CN110566217A - shallow-earth-covered shield construction method - Google Patents
shallow-earth-covered shield construction method Download PDFInfo
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- CN110566217A CN110566217A CN201910973669.1A CN201910973669A CN110566217A CN 110566217 A CN110566217 A CN 110566217A CN 201910973669 A CN201910973669 A CN 201910973669A CN 110566217 A CN110566217 A CN 110566217A
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- 238000010276 construction Methods 0.000 title claims abstract description 55
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 47
- 238000007789 sealing Methods 0.000 claims abstract description 30
- 230000005641 tunneling Effects 0.000 claims abstract description 30
- 230000002787 reinforcement Effects 0.000 claims abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 22
- 230000008569 process Effects 0.000 claims abstract description 16
- 238000001556 precipitation Methods 0.000 claims abstract description 15
- 239000004519 grease Substances 0.000 claims abstract description 11
- 238000011049 filling Methods 0.000 claims abstract description 8
- 238000006243 chemical reaction Methods 0.000 claims abstract description 7
- 230000003014 reinforcing effect Effects 0.000 claims description 54
- 239000002689 soil Substances 0.000 claims description 40
- 239000004744 fabric Substances 0.000 claims description 15
- 238000003756 stirring Methods 0.000 claims description 15
- 238000002156 mixing Methods 0.000 claims description 14
- 238000012360 testing method Methods 0.000 claims description 12
- 230000002093 peripheral effect Effects 0.000 claims description 11
- 239000007787 solid Substances 0.000 claims description 10
- 238000013461 design Methods 0.000 claims description 8
- 230000005484 gravity Effects 0.000 claims description 8
- 230000008859 change Effects 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 6
- 238000003825 pressing Methods 0.000 claims description 6
- 238000002347 injection Methods 0.000 claims description 5
- 239000007924 injection Substances 0.000 claims description 5
- 238000012544 monitoring process Methods 0.000 claims description 5
- 239000004927 clay Substances 0.000 claims description 4
- 239000004568 cement Substances 0.000 claims description 3
- 238000007689 inspection Methods 0.000 claims description 3
- 238000005259 measurement Methods 0.000 claims description 3
- 230000008439 repair process Effects 0.000 claims description 3
- 230000002441 reversible effect Effects 0.000 claims description 3
- 238000005507 spraying Methods 0.000 claims description 3
- 238000003466 welding Methods 0.000 claims description 3
- 230000000977 initiatory effect Effects 0.000 claims 1
- 238000009412 basement excavation Methods 0.000 abstract description 17
- 239000002002 slurry Substances 0.000 description 17
- 239000010802 sludge Substances 0.000 description 9
- 238000007599 discharging Methods 0.000 description 6
- 238000009434 installation Methods 0.000 description 5
- 239000004576 sand Substances 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 4
- 230000001360 synchronised effect Effects 0.000 description 4
- 238000009933 burial Methods 0.000 description 3
- 239000011440 grout Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007667 floating Methods 0.000 description 2
- 239000003673 groundwater Substances 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 235000019353 potassium silicate Nutrition 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK 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
- E21D11/38—Waterproofing; Heat insulating; Soundproofing; Electric insulating
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK 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
- E21D9/001—Improving soil or rock, e.g. by freezing; Injections
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK 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
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK 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
- E21D9/14—Layout of tunnels or galleries; Constructional features of tunnels or galleries, not otherwise provided for, e.g. portals, day-light attenuation at tunnel openings
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F16/00—Drainage
- E21F16/02—Drainage of tunnels
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- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Environmental & Geological Engineering (AREA)
- Structural Engineering (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Soil Sciences (AREA)
- Lining And Supports For Tunnels (AREA)
Abstract
the invention discloses a shallow earth covering shield construction method, which sequentially comprises the following steps: constructing an initial well; starting section reinforcement and precipitation: the initial section reinforcement comprises initial section end reinforcement and stratum reinforcement; constructing a precipitation well after the initial section is reinforced, so that the shield can be precipitated below the bottom of the tunnel in advance before the initial section and the initial section are reached; constructing an originating station; assembling and debugging the shield; installing a reaction frame and a supporting structure; installing a tunnel door sealing device: the sealing device comprises a first seal fixed on a ring frame pre-embedded at the opening and a second seal fixedly connected with the first seal through a sealing ring pipe; a grease filling hole is formed in the middle of the sealing ring; chiseling a tunnel portal; installing a negative ring duct piece, and pushing a shield until the cutter head contacts the tunnel face; the muddy water bin establishes a balance pressure; and (5) circularly tunneling the shield. The invention solves the problems of difficult control of the shield attitude in the shallow earthing construction process, avoids the collapse of the excavation surface, improves the construction safety and accelerates the tunneling speed.
Description
Technical Field
The invention relates to the technical field of tunnel construction, in particular to a shallow earth covering shield construction method.
background
The shield construction difficulty of the soft soil shallow-buried section is controlling the shield posture, and the phenomena of upward drifting and slurry overflow easily occur in the construction process, and the collapse of the excavation surface is caused by the loss of the soil body on the front surface of the excavation surface due to the pressure fluctuation of the cut.
the shield is tunneled in shallow covering sludge and sludge soft soil, the sludge and sludge soft soil has large pore ratio, high sensitivity and thin covering layer. The shield posture is difficult to control in the construction, the seam of the segment leaks water and slurry, the quality of the formed tunnel is influenced, and the tunnel face collapses when the condition is serious.
Disclosure of Invention
In view of the above, the present invention provides a shallow earth covering shield construction method, which solves the problems of difficult control of shield attitude during shallow earth covering construction, avoiding collapse of excavation surface, improving construction safety, and accelerating tunneling speed.
In order to achieve the purpose, the invention adopts the following technical scheme:
a shallow soil covering shield construction method comprises the following steps:
1) constructing an initial well: the shield starting well is constructed by adopting an open-cut reverse construction method, a foundation pit enclosure structure of the starting well adopts a ground connecting wall with the thickness of 1200mm, six inclined concrete supports are vertically arranged, a temporary central pillar is arranged in the middle, and a bored pile with the diameter of phi 1200mm is arranged below the temporary central pillar;
2) Starting section reinforcement and precipitation: the initial section reinforcement comprises initial section end reinforcement and stratum reinforcement; constructing a precipitation well after the initial section is reinforced, so that the shield can be precipitated below the bottom of the tunnel in advance before the initial section and the initial section are reached;
3) Construction of an originating station: the method comprises the following steps that concrete is poured into an originating station, the shield originating station is positioned according to a control point of measurement lofting, and a base of the originating station is of an arc-shaped structure; reserving grooves in two longitudinal channels of the starting base, reserving a groove in one transverse channel, and reserving an operation space for shield assembly welding;
4) assembling and debugging the shield;
5) Installing a reaction frame and a supporting structure;
6) installing a tunnel door sealing device: the sealing device comprises a first seal fixed on a ring frame pre-embedded at the hole and a second seal fixedly connected with the first seal through a sealing ring pipe, and a stiffened plate with one end connected with the hole is fixed on the sealing ring pipe; the first seal and the second seal are arranged in parallel and are spaced by 500 mm; a grease filling hole is formed in the middle of the sealing ring pipe;
7) chiseling a tunnel portal;
8) installing a negative ring duct piece, and pushing a shield until the cutter head contacts the tunnel face;
9) the muddy water bin establishes a balance pressure: setting the water pressure of the notch according to a design value, carrying out corresponding adjustment according to the water level change condition at the propulsion moment, and strictly controlling the fluctuation value of the muddy water pressure to control the fluctuation value of the muddy water pressure within-0.2 bar to +0.2 bar;
10) And (5) circularly tunneling the shield.
Preferably, the temporary central pillar in step 1) is a 460mm × 460mm lattice column.
preferably, the reinforcing of the end of the originating section in the step 2) comprises the following steps:
Firstly, adopting C25 plain concrete to construct a peripheral structure of an initial reinforcing area on one side of a foundation pit support structure of an initial well, which is positioned at a tunnel portal, so as to form a 3-surface plain concrete continuous wall, and enclosing the 3-surface plain concrete continuous wall and the initial well support structure to form a shield initial reinforcing area;
Constructing a first tunnel portal reinforcing area at a tunnel portal in the shield initial reinforcing area, wherein the first tunnel portal reinforcing area is a plain concrete continuous wall with the thickness of 1 m;
Thirdly, constructing a second hole reinforcing area on the outer surface of the first hole reinforcing area by adopting a three-row phi 1200@800mm high-pressure rotary spraying reinforcing mode, and constructing a third hole reinforcing area on the outer sides of the starting well enclosure structure and the peripheral structure of the starting reinforcing area; the third hole door reinforcing area is triangular, one side surface of the third hole door reinforcing area is fixedly connected with the originating well enclosure structure, and the bottom of the third hole door reinforcing area is fixedly connected with the peripheral structure of the originating reinforcing area;
Fourthly, reinforcing the bottom in the shield starting reinforcing area by adopting a triaxial mixing pile.
preferably, the construction process of the triaxial mixing pile in the step (iv) is as follows: firstly, making a test pile, and after the test is successful, making large-area construction; and after the reinforcement and construction of the triaxial mixing pile are finished, core-pulling inspection is carried out on the occlusion part of the triaxial mixing pile according to the proportion of 3%, and unqualified pile repair is continued until the pile is qualified.
preferably, the test parameters of the test pile are as follows: the cement injection amount is 538.2kg/m, the grouting pressure is 4-7bar, the drill rod lifting speed is 0.5-1.0m/min, and the stirring sinking speed is 0.1-0.5 m/min; the diameter of each three-axis stirring pile is 850mm, and the three-axis stirring piles are adjacent to each other to form an inter-pile occlusion area, so that the distance between the centers of circles of the three-axis stirring piles is 600 mm.
preferably, a rotary jet grouting pile is arranged between the plain concrete continuous wall and the three-axis stirring pile, a horizontal hole is drilled in the portal, the portal grouting effect is checked, and grouting needs to be continued when the requirements cannot be met until the design requirements are met.
Preferably, the dewatering well in the step 2) is implemented by adopting an impact hole-forming construction process, a filter pipe is arranged below the dewatering well, and the filter pipe is connected with a solid pipe; the bottom of the solid pipe is positioned 5m below the ground surface, and clay is filled between the solid pipe and the dewatering well; filling gravel between the filter pipe and the dewatering well; the diameter of precipitation well is 600mm, precipitation well's bottom plate is located 2000mm below the tunnel bottom line.
Preferably, the step 4) comprises the steps of assembling site preparation → starting preparation → crane assembling in place → rear matching trailer hoisting and pipeline connection → host hoisting and connection → installation reaction frame → host positioning and rear matching connection → no-load debugging → installation of a negative ring pipe piece → load debugging.
preferably, the first seal in step 6) comprises a first rubber curtain cloth hung on the ring frame and fixed by a first ring plate, and a first turning plate is rotatably connected to the bottom of the first ring plate; the second seal comprises a pressing plate fixedly connected with the stiffened plate and the outer side of the sealing ring pipe, and a second rubber curtain cloth hung on the pressing plate through bolts, the second rubber curtain cloth is fixed through a second ring plate, and a second turning plate is rotatably connected to the bottom of the second ring plate.
preferably, in the step 10), the pressure value of the top in the cabin is 0-1.46bar, the ground monitoring frequency is 2 times/2 h, the thrust is 3500-6500t, the tunneling speed is 5-10mm, the rotating speed of a cutter head is 0.5-1.0r/min, the torque of the cutter head is 2000-6000Kn.m, the grouting pressure is 2-3bar, and the grouting specific gravity is 1.05-1.08g/cm in the shield tunneling process3Discharging the slurrythe specific gravity is 1.08-1.25g/cm3。
the invention has the beneficial effects that:
The temporary tunnel portal sealing device is arranged when the shield starts to effectively prevent soil, underground water and circulating slurry from flowing out from the gap between the shield shell and the tunnel portal when the shield starts to tunnel, and prevent the shield tail from flowing out through the back lining grouting slurry of the tunnel portal; before the shield machine enters the reserved hole door, lubricating oil is coated on the peripheral cutter head and the outer side of the rubber curtain cloth so as to prevent the cutter head of the shield machine from breaking the rubber curtain cloth to influence the sealing effect.
After the shield cutter head completely passes through the second seal, pressurizing the slurry bin, wherein the pressure only meets the requirement that slurry is filled in the slurry bin, then injecting grease into the space between the two rubber curtain cloth seals by using a reserved grease injection hole between the two seals, and after the shield tail of the shield machine passes through the first seal and a turning plate is turned downwards, injecting grease inwards by using the grease injection hole in time, so that the grease pressure is always lower than the slurry pressure by 0.01 MPa; when the shield tail passes through the second seal and the turning plate turns downwards, grease is further added, so that the temporary seal of the tunnel portal has a good waterproof effect, the shield can be started smoothly, and the stratum loss during starting is reduced.
setting the water pressure of the cut according to a design value, carrying out corresponding adjustment according to the water level change condition at the propulsion moment, strictly controlling the fluctuation value of the muddy water pressure, and preventing soil body collapse caused by the fact that the soil body on the excavation surface cannot be supported due to low water pressure of the cut; the situation that the soil body collapses due to the fact that the water pressure of the notch is high and the soil body is disturbed excessively is prevented; the mud water pressure fluctuation value is controlled between-0.2 bar and +0.2bar, so that the pressure fluctuation is prevented from puncturing a seabed shallow covering soft soil layer, and the construction safety is improved.
The starting section end reinforcement provides stable stratum conditions for the starting of the shield to ensure safe and smooth starting on one hand, and provides enough foundation bearing capacity for the hoisting of the shield to ensure the safety of a crane in the hoisting operation process during the assembling of the shield on the other hand.
the stirring pile is reinforced, so that when the shallow soil covering layer is started and received, the water permeable channel and the water gushing and sand gushing are not easy to occur, and the safety of engineering and personnel is improved.
Drawings
FIG. 1 is a schematic structural view of originating end reinforcement;
FIG. 2 is a schematic view of mixing pile reinforcement;
FIG. 3 is a schematic structural diagram of a dewatering well;
Fig. 4 is a schematic structural view of the hole door sealing device of the present invention.
In the figure: the method comprises the following steps of 1 foundation pit support structure, 2 holes, 3 third hole reinforcing areas, 4 first hole reinforcing areas, 5 second hole reinforcing areas, 6 initial reinforcing area peripheral structures, 7 shield initial reinforcing areas, 21 inter-pile meshing areas, 31 earth surface, 32 solid pipes, 33 filter pipes, 34 tunnel bottom lines, 35 gravels, 36 clay, 41 ring frames, 42 reinforcing plates, 43 first ring plates, 44 first rubber curtain cloth, 45 first turning plates, 46 grease filling holes, 47 pressing plates, 48 second ring plates, 49 sealing ring pipes and 50 second rubber curtain cloth.
the arrows in fig. 1 indicate the heading direction.
Detailed Description
The invention is further described below with reference to the figures and examples.
a shallow soil covering shield construction method comprises the following steps:
1) Constructing an initial well: the shield starting well is constructed by adopting an open cut reverse construction method, a foundation pit enclosure structure 1 of the starting well adopts a ground connecting wall with the thickness of 1200mm, six inclined concrete supports are vertically arranged, a temporary middle upright post is arranged in the middle, and the temporary middle upright post adopts a lattice column of 460mm multiplied by 460 mm; a drill pile with the diameter of phi 1200mm is arranged below the temporary middle upright post;
2) Starting section reinforcement and precipitation: the initial section reinforcement comprises initial section end reinforcement and stratum reinforcement; constructing a precipitation well after the initial section is reinforced, so that the shield can be precipitated below the bottom of the tunnel in advance before the initial section and the initial section are reached;
the structure for reinforcing the end head of the starting section is shown in figure 1, and the construction process comprises the following steps:
Firstly, constructing a starting reinforcing area peripheral structure 6 on one side of a foundation pit support structure 1 of a starting well, which is positioned at a tunnel portal, by using C25 plain concrete to form a 3-surface plain concrete continuous wall, and enclosing the 3-surface plain concrete continuous wall and the starting well support structure to form a shield starting reinforcing area 7;
constructing a first tunnel portal reinforcing area 4 at the tunnel portal in the shield starting reinforcing area 7, wherein the first tunnel portal reinforcing area 4 is a plain concrete continuous wall with the thickness of 1 m;
Thirdly, constructing a second hole door reinforcing area 5 on the outer surface of the first hole door reinforcing area 4 by adopting a 3-row phi 1200@800mm triple pipe high-pressure rotary spraying reinforcing mode, and constructing a third hole door reinforcing area 3 on the outer sides of an originating well enclosure structure and an originating reinforcing area peripheral structure 6; the third portal reinforcement area 3 is triangular, one side surface of the third portal reinforcement area is fixedly connected with the starting well enclosure structure, and the bottom of the third portal reinforcement area is fixedly connected with the starting reinforcement area peripheral structure 6;
Fourthly, reinforcing the bottom in the shield starting reinforcing area 7 by adopting a triaxial mixing pile.
The schematic diagram of the triaxial mixing pile reinforcement is shown in fig. 2, and the construction process comprises the following steps: firstly, making a test pile, and after the test is successful, making large-area construction; and after the reinforcement and construction of the triaxial mixing pile are finished, core-pulling inspection is carried out on the occlusion part of the triaxial mixing pile according to the proportion of 3%, and unqualified pile repair is continued until the pile is qualified. Wherein the test parameters of the test pile are as follows: the cement injection amount is 538.2kg/m, the grouting pressure is 4-7bar, the drill rod lifting speed is 0.5-1.0m/min, and the stirring sinking speed is 0.1-0.5 m/min; the diameter of each three-axis stirring pile is 850mm, and the three-axis stirring piles are adjacent to each other to form an inter-pile meshing area 21, so that the distance between the centers of circles of the three-axis stirring piles is 600 mm.
as shown in fig. 3, the dewatering well is implemented by adopting an impact hole-forming construction process, a filter pipe 33 is arranged below the dewatering well, and a solid pipe 32 is connected to the filter pipe 33; the bottom of the solid pipe 32 is located 5m below the ground surface 31, and clay 36 is filled between the solid pipe 32 and the precipitation well; filling gravel 35 between the filter pipe 33 and the dewatering well; the diameter of precipitation well is 600mm, the bottom plate of precipitation well is located 2000mm below tunnel bottom line 34.
3) Construction of an originating station: the method comprises the following steps that concrete is poured into an originating station, the shield originating station is positioned according to a control point of measurement lofting, and a base of the originating station is of an arc-shaped structure; reserving grooves in two longitudinal channels of the starting base, reserving a groove in one transverse channel, and reserving an operation space for shield assembly welding;
4) assembling and debugging the shield; the method comprises the steps of assembly site preparation → starting preparation → crane assembly in place → rear matching trailer hoisting and pipeline connection → host hoisting and connection → installation of reaction frame → host positioning and rear matching connection → no-load debugging → installation of negative ring pipe piece → load debugging.
5) Installing a reaction frame and a supporting structure;
6) Installing a tunnel door sealing device: the sealing device comprises a first seal fixed on a ring frame 41 pre-embedded at the hole 2 and a second seal fixedly connected with the first seal through a sealing ring pipe 49, and a reinforcing plate 42 with one end connected with the hole 2 is fixed on the sealing ring pipe 49; the first seal and the second seal are arranged in parallel and are spaced by 500 mm; a grease filling hole 46 is formed in the middle of the sealing ring pipe 49;
In the step 6), the first seal comprises a first rubber curtain cloth 44 hung on the ring frame 41 and fixed through a first ring plate 43, and a first turning plate 45 is rotatably connected to the bottom of the first ring plate 43; the second seal comprises a pressure plate 47 fixedly connected with the stiffened plate 42 and the outer side of a sealing ring pipe 49, and a second rubber curtain cloth 50 hung on the pressure plate 47 through bolts, wherein the second rubber curtain cloth 50 is fixed through a second ring plate 48, and a second turning plate is rotatably connected at the bottom of the second ring plate 48.
7) chiseling a tunnel portal; in a conventional chiseling manner.
8) Installing a negative ring duct piece, and pushing a shield until the cutter head contacts the tunnel face; in order to reduce out-of-round influence of the negative ring pipe piece, the negative ring pipe piece is assembled in a staggered joint mode.
9) The muddy water bin establishes a balance pressure: setting the water pressure of the notch according to a design value, carrying out corresponding adjustment according to the water level change condition at the propulsion moment, and strictly controlling the fluctuation value of the muddy water pressure to control the fluctuation value of the muddy water pressure within-0.2 bar to +0.2 bar;
10) Circularly tunneling the shield; when the shield starts, the top of the shield is positioned in the silt layer, and the maximum burial depth is 8 m; at the time of arrivalThe shield is positioned in the silt and sand layer, and the top of the shield is buried by 12 m; in the shield tunneling process, the top pressure value in the cabin is 0-1.46bar, the ground monitoring frequency is less/2 h, the thrust is 3500-6500t, the tunneling speed is 5-10mm, the rotating speed of a cutter head is 0.5-1.0r/min, the torque of the cutter head is 2000-6000Kn.m, the grouting pressure is 2-3bar, the specific gravity of the grouting is 1.05-1.08g/cm3the specific gravity of the discharged pulp is 1.08-1.25g/cm3。
In addition, a rotary jet grouting pile is arranged between the plain concrete continuous wall and the three-axis stirring pile, a horizontal hole is drilled in the portal, the portal grouting effect is tested, and grouting needs to be continued when the requirements cannot be met until the design requirements are met.
the construction of sealing the tunnel door is carried out in two steps, wherein in the first step, the embedding work of an embedded ring frame of a waterproof device is well done in the construction process of an initial end wall, and the embedded ring frame is required to be connected with structural steel bars of the end wall; and in the second step, the installation of the opening sealing pressing plate, the rubber curtain cloth plate and the like is completed before the chiseling of the second layer of concrete of the opening is completed.
The notch water pressure was set as follows:
and (4) theoretical calculation:
a, upper limit of water pressure of the notch:
on P = P1+ P2 + P3
=γw•h＋K0•[（γ-γw）•h+γ•（H-h）]＋20
p, on: an upper limit value (kPa) of cutting water pressure; p1: groundwater pressure (kPa); p2: static soil pressure (kPa); p3: the soil pressure is changed, and 20kPa is generally adopted; γ w: the water soluble weight (kN/m 3); h: the tunnel burial depth (calculated to the center of the tunnel) below the ground water level (m); k0: coefficient of static soil pressure; γ: volume weight of soil (kN/m 3); h: tunnel burial depth (calculated to the center of the tunnel) (m). b lower water pressure limit of the notch:
Under P = P1+ P'2+ P3
=γw•h+Ka•[（γ-γw）•h+γ•（H-h）]-2•Cu•sqr（Ka）+20
P is as follows: a cut water pressure lower limit (kPa); p' 2: active soil pressure (kPa); ka: active soil pressure coefficient; cu: cohesion (kPa) of soil.
The shield tunneling operation flow comprises the following steps: trial excavation 100m → equipment management standard → excavation and excavation are simultaneously carried out with synchronous grouting → reaching excavation cycle footage → segment assembly → excavation → next cycle.
The aim to be achieved by shield trial excavation of 100m is as follows:
1) the running-in load operation of the whole shield machine is completed by knowing various performances of the shield;
2) Various operations of a shield and matched equipment are skillfully performed, and the shield construction operation flow and the construction sequence are mastered;
3) Matching capability of the tested matched equipment, such as a muddy water treatment system, a vertical transportation system, a horizontal transportation system and the like;
4) And collecting data, accumulating experiences and providing reference basis and information for normal and rapid tunneling construction of the next step.
The shield tunneling parameters and indexes in the shield trial tunneling stage are shown in table 1:
the requirements of segment assembly and construction precision must reach the following precision:
1) tolerance of whole ring assembly: the ring surface clearance of adjacent rings is 5mm, and the clearance between adjacent blocks of longitudinal seams is 6 mm.
2) The diameter roundness of the lining ring and the assembly allowable deviation are +/-6 thousandths of Dmm. Wherein D refers to the outer diameter unit of the tunnel: mm.
3) the tunnel ring plane position is allowed to deviate by + -50 mm.
when the shield tunneling speed is set, the following points need to be noticed:
1) When the shield is started, a shield driver needs to check whether the jack is pushed up to be real or not, and the speed is not too high before the start of propulsion and the end of propulsion. When each ring of tunneling starts, the tunneling speed is gradually increased to prevent the stratum from being disturbed by the impact of the overlarge starting speed.
2) in the normal tunneling process of each ring, the tunneling speed value should be kept constant as much as possible, and fluctuation is reduced so as to ensure stable water pressure of the cut and smooth mud conveying and discharging pipes. When the tunneling speed is adjusted, the tunneling speed is gradually adjusted, so that impact disturbance to the stratum and overlarge water pressure swing of a notch caused by sudden speed change are avoided.
3) the propelling speed must meet the requirement of the tunneling grouting amount of each ring, and the synchronous grouting system is always in a good working state.
4) when the tunneling speed is selected, attention must be paid to matching with geological conditions, and abnormal damage to a shield cutter head and a cutter and overlarge disturbance of soil around a tunnel caused by improper speed selection are avoided.
In the tunneling construction process of the shield, the 1 st ring of tunneling is full-cabin tunneling, and the pressure of an air cushion cabin is maintained at 0.75 bar. The tunneling from the 2 nd ring to the 7 th ring is gradually pressurized by 0.1-0.3bar per ring according to the sealing condition of the tunnel door; and after the 7 th ring is tunneled, performing secondary sealing of a tunnel door, and starting pressurizing the 8 th ring by 1.46bar according to theoretical calculation.
The cautions in the construction process are as follows:
(1) The section of jurisdiction is rationally selected the type, installs between two parties to prevent that shield from being too big on one side with the section of jurisdiction clearance, on the other hand the undersize, cause the shield tail clearance inhomogeneous and reduce the shield tail sealed effect, damage the shield tail brush even, with shield tail clearance difference control during the construction within 20 mm.
(2) setting the water pressure of the cut according to a design value, carrying out corresponding adjustment according to the water level change condition at the propulsion moment, strictly controlling the fluctuation value of the muddy water pressure, and preventing soil body collapse caused by the fact that the soil body on the excavation surface cannot be supported due to low water pressure of the cut; the problem that the soil body collapses due to the fact that the water pressure of the notch is high and the soil body is disturbed excessively is avoided. The pressure fluctuation is controlled to be minus 0.2bar to plus 0.2bar, and the pressure fluctuation is prevented from puncturing the seabed shallow-buried covering soft soil layer.
(3) The method has the advantages that the quality control of the slurry at the sea bottom section and the monitoring of the sludge feeding and discharging are enhanced, the specific gravity of the slurry is properly increased, the viscosity of the slurry is controlled, the quality of a sludge film is ensured, the monitoring of the sludge feeding and discharging is enhanced, the relation between the tunneling speed and the sludge feeding and discharging is calculated in advance, the sludge discharging abnormity is found, the parameters are adjusted in time, and the collapse caused by over-excavation is prevented;
(4) the soil output is strictly controlled, when the dry sand amount is too large, the use frequency of the stratum detection device is improved, so that the collapse condition of the soil body on the front side of the cut can be mastered in time, parameters can be adjusted in time according to specific construction conditions, the data of the dry sand amount is close to a theoretical value, and the possibility of collapse of the soil body on the front side is reduced;
(5) when the seabed slurry leakage is discovered, if the slurry leakage is slight, the shield can be pushed forward under the condition of not reducing the water pressure of the excavation surface, and meanwhile, the pushing speed is properly accelerated, the assembling efficiency is improved, and the shield can pass through the slurry leakage area as early as possible;
(6) When the slurry is seriously overflowed and can not be pushed: reducing the water pressure of the excavation surface until the (soil pressure + water pressure) is balanced; the specific gravity and the viscosity of the muddy water are improved by adopting heavy slurry for propulsion; in order to enable the shield to be pushed forward, the amount of dry excavating and cutting sand is checked, and whether overexcavation exists or not is confirmed; performing sufficient grouting after tunneling for a certain distance; and returning the water pressure of the excavation face to a normal state, and performing normal excavation.
(7) The synchronous grouting quality is improved, the grout is required to have shorter initial setting time, so that the grout does not crack after meeting muddy water, and the grout is required to have certain fluidity, can uniformly fill a tunnel for one circle and fill a building gap in time; on the basis of synchronous grouting, muddy water glass double-liquid slurry is injected, hoops are formed around the tunnel, and the hoops are sealed at intervals of 10 intervals, so that a discontinuous water-stopping isolation zone is longitudinally formed in the tunnel, the floating of the tunnel is slowed down and restricted, and the deformation of the tunnel is controlled.
(8) When the tunnel is found to have large floating amount and a relatively long coverage range, secondary grouting measures should be immediately adopted for the built tunnel to cut off a muddy water continuous loss path.
Finally, the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting, and other modifications or equivalent substitutions made by the technical solutions of the present invention by those of ordinary skill in the art should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.
Claims (10)
1. A shallow soil covering shield construction method is characterized by comprising the following steps:
1) Constructing an initial well: the shield starting well is constructed by adopting an open-cut reverse construction method, a foundation pit enclosure structure of the starting well adopts a ground connecting wall with the thickness of 1200mm, six inclined concrete supports are vertically arranged, a temporary central pillar is arranged in the middle, and a bored pile with the diameter of phi 1200mm is arranged below the temporary central pillar;
2) starting section reinforcement and precipitation: the initial section reinforcement comprises initial section end reinforcement and stratum reinforcement; constructing a precipitation well after the initial section is reinforced, so that the shield can be precipitated below the bottom of the tunnel in advance before the initial section and the initial section are reached;
3) Construction of an originating station: the method comprises the following steps that concrete is poured into an originating station, the shield originating station is positioned according to a control point of measurement lofting, and a base of the originating station is of an arc-shaped structure; reserving grooves in two longitudinal channels of the starting base, reserving a groove in one transverse channel, and reserving an operation space for shield assembly welding;
4) Assembling and debugging the shield;
5) installing a reaction frame and a supporting structure;
6) Installing a tunnel door sealing device: the sealing device comprises a first seal fixed on a ring frame pre-embedded at the hole and a second seal fixedly connected with the first seal through a sealing ring pipe, and a stiffened plate with one end connected with the hole is fixed on the sealing ring pipe; the first seal and the second seal are arranged in parallel and are spaced by 500 mm; a grease filling hole is formed in the middle of the sealing ring pipe;
7) Chiseling a tunnel portal;
8) Installing a negative ring duct piece, and pushing a shield until the cutter head contacts the tunnel face;
9) The muddy water bin establishes a balance pressure: setting the water pressure of the notch according to a design value, carrying out corresponding adjustment according to the water level change condition at the propulsion moment, and strictly controlling the fluctuation value of the muddy water pressure to control the fluctuation value of the muddy water pressure within-0.2 bar to +0.2 bar;
10) and (5) circularly tunneling the shield.
2. the shallow soil shield construction method of claim 1, wherein the temporary central pillar in step 1) is a 460mm x 460mm lattice pillar.
3. the shallow soil shield construction method of claim 1, wherein the reinforcing of the end of the initiation section in the step 2) comprises the following steps:
Firstly, adopting C25 plain concrete to construct a peripheral structure of an initial reinforcing area on one side of a foundation pit support structure of an initial well, which is positioned at a tunnel portal, so as to form a 3-surface plain concrete continuous wall, and enclosing the 3-surface plain concrete continuous wall and the initial well support structure to form a shield initial reinforcing area;
Constructing a first tunnel portal reinforcing area at a tunnel portal in the shield initial reinforcing area, wherein the first tunnel portal reinforcing area is a plain concrete continuous wall with the thickness of 1 m;
Thirdly, constructing a second hole reinforcing area on the outer surface of the first hole reinforcing area by adopting a three-row phi 1200@800mm high-pressure rotary spraying reinforcing mode, and constructing a third hole reinforcing area on the outer sides of the starting well enclosure structure and the peripheral structure of the starting reinforcing area; the third hole door reinforcing area is triangular, one side surface of the third hole door reinforcing area is fixedly connected with the originating well enclosure structure, and the bottom of the third hole door reinforcing area is fixedly connected with the peripheral structure of the originating reinforcing area;
fourthly, reinforcing the bottom in the shield starting reinforcing area by adopting a triaxial mixing pile.
4. The shallow soil covering shield construction method according to claim 3, wherein the operation process of the triaxial mixing pile in the fourth step is as follows: firstly, making a test pile, and after the test is successful, making large-area construction; and after the reinforcement and construction of the triaxial mixing pile are finished, core-pulling inspection is carried out on the occlusion part of the triaxial mixing pile according to the proportion of 3%, and unqualified pile repair is continued until the pile is qualified.
5. The shallow soil shield construction method of claim 4, wherein the test parameters of the test pile are as follows: the cement injection amount is 538.2kg/m, the grouting pressure is 4-7bar, the drill rod lifting speed is 0.5-1.0m/min, and the stirring sinking speed is 0.1-0.5 m/min; the diameter of each three-axis stirring pile is 850mm, and the three-axis stirring piles are adjacent to each other to form an inter-pile occlusion area, so that the distance between the centers of circles of the three-axis stirring piles is 600 mm.
6. the shallow soil shield construction method according to claim 4, characterized in that a jet grouting pile is arranged between the plain concrete continuous wall and the triaxial mixing pile, a horizontal hole is drilled on the portal, the portal grouting effect is checked, and grouting needs to be continued when the requirements cannot be met until the design requirements are met.
7. The shallow soil-covering shield construction method according to claim 1, wherein the dewatering well in the step 2) is implemented by adopting an impact hole-forming construction process, a filter pipe is arranged below the dewatering well, and a solid pipe is connected to the filter pipe; the bottom of the solid pipe is positioned 5m below the ground surface, and clay is filled between the solid pipe and the dewatering well; filling gravel between the filter pipe and the dewatering well; the diameter of precipitation well is 600mm, precipitation well's bottom plate is located 2000mm below the tunnel bottom line.
8. the shield construction method with shallow soil covering according to claim 1, wherein the step 4) comprises the steps of preparing an assembly site → preparing a starting place → assembling a crane in place → connecting a rear matched trailer with a pipeline → connecting a main machine with a lifting frame → installing a reaction frame → positioning the main machine and connecting the rear matched with the main machine → no-load debugging → installing a negative ring pipe piece → load debugging.
9. The shallow soil shield construction method according to claim 1, wherein in step 6), the first seal comprises a first rubber curtain cloth hung on a ring frame and fixed by a first ring plate, and a first turning plate is rotatably connected to the bottom of the first ring plate; the second seal comprises a pressing plate fixedly connected with the stiffened plate and the outer side of the sealing ring pipe, and a second rubber curtain cloth hung on the pressing plate through bolts, the second rubber curtain cloth is fixed through a second ring plate, and a second turning plate is rotatably connected to the bottom of the second ring plate.
10. The shallow soil shield construction method of claim 1, wherein in step 10) the shallow soil shield construction method is carried outthe pressure value at the top of the cabin is 0-1.46bar, the ground monitoring frequency is less/2 h, the thrust is 3500-6500t, the tunneling speed is 5-10mm, the rotating speed of a cutter head is 0.5-1.0r/min, the torque of the cutter head is 2000-6000kn.m, the grouting pressure is 2-3bar, the specific gravity of the grouting is 1.05-1.08g/cm3The specific gravity of the discharged pulp is 1.08-1.25g/cm3。
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| CN113006808A (en) * | 2021-04-23 | 2021-06-22 | 中铁六局集团有限公司交通工程分公司 | Construction method for viscous geological shield initial section to penetrate shallow soil-covered river channel downwards |
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