CN101481910A - Construction method of foundation pit slope supported independent pile tower crane foundation - Google Patents

Abstract

The invention discloses a method for constructing an independent pile tower crane foundation supported on an excavation slope. The steps are as follows: geologic drilling analysis is carried out on the excavation slope to draw up a construction scheme; according to the scheme, holes are dug on the excavation slope, water is pumped during the operation of digging the holes, retaining wall moulding boards are supported, and concrete retaining walls are cast. The diameter of each hole bottom is enlarged, and backing concrete is cast to form an expansion head. Independent supporting piles and the tower crane bearing foundation are cast by the concrete, the diameter of the independent supporting pile is equal to or larger than 1.42 times of the side length of each standard knot of a tower body, the depth of the independent supporting pile is equal to or larger than 1.5 times of the height of a pile foundation suspension arm, and the top face of the tower crane bearing foundation is lower than a natural terrace. The construction method has the advantages of low production cost, reliable quality, simple machines and equipment, convenient construction and operation and higher single-pile bearing force, thereby meeting the requirement of casting the tower crane bearing platform foundation; and the construction method has no noise during construction, no discharge of mud solution, little effect on ambient environment and buildings and small space occupation.

Description

The job practices on the independent pile tower crane basis of excavation slope place supporting

Technical field

The present invention relates to the tower crane of the independent stake of a kind of excavation slope place supporting, also relate to its design and job practices simultaneously, belong to technical field of building construction.

Background technology

The lagging pile of common deep foundation pit support, main function of use are in construction period opposing lateral earth pressure, prevent landslide of excavation slope soil layer and slip, and its axial bearing capacity and resistance to capsizing are all lower, can not be as the basis usefulness of tower crane.When limited by geology and site condition, in the time of can't in foundation ditch and near the foundation ditch limit tower crane being set, in the lagging pile of excavation slope, the part is chosen one and is adopted hand excavated pile castinplace pile supporting foundation pit, and utilize the independent stake of this root as tower crane, also there are many problems to need to solve.Because of the independent pile tower crane basis affords the axial force of large eccentricity, the dynamic load of repetition and the influence of soil pressure, its design and construction all will fully take into account the influence of the bearing capacity of the axial force of pattern foundation pit supporting structure, large eccentricity and antifatigue, so the building operations of excavation slope place tower crane has many problems to research and solve.

Summary of the invention

The present invention wants the technical solution problem to be: all lower at lagging pile design axial bearing capacity and resistance to capsizing, a kind of axial force that can overcome soil pressure, afford large eccentricity is proposed, the technical scheme on the independent pile tower crane basis of the excavation slope place supporting of energy antifatigue under the dynamic load effect that repeats.

Technical scheme of the present invention is that the job practices on the independent pile tower crane basis of excavation slope place supporting comprises the steps:

(1) carries out the geological drilling analysis at the excavation slope place, formulate constructure scheme;

(2) at excavation slope place borehole, draw water, support dado template, the concreting retaining wall while digging;

When (3) borehole reached projected depth, diameter at the bottom of the expanded hole will be cleaned out at the bottom of the hole, drain ponding after, cast bottom concrete and enlarged footing;

(4) concrete spouting independence soldier pile, on independent soldier pile top cast tower crane cushion cap basis, the diameter of independent soldier pile is equal to or greater than 1.42 times of the length of side of body of the tower standard knot, the degree of depth of independent soldier pile (at the bottom of the foundation ditch to enlarged footing) is equal to or greater than 1.5 times of the pile foundation cantilever height height H of tower crane cushion cap basis end face (at the bottom of the foundation ditch to), and tower crane cushion cap basis end face is lower than the nature terrace.

The present invention adopts independent manually digging hole to pour into independent soldier pile and tower crane cushion cap basis is formed, by the technology of at present existing various tower cranes has been carried out research and analysis respectively, at pattern foundation pit supporting structure, the retaining wall pile foundation, many-sides such as the design of tower crane and job practices have carried out finding after the exploratory experiment: the lagging pile of directly selecting supporting foundation pit, its axial bearing capacity and resistance to capsizing are all lower, utilize the many piles of platoon as tower crane, employing reasonable building structure, though the job practices of grasp science can be as the basis of tower crane, overturning or slip resistance analysis, antifatigue and carrying all have certain risk.The present invention is at the excavation slope place, and hand excavated pile castinplace pile supporting foundation pit is adopted in the part, and utilizes this independent soldier pile as tower crane.According to designing and calculating, adopt rational arrangement of reinforcement and construction measure, improve lagging pile design axial bearing capacity and resistance to capsizing, guarantee that independent soldier pile tower crane can bear the dynamic load and the soil pressure of the axial force of large eccentricity, repetition.This job practices cost is low, reliable in quality, and plant is simple, and constructing operation is convenient, and bearing capacity of single pile is than higher, the construction noiselessness, no mud is discharged, and surrounding environment and building is influenced little, and occupied ground is little.

Description of drawings

Fig. 1 is the independent pile tower crane foundation structure schematic diagram of excavation slope of the present invention place's supporting;

Fig. 2 is an independent soldier pile force analysis schematic diagram of the present invention;

Fig. 3 is a working face schematic diagram of the present invention;

Among the figure: at the bottom of 1 independent soldier pile, 2 enlarged footings, 3 tower crane cushion cap bases, 4 tower cranes, 5 natural terraces, 6 pile foundation cantilevers, 7 foundation ditches, 8 buildings, 9 basements, 10 side slopes.

The specific embodiment

As Fig. 1, Fig. 2, shown in Figure 3, carry out the geological drilling analysis at excavation slope 10 places of building 8 and basement 9 earlier, formulate constructure scheme; , draw water at excavation slope place borehole according to scheme, support dado template, the concreting retaining wall while digging; When borehole reached projected depth, diameter at the bottom of the expanded hole will be cleaned out at the bottom of the hole, drain ponding after, the cast bottom concrete forms enlarged footing 2; Begin with concrete spouting independence soldier pile 1 from the bottom, on the tower crane cushion cap basis 3 that tower crane 4 is installed in the cast of independent soldier pile top, the diameter of independent soldier pile is equal to or greater than 1.42 times of the length of side of body of the tower standard knot, the degree of depth of independent soldier pile is equal to or greater than 1.5 times of pile foundation cantilever 6 height, and guaranteeing has enough length at the bottom of independent soldier pile is embedded in foundation ditch below 7.Tower crane cushion cap basis end face is lower than nature terrace 5.The independent soldier pile on excavation slope place supporting independent pile tower crane basis and structure, size and the arrangement of reinforcement on tower crane cushion cap basis are according to the designing and calculating data configuration.

The independent pile tower crane Base Design of excavation slope place supporting is calculated:

1. working load calculates

The axial design payload values:

N＝1.2(N ₁+N ₂+N ₃)+1.4N ₄，

N: axial design payload values (KN),

N ₁: tower crane deadweight standard value (KN),

N ₂: tower crane cushion cap deadweight standard value (KN),

N ₂=a * b * h * 25.5; A, b, h are respectively the length on basis, and be wide, and high (m),

N ₃: independent soldier pile deadweight standard value (KN),

${\mathrm{<figure-callout\; id="3"\; label="N"\; filenames="A200910029015E00091.png"\; state="\{\{state\}\}">N</figure-callout>}}_3=\frac{1}{4}\mathrm{\&pi;}{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="A200910029015E00091.png"\; state="\{\{state\}\}">D</figure-callout>}}^2\&times;L\&times;25.1,D$ With L be respectively independent pile body diameter and the stake long (m),

N ₄: the maximum lifting weight standard value (KN) of tower crane,

The overturning moment design load,

M＝1.4M ₁+1.2M ₂，

M: under the least favorable state, overturning moment design load (KNm),

M ₁: maximum overturning moment standard value (KNm) under tower crane work or the off working state,

M ₂: slope retaining place active earth pressure, under the horizontal thrust effect, the overturning moment standard value (KNm) of formation,

${\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="A200910029015E00091.png"\; state="\{\{state\}\}">M</figure-callout>}}_2=\frac{1}{3}H\&CenterDot;D\&CenterDot;\mathrm{Ea},$

H: foundation depth (m),

E _a: the total active earth pressure of foundation ditch unit length (KN/m),

R: the averag density (KN/m of soil layer behind the foundation ditch skirt piles ³),

φ: the angle of internal friction of soil layer behind the foundation ditch skirt piles,

C: the cohesive strength (KN/m of soil layer behind the foundation ditch skirt piles ²).

2. independent soldier pile checking of bearing capacity

The pile end groundwork checking of bearing capacity:

R≥N，

R: independent soldier pile axial design bearing capacity (KN),

$R=\frac{1}{4}\mathrm{\&pi;}{D}^2{f}_{\mathrm{\&alpha;y}},$

f _{α y}: bearing course at pile end bearing capacity of foundation soil design load (KN/m ²),

2.2 independent soldier pile tower crane overturning or slip resistance analysis checking computations,

Wherein: cos45 ° of D for the pile body center of circle in connect the distance on square limit.With this moment fulcrum as overturning or slip resistance analysis.

2.3. independent soldier pile Design of Bearing Capacity,

$N\&le;\mathrm{\&alpha;}{\mathrm{\&alpha;}}_1\mathrm{fcA}(1-\frac{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="A200910029015E00091.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&pi;\&alpha;}}{2\mathrm{\&pi;\&alpha;}})+(\mathrm{\&alpha;}-\mathrm{\&alpha;t})\mathrm{fyAs},$

$\mathrm{N\&eta;}{e}_i\&le;\frac{2}{3}{\mathrm{\&alpha;}}_1\mathrm{fcAr}\frac{{\mathrm{Sin}}^3\mathrm{\&pi;\&alpha;}}{\mathrm{\&pi;}}+\mathrm{fyAs\&gamma;s}\frac{\mathrm{Sin\&pi;\&alpha;}+\mathrm{Sin\&pi;}{\mathrm{\&alpha;}}_t}{\mathrm{\&pi;}},$

αt＝1.25-2α，

e _i＝e ₀+e _a，

A: independent soldier pile circular cross-section is long-pending $\frac{1}{4}\mathrm{\&pi;}{D}^2\left(m^2\right),$

As: the sectional area (mm of whole longitudinal reinforcements ²),

γ: the radius (m of independent soldier pile circular cross-section ²),

γ _s: the radius (m of longitudinal reinforcement center of gravity place circumference ²),

e ₀: the eccentric throw (m) of axial compression pair cross-section center of gravity $e_0=\frac{M}{N},$

e _a: accidental eccentricity, its value should be got 1/30 higher value (mm) among both of the independent stake of 20mm and eccentric direction diameter dimension,

α: corresponding to the central angle (rad) of pressure zone concrete pile section area and the ratio of 2 π.

α _t: the ratio of the whole longitudinal reinforcement sectional areas of longitudinal tensile area of reinforcement and pile body, as α〉0.625 the time, get α _t=0,

Fc: independent soldier pile concrete crushing strength design load (N/mm ²),

Fy: independent soldier pile longitudinal stress reinforcing bar tensile strength design load (N/mm ²),

Annotate: the longitudinal stress bar diameter should not be less than φ 12, and all the reinforcement ratio of longitudinal reinforcement should not must not be less than 0.6% greater than 5%.

η: independent soldier pile eccentric compression member, consider the axial compression amplified coefficient of eccentricity that Order Moment influences

$\mathrm{\&eta;}=1+\frac{1}{1400\mathrm{ei}/\mathrm{\&gamma;}+{\mathrm{\&gamma;}}_s}{\left(\frac{H}{D}\right)}^2\&CenterDot;{\mathrm{\&zeta;}}_1\&CenterDot;{\mathrm{\&zeta;}}_2,$

${\mathrm{\&zeta;}}_1=\frac{0.5\mathrm{fcA}}{N},$

${\mathrm{\&zeta;}}_2=1.15-0.01\frac{H}{D},$

ζ ₁: the sectional curvature correction factor of eccentric compression independence soldier pile, work as ζ ₁1 o'clock, get ζ ₁=1,

ζ ₂: the influence coefficient of independent soldier pile slenderness ratio pair cross-section curvature, when $\frac{H}{D}<17.5$ The time, get ζ ₂=1,

2.4 the checking computations of independent soldier pile cross section shear strength,

τ _max≤[τ]，

${\mathrm{\&tau;}}_{\max }=\frac{4F_s}{3A},$

τ _Max: cross section maximum shear stress (KN/m ²),

[τ]: cross section allowable shearing stress (KN/m ²),

F _s: the suffered shearing in cross section, i.e. the active earth pressure E of slope retaining place _a(KN),

A: independent soldier pile circular cross-section is long-pending $\frac{1}{4}\mathrm{\&pi;}{D}^2\left(m^2\right).$

Claims (1)

1, the job practices on a kind of excavation slope place's supporting independent pile tower crane basis is characterized in that comprising the steps:

(1) carries out the geological drilling analysis at the excavation slope place, formulate constructure scheme;

(2) at excavation slope place borehole, draw water, support dado template, the concreting retaining wall while digging;

When (3) borehole reached projected depth, diameter at the bottom of the expanded hole will be cleaned out at the bottom of the hole, drain ponding after, cast bottom concrete and enlarged footing;

(4) concrete spouting independence soldier pile, on independent soldier pile top cast tower crane cushion cap basis, the diameter of independent soldier pile is equal to or greater than 1.42 times of the length of side of body of the tower standard knot, the degree of depth of independent soldier pile is equal to or greater than 1.5 times of pile foundation cantilever height, and tower crane cushion cap basis end face is lower than the nature terrace.

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