Composite pile foundation design method for biogas fermentation tank

Abstract

The invention belongs to the technical field of building foundations, and relates to a design method of a composite pile foundation for a biogas fermentation tank. The method comprises the following steps: determining the diameter and height of a tank body; calculating the thickness of the bearing platform; determining the diameter of the bearing platform; dividing the bearing platform into a plurality of areas; determining a bearing platform area control coefficient of each region, and determining a bearing platform effect coefficient; calculating the load of each region; determining a single pile bearing capacity characteristic value; according to the single-pile bearing capacity characteristic value and the bearing platform area control coefficient and the bearing platform effect coefficient of each area, the number of needed piles is determined; carrying out settlement checking calculation to obtain the settlement volume of each area and the settlement difference of each area; and adjusting the pile number and distributing the piles. The pile-soil cooperation efficiency is improved by adopting a partition dynamic design method, and the tank structure is prevented from being damaged by checking the settling volume and dynamically adjusting the number of piles; and the pile cap area control coefficient is dynamically corrected in combination with the pile distance, and the theoretical completeness and engineering applicability of composite pile foundation design are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of building foundations, and specifically 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: (1) Insufficient load distribution and pile-soil synergy mechanism: Most existing composite pile foundation designs adopt a homogenization treatment and do not conduct a zoned differential design according to the radial gradient distribution characteristics of the tank load, resulting in low pile-soil collaborative bearing efficiency; for example, the conventional method treats the pile cap as a whole to calculate the number of piles and their layout, ignoring the stress differences in each area, causing redundant pile numbers or insufficient local bearing capacity, which not only increases the cost but also affects safety; (2) Insufficient settlement control accuracy: Traditional designs rely on overall settlement calculations, but biogas fermentation tanks are extremely sensitive to differential settlements; (3) Lack of coupling optimization of composite pile foundation parameters: The current specifications do not clearly define 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 the pile spacing and the regional load difference, resulting in an imbalance in the load sharing ratio between the pile and the soil, being 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

[0003] To solve the above technical problems, the present invention provides a design method for a composite pile foundation for a biogas fermentation tank, including: According to the volume of the tank, set the ratio of the tank diameter to the tank height, and determine the tank diameter and the tank height; Calculate the thickness of the pile cap that meets the punching bearing capacity; Determine the diameter of the pile cap according to the tank diameter and the thickness of the pile cap; Divide the pile cap into several regions according to the stiffness of the pile cap; 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; 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; 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 pile cap area control coefficient, and the pile cap effect coefficient for each region; Conduct a settlement check 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 settlement difference of each area, and arrange the piles.

[0004] Based on the above technical solution, the present invention can also be improved as follows.

[0005] Further, the load borne by the composite pile foundation within the area is the sum of the combined weight of the metal tank and mechanical and electrical equipment within the area, the weight of the bearing platform within the area, and the weight of the fermentation broth within the area of the bearing platform.

[0006] Further, the value range of the ratio of the set tank diameter to the tank height is 1:1 to 1:3.

[0007] Further, let the tank diameter be , and the thickness of the bearing platform be , and the diameter of the composite pile foundation bearing platform be , then: .

[0008] Further, divide the bearing platform into several areas according to the stiffness of the bearing platform, including a circular area 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 areas outside the circular area.

[0009] Further, divide the bearing platform into the first area, the second area and the third area; the first area and the second area are annular areas outside the circular area 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 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 combined weight of the metal tank and mechanical and electrical equipment within the area, the weight of the bearing platform 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 bearing platform 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 bearing platform within the area.

[0010] Further, 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.

[0011] Further, the pile lines in the first area 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 area is greater than the thickness of the bearing platform in the third area, and the tops of the bearing platforms in the first area, the second area and the third area 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 surface of the bearing platform in the first area and the bottom surface of the bearing platform in 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°.

[0012] Further, according to the characteristic value of the bearing capacity of a single pile, the pile cap area control coefficient and the pile cap effect coefficient of each area, the required number of piles is determined, including: assuming the characteristic value of the bearing capacity of a single pile is , the characteristic value of the bearing capacity of the foundation under the pile cap is , the number of piles is , the total net area of the pile foundation cap is , the standard value of the external load on the pile cap within the area is , the weight of the pile cap within the area is , the pile cap effect coefficient is , the pile cap area control coefficient is ; ; Then the number of piles: .

[0013] The beneficial effects of the present invention are: (1) The zoned dynamic design improves the pile-soil cooperation efficiency: The pile cap is divided into several areas, and the pile cap area control coefficient and the load sharing ratio are set respectively to achieve the precise matching of the load-pile soil response and reduce the foundation cost; (2) The hierarchical settlement control ensures the safety of the tank: By independently checking the settlement amount in each area 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 for Steel Storage Tanks", avoiding damage to the tank structure; (3) The parameter coupling optimization enhances the scientificity of the design: Combining the pile spacing to dynamically correct the pile cap area control coefficient, improving the theoretical completeness and engineering applicability of the composite pile foundation design. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is the schematic diagram of the principle of a composite pile foundation design method for a biogas fermentation tank according to the present invention; Figure 2 is the schematic diagram of the plane zoning of the pile cap; Figure 3 is the schematic diagram of the cross-section of the pile cap.

[0014] Icon: S1 - First area; S2 - Second area; S3 - Third area. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] 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 in conjunction with the 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 shown in the drawings here can be arranged and designed in various different configurations.

[0016] As an embodiment, as shown in the appendixFigure 1 As shown in Figure 1 , to solve the above technical problems, this embodiment provides a design method for a composite pile foundation for a biogas fermentation tank, including: According to the volume of the tank body, set the ratio of the tank body diameter to the tank body height, and determine the tank body diameter and the tank body height; Calculate the thickness of the bearing platform that meets the punching bearing capacity; Determine the diameter of the bearing platform according to the tank body diameter and the thickness of the bearing platform; Divide the bearing platform into several regions according to the stiffness of the bearing platform; Determine the bearing platform area control coefficient of 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 at the bottom 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 bearing platform area control coefficient of each region, and the bearing platform effect coefficient; Carry out 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 carry out pile layout.

[0017] Optionally, the load borne by the composite pile foundation in the region is 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 broth in the region of the bearing platform.

[0018] Optionally, the value range of the set ratio of the tank body diameter to the tank body height is 1:1 to 1:3.

[0019] The selection of the ratio of the tank body diameter to the tank body height should comprehensively consider the control of dissolved oxygen and the mixing speed of the fed-batch medium and the fermentation broth.

[0020] The present invention divides the bearing platform into several regions, and respectively sets the bearing platform area control coefficient and the load-bearing ratio of the soil between the 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 Foundation of Steel Storage Tanks", and avoids damage to the tank body structure; combines the dynamic correction of the bearing platform area control coefficient with the pile spacing to improve the theoretical completeness and engineering applicability of the composite pile foundation design.

[0021] Therefore, in the actual biogas project, it is necessary to reasonably select the ratio of the tank body diameter to the tank body height according to the specific fermentation process, microbial characteristics, and the requirements for dissolved oxygen and mixing speed to achieve the best fermentation effect.

[0022] Optionally, 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: .

[0023] Optionally, the thickness of the bearing platform is greater than or equal to 400 mm.

[0024] Optionally, the bearing platform is divided into several regions according to its stiffness, 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.

[0025] 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 body and the electromechanical equipment in this region, the weight of the bearing platform in this region and the weight of the fermentation liquid in this region; the load borne by the composite pile foundation in the second region is the sum of the weight of the fermentation liquid 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 liquid in this region and the weight of the bearing platform in this region.

[0026] The schematic diagram of the bearing platform plane zoning is as shown in Appendix Figure 2 . 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 uniform load.

[0027] 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 , , , , considering that when the ratio of the center distance of the 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.

[0028] Optionally, the pile type is friction piles; 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.

[0029] In the actual application process, the pile tip penetrates into the soft soil layer to a set depth, and does not use the 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.

[0030] Optionally, as shown in the sectional schematic diagram of the pile cap Figure 3 The pile line 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 pile cap in the first area is greater than that in the third area, and the tops of the pile caps in the first, second, and third areas are on the same horizontal plane. The bottom surface of the pile cap in the first area transitions to the bottom surface of the third area through the bottom surface of the second area. The bottom surface of the pile cap in the first area and the bottom surface of the pile cap in the third area are horizontal planes, and the included angle between the bottom surface of the pile cap in the second area and the horizontal plane is 45°.

[0031] Optionally, according to the characteristic value of the bearing capacity of a single pile, the pile cap area control coefficient and the pile cap effect coefficient of each area, 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 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: .

[0032] When checking the settlement of the composite pile foundation 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 Steel Storage Tank Foundation". When the difference between the maximum and minimum settlement values does not meet the set threshold range, adjust the number of piles.

[0033] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, 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 composite pile foundation design method for a biogas fermentation tank, characterized in that: include: According to the volume of the tank, the ratio of the tank diameter to the tank height is set to determine the tank diameter and the tank height; Calculate the minimum thickness of the cap to meet the punching shear bearing capacity; Determine the diameter of the cap according to the diameter of the tank body and the thickness of the cap; The cap is divided into several areas according to its stiffness; Determine the cap area control coefficient of each area according to the proportion of pile loads in each area and the proportion of soil loads between piles, and determine the cap effect coefficient at the same time; According to the contact stress of the bottom of the cap in each area, calculate the load on the composite pile foundation in each area; Set the pile length and pile diameter to determine the characteristic value of the single pile bearing capacity; Determine the required number of piles based on the characteristic value of single pile bearing capacity, the cap area control coefficient and cap effect coefficient of each area; According to the load of each area, the settlement of the composite pile foundation in each area is checked and the settlement amount and settlement difference of each area are obtained; Adjust the number of piles and arrange the piles according to the settlement amount and settlement difference of each area.

2. A composite pile foundation design method for a biogas fermentation tank according to claim 1, characterized in that: The load borne by the composite pile foundation in the area is the sum of the total weight of the metal tank and electromechanical equipment in the area, the weight of the pedestal in the area, and the weight of the fermentation liquid on the pedestal in the area.

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

3.

4. A composite pile foundation design method for a biogas fermentation tank according to claim 1, characterized in that: Assume the tank diameter is The thickness of the base is The diameter of the composite pile foundation is ,but: .

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

6. The composite pile foundation design method for a biogas fermentation tank according to claim 1, characterized in that: The cap is divided into several areas according to the stiffness of the cap, including a circular area with the center of the cap as the center and the distance between the cap stiffness change point and the center as the radius, and several annular areas outside the circular area.

7. A composite pile foundation design method for a biogas fermentation tank according to claim 6, characterized in that: The cap is divided into a first area, a second area and a third area; the first area and the second area are annular areas outside a circular area with the center of the cap as the center and the distance from the center of the cap stiffness change point as the radius, the 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 in the first area is the sum of the total weight of the metal tank body and electromechanical equipment in the area, the weight of the cap in the area and the weight of the fermentation liquid in the area; the load borne by the composite pile foundation in the second area is the sum of the weight of the fermentation liquid in the area and the weight of the cap in the area; the load borne by the composite pile foundation in the third area is the sum of the weight of the fermentation liquid in the area and the weight of the cap in the area.

8. The composite pile foundation design method for a biogas fermentation tank according to claim 1, characterized in that: The pile type is a friction pile; the pile end is set to a depth deep in the soft soil layer, and the hard soil layer is not used as the bearing layer of the pile end.

9. A composite pile foundation design method for a biogas fermentation tank according to claim 7, characterized in that: The pile lines in the first area are arranged directly below the axis of the tank wall plate and are evenly distributed along the axis; the thickness of the pedestal in the first area is greater than that of the pedestals in the second and third areas, and the tops of the pedestals in the first, second and third areas are located in the same horizontal plane, the bottom surface of the pedestal in the first area transitions to the bottom surface of the third area through the bottom surface of the second area, the bottom surface of the pedestal in the first area and the bottom surface of the pedestal in the third area are horizontal planes, and the angle between the bottom surface of the pedestal in the second area and the horizontal plane is 45°.

10. The composite pile foundation design method for a biogas fermentation tank according to claim 1, characterized in that: According to the characteristic value of single pile bearing capacity, the control coefficient of the cap area in each area and the cap effect coefficient, the required number of piles is determined, including: assuming that the characteristic value of single pile bearing capacity is The bearing capacity characteristic value of the foundation at the bottom of the cap is , the number of piles is The total net area of ​​the pile foundation is The standard value of the external load on the bearing platform in the area is The weight of the bearing platform in the area is , the cap effect coefficient is , the control coefficient of the platform area is ; ； The number of piles: 。

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