A design method for a composite pile foundation of a biogas fermentation tank

Abstract

The present invention belongs to the technical field of building foundations and relates to a design method for a composite pile foundation for a biogas fermentation tank. The method includes: determining the tank diameter and the tank height; calculating the thickness of the bearing platform; determining the diameter of the bearing platform; dividing the bearing platform into several regions; determining the bearing platform area control coefficient for each region and at the same time determining the bearing platform effect coefficient; calculating the loads for each region; determining the characteristic value of the single-pile bearing capacity; determining the required number of piles according to the characteristic value of the single-pile bearing capacity, the bearing platform area control coefficient and the bearing platform effect coefficient for each region; obtaining the settlement amount and the settlement difference for each region through settlement calculation; adjusting the number of piles and arranging the piles. The present invention uses a method of zoning dynamic design to improve the pile-soil cooperation efficiency, and avoids damage to the tank structure by checking the settlement amount and dynamically adjusting the number of piles; combines the pile spacing to dynamically correct the bearing platform area control coefficient, and improves the theoretical completeness and engineering applicability of the composite pile foundation design.

Description

Technical Field

[0001] The present invention belongs to the technical field of building foundations, and more particularly, relates to a design method for a composite pile foundation for a biogas fermentation tank. Background Art

[0002] In recent years, the construction of large and medium-sized biogas projects in soft soil foundations has gradually increased. At present, the pile foundation design methods for biogas fermentation tanks in soft soil foundations have the following limitations:

[0003] (1) Insufficient load distribution and pile-soil synergy mechanism: Most of the existing composite pile foundation designs adopt a homogenization treatment, and do not conduct a zonal differential design according to the radial gradient distribution characteristics of the tank load, resulting in low pile-soil synergy bearing efficiency; for example, the conventional method regards the pile cap as a whole to calculate the number of piles and layout, ignoring the stress differences in each area, resulting in redundant pile numbers or insufficient local bearing capacity, increasing both the cost and affecting safety;

[0004] (2) Insufficient settlement control accuracy: Traditional designs rely on overall settlement calculations, but biogas fermentation tanks are extremely sensitive to differential settlements;

[0005] (3) Lack of coupling optimization of composite pile foundation parameters: The current specifications do not clarify the dynamic adjustment method of the pile cap area control coefficient for composite pile foundations in the scenario of biogas fermentation tanks. Existing technologies fix the value of the pile cap area control coefficient under the same pile cap, without considering the coupling effect of pile spacing and regional load differences, resulting in an imbalance in the pile-soil load sharing ratio, unable to fully utilize the bearing capacity of the soil between piles, causing redundant pile foundations or out-of-control settlements. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a design method for a composite pile foundation for a biogas fermentation tank, including:

[0007] According to the tank volume, set the ratio of the tank diameter to the tank height, and determine the tank diameter and the tank height;

[0008] Calculate the thickness of the pile cap that meets the punching bearing capacity;

[0009] Determine the diameter of the pile cap according to the tank diameter and the thickness of the pile cap;

[0010] Divide the pile cap into several regions according to the stiffness of the pile cap;

[0011] Determine the pile cap area control coefficient for each region according to the load bearing ratio of the piles and the load bearing ratio of the soil between piles in each region, and at the same time determine the pile cap effect coefficient;

[0012] Calculate the load borne by the composite pile foundation in each region according to the contact stress at the bottom of the pile cap in each region;

[0013] Set the pile length and pile diameter, and determine the characteristic value of the bearing capacity of a single pile;

[0014] Determine the required number of piles according to the characteristic value of the bearing capacity of a single pile, the area control coefficient and the pile cap effect coefficient of each area;

[0015] According to the loads of each area, conduct settlement calculations on the composite pile foundations of each area to obtain the settlement amounts and settlement differences of each area;

[0016] Adjust the number of piles according to the settlement amounts and settlement differences of each area, and arrange the piles.

[0017] Based on the above technical solutions, the present invention can be further improved as follows.

[0018] Furthermore, the load borne by the composite pile foundation within the area is the sum of the total weight of the metal tank and mechanical and electrical equipment within the area, the weight of the pile cap within the area, and the weight of the fermentation broth within the area of the pile cap.

[0019] Furthermore, the value range of the ratio of the set tank diameter to the tank height is 1:1 to 1:3.

[0020] Furthermore, let the tank diameter be , and the pile cap thickness be , and the diameter of the composite pile foundation pile cap be , then: .

[0021] Furthermore, divide the pile cap into several areas according to the stiffness of the pile cap, including a circular area with the center of the pile cap as the center and the distance between the stiffness change point of the pile cap and the center as the radius, and several ring areas outside the circular area.

[0022] Furthermore, divide the pile cap into the first area, the second area and the third area; the first area and the second area are ring areas outside the circular area with the center of the pile cap as the center and the distance between the stiffness change point of the pile cap and the center as the radius, this circular area is the third area, and the inner ring radius of the first area is the outer ring radius of the second area; the load borne by the composite pile foundation within the first area is the sum of the total weight of the metal tank and mechanical and electrical equipment within the area, the weight of the pile cap within the area, and the weight of the fermentation broth within the area; the load borne by the composite pile foundation within the second area is the sum of the weight of the fermentation broth within the area and the weight of the pile cap within the area; the load borne by the composite pile foundation within the third area is the sum of the weight of the fermentation broth within the area and the weight of the pile cap within the area.

[0023] Furthermore, the pile type is a friction pile; the pile tip penetrates into the soft soil layer to a set depth, and does not use a hard soil layer as the pile tip bearing layer.

[0024] Furthermore, the pile linear layout in the first area is arranged directly below the axis of the tank wall plate and is evenly distributed along the axis; the thickness of the bearing platform in the first area is greater than that in the third area, and the tops of the bearing platforms in the first, second, and third areas are on the same horizontal plane. The bottom surface of the bearing platform in the first area transitions to the bottom surface of the third area through the bottom surface of the second area. The bottom surfaces of the bearing platforms in the first area and the third area are horizontal planes, and the included angle between the bottom surface of the bearing platform in the second area and the horizontal plane is 45°.

[0025] Furthermore, according to the characteristic value of the bearing capacity of a single pile, the bearing platform area control coefficient and the bearing platform effect coefficient of each area, the required number of piles is determined, including: Let the characteristic value of the bearing capacity of a single pile be , the characteristic value of the bearing capacity of the foundation under the bearing platform be , the number of piles be , the total net area of the pile foundation bearing platform be , the standard value of the external load borne by the bearing platform within the area be , the weight of the bearing platform within the area be , the bearing platform effect coefficient be , and the bearing platform area control coefficient be ;

[0026] ;

[0027] Then the number of piles:

[0028] .

[0029] The beneficial effects of the present invention are:

[0030] (1) Zoning dynamic design improves the pile-soil cooperation efficiency: The bearing platform is divided into several areas, and the bearing platform area control coefficient and the load sharing ratio are respectively set to achieve precise matching of the load-pile soil response and reduce the foundation cost;

[0031] (2) Hierarchical settlement control ensures the safety of the tank body: By independently checking the settlement amount in different areas and dynamically adjusting the number of piles, it is ensured that the maximum settlement amount and the settlement difference meet the requirements of the "Code for Design of Foundation of Steel Storage Tanks", avoiding damage to the tank body structure;

[0032] (3) Parameter coupling optimization enhances the scientific nature of the design: Combining the pile spacing to dynamically correct the bearing platform area control coefficient, improving the theoretical completeness and engineering applicability of the composite pile foundation design. Description of the Drawings

[0033] Figure 1 is the schematic diagram of the principle of a composite pile foundation design method for a biogas fermentation tank of the present invention;

[0034] Figure 2 is the schematic diagram of the bearing platform plane zoning;

[0035] Figure 3 It is a schematic sectional view of a bearing platform.

[0036] Icons: S1 - First region; S2 - Second region; S3 - Third region. Specific implementation manners

[0037] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0038] As an embodiment, as shown in the attached Figure 1 figure, to solve the above technical problems, the present embodiment provides a design method for a composite pile foundation for a biogas fermentation tank, including:

[0039] According to the volume of the tank body, set the ratio of the diameter of the tank body to the height of the tank body, and determine the diameter and height of the tank body;

[0040] Calculate the thickness of the bearing platform that meets the punching bearing capacity;

[0041] Determine the diameter of the bearing platform according to the diameter of the tank body and the thickness of the bearing platform;

[0042] Divide the bearing platform into several regions according to the stiffness of the bearing platform;

[0043] Determine the area control coefficient of the bearing platform in each region according to the load-bearing ratio of the piles and the load-bearing ratio of the soil between the piles in each region, and at the same time determine the pile cap effect coefficient;

[0044] Calculate the loads borne by the composite pile foundations in each region according to the contact stresses at the bottom of the bearing platform in each region;

[0045] Set the pile length and pile diameter, and determine the characteristic value of the bearing capacity of a single pile;

[0046] Determine the required number of piles according to the characteristic value of the bearing capacity of a single pile, the area control coefficient of the bearing platform in each region and the pile cap effect coefficient;

[0047] Conduct settlement checks on the composite pile foundations in each region according to the loads in each region, and obtain the settlement amounts and settlement differences in each region;

[0048] Adjust the number of piles according to the settlement amounts and settlement differences in each region, and arrange the piles.

[0049] Optionally, the loads borne by the composite pile foundations in the region are the sum of the total weight of the metal tank body and the mechanical and electrical equipment in the region, the weight of the bearing platform in the region, and the weight of the fermentation liquid in the region of the bearing platform.

[0050] Optionally, the value range of the ratio of the set tank diameter to the tank height is 1:1 to 1:3.

[0051] The selection of the ratio of the tank diameter to the tank height should comprehensively consider the control of dissolved oxygen and the mixing speed of the fed-batch medium and the fermentation broth.

[0052] The present invention divides the bearing platform into several regions, respectively sets the bearing platform area control coefficient and the proportion of the load borne by the soil between piles, realizes the precise matching of the load-pile-soil response, and reduces the foundation cost; by independently checking the settlement amount in each region and dynamically adjusting the number of piles, it ensures that the maximum settlement difference meets the requirements of the "Code for Design of Steel Storage Tank Foundation", and avoids damage to the tank structure; combines the pile spacing to dynamically correct the bearing platform area control coefficient, and improves the theoretical completeness and engineering applicability of the composite pile foundation design.

[0053] Therefore, in actual biogas projects, it is necessary to reasonably select the ratio of the tank diameter to the tank height according to the specific fermentation process, microbial characteristics, and requirements for dissolved oxygen and mixing speed to achieve the best fermentation effect.

[0054] Optionally, let the tank diameter be , and the bearing platform thickness be , and the diameter of the composite pile foundation bearing platform be , then: .

[0055] Optionally, the bearing platform thickness is greater than or equal to 400 mm.

[0056] Optionally, the bearing platform is divided into several regions according to the stiffness of the bearing platform, including a circular region with the center of the bearing platform as the center and the distance between the stiffness change point of the bearing platform and the center as the radius, and several annular regions outside the circular region.

[0057] Optionally, the bearing platform is divided into a first region, a second region and a third region; the first region and the second region are annular regions outside the circular region with the center of the bearing platform as the center and the distance between the stiffness change point of the bearing platform and the center as the radius, the circular region is the third region, and the inner ring radius of the first region is the outer ring radius of the second region; the load borne by the composite pile foundation in the first region is the sum of the total weight of the metal tank and the mechanical and electrical equipment in this region, the weight of the bearing platform in this region, and the weight of the fermentation broth in this region; the load borne by the composite pile foundation in the second region is the sum of the weight of the fermentation broth in this region and the weight of the bearing platform in this region; the load borne by the composite pile foundation in the third region is the sum of the weight of the fermentation broth in this region and the weight of the bearing platform in this region.

[0058] The schematic diagram of the bearing platform plane zoning is shown in Appendix Figure 2As shown. The loads of the first region S1 and the second region S2 are approximately regarded as line loads, and the load of the third region S3 is a uniformly distributed load.

[0059] In the actual application process, let the bearing platform area control coefficient of the first region be , the bearing platform area control coefficient of the second region be , the bearing platform area control coefficient of the third region be , the bearing platform effect coefficient be , , , , in view of the fact that when the ratio of the center distance between piles to the pile diameter is greater than 6, the bearing platform effect will no longer increase with the increase of this ratio. According to the technical code for building pile foundations, at this time, the bearing platform effect coefficient is 0.5 - 0.8. In soft soil foundations, the bearing platform effect coefficient takes 0.8 times the lower value.

[0060] Optionally, the pile type is a friction pile; the pile tip penetrates into the soft soil layer to a set depth, and does not use a hard soil layer as the pile tip bearing layer.

[0061] In the actual application process, the pile tip penetrates into the soft soil layer to a set depth, and does not use a hard soil layer as the pile tip bearing layer, ensuring that the pile tip can penetrate into the soft soil layer when the composite pile is loaded.

[0062] Optionally, as shown in the schematic cross - section diagram of the bearing platform in Attachment Figure 3 , the pile lines in the first region are arranged directly below the axis of the tank wall plate and are evenly distributed along the axis; the thickness of the bearing platform in the first region is greater than that of the bearing platform in the third region, and the tops of the bearing platforms in the first region, the second region, and the third region are on the same horizontal plane. The bottom surface of the bearing platform in the first region transitions to the bottom surface of the third region through the bottom surface of the second region. The bottom surface of the bearing platform in the first region and the bottom surface of the bearing platform in the third region are horizontal planes, and the included angle between the bottom surface of the bearing platform in the second region and the horizontal plane is 45°.

[0063] Optionally, according to the characteristic value of the bearing capacity of a single pile, the bearing platform area control coefficients and the bearing platform effect coefficients of each region, determine the required number of piles, including: let the characteristic value of the bearing capacity of a single pile be , the characteristic value of the bearing capacity of the foundation under the bearing platform be , the number of piles be , the total net area of the pile foundation bearing platform be , the standard value of the external load borne by the bearing platform within the region be , the weight of the bearing platform within the region be , the bearing platform effect coefficient be , the bearing platform area control coefficient be ;

[0064] ;

[0065] Then the number of piles:

[0066] .

[0067] When performing settlement calculations on the composite pile foundations in each area according to the loads in each area, the settlement amount and the settlement difference in each area should meet the design requirements of the "Code for Design of Foundation of Steel Storage Tanks". Adjust the number of piles when the difference between the maximum and minimum settlement values does not meet the set threshold range.

[0068] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A design method for a composite pile foundation of a biogas fermentation tank, characterized in that Including: Set the ratio of the tank diameter to the tank height according to the tank volume, and determine the tank diameter and the tank height; Calculate the minimum thickness of the bearing platform that meets the punching bearing capacity; Determine the diameter of the bearing platform according to the tank diameter and the thickness of the bearing platform; Divide the bearing platform into several regions according to the stiffness of the bearing platform, including a circular region with the center of the bearing platform as the center and the distance between the stiffness change point of the bearing platform and the center as the radius, and several annular regions outside the circular region; divide the bearing platform into the first region, the second region and the third region; the first region and the second region are annular regions outside the circular region with the center of the bearing platform as the center and the distance between the stiffness change point of the bearing platform and the center as the radius, and this circular region is the third region, and the inner ring radius of the first region is the outer ring radius of the second region; the load borne by the composite pile foundation in the first region is the sum of the total weight of the metal tank and the mechanical and electrical equipment in this region, the weight of the bearing platform in this region, and the weight of the fermentation broth in this region; the load borne by the composite pile foundation in the second region is the sum of the weight of the fermentation broth in this region and the weight of the bearing platform in this region; the load borne by the composite pile foundation in the third region is the sum of the weight of the fermentation broth in this region and the weight of the bearing platform in this region; the pile lines in the first region are arranged directly below the axis of the tank wall plate and are evenly distributed along the axis; the thickness of the bearing platform in the first region is greater than the thickness of the bearing platforms in the second and third regions, and the tops of the bearing platforms in the first region, the second region and the third region are on the same horizontal plane, the bottom surface of the bearing platform in the first region transitions to the bottom surface of the third region through the bottom surface of the second region, the bottom surface of the bearing platform in the first region and the bottom surface of the bearing platform in the third region are horizontal planes, and the included angle between the bottom surface of the bearing platform in the second region and the horizontal plane is 45°; Determine the area control coefficient of the bearing platform in each region according to the load-bearing ratio of the piles and the load-bearing ratio of the soil between the piles in each region, and at the same time determine the bearing platform effect coefficient; Calculate the load borne by the composite pile foundation in each region according to the contact stress of the bottom surface of the bearing platform in each region; Set the pile length and the pile diameter, and determine the characteristic value of the single-pile bearing capacity; Determine the required number of piles according to the characteristic value of the single-pile bearing capacity, the area control coefficient of the bearing platform in each region and the bearing platform effect coefficient; Conduct settlement calculation on the composite pile foundation in each region according to the load in each region, and obtain the settlement amount and the settlement difference in each region; Adjust the number of piles according to the settlement amount and the settlement difference in each region, and arrange the piles.

2. The design method of a composite pile foundation for a biogas fermentation tank according to claim 1, characterized in that, The load borne by the composite pile foundation in the region is the sum of the total weight of the metal tank and the mechanical and electrical equipment in this region, the weight of the bearing platform in this region, and the weight of the fermentation broth in the bearing platform in this region.

3. The design method of a composite pile foundation for a biogas fermentation tank according to claim 1, characterized in that The value range of the ratio of the set tank diameter to the tank height is 1:1 to 1:

3.

4. The design method of a composite pile foundation for a biogas fermentation tank according to claim 1, characterized in that, Let the diameter of the tank body be , the thickness of the bearing platform be , and the diameter of the composite pile foundation bearing platform be , then: .

5. The design method of a composite pile foundation for a biogas fermentation tank according to claim 1, characterized in that The thickness of the bearing platform is greater than or equal to 400mm.

6. The design method of a composite pile foundation for a biogas fermentation tank according to claim 1, characterized in that, The pile type is a friction pile; the pile tip penetrates into the soft soil layer by a set depth, and does not use the hard soil layer as the pile tip bearing layer.

7. The design method of a composite pile foundation for a biogas fermentation tank according to claim 1, characterized in that Determine the required number of piles based on the characteristic value of the bearing capacity of a single pile, the pile cap area control coefficient and the pile cap effect coefficient for each area, including: Let the characteristic value of the bearing capacity of a single pile be , the characteristic value of the bearing capacity of the foundation under the pile cap be , the number of piles be , the total net area of the pile foundation cap be , the standard value of the external load on the pile cap within the area be , the weight of the pile cap within the area be , the pile cap effect coefficient be , the pile cap area control coefficient be ; ； Then the number of piles: 。

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