CN101436217A - New method of double-layer steel plate high-strength high-performance concrete composite borehole wall design calculation - Google Patents

Abstract

The invention discloses a design calculation method for a double-layer steel plate high-strength and high-performance concrete composite shaft lining, which comprises: firstly, determining fundamental parameters of the shaft lining according to the experience analogy method; secondly, solving the principal stress value of internal marginal concrete by adoption of a formula of an elastic combined cylinder, and introducing the increasing coefficient m of the compressive strength of the concrete; and thirdly, checking the structural strength of the shaft lining according to the formula of k1.k2.sigma<max> is less than or equal to m.f<c>, wherein k1 refers to the structure importance coefficient and takes the value of 1.1; k2 refers to the partial load coefficient and takes the value of 1.35; sigma<max> refers to the maximum value of the absolute value of the principal stress of the concrete in a shaft lining structure; and f<c> refers to the design value of the uniaxial compressive strength of the concrete. As proved by example calculation, the shaft lining structure designed by the novel method not only is safe and reliable but also greatly reduces the design strength grade of the concrete of the shaft lining or thins the thickness of the shaft lining, and solves the technical problems of design and construction of the shaft lining structure of an extra-thick surface soil layer drilled well. Currently, the method has been successfully applied to actual design of the shaft lining structure of engineering.

Description

Double-layer steel plate high-strength high-performance concrete composite borehole wall designing and calculating new method

Technical field

The invention belongs to a kind of borehole wall design and calculation method, specifically is a kind of double-layer steel plate high-strength high-performance concrete composite borehole wall design and calculation method.

Background technology

At present, the home and abroad is adopted elasticity combination tube method and is breathed out. Lin Kefa the design of double-layer plate high-strength concrete composite shaft lining is main.

Elasticity combination tube method supposition steel plate, middle concrete layer are all elastic body, composite shaft lining is considered as elasticity combination tube, and inside and outside steel plate tube is a book wall tube, middle concrete layer is a thicl-walled cylinder, the derivation of equation is to obtain each interlayer pressure with book, thicl-walled cylinder displacement formula and each interlayer surface of contact deformation compatibility condition earlier, obtain each layering section stress by single thin, thicl-walled cylinder Stress calculation formula then, at last with allowable stress method design composite shaft lining.

Breathe out. Lin Kefa and utilize the loop configuration that meets the plane supposition, obtain internal force on the borehole wall cross section by method of material mechanics, considered the unevenness that normal stress distributes in the borehole wall cross section, be that moment of flexure on the cross section is also relevant with evenly load, by interior when making every effort to stress, think inside and outside the borehole wall cross section, the condition of work of edge is identical, suppose that the size of each ply stress on the cross section is proportional to the ratio of layers of material elastic modulus, and with composite shaft lining by steel plate and concrete bullet mould than the borehole wall that is converted into a kind of equivalent material after, obtain each stress on the borehole wall cross section, at last with allowable stress method design composite shaft lining.

This shows, these two kinds of methods all adopt theory of elastic mechanics to obtain each stress on the borehole wall cross section, adopt concrete in uniaxial compressive strength design load to carry out intensity nuclear school then, and do not consider concrete in the double-layer plate high-strength concrete composite shaft lining structure owing to be in that compressive strength is improved largely under complete three compression chord states.

Summary of the invention

The purpose of this invention is to provide a kind of double-layer steel plate high-strength high-performance concrete composite borehole wall design and calculation method, more existing elasticity combination tube method, Kazakhstan. Lin Kefa compare, and accuracy in computation improves a lot, and the shaft wall structure of design can reflect its true and reliable degree.

Technical scheme of the present invention is as follows:

Double-layer steel plate high-strength high-performance concrete composite borehole wall designing and calculating new method, it is characterized in that: at first adopt heuristic methods to determine the basic parameter of shaft wall structure according to the pit shaft engineering geological condition, obtain the concrete principle stress value of borehole wall inner edge by elasticity combination tube formula then, introduce concrete crushing strength according to concrete multi-shaft strength relevant regulations in borehole wall model test result and " Code for design of concrete structures " again and improve Coefficient m, carry out the shaft wall structure strength check according to following formula at last:

Double-layer plate high-strength concrete composite shaft lining: k ₁K ₂σ _Max≤ mf _c

In the formula: k ₁Be coefficient for importance of structure, be taken as 1.1; k ₂Be partial safety factor for load, be taken as 1.35; σ _MaxMaximal value for concrete principle stress absolute value in the shaft wall structure; f _cBe concrete in uniaxial compressive strength design load;

Repeatedly calculate the borehole wall parameter designing value that is optimized at last by said process.

The inventive method proposes the basis:

(1), borehole wall concrete crushing strength improves the coefficient trial value

Ultimate bearing capacity according to a large amount of borehole wall model failure tests, concrete average maximum of hoop stress in cross section when adopting limit equilibrium method can try to achieve shaft wall structure destruction, with the ratio of its value with the concrete axial compressive strength, be called concrete crushing strength and improve coefficient, mean value is 1.4～2.3 usually.

(2), " Code for design of concrete structures " (GB50010-2002) relevant regulations

" Code for design of concrete structures " be 5.2.8 bar regulation (GB50010-2002): the two dimension of non-leverage or three-dimensional structure can adopt elasticity analysis, finite element analysis or test method to determine that its elastic stress distributes, determine required quantity of reinforcement and layout according to the principal tensile stress area of graph, and check concrete intensity by multi-axis stress state.Concrete multi-shaft strength and failure criteria can calculate by the regulation of appendix C.

C.3.3 under three pressurizeds (pressure-pressure-pressure) stress state, concrete compressive strength (f ₃) can be according to stress ratio σ ₁/ σ ₃Press accompanying drawing 1 interpolation and determine that its highest intensity value should not surpass 5f _c ^*

Double-layer plate high-strength concrete combined drilling shaft wall structure is because the effect of contraction of inside and outside steel plate tube, middle concrete layer is in three compression chord states fully, concrete compressive strength will be improved largely, adopt the shaft wall structure of the inventive method design can reflect its true and reliable degree.

Show by example calculation, adopt the shaft wall structure of the inventive method design not only safe and reliable, but also can reduce concrete design strength grade of the borehole wall or attenuate thickness of shaft wall greatly, solved a special thick alluvium drilling shaft lining structure Design and an operating technique difficult problem.At present, the inventive method successfully is applied in the shaft wall structure design of engineering reality.

Description of drawings

Fig. 1 is that concrete three compressive strength improve coefficient.

Embodiment

Double-layer plate high-strength concrete combined drilling shaft wall structure designing and calculating adopts trial and error procedure, promptly at first rule of thumb analogy method is determined the basic parameter of the borehole wall, adopt three layers of combination tube of Elasticity method to obtain the concrete principle stress value of inner edge then, obtain the ratio of principal stresses (σ ₁/ σ ₃), look into the concrete crushing strength that Fig. 1 obtains in the double-layer plate high-strength concrete composite shaft lining structure again and improve coefficient, carry out borehole wall concrete strength according to following formula at last and check.

k ₁·k ₂·σ _max≤m·f _c (2)

In the formula: k ₁Be coefficient for importance of structure, be taken as 1.1; k ₂Be partial safety factor for load, be taken as 1.35; σ _MaxMaximal value for concrete principle stress absolute value in the shaft wall structure; f _cBe concrete in uniaxial compressive strength design load.

By the said process repeated calculation, the borehole wall parameter designing value that is optimized at last.

Calculated example

Certain ore deposit main shaft is the darkest, the big pit shaft of present home and abroad wellbore construction.This well designs clean diameter 6.2m, passes the thick 584.1m of topsoil; Adopt double-layer plate high-strength concrete composite shaft lining structure, existing primary election control load section thickness of shaft wall 850mm, C70 concrete (its uniaxial compressive strength design load is 31.8MPa), ectonexine steel plate thickness are respectively 30mm and 25mm.

It is P=0.012H=0.012 * 584.1=7.0MPa that the borehole wall bears wall pressure.

Adopt elasticity combination tube formula, can try to achieve interlayer power P ₃₂=6.237MPa; P ₂₁=1.241MPa;

Concrete layer inner edge circumference stress σ _{θ max}=-28.68MPa;

σ then ₁=-1.241MPa, σ ₃=-28.68MPa,

Consider by plane strain state:

σ ₂＝0.2×(-1.241-28.68)＝-5.98；

If consider stratum settlement, adopt vertical contractibility shaft wall structure, the control vertical stress is 1.5 times of gravity stresses,

Then

σ ₂＝-0.026×584.1×1.5＝-22.78MPa

σ ₂/σ ₃＝0.209～0.794，σ ₁/σ ₃＝0.0433

According to top stress ratio, look into Fig. 1 and can get borehole wall inner edge concrete crushing strength to improve coefficient be m=1.373.

Concrete layer outer rim circumference stress σ _{θ max}=-23.69MPa;

σ then ₁=-6.237MPa, σ ₃=-23.69MPa,

If consider 1.5 times of gravity stresses:

σ ₂＝-0.026×584.1×1.5＝-22.78MPa

σ ₂/σ ₃＝0.961，σ ₁/σ ₃＝0.263

According to top stress ratio, look into Fig. 1 and can get borehole wall outer rim concrete crushing strength to improve coefficient be m=4.186.

By above calculating as can be known, inside and outside edge concrete crushing strength raising coefficient is respectively 1.373 and 4.186 in the shaft wall structure.This design and construction to deep topsoil drilling shaft lining has crucial meaning.

Because the inner edge of the double-layer plate high-strength concrete combined drilling borehole wall is a dangerouse cross-section, following for this reason employing formula (2) is checked borehole wall concrete strength.

k ₁·k ₂·σ _max＝1.1×1.35×28.68＝42.59MPa

≤m·f _c＝1.373×31.8＝43.66MPa

By checking computations, intensity meets the demands.

Calculate as the design new method that does not adopt this paper to propose, and still adopt H. Lin Kefa and elasticity combination tube method to design this main shaft (concrete crushing strength of promptly not considering following formula the right improves coefficient 1.373), according to the requirement of borehole wall Design of Bearing Capacity, under the situation that does not increase thickness of shaft wall, then the concrete uniaxial compressive strength design load of the borehole wall should be

f _c≥1.1×1.35×28.68＝42.59MPa

Show that by concrete crushing strength design load extension is calculated borehole wall design should be adopted the super high strength concrete of C100 grade at least, its compressive strength design load is 43.2MPa.So the concrete of high strength grade is being difficult to construct under site operation technical merit and the raw material supply condition at present.

For this reason, as the C70 concrete that still adopts present scene to construct, have only by strengthening thickness of shaft wall and satisfy requirement for bearing capacity, then the concrete maximum of hoop stress of inner edge is in the borehole wall

σ _max≤f _c/k ₁·k ₂＝31.8/1.1×1.35＝21.414MPa

By tentative calculation as can be known, keeping under the constant situation of inside and outside steel plate thickness, the minimum thickness of the borehole wall should be 1700mm, and the concrete circumference stress of inner edge is 21.278MPa in the borehole wall at this moment, less than 21.414MPa, satisfies requirement of strength.But by result of calculation as seen, thickness of shaft wall is too big, far surpasses the net thickness of drilling shaft lining, and intensity usefulness is too low, should not adopt sinking by boring.

This shows, in the double-layer plate high-strength concrete combined drilling shaft wall structure design of special thick alluvium, the designing and calculating new method that adopts this patent to propose not only meets relevant regulations, sidewall safety is reliable, but also can reduce concrete design strength grade or attenuate thickness of shaft wall greatly, the deep topsoil drilling shaft lining of guaranteeing to design is in the net thickness scope, solve the designing technique difficult problem of the special thick alluvium drilling shaft lining of 500～800m, had the significant social economic benefit.

Claims (1)

1, double-layer steel plate high-strength high-performance concrete composite borehole wall designing and calculating new method, it is characterized in that: at first adopt heuristic methods to determine the basic parameter of shaft wall structure according to the pit shaft engineering geological condition, obtain the concrete principle stress value of borehole wall inner edge by elasticity combination tube formula then, introduce concrete crushing strength according to concrete multi-shaft strength relevant regulations in borehole wall model test result and " Code for design of concrete structures " again and improve Coefficient m, carry out the shaft wall structure strength check according to following formula at last:

Double-layer plate high-strength concrete composite shaft lining: k ₁K ₂σ _Max≤ mf _c

In the formula: k ₁Be coefficient for importance of structure, be taken as 1.1; k ₂Be partial safety factor for load, be taken as 1.35; σ _MaxMaximal value for concrete principle stress absolute value in the shaft wall structure; f _cBe concrete in uniaxial compressive strength design load;

Repeatedly calculate the borehole wall parameter designing value that is optimized at last by said process.

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