Method for calculating equivalent compression modulus of structural clay

Abstract

This invention belongs to the field of geotechnical engineering technology, specifically relating to a method for calculating the equivalent compression modulus of structural clay. This method considers the structural strength of the soil. P d This method divides the calculated pressure range into a pre-structural strength segment and a post-structural strength segment. A weighted average method for calculating the compressibility modulus is constructed based on the proportion of pressure in both segments to determine the equivalent compressibility modulus. Taking into account the influence of soil structural strength, this method offers reliable accuracy and accurately reflects the actual compressibility characteristics of structural clay when the pressure range exceeds structural strength. It can be directly substituted into settlement calculation formulas to complete foundation settlement calculations. This method is applicable to settlement analysis and geotechnical engineering design for various types of structural clay foundations, possessing both engineering practicality and theoretical reference value.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, specifically relating to a method for calculating the equivalent compression modulus of structural clay, applicable to building foundation settlement calculation and engineering design. Background Technology

[0002] In engineering construction, a type of clay with special engineering properties is often found deep underground. Influenced by sedimentary environment and geological changes, it has physical properties such as high void ratio and high water content, but its mechanical properties such as consolidation and shear are relatively good, which is very different from conventional clay, and it has significant natural structural strength. P d This is manifested in consolidation compression. e ~ p The relationship curve exhibits typical hyperbolic characteristics, see appendix. Figure 1 . Considered as pressure applied to the soil P 2 (Self-weight pressure) P 1+ Additional pressure P 0) Below its structural strength P d When the soil's natural structure remains intact, its compression deformation is small, corresponding to a relatively large compression modulus; when the pressure... P 2 Exceeding structural strength P d Subsequently, the natural structure of the soil is destroyed, the compressive deformation suddenly increases, and the corresponding compression modulus decreases significantly. In geotechnical engineering design, when calculating the settlement of structural clay foundations, the pressure range used for calculating the compression modulus (the soil's own weight pressure) is crucial. P 1 to self-weight pressure P 1+ Additional pressure P 0) Structural strength P d At that time, existing calculation methods did not take structural strength into account. P d The impact of this has obvious technical defects: firstly, due to the soil's structural strength... P d The compressibility trend changed abruptly before and after, resulting in different patterns of change in the compression modulus with pressure. Directly using a uniform compression modulus value cannot represent the compressibility characteristics of the soil within this pressure range. Secondly, the compression modulus determined by this method has a large error, which in turn affects the accuracy of settlement calculation and makes it difficult to guide actual engineering.

[0003] Therefore, there is an urgent need for a method to calculate the compression modulus of structural clay that fully considers the influence of structural strength Pd, is intuitive to identify, easy to calculate, and has reliable results, in order to overcome the shortcomings of existing technologies. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for calculating the equivalent compression modulus of structural clay, which can be achieved through consolidation compression. e ~ p The relationship curve enables intuitive and accurate identification of soil structural strength. Using structural strength as the dividing point, the compression modulus is first determined according to the two pressure segments before and after, and then the equivalent compression modulus is obtained by the weighted harmonic average method formula. Then, it is substituted into the conventional settlement calculation formula, which solves the problems of large errors and unreasonableness of traditional methods.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for calculating the equivalent compression modulus of structural clay, the method comprising the following steps: Step 1: Conduct indoor consolidation compression tests on structural clay samples to obtain the porosity and consolidation pressure of the samples. e ~ p The structural strength of the structured clay is determined based on the inflection point of the relationship curve. P d ; Step 2: Determine the calculation pressure zone for the structural clay foundation: Calculate the self-weight pressure of the clay. P Starting from 1; calculate the self-weight pressure. P 1. Additional stress acting on clay P sum of 0 P The endpoint is 2, and the structural strength of the pressure section is satisfied. P d ,Right now P 1 < P d < P 2; Step 3: Assign the calculated pressure section according to structural strength. P d The structure is divided into a pre-strength section and a post-strength section. The pressure difference between the two pressure sections is calculated separately, and then the consolidation compression is considered. e ~ p The relationship curves are used to determine the compressive modulus corresponding to the first segment of structural strength using the conventional formula for calculating the compressive modulus. E s1 The compressive modulus corresponding to the latter part of the structural strength E s2 ; Step 4: Based on the principle of strain superposition, calculate the structural strength of the structural clay spanning the structure using the weighted harmonic average method according to the length ratio of the two pressure sections. P d Equivalent compressive modulus ; Step 5: Calculate the equivalent compressibility modulus. By directly substituting into the geotechnical engineering foundation settlement calculation formula, the settlement calculation of the structural clay foundation is completed.

[0006] Furthermore, the equivalent compressive modulus mentioned in step 4 The direct calculation expression is:

[0007] in P 1 represents the pressure due to its own weight. P d For structural strength, P 2 represents the sum of its own weight pressure and the additional pressure. E s1 The compressive modulus of the initial structural strength component. E s2 This represents the compressive modulus of the later stage of structural strength.

[0008] Furthermore, the structural strength is determined by the obvious inflection point of the consolidation compression e~p relationship curve obtained from the consolidation test, and its magnitude is automatically determined by the system.

[0009] Furthermore, in step 3, the first section of structural strength is the pressure range from self-weight pressure P1 to structural strength Pd, and the second section of structural strength is the pressure range from structural strength Pd to P2.

[0010] Furthermore, the foundation settlement calculation formula mentioned in step 5 is the layered summation method settlement calculation formula.

[0011] Compared with the prior art, the present invention has the following beneficial effects: This invention abandons the traditional semi-logarithmic coordinate method for identifying structural strength, and instead uses a Cartesian coordinate system for plotting. e ~ p Consolidation compression curves are used, and the structural strength of the soil is determined by accurately identifying the inflection points of the curves. P d， This eliminates the reliance on manual experience in interpreting drawings when determining structural strength, thus removing subjective errors and making structural strength identification more intuitive, objective, and accurate, providing a reliable foundation for the subsequent accurate division of pressure zones.

[0012] By calculating the pressure section in terms of structural strength P d Using this as the dividing point, the structure is divided into a pre-strength section and a post-strength section, and the compressive modulus of the two sections is calculated separately. E s1 and E s2It fully considers the physical nature of the abrupt change in compressibility of structural clay before and after structural strength. That is, before structural strength, the soil maintains its complete structure and has a high compression modulus, while after structural strength, the soil structure is destroyed and the compression modulus decreases. This avoids the irrationality of using a uniform compression modulus value to represent the compression characteristics of the entire pressure range in traditional methods, and makes the determination of the modulus more in line with the actual deformation law of the soil.

[0013] Based on the principle of strain superposition and deformation compatibility conditions, the length ratio of the two pressure sections is used as the weight, and a weighted harmonic mean method is employed to construct a formula for calculating the equivalent compression modulus. This method comprehensively considers the different compression characteristics of the two sections before and after the structural strength is crossed. The weighted harmonic mean form can reasonably reflect the physical relationship between the total strain and the sum of the strains in each section. Compared with the traditional single modulus method or the simple arithmetic mean method, the calculated equivalent compression modulus has higher accuracy and clearer physical meaning, and can truly reflect the comprehensive compression characteristics of the soil within the pressure section. Attached Figure Description

[0014] Figure 1 The relationship between e~p and structural strength of the consolidated compression of structural clay in this invention. P d Identification diagram. Detailed Implementation

[0015] Please see Figure 1 The porosity in the figure e The vertical axis represents the consolidation pressure. P With (kPa) as the abscissa, the curve exhibits typical hyperbolic characteristics, and the pressure value corresponding to the inflection point is the structural strength determined by the consolidation compression test. P d The left side of the inflection point represents the initial stage of structural strength, while the right side represents the later stage. The self-weight pressure is... P 1 (kPa), the soil pressure is P 2 (kPa).

[0016] One specific embodiment of the present invention is illustrated using the example of structural clay in the foundation of a building site.

[0017] First, samples of the structural clay were taken and subjected to indoor consolidation compression tests. Based on the test data, the void ratio was determined. e The vertical axis represents the consolidation pressure. p Establish a rectangular coordinate system for the horizontal axis and plot the consolidation and compression. e ~ p Relationship curve. For example... Figure 1 As shown, the curve exhibits typical hyperbolic characteristics with a clear inflection point. The system is used to identify the inflection point of this relationship curve to determine the structural strength of the structured clay. P d The pressure is 800 kPa.

[0018] Based on engineering geological survey data, the self-weight pressure of this structural clay was calculated. P 1 is 600 kPa; calculate the additional pressure acting on the clay based on the building load. P 0 is 500 kPa, and then the sum of the self-weight pressure and the additional pressure is calculated. P 2 is 1100 kPa. After comparison, the calculated pressure range meets the requirements. P 1 < P d < P 2. That is, the pressure zone crosses the structural strength of the soil, and the method of this invention is applicable to calculate the equivalent compression modulus.

[0019] Structural strength P d Using this as a dividing point, the calculated pressure section is divided into a pre-structural strength section and a post-structural strength section. The pre-structural strength section is the self-weight pressure. P 1 to structural strength P d The pressure range is 600 kPa to 800 kPa; the latter part of the structural strength is the structural strength. P d To the soil bearing pressure P 2. The pressure range is 800 kPa to 1100 kPa. Based on consolidation compression... e ~ p The relationship curve is used to determine the compression modulus corresponding to the two pressure sections using conventional compression modulus calculation methods, thus obtaining the compression modulus of the first section for structural strength. E s1 The compressive modulus of the structural strength section is 20.2 MPa. E s2 It is 16.5 MPa.

[0020] Based on the principle of strain superposition and deformation compatibility conditions, the weighted harmonic average method is used to calculate the strength of the spanning structure. P d The equivalent compressive modulus. The specific calculation formula is:

[0021] This yields the equivalent compressive modulus of the structural clay across the structural strength. It is 17.81 MPa.

[0022] The calculated equivalent compression modulus was directly substituted into the settlement calculation using the conventional layered summation method in geotechnical engineering to complete the settlement calculation for this structural clay foundation.

[0023] In this embodiment, the calculated pressure zone spans the structural strength determined by the consolidation compression curve. Pd The equivalent compression modulus obtained using the method of this invention considers both the high-modulus compression characteristics of the soil structure in the early stages of structural strength and the low-modulus compression characteristics in the later stages of structural strength. A weighted harmonic average is used to calculate the equivalent compression modulus. Compared to conventional calculation methods, the results more closely match the actual compression deformation characteristics of the soil, resulting in more accurate results. This invention supplements and improves the method for calculating the compression modulus of structural clay.

Claims

1. A method for calculating the equivalent compression modulus of structural clay, characterized in that, The method includes the following steps: Step 1: Conduct indoor consolidation compression tests on structural clay samples to obtain the porosity and consolidation pressure of the samples. e ~ p The system determines the structural strength of the structured clay based on the inflection point of the relationship curve. P d ; Step 2: Determine the calculation pressure zone for the structural clay foundation: Calculate the self-weight pressure of the clay. P Starting from 1; calculate the self-weight pressure. P 1. Additional stress acting on clay P sum of 0 P The endpoint is 2, and the structural strength of the pressure section is satisfied. P d ,Right now P 1 < P d < P 2; Step 3: Assign the calculated pressure section according to structural strength. P d The structure is divided into a pre-strength section and a post-strength section. The pressure difference between the two pressure sections is calculated separately, and then the consolidation compression is considered. e ~ p The relationship curves are used to determine the compressive modulus corresponding to the first segment of structural strength using the conventional formula for calculating the compressive modulus. E s1 The compressive modulus corresponding to the latter part of the structural strength E s2 ; Step 4: Based on the principle of strain superposition, calculate the structural strength of the structural clay spanning the structure using the weighted harmonic average method according to the length ratio of the two pressure sections. P d Equivalent compressive modulus ; Step 5: Calculate the equivalent compressibility modulus. By directly substituting into the geotechnical engineering foundation settlement calculation formula, the settlement calculation of the structural clay foundation is completed.

2. The method for calculating the equivalent compression modulus of structural clay according to claim 1, characterized in that, The equivalent compressive modulus mentioned in step 4 The direct calculation expression is: in P 1 represents the pressure due to its own weight. P d For structural strength, P 2 represents the sum of its own weight pressure and the additional pressure. E s1 The compressive modulus of the initial structural strength component. E s2 This represents the compressive modulus of the later stage of structural strength.

3. The method for calculating the equivalent compression modulus of structural clay according to claim 1, characterized in that, The structural strength is determined by the obvious inflection point of the consolidation compression e~p relationship curve obtained from the consolidation test, and its magnitude is automatically determined by the system.

4. The method for calculating the equivalent compression modulus of structural clay according to claim 1, characterized in that, The structural strength in step 3 is initially determined by its own weight. P 1 to structural strength P d The pressure range, the latter part of the structural strength is the structural strength. P d to P 2. Pressure range.

5. The method for calculating the equivalent compression modulus of structural clay according to claim 1, characterized in that, The foundation settlement calculation formula mentioned in step 5 is the layered summation method settlement calculation formula.

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