CN101285309A - Compound support method for deep foundation pit of tall buildings - Google Patents

Compound support method for deep foundation pit of tall buildings Download PDF

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Publication number
CN101285309A
CN101285309A CNA2008100243690A CN200810024369A CN101285309A CN 101285309 A CN101285309 A CN 101285309A CN A2008100243690 A CNA2008100243690 A CN A2008100243690A CN 200810024369 A CN200810024369 A CN 200810024369A CN 101285309 A CN101285309 A CN 101285309A
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CN
China
Prior art keywords
construction
foundation pit
excavation
deep foundation
soil
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CNA2008100243690A
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Chinese (zh)
Inventor
蔡群
丁俊
马建国
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南通华汇建筑工程有限公司
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Application filed by 南通华汇建筑工程有限公司 filed Critical 南通华汇建筑工程有限公司
Priority to CNA2008100243690A priority Critical patent/CN101285309A/en
Publication of CN101285309A publication Critical patent/CN101285309A/en

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Abstract

The invention provides a method for compositely supporting deep foundation pits of a high-rise building, relating to the architectural engineering technical field, in particular to the foundation engineering technical field. Steps of the invention are as follows: the construction of stirring piles, the construction of leading steel pipe piles, the earth excavation and the construction of slope tendons. According to field conditions, geologic conditions and circumferential environments, the composite type support process adopted in the invention is reasonable in technique; after construction, all deformations of foundation pits are in the control range, which ensures the safety of the construction and the safety of buildings around.

Description

Compound support method for deep foundation pit of tall buildings

Technical field

The present invention relates to construction engineering technical field, particularly the foundation engineering technical field.

Background technology

As everyone knows, ground is a building, and the basic guarantee of neighboring buildings.When engineering design height and the excavation of foundation pit degree of depth is big, apart from neighboring buildings nearly (about 7m), and neighboring buildings age of dwellings is long, the job site is narrow and small, in the time of can not adopting the natural discharging slope method to construct, need carry out the safety that supporting guarantees construction period to foundation ditch.

Summary of the invention

The object of the invention is to invent a kind of compound support method for deep foundation pit of tall buildings that neighboring buildings and engineering is provided effective basic guarantee.

The present invention includes following steps: mixing pile construction, leading steel pipe pile construction, soil excavation, side slope construction prestressed cable.

Described mixing pile construction adopts powerful mixing pile machine four to stir four spraying construction technologies, and agitation pile requires to pass through layer of sand and enters the chiltern cohesive soil and be not less than 1000, overlaps 200 mutually.

The steel pipe of described leading steel pipe construction adopts φ 89 * 2.7, drilling diameter φ 110, passes through layer of sand and enters the chiltern cohesive soil and be not less than 1500, and fixed section is not less than 2000; Join slurry with the 32.5R Portland cement, water/binder ratio 0.55~0.6, slip casting from lower to upper behind the clear hole, grouting pressure is 0.5~0.8MPa.

During described soil excavation, agitation pile length of time is greater than 10 days, the layer and section excavation, and every layer of cutting depth and the vertical spacing of anchor pole are complementary, and the degree of depth of backbreaking is less than 0.2m; Supporting one deck immediately behind excavation one deck does not have ponding around the wall, last layer not supporting soil nailing length of time greater than 4 days; Every section excavation length is 15~20m.

Described construction prestressed cable is in proper order: repair side slope, pore-forming, anchor cable installation, clear hole, once grouting, secondary grouting, linked network, injection fine-stone concrete, waist rail construction, prestressed stretch-draw.

The present invention is according to place situation, geological conditions and surrounding enviroment, and the compound support process of employing is reasonable, and after the enforcement, the various distortion of foundation ditch all in control range, have guaranteed construction safety, have also ensured the safety of neighboring buildings.

The specific embodiment:

1. soil nailing, anchor cable design

1.1 soil layer parameter

1) artificial earth fill: the thick miscellaneous fill of about 3.95m.C=10Kpa,Φ=10,γ=18KN/m 3

2) plough soil: the thick loess shape of about 0.82m silty clay.C=10Kpa,Φ=10,γ=18KN/m 3

3) mud matter flour sand: bed thickness 0.70m~3.7m.C=3~5Kpa,Φ=14,γ=17KN/m 3

4) silty clay: bed thickness 1.10m~5.6m.C=20Kpa,Φ=18,γ=18.5KN/m 3

5) coarse sand: bed thickness 0.9m~6.6m.C=3Kpa,Φ=30,γ=19KN/m 3

6) chiltern cohesive soil: bed thickness 7.9~23.50m.C=25Kpa,Φ=23,γ=19KN/m 3

1.2 design parameters

1) the about 8.0m of the excavation of foundation pit degree of depth, east, south, west side side slope are vertical supporting; The north side side slope adopts puts the slope excavation, and the gradient is 1: 0.4, and this side ground level is reduced 3m.

2) leading steel pipe adopts steel pipe to adopt φ 89 * 2.7, drilling diameter φ 110; Soil nailing adopts φ 25, and aperture 110, inclination angle are 15 °; Anchor cable adopts 2*7 Φ 5 steel strand, and drilling diameter is 130, and the inclination angle is 25 ° of free section 5m, and anchoring section is greater than 20m.

3) foundation pit side-wall safe class: the east side is an one-level, and important coefficient is 1.10; Southern side, north side, west side are secondary, and important coefficient is 1.0.

4) must not preloading in the 1m scope outside the foundation ditch sideline, beyond the 1m overload must not above 15kPa in ground.

1.3 result of calculation:

East side 1.3.1 (from the nearer part of building)

1) soil nailing adopts Φ 25 reinforcing bars, and length 12~16m, vertical spacing top are 1.3m, bottom 1.0m; The level interval anchor cable partly is 2.4m, and soil nailing partly is 2.4m.Soil nailing length does not all contain exposed parts, adds 200 (anchor head length) during blanking on the basis of this size.

2) this side adopts leading steel pipe pile, and spacing is 0.8 meter.

3) this side is established two road prestress anchorage cables and is controlled foundation pit deformation: free section 5m, and anchoring section 20m, the design uplift resistance is 280KN, latching force is 200KN.

1.3.2 west side, southern side

1) soil nailing adopts Φ 25 reinforcing bars, length 15~16m.Vertical spacing: top is 1.3~1.5m, and the bottom is 1.3m; Level interval: anchor cable partly is 2.6m, and soil nailing partly is 2.6m.

2) the leading steel pipe pile spacing of this side is 1.0 meters.

3) adopt two road prestress anchorage cables to control foundation pit deformation, free section 5m, anchoring section 20m; The design uplift resistance is 280KN, and latching force is 200KN.

1.3.3 north side

Employing is put the slope in conjunction with plate brad supporting, and the gradient was undertaken by 1: 0.4, and soil nailing adopts Φ 18 reinforcing bars.

1.3.4 jet face arrangement of reinforcement

Distribution bar is φ 8@200 * 200mm, and soil nailing connects with 2 φ, 16 stiffeners in domatic horizontal direction, and reinforcing rib passes anchor head the inside, and welds with anchor head, and weld length is 160.

1.3.5 slip casting, fine-stone concrete are domatic

1) 32.5R cement is adopted in slip casting, and water/binder ratio is 0.5, and pressure is 0.4~0.6Mpa.

2) the domatic C20 concrete of fine-stone concrete proportioning is a cement: sand: stone=1: 1.7: 1.9, and thick 100,32.5R cement.

2. job practices

Overall sequence of construction: mixing pile construction, leading steel pipe pile construction, soil excavation, side slope construction prestressed cable.

2.1 mixing pile construction

Because of this engineering layer of sand is thicker, adopt single agitation pile to be difficult to reach stagnant water effect, so adopted double agitation pile.Deep-mixed pile: adopt powerful mixing pile machine four to stir four spraying construction technologies, agitation pile requires to pass through layer of sand and enters the chiltern cohesive soil and be not less than 1000, overlaps 200 mutually, the following diagram of double agitation pile layout:

Cement mixing pile adopts the 32.5R Portland cement to join slurry, water/binder ratio 0.55~0.6, and every meter pile body cement consumption is 65kg/m.The construction agitator shaft speed is preferably middle-grade, and hoisting velocity is 0.8~1.2m/min, must not be too fast, in order to avoid influence mixing effect.Carry out marker peg and control line by the drawing spacing before the construction, control pile body verticality, effective length, stake top and an end absolute altitude in the work progress well.

2.2 leading steel pipe construction

Steel pipe pile: steel pipe pile mainly is in the soil excavation process, when soil nailing and anchor pole also play the advance support effect during construction (stressed).Steel pipe adopts φ 89 * 2.7, and drilling diameter φ 110 require to pass through layer of sand and enter the chiltern cohesive soil and be not less than 1500, and fixed section is not less than 2000.Join slurry with the 32.5R Portland cement, water/binder ratio 0.55~0.6, slip casting from lower to upper behind the clear hole, grouting pressure is preferably 0.5~0.8MPa.Must emit the agitation pile center line before the construction, deflect away from agitation pile, reduce the steel pipe pile effect to prevent steel pipe pile.

2.3 earth excavation and finishing side slope

Excavation of foundation pit: after agitation pile reaches 10 days the length of time, can carry out the construction of excavation of foundation pit and combined bolting and shotcrete, require the layer and section excavation, every layer of cutting depth should be complementary with the vertical spacing of anchor pole, and the degree of depth of backbreaking must not be greater than 0.2m; Must closely cooperate plate brad supporting construction of soil excavation, strictness accomplishes to excavate one deck, and supporting one deck, last layer be intact or 70% (being that soil nailing must not be less than 4 days the length of time) that do not reach injecting cement paste intensity of supporting not, must not excavate down one deck, every section excavation length is preferably 15~20m.Behind the mechanical equivalent of light excavation, in time cooperate the manual amendment wall, require to reach smooth, the gradient is consistent, the axial location of side slope is wanted accurately, and forbid to draw behind the retaining wall and dig, and must not ponding around the wall of limit.

When soil nailing spray anchor was partly constructed, top sprayed mortar and soil nailing length of time can be excavated down one deck greater than 4 days; Prestress anchorage cable anchoring body intensity and waist rail intensity reach 70%, can tensioning fixation.

2.4 anchor cable construction

2.4.1 pore-forming requires and deviation

According to design pitch and absolute altitude, make the position, hole, make mark.Soil nailing horizontal direction pitch-row deviation must not be greater than 50mm, vertical direction pitch-row deviation must not be greater than 100mm, and the deflection size of foot of hole must not be greater than 3% of bar length, and hole depth must not be less than design length, also must not be greater than 1% of design, the soil nailing inclination angle will adhere to specification.

2.4.2 soil nailing is made and is laid

1) the soil nailing reinforcing bar should be straight, oil removing, rust cleaning.

2) mechanical connection is adopted in bar splice.

3) soil nailing is along axis direction, every 2m adopts Φ 10 reinforcing bars to do that (anchor cable adopts Φ 48*3.5 steel pipe to be cut into 100 long segments to medium-height trestle to medium-height trestle, at three Φ 10 of tube wall equal intervals weldering, shape is with centralizer shape on the soil nailing, and with centralizer with iron wire with the steel strand colligation on the pipe face) to guarantee that the body of rod (anchor cable) is in hole central authorities.

When 4) laying the body of rod (anchor cable), should prevent the distortion of the body of rod.Grouting Pipe is together put into the body of rod.Grouting Pipe is preferably 50~100mm at the bottom of the hole.

5) degree of depth of body of rod patchhole must not be less than 95% of the body of rod.After the body of rod is put into, must not arbitrarily knock.

6) common soil nailing external end head welds 2 Φ, 25 reinforcing bars, and the every long 60mm of reinforcing bar is to strengthen uplift resistance and fixing steel mesh reinforcement.

2.4.3 clear hole, slip casting

1) after hole forming is installed soil nailing, carries out hole clearly with press water immediately, carry out slip casting after returning out clear water to the aperture.

2) Grouting Pipe adopts the PVC plastic pipe, and Grouting Pipe should be delivered at the bottom of the hole, delivers to bottom, slip casting from lower to upper to guarantee slurries.

3) when clear hole is limpid to backwater, change the cement paste (water/binder ratio is 0.45) that notes prepare in advance immediately.Begin slip casting at the bottom of the Ying Congkong until the excessive slurry in aperture, and assert when being full of cement paste in the hole, Grouting Pipe is pulled out outward to distance aperture 500, stop and mended slurry in 10~15 minutes again.

4) to prestress anchorage cable secondary grouting pipe, pipe bottom is about 500 at the bottom of the hole, and seal with adhesive plaster at the pipe end, and Grouting Pipe begins to open Φ 8 apertures and seal with adhesive plaster every 1m from pipe end 500, prevents in the once grouting cement paste inflow pipe.

5) the prestress anchorage cable secondary grouting only carries out anchoring section, after treating once grouting 4~6 hours (after the cement mortar initial set) carry out, the control grouting pressure is 1.5~2.0Mpa, make slurries break through the body that is in the milk for the first time, splitting diffusion between anchoring body and soil, make it enlarged-diameter, increase radial load, to improve the resistance to plucking ability.

2.5 linked network, injection rapid hardening concrete surface layer

1) outer net is connected with bar and wants firmly, and steel mesh reinforcement adopts Φ 8@200 two-way concrete slab, adopts the colligation overlap joint, lap length>300mm, joint will stagger, longitudinal reinforcement insert in the soil length should>300mm.

2) after net hangs up properly, reinforcing rib is installed, the good reinforcement cover of colligation, the concrete surface layer is sprayed in qualified by inspection back.

3) the concrete surface thickness is 100mm, should carry out test preparation before the construction, determines match ratio; Answer mix even when dry mix, and mix accelerating admixture 10%, the wind pressure of work at ejecting gun head place remains on 0.3MPa; Shower nozzle should keep vertical with being subjected to spray plane as far as possible, reduces resilience and concrete trickling phenomenon, and Φ 50 drain caverns of interval 2000 * 2000 quincunx indwellings on surface layer are to mediate domatic water and pressure thereof.

2.6 the stretch-draw of prestress anchorage cable and locking

1) should carry out from the centre to the both sides symmetry during stretch-draw in batches, to reduce because the stress loss that causes when malformation and adjacent anchor cable construction.

2) anchorage cable stretching carries out with regard to classification, is respectively design load 50%, 75%, 100%, and every grade of anchor cable was held lotus about 3~5 minutes, and surveys and to read the anchor head displacement three times, performs the stretch-draw record, and off-load is after design control then, and voltage stabilizing locked after 10 minutes.

3) after the anchor cable locking, should do antirust processing at the anchor head place.

After taking this scheme construction, hole wall top measured displacements and sedimentation all are controlled in the allowed band:

Sedimentation alarming value in east side is 26mm, actual sedimentation 14.73mm; The horizontal movement alarming value is 35mm, actual displacement 25mm; Remainder, sedimentation alarming value are 40mm, and actual sedimentation maximum value is 7.2mm; The horizontal movement alarming value is 35mm, and actual maximum value is 9mm.House, the road of periphery and other building all do not deform, the phenomenon of crack and sedimentation shows that the present invention is practicable technical scheme.

Claims (5)

1, a kind of compound support method for deep foundation pit of tall buildings is characterized in that may further comprise the steps: mixing pile construction, leading steel pipe pile construction, soil excavation, side slope construction prestressed cable.
2, according to the described compound support method for deep foundation pit of tall buildings of claim 1, it is characterized in that described mixing pile construction adopts powerful mixing pile machine four to stir four spraying construction technologies, agitation pile requires to pass through layer of sand and enters the chiltern cohesive soil and be not less than 1000, overlaps 200 mutually.
3, according to the described compound support method for deep foundation pit of tall buildings of claim 1, it is characterized in that the steel pipe of leading steel pipe construction adopts φ 89 * 2.7, drilling diameter φ 110, pass through layer of sand and enter the chiltern cohesive soil and be not less than 1500, fixed section is not less than 2000; Join slurry with the 32.5R Portland cement, water/binder ratio 0.55~0.6, slip casting from lower to upper behind the clear hole, grouting pressure is 0.5~0.8MPa.
4, according to the described compound support method for deep foundation pit of tall buildings of claim 1, when it is characterized in that soil excavation, agitation pile length of time is greater than 10 days, the layer and section excavation, and every layer of cutting depth and the vertical spacing of anchor pole are complementary, and the degree of depth of backbreaking is less than 0.2m; Supporting one deck immediately behind excavation one deck does not have ponding around the wall, last layer not supporting soil nailing length of time greater than 4 days; Every section excavation length is 15~20m.
5, according to the described compound support method for deep foundation pit of tall buildings of claim 1, it is characterized in that construction prestressed cable is in proper order: repair side slope, pore-forming, anchor cable installation, clear hole, once grouting, secondary grouting, linked network, injection fine-stone concrete, waist rail construction, prestressed stretch-draw.
CNA2008100243690A 2008-06-06 2008-06-06 Compound support method for deep foundation pit of tall buildings CN101285309A (en)

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102031784A (en) * 2011-01-12 2011-04-27 陕西建工集团第六建筑工程有限公司 Slope protection pile pouring and cable bolting construction method for deep foundation pit
CN102286979A (en) * 2011-05-26 2011-12-21 昆明二建建设(集团)有限公司 Construction method for deep foundation pit supporting by adopting steel pipe piles-self-drilling prestressed anchor bars
CN102425172A (en) * 2011-12-05 2012-04-25 中冶天工集团有限公司 Support method for excavating deep foundation pit closely adjacent to high-rise building
CN103147443A (en) * 2013-03-18 2013-06-12 中国建筑第八工程局有限公司 Foundation pit supporting structure and construction method thereof
CN103243721A (en) * 2013-05-22 2013-08-14 中国建筑第八工程局有限公司 Raft foundation and core tube excavation construction method of high-rise building under weak geological conditions
CN103255771A (en) * 2013-05-24 2013-08-21 山西太行建设开发有限公司 Method for excavating super-deep foundation pit engineering piles in graded mode and graded composite supporting of supporting piles
CN103572701A (en) * 2013-10-08 2014-02-12 中铁十八局集团有限公司 Buckling anchor system combined rock anchor
CN103993604A (en) * 2014-06-05 2014-08-20 中国建筑材料工业地质勘查中心广东总队 Scattered piled anchor foundation pit supporting structure
CN105586976A (en) * 2015-12-24 2016-05-18 上海核工程研究设计院 Method for carrying out foundation pit slope support by virtue of slope-ratio method as well as mixing piles and pre-stressed anchor cables
CN108797600A (en) * 2018-05-21 2018-11-13 青岛建集团有限公司 Miniature steel pipe pile prestressed anchor rope combination supporting construction method
CN109208617A (en) * 2018-10-25 2019-01-15 长沙理工大学 A kind of red beds rock side slope flexible comprehensive supporting construction and its construction method

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102031784A (en) * 2011-01-12 2011-04-27 陕西建工集团第六建筑工程有限公司 Slope protection pile pouring and cable bolting construction method for deep foundation pit
CN102286979A (en) * 2011-05-26 2011-12-21 昆明二建建设(集团)有限公司 Construction method for deep foundation pit supporting by adopting steel pipe piles-self-drilling prestressed anchor bars
CN102425172B (en) * 2011-12-05 2013-12-11 中冶天工集团有限公司 Support method for excavating deep foundation pit closely adjacent to high-rise building
CN102425172A (en) * 2011-12-05 2012-04-25 中冶天工集团有限公司 Support method for excavating deep foundation pit closely adjacent to high-rise building
CN103147443A (en) * 2013-03-18 2013-06-12 中国建筑第八工程局有限公司 Foundation pit supporting structure and construction method thereof
CN103147443B (en) * 2013-03-18 2015-08-05 中国建筑第八工程局有限公司 Foundation pit supporting construction and construction method thereof
CN103243721A (en) * 2013-05-22 2013-08-14 中国建筑第八工程局有限公司 Raft foundation and core tube excavation construction method of high-rise building under weak geological conditions
CN103243721B (en) * 2013-05-22 2016-02-17 中国建筑第八工程局有限公司 Highrise Building With Raft Foundation and Core Walls Structure excavation construction method under Unfavorable geology condition
CN103255771A (en) * 2013-05-24 2013-08-21 山西太行建设开发有限公司 Method for excavating super-deep foundation pit engineering piles in graded mode and graded composite supporting of supporting piles
CN103572701A (en) * 2013-10-08 2014-02-12 中铁十八局集团有限公司 Buckling anchor system combined rock anchor
CN103993604A (en) * 2014-06-05 2014-08-20 中国建筑材料工业地质勘查中心广东总队 Scattered piled anchor foundation pit supporting structure
CN105586976A (en) * 2015-12-24 2016-05-18 上海核工程研究设计院 Method for carrying out foundation pit slope support by virtue of slope-ratio method as well as mixing piles and pre-stressed anchor cables
CN108797600A (en) * 2018-05-21 2018-11-13 青岛建集团有限公司 Miniature steel pipe pile prestressed anchor rope combination supporting construction method
CN109208617A (en) * 2018-10-25 2019-01-15 长沙理工大学 A kind of red beds rock side slope flexible comprehensive supporting construction and its construction method

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