CN112855188B - Subway engineering soft soil stratum earth pressure balance shield construction method - Google Patents
Subway engineering soft soil stratum earth pressure balance shield construction method Download PDFInfo
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- CN112855188B CN112855188B CN202110040094.5A CN202110040094A CN112855188B CN 112855188 B CN112855188 B CN 112855188B CN 202110040094 A CN202110040094 A CN 202110040094A CN 112855188 B CN112855188 B CN 112855188B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
- E21D9/06—Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining
- E21D9/08—Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining with additional boring or cutting means other than the conventional cutting edge of the shield
- E21D9/087—Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining with additional boring or cutting means other than the conventional cutting edge of the shield with a rotary drilling-head cutting simultaneously the whole cross-section, i.e. full-face machines
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/04—Lining with building materials
- E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
- E21D11/105—Transport or application of concrete specially adapted for the lining of tunnels or galleries ; Backfilling the space between main building element and the surrounding rock, e.g. with concrete
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
- E21D9/06—Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining
- E21D9/08—Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining with additional boring or cutting means other than the conventional cutting edge of the shield
- E21D9/087—Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining with additional boring or cutting means other than the conventional cutting edge of the shield with a rotary drilling-head cutting simultaneously the whole cross-section, i.e. full-face machines
- E21D9/0873—Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining with additional boring or cutting means other than the conventional cutting edge of the shield with a rotary drilling-head cutting simultaneously the whole cross-section, i.e. full-face machines the shield being provided with devices for lining the tunnel, e.g. shuttering
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
- E21D9/12—Devices for removing or hauling away excavated material or spoil; Working or loading platforms
Abstract
The application discloses a soft soil stratum earth pressure balance shield construction method for a subway project, wherein the integral opening rate of a shield machine cutter head is 50%, openings are uniformly distributed on the whole disk surface, and mud cakes are prevented from being generated by tunneling in the whole disk surface; the shield constructs the machine unearthing mouth and sets up 2 gates, opens in turn in order to reduce the gushing pressure, disposes 2 bentonite pumps and is used for the improvement of dregs, and two pumps accessible single pipeline pours into the blade disc front portion into, also can pour into the hole shell outside all the way. The muck improvement effect is optimized by using the appropriate muck modifier and material proportion, and if the muck improvement is carried out by adopting high molecular polymers and the like, compared with the traditional foam muck improvement mode, the cohesiveness and the workability of the muck are improved, the occurrence of the gushing condition of the earth pressure shield in the water-rich soft soil stratum is effectively controlled, and the muck improvement method has the characteristics of high construction quality, quick construction progress and small influence of construction safety on the ground.
Description
Technical Field
The application relates to the field of subway construction, in particular to a soft soil stratum earth pressure balance shield construction method for a subway project.
Background
The shield construction method is widely applied to subway construction, the shield construction technology of the shallow earth covering of the water-rich soft stratum and the water-rich sandy gravel stratum is mature day by day, and the shield construction technology research of the deep water-rich soft soil stratum is deficient. The shield simultaneously passes through a muddy soil layer, silt fine sand and other deep water-rich soft soil layers, which is always a difficult point in construction, and if the shield construction is controlled improperly, the spiral soil discharging device is easy to gush and erupt, so that the conditions of ground settlement, even subsidence and the like caused by improper control of the pressure of an excavation surface can be caused.
Disclosure of Invention
The construction method has the advantages that accident treatment caused by possible accidents such as ground uplift, collapse and gushing and economic loss caused by prolonged construction period are avoided, and the construction method has strong economic benefits.
The application provides a soft soil stratum earth pressure balance shield construction method for a subway project,
firstly, selecting a type of a shield tunneling machine:
(1) the shield machine soil outlet is provided with 2 gates which are opened alternately to reduce the gushing pressure; a bentonite and high molecular polymer injection interface is reserved; is provided with a pressure maintaining pump interface
(2) 2 bentonite pumps are configured for improving the slag soil, and the two pumps can be injected into the front part of the cutter head through a single pipeline or can be injected out of the hole shell through one pipeline;
(3) selecting a belt conveyor with a small inclination angle of 10 degrees;
(4). 10 advanced grouting holes are designed in the circumferential direction of the shield body, wherein 6 advanced grouting holes are arranged at the upper part, 4 advanced grouting holes are arranged at the lower part, and 7 horizontal advanced grouting holes are arranged in the front shield partition plate; can carry out advance slip casting to excavation face the place ahead and carry out the geological strengthening.
Secondly, shield launching and tunneling.
(1) The starting attitude of the shield machine is that the front shield is 25-35mm in head-up, the tail shield is 8-12mm in head-up, and the starting base is an ascending slope which is increased by 2-4 per mill relative to the line so as to keep the upward movement trend of the shield machine;
(2) two short guide rails are laid in the tunnel door and used as extensions of the starting frame rail
(3) In the process of separating the negative ring duct pieces from the shield tail, wood wedges are adopted for wedging between the duct pieces and the brackets, and simultaneously, each ring duct piece is hoop-tightened by 1 steel wire rope;
(4) before starting, welding anti-rolling torsion steel plates on two sides of a middle shield and a tail shield of the shield machine, and controlling the rolling angle of a cutter head within +/-3 by timely adjusting the steering of a left rotating cutter head and a right rotating cutter head by operators;
thirdly, shield tunneling trial: laying ground surface deformation measuring mark points along the shield propulsion axis and a transverse section vertical to the axis, tracking and measuring the settlement deformation of the ground during construction, analyzing and adjusting the construction parameters such as propulsion thrust, propulsion speed, shield front soil pressure, propulsion gradient, grouting pressure, quantity and the like to control the ground surface deformation in a minimum range, thereby obtaining optimized construction parameters for the normal propulsion of the shield at the next stage;
fourthly, shield tunneling
(1) And selecting a pressure value P of the soil bin. The P value can counterbalance the stratum soil pressure and the hydrostatic pressure, and if the sum of the hydrostatic pressure and the soil pressure of the stratum in the center of the cutter head is P0, the P is KxP 0, and K is 1.0-1.3;
(2) maintaining the pressure P of the soil bin by maintaining the balance of the excavated soil volume and the soil discharge volume; synchronous grouting: according to the increase of synchronous grouting amount, the stratum change adjusts the synchronous grouting mixing proportion, and in the weak water-rich stratum, the synchronous grouting amount is increased to 6.5-7.3 m3The initial setting time of the slurry is shortened to 4 hours, and the gap between the tunnel and the segment is filled in time;
(3) secondary grouting: arranging secondary grouting in time after the shield segment is separated from the shield tail 5 rings, wherein the secondary grouting adopts double-liquid slurry, and the initial setting time is controlled to be 20-48 s;
(4) and (3) slag soil improvement, wherein a slag soil improvement foaming agent is adopted in a soft stratum of mucky soil, and the opening and the rotating speed of a screw machine are controlled, so that the slag discharging condition can be effectively controlled. In the soft water-rich sand layer, in order to control the screw machine gushing caused by the slag segregation in the soil bin, high molecular polymer (polyacrylamide) is injected to improve the slag;
fifthly, shield arrival.
By adopting the technical scheme, when the earth pressure balance shield machine tunnels, the earth bin is filled with the earth cut by the cutter, then the earth pressure in the earth bin is utilized to counterbalance the earth pressure and the water pressure of the working face, meanwhile, the earth removing operation corresponding to the shield propelling quantity is carried out by the earth removing equipment of the screw conveyor, and the balance between the excavated earth quantity and the earth removing quantity is always maintained in the tunneling process so as to keep the front soil body stable and prevent overlarge settlement of the earth surface caused by the loss of underground water and soil. When the earth pressure balance shield machine is constructed in a water-rich soft soil stratum, the selected earth pressure balance shield is subjected to adaptability analysis and reasonable matching; by controlling the pressure of the soil bin, the soil discharge amount, the rotating speed of the screw conveyor and other tunneling parameters; making slag soil improvement, synchronous grouting and secondary grouting; the construction of the shield tunnel is smoothly realized.
Furthermore, the cutter head adopts a structural form of 4 main beams and 4 auxiliary beams, and the integral opening rate is 50%; the cutter head panel is provided with 6 paths of single-pipe single-pump single nozzles, the nozzles adopt a back-mounted replaceable design, and a central area is provided with 3 paths of single-pipe single-pump modifier injection ports; the cutter head is provided with 4 active stirring rods which are distributed on two tracks.
By adopting the technical scheme, the stability of the excavation surface is ensured, and the surface settlement during the excavation of the silt stratum is reduced; the probability of mud cake generation in the center area of the cutter head is reduced.
Furthermore, the shield is provided with a 4-way single-pipe single-pump single-nozzle foam injection system.
By adopting the technical scheme, the shield is provided with a 4-path single-pipe single-pump single-nozzle foam injection system; a premixing mode is adopted, so that the foaming effect is enhanced, and the foam consumption is reduced; the nozzle assembly can be completely drawn out from the back of the cutter head, so that the maintenance or the replacement is convenient.
Further: 2 bentonite pumps are configured for improving the residue soil; the two pumps can be injected into the front part of the cutter head through a single pipeline, can also be injected out of the shield shell all the way, and can be matched with the head raising of the shield machine when the head falling condition of the shield machine occurs.
By adopting the technical scheme, the shield can generate the situation of larger thrust when the shield tunnels in sand, egg layers and broken rock stratums, particularly, bentonite can be injected outside the shield shell for lubrication after the side cutter is worn, and the system can reduce the abrasion resistance of the shield shell to a certain degree.
Further: the hinged seal of the shield tunneling machine is a double-finger polyurethane rubber combination, an emergency sealing air bag and an emergency polyurethane grease injection system; the shield tail design adopts 3 steel wire brushes, 1 steel plate brush and 4 polyurethane injection holes, so that the shield tail sealing design value is increased to 6bar, and the 4 emergency polyurethane injection systems inject polyurethane under the emergency condition of water burst and sand burst of the shield tail.
By adopting the technical scheme, the polyurethane is injected under the emergency condition that water burst and sand burst occur at the shield tail, so that the water stop and sand stop functions can be quickly completed, and the construction risk is effectively controlled; polyurethane is injected under the emergency condition that water gushing and sand gushing occur at the shield tail, the functions of water stopping and sand stopping can be completed quickly, and the construction risk is effectively controlled.
Furthermore, the construction process of shield arrival sequentially comprises end reinforcement, end precipitation, horizontal hole probing, mounting of the receiving base, fixing, sealing of the tunnel portal, tunneling of the arrival section and stepping up of the receiving base after penetration.
By adopting the technical scheme, the problems of sudden change of the shield posture, head falling of the shield machine, dislocation of the segments, water burst and sand burst at the tunnel portal and the like are avoided.
Further, full-ring secondary grouting is carried out at 20 rings before the tunnel is taken out, double-liquid slurry is adopted for secondary grouting, 1-ring water stop rings are applied at intervals of 4 rings in principle, the grouting pressure is controlled to be 0.3-0.5 MPA, the gaps of the pipe pieces are filled, underground water flow is cut off, and meanwhile, synchronous grouting slurry channeling is controlled; and (3) performing connection measurement before penetration 150m before shield receiving, and simultaneously measuring shield postures before 100m, 50m and hole exit respectively to ensure that the hole exit postures of the shield are consistent with the designed axis. Through measurement and check, the horizontal posture of the hole is controlled to be +/-5 mm, and the horizontal trend is as follows: 3mm/m, vertical attitude control at front point +30mm, vertical trend: and + 1- +3mm/m, the shield is lifted by 3cm when going out of the tunnel, the receiving frame is lowered by 1cm, the receiving attitude is ensured to be fitted with the center of the tunnel portal, the conflict between the elevation of the bottom of the cutter head and the elevation of the receiving frame is prevented, the shield machine is ensured to smoothly go up the receiving frame, and the shield is prevented from 'planting heads'.
Through adopting above-mentioned technical scheme, can promote the quality of hole one end.
Furthermore, in the small-radius curve segment, the thrust difference of the oil cylinder is controlled to be 50-60 bar (the right side is larger than the left side), and the thrust is controlled to be 1300T-1600T, so that slow and fast rotation is realized; the right side is properly extended out for active hinging so as to be suitable for the left turning trend of the shield machine, the left side hinging is controlled to be 40-50 mm, the right side hinging is controlled to be 100-120 mm, and the left-right side stroke difference is about 60mm through gradual adjustment; encrypting and adding the attendance and guiding system to measure the station shift: performing guide system station change once in 12-15 rings on average (according to actual conditions), and performing encryption manual retest at 20-25 rings; three times per cycle: before assembly, after assembly and in the tunneling process, shield tail clearance measurement is carried out, a basis is provided for segment selection, the shield tail clearance is controlled to be 70-50 mm, and the difference value of the upper shield tail clearance, the lower shield tail clearance and the left shield tail clearance is controlled to be 20 mm; adjusting the synchronous grouting proportion, properly shortening the initial setting time of the grout: and (3) determining proper grouting parameters by adjusting the slurry mixing ratio, and controlling the initial setting time of synchronous grouting slurry to be 4 hours.
By adopting the technical scheme, the problem that the small-radius curve segment is not favorable for shield deviation correction and posture control due to the undersize of the turning radius and the wrong platforms of tunnel forming segments in different degrees is solved.
Furthermore, when the shield passes through the water-rich sand layer to remove slag and spout, the screw machine is alternately opened by double gates to reduce the spouting pressure, bentonite or high-molecular polymer is injected into the soil bin wall and the screw machine through the reserved bentonite and high-molecular polymer injection interface to relieve the slag spraying pressure of the screw machine, and a slurry pump or a slurry pipe can be connected through the pressure maintaining pump interface of the screw machine to relieve the slag spraying pressure.
By adopting the technical scheme, the pressure balance of the soil bin is kept, and the shield tunneling machine can stably tunnel.
Furthermore, the tail shield is provided with a rotary slurry outlet ring in a rotating mode, the rotary slurry outlet ring is provided with an inclined slurry outlet hole, and slurry is rotated and discharged through slurry pressure.
By adopting the scheme, the slurry outlet ring rotates, slurry is circumferentially injected between the pipe piece and the soil body, and the slurry injection is more uniform.
In summary, the present application has the following beneficial effects: when the earth pressure balance shield machine is used for tunneling, earth cut by the cutter is filled in the earth bin, then earth pressure in the earth bin is utilized to counterbalance the earth pressure and water pressure of an operation surface, meanwhile, earth discharging operation corresponding to shield propelling quantity is carried out by using a screw conveyor earth discharging device, and the balance between the excavated earth quantity and the earth discharging quantity is always maintained in the tunneling process so as to keep the front soil body stable and prevent overlarge settlement of the earth surface caused by the loss of underground water and soil. When the earth pressure balance shield machine is constructed in a water-rich soft soil stratum, the selected earth pressure balance shield is subjected to adaptability analysis and reasonable matching; by controlling the pressure of the soil bin, the soil discharge amount, the rotating speed of the screw conveyor and other tunneling parameters; making slag soil improvement, synchronous grouting and secondary grouting; the construction of the shield tunnel is smoothly realized.
Drawings
FIG. 1 is a schematic structural diagram of a shield tunneling machine;
FIG. 2 is a schematic view of the construction of the cutter head;
FIG. 3 is a schematic structural view of the inclination angle of the belt conveyor;
FIG. 4 is a schematic view of a hinge seal;
FIG. 5 is a schematic structural view of a shield tail seal;
FIG. 6 is a flow chart of shield launch;
FIG. 7 is a flow chart of a shield arrival process;
FIG. 8 is a schematic structural view of plugging a hole by a pre-buried steel plate;
FIG. 9 is a flow chart of a synchronous grouting process;
FIG. 10 is a schematic structural view of a rotary slurry outlet ring of the shield tail;
FIG. 11 is a schematic view of a rotary slurry outlet ring;
FIG. 12 is a small radius curve segment dislocation analysis diagram;
FIG. 13 is a schematic view of a segment sizing configuration;
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples.
A soft soil stratum earth pressure balance shield construction method in a subway project comprises the main process flows of shield machine model selection → construction preparation → shield starting → shield tunneling → unearthing → segment assembly → circular tunneling → shield reaching → tunnel end plugging → shield machine demolition and hoisting.
The key construction process is explained in detail below.
Firstly, the engineering shield tunneling machine is designed in a targeted manner (refer to fig. 1);
1. cutter head design (see fig. 1 and 2);
aiming at the main problems of silt clay and silt, the design considers the construction of difficult strata such as a pile foundation and the like, and the cutter head is designed in a targeted way as follows:
2. designing a main drive;
the characteristics of the construction of the muddy stratum are considered in the shield design, and the main drive is pertinently designed as follows:
3. screw conveyor design (see fig. 1);
(1) a shaft type screw conveyor is adopted, the inner diameter is 900mm, the maximum passing particle size is 340 multiplied by 560mm, a front gate and two slag discharging gates are designed, the shaft of the screw conveyor can stretch, and the stretching amount is 900 mm. The rated torque of the screw conveyer is 210kNm, and the maximum rotating speed is 22 r/min. The bentonite and high molecular polymer injection interface and the pressure maintaining pump interface are reserved, the energy storage device is arranged on the rear gate, and the gate can be automatically closed when the equipment is powered off.
(2) And (3) anti-blowout design:
when groundwater is rich, the permeability coefficient of a soil layer is high, and soil blocks in the screw machine are difficult to form soil plugs, the possibility of the phenomenon of surging of the screw machine is high. For this reason, the machine is designed specifically as follows:
the earth outlet of the shield tunneling machine is provided with 2 gates which are opened alternately to reduce the gushing pressure.
And secondly, an injection interface of bentonite and high molecular polymer is reserved, and the bentonite or the high molecular polymer can be injected into the soil bin wall and the screw machine if necessary so as to relieve the slag spraying pressure of the screw machine.
And a pressure maintaining pump interface is arranged, and a slurry pump or a slurry pipe can be connected when necessary to relieve the slag spraying pressure.
4. Belt conveyor design
During construction in a water-bearing stratum, gushing is easy to occur, thin slag of a belt conveyor with a large angle is difficult to convey, slag and soil are seriously splashed, and civilized construction is influenced. The variable-frequency driving belt conveyor with a small inclination angle of 10 degrees is adopted, and according to related engineering cases, the residue soil conveying efficiency is greatly improved.
5. Advanced grouting system
And a perfect advanced grouting scheme is considered during shield body design. The shield body circumference designs 10 advance slip casting holes altogether, and 6 upper portions wherein, 4 lower parts, anterior shield baffle are equipped with 7 horizontal advance slip casting holes, can carry out advance slip casting to excavation face the place ahead when necessary and carry out the geological strengthening.
6. Muck improving system
(1) A foam system:
the shield is provided with a 4-path single-pipe single-pump single-nozzle foam injection system;
a premixing mode is adopted, so that the foaming effect is enhanced, and the foam consumption is reduced;
the nozzle assembly can be completely drawn out from the back of the cutter head, so that the maintenance or the replacement is convenient.
(2) Bentonite system:
2 bentonite pumps are configured for improving the residue soil; the two pumps can be injected into the front part of the cutter head through a single pipeline, can also be injected out of the shield shell all the way, and can be matched with the head raising of the shield machine when the head falling condition of the shield machine occurs.
The shield tunneling machine is likely to generate a situation of larger thrust when a sand layer, an egg layer and a broken rock stratum are tunneled, particularly, after the side cutter is abraded, bentonite can be injected outside the shield shell for lubrication, and the abrasion resistance of the shield shell can be reduced to a certain degree by the system.
7. An active articulation system;
the shield tunneling machine is in active hinge connection, so that the posture of the shield tunneling machine during small-radius shield tunneling is convenient to control, and when the shield tunneling machine is prone to head falling, the posture of the shield tunneling machine is convenient to control, and the shield tunneling machine is matched with head rising.
8. The hinged shield tail reinforced design of the shield machine (refer to fig. 4 and 5);
(1) a hinged pertinence reinforcement design;
the strengthening idea of the hinge joint for increasing the emergency air bag is formed. The design of conventional rubber combination and emergency air bag sealing of the original muddy water balance shield machine is optimized to be a design of a double-finger polyurethane rubber combination, an emergency sealing air bag and an emergency polyurethane grease injection system. The hinge reinforcement design further enhances the sealing effect, and the emergency air bag can be quickly inflated (or filled with oil) in an emergency, so that the effect of quickly isolating the ground pressure in the emergency is realized. The designed sealing value reaches 10bar, so that the shield machine is ensured to be protected more safely and effectively.
(2) Shield tail seal pertinence reinforcing design
4 steel plate brushes are adopted in the design of the shield tail of the original muddy water balance shield machine, at present, experts propose an optimized design, the optimized design is adjusted to 3 steel wire brushes, 1 steel plate brush and 4 polyurethane injection holes, and the design value of shield tail sealing is improved to 6 bar. Plus 4 urgent polyurethane injection systems of way, pour into polyurethane into in the shield tail under the emergent condition that gushes water and gush sand, can accomplish stagnant water, end sand function fast, effective control construction risk.
Secondly, shield launching and trial excavation (refer to fig. 6);
the main working contents before shield starting are as follows: the construction method comprises the following steps of triaxial mixing pile construction and end soil body reinforcement, starting bracket installation, construction track laying, steel sleeve installation, shield tunneling machine assembling and debugging, reaction frame installation, tunnel door sealing, duct piece production, negative ring duct piece assembling and the like.
If the ground connecting wall of the enclosure structure at the tunnel portal is made of glass fiber ribs, the starting tunnel portal is a water-rich soft soil stratum with geology of mucky soil and mucky silty fine sand, and a steel sleeve with the length of 600mm is additionally arranged at the position of a steel ring of the tunnel portal for starting in consideration of starting risks.
The main technical points of shield initial tunneling are as follows:
(1) after the shield starts to pass through the end strengthening section, the shield machine enters an undisturbed soil layer from the soil layer after being improved and strengthened, namely a tunneling process from a hard soil layer to a soft soil layer (a soft soil layer or a sand layer). In the process from hard to soft, the phenomenon of 'head falling' is easy to generate due to the fact that the weight of the shield machine is mainly concentrated on the cutter head and the forebody. In the tunneling process, the starting attitude of the shield tunneling machine is that a front shield is raised by 30mm, a tail shield is raised by 10mm, and a starting base is in an upward slope which is increased by 3 per mill relative to a line, so that the upward movement trend of the shield tunneling machine is maintained.
(2) In order to prevent the cutter head from suddenly sinking, two short guide rails are laid in the tunnel door and used as extensions of the starting frame rail.
(3) In the process of separating the negative ring duct piece from the shield tail, in order to ensure that the position of the negative ring duct piece is correctly and stably installed, a wood wedge is adopted for wedging between the duct piece and the bracket, and meanwhile, each ring of duct piece is hooped by 1 phi 20 steel wire rope.
(4) In the segment assembling operation, the jacks are required to be correctly extended and retracted, the oil pressure and the number of the extended jacks are strictly controlled, and the shield is ensured not to retreat during assembling.
(5) In the initial stage, attention is paid to the control of the thrust and the torque, and the effective use of grease at each part is paid to the control. The total thrust does not exceed the reaction frame bearing capacity while ensuring that the torque produced by the cutter cutting into the formation at this thrust is less than the reaction torque provided by the originator.
(6) The shield machine is prevented rolling and is twisted: firstly, welding anti-rolling torsion steel plates on two sides of a middle shield and a tail shield of the shield tunneling machine before starting, arranging a specially-assigned person for observation, and cutting off the steel plates before the shield tunneling machine enters a hole. Secondly, the rolling angle of the cutter head is controlled during the starting stage of the shield, an operator timely adjusts the steering of the left and right rotating cutter heads, and the rolling angle of the cutter head is controlled within +/-3.
(7) Shield trial tunneling
The shield is started and enters into a test section for tunneling construction after being started, the test section tunneling is a process of mastering, searching and knowing the shield performance and the construction rule, therefore, in the distance construction, according to the requirement of controlling the ground deformation, ground surface deformation measuring mark points are arranged along the shield propulsion axis and the transverse section vertical to the axis, the subsidence deformation of the ground is tracked and measured during construction, and the construction parameters such as propulsion thrust, propulsion speed, shield front soil pressure, propulsion gradient, grouting pressure, quantity and the like are analyzed and adjusted to control the ground surface deformation in the minimum range, so that the optimized construction parameters and construction operation experience are obtained for the normal propulsion of the shield in the next stage. After the initial tunneling, the statistics of the tunneling parameters of the first 100 rings are as follows:
end reinforcing section (-3-ring to 4-ring) tunneling parameter
TABLE 5.2.2-2 excavation parameters of the reinforcing section (5-ring to 100-ring) of the outlet end
Three shield tunneling normally'
1 shield tunneling control program;
in shield tunneling, maintaining the balance between the pressure of the soil bin and the pressure of the working surface (the sum of the soil pressure and the water pressure) is an important factor for preventing the ground surface from settling and ensuring the safety of buildings.
(1) And (4) selecting a pressure value P of the soil bin. The P value can be in counterbalance with the stratum soil pressure and the hydrostatic pressure, the sum of the stratum hydrostatic pressure and the soil pressure in the center of the cutter head is P0, P is K multiplied by P0, K is generally 1.0-1.3, and feedback, adjustment and optimization are carried out according to the geological and buried depth conditions and the ground surface settlement monitoring information in the stratum tunneling process. The stable relation between the ground surface settlement and the working surface and corresponding measures and countermeasures are shown in the table.
TABLE 5.2.3-1 relationship between surface subsidence and working face stability and corresponding measures and countermeasures
(2) The pressure P of the soil bin is maintained mainly by maintaining the balance between the excavated soil volume and the soil discharge volume. The method can be achieved by setting the tunneling speed and adjusting the soil discharge amount or setting the soil discharge amount and adjusting the tunneling speed.
(3) Controlling the soil discharge amount;
the control of the soil discharge amount is one of key technologies when the shield works in the soil pressure balance working condition mode.
The discharge amount of the slag soil must be matched with the excavation amount of the tunneling machine so as to obtain a stable and proper supporting pressure value and enable the tunneling machine to work in an optimal state. When the ideal unearthed state can not be achieved by adjusting the rotating speed of the screw conveyor, the plastic flow state of the muck can be adjusted by improving.
2 normally tunneling main construction tunneling parameters;
(1) the shield is tunneled in a triaxial mixing pile reinforcing area, the tunnel is covered with soil for 10-20 m, and main tunneling parameters are as follows.
(2) The shield is tunneled in a deep water-rich soft soil layer, the tunnel is covered with soil for 20-24 m, and the main tunneling parameters are as follows.
3, normal tunneling quality control measures;
in the tunneling construction in the water-rich soft soil stratum, the posture of the shield machine is difficult to control, and the problems of the shield machine head planting, the whole sinking of the shield machine, the slag discharge and the spewing of the screw machine and the like are common. In order to ensure the engineering quality and the construction safety, the shield construction technical measures are as follows when the engineering shield passes through soft soil strata such as mucky soil, mucky fine sand, silty fine sand and the like:
(1) adjusting the vertical posture in advance before the reinforcing body is formed, and preventing the shield machine from head falling;
the shield posture is controlled in advance during tunneling in the soft stratum, the posture is lifted in advance, the upward head-up trend is kept, and the shield is prevented from sinking in the soft stratum. According to actual construction experience, the shield machine raises the head to +30mm of the shield head and the shield tail to +15mm before a reinforcing body is produced, a certain floating amount of a segment is considered when the shield machine tunnels in the reinforcing body, the vertical posture of the shield machine is generally controlled to be about-25 mm (bottom crossing parameters are adjusted according to actual segment posture measurement conditions), and in order to guarantee segment quality, the shield machine raises the head in a trend of +3 to +5mm/m before the reinforcing body is produced, so that the posture adjustment needs to be carried out in advance by 12-15 rings in a reinforcing area.
(2) Synchronous grouting: according to the increase of synchronous grouting amount, the stratum change adjusts the synchronous grouting mixing proportion, and in the weak water-rich stratum, the synchronous grouting amount is increased to 6.5-7.3 m3And the initial setting time of the slurry is shortened to 4h, and the gap between the tunnel and the segment is filled in time.
3) Secondary grouting: and (3) arranging to perform secondary grouting in time after the shield segment is separated from the shield tail, wherein the secondary grouting adopts double-liquid slurry, the initial setting time is controlled to be preferably 20-48 s, and secondary grouting is enhanced mainly for the position with abnormal ground settlement monitoring.
4) Reasonably selecting muck modifier, ensuring slag discharging effect and controlling slag discharging amount
In the soft stratum of mucky soil, the conventional mucky soil improvement foaming agent is adopted, the parameters of the foaming agent are properly adjusted, and the opening and the rotating speed of a screw machine are controlled, so that the slag discharging condition can be effectively controlled. However, in the soft water-rich sand layer, in order to control the screw machine spewing caused by slag segregation in the soil bin, high molecular polymer (polyacrylamide) is injected for slag improvement, so that the workability of the slag can be effectively improved, the spewing of the screw conveyor is prevented, and the control of the pressure and the soil output of the soil bin is facilitated.
In the process of tunneling a weak stratum, the soil discharging amount of each ring is controlled to be 54-59 m3And (4) making a ledger record to prevent the ground surface from settling due to over excavation (calculating according to 1.1-1.2 times of the theoretical soil output).
5) Strengthen the monitoring and inspection, establish the linkage management mechanism
The shield tunneling in the weak stratum is easy to cause the surface subsidence due to the disturbance of the soil body, and the surface monitoring and inspection needs to be enhanced in the construction process. And (3) establishing a monitoring linkage mechanism group, analyzing and discussing the daily monitoring condition by the construction unit, the supervision unit, the construction unit and the third-party monitoring unit together, and taking effective control measures in time when monitoring abnormity occurs. And issuing a construction tunneling instruction according to daily monitoring data feedback and the shield tunneling condition, and dynamically adjusting tunneling parameters.
6) Scientifically arrange the procedures and shorten the shutdown time
According to the monitoring condition of the shield tunneling period of the soft soil stratum section with small radius and large longitudinal slope, the position of the ground surface with large settlement is basically matched with the position of the shield for temporarily stopping the shield for a long time (more than 4 h), so that the direct relation between the ground surface settlement and the temporary stopping of the shield machine can be judged.
Fourthly, shield arrival construction;
1 shield arrival construction process (refer to fig. 7);
2, main tunneling construction parameters of a shield arrival section;
the main construction tunneling parameters of shield arrival section tunneling are shown in the following table.
Main construction tunneling parameter for shield arrival tunneling
3 shield arrival construction technical key point and measure
During the tunnel-out period of the shield machine, the problems of sudden change of the shield posture, head falling of the shield machine, dislocation of the segments, water burst and sand burst at the tunnel portal and the like are common. In order to ensure the engineering quality and the construction safety, the technical control measures adopted in the receiving stage of the engineering shield are as follows:
(1) and (4) reinforcing the receiving end, and strictly constructing according to the design and standard technical requirements to ensure the end reinforcement quality.
(2) Checking and accepting conditions before hole emergence: before the shield is out of the tunnel, a condition acceptance examination meeting is organized according to a condition acceptance requirement before a key link, technical parameters, receiving device installation, personnel arrangement, equipment conditions and emergency material preparation conditions before the shield is out of the tunnel are combed and accepted, and construction safety during the shield is ensured.
(3) The receiving device and the hole door sealing device are ensured to be installed stably.
(4) End precipitation and horizontal hole probing of a portal: before the shield reaches the receiving end, the water level monitoring is carried out by utilizing the standby dewatering well at the end in advance, and the water level height is required to be 1.0m below the tunnel bottom. And advanced exploration is carried out to find out the reinforcing of the receiving end head and the conditions of underground water and water leakage.
(5) Equipment maintenance before receiving: after the shield machine reaches the receiving end, the shield machine is temporarily stopped in the reinforcing area, the shield machine and the back supporting equipment are overhauled comprehensively and carefully once, and all the equipment of the shield machine are ensured to be in the optimal working state.
(6) Fixing a duct piece at the hole outlet section: 20 rings adopt 14# channel-section steel to weld and consolidate five positions of 3 points, 4 points, 8 points, 9 points and 12 points of the segment before the hole is out, thereby enhancing the integrity and stability of the segment and preventing the segment of the hole from staggering.
(7) Secondary grouting and water stop ring construction: and (3) performing full-ring secondary grouting at 20 rings before the hole is removed, wherein the secondary grouting adopts double-liquid slurry, 1-ring water stop rings are applied at intervals of 4 rings in principle, the grouting pressure is controlled to be 0.3-0.5 MPA, the gaps of the pipe pieces are filled, underground water flow is cut off, and synchronous grouting slurry channeling is controlled at the same time.
(8) Controlling out-of-tunnel tunneling parameters: the shield penetrates through the glass fiber reinforced plastic continuous wall, foam is increased, the cutter head sprays water, the soil bin is emptied, and the cutter head is cleaned.
(9) Controlling the hole-exiting posture: and (3) performing connection measurement before penetration 150m before shield receiving, and simultaneously measuring shield postures before 100m, 50m and hole exit respectively to ensure that the hole exit postures of the shield are consistent with the designed axis. Through measurement and check, the horizontal posture of the hole is controlled to be +/-5 mm, and the horizontal trend is as follows: 3mm/m, vertical attitude control at front point +30mm, vertical trend: and + 1- +3mm/m, the shield is lifted by 3cm when going out of the tunnel, the receiving frame is lowered by 1cm, the receiving attitude is ensured to be fitted with the center of the tunnel portal, the conflict between the elevation of the bottom of the cutter head and the elevation of the receiving frame is prevented, the shield machine is ensured to smoothly go up the receiving frame, and the shield is prevented from 'head falling'.
(10) Receiving a portal block (as shown in fig. 8): and (3) digging a hole in the water-rich soft soil stratum, and timely receiving an end head to take reinforcement measures, but the reinforcement water-stop effect cannot be guaranteed, so that a whole ring steel plate is pre-embedded in the end surface of the shield digging ring pipe piece in advance. After the last ring is installed, the tunnel portal can be immediately organized for plugging, the reserved steel plate of the hole outlet ring and the steel plate ring of the tunnel portal are utilized for welding and water stopping, and after welding, secondary grouting plugging is conducted on the organization.
Five, synchronous grouting slurry preparation and construction technology
1 synchronous grouting slurry preparation
(1) Proportioning of the slurries
In construction, different mixing ratios are selected and used according to shield crossing stratum conditions, underground water conditions, peripheral conditions and the like, and the most reasonable mixing ratio is determined by combining field tests as follows:
(2) main performance index of slurry
Gel time: the gel time is generally 4-6 h, and the proportion is changed through a field test to adjust the gel time according to the stratum condition and the tunneling speed.
Strength of the consolidated body: not less than 0.2MPa in one day, and not less than 3.75MPa in 28 days.
The calculus rate of serous fluid: > 95%, i.e. a consolidation shrinkage < 5%.
Slurry consistency: 8-13 cm
Slurry stability: the decantation rate (the ratio of the volume of floating water to the total volume after standing and precipitating) is less than 5 percent.
2 synchronous grouting method and process
(1) Grouting method
The shield tunneling is carried out simultaneously, the shield is carried out while a shield tail gap is formed by advancing the shield forward through a synchronous grouting system and a built-in grouting pipe of the shield tail, and the shield is symmetrically and simultaneously grouted by adopting double pumps and four pipelines (four injection points).
The grouting can be manually controlled according to the requirement, and the manual control mode is that the grouting flow, speed and pressure are manually adjusted at any time according to the tunneling condition. The slip casting process flow is shown in fig. 9.
(2) Device configuration
A mixing station: originating end well location installation 35m3And one mortar stirring station.
A synchronous grouting system: 2 hydraulic grouting pumps are arranged (arranged on a shield machine), and the grouting capacity is 2 multiplied by 10m3/h。
③ the transportation system: mortar tank truck (8 m)3) The self-stirring mortar pump has a self-stirring function and a mortar conveying pump. Are transported with the marshalling train.
3) Main technical parameters of synchronous grouting
Grouting pressure: the grouting pressure is slightly greater than the static water-soil pressure of the stratum position, and meanwhile, slurry is prevented from entering a soil bin of the shield tunneling machine. The initial grouting pressure is determined according to the theoretical static water-soil pressure and is continuously optimized in the actual tunneling process.
Grouting amount: and determining according to the excavation diameter of the cutter head and the outer diameter of the segment.
V＝π/4×K×L×(D12-D22)
In the formula: v-grouting amount per ring (m 3); L-Ring Width (1.5 m); d1-excavation diameter (6.48 m); d2-tube piece outer diameter (6.2 m); the K-expansion coefficient is 1.5 to 2.0.
Substituting the related data to obtain the synchronous grouting amount of 5.02m 3-6.69 m3 per ring.
Grouting time and speed: the grouting time is specifically controlled according to the grout with different setting times and the tunneling speed in different stratums. The synchronous tunneling and grouting, no grouting and no tunneling are realized. The synchronous grouting speed is matched with the tunneling speed, and the average grouting speed is determined according to the ring grouting amount completed within the time of completing one-ring tunneling by the shield.
Fourthly, checking the grouting finishing standard and the grouting effect: and adopting the dual index control standard of grouting pressure and grouting amount.
The grouting effect inspection mainly adopts an analytical method, namely, comprehensive evaluation is carried out by combining the monitoring results of the duct pieces, the ground surface and surrounding buildings according to a pressure-grouting amount-time curve.
Referring to fig. 10 and 11, in order to make grouting more uniform, a containing cavity is arranged at the tail end of the tail shield, a grout outlet pipe is communicated with the containing cavity, a rotary grout outlet ring is arranged in the containing cavity, a plurality of inclined holes are circumferentially distributed on the rotary grout outlet ring, one end of each inclined hole is communicated with the containing cavity, the other end of each inclined hole is communicated with a building gap, grout with pressure in the grout outlet pipe firstly enters the containing cavity and is introduced into the inclined holes of the rotary grout outlet ring through the containing cavity, the grout is injected into the building gap through the inclined holes, the grout can be pumped, the rotary grout outlet ring can be driven to rotate by matching the high pressure with the inclined holes, namely the rotary ring rotates on one side, and the inclined holes simultaneously discharge the grout, so that the building gap in the shape of the circumference can be filled with the grout, and the grout can be injected uniformly,
the synchronous slip casting thick liquid initial setting time who adopts in this application is about 6 ~ 8 hours, and the thick liquid fails in time initial setting, provides the space that floats for the section of jurisdiction, leads to the shield to construct the section of jurisdiction and drags out the emergence come-up behind the shield tail, when causing the shield section of jurisdiction to produce certain wrong platform, handles through following measure:
as shown in fig. 12, the boost pressure control: in a small-radius curve section of 350m left turn, the thrust difference of the oil cylinder is controlled to be 50-60 bar (the right side is larger than the left side), and the thrust is controlled to be 1300T-1600T, so that the overall thrust is reduced as much as possible, and the slow and fast turn is realized.
Active articulation control: the right side of the shield machine is properly extended out for active hinging, so that the shield machine is suitable for the left turning trend, the left side hinging is controlled to be 40-50 mm, the right side hinging is controlled to be 100-120 mm, the left and right side stroke difference is about 60mm through gradual adjustment, and the requirement of left turning R350m on small-radius curve section tunneling can be met.
Encrypting and adding the attendance and guiding system to measure the station shift: on average, 12-15 rings are used for carrying out one-time guide system station change (according to actual conditions), and the encryption manual retest frequency is 20-25 rings for one-time measurement, so that the axis error generated by the encryption manual retest frequency is avoided.
Optimizing segment selection: the theoretical proportion of segment model selection of the left-turn small-radius curve segment is L: and (3) selecting a turning ring splicing point location according to the actual condition, splicing the maximum wedge-shaped amount position of the turning ring at the right side of the shield tunneling direction in principle by a left-turning small-radius curve segment, wherein the selection of the point location needs to be confirmed by an operator and a civil engineering engineer together.
The shield tail clearance is surveyed to the duty: civil technicians divide the cycle into three times: before assembly, after assembly and in the tunneling process, shield tail clearance measurement is carried out, a basis is provided for duct piece selection, the shield tail clearance is controlled to be 70-50 mm, and the difference value of the upper shield tail clearance, the lower shield tail clearance and the left shield tail clearance is controlled to be 20 mm.
Adjusting the synchronous grouting proportion, properly shortening the initial setting time of the grout: and (3) determining proper grouting parameters by adjusting the slurry mixing ratio, and controlling the initial setting time of synchronous grouting slurry to be about 4 hours.
In order to solve the problem that the shield machine sinks in a weak stratum during the transition period from a reinforced area to a non-reinforced area, the shield machine adopts the following measures (refer to fig. 13):
firstly, high-concentration bentonite with the thickness of 1-2 m is injected into the bottom of the shield shell during tunneling3. The friction resistance of propulsion is reduced, and the stability of the lower sand layer soil body is enhanced simultaneously, so that the shield machine is prevented from sinking.
Secondly, the stroke of the propulsion oil cylinder and the clearance of the shield tail are adjusted by adopting a turning ring, the turning ring is properly adopted to replace a straight line ring, the maximum wedge-shaped amount of the pipe piece is assembled at the positions of the No. 5, 6 and 7 oil cylinders, and the small-radius turning requirement is considered while the head raising is matched. Namely, the left-turning K blocks are assembled in 15#, 1#, 2# oil cylinders (the right-turning K blocks are assembled in 12#, 11#, 9# oil cylinders), the stroke of the lower oil cylinder is reduced, the gap of the lower shield tail is increased (the gap of the upper shield tail is reduced), the lower part of the duct piece is advanced to the upper part, the upward trend of the duct piece is kept, and the head raising of a shield machine is matched;
and thirdly, properly adjusting the pressure of the soil bin (reducing about 0.3bar) in the tunneling process, controlling the pressure of the soil bin to be about 1.80-1.90 bar, reducing the soil accumulation in the soil bin, and reducing the self weight of the front shield so as to be matched with the head raising of the shield tunneling machine. And keeping the tunneling speed at 60-75 mm/min for rapid tunneling, and preventing the soil body from lagging and settling. Operators need to pay attention to the posture and soil pressure change in real time and control the slag digging amount to be 54-59 m3And (according to the excavation coefficient of 1.1-1.2 times), reporting the abnormal condition in time. And before each ring of tunneling is completed, the pressure of the soil bin is restored to 2.10bar so as to ensure the stability of the tunnel face during the process connection temporary halt period.
Controlling the upper thrust to be 40-60 bar, controlling the lower thrust to be 250-300 bar, keeping the pressure difference of the upper oil cylinder and the lower oil cylinder to be about 220bar, controlling the vertical trend to be more than 10mm/m, and keeping the head-up posture.
Fifthly, the synchronous grouting amount is increased to more than 160 percent of the theoretical value, and the grouting amount per ring is controlled to be 6.5 to E7.0m3And keeping the grouting speed after the wall and the tunneling speed synchronous. And increasing the lower grouting pressure to 3.0-4.0 bar during the tunneling period, so that the lower grouting pressure is greater than the upper grouting pressure, and matching with the head raising of the shield tunneling machine.
Sixthly, performing secondary grouting at the position of 5 rings behind the shield tail in time during tunneling to prevent the duct piece from settling;
seventhly, reasonably organizing a procedure connection flow, accelerating the assembling speed of the segments and keeping continuous and stable propulsion. During the tunneling, the cutter head is prevented from idling and disturbing the soil body as much as possible.
For preventing the spiral conveyer from gushing, the following targeted design is carried out on the earth pressure balance shield machine:
firstly, the screw machine adopts a double-gate design, and utilizes the labyrinth seal principle to be alternately opened so as to reduce the surging pressure;
and secondly, reserving an injection interface of bentonite and high molecular polymer, and injecting the bentonite or the high molecular polymer into the soil bin wall and the screw machine so as to relieve the slag spraying pressure of the screw machine.
And a pressure maintaining pump interface is arranged, and a slurry pump or a slurry pipe can be connected when necessary to relieve the slag spraying pressure.
Improving the residue soil:
during the shield tunnel passes through the soft water-rich sand layer, aiming at the condition of slag discharge and spewing of the screw conveyor, high molecular polymer (polyacrylamide) is injected for slag improvement, the high molecular polymer and water are mixed according to the mass ratio of 1:400 to form a solution, the using amount of each ring of high molecular polymer is about 5-8 kg, and the solution is injected into a soil bin through a bentonite system, so that the workability of the slag is effectively improved, and the effect of preventing spewing of the screw conveyor is achieved.
The slag gushing phenomenon is effectively controlled by taking measures of improving the slag soil. The condition that an emergency pressure maintaining pump needs to be adopted does not occur.
And the high molecular polymer solution is used along with the preparation, stirring and puffing are not needed, and the preparation is convenient. The additive dosage is small, and the material consumption cost is lower compared with that of bentonite.
The construction method has the following advantages:
1. reasonable selection shield equipment
1) If the whole opening rate of the cutter head of the shield tunneling machine is 50%, the openings are uniformly distributed on the whole disk surface, and mud cakes are prevented from being generated in the process of tunneling.
2) The shield constructs the machine unearthing mouth and sets up 2 gates, opens in turn in order to reduce the gushing pressure.
3) 2 bentonite pumps are configured for improving the slag soil, and the two pumps can be injected into the front part of the cutter head through a single pipeline or can be injected out of the hole shell all the way.
2. Combining the data monitored by the shield construction information, the judgment of the actual soil output and the soil output state, summarizing the excavation rules of the earth pressure balance shield machine under the geological condition, such as reasonable setting ranges of the pressure, the torque, the synchronous grouting mix proportion selection, the grouting quantity control and other parameters of an excavation face soil bin, and reasonably improving the muck. The earth pressure balance shield can completely meet the construction requirements under the special hydrogeological conditions.
3. In the construction, different muck modifying agents and material proportions are selected and used according to specific hydrogeological conditions, the muck modifying effect is optimized, for example, high molecular polymers and the like are adopted for muck modification, compared with the traditional foam muck modifying mode, the cohesiveness and the workability of muck are improved, and the occurrence of the gushing condition of the earth pressure shield in the water-rich soft soil stratum is effectively controlled.
4. The subway engineering soft soil stratum earth pressure shield construction method has the characteristics of high construction quality, high construction progress and small influence of construction safety on the ground.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (10)
1. A subway engineering soft soil stratum earth pressure balance shield construction method is characterized in that:
firstly, selecting a type of a shield tunneling machine:
(1) the shield machine soil outlet is provided with 2 gates which are opened alternately to reduce the gushing pressure; a bentonite and high molecular polymer injection interface is reserved; is provided with a pressure maintaining pump interface
(2) 2 bentonite pumps are configured for improving the slag soil, and the two pumps can be injected into the front part of the cutter head through a single pipeline or can be injected out of the hole shell through one pipeline;
(3) selecting a belt conveyor with a small inclination angle of 10 degrees;
10 advanced grouting holes are designed in the circumferential direction of the shield body, wherein the upper part is 6, the lower part is 4, and the front shield partition plate is provided with 7 horizontal advanced grouting holes; advanced grouting can be performed in front of the excavation surface to perform geological reinforcement;
secondly, shield launching and tunneling:
(1) the starting attitude of the shield machine is that the front shield is 25-35mm in head-up, the tail shield is 8-12mm in head-up, and the starting base is an ascending slope which is increased by 2-4 per mill relative to the line so as to keep the upward movement trend of the shield machine;
(2) two short guide rails are laid in the tunnel door and used as extensions of the starting frame rail
(3) In the process of separating the negative ring duct pieces from the shield tail, wood wedges are adopted for wedging between the duct pieces and the brackets, and simultaneously, each ring duct piece is hoop-tightened by 1 steel wire rope;
(4) before starting, welding anti-rolling torsion steel plates on two sides of a middle shield and a tail shield of the shield machine, and controlling the rolling angle of a cutter head within +/-3 degrees by timely adjusting the steering of a left rotating cutter head and a right rotating cutter head by operators;
thirdly, shield tunneling trial: laying ground surface deformation measuring mark points along a shield propulsion axis and a transverse section vertical to the axis, tracking and measuring the settlement deformation of the ground during construction, and analyzing and adjusting construction parameters, wherein the construction parameters comprise propulsion thrust, propulsion speed, shield front soil pressure, propulsion gradient, grouting pressure and quantity so as to control the ground surface deformation in a minimum range, thereby obtaining optimized construction parameters for the normal propulsion of the shield at the next stage;
fourthly, normally tunneling the shield:
(1) selecting a soil bin pressure value P;
the P value can counterbalance the stratum soil pressure and the hydrostatic pressure, and if the sum of the hydrostatic pressure and the soil pressure of the stratum in the center of the cutter head is P0, the P is KxP 0, and K is 1.0-1.3;
(2) maintaining the pressure P of the soil bin by maintaining the balance of the excavated soil volume and the soil discharge volume; synchronous grouting: adjusting the synchronous grouting mix proportion according to the increase of the synchronous grouting amount and the stratum change, increasing the synchronous grouting amount to 6.5-7.3 m for carrying out top-load transportation in a weak water-rich stratum, shortening the initial setting time of the slurry to 4h, and filling the gap between the tunnel and the segment in time;
(3) secondary grouting: arranging secondary grouting in time after the shield segment is separated from the shield tail 5 rings, wherein the secondary grouting adopts double-liquid slurry, and the initial setting time is controlled to be 20-48 s;
(4) the slag soil is improved, a slag soil improvement foaming agent is adopted in a soft stratum of mucky soil, and the opening and the rotating speed of a screw machine are controlled, so that the slag discharging condition can be effectively controlled;
in the soft water-rich sand layer, in order to control the screw machine gushing caused by slag segregation in the soil bin, high molecular polymer is injected to improve the slag;
the shield arrives.
2. The subway engineering soft soil stratum earth pressure balance shield construction method according to claim 1, characterized in that: the cutter head adopts a structural form of 4 main beams and 4 auxiliary beams, and the integral opening rate is 50%; the cutter head panel is provided with 6 paths of single-pipe single-pump single nozzles, the nozzles adopt a back-mounted replaceable design, and a central area is provided with 3 paths of single-pipe single-pump modifier injection ports; the cutter head is provided with 4 active stirring rods which are distributed on two tracks.
3. The subway engineering soft soil stratum earth pressure balance shield construction method according to claim 2, characterized in that: the shield is provided with a 4-path single-pipe single-pump single-nozzle foam injection system.
4. The subway engineering soft soil stratum earth pressure balance shield construction method according to claim 3, characterized in that: 2 bentonite pumps are configured for improving the residue soil; the two pumps can be injected into the front part of the cutter head through a single pipeline, can also be injected out of the shield shell all the way, and can be matched with the head raising of the shield machine when the head falling condition of the shield machine occurs.
5. The subway engineering soft soil stratum earth pressure balance shield construction method according to claim 4, characterized in that: the hinged seal of the shield tunneling machine is a double-finger polyurethane rubber combination, an emergency sealing air bag and an emergency polyurethane grease injection system; the shield tail design adopts 3 steel wire brushes, 1 steel plate brush and 4 polyurethane injection holes, so that the shield tail sealing design value is increased to 6bar, and the 4 emergency polyurethane injection systems inject polyurethane under the emergency condition of water burst and sand burst of the shield tail.
6. The subway engineering soft soil stratum earth pressure balance shield construction method according to claim 5, characterized in that: the shield arrival construction process sequentially comprises end reinforcement, end precipitation, horizontal hole probing, mounting of a receiving base, mounting of a tunnel door seal, tunneling of an arrival section and stepping on the receiving base after penetration.
7. The subway engineering soft soil stratum earth pressure balance shield construction method according to claim 6, characterized in that: performing full-ring secondary grouting at 20 rings before the tunnel is out, wherein the secondary grouting adopts double-liquid slurry, 1-ring water-stop rings are applied at intervals of 4 rings in principle, the grouting pressure is controlled to be 0.3-0.5 MPA, the gaps of the pipe pieces are filled, underground water flow is cut off, and meanwhile, synchronous grouting slurry channeling is controlled; before receiving the shield, 150m is used for performing communication measurement, and simultaneously, the shield postures are respectively measured before 100m, 50m and exit, so that the exit postures of the shield are ensured to be consistent with the designed axis;
through measurement and check, the horizontal posture of the hole is controlled to be +/-5 mm, and the horizontal trend is as follows: 3mm/m, vertical attitude control at front point +30mm, vertical trend: and +1 to +3mm/m, the shield is lifted for 3cm in the tunnel-out posture, the receiving frame is lowered for 1cm, the receiving posture is ensured to be fitted with the center of the tunnel portal, the conflict between the elevation of the bottom of the cutter head and the elevation of the receiving frame is prevented, the shield machine is ensured to smoothly go up the receiving frame, and the shield is prevented from 'planting heads'.
8. The subway engineering soft soil stratum earth pressure balance shield construction method according to claim 7, characterized in that: when the small radius section tunnels the duct piece, the propelling pressure is controlled: in a small-radius curve section of 350m left turn, the thrust difference of the oil cylinder is controlled to be 50-60 bar, the thrust is controlled to be 1300T-1600T, and slow and fast turn is realized; the right side is properly extended out for active hinging so as to be suitable for the left turning trend of the shield machine, the left side hinging is controlled to be 40-50 mm, the right side hinging is controlled to be 100-120 mm, and the left-right side stroke difference is about 60mm through gradual adjustment; encrypting and adding the attendance and guiding system to measure the station shift: performing guide system station change for 12-15 rings on average, wherein the encryption manual retest frequency is 20-25 rings for one test; three times per cycle: before assembly, after assembly and in the tunneling process, shield tail clearance measurement is carried out, a basis is provided for segment selection, the shield tail clearance is controlled to be 70-50 mm, and the difference value of the upper shield tail clearance, the lower shield tail clearance and the left shield tail clearance is controlled to be 20 mm; adjusting the synchronous grouting proportion, properly shortening the initial setting time of the grout: and (3) determining proper grouting parameters by adjusting the slurry mixing ratio, and controlling the initial setting time of synchronous grouting slurry to be 4 hours.
9. The subway engineering soft soil stratum earth pressure balance shield construction method according to claim 8, characterized in that: when the shield passes through the water-rich sand layer to remove slag and spout, the screw machine adopts double gates to be opened alternatively to reduce the spouting pressure, bentonite or high molecular polymer is injected into the soil bin wall and the screw machine through the reserved bentonite and high molecular polymer injection interface to relieve the slag spraying pressure of the screw machine, and a slurry pump or a slurry pipe can be connected through the pressure maintaining pump interface of the screw machine to relieve the slag spraying pressure.
10. The subway engineering soft soil stratum earth pressure balance shield construction method according to claim 9, characterized in that: the tail shield is provided with a rotary slurry outlet ring, the rotary slurry outlet ring is provided with an inclined slurry outlet hole, and slurry is discharged through rotation of slurry pressure.
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| CN114017041B (en) * | 2021-09-26 | 2024-01-30 | 深圳市政集团有限公司 | Monitoring method for shield tail pressure balance |
| CN113982611B (en) * | 2021-10-27 | 2022-08-12 | 无锡中铁城轨装备有限公司 | Shield constructs cutter head convenient to tool changing |
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| WO1990013733A1 (en) * | 1989-04-28 | 1990-11-15 | Kabushiki Kaisha Konoike Gumi | Earth pressure system shield process |
| CN100543270C (en) * | 2008-08-04 | 2009-09-23 | 中铁十一局集团城市轨道工程有限公司 | The job practices of composite soil pressure balance tunnel shielding machine for traversing shallow-buried water-rich sand layer |
| CN101509381B (en) * | 2008-12-24 | 2011-07-27 | 中铁隧道集团有限公司 | Composite shield structure suitable for complicated stratum construction |
| CN107605496A (en) * | 2017-08-07 | 2018-01-19 | 北京市市政四建设工程有限责任公司 | A kind of tail sealing device of shield |
| CN108590678B (en) * | 2018-04-08 | 2019-10-18 | 中交一公局桥隧工程有限公司 | Based on the construction method for wearing multiply road railway under shallow embedding Soft Soil Layer earth pressure balanced shield, EPBS |
| CN109882190B (en) * | 2019-04-11 | 2020-06-19 | 中铁工程装备集团有限公司 | Multi-mode closed TBM suitable for long and large mountain tunnel and construction method thereof |
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