CN110735642A - shield originating end combined type reinforcing structure and construction method thereof - Google Patents

shield originating end combined type reinforcing structure and construction method thereof Download PDF

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Publication number
CN110735642A
CN110735642A CN201910916702.7A CN201910916702A CN110735642A CN 110735642 A CN110735642 A CN 110735642A CN 201910916702 A CN201910916702 A CN 201910916702A CN 110735642 A CN110735642 A CN 110735642A
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CN
China
Prior art keywords
grouting
pile
horizontal
shield
drilling
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CN201910916702.7A
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Chinese (zh)
Inventor
陈俐光
赵圣武
于艺林
陈�峰
于勇
赵勇
姜涌
田辉
王斓
戚鹏飞
袁俊
刘乐
Original Assignee
中建市政工程有限公司
中国建筑一局(集团)有限公司
中铁第六勘察设计院集团有限公司
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Application filed by 中建市政工程有限公司, 中国建筑一局(集团)有限公司, 中铁第六勘察设计院集团有限公司 filed Critical 中建市政工程有限公司
Priority to CN201910916702.7A priority Critical patent/CN110735642A/en
Publication of CN110735642A publication Critical patent/CN110735642A/en

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Classifications

    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D9/00Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
    • E21D9/001Improving soil or rock, e.g. by freezing; Injections
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D9/00Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
    • E21D9/06Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining
    • E21D9/0642Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining the shield having means for additional processing at the front end
    • E21D9/0671Making by using a driving shield, i.e. advanced by pushing means bearing against the already placed lining the shield having means for additional processing at the front end with means for consolidating the rock in front of the shield by injection of consolidating substances through boreholes

Abstract

The invention relates to a shield starting end head combined reinforcing structure and a construction method thereof, wherein the combined reinforcing structure comprises a high-pressure jet grouting pile vertical reinforcing area and a drilling and grouting horizontal reinforcing area, the high-pressure jet grouting pile vertical reinforcing area is used for vertically reinforcing the shield starting end head, the range of the vertical reinforcing area is 15-20 m outside a shield starting well underground continuous wall and 3-5 m outside the outer edge of a shield tunnel structure in the horizontal direction, the vertical direction is 3-5 m above the top of the tunnel to 3-5 m below the bottom of the tunnel, the horizontal reinforcing area is horizontally outward or horizontally downward from the shield starting end head opening of the shield continuous wall along a shield excavation contour line, and the method is characterized in that an L-shaped semi-surrounding structure is formed by using the combined reinforcing structure to isolate the corrosion of underground water.

Description

shield originating end combined type reinforcing structure and construction method thereof

Technical Field

The invention belongs to shield initiating end head combined reinforced structures and a construction method thereof.

Background

When the shield is initiated in a composite stratum, in order to keep the stratum after the underground diaphragm wall is broken stable and prevent the shield machine from completely entering the stratum and causing the phenomena of sinking of the stratum around the tunnel , sinking of structures and the like due to the fact that a large amount of sand and water are poured into the space between the shield body and the structure of the tunnel , effective measures are needed to be taken for carrying out end reinforcement treatment so as to keep the stratum stable when the shield machine is initiated and prevent the tunnel face from collapsing.

The traditional process usually adopts a single mode, such as a high-pressure jet grouting pile or sleeve valve pipe grouting mode to reinforce the end soil body, the mode only can isolate the influence of horizontal water pressure and is difficult to effectively isolate underground water below the shield excavation contour, so that the underground water is frequently generated to enter the shield excavation contour line from the lower part, the stratum water permeability is caused, the water burst accident is caused, and the shield construction safety is seriously threatened.

Disclosure of Invention

The invention aims to design combined reinforcing structures for the shield starting end and a construction method thereof, which are used for making up the defects of a single reinforcing structure for the shield starting end and improving the reinforcing effect of the shield starting end.

Therefore, the combined reinforcing structures for the shield initiation end head comprise an underground continuous wall and concrete support columns for supporting four corners at the inner end of the underground continuous wall, and the combined reinforcing structures for the shield initiation end head comprise a high-pressure jet grouting pile vertical reinforcing area and a drilling and grouting horizontal reinforcing area, wherein:

the high-pressure jet grouting pile vertical reinforcing area: the vertical reinforcement method is used for vertically reinforcing a shield starting end, the range of a vertical reinforcement area is 15-20 m outside a shield starting well underground continuous wall and 3-5 m outside the outer edge of a shield tunnel structure in the horizontal direction, the vertical direction is 3-5 m above the top of a tunnel to 3-5 m below the bottom of the tunnel, two rows of closed edge walls formed by high-pressure rotary spraying piles in advance are arranged at the edge of the vertical reinforcement area, the reinforcement depth of the closed edge walls is up to the bottom of the vertical reinforcement area, a closed space is formed in the vertical reinforcement area by the closed edge walls, the radius of each pile of the two rows of high-pressure rotary spraying piles forming the closed edge walls is 400mm, the distance between the centers of the adjacent high-pressure rotary spraying piles is 650mm, and the pile edges of the adjacent high-pressure rotary spraying piles are mutually occluded by 150 mm.

A plurality of high-pressure jet grouting piles are arranged in the closed space at intervals, the radius of each pile in the closed space is 400mm, the distance between the centers of the adjacent high-pressure jet grouting piles is 650mm, and the edges of the adjacent high-pressure jet grouting piles are meshed with each other by 150 mm.

The extension length of the pile bottom end of each high-pressure jet grouting pile close to the underground continuous wall of the shield starting well in the closed space is greater than that of the pile bottom end of each high-pressure jet grouting pile far away from the underground continuous wall of the shield starting well.

Drilling and grouting horizontal reinforcement area: the shield tunneling reinforcing method is used for horizontally reinforcing a shield starting end, a horizontal reinforcing area horizontally inclines outwards or horizontally inclines downwards from an opening of the shield starting end of the underground continuous wall shield along a shield tunneling contour line, the range of the horizontal reinforcing area is 15-20 m from the horizontal direction of the shield starting well underground continuous wall, the range of the lower end of a shield tunnel structure and the range of 3-5 m from the outer edges of two sides, the upper boundary of the horizontal reinforcing area is lower than the upper end of the shield tunneling contour line, the lower boundary of the horizontal reinforcing area is lower than the bottom end of the shield tunneling contour line to form an oblique contour line, the horizontal reinforcing area and a vertical reinforcing area are overlapped below the shield tunneling range to form an L-shaped combined reinforcing curtain structure, and the horizontal reinforcing area is formed by a plurality of horizontal grouting drill holes which are arranged at intervals in the horizontal reinforcing area and mixed cement mortar is pressed into the horizontal.

The bottom of each high-pressure jet grouting pile extends to the lower end of the shield tunnel structure by 3-5 m.

The high-pressure jet grouting pile comprises the following components: the pressure of the reinforced slurry is 2-5 MPa, the air pressure is 0.6-0.8 MPa, the water pressure is greater than 30MPa, the rotating speed is 8-12 rpm, the flow rate of the cement slurry is greater than or equal to 70L/min, and the air flow rate is 60-80 m3And h, the lifting speed is 6-12 cm/min, the slurry material adopts cement slurry, the water cement ratio is 1.0-1.5, the specific gravity of the cement slurry poured into the slurry material is 1.5-1.6, and the specific gravity of the returned slurry is 1.2-1.3.

The pile bottom extension length of each high-pressure jet grouting pile in the closed space gradually decreases from 5m below the bottom of the tunnel to 3m from the underground continuous wall of the shield starting well to the outside.

Horizontal reinforcement district in numerous horizontal slip casting drilling that are the interval and set up from last to being equipped with several rows down, adjacent row spacing 900 ~ 1100mm, with arranging adjacent two hole interval 700 ~ 800mm, lie in each horizontal slip casting drilling of each row of top to keeping the level, lie in each horizontal slip casting drilling of each row of middle part to the slope of 5 ~ 6% of inclining to the lower extreme, lie in each horizontal slip casting drilling of each row of bottom to the slope of 8 ~ 9% of inclining to the lower extreme.

The construction method of the shield originating end head combined reinforcing structure is characterized by comprising the following steps:

(1) construction preparation: preparing a drilling pile machine, cement for grouting, a reservoir, water glass slurry, a stirrer, a grouting pump, a mixer, an air compressor, a high-pressure pump and a grout stopping plug at a construction site; the construction of the horizontal consolidation zone by drilling and grouting is carried out in the originating well, and a support is required to be built in the originating well.

(2) The method comprises the steps of positioning a pile machine in a vertical reinforcing area of the high-pressure jet grouting pile, namely before construction, determining a control point of jet grouting pile construction by using a total station in the ground range of 15-20 m outside a shield initial well underground continuous wall and 3-5 m outside the outer edge of a shield tunnel structure in the horizontal direction in the vertical reinforcing area, after a retest check line is qualified, actually laying a pile position by using a steel ruler and a measuring line, nailing the pile position by using a bamboo stick, tagging a pile , ensuring that the displacement deviation of the center of a pile hole is less than 30mm, centering and leveling the pile machine according to a lofting point position, adjusting the verticality of the pile machine, ensuring that a drill rod is required to be equal to and the deviation is within 10mm, ensuring that the verticality of a drilled hole is less than 1%, debugging an air compressor and a slurry pump before drilling to enable equipment to operate normally, checking the length of the drill rod, marking a depth.

(3) Drilling and jet grouting lifting of a vertical reinforcing area of the high-pressure jet grouting pile: before drilling, an air compressor and a slurry pump are required to be debugged to ensure that the equipment runs normally; checking the length of the drill rod, marking a depth line beside the drilling tower by using red paint, and ensuring that the elevation of the bottom of the hole meets the design depth; the construction of the drilling machine needs to firstly carry out trial spraying on the ground, after the trial running of the drilling machine is normal, the drilling machine starts to guide holes to drill, the number of drill rod sections needs to be recorded in detail in the drilling process, and the accuracy of the drilling depth is guaranteed.

Constructing in advance, wherein two rows of closed edge walls formed by high-pressure rotary jet grouting piles are constructed, the reinforcing depth of the closed edge walls reaches the bottom of a vertical reinforcing area, closed spaces are formed in the vertical reinforcing area by the closed edge walls, the radius of each pile of the two rows of high-pressure rotary jet grouting piles forming the closed edge walls is 400mm, the distance between the centers of adjacent high-pressure rotary jet grouting piles is 650mm, and the adjacent high-pressure rotary jet grouting piles areThe pile edges are mutually meshed for 150 mm; the closed edge wall is formed by adopting phi 400 triple-tube high-pressure rotary jet grouting piles, the reinforcing slurry pressure is 2-5 MPa, the air pressure is 0.6-0.8 MPa, the water pressure is greater than 30MPa, the rotating speed is 8-12 rpm, the cement slurry flow is greater than or equal to 70L/min, and the air flow is 60-80 m3And h, the lifting speed is 6-12 cm/min, the slurry material adopts cement slurry, the water cement ratio is 1.0-1.5, the specific gravity of the cement slurry poured into the slurry material is 1.5-1.6, and the specific gravity of the returned slurry is 1.2-1.3.

And after the high-pressure jet grouting piles of the closed edge wall reach fixed strength, constructing the high-pressure jet grouting piles in the closed edge wall, wherein the radius of each pile in the closed space is 400mm, the pile center distance between adjacent high-pressure jet grouting piles is 650mm, and the pile edges of the adjacent high-pressure jet grouting piles are mutually occluded by 150 mm.

The extension length of the pile bottom end of each high-pressure jet grouting pile close to the underground continuous wall of the shield starting well in the closed space is greater than that of the pile bottom end of each high-pressure jet grouting pile far away from the underground continuous wall of the shield starting well.

The rotary spraying lifting requirement of the high-pressure rotary spraying pile is as follows: after the hole is led to the designed depth, the rock core pipe is pulled out, the injection grouting pipe is replaced to be inserted into the preset depth, during the pipe inserting process, water injection and pipe inserting are carried out, the water pressure is not more than 1Mpa, after the injection grouting pipe is inserted into the designed depth, a slurry pump is connected, then rotary spraying is carried out from bottom to top, and simultaneously slurry is cleaned and discharged; when spraying, the rotary spray pipe is gradually lifted after the preset spraying pressure and the preset gunite are reached; in order to ensure the quality of the bottom end of the pile, when the nozzle is sunk to the designed depth, the nozzle is rotated for 10-15 seconds at the original position, and the nozzle is lifted by rotary spraying after the orifice is normally overflowed; the rotation and the lifting of the drill rod are continuously carried out without interruption, the drilling machine breaks down, the lifting of the drill rod and the rotation are stopped to prevent pile breakage and immediately overhaul and remove the fault, the guniting and rotary spraying time of the drill rod within 1.0m of the bottom of the pile is 30-60 seconds in order to improve the quality of the bottom end of the pile, and rotary spraying parameters can be adjusted according to different soil layers in the rotary spraying lifting process; and finishing the construction of each high-pressure jet grouting pile in the vertical reinforcing area of the high-pressure jet grouting pile.

And after the construction of the high-pressure jet grouting pile is completed, drilling and grouting are carried out to horizontally reinforce the area.

(4) Positioning grouting holes in a drilling grouting horizontal reinforcement area: and (3) extending the shield starting well underground continuous wall to 15-20 m from the inlet of the shield starting well underground continuous wall as a starting point, and extending the lower end of the shield tunnel structure and the outer edges of two sides to 3-5 m.

A plurality of horizontal grouting drill holes arranged at intervals in a horizontal reinforcing area are provided with a plurality of rows from top to bottom, the distance between every two adjacent rows is 900-1100 mm, the distance between every two adjacent holes in the same row is 700-800 mm, each horizontal grouting drill hole in each row at the top is kept horizontal, each horizontal grouting drill hole in each row at the middle is inclined towards the lower end by 5-6% of gradient, each horizontal grouting drill hole in each row at the bottom is inclined towards the lower end by 8-9% of gradient, grouting holes are radial inclined holes, so lofting positioning is carried out according to three-dimensional coordinates of the hole during lofting, a hole center is lofted on an underground continuous wall in a hole by using a total station, a pile position center is marked by using a shooting nail, lofting is allowed to be +/-5 mm, a grouting hole center extension line is lofted on the other side wall surface of a structural wall, a drilling machine is positioned by using a connecting line of the drilling machine, when a hole is formed, the total station is used for rechecking the direction and elevation of a drill rod, and drilling can be.

(5) Drilling a horizontal reinforcing area by drilling and grouting, and installing an orifice pipe: and (3) arranging an orifice pipe in each drill hole, wherein the diameter of the hole of the grouting hole is 110mm, the diameter of the orifice pipe is 108mm, the wall thickness of the orifice pipe is 5mm, the pipe length is 3m, after the positioning of a drilling machine is tested again, the hole is drilled to 2.8m, after a drill rod is withdrawn, the orifice pipe is jacked into the hole by the drilling machine and anchored by an anchoring agent, and a quick joint is welded on the outer side of the orifice pipe.

(6) And (3) installing a water drainage and grout stop device in the horizontal reinforcing area for drilling and grouting, namely after the orifice pipe is fixedly installed, drilling to the designed depth through the orifice pipe, stopping drilling, dismounting sections of drill rods from the drilling machine, then sleeving a water drainage device, a grout stop plug and a hollow pressure plate on the drill rods, connecting the water drainage device and the orifice through a quick joint, then arranging the grout stop plug in the water drainage device, and connecting and pressing the bolt pressure plate and the water drainage device to enable the grout stop plug to block a gap between the drill rods and the water drainage device.

(7) And (3) retreating grouting construction of the drilling grouting horizontal reinforcement area: the grouting material is cement-water glass slurry, and the volume ratio of the mixture ratio is = 1: 1.0,the water cement ratio of the cement paste is 0.8: 1-1: 1, the water glass is water glass with the modulus of 2.6-2.8 and the baume degree of 35 degrees, which meets the national requirements, and the density of 1.40-1.46 g/cm3And the cement is ordinary Portland cement with the strength grade of 42.5 and the initial setting time of more than 3 hours and the final setting time of longer, the upper boundary of the ordinary Portland cement does not exceed the shield excavation contour line, the ordinary Portland cement is placed at the bottom end of a grouting area of the high-pressure jet grouting pile to form an oblique contour line, and the horizontal reinforcing area and the vertical reinforcing area are superposed below the shield excavation range to form an L-shaped combined type reinforcing curtain structure.

When grouting is started, after grout flows to the bottom of a hole through a drill rod, the hole between the walls of the drill hole is filled, the grout is diffused into the stratum, the drill rod is kept to rotate in the grouting process to avoid grout cementation, after the grouting pressure reaches a designed value, a grout stop plug is loosened, the drill rod is retreated to the position below the drill rod, the extra drill rod outside the hole is removed, then the grout stop plug is screwed down, grouting is continued, and the grouting is repeated and retreated until the grouting of the hole position is completed.

And repeating the steps to finish grouting of each hole position of the drilling grouting horizontal reinforcing area.

(8) And (4) reinforcing effect inspection: the standard value of the unconfined compressive strength of the high-pressure jet grouting pile in 28 days is not less than 1Mpa, and a drilling and coring method is adopted.

And (3) drilling and coring, namely drilling a rock core in a constructed consolidation and reinforcement area, making the rock core into a standard test piece, performing an indoor physical and mechanical property test, checking the uniformity and impermeability of an internal pile body, and qualitatively evaluating the grouting effect, drilling a hole in a grouting area through a geological drilling machine, taking the rock core out of the stratum as completely as possible, wherein the coring strength is not less than 1.0MPa, the core strength detection in the reinforcement area is qualified after 28d, no obvious water leakage condition exists when holes are drilled, and the maximum ground settlement/uplift is less than 30mm after the shield is started.

The grouting hole sites are all radial inclined hole sites, and the grouting hole sites are radially inclined from the horizontal direction of the inlet of the underground continuous wall of the shield starting well to both sides in an explosive manner, or from the horizontal direction of the inlet of the underground continuous wall of the shield starting well to both sides and the lower end in an explosive manner.

The above structural design and method achieve the objectives of the present invention.

The method is used for making up the defect of reinforcing the structure of the shield starting end sheet , and improving the reinforcing effect of the shield starting end, and has the advantages of simple structure, good reinforcing quality, high construction efficiency, cost saving, time saving, labor saving and good use effect.

Compared with the prior art, the invention has the following beneficial effects:

(1) the high-pressure jet grouting pile is adopted to reinforce the end head area, the reinforcing depth includes the shield tunneling range, and an th waterproof curtain is formed.

(2) The invention adopts the horizontal drilling grouting technology to perform backward double-liquid grouting, quickly solidifies, reinforces the area below the shield tunneling range, forms a second waterproof curtain below the shield tunneling range and isolates the underground water erosion.

(3) The two waterproof curtain structures can be combined to form an L-shaped semi-surrounding structure, so that the water pressure of the strong permeable layer is isolated, and a good reinforcing effect is achieved.

(4) The invention has the advantages of unique concept, simple structure, compactness, reasonableness, reliable working performance, flexible and labor-saving operation, suitable construction and use, convenience for pushing and the like.

Drawings

FIG. 1 is a schematic longitudinal cross-sectional view of the vertical and horizontal reinforcement structure of the present invention.

Fig. 2 is a schematic top view of the vertical reinforcing region structure of the present invention.

Fig. 3 is a schematic view of the engagement structure of piles of the vertical reinforcement section of the present invention.

Fig. 4 is a schematic view of the pile drilling distribution of the horizontal reinforcement zone of the present invention.

Fig. 5 is a schematic diagram of the intersection structure of pile holes in the vertical and horizontal reinforcement areas of the present invention.

Detailed Description

As shown in fig. 1 to 5, kinds of combined reinforcing structures for shield initiation end, which are composed of an underground continuous wall 1 and concrete support columns 6 for supporting four corners of the inner end of the underground continuous wall, include a high-pressure jet grouting vertical reinforcing region 2 and a drilling grouting horizontal reinforcing region 5, wherein:

and (3) vertically reinforcing the high-pressure jet grouting pile in the area 2: the method is used for vertically reinforcing the shield starting end. The range of the vertical reinforcing area is 15-20 m outside the underground continuous wall of the shield initial well in the horizontal direction and 3-5 m outside the outer edge of the shield tunnel structure, and the range of the vertical reinforcing area is 3-5 m above the top of the tunnel to 3-5 m below the bottom of the tunnel.

Two rows of closed edge walls 21 formed by constructing high-pressure jet grouting piles 22 in advance are arranged at the edge of the vertical reinforcing area, the reinforcing depth of the closed edge walls reaches the bottom of the vertical reinforcing area, and closed spaces are formed in the vertical reinforcing area by the closed edge walls. The radius of each pile of two rows of high-pressure jet grouting piles forming the closed area edge wall is 400mm, the pile center distance of adjacent high-pressure jet grouting piles is 650mm, and the pile edges of the adjacent high-pressure jet grouting piles are meshed with each other by 150 mm. After the construction of two rows of high-pressure jet grouting piles forming the closed edge wall is finished, a plurality of high-pressure jet grouting piles in the closed space are constructed to ensure that cement paste in a reinforcing range does not leak.

A plurality of high-pressure jet grouting piles 22 are arranged in the closed space at intervals, the radius of each pile in the closed space is 400mm, the distance between the centers of adjacent high-pressure jet grouting piles is 650mm, and the edges of the adjacent high-pressure jet grouting piles are mutually meshed by 150 mm. The bottom of each high-pressure jet grouting pile extends to the lower end of the shield tunnel structure by 3-5 m.

The extension length of the pile bottom end of each high-pressure jet grouting pile close to the underground continuous wall of the shield starting well in the closed space is greater than that of the pile bottom end of each high-pressure jet grouting pile far away from the underground continuous wall of the shield starting well. The pile bottom extension length of each high-pressure jet grouting pile in the closed space gradually decreases from 5m below the bottom of the tunnel to 3m from the underground continuous wall of the shield starting well to the outside.

The high-pressure jet grouting pile 22 comprises the following components: the pressure of the reinforced slurry is 2-5 MPa, the air pressure is 0.6-0.8 MPa, the water pressure is greater than 30MPa, the rotating speed is 8-12 rpm, the flow rate of the cement slurry is greater than or equal to 70L/min, and the air flow rate is 60-80 m3The lifting speed is 6-12 cm/min, the slurry material adopts cement slurry, the water cement ratio is 1.0-1.5, the specific gravity of the cement slurry poured into the slurry is 1.5-1.6, and the specific gravity of the returned slurry is1.2~1.3。

Drilling grouting horizontal reinforcement area 5: the method is used for horizontally reinforcing the shield starting end. The horizontal reinforcing area is horizontally towards the outside or horizontally towards and downwards inclined from the initial end opening of the underground continuous wall shield along the shield excavation contour line. The range of the horizontal reinforcing area is 15-20 m from the underground continuous wall of the shield starting well in the horizontal direction and 3-5 m from the lower end and the outer edges at two sides of the shield tunnel structure. The starting point of the upper boundary of the horizontal reinforcing area can be lower than the upper end of the shield excavation contour line, and the lower boundary is lower than the bottom end of the shield excavation contour line 3 to form an oblique contour line 4.

The horizontal reinforcing area and the vertical reinforcing area are overlapped at the position below the shield tunneling range to form an L-shaped combined type reinforcing curtain structure, and the horizontal reinforcing area is formed by a plurality of horizontal grouting drill holes arranged at intervals in the horizontal reinforcing area and mixed cement mortar is pressed into the horizontal reinforcing area through the horizontal grouting drill holes. The mixed cement mortar is cement-water glass slurry.

Horizontal reinforcement district in numerous horizontal slip casting drilling that are the interval and set up from last to being equipped with several rows down, adjacent row spacing 900 ~ 1100mm, with arranging adjacent two hole interval 700 ~ 800mm, lie in each horizontal slip casting drilling of each row of top to keeping the level, lie in each horizontal slip casting drilling of each row of middle part to the slope of 5 ~ 6% of inclining to the lower extreme, lie in each horizontal slip casting drilling of each row of bottom to the slope of 8 ~ 9% of inclining to the lower extreme.

As shown in figure 4, three rows can be drilled by adopting horizontal grouting, the row spacing is 1000mm, the th row is kept horizontal, the second row is inclined downwards by 5 percent of gradient (approximately close to the initial gradient of the shield), the third row is inclined downwards by 8 percent of gradient (slightly larger than the initial gradient of the shield), the grouting adopts retreating grouting, a grouting opening is provided with a high-pressure valve and a grout stop plug to prevent the backflow of grout, the distance between two holes is 750mm, the horizontal reinforcement and the vertical high-pressure jet grouting pile reinforcement are overlapped at the part below the tunneling range of the shield to form an L-shaped combined reinforced curtain structure, the influence of water pressure on the front part and the lower part of the shield tunneling can be effectively isolated after the strength is formed, and the safety guarantee is provided for the shield initial.

The construction method of the shield originating end head combined reinforcing structure comprises the following steps:

(1) construction preparation: preparing a drilling pile machine, cement for grouting, a reservoir, water glass slurry, a stirrer, a grouting pump, a mixer, an air compressor, a high-pressure pump and a grout stopping plug at a construction site; the construction of the horizontal consolidation zone by drilling and grouting is carried out in the originating well, and a support is required to be built in the originating well. The raw materials, equipment, supports and the like are all equipment technologies in the field, so the description is omitted.

(2) Before construction, the ground range of the vertical reinforced area is the ground range of 15-20 m outside the underground continuous wall of the shield initial well in the horizontal direction and 3-5 m outside the outer edge of the shield tunnel structure, a control point of the construction of the jet grouting pile is measured by using a total station, after a repeated test line is qualified, a pile position is arranged on the spot by using a steel ruler and a measuring line, the pile position is nailed by using a bamboo stick, is signed by a pile , the center displacement deviation of the pile hole is ensured to be less than 30mm, the pile machine is centered and leveled according to the lofting point position, the verticality of the pile machine is adjusted, the drill rod is ensured to be caused to be , the deviation is within 10mm, the verticality of the drill hole is less than 1%, an air compressor and a slurry pump are debugged before drilling, the equipment is operated normally, the length of the drill rod is verified, a depth line is marked beside a drill tower.

(3) Drilling and jet grouting lifting of a vertical reinforcing area of the high-pressure jet grouting pile: before drilling, an air compressor and a slurry pump are required to be debugged, so that the equipment can normally operate. And checking the length of the drill rod, and marking a depth line beside the drilling tower by using red paint to ensure that the elevation of the bottom of the hole meets the design depth. The construction of the drilling machine should firstly carry out trial spraying on the ground. After the trial run of the drilling machine is normal, the pilot drilling is started. The number of drill rod sections needs to be recorded in detail in the drilling process, and the accuracy of the drilling depth is guaranteed.

Firstly, constructing two rows of closed edge walls formed by high-pressure jet grouting piles. The closed edge wall is reinforced to the bottom of the vertical reinforcing area, a closed space is formed in the vertical reinforcing area by the closed edge wall, the radius of each pile of two rows of high-pressure jet grouting piles forming the closed edge wall is 400mm, the distance between the centers of adjacent high-pressure jet grouting piles is 650mm, and the pile of the adjacent high-pressure jet grouting pileThe edges are mutually meshed for 150 mm; the closed edge wall is formed by adopting phi 400 triple-tube high-pressure rotary jet grouting piles, the reinforcing slurry pressure is 2-5 MPa, the air pressure is 0.6-0.8 MPa, the water pressure is greater than 30MPa, the rotating speed is 8-12 rpm, the cement slurry flow is greater than or equal to 70L/min, and the air flow is 60-80 m3And h, the lifting speed is 6-12 cm/min, the slurry material adopts cement slurry, the water cement ratio is 1.0-1.5, the specific gravity of the cement slurry poured into the slurry material is 1.5-1.6, and the specific gravity of the returned slurry is 1.2-1.3.

And after the high-pressure jet grouting piles of the closed edge wall reach fixed strength, constructing the high-pressure jet grouting piles in the closed edge wall, wherein the radius of each pile in the closed space is 400mm, the pile center distance between adjacent high-pressure jet grouting piles is 650mm, and the pile edges of the adjacent high-pressure jet grouting piles are mutually occluded by 150 mm.

The extension length of the pile bottom end of each high-pressure jet grouting pile close to the underground continuous wall of the shield starting well in the closed space is greater than that of the pile bottom end of each high-pressure jet grouting pile far away from the underground continuous wall of the shield starting well.

The technology of the high-pressure jet grouting pile is the existing technology. The rotary spraying lifting requirements of the high-pressure rotary spraying pile of the invention are as follows: after the hole is led to the designed depth, the rock core pipe is pulled out, the injection grouting pipe is replaced to be inserted into the preset depth, during the pipe inserting process, water injection and pipe inserting are carried out, the water pressure is not more than 1Mpa, after the injection grouting pipe is inserted into the designed depth, a slurry pump is connected, then the slurry pump is connected, and the slurry is sprayed from bottom to top in a rotating mode, and meanwhile the slurry is cleaned and discharged. When spraying, the rotary spray pipe is gradually lifted after the preset spraying pressure and the preset gunite are reached. In order to ensure the quality of the bottom end of the pile, when the nozzle sinks to the designed depth, the nozzle rotates 10-15 seconds at the original position, and the nozzle is lifted by rotary spraying after the orifice is normally overflowed. The rotation and the lifting of the drill rod are continuously carried out without interruption, the drilling machine breaks down, the lifting of the drill rod and the rotation are stopped to prevent pile breakage and immediately overhaul and remove the fault, the guniting and rotary spraying time of the drill rod within 1.0m of the bottom of the pile is 30-60 seconds in order to improve the quality of the bottom end of the pile, and rotary spraying parameters can be adjusted according to different soil layers in the rotary spraying lifting process; and finishing the construction of each high-pressure jet grouting pile in the vertical reinforcing area of the high-pressure jet grouting pile.

And after the construction of the high-pressure jet grouting pile is completed, drilling and grouting are carried out to horizontally reinforce the area.

(4) Positioning grouting holes in a drilling grouting horizontal reinforcement area: and (3) extending the shield starting well underground continuous wall to 15-20 m from the inlet of the shield starting well underground continuous wall as a starting point, and extending the lower end of the shield tunnel structure and the outer edges of two sides to 3-5 m.

A plurality of horizontal grouting drill holes arranged at intervals in the horizontal reinforcing area are provided with a plurality of rows from top to bottom, the distance between every two adjacent rows is 900-1100 mm, the distance between every two adjacent holes in the same row is 700-800 mm, each horizontal grouting drill hole in each row at the top is horizontal, each horizontal grouting drill hole in each row at the middle is inclined to the lower end by 5-6% of slope, and each horizontal grouting drill hole in each row at the bottom is inclined to the lower end by 8-9% of slope. The grouting hole sites are all radial inclined hole sites, so lofting positioning is required according to the three-dimensional coordinates of the hole sites during lofting.

The method comprises the steps of firstly lofting the center of a hole position on an underground continuous wall in a hole by using a total station, marking the center of a pile position by using a shooting nail, lofting the allowable deviation of +/-5 mm, lofting the center of an extension line of a grouting hole on the other side wall surface of a structural wall, positioning a drilling machine by using a two-point connecting line, rechecking the direction and the elevation of a drill rod by using the total station when the drilling machine drills a hole, and tapping and drilling after the position is confirmed to be accurate.

(5) Drilling a horizontal reinforcing area by drilling and grouting, and installing an orifice pipe: and (3) arranging an orifice pipe in each drill hole, wherein the diameter of the hole of the grouting hole is 110mm, the diameter of the orifice pipe is 108mm, the wall thickness of the orifice pipe is 5mm, the pipe length is 3m, after the positioning of a drilling machine is tested again, the hole is drilled to 2.8m, after a drill rod is withdrawn, the orifice pipe is jacked into the hole by the drilling machine and anchored by an anchoring agent, and a quick joint is welded on the outer side of the orifice pipe.

(6) The installation of the water drainage and grout stopping device in the horizontal reinforcing area for drilling and grouting comprises the steps of drilling through an orifice pipe to a designed depth after the orifice pipe is fixedly installed, stopping drilling, dismounting sections of drill rods from a drilling machine, sleeving a water drainage device, a grout stopping plug and a hollow pressure plate on the drill rods, connecting the water drainage device and an orifice through a quick connector, arranging the grout stopping plug in the water drainage device, connecting and pressing the bolt pressure reducing plate and the water drainage device to enable the grout stopping plug to block a gap between the drill rods and the water drainage device, wherein the orifice pipe, the drilling machine, the drill rods, the water drainage device, the grout stopping plug, the hollow pressure plate, the quick connector, the bolt pressure reducing plate and the like are all provided with equipment.

(7) And (3) retreating grouting construction of the drilling grouting horizontal reinforcement area: the grouting material is cement-water glass slurry, and the volume ratio of the mixture ratio is = 1: 1.0, cement paste water cement ratio of 0.8: 1-1: 1, the water glass is water glass with the modulus of 2.6-2.8 and the baume degree of 35 degrees, which meets the national requirements, and the density of 1.40-1.46 g/cm3The cement is 42.5 ordinary Portland cement with initial setting time of more than 3h and longer final setting time.

The grouting range can be such that the upper boundary does not exceed the shield excavation contour line and is arranged at the bottom end of the grouting area of the high-pressure jet grouting pile to form an oblique contour line, and the horizontal reinforcing area and the vertical reinforcing area are superposed at the position below the shield excavation range to form an L-shaped combined type reinforcing curtain structure.

The grouting pipeline connection adopts the traditional technology that: the cement and the water enter the slurry pool after being stirred by the stirrer, and then the slurry is uniformly mixed with the water glass slurry in the grouting pump and stored in the material storage tank, and then is pressed into the grouting holes through the mixer, the high-pressure valve and the slurry stop plug in sequence.

When grouting is started, after grout flows to the bottom of a hole through a drill rod, the hole between the walls of the drill hole is filled, the grout is diffused into the stratum, the drill rod is kept to rotate in the grouting process to avoid grout cementation, after the grouting pressure reaches a designed value, a grout stop plug is loosened, the drill rod is retreated to the position below the drill rod, the extra drill rod outside the hole is removed, then the grout stop plug is screwed down, grouting is continued, and the grouting is repeated and retreated until the grouting of the hole position is completed.

And repeating the steps to finish grouting of each hole position of the drilling grouting horizontal reinforcing area.

As shown in fig. 5, the grouting holes are all radially inclined holes, which are inclined radially in an explosive manner from the horizontal direction of the inlet of the underground continuous wall of the shield starting well to both sides, or inclined radially in an explosive manner from the horizontal direction of the inlet of the underground continuous wall of the shield starting well to both sides and the lower end.

(8) And (4) reinforcing effect inspection: the standard value of the unconfined compressive strength of the high-pressure jet grouting pile in 28 days is not less than 1Mpa, and a drilling and coring method is adopted.

Drilling and coring, namely drilling a rock core in a constructed consolidation reinforcing area body, making the rock core into a standard test piece, carrying out an indoor physical and mechanical property test, checking the uniformity and impermeability of an internal pile body, and qualitatively evaluating the grouting effect, drilling a hole in a grouting area through a geological drilling machine, taking the rock core out of a stratum as completely as possible, wherein the coring strength is not less than 1.0MPa, the core strength detection in the reinforcing area is qualified after 28d, no obvious water leakage condition exists when holes are drilled, and the maximum ground settlement/uplift is less than 30mm after the shield is started.

In a word, the method is used for making up the defect of a single reinforced structure of the shield end and improving the reinforcing effect of the shield starting end, has the advantages of simple structure, good reinforcing quality, high construction efficiency, cost saving, time saving, labor saving and good use effect, and can be used by pushing .

Claims (7)

  1. The combined reinforcing structure for the shield initiating end head is characterized by comprising a high-pressure jet grouting pile vertical reinforcing area and a drilling and grouting horizontal reinforcing area, wherein:
    the high-pressure jet grouting pile vertical reinforcing area: the vertical reinforcement area ranges from 15-20 m outside a shield starting well underground continuous wall in the horizontal direction and 3-5 m outside the outer edge of a shield tunnel structure, the vertical direction ranges from 3-5 m above the top of a tunnel to 3-5 m below the bottom of the tunnel, two rows of closed edge walls formed by constructing high-pressure rotary jet grouting piles in advance are arranged at the edge of the vertical reinforcement area, the reinforcement depth of the closed edge walls reaches the bottom of the vertical reinforcement area, a closed space is formed in the vertical reinforcement area by the closed edge walls, the radius of each pile of the two rows of high-pressure rotary jet grouting piles forming the closed edge walls is 400mm, the distance between the centers of the adjacent high-pressure rotary jet grouting piles is 650mm, and the pile edges of the adjacent high-pressure rotary jet grouting piles are mutually occluded by 150 mm;
    a plurality of high-pressure jet grouting piles are arranged in the closed space at intervals, the radius of each pile in the closed space is 400mm, the distance between the centers of the adjacent high-pressure jet grouting piles is 650mm, and the edges of the adjacent high-pressure jet grouting piles are mutually meshed by 150 mm;
    the extension length of the pile bottom end of each high-pressure jet grouting pile close to the underground continuous wall of the shield starting well in the closed space is greater than the extension length of the pile bottom end of each high-pressure jet grouting pile far away from the underground continuous wall of the shield starting well;
    drilling and grouting horizontal reinforcement area: the shield tunneling reinforcing method is used for horizontally reinforcing a shield starting end, a horizontal reinforcing area horizontally inclines outwards or horizontally inclines downwards from an opening of the shield starting end of the underground continuous wall shield along a shield tunneling contour line, the range of the horizontal reinforcing area is 15-20 m from the horizontal direction of the shield starting well underground continuous wall, the range of the lower end of a shield tunnel structure and the range of 3-5 m from the outer edges of two sides, the upper boundary of the horizontal reinforcing area is lower than the upper end of the shield tunneling contour line, the lower boundary of the horizontal reinforcing area is lower than the bottom end of the shield tunneling contour line to form an oblique contour line, the horizontal reinforcing area and a vertical reinforcing area are overlapped below the shield tunneling range to form an L-shaped combined reinforcing curtain structure, and the horizontal reinforcing area is formed by a plurality of horizontal grouting drill holes which are arranged at intervals in the horizontal reinforcing area and mixed cement mortar is pressed into the horizontal.
  2. 2. The combined reinforcing structures at the shield starting end according to claim 1, wherein the bottom end of each high pressure jet grouting pile extends to the lower end of the shield tunnel structure by 3-5 m.
  3. 3. The kinds of shield starting end combined reinforced structure of claim 1, wherein the high pressure jet grouting pile comprises reinforced slurry pressure 2-5 MPa, air pressure 0.6-0.8 MPa, water pressure greater than 30MPa, rotation speed 8-12 rpm, cement slurry flow rate greater than or equal to 70L/min, and air flow rate 60-80 m3And h, the lifting speed is 6-12 cm/min, the slurry material adopts cement slurry, the water cement ratio is 1.0-1.5, the specific gravity of the cement slurry poured into the slurry material is 1.5-1.6, and the specific gravity of the returned slurry is 1.2-1.3.
  4. 4. The combined reinforcing structure for shield starting end according to claim 1, wherein the extension length of the pile bottom of each high pressure jet grouting pile in the enclosed space gradually decreases from 5m below the bottom of the tunnel to 3m from the underground continuous wall of the shield starting well to the outside.
  5. 5. The combined reinforcing structure for the shield initiation end according to claim 1, wherein the plurality of spaced horizontal grouting drill holes in the horizontal reinforcing area are arranged in a plurality of rows from top to bottom, the distance between adjacent rows is 900-1100 mm, the distance between two adjacent holes in the same row is 700-800 mm, each horizontal grouting drill hole in each row at the top is kept horizontal, each horizontal grouting drill hole in each row at the middle is inclined to the lower end by a slope of 5-6%, and each horizontal grouting drill hole in each row at the bottom is inclined to the lower end by a slope of 8-9%.
  6. 6, construction methods for realizing shield initiating end combined reinforced structure of claim 1, characterized by comprising the following steps:
    (1) construction preparation: preparing a drilling pile machine, cement for grouting, a reservoir, water glass slurry, a stirrer, a grouting pump, a mixer, an air compressor, a high-pressure pump and a grout stopping plug at a construction site; the construction of a drilling and grouting horizontal reinforcement area is carried out in an initial well, and a support needs to be erected in the initial well;
    (2) before construction, in the ground range of the vertical reinforced area, namely the ground range of 15-20 m outside the underground continuous wall of the shield initial well in the horizontal direction and the ground range of 3-5 m outside the outer edge of the shield tunnel structure, measuring a control point of the construction of the jet grouting pile by using a total station, after a repeated measurement and line inspection is qualified, laying a pile position on the spot by using a steel ruler and a measuring line, nailing by using a bamboo stick, and using to stick a stick, so that the displacement deviation of the center of a pile hole is ensured to be less than 30 mm;
    the pile machine is centered and leveled according to the lofting point position, the verticality of the pile machine is adjusted, the condition that a drill rod is required to be consistent with a pile position , the deviation is within 10mm, the drilling verticality is less than 1 percent,
    before drilling, an air compressor and a slurry pump are required to be debugged, so that the equipment can normally operate; checking the length of the drill rod, marking a depth line beside the drilling tower by using red paint, and ensuring that the elevation of the bottom of the hole meets the design depth;
    (3) drilling and jet grouting lifting of a vertical reinforcing area of the high-pressure jet grouting pile: before drilling, an air compressor and a slurry pump are required to be debugged to ensure that the equipment runs normally; checking the length of the drill rod, marking a depth line beside the drilling tower by using red paint, and ensuring that the elevation of the bottom of the hole meets the design depth; firstly, trial spraying is carried out on the ground during the construction of the drilling machine, after the trial running of the drilling machine is normal, the drilling machine starts to guide holes to drill, the number of drill rod sections is recorded in detail during the drilling process, and the accuracy of the drilling depth is ensured;
    firstly, constructing two rows of closed edge walls formed by high-pressure rotary jet grouting piles, wherein the reinforcing depth of the closed edge walls reaches the bottom of a vertical reinforcing area, the closed edge walls form a closed space in the vertical reinforcing area, the radius of each pile of the two rows of high-pressure rotary jet grouting piles forming the closed edge walls is 400mm, the distance between the centers of the adjacent high-pressure rotary jet grouting piles is 650mm, and the pile edges of the adjacent high-pressure rotary jet grouting piles are mutually occluded by 150 mm; the closed edge wall is formed by adopting phi 400 triple-tube high-pressure rotary jet grouting piles, the reinforcing slurry pressure is 2-5 MPa, the air pressure is 0.6-0.8 MPa, the water pressure is greater than 30MPa, the rotating speed is 8-12 rpm, the cement slurry flow is greater than or equal to 70L/min, and the air flow is 60-80 m3The lifting speed is 6-12 cm/min, the slurry material is cement slurry, the water cement ratio is 1.0-1.5, the specific gravity of the cement slurry poured into the slurry material is 1.5-1.6, and the specific gravity of the returned slurry is 1.2-1.3;
    after the high-pressure jet grouting piles of the closed edge wall reach fixed strength, constructing the high-pressure jet grouting piles in the closed edge wall, wherein the radius of each pile in the closed space is 400mm, the pile center distance between adjacent high-pressure jet grouting piles is 650mm, and the pile edges of the adjacent high-pressure jet grouting piles are mutually occluded by 150 mm;
    the extension length of the pile bottom end of each high-pressure jet grouting pile close to the underground continuous wall of the shield starting well in the closed space is greater than the extension length of the pile bottom end of each high-pressure jet grouting pile far away from the underground continuous wall of the shield starting well;
    the rotary spraying lifting requirement of the high-pressure rotary spraying pile is as follows: after the hole is led to the designed depth, the rock core pipe is pulled out, the injection grouting pipe is replaced to be inserted into the preset depth, during the pipe inserting process, water injection and pipe inserting are carried out, the water pressure is not more than 1Mpa, after the injection grouting pipe is inserted into the designed depth, a slurry pump is connected, then rotary spraying is carried out from bottom to top, and simultaneously slurry is cleaned and discharged; when spraying, the rotary spray pipe is gradually lifted after the preset spraying pressure and the preset gunite are reached; in order to ensure the quality of the bottom end of the pile, when the nozzle is sunk to the designed depth, the nozzle is rotated for 10-15 seconds at the original position, and the nozzle is lifted by rotary spraying after the orifice is normally overflowed; the rotation and the lifting of the drill rod are continuously carried out without interruption, the drilling machine breaks down, the lifting of the drill rod and the rotation are stopped to prevent pile breakage and immediately overhaul and remove the fault, the guniting and rotary spraying time of the drill rod within 1.0m of the bottom of the pile is 30-60 seconds in order to improve the quality of the bottom end of the pile, and rotary spraying parameters can be adjusted according to different soil layers in the rotary spraying lifting process; completing the construction of each high-pressure rotary jet grouting pile in the vertical reinforcing area of the high-pressure rotary jet grouting pile;
    after the construction of the high-pressure jet grouting pile is completed, drilling and grouting a horizontal reinforcing area;
    (4) positioning grouting holes in a drilling grouting horizontal reinforcement area: taking an inlet of an underground continuous wall of a shield starting well as a starting point to extend outwards for 15-20 m, and the lower end and the outer edges of two sides of the shield tunnel structure are 3-5 m;
    the method comprises the following steps that a plurality of horizontal grouting drill holes arranged at intervals in a horizontal reinforcing area are provided with a plurality of rows from top to bottom, the distance between every two adjacent rows is 900-1100 mm, the distance between every two adjacent holes in the same row is 700-800 mm, the horizontal grouting drill holes in every row at the top are kept horizontal, the horizontal grouting drill holes in every row at the middle are inclined to the lower end by 5-6% of gradient, the horizontal grouting drill holes in every row at the bottom are inclined to the lower end by 8-9% of gradient, and the grouting holes are radial inclined holes, so that lofting positioning is carried out according to three-dimensional coordinates of the hole positions during lofting;
    (5) drilling a horizontal reinforcing area by drilling and grouting, and installing an orifice pipe: installing an orifice pipe in each drill hole, wherein the diameter of the drill hole of the grouting hole is 110mm, the orifice pipe is a hot-rolled seamless steel pipe with the diameter of 108mm and the wall thickness of 5mm, the pipe length is 3m, after the drill machine is positioned and tested again, the drill hole is drilled to 2.8m, after a drill rod is withdrawn, the orifice pipe is jacked into the hole by the drill machine and anchored by an anchoring agent, and a quick joint is welded on the outer side of the orifice pipe;
    (6) after the orifice pipe is installed and fixed, stopping drilling after the orifice pipe is drilled to the designed depth, removing sections of drill rods from the drilling machine, then sleeving a drainage device, a grout stopping plug and a hollow pressure plate on the drill rods, connecting the drainage device and the orifice through a quick joint, arranging the grout stopping plug in the drainage device, and connecting and pressing the bolt pressure plate and the drainage device to enable the grout stopping plug to block a gap between the drill rods and the drainage device;
    (7) and (3) retreating grouting construction of the drilling grouting horizontal reinforcement area: the grouting material is cement-water glass slurry, and the volume ratio of the mixture ratio is = 1: 1.0, cement paste water cement ratio of 0.8: 1-1: 1, the water glass is water glass with the modulus of 2.6-2.8 and the baume degree of 35 degrees, which meets the national requirements, and the density of 1.40-1.46 g/cm3Selecting common Portland cement with the strength grade of 42.5 and the initial setting time of more than 3 hours and the longer final setting time, enabling the upper boundary not to exceed the shield excavation contour line, and enabling the cement to descend to the bottom end of a grouting area of the high-pressure jet grouting pile to form an oblique contour line, wherein the horizontal reinforcing area and the vertical reinforcing area are overlapped at the position below the shield excavation range to form an L-shaped combined reinforcing curtain structure;
    when grouting is started, after the grout flows to the bottom of a hole through the drill rod, the hole between the walls of the drilled hole is filled, then the grout is diffused into the stratum, the drill rod is kept to rotate in the grouting process to avoid cementing of the grout,
    when the grouting pressure reaches a designed value, loosening the grout stop plug, retreating the drill rod to the lower position, removing the extra drill rod outside the air, then screwing the grout stop plug, continuing grouting, and repeating retreating and grouting repeatedly until grouting at the hole position is completed;
    repeating the steps to finish grouting of each hole position of the drilling grouting horizontal reinforcing area;
    (8) and (4) reinforcing effect inspection: the strength of the high-pressure jet grouting pile requires that the standard value of the unconfined compressive strength of 28 days is not less than 1Mpa, and a drilling and coring method is adopted;
    drilling and coring: drilling a rock core in the constructed consolidation reinforcing area body, making the rock core into a standard test piece, carrying out an indoor physical mechanical property test, checking the uniformity and the impermeability of the internal pile body, qualitatively evaluating the grouting effect,
    and drilling a hole in the grouting area through a geological drilling machine, taking out a core from the stratum as completely as possible, wherein the core strength is not less than 1.0MPa, the core strength detection in the reinforced area 28d is qualified, no obvious water leakage condition exists when the hole is opened, and the maximum ground settlement/uplift is less than 30mm after the shield is started.
  7. 7. The construction method according to claim 6, wherein: the grouting hole sites are all radial inclined hole sites, and the grouting hole sites are radially inclined from the horizontal direction of the inlet of the underground continuous wall of the shield starting well to both sides in an explosive manner, or from the horizontal direction of the inlet of the underground continuous wall of the shield starting well to both sides and the lower end in an explosive manner.
CN201910916702.7A 2019-09-26 2019-09-26 shield originating end combined type reinforcing structure and construction method thereof CN110735642A (en)

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