A method for analyzing bearing capacity of annular foundation bottom surface and soft underlying layer

Abstract

The application provides a kind of annular foundation bottom surface and soft weak underlying layer bearing capacity analysis method in the field of foundation engineering, the method comprises the following steps: calculating annular foundation bottom surface pressure, regarding the annular foundation with thickness b as two adjacent imaginary strip foundations with width b, correcting the bearing capacity characteristic value of foundation bottom surface, and carrying out bearing capacity checking; according to the principle of additional stress calculation of a point inside the Buzingnaiske elastomer, the additional stress at the top surface of soft weak underlying layer under the midpoint of annular foundation and the top surface of soft weak underlying layer under the midpoint of imaginary strip foundation is calculated respectively, then the deadweight stress of soil at the top surface of soft weak underlying layer is calculated, the bearing capacity characteristic value of soft weak underlying layer top surface is corrected, and the bearing capacity of soft weak underlying layer foundation is checked further.The application provides a feasible method for bearing capacity checking of annular foundation bottom surface and soft weak underlying layer based on strip foundation bearing capacity checking and the principle of additional stress calculation of a point inside the Buzingnaiske elastomer.

Description

Technical Field

[0001] This invention belongs to the field of foundation engineering, and particularly relates to a method for analyzing the bearing capacity of the bottom surface of a ring foundation and a weak underlying layer. Background Technology

[0002] Currently, for the verification of the bearing capacity of the foundation, the characteristic value of the bearing capacity at the bottom of the foundation should first be corrected, and then compared with the base pressure for verification. However, the standard does not make clear provisions for the verification method of the bearing capacity of the bottom of the ring foundation. When calculating the base pressure of the ring foundation, the self-weight of the foundation above the base and the self-weight of the soil are often taken into account. Moreover, when correcting the bearing capacity of the bottom of the ring foundation, the width correction is not very clear, which makes the design verification method of the ring foundation inconsistent with reality. Furthermore, the verification of the bearing capacity of the weak underlying layer often adopts the stress diffusion angle principle, and only considers the simple stress superposition for the additional stress at the center of the ring foundation, which is not accurate enough.

[0003] Therefore, there is currently no method for verifying the bearing capacity of the bottom surface of a ring foundation and the weak underlying layer, making it impossible to conduct an accurate bearing capacity analysis of the bottom surface of a ring foundation. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, the present invention aims to provide a method for analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer, so as to make the analysis of the bearing capacity of the bottom surface of the ring foundation and its weak underlying layer more reasonable.

[0005] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0006] This invention provides a method for analyzing the bearing capacity of the bottom surface of a ring foundation and a weak underlying layer, the method comprising:

[0007] Step S1: Calculate the pressure on the bottom surface of the annular foundation. Treat the annular foundation with thickness b as two adjacent imaginary strip foundations with width b. Correct the characteristic value of the bearing capacity of the bottom surface of the annular foundation. Verify and analyze the bearing capacity of the bottom surface of the annular foundation based on the ground pressure of the annular foundation and the corrected characteristic value of the bearing capacity of the bottom surface of the annular foundation.

[0008] Step S2: Based on the calculation principle of additional stress at a point inside the Businesk elastomer, calculate the additional stress at the top surface of the weak underlying layer below the midpoint of the ring foundation and at the top surface of the weak underlying layer below the midpoint of the hypothetical strip foundation, respectively, and calculate the self-weight stress of the soil at the top surface of the weak underlying layer. Correct the characteristic value of the foundation bearing capacity at the top surface of the weak underlying layer. Based on the additional stress, self-weight stress, and the corrected characteristic value of the foundation bearing capacity at the top surface of the weak underlying layer, verify and analyze the foundation bearing capacity of the weak underlying layer.

[0009] The calculation of the pressure on the bottom surface of the annular foundation includes:

[0010] When an axial load is applied to the bottom surface of the annular foundation, the pressure p on the bottom surface of the annular foundation is... k Calculate using the following formula:

[0011]

[0012] When a small eccentric load is applied to the bottom surface of the annular foundation, the pressure p on the bottom surface of the annular foundation is calculated. k and the maximum pressure on the base; wherein the pressure p on the bottom surface of the annular base k The calculation is the same as above, where the maximum pressure p of the base is... kmax Calculate using the following formula:

[0013]

[0014] Among them, F k M is the load of the superstructure acting on the ring foundation. k Let D be the bending moment acting on the bottom of the foundation, d be the outer diameter of the ring foundation, and G be the inner diameter of the ring foundation. k For the self-weight of the ring foundation, G k It only includes the reinforced concrete portion of the ring-shaped foundation.

[0015] Specifically, for the bottom surface of the annular foundation, the small eccentric load is a load with an eccentricity e that satisfies the following conditions:

[0016]

[0017] The correction of the characteristic value of the bearing capacity of the foundation bottom surface includes: calculating the correction value of the characteristic value of the bearing capacity of the ring foundation bottom surface using the following formula:

[0018] f a =f ak1 +η b γ(b-3)+η d1 γ m1 (h-0.5)

[0019] Among them, f ak1 γ is the uncorrected characteristic value of the bearing capacity at the foundation bottom; γ is the unit weight of the soil below the foundation bottom; γ m1 η is the weighted average unit weight of the soil above the foundation bottom; b is the width of the hypothetical strip foundation bottom, b = 3 when b < 3; h is the height of the ring foundation, h = 0.5 when h < 0.5; η b η d1 This is the bearing capacity correction factor.

[0020] The verification and analysis of the bearing capacity of the bottom surface of the annular foundation based on the ground pressure of the annular foundation and the corrected characteristic value of the bearing capacity of the bottom surface of the annular foundation includes:

[0021] When an axial load is applied to the bottom surface of the annular foundation, verify whether the bearing capacity of the bottom surface of the annular foundation meets the following conditions:

[0022]

[0023] When a small eccentric load is applied to the bottom surface of the ring foundation, in addition to verifying according to the above formula, it is also necessary to verify whether the following conditions are met:

[0024]

[0025] The correction of the characteristic value of the foundation bearing capacity at the top surface of the weak underlying layer includes:

[0026] The correction value f of the characteristic value of the bearing capacity of the foundation at the top surface of the weak underlying layer is calculated using the following formula. az :

[0027] f az =f ak2 +η d2 γ m2 (h+z-0.5)

[0028] Among them, f ak2 γ represents the uncorrected characteristic value of the bearing capacity at the top surface of the weak underlying layer. m2 η is the weighted average unit weight of the soil above the top surface of the weak underlying layer, z is the distance from the top surface of the weak underlying layer to the bottom surface of the foundation, and η is the weighted average unit weight of the soil above the top surface of the weak underlying layer. d2 This is the bearing capacity correction factor.

[0029] The verification and analysis of the bearing capacity of the foundation of the weak underlying layer based on the additional stress, self-weight stress, and the corrected characteristic value of the bearing capacity of the foundation at the top surface of the weak underlying layer includes:

[0030] Verify whether the bearing capacity at the top surface of the weak underlying layer below the midpoint of the ring foundation satisfies the following formula:

[0031]

[0032] Verify whether the bearing capacity at the top surface of the weak underlying layer below the midpoint of the hypothetical strip foundation satisfies the following formula:

[0033]

[0034] Where, α O α is the additional stress coefficient at the top surface of the weak underlying layer below the midpoint of the bottom surface of the annular foundation. Rdenoted as the additional stress coefficient at the top surface of the weak underlying layer below the midpoint of the uniformly distributed strip load of width b.

[0035] Wherein, the α O The determination method is as follows:

[0036] The difference in the additional stress coefficient at the top surface of the weak underlying layer below the midpoint of the two uniformly distributed circular loads on the bottom surface of the annular foundation is taken as the additional stress coefficient α. O .

[0037] Wherein, the α R The determination method is as follows:

[0038] The first additional stress generated by the imaginary strip foundation with width b on the top surface of the weak underlying layer below the midpoint of the imaginary strip foundation, and the second additional stress generated by the adjacent imaginary strip foundation with the same width b on the top surface of the weak underlying layer below the midpoint of the imaginary strip foundation.

[0039] By superimposing the first and second additional stresses using the corner point method, the α is obtained. R .

[0040] The technical solutions provided in the embodiments of the present invention have the following beneficial effects:

[0041] This invention provides a method for analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer. The method calculates the pressure on the bottom surface of the ring foundation by treating the ring foundation of thickness *b* as two adjacent imaginary strip foundations of width *b*. The characteristic value of the bearing capacity of the foundation bottom surface is corrected, and the bearing capacity is verified. Based on the principle of calculating additional stress at a single point within a Bushnaesk elastomer, the additional stress at the top surface of the weak underlying layer below the midpoint of the ring foundation and at the top surface of the weak underlying layer below the midpoint of the imaginary strip foundation are calculated respectively, thereby verifying the bearing capacity of the weak underlying layer at these two points. This invention, based on the verification of the bearing capacity of strip foundations and the principle of calculating additional stress at a single point within a Bushnaesk elastomer, provides a practical and feasible method for verifying and analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer.

[0042] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1This is a flowchart illustrating a method for analyzing the bearing capacity of a ring-shaped foundation bottom and a weak underlying layer according to an embodiment of the present invention.

[0045] Figure 2 This is a plan view of the annular foundation as described in an embodiment of the present invention;

[0046] Figure 3 This is a schematic diagram of the elevation section for verifying the bearing capacity of point R at the top surface of the weak underlying layer below the midpoint of the annular foundation bottom surface and the imaginary strip foundation with width b, as described in an embodiment of the present invention.

[0047] Figure 4 This is a schematic diagram of the elevation profile for verifying the bearing capacity at point O on the top surface of the weak underlying layer below the midpoint of the annular foundation according to an embodiment of the present invention.

[0048] Figure 5 This is a block plan view of a hypothetical strip foundation with width b, as described in an embodiment of the present invention, showing a uniformly distributed load. Detailed Implementation

[0049] After discovering the aforementioned problems, the inventors of this application conducted research on the bearing capacity of the bottom surface of annular foundations and weak underlying layers. The research revealed inconsistencies in the bearing capacity correction and base pressure calculation during the verification of the bearing capacity of the bottom surface of annular foundations. Furthermore, the use of the stress diffusion angle method to calculate the additional stress on the top surface of the weak underlying layer was not accurate enough during the verification of its bearing capacity. However, currently, there is no clear verification method for the bearing capacity of the bottom surface of annular foundations and weak underlying layers.

[0050] It should be noted that the defects in the above-mentioned prior art solutions are all the result of the inventors' practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the embodiments of the present invention in the following text should be the inventors' contributions to the present invention.

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can also be combined with each other.

[0052] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of the invention, the terms "first," "second," "third," "fourth," etc., are used only to distinguish descriptions and should not be construed as merely or implying relative importance.

[0053] Following the above in-depth analysis, this application analyzes the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer. It finds that the bearing capacity of the bottom surface of the ring foundation can be corrected by treating it as a hypothetical strip foundation. Furthermore, calculating the additional stress under the ring foundation using the principle of additional stress at a single point inside the Buchenesk elastic body is more accurate and reliable than using the stress diffusion angle method. Based on this, this application provides a method for analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer. This method can be used to analyze the bearing capacity of a ring foundation; however, this invention is not limited to this.

[0054] like Figure 1 The diagram shown is a flowchart of a method for analyzing the bearing capacity of a ring-shaped foundation bottom surface and a weak underlying layer according to an embodiment of the present invention. The method includes the following steps:

[0055] Step S1: Calculate the pressure on the bottom surface of the annular foundation. Treat the annular foundation with thickness b as two adjacent imaginary strip foundations with width b. Correct the characteristic value of the bearing capacity of the bottom surface of the annular foundation. Verify and analyze the bearing capacity of the bottom surface of the annular foundation based on the ground pressure of the annular foundation and the corrected characteristic value of the bearing capacity of the bottom surface of the annular foundation.

[0056] like Figure 2 As shown, the bottom area A of the annular foundation is:

[0057]

[0058] In the formula, D is the outer diameter of the annular foundation, and d is the inner diameter of the annular foundation.

[0059] When an axial load is applied to the bottom surface of the annular foundation, the pressure p on the bottom surface of the annular foundation is... k Calculate using the following formula:

[0060]

[0061] In the formula, F k G is the load of the superstructure acting on the ring foundation. k For the self-weight of the ring foundation, G k It only includes the reinforced concrete portion of the ring-shaped foundation.

[0062] Substituting formula (1) into formula (2) yields:

[0063]

[0064] When a small eccentric load is applied to the bottom surface of the annular foundation, the pressure p on the bottom surface of the annular foundation is calculated. k and the maximum pressure on the base; wherein the pressure p on the bottom surface of the annular base k The calculation is the same as in equation (3) above, for the maximum pressure p at the base. kmaxThe following formula can be used for calculation:

[0065]

[0066] In the formula, M k Let W be the bending moment acting on the bottom surface of the ring foundation, and W be the section modulus of the bottom surface of the ring foundation. For a ring foundation:

[0067]

[0068] Substituting formulas (3) and (5) into formula (4), we get:

[0069]

[0070] like Figure 3 As shown, the annular foundation with thickness b is considered as two adjacent imaginary strip foundations with width b. The correction value f of the bearing capacity characteristic value at the bottom of the foundation is... a It can be calculated using the following formula:

[0071] f a =f ak1 +η b γ(b-3)+η d1 γ m1 (h-0.5) (7)

[0072] In the formula, f ak1 γ is the uncorrected characteristic value of the foundation bearing capacity at the foundation bottom surface; γ is the unit weight of the soil below the foundation bottom surface; γ m1 η is the weighted average unit weight of the soil above the foundation base; b is the width of the hypothetical strip foundation base (i.e., the thickness of the ring foundation), b = 3 when b < 3; h is the height of the ring foundation, h = 0.5 when h < 0.5; η b η d1 The bearing capacity correction factor can be determined according to the properties of the soil layer at the bottom of the foundation, based on Table 5.2.4 of GB 50007-2011 "Code for Design of Building Foundations".

[0073] The verification and analysis of the bearing capacity of the bottom surface of the annular foundation based on the ground pressure of the annular foundation and the corrected characteristic value of the bearing capacity of the bottom surface of the annular foundation includes:

[0074] When an axial load is applied to the bottom surface of the annular foundation, verify whether the bearing capacity of the bottom surface of the annular foundation meets the following conditions:

[0075] p k ≤f a (8)

[0076] Substituting formulas (3) and (7) into formula (8), we get:

[0077]

[0078] When a small eccentric load is applied to the bottom surface of the ring foundation, in addition to verifying according to the above formula (9), it is also necessary to verify whether the following conditions are met:

[0079] p kmax ≤1.2f a (10)

[0080] Substituting formulas (6) and (7) into formula (10), we get:

[0081]

[0082] Step S2: Based on the calculation principle of additional stress at a point inside the Businesk elastomer, calculate the additional stress at the top surface of the weak underlying layer below the midpoint of the ring foundation and at the top surface of the weak underlying layer below the midpoint of the hypothetical strip foundation, respectively, and calculate the self-weight stress of the soil at the top surface of the weak underlying layer. Correct the characteristic value of the foundation bearing capacity at the top surface of the weak underlying layer. Based on the additional stress, self-weight stress, and the corrected characteristic value of the foundation bearing capacity at the top surface of the weak underlying layer, verify and analyze the foundation bearing capacity of the weak underlying layer.

[0083] According to the principle of calculating additional stress at a single point inside a Busineske elastic body, the point of maximum additional stress at the top surface of the weak underlying layer can only occur at... Figure 4 Point O at the top surface of the weak underlying layer below the midpoint of the ring foundation or Figure 3 Since the imaginary strip foundation has a midpoint at point R on the top surface of the weak underlying layer, it is only necessary to check whether the bearing capacity of the foundation at these two points meets the requirements.

[0084] The additional pressure p0 on the bottom surface of the annular foundation is:

[0085] p0 = p k -γ m1 h (12)

[0086] Additional stress p at point O on the top surface of the weak underlying layer below the midpoint of the ring foundation zO for:

[0087] p zO =α O p0 (13)

[0088] In the formula, α O α is the additional stress coefficient at point O on the top surface of the weak underlying layer below the midpoint of the bottom surface of the annular foundation. O The determination method is as follows: the difference in the additional stress coefficient at the top surface of the weak underlying layer below the midpoint of the two uniformly distributed circular loads on the bottom surface of the annular foundation is taken as the additional stress coefficient α. O .like Figure 2As shown, the annular base of the foundation can be considered as the result of subtracting two circles with diameters D and d. Therefore, the additional stress coefficient at the top surface of the weak underlying layer below the midpoint of the uniformly distributed load on each of the two circles is calculated separately, and the difference between the two calculations yields the additional stress coefficient α at the top surface of the weak underlying layer below the midpoint of the annular base. O Obtain the radii r of the two circles and the distance z from the top surface of the weak underlying layer to the bottom surface of the foundation. Based on the z / r values ​​of each circle, the additional stress coefficient at the top surface of the weak underlying layer under the midpoint of the circular uniformly distributed load can be determined by referring to Table K.0.3 in GB50007-2011 "Code for Design of Building Foundation".

[0089] For a circle with diameter D, it can be determined by... The additional stress coefficient α1 at the top surface of the weak underlying layer below the midpoint of a uniformly distributed circular load of diameter D is obtained from the table; for a circle of diameter d, it can be obtained from... From the table, the additional stress coefficient α2 at the top surface of the weak underlying layer below the midpoint of the uniformly distributed circular load of diameter d is obtained. O =α1-α2.

[0090] Based on the corner point method, the additional stress p at point R on the top surface of the weak underlying layer below the midpoint of the imaginary strip foundation is calculated. zR The calculation is as follows:

[0091] p zR =α R p0 (14)

[0092] In the formula, α R is the additional stress coefficient at point R on the top surface of the weak underlying layer below the midpoint of the uniformly distributed strip load of width b.

[0093] α R The calculation method includes: determining the first additional stress generated by the imaginary strip foundation of width b on the top surface of the weak underlying layer below the midpoint of the imaginary strip foundation, and the second additional stress generated by adjacent imaginary strip foundations of the same width b on the top surface of the weak underlying layer below the midpoint of the imaginary strip foundation; then, using the corner point method, superimposing the first and second additional stresses to obtain the α. R The details are as follows:

[0094] like Figure 3 As shown, the calculation of additional stress at point R includes two parts: first, the additional stress generated at point R by the imaginary strip foundation I with width b; and second, the additional stress generated at point R by the adjacent imaginary strip foundation II with the same width b. Therefore, the additional stress coefficient α... R It also consists of two parts, which can be obtained by superimposing them according to the corner point method.

[0095] like Figure 5As shown, auxiliary lines are drawn through point R to make it the common intersection point of several rectangles. The lengths of the long and short sides, l' and b', of each rectangle are obtained. Using the values ​​of l' / b' and z / b', the additional stress coefficients at the corner points of each rectangle are determined by referring to Table K.0.1-1 of GB 50007-2011 "Code for Design of Building Foundations". Based on the principle of corner point superposition, the additional stress coefficients at the corner points of each rectangle are superimposed to obtain the additional stress coefficient α at point R. R .

[0096] α R =4α 矩形ABCD +2(α 矩形ABGH -α 矩形ABFE (15)

[0097] For rectangle ABCD, using the corner point method, l′ / b′>10, z / b′=2z / b, we can find α from the table. ABCD ;

[0098] For rectangle ABGH, using the corner point method, l′ / b′>10, z / b′=z / (3b / 2+d), we can find α from the table. ABGH ;

[0099] For rectangle ABFE, using the corner point method, l′ / b′>10, z / b′=z / (b / 2+d), and by referring to the table, α can be obtained. ABFE The self-weight stress p of the soil at the top surface of the weak underlying layer. cz for:

[0100] p cz =γ m2 (h+z) (16)

[0101] In the formula, γ m2 denoted as the weighted average unit weight of the soil above the top surface of the weak underlying layer, and z is the distance from the top surface of the weak underlying layer to the bottom surface of the foundation.

[0102] Correction value f of the characteristic value of the foundation bearing capacity at the top surface of the weak underlying layer az for:

[0103] f az =f ak2 +η d2 γ m2 (h+z-0.5) (17)

[0104] In the formula, f ak2 η represents the uncorrected characteristic value of the bearing capacity at the top surface of the weak underlying layer. d2 The bearing capacity correction factor can be determined according to the properties of the underlying soft soil layer, based on Table K.0.3 of GB 50007-2011 "Code for Design of Building Foundations".

[0105] The bearing capacity at points O and R is verified using the following formula:

[0106] Verify whether the bearing capacity at point O, located on the top surface of the weak underlying layer below the midpoint of the ring foundation, satisfies the following formula:

[0107] p zO +p cz ≤f az (18)

[0108] Substituting formulas (3), (12), (13), (16), and (17) into formula (18), we get:

[0109]

[0110] Does the bearing capacity at point R on the top surface of the weak underlying layer below the midpoint of the hypothetical strip foundation satisfy the following formula:

[0111] p zR +p cz ≤f az (20)

[0112] Substituting formulas (3), (12), (14), (16), and (17) into formula (20), we get:

[0113]

[0114] The invention will be further explained in detail below through a specific example.

[0115] A circular foundation has an outer diameter D = 6m, an inner diameter d = 2m, a width b = 2m, and a foundation height h = 3m. The load F acting on the circular foundation from the superstructure is... k =5000kN, foundation weight is G k =1500kN, the bearing layer of the foundation is red clay with a water content greater than 0.8 and a unit weight of γ = 18kN / m³. 3 Characteristic value of bearing capacity f of foundation bearing layer ak1 =200kPa, the underlying weak layer is silty soil, the distance from the underlying weak layer to the foundation bottom is z=3m, the characteristic value of the bearing capacity of the underlying weak layer is f. ak2 =120kPa.

[0116] Foundation bearing capacity verification:

[0117] From formulas (4) and (6), the average pressure at the base is P. k =219 kPa, the maximum pressure at the base is P kmax =227kPa,

[0118] For red clay with a moisture content greater than 0.8, the bearing capacity correction factor η can be obtained from the table in GB 50007-2011 "Code for Design of Building Foundations". b =0, η d1 =1.2, from formula (7) the correction value f of the bearing capacity of the foundation bottom surface is obtained. a =254kPa, from formulas (8) and (9) we get:

[0119] p k =219kPa≤f a =254kPa

[0120] p kmax =227kPa≤1.2f a =304.8 kPa

[0121] The bearing capacity of the foundation bottom surface meets the requirements.

[0122] Calculation of bearing capacity of weak underlying soil:

[0123] The annular base of this foundation can be considered as the result of subtracting two circles with diameters D = 6m and d = 2m respectively. Referring to Table K.0.3 of GB 50007-2011 "Code for Design of Building Foundations", the additional stress coefficient α1 at the top surface of the weak underlying layer below the midpoint of a uniformly distributed circular load with diameter D = 6m is 0.647; for a circle with diameter d = 2m, it can be obtained from... Referring to Table K.0.3 of GB 50007-2011 "Code for Design of Building Foundations", the additional stress coefficient α2 at the top surface of the weak underlying layer below the midpoint of a circular uniformly distributed load with a diameter d = 2m is 0.146. O =α1-α2=0.501.

[0124] For rectangles ABCD, ABGH, and ABFE, referring to Table K.0.1-1 of GB 50007-2011 "Code for Design of Building Foundations", the additional stress coefficients at the corner points of each rectangle are as follows:

[0125] For rectangle ABCD, using the corner point method, l′ / b′>10, z / b′=3, we can find α from the table. ABCD =0.099;

[0126] For rectangle ABGH, using the corner point method, l′ / b′>10, z / b′=0.6, we can find α from the table. ABGH =0.234;

[0127] For rectangle ABFE, using the corner point method, l′ / b′>10, z / b′=1, we can find α from the table. ABFE =0.205.

[0128] From formula (15), we get α R =4×0.099+2(0.234-0.205)=0.454;

[0129] The underlying weak layer is silty soil. The bearing capacity correction factor η is obtained from the table. d2 =1.0,

[0130] From formulas (18) and (19), the bearing capacity at point O is verified as follows:

[0131] p zO +p cz =190.7≤f az =219, so the bearing capacity at point O meets the requirements.

[0132] From formulas (20) and (21), the bearing capacity at point R is verified as follows:

[0133] p zR +p cz =182.9≤f az =219, so the bearing capacity at point R meets the requirements.

[0134] This invention provides a method for analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer. The method calculates the pressure on the bottom surface of the ring foundation under axial load and small eccentric load, respectively. The ring foundation with thickness *b* is treated as two adjacent imaginary strip foundations with width *b*. The characteristic value of the bearing capacity of the foundation bottom surface is corrected, and the bearing capacity is verified. Based on the principle of calculating additional stress at a single point inside a Bushnaesk elastomer, the additional stress at point O on the top surface of the weak underlying layer below the midpoint of the ring foundation and at point R on the top surface of the weak underlying layer below the midpoint of the imaginary strip foundation are calculated, thereby verifying the bearing capacity of the weak underlying layer at these two points. This invention, based on the calculation principle of strip foundation bearing capacity and the calculation principle of additional stress at a single point inside a Bushnaesk elastomer, provides a practical method for verifying the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer.

[0135] The above description is merely a preferred embodiment of the present invention and an explanation of the technical principles employed, and is not intended to limit the scope of the claimed invention, but merely to illustrate preferred embodiments of the invention. Those skilled in the art should understand that the scope of the invention is not limited to the specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer, characterized in that, The method includes: Step S1, calculate the pressure on the bottom surface of the annular foundation, with a thickness of... b The ring foundation is considered as two adjacent widths. b The hypothetical strip foundation is used to correct the characteristic value of the bearing capacity of the bottom surface of the ring foundation, and the bearing capacity of the bottom surface of the ring foundation is verified and analyzed based on the pressure on the bottom surface of the ring foundation and the corrected characteristic value of the bearing capacity of the bottom surface of the ring foundation. The calculation of the pressure on the bottom surface of the annular foundation includes: When an axial load is applied to the bottom surface of the annular foundation, the pressure on the bottom surface of the annular foundation is... p k Calculate using the following formula: ， When a small eccentric load is applied to the bottom surface of the annular foundation, the pressure on the bottom surface of the annular foundation is calculated. p k and the maximum pressure on the base; wherein the pressure on the bottom surface of the annular base p k The calculation is the same as above, for the maximum pressure of the base. p kmax Calculate using the following formula: ， in, F k The loads of the superstructure acting on the ring foundation. M k The bending moment acting on the bottom of the foundation. D The outer diameter of the ring-shaped foundation, d The inner diameter of the ring foundation, G k For the self-weight of the ring foundation, G k Includes only the reinforced concrete portion of the annular foundation; Step S2: Based on the calculation principle of additional stress at a point inside the Businesk elastomer, calculate the additional stress at the top surface of the weak underlying layer below the midpoint of the ring foundation and at the top surface of the weak underlying layer below the midpoint of the hypothetical strip foundation, respectively, and calculate the self-weight stress of the soil at the top surface of the weak underlying layer. Correct the characteristic value of the foundation bearing capacity at the top surface of the weak underlying layer. Based on the additional stress, self-weight stress, and the corrected characteristic value of the foundation bearing capacity at the top surface of the weak underlying layer, verify and analyze the foundation bearing capacity of the weak underlying layer.

2. The method for analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer according to claim 1, characterized in that, For the bottom surface of the annular foundation, the small eccentric load is the eccentricity. e Loads that meet the following conditions: 。 3. The method for analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer according to claim 1, characterized in that, The correction of the characteristic value of the bearing capacity of the foundation bottom surface includes: calculating the correction value of the characteristic value of the bearing capacity of the ring foundation bottom surface using the following formula: ， in, f ak1 The uncorrected characteristic value of the bearing capacity at the base surface; γ The unit weight of the soil below the foundation bottom surface; γ m1 The weighted average unit weight of the soil above the foundation bottom surface; b For the hypothetical width of the base of the strip foundation, b <3 o'clock b =3; h The height of the ring-shaped foundation. h When <0.5, take h =0.5; η b , η d1 This is the bearing capacity correction factor.

4. The method for analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer according to claim 1, characterized in that, The verification and analysis of the bearing capacity of the bottom surface of the annular foundation based on the ground pressure of the annular foundation and the corrected characteristic value of the bearing capacity of the bottom surface of the annular foundation includes: When an axial load is applied to the bottom surface of the annular foundation, verify whether the bearing capacity of the bottom surface of the annular foundation meets the following conditions: ， When a small eccentric load is applied to the bottom surface of the ring foundation, in addition to verifying according to the above formula, it is also necessary to verify whether the following conditions are met: ， in, f ak1 The uncorrected characteristic value of the bearing capacity at the base surface; γ The unit weight of the soil below the foundation bottom surface; γ m1 The weighted average unit weight of the soil above the foundation bottom surface; b For the hypothetical width of the base of the strip foundation, b <3 o'clock b =3; h The height of the ring-shaped foundation. h When <0.5, take h =0.5; η b , η d1 This is the bearing capacity correction factor.

5. The method for analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer according to claim 1, characterized in that, The correction of the characteristic value of the foundation bearing capacity at the top surface of the weak underlying layer includes: The correction value of the characteristic value of the bearing capacity of the foundation at the top surface of the weak underlying layer is calculated using the following formula. f az : ， in, f ak2 This represents the uncorrected characteristic value of the bearing capacity at the top surface of the weak underlying layer. γ m2 The weighted average unit weight of the soil above the top surface of the weak underlying layer is given. z It is the distance from the top surface of the weak underlying layer to the bottom surface of the foundation. η d2 This is the bearing capacity correction factor.

6. The method for analyzing the bearing capacity of the bottom surface of a ring foundation and its weak underlying layer according to claim 1, characterized in that, The verification and analysis of the bearing capacity of the foundation of the weak underlying layer based on the additional stress, self-weight stress, and the corrected characteristic value of the bearing capacity of the foundation at the top surface of the weak underlying layer includes: Verify whether the bearing capacity at the top surface of the weak underlying layer below the midpoint of the ring foundation satisfies the following formula: ， Verify whether the bearing capacity at the top surface of the weak underlying layer below the midpoint of the hypothetical strip foundation satisfies the following formula: ， in, f ak2 This represents the uncorrected characteristic value of the bearing capacity at the top surface of the weak underlying layer. γ m2 The weighted average unit weight of the soil above the top surface of the weak underlying layer is given. z It is the distance from the top surface of the weak underlying layer to the bottom surface of the foundation. η d2 This is the bearing capacity correction factor; α O This represents the additional stress coefficient at the top surface of the weak underlying layer below the midpoint of the bottom surface of the annular foundation. α R Width b The additional stress coefficient at the top surface of the weak underlying layer below the midpoint of the uniformly distributed strip load.

7. The method for analyzing the bearing capacity of the bottom surface of a ring foundation and a weak underlying layer according to claim 6, characterized in that, The α O The determination method is as follows: The difference in the additional stress coefficient at the top surface of the weak underlying layer below the midpoint of the two uniformly distributed circular loads on the bottom surface of the annular foundation is taken as the additional stress coefficient. α O .

8. The method for analyzing the bearing capacity of the bottom surface of a ring foundation and a weak underlying layer according to claim 6, characterized in that, The α R The determination method is as follows: Determine the width b The first additional stress generated by the hypothetical strip foundation at the top surface of the weak underlying layer below the midpoint of the hypothetical strip foundation, and the adjacent widths of the same... b The second additional stress generated at the top surface of the weak underlying layer below the midpoint of the imaginary strip foundation; By superimposing the first and second additional stresses using the corner point method, the following can be obtained: α R .

Images