and the steel frame is completely covered, so that the steel frame and the sprayed concrete are stressed together. The concrete spraying should be carried out in layers, and the thickness of each layer is as follows: the arch part is 50-100 mm; the side wall is 70-150 mm, and the material is sprayed from the arch springing or upwards to prevent the arch springing (wall springing) from being hidden by the upper spraying material but not compact, and the strength is not enough, so that the instability of the arch springing (wall springing) is caused. The thickness of the steel frame protective layer is not less than 3.5 cm. When the partial excavation is carried out, the lower half part of the steel frame is excavated, the steel frame falls to the bottom in time and is lengthened, and the steel frame is closed into a ring.

And (3) spraying concrete, and spraying C25 early strength concrete on an unstable face by adopting a wet spraying process according to design requirements and tunnel excavation conditions to seal in time. The sprayed concrete adopts commercial concrete, a wet spraying process is adopted, the concrete is sprayed for two times, and the concrete is sprayed for the first time: after the tunnel is excavated, the initial concrete spraying is carried out in time to close the excavated surface, and the concrete spraying is carried out to close the tunnel face when necessary, so as to prevent the rock stratum from weathering and collapsing. Before spraying, the spraying concrete thickness control mark is embedded in the excavated surface. Re-spraying concrete: and after the constructions of the arch frame, the longitudinal connecting steel bars, the R32S self-advancing foot-locking anchor rods, the steel bar meshes, the embedded grouting pipes and the like are completed, concrete is re-sprayed to the designed thickness. And (5) after the sprayed concrete is finally set for 2 hours, spraying water for curing, wherein the curing time is not less than 7 days.

Backfilling and grouting for primary support, and installing a back grouting pipe: the grouting pipe behind the primary support adopts a phi 42 steel flower pipe, the wall thickness is 3.5mm, the length is 1.0m, the small guide pipe type is manufactured, the distance between the grouting pipes is 1.0m multiplied by 0.8m, and the plum blossom type arrangement is adopted. And (3) injecting cement slurry to the backs of the arch of the primary support after the primary support is closed into a ring for a certain length. The pipes are generally distributed in a pre-buried manner, namely, are buried before the concrete is sprayed. Before grouting, the grouting holes are cleaned, and grouting pipes are installed to ensure smooth grouting. The grouting must be continuously operated without stopping the pump at will to prevent the slurry from precipitating, blocking the pipeline and affecting the grouting effect.

The fender pile is broken, the underpass tunnel fender pile is positioned on the right side of the upper half section of the mine tunnel, phi 800mm @1500mm, 48 pieces are in total, structural stress is not involved, the fender pile is broken by adopting a mode of combining a rope saw and manual chiseling, and the concrete steps are as follows according to the principle of 'cutting off first, transporting outside and breaking after'. 1. Before pile cutting, the steel arch frame needs to be supported against the face, C25 early strength concrete 8-10 cm is sprayed to seal the face and the excavation face, and the stability of the rock mass of the operation face is kept. 2. 2 steel floral tubes with the length of 3.5m and the diameter of 42 are arranged in the middle of the fender pile and on the upper portion of the excavation contour line, and the rear end of each steel floral tube is firmly welded with the constructed arch centering to prevent the fender pile from falling. 3. The manual pneumatic pick breaks rock mass within 50cm of the periphery of the pile, and sprays concrete to seal; and cutting the pile body section by using a rope saw from bottom to top, controlling the length of each section within 1.5m, and crushing the whole pile body section after transportation. The observation is strengthened to the in-process of cutting the stake, prevents that fender pile from weighing down. 4. And after pile cutting is finished, drilling a fracture of the primary support outer pile body along the primary support outer contour by using a manual pneumatic pick, and rounding and flattening the fracture. 5. After pile cutting, excavating and erecting a steel frame in time, and spraying concrete for sealing; after primary support, radial grouting is carried out on the primary support in the vault range by adopting a steel perforated pipe with the length of 3.5m and the diameter of 42 mm, the grouting interval is 1.0m multiplied by 0.8m, and the arrangement is in a quincunx shape.

The bottom plate construction, the bottom plate design of just opening is 60cm thick C15 plain concrete, is equipped with 1% cross slope, does not influence the face construction, and the bottom plate adopts half stagger construction, and construction length 3m each time, and the left and right sides stagger a construction cycle. The concrete is pumped into a mould by a commercial concrete pump, vibrated by an inserted vibrating spear and manually finished and trowelled for forming. Before the construction of the bottom plate, the bottom slag and accumulated water are cleaned. In order to ensure the vibrating quality of the bottom plate concrete, the concrete is vibrated in an insertion mode while pouring, a vibrating rod is vertical during vibrating, is driven in quickly and slowly and is 10cm-15cm away from a template, and the concrete is vibrated until the concrete does not bubble or sink and the surface begins to be pulped. After the bottom plate is poured, the maintenance operation is reinforced, and the vehicle can be started when the strength of the bottom plate meets the requirement.

Backfilling the main hole, the transverse channel and the vertical shaft after the existing fender post penetrating downwards in the main hole is broken, backfilling the main hole by C15 plain concrete in a segmented and layered mode, correspondingly removing a vertical support of the channel of the mining method according to backfilling segmentation conditions, and avoiding the intrusion of primary support deformation into the construction range of the shield tunnel at the later stage; backfilling the area of the transverse channel in the outline range of the main tunnel by using C15 plain concrete; and the rest of the construction transverse passages and the temporary vertical shaft are backfilled by sand and pebbles mixed with cement, clay is backfilled within 3m of the top of the vertical shaft, and the pebbles are backfilled within 10m of the ground layer by layer without mixing a cementing material. The specific procedures are as follows: 1. the main hole backfilling is carried out in three sections from a small mileage to a large mileage, each section is divided into three layers, and the vertical supports are dismantled in sections. 2. Firstly, backfilling 1-1 part with C15 pumped concrete, after the concrete is initially set, constructing end templates of 1-2 parts and 2-1 parts, and pre-embedding a phi 50 grouting pipe in a 1-3 arch part; then pouring 1-2 parts of concrete and 2-1 parts of concrete in sequence. 3. Constructing 1-3, 2-2 and 3-1 plug templates, pouring concrete in sequence, and performing grouting and backfilling on 1-3 vault tops to ensure the tops to be compact and have no cavities. And (3) embedding a phi 50 grouting pipe in the arch top 2-3 after grouting. 4. Constructing the plug templates of 2-3 parts and 3-2 parts, pouring concrete in sequence, and grouting and backfilling the vault of 2-3 parts to ensure that the top is compact and has no cavity. And (3) embedding a phi 50 grouting pipe in the arch crown of 3-3 after grouting. 5. And constructing 3-3 plug templates, pouring concrete, and performing grouting and backfilling on 3-3 arch parts.

Backfilling the transverse channel and the vertical shaft, after 1-3 parts of concrete is initially set, backfilling the part S-1 by adopting sand and pebbles with the cement content of 5% in a layered mode, closing the plug templates of the parts 1-4, embedding a phi 50 grouting pipe along the vault of the transverse channel, and enabling a pipe orifice to extend out of a transverse channel hole door to be not less than 30 cm; then 1-4 parts were backfilled with C15 concrete. And backfilling the S-2 part to the arch top of the transverse passage by using sand and pebbles with the cement content of 5%, then grouting and backfilling the arch top, and then continuously backfilling the S-2. Sand and pebbles are adopted for backfilling S-3 layer by layer, and a tamping machine is used for tamping in the filling process to ensure compaction. The top 3m of the shaft was backfilled with clay.

Advanced geological prediction. Because the construction transverse channel is 12.789m long, the mine method tunnel is 69.304m long, the lines are short, and the lithology, water-rich and toxic and harmful gas conditions of the stratum are also found out by the prospecting borehole in the early period, the advanced detection of the precipitation effect and the detection of local toxic and harmful gas are mainly enhanced in the construction process, the lithology characteristics of the stratum of the project are combined, the geological forecast of the drilling method is mainly adopted in the construction process, and the concrete measures are as follows. 1. Advancing geological exploration: drilling a hole at a position of 50cm in the excavation contour line of the arch crown of the tunnel face, wherein the detection depth of each cycle is preferably controlled to be 30m, and the lap joint length of each cycle is not less than 5m during continuous drilling; the diameter of the drilled hole is not smaller than 89 mm; the vertical angle of the general section is preferably 1-3 degrees, and the external insertion angle is preferably controlled to be 1-3 degrees. 2. Deepening blast hole detection: drilling small-aperture shallow holes on the contour line of a tunnel excavation working surface by using an air drill to obtain geological information, wherein 1 hole is respectively arranged on the arch crown and the arch waist of each section, the depth of blast holes is deepened by more than 3 meters compared with the circulating footage, and the depth of the holes is not less than 5 m; the external insertion angle is preferably controlled to be 1-3 degrees.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A pile group construction method for removing an intruding main body structure in a shield area is characterized in that a temporary construction vertical shaft and a cross passage are arranged at the position, close to an outlet of a slow-walking street crossing passage, of an underground excavation tunnel section of a subway station area mining method, a scheme of tunneling from the cross passage to a big mileage downslope is adopted, namely the temporary construction vertical shaft is used as a hanging-out vertical shaft, and the cross passage is used as a construction passage and a tunnel entrance door; the method is characterized by comprising the following steps:

2. The pile group construction method for removing the invading main structure in the shield zone according to claim 1, wherein in step S2, it specifically comprises:

3. The pile group construction method for removing the invading main structure in the shield zone according to claim 1, characterized in that: in step S4, the bench method excavation is a construction process in which the upper half of the cross section is excavated first, the lower part is excavated after the excavation reaches a certain length, and the upper and lower parts are moved in parallel, and a temporary cross brace is applied to the upper bench to reduce the deformation of the arch structure under the condition of poor geological conditions of the cross channel; excavating a construction flow: construction measurement → ventilation → artificial excavation → initial spraying → mucking → arrangement of a suspended net → temporary support of a vertical frame → secondary spraying → the next cycle.

4. The pile group construction method for removing the invading main structure in the shield zone according to claim 3, wherein the step excavation comprises:

5. The pile group construction method for removing the invading main structure in the shield zone according to claim 1, wherein in step S7, it specifically comprises: