CN-121980639-A - Support rigidity reduction determination method considering structural form deviation of circular ring beam

CN121980639ACN 121980639 ACN121980639 ACN 121980639ACN-121980639-A

Abstract

The invention provides a method for determining support rigidity reduction by considering the structural form deviation of a circular ring beam, which comprises the following steps of S1, ideal support rigidity of a standard circular ring beam, S2, form deviation and simulation characterization of the circular ring beam structure, S3, building a circular ring beam structural form deviation model and calculating a support rigidity reduction coefficient, S4, building a mathematical model of the support rigidity reduction coefficient by considering the structural form deviation of the circular ring beam, S5, substituting the measured circular structural form deviation value in an actual engineering into the mathematical model of the support rigidity reduction coefficient to calculate the support rigidity reduction coefficient, and then accurately estimating the actual support rigidity of a structure with the form deviation in practice by combining the ideal support rigidity of the standard circular ring beam structure. The invention unifies the rigidity reduction coefficient of the circular structure corresponding to the DeltaR/R 2 , improves the calculation accuracy of the circular foundation pit supporting structure, and ensures the accurate control and safety of the foundation pit supporting under the condition of construction error deformation.

Inventors

CHEN CHUNHONG
FAN ZHIQIANG
ZHOU QIHUI
JING ZIJING
YANG FEI
SHEN HUAWEI
WANG HENGLE
REN XIANG

Assignees

中国电建集团华东勘测设计研究院有限公司

Dates

Publication Date: 20260505
Application Date: 20251210

Claims (10)

1. A method for determining the reduction of the supporting rigidity by considering the structural form deviation of a circular ring beam is characterized by comprising the following steps: S1, ideal supporting rigidity of a standard circular ring beam, wherein ideal supporting rigidity K of the standard circular structure is directly obtained by standard size and material mechanical parameters of the standard circular structure, and is the ratio of uniformly distributed annular pressure P to radial deformation increment dR, namely: S2, simulating and representing the shape deviation of the circular ring beam structure by adopting an elliptical structure, namely, the circular structure in engineering deforms and then is led to develop towards the elliptical structure, wherein the minor axis in the ellipse is R 0 , the major axis R 1 is the main direction of the shape deviation in engineering operation, and the supporting rigidity of a structural boundary point C corresponding to the minor axis R 0 is weakened compared with that of a standard circular ring beam structure under the condition of original non-shape deviation; S3, building a circular ring beam structure form deviation model and calculating a supporting rigidity reduction coefficient, namely adopting a MIDAS GEN two-dimensional rod model to make an elliptical structure simulating the circular ring beam structure form deviation equivalent to a polygonal structure formed by a plurality of rods, adopting elasticity to support soil around the simulated structure, and applying uniform confining pressure P 0 of the soil around the structure to perform structure stress deformation calculation; S4, establishing a mathematical model of the support rigidity reduction coefficient considering the form deviation of the circular ring beam structure, namely adopting a MIDAS GEN two-dimensional rod model to simulate and calculate the support rigidity reduction coefficient alpha under the conditions of different original standard circular ring beam structure radiuses R and different form deviations delta R, and carrying out mathematical fitting of the support rigidity reduction coefficient alpha with respect to the form deviation characteristic index delta R/R 2 to obtain the mathematical model of the support rigidity reduction coefficient considering the form deviation of the circular ring beam structure; s5, substituting the measured form deviation value delta R/R 2 of the circular structure in the actual engineering into a support rigidity reduction coefficient mathematical model to calculate a support rigidity reduction coefficient alpha, and then accurately estimating the actual support rigidity K' R of the structure with the form deviation in practice by combining the ideal support rigidity K of the standard circular ring beam structure.
2. The method of claim 1, wherein in the step S1, the radial deformation increment dR of the standard circular ring beam structure is a radius increment of the standard circular ring beam structure after the whole uniform deformation under the action of uniform radial confining pressure, namely, the standard radius of the standard circular ring beam structure is recorded as R, the standard radius of the standard circular ring beam structure after the whole uniform deformation is changed to R ', dR=R-R', the circumferential perimeter increment of the standard circular ring beam structure after the whole uniform deformation is s=2pi R-2pi R '=2pi R epsilon, wherein epsilon is the circumferential strain of the structure, the strain of the standard circular ring beam structure under the action of the circumferential pressure can be expressed as epsilon=N/EA, wherein N is the circumferential compressive stress of the standard circular ring beam structure under the action of uniform radial confining pressure P 0 , E is the deformation modulus of the standard circular ring beam structure, and A is the cross section area of the standard circular ring beam structure=R-R' =RN/EA.
3. The method of claim 1, wherein in step S1, the standard circular ring beam structure is subjected to stress analysis by selecting a micro unit dθ, and the standard circular ring beam structure generates a hoop compressive stress N under the action of the uniform radial confining pressure P 0 , namely the hoop supporting axial force of the standard circular ring beam structure, so as to obtain the relationship between the uniform radial confining pressure P 0 and the hoop compressive stress N Under the condition of extreme differential Therefore, the relationship between the circumferential support axial force N and the uniform confining pressure P 0 is n=p 0 R.
4. The method of claim 1, wherein the desired support stiffness of the standard circular ring beam structure in step S1 is Combining dr=r-R' =rn/EA and n=p 0 R, yields the ideal support stiffness for a standard circular ring beam structure
5. The method of claim 1, wherein in the step S3, the calculated deformation of the structural boundary point C corresponding to the elliptical short axis R 0 is obtained to be delta, and the unit width equivalent supporting rigidity K ' R ＝P 0 /delta of the point C is obtained, wherein the value is the actual supporting rigidity considering the structural form deviation of the circular ring beam, K ' R is reduced compared with the supporting rigidity K of the standard circular ring beam, the introduced supporting rigidity reducing coefficient is marked as alpha, the supporting rigidity K ' R considering the structural form deviation of the circular ring beam is K ' R =alpha K which is reduced on the basis of the supporting rigidity K of the standard circular ring beam, and the supporting rigidity reducing coefficient alpha=K ' R /K is calculated.
6. The method of claim 1, wherein in the steps S3 and S4, the step of calculating the two-dimensional bar model by using the MIDAS GEN is as follows: 1) Inputting R 0 、R 1 of an elliptical structure, the edge number of the structural rod piece and the parameters of the structural rod piece; 2) Inputting the peripheral confining pressure P 0 of the circular ring beam structure; 3) Calculating, and extracting a C point to calculate deformation delta; 4) The steps are repeated with different radii and form deviation values.
7. The method according to claim 1, wherein in the steps S3 and S4, the radii R 0 are 8m, 10m, 12m, 14m, 16m, 18m, 20m, 22m, 24m, 26m, 28m, 30m, 32m, 34m and 36m, respectively, and the radii R 1 -R 0 are 0m, 0.05m, 0.1m and 0.2m, respectively, for each R 0 , and the support stiffness reduction coefficient alpha under the conditions of different radii and different form deviations is calculated.
8. The method according to claim 1, wherein in the step S4, the support stiffness reduction coefficient α is directly related to the morphological deviation characteristic index ΔR/R 2 , and if ΔR/R 2 is the same under the condition of different radii R, the stiffness reduction coefficient is substantially the same, and the relationship between the support stiffness reduction coefficient α and ΔR/R 2 is expressed by adopting a double exponential decay model or a tensile exponential function, so that the following results are obtained: double exponential decay model: y=0.65 e -1450x +0.72e -50X +0.35 Tensile index model: wherein x is a morphological deviation characteristic index delta R/R 2 , and y is a rigidity reduction coefficient.
9. The method according to claim 8, wherein when the morphological deviation feature index DeltaR/R 2 is smaller than 0.002, the expression is performed by adopting a double-exponential decay model or a tensile exponential function pair, so as to obtain: double exponential decay model: y=0.65 e -1450x +0.35 Tensile index model: wherein x is a morphological deviation characteristic index delta R/R 2 , and y is a rigidity reduction coefficient.
10. The method of claim 1, wherein the support stiffness reduction coefficient α is further integrated with the mathematical model of the support stiffness reduction coefficient obtained in step S4 and engineering experience, and α is 0.5-0.8 when the form deviation ΔR/R 2 is small and 0.9 when the radius R is greater than 36m, respectively.

Description

Support rigidity reduction determination method considering structural form deviation of circular ring beam Technical Field The invention belongs to the field of foundation pit engineering design calculation, and particularly relates to a method for determining support rigidity reduction by considering structural form deviation of a circular ring beam. Background Because the round structure has good arch effect, many foundation pits are constructed into a round support system by the diaphragm wall. The circular ring beam structure is used as a supporting system of the foundation pit, under the action of external water and soil pressure loads, circular arch effect can fully exert the circumferential bearing capacity of the underground continuous wall, reduce the vertical bending moment of the underground continuous wall and the internal force of the circular ring beam support, improve the self stability of the ultra-deep foundation pit, improve the integral rigidity of the enclosure structure, reduce the deformation of the foundation pit and reduce the internal force of the enclosure structure, and is an economic and reasonable underground space structure form. The supporting rigidity of the circular structure is an important parameter in foundation pit calculation, and the calculated rigidity value is important to deformation, internal structural force, reinforcement and the like of the foundation pit. The highway bridge foundation and foundation design specification (JTG 3363-2019) recommends that the supporting rigidity of the circular ring beam structure directly adopts a calculation formula of a theoretical ring, the circular ground wall structure adopts an equivalent distribution elastic coefficient of a wall body with unit width and corrects the equivalent distribution elastic coefficient, and the correction coefficient is 0.4-0.7. However, certain errors exist in the construction of the circular structure, such as 20mm of cross section deviation of the support ring beam, 30mm of support axis deviation, 1/1000 of support flexibility and the like are allowed in the conventional design. Along with excavation of foundation ditch, bearing structure also can take place certain deformation and displacement, and circular bearing structure includes that circular ground even wall structure is not theoretical circular, therefore the calculation formula based on theoretical ring alone in the prior art evaluates actual circular ring beam structure's support rigidity not accurate. How to select a scientific and practical rigidity reduction calculation method to quantitatively calculate the supporting rigidity of the circular ring beam supporting structure is a technical problem which is not yet known in the engineering industry. Disclosure of Invention The main object of the present invention is to provide a method for determining the reduction of the supporting rigidity taking into account the structural form deviation of a circular ring beam, in view of the above-mentioned problems. For this purpose, the above object of the present invention is achieved by the following technical solutions: A method for determining the reduction of the supporting rigidity by considering the structural form deviation of a circular ring beam comprises the following steps: s1, ideal supporting rigidity of a standard circular ring beam, wherein ideal supporting rigidity K of the standard circular structure can be directly obtained by standard size and material mechanical parameters of the standard circular structure, and is the ratio of uniformly distributed annular pressure P to radial deformation increment dR, namely: S2, simulating and representing the shape deviation of the circular ring beam structure by adopting an elliptical structure, namely, the circular structure in engineering deforms and then is led to develop towards the elliptical structure, wherein the minor axis in the ellipse is R 0, the major axis R 1 is the main direction of the shape deviation in engineering operation, and the supporting rigidity of a structural boundary point C corresponding to the minor axis R 0 is weakened compared with that of a standard circular ring beam structure under the condition of original non-shape deviation; S3, building a circular ring beam structure form deviation model and calculating a supporting rigidity reduction coefficient, namely adopting a MIDAS GEN two-dimensional rod model to make an elliptical structure simulating the circular ring beam structure form deviation equivalent to a polygonal structure formed by a plurality of rods, adopting elasticity to support soil around the simulated structure, and applying uniform confining pressure P 0 of the soil around the structure to perform structure stress deformation calculation; S4, establishing a mathematical model of the support rigidity reduction coefficient considering the form deviation of the circular ring beam structure, namely adopting a MIDAS GEN two-dimensional rod mo