Foundation structure for an LNG tank

Abstract

The utility model provides a kind of foundation structure of LNG storage tank, belong to foundation treatment engineering technical field. Including composite soil layer, from bottom to top are sequentially provided with bad soil layer, transition layer and replacement layer;Sinking pipe broken stone pile, vertically set in the bad soil layer;Bored pile, vertically set in the composite soil layer, its pile top is higher than the top surface of the replacement layer, pile body extends to the bottom of the bad soil layer;The utility model is applicable to the large-scale LNG storage tank formed by reclamation in coastal seaside, the foundation structure will replacement layer, transition layer, sinking pipe broken stone pile and bored pile organic integration, form multilayer collaborative composite foundation structure, satisfy the requirement standard of large-scale LNG storage tank for horizontal bearing capacity for sitting in seaside, guarantee the safety performance under the action of earthquake SSE, OBE and other unconventional working conditions.

Description

Technical Field

[0001] This utility model relates to the field of foundation treatment engineering technology, specifically to a foundation structure for an LNG storage tank. Background Technology

[0002] Given that LNG storage tanks are generally located in coastal areas, and some LNG storage areas are formed by land reclamation, the complex geological composition results in poor foundation stability and extremely low bearing capacity, making it unable to support the enormous weight of the LNG tanks and prone to settlement. In the case of saturated sandy soil or loose silty soil on land, under the cyclic shear stress caused by an earthquake, the pore water pressure rises sharply and the effective stress drops sharply, causing the soil to instantly lose strength and behave like a liquid (i.e., "liquefaction"). The liquefaction of the liquefied soil layer completely eliminates its bearing capacity and lateral restraint, leading to catastrophic consequences such as overall tilting, sliding, or even overturning of the LNG storage tank. LNG storage tanks have extremely high requirements for horizontal bearing capacity under the influence of earthquakes. Currently, most LNG storage tanks are constructed by increasing the bearing capacity through the addition of a large amount of steel reinforcement to the tank body and foundation piles, or by directly embedding the pile tops into the raft foundation. However, this method has disadvantages such as large concentrated internal forces at the pile tops, construction difficulties, and high costs.

[0003] Patent CN116220039A discloses a construction method for a thick plain concrete foundation layer of a ground-mounted LNG storage tank. By designing pouring zones and setting up column holes and PVC pipes, and constructing a pouring platform, it solves the operational difficulties in constructing the thick plain concrete foundation layer of a ground-mounted LNG storage tank. However, it does not specify solutions to the foundation bearing capacity problem under different geological conditions. Patent CN118793085A discloses a rigid pile composite foundation seismic isolation system and method for LNG storage tanks. By designing a rigid pile composite foundation seismic isolation system and utilizing layered seismic isolation and damping technologies, it solves the problems of difficult construction and high cost of existing LNG storage tank foundations in areas with high seismic intensity, achieving reduced pile foundation engineering costs and disaster mitigation effects. However, in land reclamation areas, there is still the problem of sand liquefaction damaging the rigid pile composite foundation structure.

[0004] It is evident that existing foundation structures are insufficient to meet the requirements of LNG storage tanks near the coast, cannot cope with the liquefaction of liquefied soil layers in coastal reclamation areas, and cannot solve the problems of poor foundation stability and extremely low bearing capacity caused by special geological conditions. Utility Model Content

[0005] In response to the problem that existing LNG storage tanks located in coastal areas are prone to insufficient foundation stability and reduced bearing capacity due to soil liquefaction under earthquakes, leading to tank tilting, this utility model discloses a novel LNG storage tank foundation structure. This structure effectively suppresses the earthquake-induced soil liquefaction effect, improves the overall stability and bearing capacity of the foundation, and thus ensures the safe operation of LNG storage tanks under complex geological conditions.

[0006] To achieve the above technical objectives, this utility model proposes a foundation structure for an LNG storage tank, comprising:

[0007] The composite soil layer consists of a poor soil layer, a transition layer, and a replacement layer, arranged from bottom to top.

[0008] The driven stone piles are vertically installed in the aforementioned unfavorable soil layer;

[0009] The cast-in-place piles are vertically installed in the composite soil layer, with the top of the pile higher than the top surface of the replacement layer and the pile body extending to the bottom of the undesirable soil layer.

[0010] This invention addresses the unique geological conditions of liquefiable soil layers in coastal locations by proposing a composite foundation structure with strong integrity and significant multi-layered synergistic effects. Based on the existing unfavorable soil layers in coastal locations, this invention organically integrates a replacement layer, a transition layer, driven gravel piles, and cast-in-place piles into a systematic foundation reinforcement system, with each layer functionally closely coupled: the replacement layer forms a high-strength rigid cushion layer, increasing the bearing capacity of the pile foundation; the transition layer acts as a bridging layer, allowing the cast-in-place piles to pass through the composite soil layer from a rigid to a flexible structure. The soil gradually softens, avoiding sudden changes in local bending moment of the cast-in-place piles. Furthermore, by installing driven crushed stone piles within the unfavorable soil layer, the loose sand layer and the upper clay layer are compacted, while vertical drainage channels are formed for rapid drainage and consolidation of the unfavorable soil layer. This facilitates the release of pore water from the unfavorable soil layer, eliminates the effects of liquefaction, reinforces the upper cohesive soil, solves the problem of consolidation settlement of dredged fill, and increases the horizontal bearing capacity of the foundation. Simultaneously, the cast-in-place piles, penetrating the entire composite soil layer and anchored within the unfavorable soil layer, provide stable bearing capacity, offering deep stability and strong end bearing capacity. This structured, multi-layered, synergistic foundation structure represents a systematic breakthrough in improving bearing capacity and eliminating liquefaction in the treatment of unfavorable soil layers in coastal locations.

[0011] Furthermore, the unfavorable soil layer includes a liquefiable soil layer and a weak soil layer located below the liquefiable soil layer, and a portion of the driven stone pile penetrates the liquefiable soil layer.

[0012] The driven crushed stone piles form vertical drainage channels in the liquefiable soil layer, allowing for rapid drainage and consolidation of the liquefied soil layer. This facilitates the release of pore water in the liquefied soil layer, eliminates the effects of liquefaction, reinforces the upper cohesive soil, solves the problem of consolidation settlement of the dredged fill, and increases the horizontal bearing capacity of the foundation.

[0013] Furthermore, the foundation structure of the LNG storage tank also includes a rock layer located below the poor soil layer, and the pile body of the cast-in-place pile penetrates the liquefied soil layer and the weak soil layer, with the pile bottom fixed to the rock layer.

[0014] The pile body of the cast-in-place pile needs to penetrate the liquefiable soil layer and the soft soil layer, and the pile bottom needs to be fixed to the rock layer, so as to avoid the cast-in-place pile from failing due to deformation of the liquefiable soil layer.

[0015] Furthermore, there are multiple driven stone piles, and these multiple driven stone piles are distributed in a rectangular array along the circumference of the cast-in-place pile.

[0016] By further optimizing the construction position of the cast-in-place piles, the surrounding driven stone piles provide better lateral restraint for the central cast-in-place piles. The central cast-in-place piles compensate for the deficiencies of the surrounding driven stone piles in terms of deep reinforcement and stiffness, and further achieve dual reinforcement of the loose, high-water-content soil layer formed by dredged filling, thus achieving the goal of simultaneously achieving compaction optimization and deep bearing capacity.

[0017] Furthermore, the replacement layer is a graded crushed stone mixed with cement slurry replacement layer.

[0018] Preferably, in the graded crushed stone mixed with cement slurry replacement layer of this utility model, the volume of cement slurry is 10% to 25% of the volume of graded crushed stone, and more preferably 15% to 25%.

[0019] Preferably, the graded crushed stone is composed of crushed stone with diameters of 0mm-10mm and 10mm-30mm in a ratio of (5-6):(4-5). Preferably, the crushed stone used is of grade III aggregate standard with a compressive strength ≥30KPa.

[0020] Preferably, the mass ratio of cement to water in the cement slurry is 1:(1.5 to 1.7).

[0021] Preferably, the cement used is silicate cement or ordinary silicate cement with a strength grade of 32.5 or 42.5.

[0022] Furthermore, the transition layer is a topsoil layer with a compaction coefficient of not less than 0.95. It should be noted that the transition layer of this invention is not limited to replacing topsoil; other materials with similar properties to topsoil can also be used as options in this invention.

[0023] Furthermore, the thickness of the replacement layer is 1.3m to 1.5m.

[0024] Furthermore, the thickness of the transition layer is 0.5m to 0.7m.

[0025] Furthermore, the diameter of the driven stone pile is 400mm to 600mm, and the distance between two adjacent driven stone piles is not less than three times the diameter of the driven stone pile. For example, when the diameter of the driven stone pile is 400mm, the pile spacing is 2.25m.

[0026] Furthermore, the diameter of the cast-in-place piles is 1000mm to 1500mm, and the distance between two adjacent cast-in-place piles is not less than three times the diameter of the cast-in-place piles. For example, when the diameter of the cast-in-place piles is 1500mm, the distance between the piles is 4.5m.

[0027] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0028] This utility model discloses a foundation structure for LNG storage tanks suitable for large LNG storage tanks built on reclaimed land near coastal areas. This foundation structure organically integrates a replacement layer, a transition layer, driven stone piles, and cast-in-place piles to form a multi-layered, synergistic composite foundation structure. The replacement layer forms a high-strength rigid cushion layer, increasing the bearing capacity of the pile foundation. The transition layer acts as a bridge, gradually softening the soil as the cast-in-place piles penetrate the composite soil layer, preventing sudden changes in local bending moments. Furthermore, by installing driven stone piles in unfavorable soil layers, the liquefaction effect of liquefiable soil layers during earthquakes is eliminated, increasing the horizontal bearing capacity of the foundation. This utility model's LNG storage tank foundation meets the horizontal bearing capacity requirements for large LNG storage tanks located near the coast, ensuring safety performance under unconventional operating conditions such as SSE and OBE during earthquakes. Attached Figure Description

[0029] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the drawings:

[0030] Figure 1 The diagram shows the foundation structure of the LNG storage tanks in Embodiments 1 and 2 of this utility model;

[0031] Figure 2 The diagram shows the arrangement of driven stone piles and cast-in-place piles in Embodiment 3 of this utility model.

[0032] The above figures include the following reference numerals:

[0033] 1-Unfavorable soil layer; 2-Transition layer; 3-Replacement layer; 4-Driving stone pile; 5-Cast-in pile. Detailed Implementation

[0034] To facilitate understanding of this utility model, a more comprehensive description of the present utility model will be provided below, along with preferred embodiments. However, it should be understood that these embodiments are merely for more detailed explanation and should not be construed as limiting the present utility model in any way, i.e., not limiting the scope of protection of the present utility model. Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which this utility model pertains.

[0035] Example 1

[0036] A foundation structure for an LNG storage tank, such as Figure 1 As shown, the structure includes a composite soil layer, driven stone piles 4, and cast-in-place piles 5. The composite soil layer consists of a poor soil layer 1, a transition layer 2, and a replacement layer 3 from bottom to top. The driven stone piles 4 are vertically installed in the poor soil layer 1. The cast-in-place piles 5 are vertically installed in the composite soil layer 1, with their tops higher than the top surface of the replacement layer 3, and the pile bodies extending to the bottom of the poor soil layer 1.

[0037] Unfavorable soil layer 1 is a sandy soil geological layer formed by hydraulic filling, including a liquefiable soil layer and a weak soil layer located below the liquefiable soil layer.

[0038] Optionally, the top of the driven stone pile 4 is level with the top surface of the unfavorable soil layer 1.

[0039] Optionally, a portion of the driven stone pile 4 penetrates the liquefiable soil layer, such that the length of the driven stone pile 4 is not less than the thickness of the liquefiable soil layer. For example, the length of the driven stone pile 4 is equal to the thickness of the liquefiable soil layer, or the length of the driven stone pile 4 is equal to the sum of the thickness of the liquefied soil layer and the thickness of a portion of the soft soil layer.

[0040] Optionally, the foundation structure includes a rock layer located below the unfavorable soil layer 1, and the pile shaft of the cast-in-place pile 5 penetrates the liquefiable soil layer and the soft soil layer, with the pile bottom fixed to the rock layer. For example, the pile length of the cast-in-place pile 5 is greater than the sum of the thicknesses of the replacement layer 3, the transition layer 2, and the liquefiable soil layer.

[0041] Optionally, the thickness of the replacement layer 3 is 1.3m to 1.5m, and the thickness of the transition layer 2 is 0.5m to 0.7m. For example, when the thickness of the replacement layer is 1.3m, the thickness of the transition layer 2 is 0.7m; or when the thickness of the replacement layer is 1.5m, the thickness of the transition layer 2 is 0.5m.

[0042] Example 2

[0043] A foundation structure for an LNG storage tank, such as Figure 1As shown, the structure includes a composite soil layer, driven stone piles 4, and cast-in-place piles 5. The composite soil layer consists of a poor soil layer 1, a transition layer 2, and a replacement layer 3 from bottom to top. The driven stone piles 4 are vertically installed in the poor soil layer 1. The cast-in-place piles 5 are vertically installed in the composite soil layer 1, with their tops higher than the top surface of the replacement layer 3, and the pile bodies extending to the bottom of the poor soil layer 1.

[0044] Unfavorable soil layer 1 is a sandy soil geological layer formed by hydraulic filling, including a liquefiable soil layer and a weak soil layer located below the liquefiable soil layer.

[0045] Optionally, the length of the driven stone pile 4 is equal to the thickness of the liquefiable soil layer. The length of the driven stone pile 4 is 13m, the pile spacing is 2.25m, and the pile diameter is 400mm.

[0046] Optionally, the length of the cast-in-place pile 5 is greater than the total thickness of the liquefiable soil layer, the transition layer and the replacement layer. The length of the cast-in-place pile 5 is 45m, the diameter is 1500mm and the spacing between piles is 4.5m.

[0047] As a preferred implementation method, such as Figure 1 As shown, the driven stone pile 4 is vertically installed in the poor soil layer 1, and the cast-in-place pile 5 is vertically installed in the composite soil layer to maximize the overall stability and bearing capacity of the foundation.

[0048] Optionally, the replacement layer 3 is a graded crushed stone mixed with cement grout, with a replacement depth of 1.5m. Further optionally, the graded crushed stone mixed with cement grout replacement layer is composed of graded crushed stone and cement grout in a volume ratio of 5:1. The graded crushed stone is composed of crushed stone with diameters of 0mm-10mm and 10mm-30mm in a part ratio of 6:4, meeting the third-grade aggregate standard, with a compressive strength ≥30KPa; the cement grout used is made of silicate cement and water, containing 78kg of cement and 130kg of water per cubic meter. The replacement layer structure of this utility model includes, but is not limited to, the composition given in this embodiment, and can also be composed of other graded crushed stone and cement grout that can meet the bearing capacity requirements.

[0049] Optionally, transition layer 2 is filled with topsoil, with a filling depth of 0.5m and a compaction coefficient of 0.97.

[0050] In this embodiment, the characteristic value of the bearing capacity of the transition layer 2 in the foundation structure of the LNG storage tank reaches 150 kPa, and the characteristic value of the bearing capacity of the replacement layer 3 reaches 220 kPa. The test pile results show that when the horizontal displacement of the top elevation of the cast-in-place pile 5 is 10 mm, the corresponding load value is 2476.7 kN, which is 85% higher than the load value of the LNG storage tank in the coastal area without foundation treatment. This greatly increases the horizontal bearing capacity of the cast-in-place pile 5 and the overall stability of the foundation, effectively eliminating the adverse effects of soft soil and liquefied soil layers on the foundation.

[0051] Example 3

[0052] Based on the foundation structure of the LNG storage tank in Example 1, this example further optimizes the arrangement of the driven pipe crushed stone piles, such as... Figure 2 As shown, in this embodiment, the driven stone piles 4 are arranged in a rectangular array along the circumference of the cast-in-place piles 5. The pile spacing of the driven stone piles 4 is 2.25m, the pile diameter is 400mm, and the pile length is 13m. The pile spacing of the cast-in-place piles 5 is 4.5m, the pile diameter is 1500mm, and the pile length is 45m.

[0053] The driven stone piles 4 are arranged in a rectangular array along the circumference of the cast-in-place piles 5, which provides better lateral restraint to the cast-in-place piles 5 in the center. The cast-in-place piles 5 in the center make up for the deficiencies of the driven stone piles 4 in the deep reinforcement and stiffness of the surrounding stones, and further achieve dual reinforcement of the loose and high water content soil layer formed by dredged filling, so as to achieve the purpose of compaction optimization and deep bearing capacity at the same time.

[0054] It should be noted that the above description is a further detailed explanation of the present invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the present invention to these descriptions; the dimensional data in this embodiment do not limit the technical solution, but merely illustrate one specific working condition. For those skilled in the art to which this invention pertains, several simple improvements and modifications can be made without departing from the concept of the present invention, and all such improvements and modifications should be considered to fall within the scope of protection of the present invention.

Claims

1. A foundation structure for an LNG storage tank, characterized by, include: The composite soil layer consists of a poor soil layer (1), a transition layer (2), and a replacement layer (3) arranged from bottom to top. The driven stone pile (4) is vertically installed in the unfavorable soil layer (1); The cast-in-place pile (5) is vertically installed in the composite soil layer, with its top being higher than the top surface of the replacement layer (3) and the pile body extending to the bottom of the unfavorable soil layer (1).

2. The foundation structure of an LNG storage tank according to claim 1, wherein The unfavorable soil layer (1) includes a liquefiable soil layer and a weak soil layer located below the liquefiable soil layer, and a portion of the driven stone pile (4) is installed through the liquefiable soil layer.

3. The foundation structure of an LNG storage tank according to claim 2, wherein The foundation structure also includes a rock layer located below the unfavorable soil layer (1), the pile body of the cast-in-place pile (5) penetrates the liquefied soil layer and the soft soil layer, and the pile bottom is fixed to the rock layer.

4. The foundation structure of an LNG storage tank according to claim 1, wherein The number of the driven stone piles (4) is multiple, and the multiple driven stone piles (4) are distributed in a rectangular array along the circumference of the cast-in-place piles (5).

5. The foundation structure of an LNG tank according to any one of claims 1 to 4, characterized in that, The replacement layer (3) is a graded crushed stone mixed with cement slurry replacement layer.

6. The foundation structure of the LNG storage tank according to any one of claims 1 to 4, characterized in that, The transition layer (2) is the mountain soil layer.

7. The foundation structure of an LNG storage tank according to claim 5, wherein The thickness of the replacement layer (3) is 1.3m to 1.5m.

8. The foundation structure of an LNG storage tank according to claim 6, wherein The thickness of the transition layer (2) is 0.5m to 0.7m.

9. The foundation structure of an LNG tank according to any one of claims 1 to 4, characterized in that, The diameter of the immersed tube crushed stone pile (4) is 400mm to 600mm, and the distance between two adjacent immersed tube crushed stone piles (4) is not less than 3 times the diameter of the immersed tube crushed stone pile (4).

10. The foundation structure of the LNG storage tank according to any one of claims 1 to 4, characterized in that, The diameter of the cast-in-place pile (5) is 1000mm to 1500mm, and the distance between two adjacent cast-in-place piles (5) is not less than 3 times the diameter of the cast-in-place pile (5).

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