CN108442382B - In-situ protection and enclosure soil-retaining structure for pressure pipeline crossing deep foundation pit and construction method - Google Patents

In-situ protection and enclosure soil-retaining structure for pressure pipeline crossing deep foundation pit and construction method Download PDF

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Publication number
CN108442382B
CN108442382B CN201810181717.9A CN201810181717A CN108442382B CN 108442382 B CN108442382 B CN 108442382B CN 201810181717 A CN201810181717 A CN 201810181717A CN 108442382 B CN108442382 B CN 108442382B
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pile
jet grouting
retaining
construction
mjs
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CN108442382A (en
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李应姣
张志冰
彭刚
龙华东
谭桂平
周坤
李�杰
曹铁军
田诗国
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Urban Mass Transit Engineering Co Ltd Of China Railway 11th Bureau Group
China Railway 11th Bureau Group Co Ltd
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Urban Mass Transit Engineering Co Ltd Of China Railway 11th Bureau Group
China Railway 11th Bureau Group Co Ltd
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    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D17/00Excavations; Bordering of excavations; Making embankments
    • E02D17/02Foundation pits
    • E02D17/04Bordering surfacing or stiffening the sides of foundation pits

Abstract

The invention provides a pressure pipeline in-situ protection and enclosure soil-retaining structure traversing a deep foundation pit and a construction method. The construction process of the retaining structure comprises the steps of firstly constructing a first-stage underground continuous wall on two sides of a pipeline to be protected in situ and interrupting the first-stage underground continuous wall at a position close to the pipeline to be protected in situ, then constructing a steel sheet pile supporting structure and a composite pile retaining wall on the outer side of the first-stage underground continuous wall, wherein the composite pile retaining wall is arranged on the outer side of an interruption area and consists of an MJS jet grouting pile reinforcing body consisting of a plurality of mutually-meshed MJS jet grouting piles and a plurality of miniature steel pipe piles inserted into the MJS jet grouting pile reinforcing body, the interruption area is completely shielded, and the steel sheet pile supporting structure consists of two rows of steel sheet piles constructed on two sides of the composite pile retaining wall. The invention greatly reduces the influence on the environment, achieves the effect of enclosing the enclosure structure before the excavation of the foundation pit, effectively reduces the possibility of water seepage, water leakage and collapse at the position of the reverse continuous wall during the excavation of the foundation pit, and increases the safety factor during the excavation of the foundation pit and the construction of the reverse continuous wall.

Description

In-situ protection and enclosure soil-retaining structure for pressure pipeline crossing deep foundation pit and construction method
Technical Field
The invention relates to the field of in-situ pipeline protection in underground structure construction, in particular to a pressure pipeline in-situ protection and retaining and soil-retaining structure construction method suitable for a high-standard stratum to cross a deep foundation pit.
Background
With the upgrading and transformation of urbanization, the construction of towanization infrastructure in China is accelerated, particularly the construction of urban subway rail transit is more rapid, the subway construction inevitably brings great influence on the original various municipal pipelines, the inconvenience is brought to the original planning and the pipeline layout construction, and the problems of pipeline moving and transformation and how to protect the existing pipelines become difficult problems in the subway construction.
Pipelines in some special areas cannot be changed at will, for example, an airport oil pipeline with the diameter phi 273 traverses a foundation pit on a construction site of a certain subway line in Hangzhou, the subway station is an underground three-layer island station, an oil pipeline on the north side of the station runs to obliquely pass through a main body structure of another station, the diameter phi 273 of the oil pipeline is about 3.4m of the buried depth, the length of an oblique span reaches 29m, the oil pipeline is a unique oil supply pipeline of the airport and cannot be changed, and only in-situ suspension protection can be performed due to the construction of the subway structure. However, the in-situ protection of the pipeline also causes great influence on the construction of the building enclosure of the station, so that the building enclosure at the position cannot be completely closed, and the building enclosure below the oil pipeline can be constructed only by adopting a top-down method of digging while excavating when the foundation pit is excavated. Before the reverse construction method is used for construction, the open position of the enclosure structure needs to be reinforced and stopped in advance, so that the safety risks of water gushing, sand gushing, landslide and the like during reverse construction are prevented. However, the foundation pit is an ultra-deep foundation pit with the excavation depth of 26m, the stratum is also a high-standard-penetration stratum with the standard penetration of more than 45, and the conventional double-pipe and triple-pipe rotary-spraying reinforcement method hardly has a reinforcement effect at the depth and the stratum and cannot meet the requirements of site construction, and the important degree of the pipeline above the enclosure structure also provides a harsh requirement for the deformation displacement of the pipeline in the reinforcement process.
Disclosure of Invention
The invention provides a construction method of a pressure pipeline in-situ protection and enclosure retaining structure suitable for a weathered high-grade penetrated stratum to cross a deep foundation pit, which is based on the defects of the prior art.
The technical scheme provided by the invention is as follows: the pressure pipeline in-situ protection and enclosure retaining structure traversing the deep foundation pit comprises a first-stage underground continuous wall constructed on two sides of a pipeline to be protected in situ, wherein the first-stage underground continuous wall forms an interruption area near the pipeline to be protected in situ, a retaining wall construction area is dug outside the interruption area, the width of the retaining wall construction area is greater than that of the interruption area, the bottom surface of the retaining wall construction area is lower than that of the pipeline to be protected in situ, and a steel sheet pile supporting structure and a composite pile retaining wall are constructed in the retaining wall construction area; the composite pile retaining wall is arranged outside the interruption area, and consists of an MJS jet grouting pile reinforcing body consisting of a plurality of mutually meshed MJS jet grouting piles and a plurality of miniature steel pipe piles inserted into the MJS jet grouting pile reinforcing body, wherein the width of the miniature steel pipe piles is larger than that of the interruption area, the interruption area is completely shielded, the plurality of mutually meshed MJS jet grouting piles of the MJS jet grouting pile reinforcing body are arranged into one or more rows, each row of MJS jet grouting piles are mutually meshed, the edge of the MJS jet grouting pile close to the first-stage underground continuous wall is mutually meshed with the first-stage underground continuous wall, and the pile bottoms of the MJS jet grouting piles are not higher than the wall bottom of the first-stage underground continuous wall; the steel sheet pile supporting structure is composed of two rows of steel sheet piles constructed on two sides of a composite pile retaining wall, wherein the two rows of steel sheet piles are respectively arranged at the edge position of a retaining wall construction area and extend into an excavation side slope on the outer side of the retaining wall construction area.
The invention has the following excellent technical scheme: the bottom of each MJS jet grouting pile forming the composite pile retaining wall and the bottom of the first-stage underground continuous wall are on the same plane, after a plurality of MJS jet grouting piles are constructed to form a reinforcing body, a plurality of holes are formed in the MJS jet grouting pile reinforcing body in a hole leading mode, a micro steel pipe pile is inserted into each hole, and the micro steel pipe pile reinforcing body and the plurality of micro steel pipe piles are consolidated into a whole through grouting.
The invention has the following excellent technical scheme: the bottom surface of the retaining wall construction area is arranged at a position of at least 1m below the pipeline to be protected in situ, and the gradient of an excavation side slope on the outer side of the retaining wall construction area is 1: 1.
The invention has the following excellent technical scheme: the steel sheet pile supporting structure is composed of two rows of Larsen steel sheet piles with the length of 9-10 m, the distance between each two rows of Larsen steel sheet piles and a pipeline to be protected in situ is larger than 5m, and the distance between the two rows of Larsen steel sheet piles is larger than the width of a composite pile retaining wall.
The invention has the following excellent technical scheme: the MJS jet grouting pile is a high-pressure jet grouting pile constructed by adopting an MJS construction method, the jet grouting angle of each MJS jet grouting pile is 360 degrees, the pile diameter is 1500mm, the spacing is 1100mm, the cement mixing amount is 25-30 percent, and the pile top is 1000mm below a pipeline; each miniature steel pipe pile is made of Q235 steel pipes, the diameter of each miniature steel pipe pile is 108mm, the wall thickness of each miniature steel pipe pile is 4mm, and the distance between pile bodies is 450 mm-500 mm.
The invention has the following excellent technical scheme: the height of each miniature steel pipe pile is equal to that of the MJS jet grouting pile, and the miniature steel pipe piles are distributed in a quincunx shape and are consolidated with the reinforcing body of the MJS jet grouting pile into a whole through cement.
The invention has the following excellent technical scheme: the width of the interruption region is not more than 2.5m, and a gap more than 0.5m is reserved between two interruption surfaces of the interruption region and the pipeline to be protected in situ.
The invention provides a construction method for in-situ protection and retaining of a pressure pipeline traversing a deep foundation pit, which is characterized by comprising the following specific steps of:
(1) constructing first-stage underground continuous walls on two sides of a pipeline to be protected in situ, wherein the first-stage underground continuous walls are interrupted near the pipeline to be protected in situ, and the interruption distance is controlled to be not more than 2.5 m;
(2) constructing a row of Larsen steel sheet piles outside the range of 5m of each of two sides of the outer part of the first-stage underground continuous wall by using a static pressure machine to form a steel sheet pile supporting structure;
(3) the Larsen steel sheet pile encloses the excavation area, is far away from underground continuous wall side, and the slope of the open cut area of putting the slope is 1:1, excavating earthwork within the enclosing range of a steel sheet pile supporting structure in a manual layered and segmented mode, and stopping excavating to the position at least 1m below a pipeline to be protected in situ, so that the part, to be protected in situ, of the pipeline, which is arranged on the outer side of a first-stage underground continuous wall is suspended;
(4) after the in-situ protection pipeline is suspended and protected, constructing a composite pile retaining wall at a position, corresponding to the interruption area, outside the first-stage underground continuous wall, firstly constructing one or more rows of high-pressure jet grouting piles by adopting an MJS construction method, forming a jet grouting pile reinforcing body outside the interruption area, then drilling a plurality of holes on the jet grouting pile reinforcing body by adopting a drilling machine, inserting a micro steel pipe pile into each hole, then grouting and filling, and consolidating the micro steel pipe piles and the jet grouting pile reinforcing body into a compact whole to finish the construction of the whole retaining structure;
(5) after the construction of the retaining wall structure formed by combining the MJS jet grouting piles and the double rows of inserted steel pipe piles is finished, after the earthwork of the foundation pit of the open cut station is excavated by the depth of 1.5-2 m in a layering way, the construction of a first-stage underground diaphragm wall interrupted area is finished by adopting a conventional reverse construction method.
The further technical scheme of the invention is as follows: the concrete construction process of the jet grouting pile reinforcing body in the step (4) is as follows:
a. firstly, lofting a pile position of an MJS jet grouting pile by using a total station, then guiding a hole by using a geological drilling machine, wherein the depth of the guiding hole is 1-2 m deeper than the design depth, and the wall is protected by bentonite slurry during guiding the hole, and then embedding a low-strength PVC sleeve pipe with the same depth as the pile in the hole for hole wall protection after the guiding of the hole is completed;
b, the MJS pile driver is in place, the pile driver is leveled and centered, the perpendicularity of the pile driver is adjusted, and the error of the drilling perpendicularity is less than 0.5 percent; the position of a drill rod of the pile machine is consistent with that of a pile core, the deviation is within 10mm, then the construction of MJS jet grouting pile is carried out, the grouting pressure is more than or equal to 40MPa, the air pressure is 0.5-0.8 MPa, the suck-back pressure is 8-25 MPa, and the air flow is as follows: 8-10 m3/min, and 25-30% of cement mixing amount;
and c, when the micro steel pipe pile is constructed after the construction of the MJS jet grouting pile is completed to form a jet grouting pile reinforcing body, firstly, a geological drilling machine is adopted to guide holes on the jet grouting pile reinforcing body, the micro steel pipe pile is processed in the field, the micro steel pipe pile is naturally placed into the pre-drilled holes through a crane, the micro steel pipe pile is fixed on the ground through hanging ribs according to the designed elevation, a grouting pipe is inserted from the top to the bottom of the steel pipe to perform grouting filling, and the steel pipe and the reinforcing body are consolidated into a compact whole.
The invention has the following excellent technical scheme: in the step (4), the diameter of each MJS jet grouting pile of the jet grouting pile reinforcing body is 1500mm, the distance is 1100mm, and the pile top is 1000mm below the pipeline; each miniature steel pipe pile is made of a Q235 steel pipe, the diameter of each miniature steel pipe pile is 108mm, the wall thickness of each miniature steel pipe pile is 4mm, and the distance between pile bodies is 500 mm.
The retaining structure is suitable for a weathered high-elevation through-stratum ultra-deep foundation pit and mainly comprises Larsen steel sheet piles, MJS jet grouting piles and micro steel pipe piles, first-stage underground continuous walls on two sides of an oil conveying pipe are constructed firstly, the continuous walls are interrupted near the oil conveying pipe, and the continuous walls in the interrupted area can be constructed by adopting a reverse construction method after the MJS composite retaining structure is completed; two rows of steel sheet piles are constructed on two sides of the pipeline outside the foundation pit, the overlying soil of the pipeline is excavated by manual slope setting, and the pipeline is exposed and protected; and constructing the MJS jet grouting pile on the outer side of the reverse construction diaphragm wall, inserting the micro steel pipe pile into the hole in a hole guiding mode after reinforcing, and solidifying the micro steel pipe pile and the MJS jet grouting pile into an integral composite stress structure capable of resisting shear and bending.
The invention has the beneficial effects that:
1. the invention adopts MJS jet grouting pile to reinforce soil body, which is based on the traditional high-pressure jet grouting process, adopts a unique porous pipe and a front end generating device to realize the forced slurry discharge in the hole and the monitoring of the underground pressure, controls the underground pressure by adjusting the forced slurry discharge amount, greatly reduces the influence on the environment, further ensures the pile forming diameter by reducing the underground pressure, and can still achieve good pile forming effect in weathered residual high-grade soil layers.
2. According to the invention, the outer side soil pressure is borne by the MJS pile body and the miniature steel pipe pile together, and the stress mode is similar to a reinforced concrete structure, so that the thickness of the reinforcement of the MJS pile body of the ultra-deep foundation pit is greatly reduced, the construction cost is greatly reduced, and a better economic effect is achieved.
3. According to the invention, through the combined action of the MJS reinforcing body and the continuous wall, the effect of enclosing the enclosure structure is achieved before the foundation pit is excavated, the possibility of water seepage, water leakage and collapse at the position of the reverse continuous wall during excavation of the foundation pit is effectively reduced, and the safety coefficient during excavation of the foundation pit and construction of the reverse continuous wall is increased;
drawings
FIG. 1 is a schematic plan view of the present invention;
fig. 2 is a schematic elevation structure of the present invention.
In the figure: 1-composite pile retaining wall, 1-MJS jet grouting pile, 1-2-miniature steel pipe pile, 2-pipeline to be protected in situ, 3-steel sheet pile supporting structure, 4-excavation slope, 5-interruption area, 6-first-stage underground continuous wall, 7-crown beam, 8-station structure, 9-enclosure inner support and 10-retaining wall construction area.
Detailed Description
The invention is further illustrated by the following figures and examples. As shown in fig. 1, the in-situ protection and retaining structure for pressure pipelines crossing deep foundation pits comprises a first-stage underground continuous wall 6 constructed at two sides of a pipeline 2 to be protected in situ, wherein the first-stage underground continuous wall 6 forms an interruption area 5 near the pipeline 2 to be protected in situ, the width of the interruption area 5 is not more than 2.5m, and a gap more than 0.5m is reserved between two interruption surfaces of the interruption area 5 and the pipeline 2 to be protected in situ, wherein the underground continuous wall at the interruption area is constructed by a reverse method, a retaining wall construction area 10 is firstly constructed before the construction, a retaining wall construction area 10 is dug outside the interruption area 5, the width of the retaining wall construction area 10 is more than the width of the interruption area 5, the bottom surface of the retaining wall construction area is lower than the pipeline 2 to be protected in situ and is at least arranged at a position 1m below the pipeline 2 to be protected in situ, the slope 4 outside the retaining wall construction area 10 is 1:1, the pipeline 2 to be protected in situ is in a suspended state at the lower part. A steel sheet pile supporting structure 3 and a composite pile retaining wall 1 are constructed in the retaining wall construction zone 10.
As shown in fig. 1 and 2, the composite pile retaining wall 1 is arranged outside the interruption region 5, and is composed of an MJS jet grouting pile reinforcement body composed of a plurality of mutually engaged MJS jet grouting piles 1-1 and a plurality of micro steel pipe piles 1-2 inserted into the MJS jet grouting pile reinforcement body, the width of the MJS jet grouting pile reinforcement body is larger than the width of the interruption region 5, and the interruption region 5 is completely shielded, the plurality of mutually engaged MJS jet grouting piles 1-1 of the MJS jet grouting pile reinforcement body are arranged into one or more rows, each row of MJS jet grouting piles 1-1 are mutually engaged, the edge of the MJS jet grouting pile 1-1 close to the first-stage underground continuous wall 6 is mutually engaged with the first-stage underground continuous wall 6, and the pile bottoms of the plurality of MJS jet grouting piles 1-1 are flush with the wall bottom of the first-stage underground continuous wall 6; after a plurality of MJS jet grouting piles 1-1 are constructed to form a reinforcing body, a plurality of holes are formed in the MJS jet grouting pile reinforcing body in a hole guiding mode, a micro steel pipe pile 1-2 is inserted into each hole, the height of each micro steel pipe pile 1-2 is equal to the height of the MJS jet grouting pile 1-1, and the plurality of micro steel pipe piles 1-2 are distributed in a quincunx shape and are consolidated with the MJS jet grouting pile reinforcing body into a whole through cement. The steel sheet pile supporting structure 3 is composed of two rows of Larsen steel sheet piles with the length of 9 m-10 m, which are constructed on two sides of the composite pile retaining wall 1, and the two rows of steel sheet piles are respectively arranged at the edge position of a retaining wall construction area 10 and extend into an excavation slope 4 outside the retaining wall construction area 10. The distance between the two rows of Larsen steel sheet piles and the pipeline 2 to be protected in situ is larger than 5m, and the distance between the two rows of Larsen steel sheet piles is larger than the width of the composite pile retaining wall 1.
The MJS jet grouting pile 1-1 is a high-pressure jet grouting pile constructed by adopting an MJS construction method, wherein the jet grouting angle of each MJS jet grouting pile is 360 degrees, the pile diameter is 1500mm, the interval is 1100mm, the cement mixing amount is 25-30 percent, and the pile top is 1000mm below a pipeline; each miniature steel pipe pile 1-2 is made of Q235 steel pipes, the diameter of each miniature steel pipe pile is 108mm, the wall thickness of each miniature steel pipe pile is 4mm, and the distance between pile bodies is 450 mm-500 mm.
The invention is further explained by combining the embodiment, in the construction of the in-situ protection of the airport oil pipeline of the subway station in Hangzhou, the airport oil pipeline with the diameter phi 273 traverses the foundation pit on the construction site of the station. The station is an underground three-layer island type station, an oil conveying pipe is arranged on the north side of the station and runs obliquely through a main body structure of the north section of the subway station, the diameter of the oil conveying pipe is phi 273, the burial depth is about 3.4m, the oblique span length reaches 29m, the oil conveying pipe is an only oil supply pipeline of a Hangzhou Xiaoshan airport and cannot be changed, and only in-situ suspension protection can be carried out due to the construction of the subway structure.
The subway station geomorphology generally belongs to mountain forward flood plain geomorphology, and mountain forward hillock geomorphology is located on the north side of the station. The fourth stratum is artificial filling layer, flushing-flooding sedimentary layer, river-lake sedimentary layer and residual layer, and the bedrock is three-cascade invasion granite. The change of the underground water level is controlled by factors such as landform, underground water supply source and the like. The stable water level burial depth of the underground water in the station area is 2.10-3.80 m, the average burial depth is about 2.80m, the water level elevation is 23.29-27.49 m, and the average elevation is 24.59 m. The underground water level of the mark section has close relation with seasons, climates, occurrence, supply and drainage of underground water, the underground water level rises to some extent during rainy seasons, the underground water level falls to some extent during dry seasons, and the annual variation range of the water level is 1.00-3.00 m.
Because of the influence of an airport oil pipeline, the underground continuous wall of the station needs to be reversely constructed at the intersection with the oil pipeline, the width of the reverse continuous wall is 2500mm, in order to ensure the construction safety of a foundation pit, the soil body outside the continuous wall needs to be subjected to water stop reinforcement before excavation of the foundation pit, and the special landform at the intersection is added, so that the effect of a general reinforcement method is not good, the inventor adopts the reinforcement method, the construction of the invention adopts MJS construction method piles, test piles are required to be carried out before the construction of the MJS construction method, the test piles select the stratum with the worst reinforcement range, and the construction is carried out after the test piles are completed, and the concrete construction steps are as follows:
(1) constructing first-stage continuous walls 6 on two sides of an in-situ oil conveying pipe to be protected, wherein the first-stage continuous walls 6 are interrupted near the oil conveying pipe, the interruption distance is controlled to be not more than 2.5m, and the interruption area is a reverse continuous wall in the later stage;
(2) for the influence that reduces the high pressure thick liquid of pile foundation construction to defeated oil pipe production, need excavate oil pipe both sides soil body in advance, and it is unsettled to expose the pipeline, the excavation depth is oil pipe below 1m, the foundation ditch east side oil pipe buries deeply and is 2m underground, excavation depth 3m, the defeated oil pipe underground of foundation ditch west side buries deeply 3m, excavation depth 4m, form retaining wall construction zone 10, it is darker to consider defeated oil pipe both sides excavation depth, carry out the steel sheet pile to the oil pipe both sides soil body in advance before the excavation and strut, specifically respectively construct one row of larsen steel sheet pile at the excavation zone edge of the settlement of defeated oil pipe both sides, larsen steel sheet pile adopts static pressure machinery to construct, its concrete construction is as follows:
a. firstly, marking concrete pile positions of the steel sheet piles in sequence, and burying pile positions;
b. positioning according to the initial steel sheet pile on the clamp; the crawler-type hydraulic pile driver is in place; the steel sheet pile adopts Larsen IV type steel sheet pile, the effective pile length of the steel sheet pile is 9 meters;
c. the guide clamp clamps the closure and clamps the steel sheet pile. The safety is provided, and the pile hammer and the steel sheet pile are lifted;
d. adjusting the verticality or inclination of the pile, and accurately positioning;
e. and (5) setting the pile at the well pile position, calibrating the verticality or gradient of the pile and the plane position of the pile, and enabling the pile to sink automatically. If the pile position has errors, pulling up and calibrating in place, and meanwhile, controlling the verticality or inclination of the pile to form the pile;
f. firstly, lightly hammering the pile to a certain depth, and then heavily hammering the pile to the designed depth;
g. measuring deviation and elevation of the pile;
h. clamping the closure mouth of the next steel sheet pile, clamping the pile, lifting the steel sheet pile to adjust the verticality or inclination of the pile and aligning the small tooth mouth of the steel sheet pile;
i. pile descending, pile perpendicularity or inclination and pile plane position calibration are carried out, so that the pile is self-sunk, and if the pile position has errors, the pile is pulled up and calibrated in place; meanwhile, controlling the verticality or inclination of the pile, planting the pile in place, sinking the pile within an error range by error control, and making pile sinking records;
j. and sequentially lifting the steel sheet piles and driving the steel sheet piles in place.
Attention should be paid to: the conditions of peripheral pipelines and structures need to be confirmed before the construction of the steel sheet piles; the steel sheet piles are inspected one by one before piling, rusted and seriously deformed steel sheet piles of the connecting lock catch are removed, and unqualified steel sheet piles can be used after being trimmed and qualified; before piling, coating grease in the locking notch of the steel sheet pile to facilitate driving and pulling out; and measuring and monitoring the inclination of each pile at any time in the inserting and beating process, and pulling and beating when the inclination is overlarge (more than 2%).
(4) After construction of the Larsen steel sheet pile is finished, excavating a side slope according to a preset area, wherein the slope of the open excavation area of the open slope is 1:1, excavating earthwork within the enclosing range of a steel sheet pile supporting structure 3 in a manual layered and segmented mode until the excavation is stopped to a depth to be designed, and suspending the part of a pipeline to be protected in situ, which is arranged on the outer side of a first-stage underground continuous wall;
(5) after an oil delivery pipe is excavated and exposed, constructing a composite pile retaining wall 1 at the outer side of the intersection of the oil delivery pipe and the first-stage continuous wall 6, wherein the composite pile retaining wall is composed of two rows of MJS construction method piles, the solid pile length of each MJS jet grouting pile 1-1 is 28.08m, the reinforcement depth is 8.0m below the bottom of a foundation pit, the piles are mutually occluded, and the joint of the MJS jet grouting pile 1-1 and the first-stage continuous wall 6 is also mutually occluded; before construction, a total station instrument is used for lofting the pile position of the MJS jet grouting pile 1-1, a geological drilling machine is used for guiding holes, the depth of the guiding holes is slightly deeper than the design depth by 1m, rainwater in a weathered and residual stratum is easy to soften and disintegrate, bentonite slurry is used for wall protection during guiding the holes, after the guiding of the holes is completed, low-strength PVC sleeves with the same depth as the piles are embedded in the holes for hole wall protection, then an MJS pile machine is used for construction of the MJS jet grouting pile 1-1, the pile machine is leveled and centered, the perpendicularity of the pile machine is adjusted, and the error of the perpendicularity of the drilling holes is less than; the position of a drill rod of the pile machine is consistent with that of a pile core, the deviation is within 10mm, then construction of the MJS jet grouting pile 1 is carried out, the grouting pressure is not less than 40MPa, the air pressure is 0.5-0.8 MPa, the suck-back pressure is 8-25 MPa, and the air flow is as follows: 8-10 m3/min, and 25-30% of cement mixing amount.
(6) After the construction of the reinforcement body of the MJS jet grouting pile is completed, inserting 3 rows of 108 steel pipe (t is 4mm) miniature steel pipe piles 1-2 into the reinforcement body, specifically, guiding holes on the reinforcement body by adopting a geological drilling machine, processing the miniature steel pipe piles 1-2 in the field in advance, naturally placing the miniature steel pipe piles 1-2 into the pre-drilled holes by a crane, fixing the miniature steel pipe piles 1-2 on the ground by hanging ribs according to the designed elevation, inserting grouting pipes from the top to the bottom of the steel pipes for grouting filling, consolidating the steel pipes and the reinforcement body into a compact whole, and finally constructing a crown beam to complete the construction of the whole composite retaining wall 1;
(5) after the construction of the composite retaining wall 1 is completed, constructing the retaining wall and a pipe beam below an oil pipe, backfilling two sides of the oil pipe by using stone powder to compact, and recovering a pavement; and finally, after the earthwork of the foundation pit of the open cut station is excavated by layers to the depth of 1.5-2 m, the interrupted area part of the underground diaphragm wall at the first stage is constructed by adopting a conventional reverse construction method.
In the embodiment, the MJS jet grouting pile is adopted to reinforce the soil body, the influence on the environment is greatly reduced, the pile forming diameter is further ensured due to the reduction of the underground pressure, a good pile forming effect can be still achieved in a weathered residual high-grade through soil layer, the enclosure structure sealing effect is achieved before the foundation pit is excavated, the possibility of water seepage, water leakage and collapse at the position of the reverse continuous wall during excavation of the foundation pit is effectively reduced, and the safety factor during excavation of the foundation pit and construction of the reverse continuous wall is increased.
The present invention has been described in detail with reference to the above examples, but the description is only for the preferred examples of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.

Claims (10)

1. The utility model provides a pressure pipeline normal position protection and enclosure retaining structure of crossing deep basal pit which characterized in that: the soil retaining structure comprises first-stage underground continuous walls (6) constructed on two sides of a pipeline (2) to be protected in situ, wherein the first-stage underground continuous walls (6) form an interruption area (5) near the pipeline (2) to be protected in situ, a soil retaining wall construction area (10) is dug outside the interruption area (5), the width of the soil retaining wall construction area (10) is larger than that of the interruption area (5), the bottom surface of the soil retaining wall construction area is lower than that of the pipeline (2) to be protected in situ, and a steel sheet pile supporting structure (3) and a composite pile soil retaining wall (1) are constructed in the soil retaining wall construction area (10); the composite pile retaining wall (1) is arranged outside the interruption area (5), consists of an MJS jet grouting pile reinforcement body consisting of a plurality of MJS jet grouting piles (1-1) which are mutually meshed and a plurality of miniature steel pipe piles (1-2) inserted in the MJS jet grouting pile reinforcement body, the width of the composite pile retaining wall is larger than the width of the interruption area (5), the interruption area (5) is completely shielded, the plurality of MJS jet grouting piles (1-1) which are mutually meshed of the MJS jet grouting pile reinforcement body are arranged into one or more rows, each row of MJS jet grouting piles (1-1) are mutually meshed, the edge of the MJS jet grouting pile (1-1) close to the first-stage underground continuous wall (6) is mutually meshed with the first-stage underground continuous wall (6), and the pile bottom of the plurality of MJS jet grouting piles (1-1) is not higher than the wall bottom of the first-stage underground continuous wall (6); the steel sheet pile supporting structure (3) is composed of two rows of steel sheet piles constructed on two sides of the composite pile retaining wall (1), and the two rows of steel sheet piles are respectively arranged at the edge position of a retaining wall construction area (10) and extend into an excavation side slope (4) on the outer side of the retaining wall construction area (10).
2. The in-situ protection and containment soil guard structure for the pressure pipeline crossing the deep foundation pit according to claim 1, wherein: the bottom of each MJS jet grouting pile (1-1) forming the composite pile retaining wall (1) and the bottom of the first-stage underground continuous wall (6) are on the same plane, after a plurality of MJS jet grouting piles (1-1) are constructed to form a reinforcing body, a plurality of holes are formed in the MJS jet grouting pile reinforcing body in a hole leading mode, a micro steel pipe pile (1-2) is inserted into each hole, and the micro steel pipe pile reinforcing body and the plurality of micro steel pipe piles (1-2) are consolidated into a whole through grouting.
3. The in-situ protection and containment soil guard structure for pressure pipelines crossing deep foundation pits according to claim 1 or 2, wherein: the bottom surface of the retaining wall construction area (10) is arranged at a position of at least 1m below the pipeline (2) to be protected in situ, and the gradient of an excavation side slope (4) on the outer side of the retaining wall construction area (10) is 1: 1.
4. The in-situ protection and containment soil guard structure for pressure pipelines crossing deep foundation pits according to claim 1 or 2, wherein: the steel sheet pile supporting structure (3) is composed of two rows of Larsen steel sheet piles with the length of 9-10 m, the distance between the two rows of Larsen steel sheet piles and the pipeline (2) to be protected in situ is larger than 5m, and the distance between the two rows of Larsen steel sheet piles is larger than the width of the composite pile retaining wall (1).
5. The in-situ protection and containment soil guard structure for pressure pipelines crossing deep foundation pits according to claim 1 or 2, wherein: the MJS jet grouting pile (1-1) is a high-pressure jet grouting pile constructed by adopting an MJS construction method, wherein the jet grouting angle of each MJS jet grouting pile is 360 degrees, the pile diameter is 1500mm, the distance is 1100mm, the cement mixing amount is 25-30 percent, and the pile top is 1000mm below a pipeline; each miniature steel pipe pile (1-2) is made of a Q235 steel pipe, the diameter of each miniature steel pipe pile is 108mm, the wall thickness of each miniature steel pipe pile is 4mm, and the distance between pile bodies is 450 mm-500 mm.
6. The in-situ protection and containment soil guard structure for pressure pipelines crossing deep foundation pits according to claim 1 or 2, wherein: the height of each micro steel pipe pile (1-2) is equal to that of the MJS jet grouting pile (1-1), and the plurality of micro steel pipe piles (1-2) are distributed in a quincunx shape and are consolidated with the reinforcing body of the MJS jet grouting pile into a whole through cement.
7. The in-situ protection and containment soil guard structure for pressure pipelines crossing deep foundation pits according to claim 1 or 2, wherein: the width of the interruption region (5) is not more than 2.5m, and a gap which is more than 0.5m is reserved between two interruption surfaces of the interruption region (5) and the pipeline (2) to be protected in situ.
8. A construction method for in-situ protection and enclosure of a pressure pipeline traversing a deep foundation pit is characterized by comprising the following specific steps:
(1) constructing first-stage underground continuous walls on two sides of a pipeline to be protected in situ, wherein the first-stage underground continuous walls are interrupted near the pipeline to be protected in situ, and the interruption distance is controlled to be not more than 2.5 m;
(2) constructing a row of Larsen steel sheet piles outside the range of 5m of each of two sides of the outer part of the first-stage underground continuous wall by using a static pressure machine to form a steel sheet pile supporting structure;
(3) the Larsen steel sheet pile encloses the excavation area, is far away from underground continuous wall side, and the slope of the open cut area of putting the slope is 1:1, excavating earthwork within the enclosing range of a steel sheet pile supporting structure in a manual layered and segmented mode, and stopping excavating to the position at least 1m below a pipeline to be protected in situ, so that the part, to be protected in situ, of the pipeline, which is arranged on the outer side of a first-stage underground continuous wall is suspended;
(4) after the in-situ protection pipeline is suspended and protected, constructing a composite pile retaining wall at a position, corresponding to the interruption area, outside the first-stage underground continuous wall, firstly constructing one or more rows of high-pressure jet grouting piles by adopting an MJS construction method, forming a jet grouting pile reinforcing body outside the interruption area, then drilling a plurality of holes on the jet grouting pile reinforcing body by adopting a drilling machine, inserting a micro steel pipe pile into each hole, then grouting and filling, and consolidating the micro steel pipe piles and the jet grouting pile reinforcing body into a compact whole to finish the construction of the whole retaining structure;
(5) after the construction of the retaining wall structure formed by combining the MJS jet grouting piles and the double rows of inserted steel pipe piles is finished, after the earthwork of the foundation pit of the open cut station is excavated by the depth of 1.5-2 m in a layering way, the construction of a first-stage underground diaphragm wall interrupted area is finished by adopting a conventional reverse construction method.
9. The construction method for in-situ protection and containment of a soil retaining structure of a pressure pipeline crossing a deep foundation pit according to claim 8, wherein the concrete construction process of the jet grouting pile reinforcement body in the step (4) is as follows:
a. firstly, lofting a pile position of an MJS jet grouting pile by using a total station, then guiding a hole by using a geological drilling machine, wherein the depth of the guiding hole is 1-2 m deeper than the design depth, and the wall is protected by bentonite slurry during guiding the hole, and then embedding a low-strength PVC sleeve pipe with the same depth as the pile in the hole for hole wall protection after the guiding of the hole is completed;
b, the MJS pile driver is in place, the pile driver is leveled and centered, the perpendicularity of the pile driver is adjusted, and the error of the drilling perpendicularity is less than 0.5 percent; the position of a drill rod of the pile machine is consistent with that of a pile core, the deviation is within 10mm, then the construction of MJS jet grouting pile is carried out, the grouting pressure is more than or equal to 40MPa, the air pressure is 0.5-0.8 MPa, the suck-back pressure is 8-25 MPa, and the air flow is as follows: 8-10 m3/min, and 25-30% of cement mixing amount;
and c, when the micro steel pipe pile is constructed after the construction of the MJS jet grouting pile is completed to form a jet grouting pile reinforcing body, firstly, a geological drilling machine is adopted to guide holes on the jet grouting pile reinforcing body, the micro steel pipe pile is processed in the field, the micro steel pipe pile is naturally placed into the pre-drilled holes through a crane, the micro steel pipe pile is fixed on the ground through hanging ribs according to the designed elevation, a grouting pipe is inserted from the top to the bottom of the steel pipe to perform grouting filling, and the steel pipe and the reinforcing body are consolidated into a compact whole.
10. A construction method for in-situ protection and containment of a soil retaining structure of a pressure pipeline crossing a deep foundation pit according to claim 8 or 9, wherein: in the step (4), the diameter of each MJS jet grouting pile of the jet grouting pile reinforcing body is 1500mm, the distance is 1100mm, and the pile top is 1000mm below the pipeline; each miniature steel pipe pile is made of a Q235 steel pipe, the diameter of each miniature steel pipe pile is 108mm, the wall thickness of each miniature steel pipe pile is 4mm, and the distance between pile bodies is 500 mm.
CN201810181717.9A 2018-03-06 2018-03-06 In-situ protection and enclosure soil-retaining structure for pressure pipeline crossing deep foundation pit and construction method Active CN108442382B (en)

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CN109723065A (en) * 2019-02-26 2019-05-07 济南轨道交通集团有限公司 Deep basal pit freezing partly reinforced construction method in bracing means and rich water sandy pear variety
CN110318401A (en) * 2019-06-05 2019-10-11 中铁七局集团有限公司 Suitable for the construction method to open cut area large size pipeline in-situ conservation and pattern foundation pit supporting structure
CN110158649B (en) * 2019-06-05 2020-10-23 浙江交工集团股份有限公司 Construction method for adjacent underground pipeline during open caisson sinking construction
CN110593264B (en) * 2019-08-01 2021-02-26 中建五局土木工程有限公司 Excavation construction method for underground pipeline in-situ protection long and narrow deep foundation pit

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