Single-chamber grating type underground diaphragm wall foundation p-y curve calculation method

Abstract

The invention discloses a method for calculating a p-y curve of a single-chamber grating type underground diaphragm wall foundation. The method mainly comprises the following steps of: respectively determining wall body and soil body parameters of the single-chamber type grating type underground diaphragm wall based on the structural characteristics of the grating type underground diaphragm wall foundation, establishing a mutual stress model of the underground diaphragm wall foundation and the soil body, applying a static load, extracting a soil body stress value and a wall body displacement value, normalizing and integrating the extracted data, and obtaining a single-chamber type grating type underground diaphragm wall foundation model. Calculating ultimate soil counter-force in clay and sandy soil and initial foundation counter-force modulus in the sandy soil, fitting data by adopting a hyperbolic tangent function, and finally respectively establishing a p-y curve method suitable for analyzing the horizontal stress of the single-chamber grating type underground diaphragm wall foundation in the cohesive soil foundation and the sandy soil foundation. The horizontal static load response of the foundation can be effectively predicted and simulated, and important guidance can be provided for engineering design and construction of the grating type underground diaphragm wall.

Description

Technical Field

[0001] The invention relates to the technical field of foundation engineering, and in particular to a py curve method of a single-chamber grid-type underground continuous wall foundation. Background Art

[0002] The grid-type underground continuous wall foundation refers to a foundation form in which adjacent underground continuous wall bodies are connected by rigid joints to form a closed rectangular frame with a top plate (cap). Due to the mechanized and rapid construction, the underground continuous wall foundation has high efficiency, low cost, wide application range of foundation, and low noise. The strong rigidity and good compactness with the foundation also make the underground continuous wall foundation particularly suitable for large-span deep-water bridges. In my country, with the maturity and advancement of construction technology, the application of grid-type ground-connected walls in large bridge foundations is increasing (such as: Runyang Bridge, Wuhan Yangluo Bridge, Zhangjinggao Yangtze River Bridge, Kahalo Jinsha River Bridge, etc.), and there is a trend of replacing caisson foundations and pile foundations in ultra-deep and ultra-large foundations.

[0003] At present, the calculation of horizontal load response of grid-type underground continuous wall foundation is relatively lacking, but the horizontal force calculation of pile foundation as deep foundation includes M method, K method and PY curve method. Among these methods, PY curve method can construct the relationship between the reaction force of soil around the foundation and the foundation displacement, and assumes the soil action as a series of discrete nonlinear soil springs, so it can better simulate the nonlinear changes of soil. Based on the PY curve method, the present invention innovatively proposes a single-chamber grid-type underground continuous wall foundation horizontal force response analysis method, which can be used for the design and construction reference of single-chamber grid-type ground-connected wall foundation. Summary of the invention

[0004] In view of the above-mentioned gaps in the prior art, the purpose of the present invention is to provide a simple, accurate and fast py curve method for single-chamber grid-type underground continuous wall foundation, so as to solve the deficiency of the prior art in the research on the calculation of horizontal force displacement and soil pressure of grid-type underground continuous wall.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a single-chamber grid-type underground continuous wall foundation py curve calculation method, comprising the following steps:

[0006] S1. Determine the geometric dimensions, material strength and stiffness parameters of the grid-type underground continuous wall foundation required for calculation;

[0007] S2. Determine the strength and stiffness parameters of clay soil and sandy soil foundation required for calculation respectively;

[0008] S3. Based on the numerical model of grid-type diaphragm wall foundation in clay and sand, loads are applied step by step on the side of the foundation slab to extract and calculate displacement data and stress data Obtain the ultimate soil reaction force p of two types of soil i,u,c and p i,u,s ;

[0009] S4. Normalize the numerical results of earth pressure of two types of soils respectively, determine the ultimate soil reaction adjustment coefficient α1 and depth influence coefficient α2 of cohesive soil, and calculate the ultimate soil reaction adjustment coefficient α under different B3 sizes by eliminating the dependence on the horizontal section size B3 of the foundation. 1,e and α 2,e , and its calculation parameters β1, β2, β3, β4 and β5, determine the influence factor α3 and depth influence factor α4 of the ultimate soil reaction of sandy soil, and calculate the ultimate soil reaction adjustment coefficient α under different B3 sizes by eliminating the dependence of the foundation horizontal section size B3. 3,e and α 4,e , and its calculation parameters β6, β7, β8 and β9;

[0010] S5. Process the relationship between soil pressure and displacement of sandy soil foundation under small displacement conditions, and determine the depth influence factors α5, α6 and size influence factor α7 of the initial foundation reaction modulus of sandy soil foundation;

[0011] S6. Use hyperbolic tangent function to fit the relationship between displacement and earth pressure of two types of soils;

[0012] S7. Mathematical analysis models are established to predict the interaction response between single-chamber grid-type underground continuous wall foundation and surrounding soil in clay and sand foundations respectively.

[0013] Furthermore, the step S1 is specifically as follows:

[0014] ①Geometric parameters of single-chamber grid-type ground-connected wall foundation

[0015] Including the horizontal cross-sectional dimensions B1, B2, B3, B4 of the single-chamber grid-type underground continuous wall foundation and the wall thickness t w , where B1 is the outer dimension of the foundation section perpendicular to the y-axis, B2 is the inner dimension of the foundation section perpendicular to the y-axis, B3 is the outer dimension of the foundation section perpendicular to the x-axis, and B4 is the inner dimension of the foundation section perpendicular to the x-axis. The horizontal section dimensions need to meet the structural requirements. The outer dimension B1 of the single-chamber grid-type underground continuous wall foundation perpendicular to the y-axis is generally not more than 9.0m, and the outer dimension B3 perpendicular to the x-axis is generally not more than 12.0m. The wall thickness t w Usually 0.6-1.2m:

[0016] B1≤9.0 (1)

[0017] B3≤12.0 (2)

[0018] t w=0.6-1.2 (3)

[0019] B1-B2=B3-B4=2t w (4)

[0020] Including the vertical cross-sectional dimensions of the single-chamber grid-type underground continuous wall foundation and the foundation burial depth L e and the thickness of the cap plate t cap ;

[0021] ② Single-chamber grid-type ground-connected wall foundation material parameters

[0022] Including elastic modulus E w , Poisson's ratio v w , bulk modulus K w , shear modulus G w and material density ρ w . Elastic modulus E w It is related to the concrete grade used. The Poisson's ratio ν is calculated based on the cube compressive strength value or empirical value according to relevant specifications. w Measured by experiment, if there is no measured data, take ν w =0.2, material density ρ w For ordinary concrete: 2200-2500kg / m 3 , the design usually adopts 2400kg / m 3 , bulk modulus K w and shear modulus G w Calculated by elastic modulus and Poisson's ratio.

[0023] Furthermore, the step S2 is specifically as follows:

[0024] ① Soil properties of clay soil

[0025] Including deformation parameters bulk modulus K c , shear modulus G c , strength parameter internal friction angle and cohesion c c , soil density ρ c and lateral earth pressure coefficient K0. Bulk modulus K c and shear modulus G c The cohesion c is obtained and converted through indoor triaxial test. s and friction angle The data measured by the triaxial test can be used to draw the Mohr circle for calculation. The soil density is obtained by drying in an oven to obtain the dry density of the soil for reference. The lateral earth pressure coefficient is calculated as follows:

[0026]

[0027] in: is the internal friction angle of clay soil;

[0028] ②Sandy soil parameters

[0029] Including deformation parameters bulk modulus K s , shear modulus G s , dilatancy angle ψ, strength parameter internal friction angle and cohesion c s , soil density ρ s and the passive earth pressure coefficient K p . Bulk modulus K s and shear modulus G s The cohesion c is obtained and converted through indoor triaxial test. s and friction angle The Mohr circle can be calculated by using the data measured by the triaxial test. The soil density is obtained by drying in an oven to obtain the dry density of the soil for reference. The passive earth pressure coefficient is calculated as follows:

[0030]

[0031] in: is the internal friction angle of clay soil.

[0032] Furthermore, the step S3 is specifically as follows:

[0033] S31. Extract the normal stress of the soil around the wall at different depths i along the x-axis and tangential stress And calculate the algebraic sum of the initial stresses around the wall

[0034] S32. Divide the target horizontal static load H into n levels. The area of ​​the side area of ​​the foundation slab of the single-chamber ground-connected wall is S = B3t cap Initial load is applied step by step And each level increment is Stress load H′, n=1,2,3……;

[0035] S33, extract the wall displacement at different depths i under load level n and the normal stress of the surrounding soil along the x-axis and tangential stress And calculate the wall circumferential stress increment Calculate Linear Stress Increment

[0036] S34, respectively record the displacement increment of the wall depth i when the load level is n And the linear stress data of the soil around the wall For further data processing;

[0037] S35, repeat steps S32, S33 and S34 until H′=H;

[0038] S36, respectively obtain the ultimate soil reaction force p around the wall of two types of soil at different depths i,u,c and p i,u,s .

[0039] Furthermore, the step S4 is specifically as follows:

[0040] S41. Calculation of the undrained shear strength τ of cohesive soil based on the Mohr-Coulomb elastoplastic constitutive criterion f :

[0041]

[0042] Where: c c is the cohesion of clay soil, is the friction angle of clay soil, γ′ c is the effective weight of clay soil, z is the depth, K0 is the lateral earth pressure coefficient of clay soil, provided by step S2 in claim 1;

[0043] S42, draw N w -z curve, the dimensionless wall side bearing capacity coefficient N is fitted using the following formula w Relationship with depth:

[0044]

[0045] Where: N w is the dimensionless bearing capacity coefficient of the wall side, α1 is the adjustment coefficient of the ultimate soil reaction, and α2 is the depth influence coefficient;

[0046] S43. The calculation method of the ultimate soil reaction force for the single-chamber grid-type underground continuous wall foundation in cohesive soil is constructed based on the ultimate soil reaction force adjustment coefficient α1 and the depth influence coefficient α2:

[0047]

[0048] Where: s u is the undrained shear strength of cohesive soil, obtained through indoor triaxial test or on-site static touch detection. When there is no test data, it can be calculated according to the Mohr-Coulomb criterion by referring to step S41 of claim 5;

[0049] S44. The normalization method is used to process the ultimate soil reaction adjustment coefficient α1 and the depth influence coefficient α2 to eliminate the dependence of the ultimate soil reaction on the cross-sectional size of the ground-connected wall foundation. The ultimate soil reaction adjustment coefficient α1 and the depth influence coefficient α2 affected by different foundation cross-sectional sizes can be obtained by the following formula:

[0050]

[0051] Where: α 1,e The ultimate soil reaction adjustment coefficient when the foundation section size B3 = em, α 2,e is the depth influence coefficient when the basic cross-section size B3 = em, α 2,5 =1.139,α 1,5 =1.545, β1=-0.275, β2=1.266, β3=0.004, β4=1.247, β5=0.996, the value of e is determined by step S1 of claim 1;

[0052] S45. Through the combined calculation of steps S43 and S44, a method for calculating the ultimate soil reaction force at different depths applicable to a single-chamber grid-type underground continuous wall foundation of any cross-sectional size in clay soil is finally obtained:

[0053]

[0054] S46. In order to eliminate the dependence of different cross-sectional dimensions of diaphragm wall foundations in sandy soil foundations, the following power function is used to fit the relationship between the ultimate soil reaction force around the wall and the depth, and a calculation method for the ultimate soil reaction force of a single-chamber grid-type underground continuous wall foundation in sandy soil is established:

[0055]

[0056] Where: K p is the passive earth pressure coefficient of sandy soil, γ′ s is the effective weight of sandy soil, B3 is the outer peripheral dimension of the basic section perpendicular to the x-axis, α3 is the basic section dimension influence coefficient, and α4 is the depth influence coefficient;

[0057] S47. Through data normalization and fitting, the cross-sectional dimension influence coefficient α calculated by different cross-sectional dimensions in the sand foundation is established. 3,e and depth influence coefficient α 4,e as follows:

[0058]

[0059] Where: α 3,e The ultimate soil reaction adjustment coefficient when the foundation section size B3 = em, α 4,e is the depth influence coefficient when the basic cross-section size B3 = em, α 3,5 =1.479,α 4,5 =1.517, β6=0.997, β7=-0.4, β8=0.076, β9=0.924, the value of e is determined by step S1 of claim 1;

[0060] S48. Through the combined calculation of steps S43 and S44, a method for calculating the ultimate soil reaction force at different depths of a single-chamber grid-type underground continuous wall foundation of any cross-sectional size in sandy soil is finally obtained:

[0061]

[0062] Furthermore, the step S5 is specifically as follows:

[0063] S51. Arrange and fit the initial foundation reaction modulus data of different depths with deformation states of wall mud surface displacement in the range of 1.0-2.0 mm, determine the calculation formula of the initial foundation reaction modulus of sand under different cross-sectional sizes and depths of the ground-connected wall foundation, and use the following exponential function to calculate in order to express the relationship between the initial foundation reaction modulus and the depth:

[0064]

[0065] Where: n h It is the initial foundation reaction coefficient related to the relative density of sand. If there is no test data, it can be taken as 1.1-1.3MN / m for loose sand. 3 , medium dense sand takes 3.3-11.0MN / m 3 , compacted sand takes 11.0-23.4MN / m 3 , α5 and α6 are depth influence coefficients, α5 = 0.166, α6 = 0.05 respectively;

[0066] S52. Further, taking the single-chamber grid-type ground-connected wall foundation with B3=5.0m as a reference, the normalized relationship between the initial foundation reaction modulus and the cross-sectional size ratio of different cross-sectional sizes in the sand foundation is established to eliminate the cross-sectional size dependence of the ground-connected wall foundation, and the following function fitting is adopted:

[0067]

[0068] in: is the initial foundation reaction modulus when B3=em, For reference to the initial foundation reaction modulus, different values ​​are taken at different depths. 3,e The basic cross-sectional dimensions are B3 = em, α7 = 0.985;

[0069] S53. Finally, a calculation method for the initial foundation reaction modulus of a single-chamber grid-type underground continuous wall foundation in sandy soil is established:

[0070]

[0071] Furthermore, the step S6 is specifically as follows:

[0072] S61. Establish the relationship between the soil pressure around the cohesive soil wall and the wall displacement, and use the hyperbolic tangent function to fit the best curve:

[0073]

[0074] Where: p is soil reaction force, y is displacement, p i,u,c is the clay limit soil reaction force, provided by step S45 of claim 5, λ1 and λ2 are clay py curve fitting parameters;

[0075] S62. Establish the relationship between the soil pressure around the sandy soil wall and the wall displacement, and use the hyperbolic tangent function to fit:

[0076]

[0077] Where: p is soil reaction force, y is displacement, p i,u,s is the ultimate soil reaction force of sand, provided by step S48 of claim 5, k ini,i is the initial foundation reaction modulus of sand, provided by step S53 of claim 6;

[0078] S63. Using the above hyperbolic tangent function to fit the data, the ultimate soil reaction forces of clay and sand can correspond well. The calculated stiffness of sand is too soft, that is, the initial foundation reaction modulus of sand is too small to varying degrees. The following linear function related to soil depth and foundation section size is used for correction:

[0079]

[0080] in: is the correction function of the initial foundation reaction modulus of sand;

[0081] Furthermore, the step S7 specifically includes establishing the py curves applicable to the horizontal stress of the single-chamber grid-type underground continuous wall foundation in the clay soil and sand soil foundations respectively:

[0082] Clay soil:

[0083] Sandy soil:

[0084] In summary, the beneficial effects of the present invention are:

[0085] (1) It can accurately and efficiently predict the horizontal stress characteristics of a single-chamber grid-type underground continuous wall foundation based on a small amount of soil parameters, which is convenient for designers and construction personnel to use;

[0086] (2) Compared with the large-diameter pile foundation py curve method, it can more accurately reflect the horizontal force characteristics of the single-chamber grid-type underground continuous wall foundation;

[0087] (3) It is not limited to single-chamber grid-type underground continuous wall foundation, but can also provide reference for foundations with soil cores. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 It is a flow chart of a method for calculating the py curve of a single-chamber grid-type underground continuous wall foundation of the present invention;

[0089] Figure 2 It is the calculation model of the grid-type underground continuous wall of the present invention;

[0090] Figure 3 This is a schematic diagram of stress around the wall of the present invention;

[0091] Figure 4 It is a schematic diagram of the py curve method of the present invention. DETAILED DESCRIPTION

[0092] The following is a specific description of the embodiments of the present invention in conjunction with the accompanying drawings to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0093] like Figure 1 As shown, a method for calculating the pull-out displacement of a segmented underground continuous wall foundation includes the following steps:

[0094] S1. Determine the geometric dimensions, material strength and stiffness parameters of the grid-type underground continuous wall foundation required for calculation

[0095] ①Geometric parameters of single-chamber grid-type ground-connected wall foundation

[0096] Including the horizontal cross-sectional dimensions B1, B2, B3, B4 of the single-chamber grid-type underground continuous wall foundation and the wall thickness t w , where B1 is the outer dimension of the foundation section perpendicular to the y-axis, B2 is the inner dimension of the foundation section perpendicular to the y-axis, B3 is the outer dimension of the foundation section perpendicular to the x-axis, and B4 is the inner dimension of the foundation section perpendicular to the x-axis. The horizontal section dimensions need to meet the structural requirements. The outer dimension B1 of the single-chamber grid-type underground continuous wall foundation perpendicular to the y-axis is generally not more than 9.0m, and the outer dimension B3 perpendicular to the x-axis is generally not more than 12.0m. The wall thickness t w Usually 0.6-1.2m:

[0097] B1≤9.0 (1)

[0098] B3≤12.0 (2)

[0099] t w =0.6-1.2 (3)

[0100] B1-B2=B3-B4=2t w (4)

[0101] Including the vertical cross-sectional dimensions of the single-chamber grid-type underground continuous wall foundation and the foundation burial depth L e and the thickness of the cap plate t cap ;

[0102] ② Single-chamber grid-type ground-connected wall foundation material parameters

[0103] Including elastic modulus E w , Poisson's ratio ν w , bulk modulus K w , shear modulus G w and material density ρ w . Elastic modulus E w It is related to the concrete grade used. The Poisson's ratio ν is calculated based on the cube compressive strength value or empirical value according to relevant specifications. w Measured by test, if there is no measured data, ν is taken for ordinary concrete w =0.15-0.20, ν is often used in design w =0.20, material density ρ w For ordinary concrete: 2200-2500kg / m 3 , the design usually adopts 2400kg / m 3 , bulk modulus K w and shear modulus G w Calculated by elastic modulus and Poisson's ratio.

[0104] S2. Determine the strength and stiffness parameters of clay soil and sandy soil required for calculation

[0105] ① Soil properties of clay soil

[0106] Including deformation parameters bulk modulus K c , shear modulus G c , strength parameter internal friction angle and cohesion c c , soil density ρ c and lateral earth pressure coefficient K0. Bulk modulus K c and shear modulus G c The cohesion c is obtained and converted through indoor triaxial test. c and friction angle The data measured by the triaxial test can be used to draw the Mohr circle for calculation. The soil density is obtained by drying in an oven to obtain the dry density of the soil for reference. The lateral earth pressure coefficient is calculated as follows:

[0107]

[0108] in: is the internal friction angle of clay soil;

[0109] ②Sandy soil parameters

[0110] Including deformation parameters bulk modulus K s , shear modulus G s , dilatancy angle ψ, strength parameter internal friction angle and cohesion c s , soil density ρ s and the passive earth pressure coefficient K p . Bulk modulus K s and shear modulus G s The cohesion c is obtained and converted through indoor triaxial test. s and friction angle The Mohr circle can be calculated by using the data measured by the triaxial test. The soil density is obtained by drying in an oven to obtain the dry density of the soil for reference. The passive earth pressure coefficient is calculated as follows:

[0111]

[0112] in: is the internal friction angle of clay soil.

[0113] S3. Based on the numerical model of grid-type ground-connected wall foundation in clay and sand, loads are applied step by step on the side of the foundation slab to extract and calculate displacement data and stress data Obtain the ultimate soil reaction force p of two types of soil i,u,c and p i,u,s

[0114] like Figure 2 and 3 As shown in the figure, the normal stress of the soil around the wall at different depths i along the x-axis is extracted. and tangential stress , and calculate the algebraic sum of the initial stresses around the wall

[0115] The target horizontal static load H is divided into n levels. The area of ​​the side area of ​​the foundation slab of the single-chamber ground-connected wall is S = B3t cap Initial load is applied step by step And each level increment is Stress load H′, n=1,2,3……;

[0116] Extract the wall displacement at different depths i under n-level load and the normal stress of the surrounding soil along the x-axis and tangential stress And calculate the wall circumferential stress increment Calculate Linear Stress Increment

[0117] Record the displacement increment of the wall with a depth of i when the load level is n. And the linear stress data of the soil around the wall For further data processing;

[0118] Repeat the above three steps until H′=H;

[0119] Draw a py curve, such as Figure 4 As shown in the figure, the ultimate soil reaction force p around the wall of two types of soil at different depths is obtained respectively. i,u,c and p i,u,s .

[0120] S4. Normalize the numerical results of earth pressure of two types of soils respectively, determine the ultimate soil reaction adjustment coefficient α1 and depth influence coefficient α2 of cohesive soil, and calculate the ultimate soil reaction adjustment coefficient α under different B3 sizes by eliminating the dependence on the horizontal section size B3 of the foundation. 1,e and α 2,e , and its calculation parameters β1, β2, β3, β4 and β5, determine the influence factor α3 and depth influence factor α4 of the ultimate soil reaction of sandy soil, and calculate the ultimate soil reaction adjustment coefficient α under different B3 sizes by eliminating the dependence of the foundation horizontal section size B3. 3,e and α 4,e , and its calculation parameters β6, β7, β8 and β9

[0121] Calculation of the undrained shear strength τ of cohesive soil based on the Mohr-Coulomb elastoplastic constitutive criterion f :

[0122]

[0123] Where: c c is the cohesion of clay soil, is the friction angle of cohesive soil, γ′ c is the effective weight of clay, z is the depth, and K0 is the lateral earth pressure coefficient of clay, which is provided by step S2.

[0124] Draw N w -z curve, the dimensionless wall side bearing capacity coefficient N is fitted using the following formula w Relationship with depth:

[0125]

[0126] Where: N w is the dimensionless bearing capacity coefficient of the wall side, α1 is the adjustment coefficient of the ultimate soil reaction, and α2 is the depth influence coefficient.

[0127] The calculation method of the ultimate soil reaction force of the single-chamber grid-type underground continuous wall foundation in clay soil is constructed based on the ultimate soil reaction force adjustment coefficient α1 and the depth influence coefficient α2:

[0128]

[0129] Where: s u It is the undrained shear strength of clay, obtained through indoor triaxial test or on-site static touch probe. When there is no test data, it is calculated according to Mohr's Coulomb criterion in the previous steps.

[0130] The normalization method is used to process the ultimate soil reaction adjustment coefficient α1 and the depth influence coefficient α2 to eliminate the dependence of the ultimate soil reaction on the cross-sectional size of the ground-connected wall foundation. The ultimate soil reaction adjustment coefficient α1 and the depth influence coefficient α2 affected by different foundation cross-sectional sizes can be obtained by the following formula:

[0131]

[0132] Where: α 1,e The ultimate soil reaction adjustment coefficient when the foundation section size B3 = em, α 2,e is the depth influence coefficient when the basic cross-section size B3 = em, α 2,5 =1.139,α 1,5 =1.545, β1=-0.275, β2=1.266, β3=0.004, β4=1.247, β5=0.996, the value of e is determined by step S1;

[0133] Through the combined calculation of the above steps, the ultimate soil reaction calculation method applicable to single-chamber grid-type underground continuous wall foundation of any cross-sectional size in clay soil at different depths is finally obtained:

[0134]

[0135] In order to eliminate the dependence of different cross-sectional sizes of diaphragm wall foundations in sandy soil foundations, the following power function is used to fit the relationship between the ultimate soil reaction force around the wall and the depth, and a calculation method for the ultimate soil reaction force of a single-chamber grid-type underground continuous wall foundation in sandy soil is established:

[0136]

[0137] Where: K p is the passive earth pressure coefficient of sandy soil, γ′ s is the effective weight of sandy soil, B3 is the outer peripheral dimension of the basic section perpendicular to the x-axis, α3 is the influence coefficient of the basic section dimension, and α4 is the depth influence coefficient.

[0138] Through data normalization and fitting, the cross-sectional influence coefficient α calculated by different cross-sectional dimensions in sand foundation is established. 3,e and depth influence coefficient α 4,e as follows:

[0139]

[0140] Where: α 3,e The ultimate soil reaction adjustment coefficient when the foundation section size B3 = em, α 4,e is the depth influence coefficient when the basic cross-section size B3 = em, α 3,5 =1.479,α 4,5 =1.517, β6=0.997, β7=-0.4, β8=0.076, β9=0.924, the value of e is determined by step S1.

[0141] Through the combined calculation of the above steps, the ultimate soil reaction force calculation method applicable to single-chamber grid-type underground continuous wall foundation of any cross-sectional size at different depths in sandy soil is finally obtained:

[0142]

[0143] S5. Process the relationship between soil pressure and displacement of sandy soil foundation under small displacement conditions, and determine the depth influence factors α5, α6 and size influence factor α7 of the initial foundation reaction modulus of sandy soil foundation

[0144] The initial foundation reaction modulus data of different depths with deformation states of wall mud surface displacement in the range of 1.0-2.0 mm were sorted and fitted, and the calculation formula of the initial foundation reaction modulus of sand under different cross-sectional sizes and depths of the ground-connected wall foundation was determined. In order to express the relationship between the initial foundation reaction modulus and the depth, the following exponential function was used for calculation:

[0145]

[0146] Where: n h It is the initial foundation reaction coefficient related to the relative density of sand. If there is no test data, it can be taken as 1.1-1.3MN / m for loose sand. 3 , medium dense sand takes 3.3-11.0MN / m 3 , compacted sand takes 11.0-23.4MN / m 3 , α5 and α6 are depth influence coefficients, which are α5=0.166 and α6=0.05 respectively.

[0147] Further, taking the single-chamber grid-type ground-connected wall foundation with B3=5.0m as a reference, the normalized relationship between the initial foundation reaction modulus and the cross-sectional size ratio of different cross-sectional sizes in the sand foundation is established to eliminate the cross-sectional size dependence of the ground-connected wall foundation, and the following function fitting is used:

[0148]

[0149] in: is the initial foundation reaction modulus when B3=em, For reference to the initial foundation reaction modulus, different values ​​are taken at different depths. 3,e The basic cross-sectional dimensions are B3=em, α7=0.985.

[0150] Finally, a calculation method for the initial foundation reaction modulus of a single-chamber grid-type underground continuous wall foundation in sandy soil was established:

[0151]

[0152] S6. Use hyperbolic tangent function to fit the relationship between displacement and earth pressure of two types of soil

[0153] The relationship between the soil pressure around the cohesive soil wall and the wall displacement is established, and the hyperbolic tangent function is used to fit the optimal curve:

[0154]

[0155] Where: p is soil reaction force, y is displacement, p i,u,c is the ultimate soil reaction of clay, provided by step S4, and λ1 and λ2 are the fitting parameters of the clay py curve.

[0156] The relationship between the soil pressure around the sandy soil wall and the wall displacement is established, and the hyperbolic tangent function is used for fitting:

[0157]

[0158] Where: p is soil reaction force, y is displacement, p i,u,s is the ultimate soil reaction force of sand, provided by step S4, k ini,i is the initial foundation reaction modulus of sand, provided by step S5.

[0159] By fitting the data with the hyperbolic tangent function, the ultimate soil reaction forces of clay and sand can correspond well. The calculated stiffness of sand is too soft, that is, the initial foundation reaction modulus of sand is too small to varying degrees. The following linear function related to soil depth and foundation section size is used for correction:

[0160]

[0161] in: is the correction function of the initial foundation reaction modulus of sand.

[0162] S7. Establish mathematical analysis models for predicting the interaction response between single-chamber grid-type underground continuous wall foundation and surrounding soil in clay and sand foundations respectively

[0163] Clay soil:

[0164] Sandy soil:

Claims

1. A method for calculating the py curve of a single-chamber grid-type underground continuous wall foundation, characterized in that: The following steps are involved: S1. Determine the geometric dimensions, material strength and stiffness parameters of the grid-type underground continuous wall foundation required for calculation; S2. Determine the strength and stiffness parameters of clay soil and sandy soil foundation required for calculation respectively; S3. Based on the numerical model of grid-type diaphragm wall foundation in clay and sand, loads are applied step by step on the side of the foundation slab to extract and calculate displacement data and stress data Obtain the ultimate soil reaction force p of two types of soil i,u,c and p i,u,s ; S4. Normalize the numerical results of earth pressure of two types of soils respectively, determine the ultimate soil reaction adjustment coefficient α1 and depth influence coefficient α2 of cohesive soil, and calculate the ultimate soil reaction adjustment coefficient α under different B3 sizes by eliminating the dependence on the horizontal section size B3 of the foundation. 1,e and α 2,e , and its calculation parameters β1, β2, β3, β4 and β5, determine the influence factor α3 and depth influence factor α4 of the ultimate soil reaction of sandy soil, and calculate the ultimate soil reaction adjustment coefficient α under different B3 sizes by eliminating the dependence of the foundation horizontal section size B3. 3,e and α 4,e , and its calculation parameters β6, β7, β8 and β9; S5. Process the relationship between soil pressure and displacement of sandy soil foundation under small displacement conditions, and determine the depth influence factors α5, α6 and size influence factor α7 of the initial foundation reaction modulus of sandy soil foundation; S6. Use hyperbolic tangent function to fit the relationship between displacement and earth pressure of two types of soils; S7. Mathematical analysis models are established to predict the interaction response between single-chamber grid-type underground continuous wall foundation and surrounding soil in clay and sand foundations respectively.

2. According to the single-chamber grid-type underground continuous wall foundation py curve calculation method described in claim 1, it is characterized in that: The step S1 is specifically as follows: ①Geometric parameters of single-chamber grid-type ground-connected wall foundation Including the horizontal cross-sectional dimensions B1, B2, B3, B4 of the single-chamber grid-type underground continuous wall foundation and the wall thickness t w , where B1 is the outer dimension of the foundation section perpendicular to the y-axis, B2 is the inner dimension of the foundation section perpendicular to the y-axis, B3 is the outer dimension of the foundation section perpendicular to the x-axis, and B4 is the inner dimension of the foundation section perpendicular to the x-axis. The horizontal section dimensions need to meet the structural requirements. The outer dimension B1 of the single-chamber grid-type underground continuous wall foundation perpendicular to the y-axis is generally not more than 9.0m, and the outer dimension B3 perpendicular to the x-axis is generally not more than 12.0m. The wall thickness t w Usually 0.6-1.2m: B1≤9.0 (1) B3≤12.0 (2) t w ＝0.6-1.2 (3) <h2 style=";text-align:left;direction:ltr">B1-B2=B3-B4=2t<h2 style=";text-align:left;direction:ltr"> w <h2 style=";text-align:left;direction:ltr"> (4) Including the vertical cross-sectional dimensions of the single-chamber grid-type underground continuous wall foundation and the foundation burial depth L e and the thickness of the cap plate t cap ; ② Single-chamber grid-type ground-connected wall foundation material parameters Including elastic modulus E w , Poisson's ratio v w , bulk modulus K w , shear modulus G w and material density ρ w . Elastic modulus E w It is related to the concrete grade used. The Poisson's ratio ν is calculated based on the cube compressive strength value or empirical value according to relevant specifications. w Measured by experiment, if there is no measured data, take ν w =0.2, material density ρ w For ordinary concrete: 2200-2500kg / m 3 , the design usually adopts 2400kg / m 3 , bulk modulus K w and shear modulus G w Calculated by elastic modulus and Poisson's ratio.

3. According to the single-chamber grid-type underground continuous wall foundation py curve calculation method described in claim 1, it is characterized in that: The step S2 is specifically as follows: ① Soil properties of clay soil Including deformation parameters bulk modulus K c , shear modulus G c , strength parameter internal friction angle and cohesion c c , soil density ρ c and lateral earth pressure coefficient K0. Bulk modulus K c and shear modulus G c The cohesion c is obtained and converted through indoor triaxial test. c and friction angle The data measured by the triaxial test can be used to draw the Mohr circle for calculation. The soil density is obtained by drying in an oven to obtain the dry density of the soil for reference. The lateral earth pressure coefficient is calculated as follows: in: is the internal friction angle of clay soil; ②Sandy soil parameters Including deformation parameters bulk modulus K s , shear modulus G s , dilatancy angle ψ, strength parameter internal friction angle and cohesion c s , soil density ρ s and the passive earth pressure coefficient K p . Bulk modulus K s and shear modulus G s The cohesion c is obtained and converted through indoor triaxial test. s and friction angle The Mohr circle can be calculated by using the data measured by the triaxial test. The soil density is obtained by drying in an oven to obtain the dry density of the soil for reference. The passive earth pressure coefficient is calculated as follows: in: is the internal friction angle of clay soil.

4. According to claim 1, a single-chamber grid-type underground continuous wall foundation py curve calculation method is characterized in that: The step S3 is specifically as follows: S31. Extract the normal stress of the soil around the wall at different depths i along the x-axis and tangential stress And calculate the algebraic sum of the initial stresses around the wall S32. Divide the target horizontal static load H into n levels. The area of ​​the side area of ​​the foundation slab of the single-chamber ground-connected wall is S = B3t cap Initial load is applied step by step And each level increment is Stress load H′, n=1,2,3……; S33, extract the wall displacement at different depths i under load level n and the normal stress of the surrounding soil along the x-axis and tangential stress And calculate the wall circumferential stress increment Calculate Linear Stress Increment S34, respectively record the displacement increment of the wall depth i when the load level is n And the linear stress data of the soil around the wall For further data processing; S35, repeat steps S32, S33 and S34 until H′=H; S36, respectively obtain the ultimate soil reaction force p around the wall of two types of soil at different depths i,u,c and p i,u,s .

5. According to claim 1, a single-chamber grid-type underground continuous wall foundation py curve calculation method is characterized in that: The step S4 is specifically as follows: S41. Calculation of the undrained shear strength τ of cohesive soil based on the Mohr-Coulomb elastoplastic constitutive criterion f : Where: c c is the cohesion of clay soil, is the friction angle of clay soil, γ′ c is the effective weight of clay soil, z is the depth, K0 is the lateral earth pressure coefficient of clay soil, provided by step S2 in claim 1; S42, draw N w -z curve, the dimensionless wall side bearing capacity coefficient N is fitted using the following formula w Relationship with depth: Where: N w is the dimensionless bearing capacity coefficient of the wall side, α1 is the adjustment coefficient of the ultimate soil reaction, and α2 is the depth influence coefficient; S43. The calculation method of the ultimate soil reaction force for the single-chamber grid-type underground continuous wall foundation in cohesive soil is constructed based on the ultimate soil reaction force adjustment coefficient α1 and the depth influence coefficient α2: Where: s u is the undrained shear strength of cohesive soil, obtained through indoor triaxial test or on-site static touch detection. When there is no test data, it can be calculated according to the Mohr-Coulomb criterion by referring to step S41 of claim 5; S44. The normalization method is used to process the ultimate soil reaction adjustment coefficient α1 and the depth influence coefficient α2 to eliminate the dependence of the ultimate soil reaction on the cross-sectional size of the ground-connected wall foundation. The ultimate soil reaction adjustment coefficient α1 and the depth influence coefficient α2 affected by different foundation cross-sectional sizes can be obtained by the following formula: Where: α 1,e The ultimate soil reaction adjustment coefficient when the foundation section size B3 = em, α 2,e is the depth influence coefficient when the basic cross-section size B3 = em, α 2,5 =1.139,α 1,5 =1.545, β1=-0.275, β2=1.266, β3=0.004, β4=1.247, β5=0.996, the value of e is determined by step S1 of claim 1; S45. Through the combined calculation of steps S43 and S44, a method for calculating the ultimate soil reaction force at different depths applicable to a single-chamber grid-type underground continuous wall foundation of any cross-sectional size in clay soil is finally obtained: S46. In order to eliminate the dependence of different cross-sectional dimensions of diaphragm wall foundations in sandy soil foundations, the following power function is used to fit the relationship between the ultimate soil reaction force around the wall and the depth, and a calculation method for the ultimate soil reaction force of a single-chamber grid-type underground continuous wall foundation in sandy soil is established: Where: K p is the passive earth pressure coefficient of sandy soil, γ′ s is the effective weight of sandy soil, B3 is the outer peripheral dimension of the basic section perpendicular to the x-axis, α3 is the influence coefficient of the basic section dimension, and α4 is the depth influence coefficient; S47. Through data normalization and fitting, the cross-sectional dimension influence coefficient α calculated by different cross-sectional dimensions in the sand foundation is established. 3,e and depth influence coefficient α 4,e as follows: Where: α 3,e The ultimate soil reaction adjustment coefficient when the foundation section size B3 = em, α 4,e is the depth influence coefficient when the basic cross-section size B3 = em, α 3,5 =1.479,α 4,5 =1.517, β6=0.997, β7=-0.4, β8=0.076, β9=0.924, the value of e is determined by step S1 of claim 1; S48. Through the combined calculation of steps S43 and S44, a method for calculating the ultimate soil reaction force at different depths of a single-chamber grid-type underground continuous wall foundation of any cross-sectional size in sandy soil is finally obtained:

6. According to claim 1, a single-chamber grid-type underground continuous wall foundation py curve calculation method is characterized in that: The step S5 is specifically as follows: S51. Arrange and fit the initial foundation reaction modulus data of different depths with deformation states of wall mud surface displacement in the range of 1.0-2.0 mm, determine the calculation formula of the initial foundation reaction modulus of sand under different cross-sectional sizes and depths of the ground-connected wall foundation, and use the following exponential function to calculate in order to express the relationship between the initial foundation reaction modulus and the depth: Where: n h It is the initial foundation reaction coefficient related to the relative density of sand. If there is no test data, it can be taken as 1.1-1.3MN / m for loose sand. 3 , medium dense sand takes 3.3-11.0MN / m 3 , compacted sand takes 11.0-23.4MN / m 3 , α5 and α6 are depth influence coefficients, α5 = 0.166, α6 = 0.05 respectively; S52. Further, taking the single-chamber grid-type ground-connected wall foundation with B3=5.0m as a reference, the normalized relationship between the initial foundation reaction modulus and the cross-sectional size ratio of different cross-sectional sizes in the sand foundation is established to eliminate the cross-sectional size dependence of the ground-connected wall foundation, and the following function fitting is adopted: in: is the initial foundation reaction modulus when B3=em, For reference to the initial foundation reaction modulus, different values ​​are taken at different depths. 3,e The basic cross-sectional dimensions are B3 = em, α7 = 0.985; S53. Finally, a calculation method for the initial foundation reaction modulus of a single-chamber grid-type underground continuous wall foundation in sandy soil is established:

7. The method for calculating the py curve of a single-chamber grid-type underground continuous wall foundation according to claim 1, characterized in that: The step S6 is specifically as follows: S61. Establish the relationship between the soil pressure around the cohesive soil wall and the wall displacement, and use the hyperbolic tangent function to fit the best curve: Where: p is soil reaction force, y is displacement, p i,u,c is the clay limit soil reaction force, provided by step S45 of claim 5, λ1 and λ2 are clay py curve fitting parameters; S62. Establish the relationship between the soil pressure around the sandy soil wall and the wall displacement, and use the hyperbolic tangent function to fit: Where: p is soil reaction force, y is displacement, p i,u,s is the ultimate soil reaction force of sand, provided by step S48 of claim 5, k ini,i is the initial foundation reaction modulus of sand, provided by step S53 of claim 6; S63. Using the above hyperbolic tangent function to fit the data, the ultimate soil reaction forces of clay and sand can correspond well. The calculated stiffness of sand is too soft, that is, the initial foundation reaction modulus of sand is too small to varying degrees. The following linear function related to soil depth and foundation section size is used for correction: in: is the correction function of the initial foundation reaction modulus of sand.

8. The method for calculating the py curve of a single-chamber grid-type underground continuous wall foundation according to claim 1, characterized in that: The step S7 specifically includes establishing the py curves applicable to the horizontal stress of the single-chamber grid-type underground continuous wall foundation in the clay soil and sand soil foundations respectively: Clay soil: Sandy soil:

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