CN103761400B - Band supporting leg diaphram wall computational methods under horizontal loads - Google Patents

Abstract

The present invention relates to band supporting leg ground diaphragm wall computational methods under horizontal loads.The present invention is directed to the band distinctive structural form of supporting leg diaphram wall, first revise and improve ordinary elasticity grade beam method finite element program, establishment variation rigidity elastic foundation method finite element program, the internal force under horizontal loads and the engineering calculating method of horizontal displacement is formed in conjunction with supporting leg interface degree of depth decision method, during so that it uses as outer wall of basement and foundation pit enclosure structure, the lateral pressure of the soil body can be born.The present invention can make project planner carry out design and the calculating of band supporting leg diaphram wall quickly and efficiently.

Description

Band supporting leg diaphram wall computational methods under horizontal loads

Technical field

The invention belongs to Geotechnical Engineering in civil engineering, base pit engineering technical field, relate to a kind of water Band supporting leg diaphram wall computational methods under flat load action.

Background technology

Along with city size expands, skyscraper is increasing, and the basement degree of depth is constantly deepened；Along with warp Ji development, for protection urban environment and quality, each big city, the world includes that domestic each big and medium-sized cities are all carried out The exploration that road develops to underground.The underground space is built like a raging fire, ground deep in its process of construction, thick Lower diaphragm wall technology is widely applied.Diaphram wall construction costs is high, and difficulty of construction is big, actual Application there is problems:

1, it is only used as the permanent exterior enclosure wall of basement, does not consider to bear vertical uniform load q.

2, in soft soil foundation, insertion depth is big, and difficulty of construction and construction costs increase.

3, the excavation of foundation pit degree of depth is big, and when bedrock surface buries shallow, diaphram wall must enter basement rock certain depth. Diaphram wall enters basement rock, causes difficulty of construction and construction costs to be significantly increased.

Domestic foundation ditch project deep, big is numerous, and bigger cutting depth is plus certain insertion depth, in addition Building enclosure length is long, and only bracing engineering one just account for the ratio that construction costs is bigger.Work as geological conditions Complexity, existing deep weak soil, also there is the basement rock that buried depth is shallower, subterranean wall tunneling boring enters basement rock Construction cost is high.

If arranging supporting leg under diaphram wall, replace common diaphram wall with band supporting leg diaphram wall, Then in the base pit engineering of deep soft soil foundation condition, when using as building enclosure, under wall, supporting leg can hold Load part of horizontal load, replaces the deficiency of bottom diaphram wall building-in depth, thus it is continuous to reduce underground The degree of depth of wall.When basement rock buried depth is shallower, diaphram wall does not enter supporting leg under basement rock, only wall and enters Basement rock certain depth, now under wall, supporting leg can make up the deficiency of diaphram wall insertion depth, reduces underground The wall degree of depth and difficulty of construction.Use band supporting leg diaphram wall will bring significant Social and economic benef@. Therefore, use band supporting leg diaphram wall, work can be reduced under conditions of guaranteeing original engineering safety degree Journey cost and difficulty of construction, reduce the work progress impact on surrounding enviroment, and economic and social benefit is notable.

External huge ultradeep foundation pit project is less, currently without band supporting leg diaphram wall correlational study and report Road.Domestic only Guangdong Province Base Engineering Co., Ltd 1997 is in Zhujiang Power Plant water intake pumping station engineering and 1999 Year has carried out the Construction practices of band supporting leg diaphram wall in the commercial and residential building engineering of moral garden, Guangzhou one.The former Pump house planar dimension is 39m × 52m, cutting depth about 9.6m；The latter foundation ditch area about 4600m², open Dig degree of depth 9m.The two scale of the project is little, has limitation, and is only limitted to Construction practices, not to band The stress of supporting leg diaphram wall and deformation characteristic, the scope of application etc. carry out system practice and theoretical research.

Band supporting leg diaphram wall is Novel underground diaphragm wall form, and current national standard sets the most accordingly Meter method.It is limited that diaphram wall bears the common Vertical elastic foundation beam that level uses when load action Metaprogram, the stiffness matrix of its unit is the most consistent, it is impossible to wall section in reflection band supporting leg diaphram wall Lateral rigidity difference with supporting leg section.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, it is provided that under a kind of horizontal loads, band supporting leg underground is even Continuous wall computational methods.

First the present invention revises and improves ordinary elasticity grade beam method finite element program, and establishment variation rigidity is elastic Grade beam method finite element program, is formed under horizontal loads in conjunction with supporting leg interface degree of depth decision method Internal force and the engineering calculating method of horizontal displacement, so that it makes as outer wall of basement and foundation pit enclosure structure Used time, the lateral pressure of the soil body can be born.

The present invention comprises the steps:

Step 1, use elastic foundation method finite element program, carry out the internal force of diaphram wall, deformation and Stability analysis, obtains underground diaphragm wall inner force, deforms the relation curve with the degree of depth, and determine suitably Lower diaphragm wall thickness, this diaphram wall thickness is band supporting leg underground continuous wall section thickness.

The reasonable judgement of step 2, number of legs, size and the degree of depth:

(1) tentatively draft number of legs, sectional dimension under wall section, obtain the stiffness ratio of wall section and supporting leg r_I, supporting leg level to bearing capacity f_l, including bending resistance and shear-carrying capacity.

(2) underground diaphragm wall inner force that obtains according to step 1, deformation are with the relation curve of the degree of depth, at base The descending branch scope of the hole following internal force in the end, determines interior force value F=f_l/r_IThe corresponding degree of depth.This is deep for preliminary judgement Degree is the interface location of wall section with supporting leg, the namely position on supporting leg top.

(3) band supporting leg diaphram wall sectional dimension, wall section and supporting leg depth parameter are preliminarily formed.

Step 3, improvement elastic foundation method finite element program, arrange variation rigidity switch so that supporting leg Duan Fan Enclose beam on elastic foundation rigidity=wall segment limit beam on elastic foundation rigidity/r_I, thus form variation rigidity beam on elastic foundation Method finite element program.Use variation rigidity vertical elastic FInite Element program, carry out carrying under horizontal loads The internal force of supporting leg diaphram wall and deformation Check checking computations, position, the internal force of supporting leg to supporting leg interface Check.

Step 4, when calculated supporting leg internal force more than the level of supporting leg to bearing capacity f_lTime, reduce supporting leg Interface location.Return step 3, recalculate, until the internal force of supporting leg meet its level to bearing capacity and The deformation requirements of surrounding enviroment.

Step 5, internal force according to the band supporting leg diaphram wall determined, carry out wall section and the arrangement of reinforcement of supporting leg section Design calculates, wall section and supporting leg section Bend, Shear checking of bearing capacity.Wherein wall section and Supporting leg section Bend, Shear checking of bearing capacity formula are as follows:

1) wall section unit width flexure checking of bearing capacity:

$M\≤{\mathrm{\α}}_1{f}_{c}x(h_o-\frac{x}{2})+{f_y}^{\′}{A_s}^{\′}(h_o-a^{\′})$

Concrete compression district height x determines as the following formula:

α₁f_cX=f_yA_s-f_y′A_s′

In formula, M represents the moment-curvature relationship of wall section；α₁Represent coefficient, according to " the Concrete Structure Design is advised Model " the devise a stratagem calculation of GB50010 6.2.6 rules and regulations；f_cRepresent concrete axial compressive strength design load；A_sTable Show the area of section of tensile region longitudinal reinforcement；A_sThe area of section of ' expression compressive region longitudinal reinforcement；h_oRepresent Effective depth of section；A represents that tensile region longitudinal reinforcement Resultant force is to the distance at tension edge；A ' represents pressurized District's longitudinal reinforcement Resultant force is to the distance at pressurized edge；f_yRepresent that the tensile strength of tensile region longitudinal reinforcement sets Evaluation, f_yThe tensile strength design load of ' expression compressive region longitudinal reinforcement；

2) the flexure checking of bearing capacity of supporting leg section:

$M_l\≤{\mathrm{\α}}_1{f}_c{b}_{l}x(h_o-\frac{x}{2})+{f_y}^{\′}{A_s}^{\′}(h_o-a^{\′})$

M in formula_lRepresent the moment-curvature relationship of supporting leg section；b_lRepresent the width of supporting leg.

3) wall section Shear checking of bearing capacity:

$V_{cs}\≤0.7f_t{h}_o+f_{yh}\frac{A_{sh}}{s}{h}_o$

V in formula_csRepresent the shearing force design value of wall section.f_tRepresent concrete axial tensile strength design load；f_yhTable Show the tensile strength design load of wall section horizontal reinforcement；A_shIn the same interface of expression configuration, horizontal steel bar is complete Portion's area of section；S represents the horizontal bar spacing along subterranean wall length direction.

4) supporting leg section Shear checking of bearing capacity:

$V_{lcs}\≤0.7f_t{b}_l{h}_o+f_{lyh}\frac{A_{lsh}}{s_l}{h}_o$

V in formula_lcsRepresent concrete and the shear resistance capacity design load of horizontal bar of supporting leg.f_lyhRepresent a leg cuff The tensile strength design load of muscle；A_lshRepresent the face, gross section of each limb of supporting leg stirrup in same cross section that is arranged in Long-pending；s_lRepresent the supporting leg stirrup spacing along supporting leg length direction.

Beneficial effects of the present invention: the present invention can make project planner carry out band supporting leg quickly and efficiently The design of diaphram wall and calculating.

Accompanying drawing explanation

Fig. 1 is wall section unit width flexure bearing capacity calculation schematic diagram.

Detailed description of the invention

Below in conjunction with the accompanying drawings embodiments of the invention are elaborated: the present embodiment is with the technology of the present invention Implement under premised on scheme, give detailed embodiment and concrete operating process, but this Bright protection domain is not limited to following embodiment.

When being used as building enclosure and the outer wall of basement of building basement foundation ditch with supporting leg diaphram wall, main Level to be born is to soil pressure effect.It is general that general diaphram wall bears that level uses when load action Logical Vertical elastic foundation beam finite element program, the stiffness matrix of its unit is the most consistent, it is impossible to reflection band The lateral rigidity difference of wall section and supporting leg section in lower limb diaphram wall.To this end, correction of the present invention is the most vertical Finite element method for beam on elastic foundation program, revises its stiffness matrix expression formula, forms variation rigidity vertical elastic ground Beam finite element program；Based on variation rigidity Vertical elastic foundation beam finite element program, establish horizontal lotus Band supporting leg diaphram wall System Design Calculational Methods under load effect.

Calculation procedure is designed as follows under band supporting leg diaphram wall horizontal loads:

1, use ordinary elasticity grade beam method finite element program, carry out the internal force of common diaphram wall, change Shape and stability analysis, obtain common underground diaphragm wall inner force, deform the relation curve with the degree of depth, and determine Suitably diaphram wall thickness, this diaphram wall thickness is band supporting leg underground continuous wall section thickness.

2, the reasonable judgement of supporting leg parameter (quantity, size and the degree of depth):

(1) tentatively draft number of legs, sectional dimension under wall section, obtain the stiffness ratio of wall section and supporting leg r_I, supporting leg level to bearing capacity f_l, including bending resistance and shear-carrying capacity.

(2) according to the 1st the common underground diaphragm wall inner force obtained with the change curve of the degree of depth, at base The descending branch scope of the hole following internal force in the end, determines interior force value F=f_l/r_IThe corresponding degree of depth.This is deep for preliminary judgement Degree is the interface location of common wall section with supporting leg, the namely position on supporting leg top.

(3) band supporting leg diaphram wall sectional dimension, wall section and supporting leg depth parameter are preliminarily formed.

3, improve ordinary elasticity grade beam method finite element program, variation rigidity switch is set so that supporting leg Duan Fan Enclose beam on elastic foundation rigidity=wall segment limit beam on elastic foundation rigidity/r_I, thus form variation rigidity beam on elastic foundation Method finite element program.Use variation rigidity vertical elastic FInite Element program, carry out carrying under horizontal loads The internal force of supporting leg diaphram wall and deformation Check checking computations, position, the internal force of supporting leg to supporting leg interface Check.

4, the supporting leg internal force calculated is more than the level of supporting leg to bearing capacity f_lTime, reduce supporting leg interface location. Return 3, recalculate, until the internal force of supporting leg meets its level and wants to the deformation of bearing capacity and surrounding enviroment Ask.

5, according to the internal force of the band supporting leg diaphram wall determined, wall section and the Reinforcement Design of supporting leg section are carried out Calculate, wall section and supporting leg section Bend, Shear checking of bearing capacity.Wherein wall section and supporting leg Section Bend, Shear checking of bearing capacity formula are as follows:

1) wall section unit width flexure checking of bearing capacity, sees Fig. 1

$M\≤{\mathrm{\α}}_1{f}_{c}x(h_o-\frac{x}{2})+{f_y}^{\′}{A_s}^{\′}(h_o-a^{\′})---\left(1\right)$

Concrete compression district height x determines as the following formula:

α₁f_cX=f_yA_s-f_y′A_s′ (2)

The moment-curvature relationship of M wall section in formula；

α₁Coefficient, devises a stratagem according to " Code for design of concrete structures " (GB50010) 6.2.6 rules and regulations Calculate；

f_cConcrete axial compressive strength design load；

A_s、A_s' tensile region, the area of section of compressive region longitudinal reinforcement；

h_oEffective depth of section；

A, a ' tensile region, compressive region longitudinal reinforcement Resultant force to tension, the distance at pressurized edge.

f_y、f_y' tensile region, the tensile strength design load of compressive region longitudinal reinforcement.

2) the flexure checking of bearing capacity of supporting leg section

$M_l\≤{\mathrm{\α}}_1{f}_c{b}_{l}x(h_o-\frac{x}{2})+{f_y}^{\′}{A_s}^{\′}(h_o-a^{\′})---\left(3\right)$

M in formula_lThe moment-curvature relationship of supporting leg section；

b_lThe width of supporting leg.

3) wall section Shear checking of bearing capacity

$V_{cs}\≤0.7f_t{h}_o+f_{yh}\frac{A_{sh}}{s}{h}_o---\left(4\right)$

V in formula_csThe shearing force design value of wall section；

f_tConcrete axial tensile strength design load；

f_yhThe tensile strength design load of wall section horizontal reinforcement；

A_shConfigure the gross section area of horizontal steel bar in same interface；

S is along the horizontal bar spacing of subterranean wall length direction.

4) supporting leg section Shear checking of bearing capacity

$V_{lcs}\≤0.7f_t{b}_l{h}_o+f_{lyh}\frac{A_{lsh}}{s_l}{h}_o---\left(5\right)$

V in formula_lcsThe concrete of supporting leg and the shear resistance capacity design load of horizontal bar；

f_lyhThe tensile strength design load of supporting leg stirrup；

A_lshIt is arranged in the gross section area of each limb of supporting leg stirrup in same cross section；

s_lSupporting leg stirrup is along the spacing of supporting leg length direction.

Claims (1)

1. band supporting leg diaphram wall computational methods under horizontal loads, it is characterised in that the method include as Lower step:

Step 1, use elastic foundation method finite element program, carry out the internal force of diaphram wall, deformation and Stability analysis, obtains underground diaphragm wall inner force, deforms the relation curve with the degree of depth, and determine suitable underground Diaphragm wall thickness, this diaphram wall thickness is band supporting leg underground continuous wall section thickness；

The reasonable judgement of step 2, number of legs, size and the degree of depth:

(1) tentatively draft number of legs, sectional dimension under wall section, obtain the stiffness ratio r of wall section and supporting leg_I、 The level of supporting leg is to bearing capacity f_l, including bending resistance and shear-carrying capacity；

(2) underground diaphragm wall inner force that obtains according to step 1, deformation are with the relation curve of the degree of depth, at base The descending branch scope of the hole following internal force in the end, determines interior force value F=f_l/r_IThe corresponding degree of depth；This degree of depth of preliminary judgement For the interface location of wall section Yu supporting leg, the namely position on supporting leg top；

(3) band supporting leg diaphram wall sectional dimension, wall section and supporting leg depth parameter are preliminarily formed；

Step 3, improvement elastic foundation method finite element program, arrange variation rigidity switch so that supporting leg Duan Fan Enclose beam on elastic foundation rigidity=wall segment limit beam on elastic foundation rigidity/r_I, thus form variation rigidity beam on elastic foundation Method finite element program；Use variation rigidity elastic foundation method finite element program, carry out carrying under horizontal loads The internal force of supporting leg diaphram wall and deformation Check checking computations, enter the position of supporting leg interface, the internal force of supporting leg Row is checked；

Step 4, when calculated supporting leg internal force more than the level of supporting leg to bearing capacity f_lTime, reduce supporting leg Interface location；Return step 3, recalculate, until the internal force of supporting leg meet its level to bearing capacity and The deformation requirements of surrounding enviroment；

Step 5, internal force according to the band supporting leg diaphram wall determined, carry out wall section and the arrangement of reinforcement of supporting leg section Design calculates, wall section and supporting leg section Bend, Shear checking of bearing capacity；Wherein wall section and Lower limb section Bend, Shear checking of bearing capacity formula are as follows:

1) wall section unit width Bend checking of bearing capacity:

$M\≤{\mathrm{\α}}_1{f}_{c}x(h_o-\frac{x}{2})+{f_y}^{\′}{A_s}^{\′}(h_o-a^{\′})$

Concrete compression district height x determines as the following formula:

α₁f_cX=f_yA_s-f_y'A_s'

In formula, M represents the moment-curvature relationship of wall section；α₁Represent coefficient, according to " Code for design of concrete structures " GB50010 6.2.6 rules and regulations devise a stratagem is calculated；f_cRepresent concrete axial compressive strength design load；A_sRepresent tension The area of section of district's longitudinal reinforcement；A_s' represent the area of section of compressive region longitudinal reinforcement；h_oRepresent that cross section is effective Highly；A represents that tensile region longitudinal reinforcement Resultant force is to the distance at tension edge；A' represents compressive region longitudinal reinforcement Resultant force is to the distance at pressurized edge；f_yRepresent the tensile strength design load of tensile region longitudinal reinforcement, f_y' represent The tensile strength design load of compressive region longitudinal reinforcement；

2) the Bend checking of bearing capacity of supporting leg section:

$M_l\≤{\mathrm{\α}}_1{f}_c{b}_{l}x(h_o-\frac{x}{2})+{f_y}^{\′}{A_s}^{\′}(h_o-a^{\′})$

M in formula_lRepresent the moment-curvature relationship of supporting leg section；b_lRepresent the width of supporting leg；

3) wall section Shear checking of bearing capacity:

$V_{cs}\≤0.7f_t{h}_o+f_{yh}\frac{A_{sh}}{s}{h}_o$

V in formula_csRepresent the shearing force design value of wall section；f_tRepresent concrete axial tensile strength design load；f_yhRepresent wall The tensile strength design load of section horizontal reinforcement；A_shThe gross section of horizontal steel bar in the same interface of expression configuration Area；S represents the horizontal bar spacing along subterranean wall length direction；

4) supporting leg section Shear checking of bearing capacity:

$V_{lcs}\≤0.7f_t{b}_l{h}_o+f_{lyh}\frac{A_{lsh}}{s_l}{h}_o$

V in formula_lcsRepresent concrete and the shear resistance capacity design load of horizontal bar of supporting leg；f_lyhRepresent the anti-of supporting leg stirrup Tensile strength design load；A_lshRepresent and be arranged in the gross section area of each limb of supporting leg stirrup in same cross section；s_lTable Show the supporting leg stirrup spacing along supporting leg length direction.