CN104164869B - Band supporting leg diaphram wall Computing Method for Vertical Bearing Capacity - Google Patents

Abstract

The present invention relates to a kind of band supporting leg ground diaphragm wall Computing Method for Vertical Bearing Capacity. First the present invention is with supporting leg diaphram wall bearing capacity composition analysis; Secondly determine the bearing capacity of supporting leg and the bearing capacity of wall section, thereby obtain being with supporting leg diaphram wall bearing capacity; Then to the vertical bearing capacity checking computations of band supporting leg diaphram wall and the checking computations of supporting leg vertical bearing capacity; Finally obtain being with supporting leg diaphram wall vertical bearing capacity. The present invention, without carrying out special geotechnical engineering investigation, can adapt to the widespread adoption of engineering.

Description

Band supporting leg diaphram wall Computing Method for Vertical Bearing Capacity

Technical field

The invention belongs to Geotechnical Engineering in civil engineering, base pit engineering field, be generally used for buildings or structures basement or underground structure.

Background technology

Expand with city size, automobile pollution increases, and basement in high rise building is deepened day by day, and the exploration of road to underground development carried out in each big city one after another, and underground space development and construction are like a raging fire. In the underground space process of construction that area and the degree of depth continue to increase, dark, thick Diaphragm Wall is widely applied, but also has following problem at present:

1, mainly as basement exterior enclosure wall, do not consider to bear agent structure vertical load.

2,, need be taking basement rock as supporting course time, difficulty of construction when diaphram wall enters rock and construction costs increase.

Being the innovation according to specific soil condition, specific use function and to diaphram wall with supporting leg diaphram wall, is special diaphram wall. Diaphram wall bottom arranges after supporting leg, because supporting leg enters the good supporting course in bottom or basement rock, can double as engineering pile, bring into play its end and make use, finally make to be with supporting leg diaphram wall can bear agent structure vertical load, reduce the difficulty of construction that diaphram wall enters rock simultaneously, reduce construction costs.

Band supporting leg diaphram wall is born after vertical load, can reduce engineering pile, solves body of wall and enters rock difficulty and the high problem of cost. Compare society and remarkable in economical benefits with common diaphram wall.

Be not with at present the correlative study of supporting leg diaphram wall and report abroad, domestic only Guangdong Province is as far back as having carried out at the end of last century the similar Construction practices with supporting leg diaphram wall, scale of the project is little, force and deformation characteristic, the scope of application etc. with supporting leg diaphram wall is not carried out to system practice and theoretical research.

Band supporting leg diaphram wall is Novel underground diaphragm wall form, and national standard does not have corresponding method for designing at present. Existing pile foundation formula is applicable to circle stake or the square pile in single cross section, can not reflect that the supporting course at wall section and supporting leg place is inconsistent, the different situation of wall section and supporting leg end loading end.

Summary of the invention

For making project planner according to existing engineering prospecting data and data, determine the vertical bearing capacity with supporting leg diaphram wall, the each layer soil body frictional force and the characteristic load bearing capacity that provide according to engineering investigation report are provided, determine the computational methods with supporting leg diaphram wall vertical bearing capacity, the present invention includes:

Step 1: band supporting leg diaphram wall bearing capacity composition analysis.

Step 2: determine the Bearing Capacity Formula of supporting leg, calculate supporting leg vertical bearing capacity.

Step 3: determine the Bearing Capacity Formula of wall section, calculate wall section vertical bearing capacity.

Step 4: by step 2 and step 3, calculate band supporting leg diaphram wall bearing capacity.

Step 5: band supporting leg diaphram wall vertical bearing capacity checking computations.

Step 6: supporting leg vertical bearing capacity checking computations.

Step 7: after step 5, step 6 checking computations, finally obtain being with supporting leg diaphram wall vertical bearing capacity.

Beneficial effect of the present invention:

1, can jointly bring into play the end resistance with supporting leg underground continuous wall section and supporting leg, improve the vertical bearing capacity with supporting leg diaphram wall.

2, provide with vertical bearing capacity compute classes like be with supporting leg diaphram wall vertical bearing capacity computing formula, facilitate designer to apply, simple and easy to do.

3, band supporting leg diaphram wall self strength condition is taken into account, clearly needed the vertical bearing capacity checking computations with supporting leg underground continuous wall section and supporting leg, guarantee to meet with supporting leg diaphram wall self intensity the requirement of vertical load pressurized.

Though 4, band supporting leg diaphram wall is special-shaped diaphram wall, but determine its bearing capacity by these computational methods, need the characteristic value of foundation bearing capacity data of foundation and the data qualification of existing national Specification consistent, without carrying out special geotechnical engineering investigation, can adapt to the widespread adoption of engineering.

Brief description of the drawings

Fig. 1 a, Fig. 1 b and Fig. 1 c are respectively band supporting leg diaphram wall vertical bearing capacity stereogram, front view and side view (as engineering pile);

Fig. 2 a, Fig. 2 b and Fig. 2 c are respectively band supporting leg diaphram wall vertical bearing capacity stereogram, front view and side view (as outer wall of basement);

Checking of bearing capacity figure when Fig. 3 a, Fig. 3 b and Fig. 3 c are respectively band supporting leg diaphram wall as outer wall of basement, as engineering pile and supporting leg.

Detailed description of the invention

Below in conjunction with accompanying drawing, embodiments of the invention are elaborated: the present embodiment is implemented under taking technical solution of the present invention as prerequisite, provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

When band supporting leg diaphram wall bears superstructure load, be equivalent to basis, its vertical bearing capacity comprises two-layer connotation: the ultimate bearing capacity of the foundation soil with supporting leg diaphram wall self bearing capacity, supporting strap supporting leg ground continuous wall base. The latter is also referred to as the vertical bearing capacity with supporting leg diaphram wall. The invention provides the complete Computing Method for Vertical Bearing Capacity with supporting leg diaphram wall, supporting leg, band supporting leg underground continuous wall section, supporting leg self checking of bearing capacity formula, thereby final definite band supporting leg diaphram wall bearing capacity.

For achieving the above object, the present invention takes following step:

Step 1: band supporting leg diaphram wall bearing capacity composition analysis. Compare with common diaphram wall, band supporting leg diaphram wall has increased supporting leg collateral resistance, supporting leg end resistance two parts vertical bearing capacity. Be that its vertical bearing capacity is by wall section vertical bearing capacity (side friction q_sw1、q_sw2With end resistance q_pw) and supporting leg vertical bearing capacity composition (side friction q_sl1、q_sl2With end resistance q_pl). While being with supporting leg diaphram wall as vertical load-carrying members, supporting leg performance end is made use. Its vertical bearer properties is similar to friction end-bearing pile. For performance wall section and the effect of leg ends end resistance, should make wall section and supporting leg enter better supporting course.

Band supporting leg diaphram wall, as vertical load-carrying members, divides following two kinds of situations:

(1) as engineering pile, bear the load of skyscraper superstructure, referring to Fig. 1 a, Fig. 1 b and Fig. 1 c.

(2) bear superstructure load, as outer wall of basement. Because being with supporting leg underground continuous wall section width and width to join between two, between wall width, be reduced to zero without vertical displacement is poor, wall both end sides frictional resistance q_sw1Be zero. In basement construction process, excavation, causes and meets above native side wall body region soil body lateral confinement at the bottom of foundation ditch and weaken; For being partial to safety, basement scope body of wall side friction q_sw2Also be taken as zero, referring to Fig. 2 a, Fig. 2 b and Fig. 2 c

Step 2: determine supporting leg vertical bearing capacity R_lFormula, for:

R_l＝(Q_sl+Q_pl)/K(1a)

Wherein supporting leg collateral resistance: Q_sl＝n(α·2t∑q_sl1il_i+2b_l∑q_sl2il_i)(1b)

Supporting leg end resistance: Q_pl＝q_plA_l；A_l＝nb_l·t(1c)

In formula: α---supporting leg is along the long side frictional resistance reduction coefficient of wall, desirable 0.8～0.9;

A_l---the projected area (m of supporting leg²)；

l_i---the thickness (m) of i layer soil;

b_l, t---width and the thickness (m) of supporting leg;

N---the quantity of supporting leg (m) under wall section.

Step 3: determine wall section vertical bearing capacity R_wFormula, for:

R_w＝(Q_sw+Q_pw)/K(2a)

Wherein, wall collateral resistance: Q_sw＝2t∑q_sw1l_i+2b∑q_sw2l_i(2b)

Wall end resistance: Q_pw＝q_sp(A_w-A_l)；A_w＝bt(2c)

In formula: A_W---the projected area (m of wall section²)；

The width of b, t---wall section and thickness (m);

q_sp＝q_pw。

Step 4: determine band supporting leg diaphram wall bearing capacity R formula, calculate band supporting leg diaphram wall bearing capacity.

R＝R_w+R_l(3)

q_sw1、q_sw2、q_pw、q_s1、q_sl2And q_plProvided by engineering investigation report, in the time that band supporting leg diaphram wall doubles as outer wall of basement, q_sw1Value gets 0, and basement depth bounds wall section surrounding side friction q_sw1、q_sw2Be 0. In formula (1) and formula (2), K is safety coefficient, consistent with national standard bearing capacity of pile foundation safety requirements, gets K=2. According to band supporting leg diaphram wall size, by formula (3), can calculate band supporting leg diaphram wall vertical bearing capacity.

Step 5: band supporting leg underground continuous wall section vertical bearing capacity checking computations. The suffered superstructure vertical load of wall section P need meet following formula requirement:

P≤R'＝φ_cf_cA_w+0.9f_y'A_s'(4)

φ in formula_c---become wall service factor, same to cast-in-situ bored pile, desirable 0.7～0.8.

f_c---concrete axle center compression strength design load;

f_y'---lengthways main steel bar compression strength design load;

A_s'---lengthways main steel bar area of section.

Step 6: the supporting leg vertical bearing capacity checking computations with supporting leg diaphram wall, see Fig. 3 a, Fig. 3 b and figure c. The suffered vertical load N in supporting leg top is:

$N=\frac{P+G-(Q_{\mathrm{sw}}+Q_{\mathrm{pw}})/K}{n}---\left(5\right)$

G in formula---the basement vertical load that the above wall section deadweight in supporting leg top and wall section are shared; When as engineering pile, be the above wall section deadweight in supporting leg top.

Supporting leg top vertical load need meet following requirement:

N≤φ_lcf_cA_l+0.9f_y'A_s'(6)

φ in formula_lc---the service factor of supporting leg moulding, same to cast-in-situ bored pile, desirable 0.7～0.8.

Step 7: after step 5, step 6 checking computations, meeting under the condition of supporting leg self vertical bearing capacity formula (6), the minimum of a value of modus ponens (3) R and formula (4) R', this value is the final vertical bearing capacity of band supporting leg diaphram wall.

Claims (7)

1. band supporting leg diaphram wall Computing Method for Vertical Bearing Capacity, is characterized in that the method comprises following stepRapid:

Step 1: band supporting leg diaphram wall bearing capacity composition analysis;

Step 2: determine the Bearing Capacity Formula of supporting leg, calculate supporting leg vertical bearing capacity;

Step 3: determine the Bearing Capacity Formula of wall section, calculate wall section vertical bearing capacity;

Step 4: supporting leg vertical bearing capacity and wall section vertical bearing capacity are added, calculate band supporting leg underground continuouslyWall bearing capacity;

Step 5: band supporting leg diaphram wall vertical bearing capacity checking computations;

Step 6: supporting leg vertical bearing capacity checking computations;

Step 7: after step 5, step 6 checking computations, finally obtain being with supporting leg diaphram wall vertically to carryPower.

2. band supporting leg diaphram wall Computing Method for Vertical Bearing Capacity according to claim 1, its feature existsIn: bearing capacity described in step 1 is made up of wall section and supporting leg vertical bearing capacity; Wherein wall section vertical bearing capacity bagDraw together both end sides frictional resistance q_sw1, wall both sides side friction q_sw2, wall bottom end resistance q_pw; Supporting leg vertical bearing capacityComprise supporting leg side friction q along its length_sl1, through-thickness supporting leg side friction q_sl2, supporting leg end resistancePower q_pl。

3. band supporting leg diaphram wall Computing Method for Vertical Bearing Capacity according to claim 2, its feature existsIn: supporting leg vertical bearing capacity R_lCircular is:

R_l＝(Q_sl+Q_pl)/K

Q_sl＝n(α·2tΣq_sl1l_i+2b_lΣq_sl2l_i)

Q_pl＝q_plA_l；A_l＝nb_l·t

In formula, α is that supporting leg is along the long side frictional resistance reduction coefficient of wall; A_lFor the projected area of supporting leg; l_iBe i layer soilThickness; b_lFor the width of supporting leg; T is the thickness of supporting leg; N is the quantity of supporting leg under wall section; K is safety systemNumber.

4. band supporting leg diaphram wall Computing Method for Vertical Bearing Capacity according to claim 2, its featureBe: wall section vertical bearing capacity R_wCircular is:

R_w＝(Q_sw+Q_pw)/K

Q_sw＝2tΣq_sw1l_i+2bΣq_sw2l_i

Q_pw＝q_sp(A_w-A_l)；A_w＝bt

A in formula_WFor the projected area of wall section; B is the width of wall section; T is the thickness of wall section; A_lFor the projection of supporting legArea, K is safety coefficient, l_iBe the thickness of i layer soil, Q_swFor wall collateral resistance, Q_pwFor wall end resistance,q_spFor wall section end resistance.

5. according to the band supporting leg diaphram wall Computing Method for Vertical Bearing Capacity described in claim 3 or 4, itsBe characterised in that: the checking computations in step 5 specifically: the suffered superstructure vertical load of wall section P need meet:

P≤R'＝φ_cf_cA_w+0.9f_y'A_s'

In formula, R' is wall section intensity; φ_cFor becoming wall service factor; f_cFor concrete axle center compression strength design load;f_y' be lengthways main steel bar compression strength design load; A_s' be lengthways main steel bar area of section, A_WFor the perspective plane of wall sectionLong-pending.

6. according to the band supporting leg diaphram wall Computing Method for Vertical Bearing Capacity described in claim 3 or 4, itsBe characterised in that: the checking computations in step 6 specifically:

Supporting leg top vertical load N need meet following requirement:

N≤φ_lcf_cA_l+0.9f_y'A_s'

$N=\frac{P+G-(Q_{sw}+Q_{pw})/K}{n}$

φ in formula_lcFor the service factor of supporting leg moulding, f_cFor concrete axle center compression strength design load; f_y' for verticalTo main muscle compression strength design load; A_s' be lengthways main steel bar area of section; G is the above wall section deadweight in supporting leg topAnd the basement vertical load shared of wall section; When as engineering pile, be the above wall section in supporting leg top certainlyHeavy, P is the suffered superstructure vertical load of wall section, Q_swFor wall collateral resistance, Q_pwFor wall end resistance.

7. band supporting leg diaphram wall Computing Method for Vertical Bearing Capacity according to claim 5, its featureBe: step 7 specifically: meeting under the vertical load requirement of supporting leg top, getting band supporting leg diaphram wallMinimum of a value in bearing capacity and R', this minimum of a value is the final vertical bearing capacity of band supporting leg diaphram wall.