CN1047219C

CN1047219C - Design and construction method for large calibre poured pile and large-diameter bottom-enlarging pier

Info

Publication number: CN1047219C
Application number: CN 93115995
Authority: CN
Inventors: 孟凡林
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-06-18
Filing date: 1993-12-28
Publication date: 1999-12-08
Anticipated expiration: 2013-12-28
Also published as: CN1111308A

Abstract

The present invention relates to a novel method for the design and the construction of a large-caliber filling pile and a large-diameter bottom-enlarging pier, which belongs to the generalization and the application of a shotcrete technology in the basis of a building foundation in building science. The novel method is mainly characterized in that a well-sinking wall protection method and a cast-in-situ wall protection method are substituted by a shotcrete wall protection method. The technology can improve the bearing capacity and the reliability of a pile, improve the work efficiency, save the labour, reduce the engineering cost, shorten the construction period and have large social benefit and economic benefit.

Description

The job practices of large-diameter bored pile and large diameter belled pier

The present invention is the job practices of large-diameter bored pile and large diameter belled pier, and affiliated field is the application of concrete-spraying technology in large-diameter bored pile and large diameter belled pier design and construction in the building foundation science.

Prior art and the technological document relevant with invention:

Concrete-spraying technology

" Code for design of building (GBJ7-89) "

" steel concrete Designing Structures of High Rising Buildings and construction regulations (JBJ3-91) "

" Code for design of concrete structures (GBJ10-89) "

The design and construction method of existing large-diameter bored pile, large diameter belled pier has two kinds:

(1) open caisson retaining wall method

Precast open caisson earlier and do retaining wall and be placed on the station, excavation renews a joint until digging to design elevation behind the joint that avales then, when calculating bearing capacity of single pile, does not consider the effect of retaining wall, only gets inner diameter d as the pile body calculated diameter.Because can not consider the effect of frictional force and retaining wall, bearing capacity is lower.If smooth in order to sink, the external diameter of excavation is too big, also can produce negative friction.

(2) cast-in-place retaining wall method

Whenever at the medial branch cope match-plate pattern, concrete placing then is until design elevation after digging one section.When calculating bearing capacity of single pile, except that frictional force, do not consider the effect of retaining wall.This method is propped up form removal inconvenience, long in time limit.Because of retaining wall can not be too thick, it is closely knit that concrete is difficult to cast, and upward the connection of hypomere joint part is unreliable, also is difficult to form one with the back pouring concrete.

No. 90108927.3 patent disclosures of known Chinese invention patent the perfusion prefabricating composite pile piling method.It is characterized in that before the concrete initial set of perfusion, squeeze into a prefabricated stake core at the center, behind the excavation pit, weld out connecting reinforcement from preformed pile, this method has been avoided broken pile and necking down accident, but more complicated, the inconvenience construction.

92104708.8 number patent " method of field casted pile forming with ash cement slurry wall protecting ", owing to adopt ash cement slurry low pressure retaining wall, perfusion grating concrete can guarantee pile quality, reduce cost, reduce to pollute, be applicable to pile under the geological conditions of underground water and quicksand.

Purpose of the present invention:

Improve the design and construction method of existing large-diameter bored pile.

With several retaining wall methods before the replacement of sprayed mortar retaining wall method, the bearing capacity of raising stake and reliability, raising construction efficiency, reduction cost, shortening construction period.

Summary of the invention:

In the design and construction of existing borehole large-diameter bored pile and large diameter belled pier, introduce concrete-spraying technology, at first make circular steel concrete snare by intended diameter, be put on the station, in snare,, be a construction section about every excavation 1m, around Tu Bi, established the jet thickness sign with artificial or mechanical equivalent of light excavation, from bottom to top spray with concrete sprayer, when constructing to design elevation, can at the bottom of the hole, stamp bed course, carry out the construction of pile body then.The concrete that sprays usefulness have coagulate soon, characteristics such as fast hard, strong, antiseepage early, expansion, make breast wall concrete coagulate, can guarantee by force hard, morning soon the continuity that borehole is constructed soon, accelerating construction progress: make breast wall concrete antiseepage, expansion, can prevent that the water in the soil from infiltrating in the hole, cause the instability of soil, can improve stake and native frictional force again, improve bearing capacity.Do the retaining wall in a hole with sprayed mortar or arrangement of reinforcement sprayed mortar, around hole wall, dug ring-shaped groove, to improve stake and native frictional force, around hole wall, insert some reinforcing bars, strengthen the stability of the soil body and retaining wall, the retaining wall inboard is sprayed into the band of ring uplift, with the interlock effect of raising with the back pouring concrete.

Concrete job practices:

At first make circular steel concrete snare by intended diameter, wall thickness is 10-20cm, and height is 50-60cm, and the height that exposes on ground is 15-20cm, enters in the hole to prevent foreign material.With artificial or mechanical equivalent of light excavation, strict with designing requirement controlling dimension and shape in circular snare, ring-shaped groove on every side is according to the size of stake, and the situation of bearing capacity and soil and deciding is changeable, can establish also and can not establish.Be a construction section about every excavation 1m, around Tu Bi, established the sign of jet thickness (being generally about 10cm), if soil body instability can shorten construction section.Carry out the preparation before the construction, adhere rigidly to technological process and construction point with the spraying machine of packing into after stirring that weighs such as stone, sand, cement, cooperate air compressor machine and high-pressure water tank again, from bottom to top spray.When constructing to design elevation, can at the bottom of the hole, stamp bed course, carry out the construction of pile body then.Though retaining wall has certain antiseepage effect, if when in the cutting depth scope, underground water being arranged, precipitation at first before the excavation.

Advantage or good effect:

(1) supporting capacity and the reliability of raising stake

Sprayed mortar is under the high pressure effect, and concrete can be closely linked with soil well, and expansive concrete makes retaining wall give birth to compressive pre-stress to local products, adds ring-shaped groove, can make pile body and soil form one, and co-operation improves frictional force greatly.When the design of stake, not only can consider the friction of retaining wall, and can consider bearing capacity of pile tip as the part of pile body.Present open caisson retaining wall, frictional force can not be considered, and also can produce negative friction sometimes; The cast-in-place retaining wall of formwork, because retaining wall can not be done too thickly, so it is closely knit to be difficult to cast, upper and lower concrete joint stubble is unreliable, thereby greatly reduces the bearing capacity of stake.

(2) reduce construction costs

Because the bearing capacity of stake has improved, under identical design load situation, its scale of construction of stake of this method design reduces, thereby reduces material consumption, reduces construction costs.The cost of general stake can reduce 20%-30%.

(3) improve work efficiency, save the labour

The general open caisson difficulty of open caisson construction, especially darker stake, it is smooth to want open caisson, just must enlarge the borehole external diameter, and this certainly leads to the said negative friction in front, and eccentric difficult correction of open caisson.

The cast-in-place retaining wall of formwork needs formwork, concrete placing, maintenance, and the formwork form removal all needs for a long time, and work efficiency is low.

Sprayed mortar can spray while digging, and can construct continuously, has sprayed to dig down, digs and can spray, and has greatly improved work efficiency, has saved the labour again simultaneously, and this point also can reduce construction costs.

(4) shorten the construction period

Because sprayed mortar panelling construction worker is simple, and borehole is carried out continuously, improve work efficiency, must shorten the construction period.

Description of drawings:

Fig. 1: retaining wall way

Among the figure 1, foundation soil; 2, sprayed mortar or arrangement of reinforcement sprayed mortar retaining wall; 3, sprayed mortar in the groove; 4, be sprayed into the concrete band of protuberance; 5, insert the interior reinforcing bar of the soil body.

Realize the embodiment of this technology:

New Development big world, Changchun engineering foundation is one on a post.H wherein _a-D _bThe bearing capacity of single pile design load of axle is 9800KN, if adopt cast-in-place retaining wall method construction, pile body diameter is 1.35m, and the enlarged footing diameter is 2.65m, and stake is long to be 15.9m, and the engineering time is taken 30 days at least; The actual sprayed mortar retaining wall method that adopts is constructed, and pile body diameter is 1.2m, and the enlarged footing diameter is 2.5m, and stake is long to be 15.9m.Engineering time is 7 days.Like this, material consumption reduces by 25%, and the duration shortens significantly.

Claims

1, the job practices of large-diameter bored pile and large diameter belled pier, it is characterized in that: at first make circular steel concrete snare by intended diameter, be put on the station, in snare,, be a construction section about every excavation 1m, around Tu Bi, established the jet thickness sign with artificial or mechanical equivalent of light excavation, from bottom to top spray with concrete sprayer, when constructing to design elevation, can at the bottom of the hole, stamp bed course, carry out the construction of pile body then.

2, press the described job practices of claim 1, it is characterized in that being the frictional force that improves stake and soil, can around hole wall, dig ring-shaped groove, be the interlock effect of raising, be sprayed into the band of ring uplift in the retaining wall inboard with the back pouring concrete.

3, by the described job practices of claim 1, it is characterized in that wall thickness is 10-20cm by the circular concrete snare of intended diameter making, height is 50-60cm, enters for preventing foreign material, exposes on ground highly for about 20cm.

4,, it is characterized in that employing is coagulated soon, fast hard, early strength concrete in order to make breast wall concrete hard soon, early strong, stable by the described job practices of claim 1.

5,, it is characterized in that adopting impervious concrete for making the retaining wall antiseepage by the described job practices of claim 1.

6, by the described job practices of claim 1, it is characterized in that being the frictional force that improves stake and soil, make around the stake the compacted and employing expansive concrete of soil.