CN101392536A - Composite foundation of composite pile with different stiffness - Google Patents

Abstract

The invention discloses a composite foundation with compound piles in different rigidities. The composite foundation comprises a rigid pile, a flexible pile, soil and mattress layers, wherein the rigid pile adopts a long pile; the end of the rigid pile is placed in a deep force bearing layer; the rigid pile is weak in load transfer capability; the flexible pile adopts a short pile; the end of the flexible pile is placed in a shallow force bearing layer; and the rigid pile and the flexible pile adopt the mattress layers with different variable-thickness materials. Compared with the prior composite foundation, the composite foundation with compound piles in different rigidities adopts the long pile as the rigid pile which is large in effective pile length and embodies bearing capacity, and adopts the short pile as the flexible pile small in effective pile length. The composite bearing structure with the long pile and the short pile can greatly save material cost on the basis of no reduction of the bearing capacity so as to effectively utilize the bearing potential of pile bodies in the composite foundation, thereby adapting to the feature that the additional stress of the foundation decreases from the top down.

Description

Composite foundation of composite pile with different stiffness

Technical field

The present invention relates to a kind of composite foundation of composite pile with different stiffness.

Background technology

Conventional piles bluk recombination ground adopts single stake, the rigidity of stabilization zone complex is identical, because under load action, subsidiary stress increases along with the degree of depth and reduces in the ground, the ground strain also reduces gradually, required foundation stiffness is corresponding to diminish, and adopts single pile composite foundation easily to cause two kinds of bad tendencies: bottom stabilization zone rigidity is excessive to seem waste or top stabilization zone insufficient rigidity and causes the degree of safety deficiency.In addition, there is difference in the Stress Transfer ability of different-stiffness stake, and the rigid pile Stress Transfer degree of depth is dark, and the flexible pile Stress Transfer degree of depth is short, has the effective length phenomenon in stake aspect bearing capacity and the sedimentation, and the effective length of rigid pile is far longer than the effective length of flexible pile.

Summary of the invention

Technical problem to be solved by this invention is to overcome the deficiencies in the prior art, provides a kind of and can produce the composite foundation of composite pile with different stiffness that becomes rigidity.

For this reason, the invention provides a kind of composite foundation of composite pile with different stiffness, this composite foundation comprises rigid pile, flexible pile, soil and mattress layer, rigid pile adopts long stake, rigid pile stake end places darker bearing stratum, and a little less than the rigid pile Load Transfer ability, rigid pile is taked stub, rigid pile stake end places more shallow bearing stratum, and described rigid pile, flexible pile are taked thickening degree different materials mattress layer.

Compare the big rigid pile of effective length that will embody supporting capacity in the composite foundation of composite pile with different stiffness provided by the invention with the conventional composite ground and adopt long stake, and the little flexible pile of effective length adopts stub, the structure of this long stake and stub combination carrying can be saved material cost greatly on the basis that does not reduce supporting capacity, thereby more effectively utilize the carrying potential of pile body in the composite foundation, adapted to the feature that the ground subsidiary stress from top to bottom reduces.

Compare with the processing of conventional composite ground, the main advantage of this new technology has 3 points: one, engineering cost can save 20%～35%; Two, adopt this technology can handle complicated ground situation effectively, reduce traditional pile foundation soil compaction stake bad environment effect, help guaranteeing construction quality; Three, the duration of a project can shorten for 1/3～1/4 time, was fit to coastal Deep Thick Soft Ground Area and used, and had very high promotional value.This class composite foundation is applicable to multistory building and small sized multiple story building, and is especially more suitable for the building that basement is arranged.

Description of drawings

Fig. 1 composite foundation of composite pile with different stiffness schematic diagram.

Fig. 2 composite foundation of composite pile with different stiffness strip foundation form figure that lays out pile.

Fig. 3 composite foundation of composite pile with different stiffness raft foundation form figure that lays out pile.

Fig. 4 is A-A sectional drawing of Fig. 3.

The specific embodiment

As shown in Figure 1, composite foundation of composite pile with different stiffness is meant by rigid pile 5, flexible pile 6 and inter-pile soil body deformability coordinate to bear jointly the composite foundation of load, in the composite foundation of composite pile with different stiffness provided by the invention, composite foundation comprises rigid pile 5, flexible pile 6, soil and mattress layer, rigid pile 5 is the higher stakes of material stiffness, rigid pile 5 adopts long stake, because its rigid pile 5 is longer, therefore its end places darker bearing stratum, flexible pile 6 is the lower stakes of material stiffness, flexible pile 6 is taked stub, and the stake of flexible pile 6 is grown up long less than the stake of rigid pile greatly, because flexible pile 6 is shorter, therefore its end places more shallow bearing stratum, described rigid pile 5, flexible pile 6 is taked thickening degree different materials mattress layer, and mattress layer 3 thickness of cushion cap 1 following rigid pile 5 upper ends are 300mm, and mattress layer 3 adopts grit material; Flexible pile 6 place's mattress layer thickness 4 are 100mm, and mattress layer 4 adopts rubble to add the coarse sand material.Also have the thick pea gravel concreten leveling layer 2 of 100mm in addition among Fig. 1, leveling layer below 2 except that the mattress layer of flexible pile 6 and rigid pile 5 top bit other position mattress layers be 200mm.Rigid pile 5 can be reinforced concrete pile or piling bar in the present embodiment, its top absolute altitude is lower than flexible pile 6 top absolute altitude 200mm, after adopting this mode to adjust the height of piles with different, reduce the stress concentration of rigid pile 5 on the one hand, make flexible pile 6 and soil load-bearing passively on the other hand, having increased native normal stress, thereby improved pile side friction, can be cement mixing pile or lime pile at this flexible pile 6.

Below in conjunction with accompanying drawing two kinds of embodiment of the present invention are described in detail:

Composite foundation provided by the invention can adopt strip foundation and two kinds of forms of raft foundation, and as Fig. 2, Fig. 3, shown in Figure 4, when adopting strip foundation, the basis is long-pending suitable big with soil contact face, thereby increases native load share ratio.Rigid pile 5 should be arranged in the building controls sedimentation and stablize on the major control active position, as the edge stake, angle point stake and the upper load ability that are positioned at building play direct acting, and rigid pile 5 general arrangement centers of gravity should be consistent with the building centre of form.Flexible pile 6 compensates bearing capacity according to the upper load size.

When adopting raft foundation, rigid pile 5 and flexible pile 6 arrange that evenly spaced apart, looking different situations has quincunx and two kinds of arrangement forms of rectangle.Be provided with beam at rigid pile 5 positions, make lattice raft plate, avoid rigid pile 5 stress to concentrate and damage.

Total settlement of the present invention comprises the decrement and the substratum sedimentation of inter-pile soil body, and the substratum sedimentation can adopt traditional layerwise summation method to calculate, and this method can be found in the composite foundation document.The stabilization zone decrement is taked the composite modulus method, and composite modulus calculates takes following formula

$E_c=(\frac{m_1}{\frac{H_r}{E_r{\mathrm{\λ}}_r}\·\frac{{\mathrm{\γ}}_r\mathrm{th}{\mathrm{\λ}}_r+{\mathrm{\λ}}_r}{{\mathrm{\λ}}_r\mathrm{th}{\mathrm{\λ}}_r+{\mathrm{\γ}}_r}+\frac{H_d}{E_d}}+\frac{m_2}{\frac{H_f}{E_f{\mathrm{\λ}}_f}\·\frac{{\mathrm{\γ}}_f\mathrm{th}{\mathrm{\λ}}_f+{\mathrm{\λ}}_f}{{\mathrm{\λ}}_f\mathrm{th}{\mathrm{\λ}}_f+{\mathrm{\γ}}_f}+\frac{H_d}{E_d}}+\frac{1-m_1-m_2}{\frac{H_r}{E_S}+\frac{H_d}{E_d}})H_r$

E in the formula _cComposite modulus for composite foundation of composite pile with different stiffness; m ₁Be rigid pile 5 replacement ratios; m ₂Be flexible pile 6 replacement ratios; E _rModulus of deformation for rigid pile 5; E _fModulus of deformation for flexible pile 6; E _sModulus of compressibility for soil; E _dBe the mattress layer modulus; H _rFor 5 of rigid pile long; H _fFor 6 of flexible piles long; H _dBe mattress layer thickness; λ _r=μ _rH _r, μ _rBe native parameter of 5 week of rigid pile; λ _f=μ _fH _f, μ _fBe native parameter of 6 week of flexible pile; ${\mathrm{\γ}}_r=\frac{n_r{H}_r}{A_r{E}_r},$ n _rBe 5 native parameters of end of rigid pile; ${\mathrm{\γ}}_f=\frac{n_f{H}_f}{A_f{E}_f},$ n _fBe 6 native parameters of end of flexible pile; All native parameters of stake and the native calculation of parameter of stake end can be found in the pile foundation document.

Bearing capacity formula of the present invention can be taked following formula

$f_{\mathrm{sp},k}={\mathrm{\β}}_1{m}_1\frac{R_1}{A_{p1}}+{\mathrm{\β}}_2{m}_2\frac{R_2}{A_{p2}}+{\mathrm{\β}}_3(1-m_1-m_2)f_{\mathrm{sk}}$

F in the formula _{Sp, k}Be the Bearing Capacity of Composite Foundation characteristic value; m ₁Be rigid pile 5 replacement ratios; m ₂Be flexible pile 6 replacement ratios; f _{S, k}Be the inter-pile soil characteristic load bearing capacity; R ₁Be rigid pile 5 bearing capacity of single pile characteristic values; R ₂Be flexible pile 6 bearing capacity of single pile characteristic values; A _P1Section area for rigid pile 5; A _P2Section area for flexible pile 6; β ₁Be rigid pile 5 bearing capacity performance degree, numerical value is got between 0.85～1.0, β ₂Be flexible pile 6 bearing capacity performance degree, numerical value is got between 0.7～0.8, β ₃Be inter-pile soil bearing capacity performance degree, numerical value is got between 0.9～1.0.During engineering was used, soil property was poor more, the stake replacement ratio is high more, building is important more, and bearing capacity performance degree is got high value; Otherwise get low value.

The present invention includes following construction sequence: first construction rigid pile 5 flexible pile 6 of constructing again, but rigid pile 5 and flexible pile 6 continuous productive processes, when partially rigid stake 5 construction finish reserve work plane after, just can organize flexible pile 6 construction of marching into the arena, thereby to shorten the construction period greatly than the conventional composite foundation construction period.

Detection mode of the present invention will adopt the composite foundation static load test, and composite foundation static load test area is taked the identical fritter equivalent area of replacement ratio, and stock mould is set around mattress layer, and mattress layer should pass through precompressed before loading.The static load test curve is gradual shape usually, determines the Bearing Capacity of Composite Foundation characteristic value according to sedimentation and bearing plate relative deformation value 0.002～0.003 corresponding bearing capacity.

Claims (6)

1, a kind of composite foundation of composite pile with different stiffness, it is characterized in that: this composite foundation comprises rigid pile, flexible pile, soil and mattress layer, rigid pile adopts long stake, rigid pile stake end places darker bearing stratum, flexible pile is taked stub, flexible pile stake end places more shallow bearing stratum, and described rigid pile, flexible pile are taked thickening degree different materials mattress layer.

2, composite foundation of composite pile with different stiffness according to claim 1 is characterized in that: flexible pile is cement mixing pile or lime pile.

3, composite foundation of composite pile with different stiffness according to claim 1 and 2 is characterized in that: rigid pile is reinforced concrete pile or piling bar.

4, composite foundation of composite pile with different stiffness according to claim 1 and 2, it is characterized in that: reduce the high 100mm of rigid pile stake top mark, increase the high 100mm of flexible pile stake top mark, strengthen rigid pile position mattress layer thickness 100mm, reduce flexible pile position mattress layer thickness 100mm; Rigid pile position mattress layer adopts the low material of modulus, and flexible pile position mattress layer adopts the high material of modulus.

5, composite foundation of composite pile with different stiffness according to claim 4 is characterized in that: rigid pile position mattress layer adopts grit material; Flexible pile position mattress layer adopts rubble to add the coarse sand material.

6, composite foundation of composite pile with different stiffness according to claim 1 and 2 is characterized in that: rigid pile is reinforced concrete pile or piling bar, and rigid pile stake top absolute altitude is lower than flexible pile stake top absolute altitude 200mm.

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