CN102535477B - Safety construction method for cutting off anchor cables of support of excavating foundation pit - Google Patents
Safety construction method for cutting off anchor cables of support of excavating foundation pit Download PDFInfo
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Abstract
The invention discloses a safety construction method for cutting off anchor cables of a support of an excavating foundation pit, which includes steps of firstly measuring various physical and mechanic parameters of the soil and constructing a row of cast-in-situ bored piles beside a fender pile of an excavated foundation pit; constructing manually-hole-drilled piles; determining position and size of an anchored ring beam of each layer of anchor cables and constructing ring beams with top surrounded by purlins; excavating a new foundation pit; fixing anchorage devices to one ends of the anchor cables penetrating out of the ring beam and distant from the manually-hole-drilled piles, casting a second ring beam, excavating continuously after the second ring beam reaches the designed strength, and excavating out the first anchor cable; cutting off the first anchor cable, recovering the first cut-off anchor cable and the anchorage device thereof and completing excavation of the first anchor cable; excavating from the lateral side of the new foundation pit to the position of the second anchor cable, then casting the second ring beam, and repeating the above steps until the last anchor cable is excavated out. Construction safety of foundation pit excavation can be effectively guaranteed, the anchor cables and clamps can be recycled and project manufacturing cost is reduced.
Description
Technical field
What the present invention relates to is the construction technology in a kind of underground structrue engineering technical field, the safe construction method that specifically a kind of pattern foundation pit supporting structure anchor cable excavating cuts off.
Background technology
In deep pit construction, adopt the support of prestress anchorage cable as Retaining Structures, there is the foundation ditch inner space of saving, guarantee to excavate the scope of operation, excavation construction efficiency high, save the advantages such as support expense.Therefore from last century the nineties from the beginning of, in China's urban architecture deep foundation ditch, be widely used.In the metropolis such as Guangzhou, Beijing, Wuhan, there are into kiloton steel every year and are embedded in underground by pattern foundation pit supporting structure anchor cable.In the time carrying out new foundation ditch or other underground engineering construction on foundation ditch limit, the anchor cable of existing foundation ditch need to be dug out or cuts off.At this moment in order to ensure the safety of the foundation ditch in excavation construction just, the anchor cable that is arranged in construction foundation ditch need to be cut off and dig out, and in corresponding hand excavated pile position again anchoring support anchor cable.
By existing technical literature retrieval is found, although existing a large amount of patent documentation about foundation ditch Recyclable anchor rope, as Chinese invention patent application numbers 200410027469.0, denomination of invention: the Recyclable anchor rope of civil engineering, and application for a patent for invention 200910197095.X, denomination of invention: recyclable prestressed tendon for soft oil support and construction method thereof, also have application for a patent for invention numbers 201020138405.9, denomination of invention: the recoverable prestressed anchor cable of U-shaped anchor head in addition.But the content of these patents concentrates on while installation before excavation of foundation pit how anchoring mostly, and how pit backfill to reclaim after finishing, and do not cut off technological means and the scheme of digging out then anchoring for the anchor cable of foundation ditch in construction.For the deep foundation ditch that carries out excavation construction, its supporting anchorage cable is dug out or cut off is danger close.Therefore, need anchoring again to guarantee construction safety.
Summary of the invention
Object of the present invention is just for above-mentioned defect, provide a kind of existing foundation ditch anchor cable is dug out after the construction method of anchoring again, how what overcome that above-mentioned technical background lacks deals carefully with in the foundation ditch excavating anchor cable to guarantee the technological means of security of foundation ditch construction and the problem of scheme.
The present invention is achieved by the following technical solutions, comprises the steps:
The first step, on-the-spot hydrogeology exploration, the boring of fetching earth, divides soil layer, determines top board and the bottom plate depth of each soil layer within the scope of Effects on Engineering, descends definitely water distribution.Get the sample of natural undisturbed soil simultaneously, measure every physical and mechanical parameter of the soil body by laboratory test.
Described every physical and mechanical parameter of measuring the soil body by laboratory test, is organized into soil test outcome table.Parameter comprises: the compression modulus Es of each layer soil body, void ratio e, natural density γ, poisson's ratio μ, cohesion c, angle of friction
Described on-the-spot boring extracting soil, mainly adopt thin-wall sampler at the construction field (site) from ground to stake projected depth fetch earth, the amount of fetching earth according to test specimen amount determine, be no less than three test specimens with every layer of soil and be advisable.
Described laboratory test comprises: Axial compression tests, density test, shear test, triaxial test.
Described Axial compression tests refers to: the compression modulus Es that records each soil layer by indoor Axial compression tests instrument.
Described density test refers to: record the wet density ρ of each soil layer by core cutter method isodensity test method, and calculate corresponding natural density γ; Measure each soil layer soil moisture content w and the rear soil particle dry weight m of unit soil oven dry by oven drying method
s, then in conjunction with the density p of wet density ρ and water
wcan try to achieve void ratio:
Described shearing experiment refers to: the cohesion c that determines the soil body by unconsolidated undrained test.
Described triaxial test refers to: the Stationary side pressure coefficient K that measures the soil body by triaxial apparatus
0, then according to poisson's ratio μ and Stationary side pressure coefficient K
0relation:
Calculate poisson's ratio μ; Make the mohr circle of stress of soil under different confined pressures by triaxial test, obtain native angle of friction
Second step, construction drill castinplace pile: the row hole drilling castinplace pile of constructing on the fender post side of built good foundation ditch.When pile driving construction, should note avoiding anchor cable position, size, spacing and the stake of stake are dark in Finite Element Method calculative determination.
Described Finite Element Method is, according to the every Soil Parameters in laboratory soil test table, and suppose in advance bored pile size, spacing and stake is dark, then utilize finite element software simulating excavation, thereby calculate the safe bored pile size of excavation, spacing and a kind of dark method of stake of meeting.Concrete steps are as follows:
1. Geometric Modeling, according to design drawing, carries out Geometric Modeling by the soil body in the certain limit including existing foundation ditch and newly-built foundation ditch.
Determining of soil body scope value:
A. determining of horizontal extent: two edge directions that horizontal direction is got respectively foundation ditch are X, Y-direction, and model soil body horizontal extent is got including two foundation ditches and from foundation ditch edge the scope along X, the outside twice foundation ditch of Y-direction length respectively.
B. determining of depth bounds: getting higher foundation ditch surface for soil body end face, is soil body bottom surface compared with downward 1.5 times of its foundation depths at the bottom of Deep Foundation Pit.
2. Soil Parameters value, according to the laboratory test parameter value in step 1.Value parameter comprises the compression modulus Es of each layer soil body, void ratio e, natural density γ, poisson's ratio μ, cohesion c, angle of friction
Size, spacing and a dark and distribution of 3. supposing a kind of bored pile, the general cut-off of size footpath is within the scope of 600～1800mm; More than spacing is generally got 300mm; Stake is dark generally gets 1.5 times of foundation depths, in the time that soil layer under foundation ditch has ground stabilization measure or holds power rock stratum etc., gets back-up coat or the power rock stratum of holding above; Arrange and should note avoiding anchor cable position when distribution form, bored pile external diameter should be from more than one times of stake footpath of anchor cable conventionally, anchor cable is exerted an influence when preventing drilling construction.
4. 3. middle castinplace pile parameter of basis, utilizes the excavation of the newly-built foundation ditch of finite element software analog computation in this kind of situation, if meet the requirement of excavation degree of safety, stops calculating; If do not meet the requirement of excavation degree of safety, again suppose castinplace pile parameter, conventionally add timber pile footpath or reduce spacing, then continue analog computation, until degree of safety meets.Now can draw the bored pile parameter that meets excavation degree of safety.
The 3rd step, construction hand excavated pile, when bored pile reaches after design strength, selection ground tackle, and planning to build foundation ditch and building line-up's work hole digging pile of constructing between the fender post of foundation ditch, determine hand excavated pile plan-position and parameter.
Described hand excavated pile plan-position is determined by the following method: get the vertical line of the both sides fender post line of centres and the center that anchor cable joining is hand excavated pile.
Described hand excavated pile parameter refers to: hand excavated pile stake footpath and stake are dark.Specifically value by the following method:
Diameter is value in 800～1200mm, when value guarantee stake with between more than interval 300mm; Stake is dark gets 1.2 times of higher values of planning to build between the design of foundation pit degree of depth and 1.2 times of last one deck anchor cable buried depths, in the time that soil layer under foundation ditch has ground stabilization measure or holds power rock stratum etc., gets back-up coat or the power rock stratum of holding above.
Hand excavated pile Specific construction step is as follows:
1. carry out soil excavation until first floor anchor cable is exposed at 20cm place under first floor anchor cable.When digging to should reduce speed of application in the time that first floor anchor cable also has 35mm, the too fast disconnected anchor cable that digs of avoiding constructing.
2. ground tackle be clipped in to first floor anchor cable middle part and fix.
3. repeat the 1.～2. step, until dig to stake projected depth, and all ground tackles are fixed.
4. lift reinforcing cage, after rigging out, withdraw from constructor and construction apparatus, carry out concrete pouring construction, complete manual digging pile construction.
The 4th step, determines position and the size of every layer of anchorage cable anchoring collar tie beam, and purlin collar tie beam is enclosed at construction top.
Described anchoring collar tie beam refers to: on the bored pile of planning to build foundation ditch side, build collar tie beam, the end anchorage end after cutting off as anchor cable.Wherein, enclose purlin collar tie beam planning to build construction top, foundation ditch sidetracking hole pouring pile top, to improve the globality of bored pile.Anchor cable adopts the anchoring of intumescent crab-bolt.
Described anchoring collar tie beam position refers to: planning to build the position at foundation ditch sidetracking hole pouring pile place as the position at the anchoring collar tie beam center of this layer of anchor cable using every layer of anchor cable.Wherein, the position that purlin collar tie beam is enclosed at top is for planning to build foundation ditch sidetracking hole pouring pile upper end place.
The size of described anchoring collar tie beam refers to: the deck-siding of every layer of anchorage cable anchoring collar tie beam and deck-molding, specifically determine according to the following steps:
1. determine effective anchorage depth of anchor cable.
Effective anchorage depth of described anchor cable meets following formula:
h
ef＝5d
Wherein, h
effor effective anchorage depth of anchor cable; D is the maximum gauge of single anchor cable, according to building the anchorage cable design scheme value of foundation ditch.
2. determine deck-molding and the deck-siding of anchorage cable anchoring collar tie beam.
The deck-molding of described anchoring collar tie beam is by meeting following formula:
h＝1.5h
ef
Wherein, h is the deck-molding of anchoring collar tie beam.
The deck-siding of described anchoring collar tie beam meets following formula:
b＝1.2h
ef
Wherein, b is the deck-siding of anchoring collar tie beam.
For guaranteeing that top encloses the effect of purlin collar tie beam performance globality, top is enclosed purlin collar tie beam and is got its size of conduct maximum in all the other collar tie beam sizes.
Described construction top is enclosed purlin collar tie beam and is referred to: hit concrete at the top of newly-built bracing of foundation pit stake and existing bracing of foundation pit stake cutter respectively, expose reinforcing bar in concrete.The reinforcing cage that encloses purlin collar tie beam is fixedly welded on to stake top and cuts a hole on the reinforcing bar hitting, and fix anchor cable, linkage.
The 5th step, new pit earthwork excavation.The construction method of soil excavation is: vertical layered, and longitudinally piecemeal.On vertical according to steel supported design position up and down a point multilayer excavate, layering absolute altitude is that every layer of steel supports lower 0.5～0.8m.
New foundation ditch side first floor soil excavation: carry out according to pit earthwork excavation plan.When cutting depth is to the 5cm place, bottom of the second collar tie beam of fixing anchor cable, expose first anchor cable.
The 6th step, is fixed on anchor cable by ground tackle and passes collar tie beam the one end away from hand excavated pile, is second collar tie beam formwork, cast second collar tie beam, and maintenance two weeks continues excavation after collar tie beam reaches design strength, digs out first anchor cable.
The 7th step, cuts off first anchor cable, reclaims the anchor cable cutting off and reclaims ground tackle.First anchor cable digs out end.
The 8th step, new foundation ditch side continues to be excavated to second anchor cable position, and rear cast second collar tie beam, repeats above-mentioned five～seven steps, and second anchor cable digs out end.
The 9th step, repeating step five is to step 8, and to the last one anchor cable digs out and stops.
The tenth step, construction finishes, base plate of foundation pit and internal construction backfill.
Compared with prior art, anchor cable in the foundation ditch in excavation construction is cut off the construction method that reclaims and be again anchored in foundation ditch side hand excavated pile position by the present invention, can effectively guarantee the construction safety of excavation pit, and reclaim anchor cable and fixture to recycle, be a kind of economic and engineering method efficiently.
Accompanying drawing explanation
Fig. 1 is application anchor cable plane of arrangement figure of the present invention;
Fig. 2 is application anchor cable layout of the present invention skiagraph;
Fig. 3 is the rear skiagraph of application anchor cable cut-out of the present invention.
The specific embodiment
Below embodiments of the invention are elaborated, the present embodiment is implemented under take technical solution of the present invention as prerequisite, provided detailed embodiment and concrete operating process, but the scope of application of the present invention is not limited to following embodiment.
The projected depth of embodiment Certain Project excavation pit is 14m, intends adopting bored pile space enclosing structure.Plan to build foundation ditch one side 8.5m place and building the fender post of foundation ditch for another, building design of foundation pit degree of depth 10m, it adopts piled anchor structural support near planning to build foundation ditch one side, anchor cable arranges 3 roads, level interval 1.5m, vertical spacing is 3.0m, 3.0m, 3.0m, and anchor cable length 15m, stretches into and plan to build 6m within the scope of foundation ditch.Two foundation ditch layout are rectangle, are building the long 180m of foundation ditch, and wide 157m, plans to build the long 66m of foundation ditch, wide 25m, and the adjacent edge length that influences each other is 50m.Intend adopting by the safe construction method of the supporting anchor tractotomy in excavation pit just, in the present embodiment, there is no the part describing in detail, the technical scheme of describing according to summary of the invention operates, and the part also not illustrating in summary of the invention adopts ability city routine operation to carry out.
The present embodiment Specific construction step is summarized as follows:
The first step, carries out soil layer division by on-the-spot boring extracting soil to planning to build excavation of foundation pit region, obtains job site soil sample simultaneously and carries out indoor conventional soil test, obtains hierarchical information and the physical and mechanical parameter of soil layer.Concrete hierarchical information and each soil layer physical and mechanical parameter are as follows: ground to the soil body within the scope of underground 24m is divided into 5 layers: first floor is plain fill, the compression modulus Es=3.40MPa of soil layer, void ratio e=0.80, natural density γ=17.934kN/m
3, poisson's ratio v=0.3, cohesion C=20kPa, angle of friction φ=15 °, floor level is-1.2m, bed thickness 1.2m; The second layer is silty clay, the compression modulus Es=4.60MPa of soil layer, void ratio e=0.87, natural density γ=18.228kN/m
3, poisson's ratio v=0.32, cohesion C=20kPa, angle of friction φ=15 °, floor level is-3.3m, bed thickness 2.1m; The 3rd layer is loam, the compression modulus Es=3.76MPa of soil layer, void ratio e=0.93, natural density γ=17.542kN/m
3, poisson's ratio v=0.29, cohesion C=19kPa, angle of friction φ=20 °, floor level is-10m, bed thickness 6.7m; The 4th layer is completely decomposed granite, the compression modulus Es=4.38MPa of soil layer, void ratio e=0.75, natural density γ=18.228kN/m
3, poisson's ratio v=0.26, cohesion C=22kPa, angle of friction φ=24 °, floor level is-17.6m, bed thickness 7.6m; Layer 5 is strong weathered granite, the compression modulus Es=4.38MPa of soil layer, void ratio e=0.70, natural density γ=18.424kN/m
3, poisson's ratio v=0.25, cohesion C=22kPa, angle of friction φ=25 °, floor level is-24m, bed thickness 6.4m.
Second step, at fender post and the middle construction one row hole drilling castinplace pile of planning to build bracing of foundation pit stake of built good foundation ditch.
Concrete steps are as follows:
1. according to design drawing, determine modeling scope, then carry out Geometric Modeling.Soil body modeling scope is: length × wide × height=410m × 346m × 21m.
2. determine Soil Parameters.The parameter value obtaining according to laboratory test in the first step.
3. determine by FEM (finite element) calculation, in this example, drilled pile diameter is 1.2m, between stake and stake, is spaced apart 300mm, and the degree of depth is 21m, and the distribution of stake as shown in Figure 1.
The 3rd step, construction hand excavated pile.
Investigation build foundation ditch anchorage cable design scheme determine anchor cable distribute, determine hand excavated pile stake footpath, stake dark and spacing.In this example, 1000mm is got in hand excavated pile stake footpath, the dark 16.8m that gets of stake, and spacing is 1500mm.After hand excavated pile has excavated, on anchor cable, ground tackle is fixed, lifting reinforcing cage, withdraws from constructor and construction apparatus after rigging out, carry out concrete pouring construction, completes manual digging pile construction.
The 4th step, determines position and the size of every layer of anchorage cable anchoring collar tie beam, and purlin collar tie beam is enclosed at construction top.
1. determine effective anchorage depth of anchor cable.This example has 3 road anchor cables, and the maximum gauge of single anchor cable is 80mm, and effective anchorage depth of anchor cable is 400mm.
2. determine deck-molding and the deck-siding of anchorage cable anchoring collar tie beam.This example need to be built 4 road collar tie beams (containing enclosing purlin collar tie beam in top).Collar tie beam is of a size of 600mm × 480mm.Adopt the M15-N ground tackle that steel strand specification is 15.24, anchoring process is that one end is fixed on each layer of collar tie beam of excavation pit fender post, and the other end is embedded in the Adjacent Pit soil body.Two ends anchor head adopts round platform build fixture.Fig. 2 is that the anchor cable of application is arranged skiagraph.
Purlin collar tie beam is enclosed at construction top: hit concrete at the top of newly-built bracing of foundation pit stake and existing bracing of foundation pit stake cutter respectively, expose reinforcing bar in concrete.The reinforcing cage that encloses purlin collar tie beam is fixedly welded on to stake top and cuts a hole on the reinforcing bar hitting, and fix anchor cable and linkage.Then formwork cast collar tie beam, in this example according to by both sides to middle order, be divided into up and down three layers and pour into a mould.
The 5th step, excavates the earthwork of new foundation ditch side first floor.Cutting depth is to 5.35m,, expose first anchor cable.
The 6th step, fixes anchor cable two ends with fixture, be second collar tie beam formwork, cast second collar tie beam, and maintenance continues excavation after two weeks, dig out first anchor cable.Fig. 3 is skiagraph after the anchor cable of application cuts off.
The 7th step, cuts off first anchor cable, reclaims the anchor cable cutting off and reclaims ground tackle, and first anchor cable digs out end.The ground tackle major part of digging out meets the instructions for use in engineering, in this example, it is recycled, to save engineering cost.
The 8th step, new foundation ditch side second layer soil excavation.Continue soil excavation, cutting depth, to 8.35m place, is now exposed second anchor cable.Repeat above-mentioned six～seven steps, second anchor cable digs out end.
The 9th step, repeats five～seven steps, and now cutting depth is 11.35m, until last one anchor cable (this example Wei tri-roads) digs out.Anchor cable construction finishes.
The tenth step, cleaning foundation ditch bottom, carries out backfill construction to base plate of foundation pit and internal construction.This case history adopts sandy clay, back-filling in layers and compacting.After backfill finishes, complete construction.
Anchoring again after the present embodiment digs out existing foundation ditch anchor cable, overcome and how to deal carefully with the interior anchor cable of the foundation ditch excavating to guarantee the problem of security of foundation ditch construction, can effectively guarantee the construction safety of excavation pit, and reclaim anchor cable and fixture to recycle, reduce construction costs.
Although content of the present invention has been done detailed introduction by above preferred embodiment, will be appreciated that above-mentioned description should not be considered to limitation of the present invention.Read after foregoing those skilled in the art, for multiple modification of the present invention and substitute will be all apparent.Therefore, protection scope of the present invention should be limited to the appended claims.
Claims (9)
1. the safe construction method that excavation pit supporting anchorage cable cuts off, is characterized in that comprising the steps:
The first step, on-the-spot hydrogeology exploration, the boring of fetching earth, divide soil layer, determine top board and the bottom plate depth of each soil layer within the scope of Effects on Engineering, descend definitely water distribution, get the sample of natural undisturbed soil simultaneously, measure every physical and mechanical parameter of the soil body by laboratory test;
Second step, construction drill castinplace pile: the row hole drilling castinplace pile of constructing on the fender post side of built good foundation ditch, when pile driving construction, avoid anchor cable position, size, spacing and the dark calculation of parameter obtaining by Finite Element Method and according to the first step of stake of stake are determined;
The 3rd step, construction hand excavated pile, when bored pile reaches after design strength, selection ground tackle, and planning to build foundation ditch and building line-up's work hole digging pile of constructing between the fender post of foundation ditch, determine hand excavated pile plan-position and parameter;
In the 3rd step, hand excavated pile Specific construction step is as follows:
1. carry out soil excavation until first floor anchor cable is exposed at 20cm place under first floor anchor cable, when digging to reduce speed of application in the time that first floor anchor cable also has 35mm, the too fast disconnected anchor cable that digs of avoiding constructing;
2. ground tackle be clipped in to first floor anchor cable middle part and fix;
3. repeat the 1.～2. step, until dig to stake projected depth, and all ground tackles are fixed;
4. lift reinforcing cage, after rigging out, withdraw from constructor and construction apparatus, carry out concrete pouring construction, complete manual digging pile construction;
The 4th step, determines position and the size of every layer of anchorage cable anchoring collar tie beam, and purlin collar tie beam is enclosed at construction top;
The 5th step, new pit earthwork excavation, the construction method of soil excavation is: vertical layered, longitudinally piecemeal; On vertical according to steel supported design position up and down a point multilayer excavate;
The 6th step, is fixed on anchor cable by ground tackle and passes collar tie beam the one end away from hand excavated pile, is second collar tie beam formwork, cast second collar tie beam, and maintenance two weeks continues excavation after collar tie beam reaches design strength, digs out first anchor cable;
The 7th step, cuts off first anchor cable, reclaims the anchor cable cutting off and reclaims ground tackle, and first anchor cable digs out end;
The 8th step, new foundation ditch side continues to be excavated to second anchor cable position, and rear cast second collar tie beam, repeats above-mentioned five～seven steps, and second anchor cable digs out end;
The 9th step, repeating step five is to step 8, and to the last one anchor cable digs out and stops;
The tenth step, construction finishes, base plate of foundation pit and internal construction backfill.
2. the safe construction method just cutting off at excavation pit supporting anchorage cable according to claim 1, it is characterized in that: in second step, described Finite Element Method is, according to the every Soil Parameters in laboratory soil test table, and suppose in advance bored pile size, spacing and stake is dark, then utilize finite element software simulating excavation, thereby calculate the safe bored pile size of excavation, spacing and a kind of dark method of stake of meeting.
3. the safe construction method just cutting off at excavation pit supporting anchorage cable according to claim 1, it is characterized in that: in the 3rd step, described hand excavated pile plan-position is determined by the following method: get the vertical line of the both sides fender post line of centres and the center that anchor cable joining is hand excavated pile.
4. according to the safe construction method just cutting off at excavation pit supporting anchorage cable described in claim 1 or 3, it is characterized in that: in the 3rd step, described hand excavated pile parameter refer to hand excavated pile stake footpath and stake dark, specifically value by the following method:
Diameter is value in 800～1200mm, when value guarantee stake with between more than interval 300mm; Stake is dark gets 1.2 times of higher values of planning to build between the design of foundation pit degree of depth and 1.2 times of last one deck anchor cable buried depths, in the time that soil layer under foundation ditch has ground stabilization measure or holds power rock stratum, more than getting back-up coat or holding power rock stratum.
5. the safe construction method just cutting off at excavation pit supporting anchorage cable according to claim 1, it is characterized in that: in the 4th step, described anchoring collar tie beam refers to: on the bored pile of planning to build foundation ditch side, build collar tie beam, end anchorage end after cutting off as anchor cable, wherein, enclose purlin collar tie beam planning to build construction top, foundation ditch sidetracking hole pouring pile top, to improve the globality of bored pile, anchor cable adopts the anchoring of intumescent crab-bolt.
6. the safe construction method just cutting off at excavation pit supporting anchorage cable according to claim 1 or 5, it is characterized in that: described construction top is enclosed purlin collar tie beam and referred to: hit concrete at the top of newly-built bracing of foundation pit stake and existing bracing of foundation pit stake cutter respectively, expose reinforcing bar in concrete, the reinforcing cage that encloses purlin collar tie beam is fixedly welded on to stake top and cuts a hole on the reinforcing bar hitting, and fix anchor cable, linkage.
7. the safe construction method just cutting off at excavation pit supporting anchorage cable according to claim 1 or 5, it is characterized in that: in the 4th step, described anchoring collar tie beam position refers to: planning to build the position at foundation ditch sidetracking hole pouring pile place as the position at the anchoring collar tie beam center of this layer of anchor cable using every layer of anchor cable, wherein, the position that purlin collar tie beam is enclosed at top is for planning to build foundation ditch sidetracking hole pouring pile upper end place.
8. the safe construction method just cutting off at excavation pit supporting anchorage cable according to claim 1 or 5, is characterized in that: in the 4th step, the size of described anchoring collar tie beam refers to: the deck-siding of every layer of anchorage cable anchoring collar tie beam and deck-molding, specifically determine according to the following steps:
1. determine effective anchorage depth of anchor cable
Effective anchorage depth of described anchor cable meets following formula:
h
ef=5d
Wherein, h
effor effective anchorage depth of anchor cable; D is the maximum gauge of single anchor cable, according to building the anchorage cable design scheme value of foundation ditch;
2. determine deck-molding and the deck-siding of anchorage cable anchoring collar tie beam
The deck-molding of described anchoring collar tie beam is by meeting following formula:
h=1.5h
ef
Wherein, h is the deck-molding of anchoring collar tie beam;
The deck-siding of described anchoring collar tie beam meets following formula:
b=1.2h
ef
Wherein, b is the deck-siding of anchoring collar tie beam; Top is enclosed purlin collar tie beam and is got its size of conduct maximum in all the other collar tie beam sizes.
9. the safe construction method just cutting off at excavation pit supporting anchorage cable according to claim 1, it is characterized in that: in the 5th step, described new foundation ditch side first floor soil excavation carries out according to pit earthwork excavation plan, when cutting depth is to the 5cm place, bottom of the second collar tie beam of fixing anchor cable, expose first anchor cable; Described layering absolute altitude is that every layer of steel supports lower 0.5～0.8m.
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| CN103967015B (en) * | 2014-05-21 | 2016-04-27 | 刘绍国 | A kind of water seal for deep foundation pit excavation method and structure thereof |
| CN106088099B (en) * | 2016-07-15 | 2018-08-31 | 中铁隧道集团三处有限公司 | A kind of subway foundation pit anchor cable processing method |
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